@article{ author = {pouraminian, maji}, title = {Concrete Open Arch Bridge Optimization}, abstract ={Abstract: Arch bridges are generally considered widely as esthetically pleasing bridges and its different variations can be found from both historical and modern times all over the word. Arch bridges can be divided into several different types by different definition. One possibility to divide them is through the spandrel. Spandrel can be open or closed. When it is open, there are usually columns to transmit the loads from the deck to the arch. The purpose of this study is to determine the optimum design of arch longitudinal no prismatic single-cell section. In this study, Cetina Bridge, which is a long span open reinforced concrete arch bridge spanning Cetina river canyon near the town of Trilj. The arch is of span 140m with a rise of 21.5 m, giving rise-to-span ratio of 1/6.5. The FE model of the Cetina open spandrel arch bridge was constructed using the Ansys. The main span and columns was simulated with Beam4, and element solid45 was used for reinforced concrete non prismatic single cell arch. For definition of arch geometry in longitudinal sections, parabolic conic functions are employed. In this present work the optimum design is carried out by taking total material volume of substructure of bridge as objective function. Substructure includes of column and reinforced concrete arch. Height of skewback abutment, Height of crown of arch, back and soffit radii of arch and position of crown respect to global axes are considered as design variables. The distance between the columns is assumed constant and equal to 21.6 m in optimization process. Also the cross sections of column are not taken as design variables. Instead of this, cross section of piers is selected proportionally with these of application project. During problem formulation most of practical design variables and constraints are considered. Three type of design constraints were taken into account: stress constraints of arch, transversal displacement constraints of arch crown and geometric constraint. Initially, a program is developed in MATLAB in order to generate coordinate of nodes, then is taken finite element software ANSYS for modelling the geometry of an arch dam. Finally, the optimization technique is performed by Simultaneous Perturbation Stochastic Approximation (SPSA) algorithm. Shape optimization for each of the arch web thickness to be examined (i.e. t_w=0.3-0.5m ). The following, some of important conclusions are drawn from the present work: It is concluded that SPSA can be effectively used in the shape optimization of the bridges. The total reinforced concrete volume obtained in this study is 23% less than the application project. For each t_w, the optimum arch geometry is obtained, when the volume of the arches and columns is minimized. Minimum volume of substructure achieved for t_w=0.35m with 1131 m3 . Keywords: long span; Open Arch Bridge; SPSA algorithm; Finite Element Analysis; substructure; shape optimization;}, Keywords = {long span,Open Arch Bridge,SPSA gradient based algorithm,substructure,shape optimization}, volume = {15}, Number = {1}, pages = {1-9}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11597-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11597-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Mortezaei, Alirez}, title = {Behavior of steel unbonded brace in seismic strengthening of reinforced concrete buildings}, abstract ={One of the strengthening methods in reinforced concrete frame buildings is improving seismic behavior of such structures by means of steel bracing. When influenced by compressive stresses, traditional steel braces would buckle and are free of any ductility. As a result, efforts in order to restrain buckling problem for steel braces has led to creation of steel unbonded brace. In these braces, Eulerian buckling of central steel core is controlled by placing in a steel tube full of mortar. In this paper, RC buildings of 6, 12 and 18 stories are first designed based on standard 2800 and then controlled based on the rehabilitation regulation and the third edition of standard 2800. After analyzing and in order to improve seismic behavior, these buildings are strengthened by the use of common braces and steel unbonded braces and the columns of braced frames are also reinforced by concrete jacket. Totally, 42 models were analyzed by nonlinear static analysis (pushover analysis). The results indicate that structures with traditional braces have weakness in high level of drifts due to buckling of compressive braces and the energy absorption in 12 and 18 stories structures is even lower than non-strengthened structures. Nevertheless, this defect is removed by applying unbounded braces because of somehow identical behavior in extension and pressure as well as utilizing total capacity of these kinds of brace. Also, in comparison with structures with traditional braces and non-strengthened structures, a high level of energy absorption will be obtained. One of the strengthening methods in reinforced concrete frame buildings is improving seismic behavior of such structures by means of steel bracing. When influenced by compressive stresses, traditional steel braces would buckle and are free of any ductility. As a result, efforts in order to restrain buckling problem for steel braces has led to creation of steel unbonded brace. In these braces, Eulerian buckling of central steel core is controlled by placing in a steel tube full of mortar. In this paper, RC buildings of 6, 12 and 18 stories are first designed based on standard 2800 and then controlled based on the rehabilitation regulation and the third edition of standard 2800. After analyzing and in order to improve seismic behavior, these buildings are strengthened by the use of common braces and steel unbonded braces and the columns of braced frames are also reinforced by concrete jacket. Totally, 42 models were analyzed by nonlinear static analysis (pushover analysis). The results indicate that structures with traditional braces have weakness in high level of drifts due to buckling of compressive braces and the energy absorption in 12 and 18 stories structures is even lower than non-strengthened structures. Nevertheless, this defect is removed by applying unbounded braces because of somehow identical behavior in extension and pressure as well as utilizing total capacity of these kinds of brace. Also, in comparison with structures with traditional braces and non-strengthened structures, a high level of energy absorption will be obtained.}, Keywords = {Unbonded bracing,buckling-restrained bracing,pushover analysis,Seismic behavior,energy absorption}, volume = {15}, Number = {1}, pages = {9-23}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2748-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2748-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {rashidinia, shaghayegh and Ahmadi, Mohammdtaghi}, title = {Optimum patterns for arch dam shape design in highly seismic zones}, abstract ={One of the most important issues in arch dam design, is optimum shape design of the dam body in such a way that both safety and economical constraints could be satisfied. The aim of this research is the introduction of some patterns for optimum arch dam shape in seismic zones and the identification of the optimum shape trends in proportion to physical and geometrical parameters of each specific site. Method of research includes parametric and statistical calculations on several arch dam sites samples. Thus optimization procedures are performed on dams with different heights, canyon widths, canyon shape types (V-shape or U-shape), and foundation moduli of deformation. Studying the resulting optimized arch dams shapes, certain trends of design variables is deduced in order to achieve optimum shape of the dam body when site specification changes. These trends are showed in graph forms. Resulting rules can be used as arch dam design guidline. One of the most important results of this study is the increasing trend in the thickness design variables in the central cantilever and abutments with the increase of the foundation modulus of elasticity. These rules can be used as guidelines for dam shape design. One of the most important issues in arch dam design, is optimum shape design of the dam body in such a way that both safety and economical constraints could be satisfied. The aim of this research is the introduction of some patterns for optimum arch dam shape in seismic zones and the identification of the optimum shape trends in proportion to physical and geometrical parameters of each specific site. Method of research includes parametric and statistical calculations on several arch dam sites samples. Thus optimization procedures are performed on dams with different heights, canyon widths, canyon shape types (V-shape or U-shape), and foundation moduli of deformation. Studying the resulting optimized arch dams shapes, certain trends of design variables is deduced in order to achieve optimum shape of the dam body when site specification changes. These trends are showed in graph forms. Resulting rules can be used as arch dam design guidline. One of the most important results of this study is the increasing trend in the thickness design variables in the central cantilever and abutments with the increase of the foundation modulus of elasticity. These rules can be used as guidelines for dam shape design. One of the most important issues in arch dam design, is optimum shape design of the dam body in such a way that both safety and economical constraints could be satisfied. The aim of this research is the introduction of some patterns for optimum arch dam shape in seismic zones and the identification of the optimum shape trends in proportion to physical and geometrical parameters of each specific site.}, Keywords = {concrete arch dam,optimum geometrical shape,Optimization,dam design}, volume = {15}, Number = {1}, pages = {23-35}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10857-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10857-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {RezaeiBalouchi, Moein and SalehJalali, Rez}, title = {Pounding response of adjacent buildings with non-equal height under near-fault strong ground motion}, abstract ={In this paper a simple model of one and two-storey adjacent buildings excited by the horizontal and vertical components of fault-normal pulse and fault-parallel displacement with different magnitudes and time lags has been considered. In the considered model each storey consist of a rigid beam connected to two axially rigid mass-less columns by nonlinear rotational springs and linear rotational dashpots. For determination of the pounding force the non-linear viscoelastic model has been chosen. In this model, a non-linear spring following the Hertz law of contact is applied together with an additional non-linear damper, which is activated during the approach period of collision in order to simulate the process of energy loss taking place mainly during that period. The ground motion is described by fault-normal pulse and fault-parallel permanent displacement, and their amplitudes and duration are selected consistent with the variables that describe near-fault motions. An important physical characteristic of the selected pulse and displacement is large initial velocity associated with onset of these motions and it is proportional to the stress drop on the fault. It is assumed that the buildings are near the fault and that the longitudinal axis of the buildings (x-axis) coincides with the radial direction (r-axis) of the propagation of waves from the earthquake source so that the absolute displacements of the bases of columns because of the wave passage are different. It is further assumed that the ground motion can be described approximately by linear-wave motion. It is assumed that the excitations at all bases have the same amplitude but differ in terms of phase. The phase difference (or time delay) between the input ground motions depends on the length of the buildings and the horizontal phase velocity of the incident waves. The system of equations of motion has been solved by the fourth-order Runge-Kutta method because of its self-starting feature and the long-range stability. For the considered models the results indicate: (1) for nonlinear behavior of material the impact force tends to increase of maximum relative displacement and permanent deformation specially in the second storey (2) the maximum impact force and the minimum distance required to avoid pounding of adjacent buildings under fault-normal pulse are many times larger than those induced by fault-parallel displacement (3) material nonlinearity reduces the maximum impact force and the minimum distance required to avoid pounding significantly, respect to the linear case. Also in nonlinear case the maximum impact force occurs at d>0, while for linear case it happens at d=0 (4) the time delay in ground motion can increase 1.5 to 2 times the maximum impact force and the minimum distance required to avoid collision. The horizontal component of the ground motion is predominant in this magnification and the effects of the vertical and rocking components of ground motion are negligible.}, Keywords = {Pounding,near-fault ground motion,forward directivity,fling-step,adjacent buildings}, volume = {15}, Number = {1}, pages = {35-46}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11262-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11262-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Shariatmadari, Nader and AsadiSeyfar, Nasser and Saeidijam, Saeid and Heshmati, Ali Akbar}, title = {Remediation of BTEX-contaminated groundwaters by Nano scale zero-valent Iron based PRBs}, abstract ={Benzene, toluene, ethylbenzene and xylenes, commonly referred to as BTEX, are critical monoaromatic environmental contaminants around the World, of which the major aromatic contaminants in gasoline pose serious environmental health problems. Leaking tanks or ruptured pipelines pollute soil and groundwater with these compounds. Because of their polarity and very soluble characteristics, these compounds will be able to enter the soil and groundwater systems and cause serious contamination problems and threats to the public safety and environment. One of the most promising ground water remediation technologies is the use of permeable reactive barriers (PRBs) packed with reactive material to intercept and decontaminate plumes in the subsurface. The concept of PRBs is rather simple. Reactive material is placed in the subsurface to intercept a plume of contaminated groundwater which must move through it as it flows, typically under its natural gradient. As the contaminant moves through the Reactive material, reactions occur that alter it to less harmful or immobile species. The PRB is not a barrier to the groundwater, but it is a barrier to the contaminant. The key advantage of a reactive barrier is the passive nature of the treatment. That is, for the most part, its operation does not depend on any external labor or energy inputs. Once installed, the barrier takes advantage of the in situ groundwater flow to bring the pollutants in contact with the reactive material. The reactive material used in the barrier may vary depending on the type of contaminants being treated. The most common reactive agent used to date has been granular iron. For contaminants of unknown treatability or media of unknown reactivity, addressing these issues will involve laboratory studies using both batch and column techniques. As for any remedial technology, it is imperative to fully understand the factors that can result in either effective implementation and successful remediation or failure to achieve the remedial design objectives. Iron nanoparticles are increasingly being applied in soil and grounwater remediation and hazardous waste treatment. Nearly two decades after iron nanoparticle was first proposed, the iron nanoparticle technology is at a critical point of its development process. Extensive laboratory studies have verified that nanoscale iron particles are effective for the treatment of a wide range of common groundwater pollutants such as chlorinated organic solvents, organochlorine pesticides, polychlorinated biphenyls (PCBs), organic dyes, and various inorganic compounds. Numerous field trials have also demonstrated the favorable prospective for in situ remediation. Nonetheless, there are still substantial knowledge gaps on many fundamental scientific issues. In this Experimental study, A series of laboratory experiments in various temperatures and contaminant concentrations were conducted on Nano sized zero-valet iron (nZVI) to determine its removal efficiency as PRB reactive materials against BTEX compounds in saturated Kaolinite clays, And the initial Concentration of BTEX is reduced to 60%. Obtained results may provide required data in groundwater remediation PRB systems design.}, Keywords = {BTEX,PRB,nano zero-valent Iron,permeable reactive barriers,ground water remediation}, volume = {15}, Number = {1}, pages = {47-57}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-8658-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-8658-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Investigation of Web sidesway buckling phenomenon in Steel Girders}, abstract ={In previous experiments, practice and in some condition of loading, geometry and support configurations, a type of instability has been observed in which tension flange moves laterally which it has been addressed in design codes as “web sidesway buckling”. Web sidesway buckling is a case of instability that it was observed in beam with restrained top flange and no constraint for bottom flange. Primary studies and experiments show that web sidesway buckling is due to both local instability in the web just under loaded zone and global instability of tension flange along length of the girder. In the present paper, a concise study has been carried out on behavior and the mechanism of this instability occurrence in web sidesway and how to evaluate loading capacity of the girders in the light of experiments, then a simple model which is a modification on the existing model has been proposed. Experimental work has been conducted to investigate the effect of tension flange on the load capacity of beams. The specimen's dimensions were adjusted in order to show web sidesway buckling. In addition, the supports configuration was made compatible with this instability. The objectives of the experiment were to obtain; mechanism of instability initiation, deformation pattern, effect of tension flange width and nonlinear deformations underneath the loading point. A closer view in load-displacement behavior of test specimens shows at first, loading accompanies lateral displacement due to imperfection and then rate of displacement reduces. After reaching to maximum load, girder has still capacity for load carrying but with excessive lateral displacement in tension flange. The results of experiments also show that web sidesway buckling generally accompanied by local buckling or crippling of the web under loaded zone. Deformation initiates with lateral movement of tension flange. Then local buckling and yielding occur, and finally, web sidesway buckling develops along the beam length. From this time onwards, load capacity is approximately constant. Furthermore, it can be seen that the rate of lateral displacement is directly dependent on width of tension flange. On the other hand, the results from design equations of design codes for estimating load capacity of girders against web sidesway buckling are too conservative in comparison to the proposed model. The critical load is affected by tension flange clearly, and occurrence of this type of instability is credible in other sections such as T- shape beam but in a lower critical load with respect to the I-shape sections. Also the results from the new model are in good agreement with that of experimental data. Finally, • It seems that only the existence of an area in the web affected by a tension stress field do not cause web sidesway buckling and transformation of tension stress field into compression field determents on initiation of instability.}, Keywords = {web sidesway buckling,Instability,tension flange,steel beam,Critical load}, volume = {15}, Number = {1}, pages = {56-73}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-170-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-170-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {rezaee, Abas}, title = {Bio-electrochemical reduction of nitrate from wastewater using graphite-coated multi-walled carbon nanotubes}, abstract ={Due to extensive usage of nitrogenous fertilizers and discharge of industrial and domestic wastewater, nitrate contamination of water is becoming a main environmental concern. High levels of nitrate in drinking water causes serious health problems such as methemoglobinemia in infants and gastric cancer. Because of such health problems, nitrate removal from water is urgent and has been a hot topic over the recent years. Various technologies such as the ion exchange, reverse osmosis, electrocatalytic, adsorption, electrodialysis and biological process, have been used to eliminate nitrate ion from water and wastewater. Nevertheless, these methods have several drawbacks such as high installation and maintenance costs, difficult operation, brine production, membrane fouling, further treatment, slow process and carbon source requirement. A large number of investigators thus have focused on the reduction of nitrate by the electrochemical process usually because of its efficiency, very low sludge production, small area occupation and facile operation. Integration of electrochemical and biological processes as bioelectrochemical systems has been recommended to overcome the potential problems. In bioelectrochemical denitrification, denitrifying microorganisms make use of hydrogen generated at the cathode by the electrolysis of water as an electron donor to reduce nitrate into nitrogen gas. Autohyrogenotrophic denitrifying bacteria commonly adhere to the cathode surface and make a biocathode. Therefore, Cathode electrode material is one of the major factors that affecting in the bioelectrochemistry efficiency. Cathode material can directly affect to denitrifying bacteria attachment, hydrogen production, electron transfer and electrical conductivity. Bioelectrochemical process can be used to eliminate nitrate through a catholic reduction process. Carbon material has high mechanical strength and a rough surface which is ideal for the formation of biofilm as compared with metal materials. However, carbon materials are difficult to apply in large scale processes due to high electrical resistivity that tend to increase electrode ohmic losses. Hence, carbon electrodes are supported by a conductive material current collector such as carbon nanotubes and metallic materials. Carbon nanotubes have a good biocompatibility with bacteria and have not shown negative effect on biofilm formation. It had been reported that carbon nanotubes can facilitate transfer of electrons between bacteria and electrode in bioelectrochemistry. The aim of this study is bio-electrochemical removal of nitrate from wastewater using carbon nanotubes immobilized in cathode. This study has been done in a bathe scale bioelectrochemical rector with a two chambers. Considering that nitrate reduction done in biocathode, carbon nanotube used in cathode for increasing nitrate removal. The effects of pH, current density and retention time were evaluated for nitrate removal in a bio-electrochemical reactor.The highest nitrate reduction rates were occurs in neutral pH and current density of 15 mA/cm2. Furthermore, at current density of 15 mA/cm2 and retention time of 8 hours, the bioelecterochmical system can reduce the nitrate levels to below the environmental standard.The results showed that multi-wall carbon nanotube as cathode modifier increase the nitrate reduction efficiency about 14 persent. The use of multi-wall carbon nanotube can increased biofilm formation and therfor the reduction time for achieving to nitrate standard was reduced.}, Keywords = {Bioelectrochemical,Nitrate,Denitrification,Carbon nanotubes}, volume = {15}, Number = {1}, pages = {57-65}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1373-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1373-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {mohammadaliha, mohammadreza and Rezaiefar, Mohammadhossein and Fazaeli, Hass}, title = {Evaluation of mixed mode fracture resistance of different asphalt concretes-An Experimental study}, abstract ={Asphalt cracking is one of the major distress and deterioration modes of pavements of roads especially in the cold regions. Different types of cracks such as top-down, reflecting and alligator cracks are usually observed in the asphalt pavements. These cracks may be initiated due to improper construction and implementation of paving process, daily or seasonal cyclic thermal loads and mechanical traffic loading induced by moving vehicles. Consequently, the investigation of crack growth behavior in the asphalt overlays is an important issue for design, construction and maintenance of roads and highways. Due to the applied thermal and mechanical stresses, the cracks initiated in the asphalt layers may often experience different deformations including mode I(tensile or opening), mode II (shear or sliding) and any combinations of opening-shearing deformations (i.e. mixed mode I/II). Fracture toughness is a key fundamental parameter for investigating the crack growth behavior of cracked bodies. From the other hand, since asphalt mixtures are composite materials composed of aggregate, binder and air void, their fracture behavior might be affected by the asphalt characteristics specifications. Hence in this research the influences of asphalt characteristic specifications (including the type and size of aggregates, bitumen type, air void content and the mixture composition) is investigated experimentally on the mixed mode fracture toughness of different asphalt mixtures. For conducting the fracture toughness experiments, semi circular bend (SCB) specimens containing a vertical edge crack and subjected to asymmetric three-point bend loading was used. In order to study the influence of mixture characteristic specifications on the value of fracture toughness, two aggregate types (i.e. limestone and siliceous), two aggregate sizes (with nominal maximum aggregate sizes 19 mm and 4.75 mm), two binders (60/70 and 85/100) and two air void percentages (i.e. 4% and 6%) were considered for manufacturing asphalt mixtures. The SCB specimens were then tested under two different loading mode mixities (i.e. Me = 0.8 (mixed mode condition with dominantly tensile deformation) and Me = 0.38 (mixed mode condition with dominantly shear deformation) at -15oC. The load-displacement curves for the whole samples were linear which revealed the linear and elastic behavior of asphalt mixtures at the tested low temperature. Thus, the corresponding values of fracture toughness (KI, KII and Keff) were determined using the obtained fracture loads and the available formula. The experimental result showed that the mixed mode cracking resistance of asphalt mixtures is significantly affected by their properties. Analysis of results indicated that the specimens containing 4% air void (i.e. with the more compacted mixtures) show greater resistant against cracking than the asphalt specimens containing 6% air void. Meanwhile by increasing the maximum aggregate size the fracture toughness is also increased. Mixtures made of limestone aggregates and softer binders had more fracture toughness. Analysis of results also showed that when the contribution of mode II deformation is increased, the influence of air void and aggregate size on the fracture toughness of tested asphalt mixtures becomes negligible.}, Keywords = {Asphalt concrete,Fracture toughness,Semi circular bend specimen (SCB),Mixed mode I/II,Low temperature Cracking}, volume = {15}, Number = {1}, pages = {73-85}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-12274-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-12274-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Toopchi-Nezhad, Hami}, title = {The Simulation of Mullins’ Effect in Load-Displacement Hysteresis Loops of Fiber-Reinforced Elastomeric lsolators}, abstract ={This paper briefly reviews Fiber Reinforced Elastomeric Isolators (FREIs) as a relatively new type of elastomeric bearings. In comparison with conventional Steel Reinforced Elastomeric Isolators (SREIs) that are reinforced with steel plates, FREIs utilize fiber fabric layers as the reinforcement material. The fiber reinforcement is employed to prevent the lateral bulging of elastomer layers when the bearing is subjected to vertical compression. Fiber reinforced isolators are categorized in two groups, namely, “bonded-“ and “unbonded-“ FREIs, depending on the boundary conditions at top and bottom surfaces of the bearing. The main objective of this paper is to simulate the lateral load-displacement hysteresis loops of unbonded-FREIs. In an unbonded-FREI, no bonding is provided between the bearing and its top and bottom contact supports. As such, shear forces are transferred via friction at the contact surfaces. When an unbonded-FREI is deformed laterally, portion of its contact surfaces roll off the contact supports, and the bearing exhibits a specific deformation called “rollover deformation”. As a result of rollover deformation, the effective lateral stiffness of the bearing is decreased significantly. This in turn improves the seismic isolation efficiency due to the increased base isolated period of bearing. The ultimate lateral displacement in an unbonded-FREI may achieve when the originally vertical faces of the bearing contact top and bottom supports. Lateral load-displacement response in an unbonded-FREI is characterized with a gradual softening (due to rollover deformation) that is followed by a stiffening behavior at the ultimate stage of lateral bearing displacement. Under a cyclic excitation, the response characteristics of the bearing during the first load-cycle are different than the subsequent cycles of the same load amplitude. This phenomenon that is specific to elastomeric materials is known as Mullins’ effect. In this paper an extended Bouc-Wen model is developed to simulate the lateral load-displacement hysteresis loops of unbonded-FREIs. The model captures the gradual softening and ultimate stiffening behavior in the load-displacement curve of the bearing, and addresses the Mullins’ effect in the simulation of hysteresis loops. The proposed model comprises two simultaneous coupled equations which employ six constant coefficients altogether. To determine these coefficients, the model is fitted to experimentally-evaluated load-displacement hysteresis loops of prototype bearings. The experimental loops are obtained from cyclic shear tests that are conducted on the bearing while it is subjected to constant vertical compression. In order to account for Mullins’ effect, an individual set of coefficients corresponding to unscragged loops (the first cycle of each displacement amplitude) are evaluated. The second set of coefficients is attributed to scragged response (subsequent cycles of each displacement amplitude) of the bearing. To simulate the load-displacement hysteresis loops, the proposed model switches between the first and the second set of coefficients depending on the unscragged or scragged state of the elastomer, respectively. A constraint is imposed on the model to assure its continuity when the model coefficients are alternated. Comparison between analytical and experimental results (shake-table test data) indicates that the proposed model is accurate in dynamic response simulation of the unbonded-FREIs studied in this paper.}, Keywords = {Fiber Reinforced Elastomeric Isolators,Hysteresis Loops,Mullins’ Effect,Bouc-Wen Model,Time history analysis}, volume = {15}, Number = {1}, pages = {86-96}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-9630-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-9630-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Pourjafar, Arash and Mahinroosta, Rez}, title = {Investigation of stress reduction in sandy soils during saturation}, abstract ={Abstract:If dry cohesionless soil material is saturated, stress reduction will occur in the soil mass, followed by sudden deformation,which is called collapse settlement. In this research, effect of saturation on the shear strength parameters of sandy soils and effective factors on collapse behavior of this material has been investigated by triaxialshear device. First of all, preliminary tests were performed in order to prepare physical properties of sandy soils including: grain-size analysis, specific gravity, maximum and minimum densities. After providing soil samples with specific relative densities, dry and saturated triaxialtests were carried out in different confine pressures to evaluate shear strength parameters of these materials. In order to investigate the stress reduction of material due to saturation, triaxial tests were done initially on dry samplesand shearing continued until a proposed stress level; keeping constant axial strain, samples were saturated until a period of time and shearing was continued again to reach failure in the wet state. In this way, effect of diverse factors such as confining pressure, shear stress level, relative density, initial moisture content and size of particles on the stress reduction of sandy material were investigated.Abstract:If dry cohesionless soil material is saturated, stress reduction will occur in the soil mass, followed by sudden deformation,which is called collapse settlement. In this research, effect of saturation on the shear strength parameters of sandy soils and effective factors on collapse behavior of this material has been investigated by triaxialshear device. First of all, preliminary tests were performed in order to prepare physical properties of sandy soils including: grain-size analysis, specific gravity, maximum and minimum densities. After providing soil samples with specific relative densities, dry and saturated triaxialtests were carried out in different confine pressures to evaluate shear strength parameters of these materials. In order to investigate the stress reduction of material due to saturation, triaxial tests were done initially on dry samplesand shearing continued until a proposed stress level; keeping constant axial strain, samples were saturated until a period of time and shearing was continued again to reach failure in the wet state. In this way, effect of diverse factors such as confining pressure, shear stress level, relative density, initial moisture content and size of particles on the stress reduction of sandy material were investigated. time and shearing was continued again to reach failure in the wet state. In this way, effect of diverse factors such as confining pressure, shear stress level, relative density, initial moisture content and size of particles on the stress reduction of sandy material were investigated.Abstract:If dry cohesionless soil material is saturated, stress reduction will occur in the soil mass, followed by sudden deformation,which is called collapse settlement. In this research, effect of saturation on the shear strength parameters of sandy soils and effective factors on collapse behavior of this material has been investigated by triaxialshear device. First of all, preliminary tests were performed in order to prepare physical properties of sandy soils including: grain-size}, Keywords = {collapse settlement,sand,saturation,triaxial test,Shear Strength}, volume = {15}, Number = {1}, pages = {97-108}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7830-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7830-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {nazari, narges}, title = {Simulation of Sediment Transport at Straight channel and Lateral Intake}, abstract ={In this paper, the Lagrangian tracking of individual particles was performed at the straight channel and the lateral intake. This study is conducted for the aim of investigation of Discrete Phase Model )DPM (for simulation of tracking of individual sediment particles and also estimation of the rate of bed load at the entrance of intake related to the main channel. The Reynolds stress transport model )RSM) of the FLUENT software was used for evaluating the turbulent flow characteristics. The study was conducted in two parts. At the first part, the particle movement was simulated in the straight channel for evaluating of the model operation. The comparison of numerical results (predicted) and experimental data (measured), which were done for this purpose, confirmed numerical simulation. In the second part, sediments movement pattern in lateral intake from straight direction investigated from quantitative and qualitative views and compared with available experimental data. The qualitative analysis of sediments movement showed a shape of wedge liked sand bar forms by bed load at the entrance of lateral intake. The quantitative comparison of the predicted and measured Qs (ratio of the bed load discharge in lateral intake to the bed load in main channel) shows predicted values were more than the measured values. In this paper, the Lagrangian tracking of individual particles was performed at the straight channel and the lateral intake. This study is conducted for the aim of investigation of Discrete Phase Model )DPM (for simulation of tracking of individual sediment particles and also estimation of the rate of bed load at the entrance of intake related to the main channel. The Reynolds stress transport model )RSM) of the FLUENT software was used for evaluating the turbulent flow characteristics. The study was conducted in two parts. At the first part, the particle movement was simulated in the straight channel for evaluating of the model operation. The comparison of numerical results (predicted) and experimental data (measured), which were done for this purpose, confirmed numerical simulation. In the second part, sediments movement pattern in lateral intake from straight direction investigated from quantitative and qualitative views and compared with available experimental data. The qualitative analysis of sediments movement showed a shape of wedge liked sand bar forms by bed load at the entrance of lateral intake. The quantitative comparison of the predicted and measured Qs (ratio of the bed load discharge in lateral intake to the bed load in main channel) shows predicted values were more than the measured values. from quantitative and qualitative views and compared with available experimental data. The qualitative analysis of sediments movement showed a shape of wedge liked sand bar forms by bed load at the entrance of lateral intake. The quantitative comparison of the predicted and measured Qs (ratio of the bed load discharge in lateral intake to the bed load in main channel) shows predicted values were more than the measured values.}, Keywords = {Sediment,Particle,Lagrangian Approach,Fluent,lateral intake}, volume = {15}, Number = {1}, pages = {109-119}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-6728-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-6728-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Investigating the intergranular interaction to define the equivalent steady state}, abstract ={Many studies have been focused on soil-related problems so far. These may include consolidation, soil settlement, or swelling for clayey soils. However, before some incidents like liquefaction phenomena had been recognized, sands were not defined as a sort of problematic soil. After some liquefaction and flow failure took place during Niigata and Alaska earthquakes in 1964, comprehensive studies were carried out to explain sands behavior under various situations. One of the most crucial factors that can affect soil behavior is fines content and their types. Many investigations have been conducted on behavioral characteristics of clean and silty sands since liquefaction first observed in these kinds of soils. Most of studies suggest that sand liquefaction potential boosts with an increase in silt content until a threshold value and after that it starts to decline as silt content increases. Most of the studies conducted so far have mainly focused on clean sand or its mixtures containing non-plastic fines with not much attention paid to the soil mechanics of the critical state of clayey sands. The reason for this neglect might have been the misconception that plastic properties in clay prohibit flow behaviors and liquefaction. However, the studies of Northridge 1994, Kokaeli 1999, Chi Chi 1999, and Niigata 2004 earthquakes have indicated that notable settlements occur in soils containing considerable amounts of clay, resulting in great destruction. The researchers have emphasized that more detailed investigations are needed to determine the critical state behavior of clayey sands The steady state line or critical state line is one of the main factors used in the critical state topics. It is used for investigating the variation of liquefaction potential, calculating state parameters and also determining the parameters affecting on the collapse or state boundary surface shapes. Sand skeleton void ratio, equivalent void ratio and the interaction of sand and fines are being the main subjects of sand critical state behavior researches. In this paper the possibility of equivalent steady state line is investigated to order to reach a unique frame work for interpretation the critical state behavior of clayey sands. The inter granular interaction of coarse and fine grains and the fine communication in inter granular contacts are investigated to reach the equivalent void ratio. An appropriate and useful relation is presented to calculate the fine contribution percent in inter granular contacts and so the equivalent void ratio trough performing numerous cyclic triaxial on different combination of sand and clay, evaluating the variation of liquefaction resistance and finally mathematical analysis the results. Increasing the fine content has increased the instability of combinations. Also it has been shown that the different steady state lines can be converted to a one equivalent steady state line using the proposed relation. The latter means that it would be possible to predict the steady state line of every optional mixture of sand and fine trough performing some tests just on clean sand. In order to certificate the proposed relation, it has been verified based on some previous researches.}, Keywords = {Steady State Line,Cyclic Triaxial,Equevalent void ratio}, volume = {15}, Number = {1}, pages = {119-130}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10027-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10027-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {naghipour, morteza and Salimbahrami, Seyyed and Nemati, Marzieh}, title = {The Role of Ductile Behavior of Connection Elements on Seismic performance of CBF}, abstract ={Nonlinear behavior of members and their connections during earthquake caused ductility in buildings. Also increasing the number of resisting elements of structure reduces cost of repair and reconstruction in bending structures. In contrast, the concentrically brace frames do not have sufficient ductility But their vulnerable members are limited, thus their reconstruction were much less expensive than bending frames. In order to overcome concentrically brace frames disadvantages and they providing good ductility for them, Extensive research has been conducted in the past two decades by researchers. Several methods have been proposed by various researchers which were resulted in increasing the ductility of concentrically brace frames. In this research, a new type of energy dissipation elements was introduced. This dissipation consists of a ring which increased the ductility and earthquakeenergy absorption and can be used in braced frames. Also, during an earthquake, it has depreciates significant portion of input energy by entrance to non-linear phase and forming flexural plastic hinges, so it prevent entrance of other members to non-linear phase and buckling of brace members. In order to increase the capacity of this member, a box was used that connected to the ductile ring by two plates. By increasing the diameter, rate of ductility decreased. However increasing the thickness would enhance the ductility. Stresses and deformations were been studied by using the finite element under cyclic loads. Obtained hysteresis curves indicate that the introduced element can be act as an energy absorbing member and also act as a fuse to control the buckling of brace, while providing to the required ductility. Pushover analyses for determining the seismic demand of structures and especially in earthquake engineering based on performance, it has been considered by many researchers. General basis of this method is a nonlinear mathematical model of the structure was under a lateral load pattern and this lateral load increases at a constant rate until the structure reaches a predetermined target displacement. This target displacement was measured at a control point. During the ascending increase in lateral load, resistance and stiffness of structural components were corrected at each step according to predefined nonlinear. Also performance of this ductile element was investigated in 2D concentrically brace frames under Pushover analyses. Obtained results from pushover analysis indicated that ductile element can decrease base shear force and also increase ductility of structure. The obtained results indicate that installation or replacement of steel ring in proposed connection was easily possible with low cost and high speed. Furthermore, nonlinear static analysis obtained results reflects the lower base shear force for braced frame with proposed element compared to braced frames without proposed element Which results in Cutting down construction and foundation strengthening costs of building. At the end, results of Pushover analysis of concentrically braced systems can be mentioned. High behavior coefficient of structural braced systems with proposed element represents suitable performance and ductility of proposed element in building.}, Keywords = {Concentrically Brace,Ductile Rings,Finint Element,Pushover}, volume = {15}, Number = {1}, pages = {131-143}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10152-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10152-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Stress path effect on wetting behaviour of unsaturated soils}, abstract ={One of the most important behavioral aspect of unsaturated soil is, engendered deformation due to wetting. Numerous research works exist in the literature concerning wetting behaviour of unsaturated soils. However the majority of them have been done in oedometric conditions. The oedometric apparatus, despite its simplicity, presents a certain limitations. In fact in this apparatus lateral deformation is zero, Also in the its classical form, confining pressure cannot be controlled and pore water pressure and matric suction measurement are not possible. Therefore, the effect of stress path cannot be studied. These limitations are not relevant in the triaxial apparatus. On the other hand, there is a few study concerning stress path on wetting behaviour of unsaturated soils. In the present study, using a special triaxial apparatus, influence of stress path on wetting behaviour of an unsaturated sand-fine mixture, for two level of initial deviator stresses and different initial suctions, was studied. The selected soil is composed of 60% sand, 25% clay and 15% silt. This soil is non plastic and according to Unified Soil Classification System, it is classified as silty sand (SM). The specimens were prepared using the moist tamping method. The purpose of using static wet compaction as opposed to dynamic compaction is to obtain a more homogenous specimen in terms of density and shear strength. Before applying wetting process, two types of conventional stress paths were induced on soil specimens,. The first stress path was coincided with k0 lines. For obtaining the oedometric condition using triaxial apparatus, the area of specimen was kept constant by augmentation of confining pressure incrementally. In the second stress path, first, specimen was isotropically consolidated, then axial stress was increased, while confining stress was maintained constant during loading process. Two groups tests including low and high levels of initial deviator stress state were considered in this study. For every group, the level of initial stress exerced on specimens, before wetting step, was similar. All of specimens were in equilibrium regarding to pore-air and pore-water pressures. Pore-air pressure was kept constant equal to 250 kPa for all of specimens. During wetting process external loadings, applied on specimens, were constant, while matric suctions was decreased incrementally due to change in water content. There are several conclusions deduced from this study. Difference between observed deformations in consolidation phase (before wetting) for two stress paths depends on the level of deviator stress, so that for low level of deviator stress this difference is insignificant. However for high level of deviator stress, this difference is considerable. Engendered deformation during wetting for a given stress path depends essentially on the levels of matric suction and deviator stress at the start of wetting, so that, deformation due to wetting increase with increasing in initial suction or initial deviator stress. Based on the measured axial and volumetric strains during wetting phase, in the axisymmetric triaxial conditions, lateral strain was calculated. The obtained results indicate that lateral strain is considerable, therefore, evaluation of wetting effect in oedometric conditions underestimates deformation field}, Keywords = {unsaturated soil,stress path,wetting,triaxial test}, volume = {15}, Number = {1}, pages = {143-155}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-9937-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-9937-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Prediction of collapse potential of soils using Artificial Neural Network}, abstract ={Collapsible soils are soils that compact and collapse after they get wet. The soil particles are originally loosely packed and barely touch each other before moisture soaks into the ground. As water is added to the soil in quantity and moves downward, the water wets the contacts between soil particles and allows them to slip past each other to become more tightly packed. Water also affects clay between other soil particles so that it first expands, and then collapses like a house of cards. Another term for collapsible soils is "hydrocompactive soils" because they compact after water is added. The amount of collapse depends on how loosely the particles are packed originally and the thickness of the soil that becomes wetted. Collapsible soils consist of loose, dry, low-density materials that collapse and compact under the addition of water or excessive loading. These soils are distributed throughout the southwestern United States, specifically in areas of young alluvial fans, debris flow sediments, and loess (wind-blown sediment) deposits. Soil collapse occurs when the land surface is saturated at depths greater than those reached by typical rain events. This saturation eliminates the clay bonds holding the soil grains together. Similar to expansive soils, collapsible soils result in structural damage such as cracking of the foundation, floors, and walls in response to settlement. Collapsible soils may be suspected in undeveloped areas that have young, accumulating sandy and silty soils in dry areas. The soils may be confirmed to be collapsible through engineering testing. These tests include study of seismic waves through the soils, rates of drilling through the soils (blow counts), and testing undisturbed soil samples obtained by careful drilling for compaction after wetting. In this study, the ability of Artificial Neural Networks (ANN) has been investigated to determine the collapse potential of soils. Therefore, different samples of collapsible soil have been collected from an area (Zahedan plain). General tests were performed on the samples in the laboratory and 130 samples of collapsible soil from different depths and locations were recorded in the database. The collapse potential tests (One-dimensional collapse test) was carried out on the samples and with the aim of further investigations, the grain size distribution, specific gravity, atterberg limits and strength properties of the samples were performed. In the later stages, the collapsible samples data were prepared for the artificial neural networks input. After the network training process and the subsequent learning, some network models have been selected under experiments, which include six inputs and one output. According to the predicted results, it was indicated that the correlation between experimental and predicted data by the ANN is 95%. Furthermore, the results show that artificial neural networks can predict collapse potential of soils, also the calculations and required tests will be reduced due to their simple use and inexpensive tests.}, Keywords = {Collapsible soil,Collapse Potential,Modeling,Artificial Neural Networks (ANN)}, volume = {15}, Number = {1}, pages = {155-165}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-925-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-925-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {KaramiMohammadi, Rez}, title = {Performance-based design optimization under the set of earthquake records using the uniform deformation theory}, abstract ={Performance-based design optimization (PBDO) is a relatively new concept in structural seismic design optimization. One of the PBDO methods which has been introduced in recent years is the optimization based on the uniform deformation theory. This method is quite different from other optimization techniques and formed based on the concept of structural performance and uniform distribution of deformation demands in the structure subjected to the seismic excitation. The aim of this method is to assign specific sections to elements such that all of the elements can reach their allowable deformation capacity during the earthquake. According to this theory, inefficient material is gradually shifted from the strong to weak areas leads to a uniform deformation (ductility) state at the end of a repetitive process. Although the base of this theory and proposed algorithm is to attain a uniform state of deformation in the whole structure, but the allowable limit of deformation values defined in PBD codes is not constant for all of structural elements. Additionally, in these codes, some actions of structural elements may be controlled by deformation and some controlled by force. Therefore, by considering the acceptance criteria of PBD codes, it is not possible to reach a uniform deformation state in the whole structure. Hence, in this paper uniform distribution of demand capacity ratio (DCR) is considered instead of uniform state of deformation. Historical review of applying this methodology shows that researchers mostly have used it to the optimum design of the structures under the earthquake records separately. Since earthquakes are random by nature, it is unlikely that the same earthquake ground motion will be repeated at some future time. This reveals that design based only one earthquake is insufficient and it is necessary to consider several earthquakes in checking the dynamic responses of a building. This paper presents an algorithm to PBDO of steel moment frames under set of ground motion records using the basic concepts of the uniform deformation theory. The proposed method consists of two phases. In the first phase of the search, to enhance the convergence rate, the search space of design variables is assumed to be continuous. Additionally in this phase of the search, only the deformation-controlled elements may vary. In the Second phase of the search, first for each structural element groups, the nearest discrete section to the imaginary section achieved in the first phase is identified and selected and then the structure is analyzed again and the DCRs are controlled. In this phase, acceptance criteria for both deformation and forced-controlled elements are supposed to be satisfied. Efficiency of the proposed algorithm is demonstrated in the optimum design of two baseline steel moment frames under a set of ground motion records. Results indicate that the proposed algorithm has a high speed to reach the optimum solution. The results are also compared with the optimum designs obtained by pushover analysis. It is shown that the optimization based on the pushover analysis results higher frame weight than time history analysis.}, Keywords = {Structural optimization,performance-based design,Uniform deformation theory,Nonlinear time-history analysis,pushover analysis}, volume = {15}, Number = {1}, pages = {165-175}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11039-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11039-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Rahmani, Hamid and Jokar, Mohsen and Parvinnia, Mohamm}, title = {Effect of Nano-SiO2 and Silica Fume on Durability of High Strength Concretes under Sulfuric Acid Attack}, abstract ={Concrete is one of the most practical and durable construction materials due to economic aspects, abundance of the constituents, adaptability with the environment and its high compressive strength and durabity. High strength concretes are used in the most substructure constructions such as bridges, dams, towers, silos and etc. . The selection of proper aggregates and the constituents affects on the concrete properties such as strength, permeability, and durability. Therefore, optimization of mix designs is necessary to produce high strength and low permeability concretes. Although most of the concrete structures are constructed for 50 years sevice life, however, some of them are sometimes damaged due to sulfuric acid attack. The rate of concrete corrosion in sulfuric acid is a process of dissolution, sedimentation and leaching depends on the chemical compounds of cement, paste reactivity, aggregates type and their grading curves and the proportion of concrete components. Moreover, wetting and drying cycles increases the acid penetration and consequently the rate of corrosion. Remarkable concrete damages have been reported in Australia, Japan, the countries around Persian Gulf, Germany, South Africa and U.S.A.. Therefore, It will be necessary to repair or replace the damaged structure after the attack and it would be very expensive and creates many social problems. Nevetheless, several reports have been published to investigate plain concretes durability in acidic environments, but first, the results are paradoxical for example, silica fume effect against sulfuric acid attack and second, their studies have been conducted on the native construction materials such as fly ash or blast furnace slag. Therefore, it seems necessary to investigate concrete durability against sulfuric acid attack by using new materials such as nano-SiO2. In the present study, durability of concretes containing silica fume, nano-SiO2 and ultra fine Quartz powder was investigated under sulfuric acid attack. Concrete samples of four mix designs, including Silica Fume, nano-SiO2 and ultra fine Quartz powder as cement filler, were investigated to find optimum content of Silica Fume and nano-SiO2. Also to obtain a high strength concretes, ideal grading curve of aggregates and cementitious materials were used which lead to decrease cement consumption. Results show that the very low porosity concretes were obtained based on water absorption test results in comparison to plain concretes. Also, the 28 days compressive strength of all mixtures were obtaied more than 500 kg/cm2 using no more than 325 kg/m3 cementitious material content. Moreover, the durability of concretes against sulfuric acid attack, which is increased by silica fume and nano-SiO2, directly related to the 90 days water absorption. In addition, After 6 months of immersion in sulfuric acid solution with pH of 1.0, the mixture containing 8% silica fume, 2% nano-SiO2 and 25% ultra fine Quartz powder showed the best performance.}, Keywords = {Sulfuric Acid Attack,Silica Fume,Nano-SiO2,High Strength Concrete}, volume = {15}, Number = {2}, pages = {1-12}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11787-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11787-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Rahimi, Mohammad Ghasem and Ayati, Bit}, title = {Investugation of Moving Bed Biofilm Reactor Capability in Treating Wastewater Containing Petrolium and Gas Oil}, abstract ={Abstract: Wastewater contaminated by petroleum compounds includes a wide range of hydrocarbons with different concentrations. Due to high amounts of toxic multiple cyclic aromatics, this type of wastewater may cause significant damages to water resources and human health, which have to be treated before discharging to the environment. Different processes have been applied for treating these kinds of wastewater. The most conventional systems are biological processes especially activated sludge that is being used in the most of the Iranian refineries. In recent years, biofilm processes have been replaced for treating different types of wastewaters because of bulking and foaming problems in the suspended systems. Due to the least deficiencies and restrictions, these processes have been proved as a reliable method for removal of wastewater pollutants. Therefore, in this study, the capability of treating petroleum wastewater was investigated using Moving Bed Biofilm Reactor (MBBR). This study was conducted in a lab-scale batch plastic rectangular cube pilot (L: 24 cm, W: 17 cm, H: 9 cm). To get a compound similar to petroleum effluent of Tehran Refinery, the mixture of gasoline (C16 - C20) and crude oil (C8 - C37) by the ratio of 1 to 2 was prepared. At first, sewage sludge was adapted with hydrocarbon compounds at COD equal to 100 mg/L (or TPH of 27.4 mg/L). Then petroleum hydrocarbons was injected to the reactor with a COD range of 200 to 2500 mg/L (TPH of 52 to 400 mg/L); and COD and TPH removal efficiency was measured at different retention time. Also the dominant mechanism, kinetic of biological reactions, the effect of suspended microorganisms and carrier filling ratio were studied. The highest COD removal efficiency of 85 percent was obtained at influent COD= 1000 mg/L, HRT= 72 hr and filling ratio = 50 percent. The removal trend of organic compounds from the end of adaptation stage (COD= 100 to 1000 mg/L) at resident time of 8, 12 and 24 hours has been varied between 62 and 48 percent. TPH removal efficiency in aforementioned range, followed a smooth trend; so that in HRT= 72 hr, the removal efficiency reduced from the initial 84 percent at TPH= 50 mg/L to 75 percent at TPH= 400 mg/L. The ratio of COD to input TPH was 3.82 and the range of ratios of COD to output TPH at resident times of 24, 48 and 72 hours were 3.09 - 4.80, 9.00 - 13.89 and 10.80 - 15.63, respectively. The results have shown that Grau and Stover- Kincannon were the best models for describing the biological kinetic data. The results have shown that MBBR system is a proper method for treating petroleum hydrocarbons, due to adequate ability to decomposition of these kinds of pollutants.}, Keywords = {COD,TPH,COD,TPH,Grau,Stover-Kincannon,Biodegradation}, volume = {15}, Number = {2}, pages = {13-22}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1081-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1081-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {RazaviToosi, Seyedeh Leila and Ayyoubzadeh, Seyyed Ali and Valizadeh, Alirez}, title = {2D Simulation of Water and Sediment Flow in Dam Break by Smoothed Particle Hydrodynamics (SPH)}, abstract ={Computational Fluid Dynamics (CFD) implementations are also classified as the Lagrangian and Eulerian methods. Smoothed Particle Hydrodynamics (SPH) is a mesh free particle method based on Lagrangian formulation with a number of advantages. This method is obtained approximate numerical solutions of the equations of the fluid dynamics by replacing the fluid with a set of particles. All particles carry their properties and then the advection is taken care automatically. In contrast, Eulerian mesh based numerical methods have difficulties such as the problem of numerical diffusion due to advection terms. Because of the simplicity and robustness of SPH, this numerical method has been extended to complex fluid and solid mechanics problems. The important advantage of SPH is that the muli-phase flows can be modeled by SPH and each particle can be assigned to a different phase. In this paper, the SPH method is used for simulating water and sediment flow in dam break problem. The government equations are momentum and continuity equations which are described in a Lagrangian framework. Also, the compressible flows are modeled as a weakly compressible flow via the equation of state. The XSPH equation is applied for each particle movement at each time step. The Wendland kernel is applied as smoothing function. Sediments are treated as non-Newtonian fluid and for simulating them the non-Newtonian models are used. In this paper, the combination of two rheological models named Bingham and Cross is used. The predictor- corrector algorithm is applied. The time step is controlled by Courant condition (CFL), the forcing terms and the viscous diffusion terms. On the other hand, the laboratory experiment of dam break is performed and the new experimental set up was built. At first, the column of water with a height of 0.5 m and the wide of 0.25 m is blocked by a partition gate. The bottom of the water column is covered with non cohesive sediments. The sediments are sands with d50=1.4 mm. The partition gate separates the water column from the downstream channel and the speed of partition gate is more important. Then the partition gate is removed with a specific velocity. The partition gate opens completely from above with a constant speed of 0.6 m/s. The flow motion is recorded by digital camera system. Finally, a comparison between experimental results and computational results is carried out and the errors are calculated. The error of sediment height variations in specific horizontal distances (x=5 cm and 14 cm) in reservoir are 6.55% and 5.94%, respectively. Also, the sediment surface profiles are shown in different times. The comparisons are shown good agreements between numerical and experimental results. The good agreement proves the ability of the present SPH model to simulating two phase flows.}, Keywords = {Two phase flow,Sediment,SPH}, volume = {15}, Number = {2}, pages = {23-34}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1728-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1728-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Zarrinmehr, Amirali}, title = {Parallelization of Ant Colony Algorithm in Transportation Discrete Network Design}, abstract ={Transportation Discrete Network Design Problem (TDNDP) is defined as the problem of selecting a subset of proposed projects (i.e. new highways) for construction, while holding the budget constraint, so as to minimize the total travel time of the network users. TDNDP has been often known as a problem with the bi-level programming formulation. At the upper level, this formulation allows for finding the optimal selection of the projects, while taking into account the route choice behavior of network users at its lower level. Such a formulation falls into the category of problems in the NP-Hard complexity class. These are resource-intensive problems which have not been exactly solved yet with any efficient algorithms. As a result, the main body of TDNDP related literature has ignored the exact solution of the problem and addressed TDNDP through heuristic and meta-heuristic approaches. These approaches contribute to find a rather high quality solution in a reasonable amount of time. Using heuristic and meta-heuristic algorithms is one way to overcome the complexity of NP-Hard problems like TDNDP. However, application of parallel computing still remains as another way to speed up the performance of such algorithms. Parallel computation aims at harnessing multiple computing resources, e.g. computer processors, to solve a certain problem. Different parallelization paradigms have been developed so far to parallelize solution algorithms. These paradigms generally address the two fundamental questions of how and when the required information should be exchanged among the processors. A master-slave (MS) parallelization paradigm is one of the basic paradigms in which one processor, namely the master, holds the main information of the problem. The master generates new jobs whenever needed, distributes them among other processors (i.e. slaves), and exploits them to work on the sent jobs. This paper is going to explore the application of parallel computation in a meta-heuristic algorithm in TDNDP. A parallel Ant Colony Algorithm (ACA), based on the study of Poorzahedy and Abulghasemi, is proposed with the MS parallelization paradigm. The Chicago Sketch transportation network is considered as a case study with 16 bi-directional proposed projects. The results are reported in three runs over a cluster of 8 processing cores for both single-core and parallel ACAs. According to the performances observed in this paper, parallel algorithms can achieve high quality solutions in 4000 seconds, while this happens for the single-core algorithms in 10000 seconds. The parallel ACA finds the exact solution of the problem in two instances out of three runs and in the other instance it converges to a solution with 0.07 percent error from the exact solution. The parallel performance of ACA is also reported along with that of the branch and bound algorithm. It is observed that the parallel branch and bound algorithm requires more than 32000 seconds running time to find the exact solution of the problem. More accurate comparisons, however, can only be achieved by running the single-core and parallel ACAs more than the three times used in this paper.}, Keywords = {Transportation Discrete Network Design,Ant colony algorithm,Parallel Computing,Master-Worker Paradigm}, volume = {15}, Number = {2}, pages = {37-50}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10956-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10956-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {sangsefidi, yousef and Mehraein, mojtaba and ghodsian, masou}, title = {Experimental Investigation of the Hydraulic Performance of Arced Weirs}, abstract ={Weirs possess an essential role in dam safety and should spill floods with high return period. The designers can enhance the width of the weirs to increase the discharge capacity. But this has sometomes topography and economic limitations. Arced weirs can be considered as an alternative. A arced weir is a arcuate of a circle in plan-view that provides an increase in crest length for a given channel width that increas the flow capacity for the same head. Also when modification and capacity increase in existing spillways are necessary, this structure is recommended. In this paper, the hydraulic performance of arced weirs located in a reservoir has been studied experimentally. Firstly, dimensionless parameters affecting the performance of arced weirs is introduced using Buckingham π theorem. Then effect of arc angle (θ) and head water ratio (H0/P) on hydraulic performance of arced weirs was experimentally investigated and hydraulic performance of the tested arced weir geometries was compared with a linear configuration. For this purpose, Arches with different radius of curvature from linear to semi-circular configurations ( ) and various head water ratio Were studied. To simulate reservoir conditions, a reservoir simulator was designed and built. Laboratory observations show that the converging of flow over a arced weir causes a locally bulge in the downstream of the weir. This phenomenon was named as flow mound. Results show that arc angle (θ) and head water ratio (H0/P) have a direct effect on the flow mound and an increase in each of them leads to mound height rise. The head-discharge relationship for arced weirs was determined by using a general form of the rectangular weir equation. Data from physical models were used to determine discharge and upstream head for the flat crested weirs installed in the reservoir. from discharge curves, it was found that with increasing angle of weir, that provide an increase in crest length for a given channel width, flow capacity increases for a given upstream head. Discharge coefficients as a function of H0/P for arced weirs are also presented and is compared with linear configuration. The results show that with increasing H0/P, discharge coefficient is declined for each tested configuration. Also with increasingθ , that leads to greater convergence of flow passing over the weirs, discharge coefficient decreases. Efficiency parameter is defined as the ratio of discharge of arced weir to that of liner weir with a same width. From efficiency curves it can be understood that the semi-circular weir can improve efficiency up to about 45%. However for all tested weirs , efficiency decreases with increasing H0/P and it gets close to 1. Finally, based on the results and limitations of this study, a methodology for the design of arced weirs located in the reservoir is presented. By using this method, the geometric parameters if an arced weir that is able to pass a certain flow rate for a given hydraulic head, will be determined.}, Keywords = {Dam,arced weir,head water ratio,discharge,Discharge coefficient}, volume = {15}, Number = {2}, pages = {51-63}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10460-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10460-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {A Study on the Effect of Pile Penetration Length in the Soil Layer on End Bearing Capacity}, abstract ={In geotechnical engineering practice, piles are employed usually where, because of soil conditions, economic or constructional considerations, it is desirable to transmit loads to strata beyond the practicable reach of spread foundations. Many factors affect the behavior of piles such as soil-pile interaction, compressibility of soil, pile construction technique, shape and also type of the pile. Given the many uncertainties inherent in the design and construction of piles, it is difficult to predict with accuracy the performance of a pile. Therefore, several approaches have been developed to overcome the uncertainty in the prediction. These approaches include static analysis, dynamic analysis, dynamic testing, in-situ testing and pile load test. Among these methods, pile load test is the best option to investigate a load-settlement relationship for a specific site and pile. There are different types of piles that cast-in-situ piles are a common type of them. Cast-in-situ piles were successfully applied in different geotechnical conditions and have gained wide acceptance in recent years because of their many advantages over other types of piles. For example, the construction of cast-in-situ piles generates less noise and vibration or in many cases, a large diameter cast-in-situ pile can replace a group of piles which in turn eliminates the need for a pile cap. The axial capacity of a cast-in-situ pile can be estimated by summing the skin friction capacity and the bearing capacity of the pile base. The skin friction develops between the shaft concrete and the surrounding soil. The skin friction is transmitted to the soil along the length of drilled shaft. However, the end bearing is analogous to shallow foundation bearing capacity with a very large depth of footing. The end bearing capacity is transmitted to the base of drilled shaft. The side resistance of piles is, in most cases, fully mobilized well before the maximum base resistance is reached. In other words, the movement of the pile base against the soil necessary to mobilize the ultimate base resistance is considerably larger than that necessary for mobilizing the side resistance. After full mobilization of side resistance, any increment of axial load is transferred fully to the base. As the side resistance is mobilized early in the loading process, the determination of base resistance is a key element in the design of cast-in-situ piles bearing in sands. The end bearing capacity of cast-in-situ piles can have an important role in their design so that in some projects, cast-in-situ piles are designed primarily based on the magnitude of their end bearing capacity. In this study, by performing axial compression load tests on 14 small scale cast-in-situ concrete piles in sandy soils of Caspian Sea southern coasts, load-settlement curves and the end bearing capacity of piles were investigated. Then, the values of settlements and end bearing capacities of piles obtained in this study were compared with the results of other methods and finally, the depth of penetration of the piles to fully mobilize the ultimate base resistance of the soil layer was estimated.}, Keywords = {Cast-in-situ concrete piles,End bearing capacity,Pile settlement,Sandy Soil,Axial compression pile load test}, volume = {15}, Number = {2}, pages = {65-78}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7382-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7382-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Ayati, Bit}, title = {Investigation of kinetic and intermediate products of acid orange7 removal by hybrid ozonation/photocatalytic processes}, abstract ={Most of dyes used in production processes caused serious environmental pollution when discharged into the environment. Azo dyes are the most used synthetic compounds in the textile, food, leather and cosmetic industries. Due to their toxicity and hard degradation, these kinds of compounds are classified as environmental hazardous materials that have to be treated before discharging to the environment. Acid orange 7 (AO7) is one of azo dyes that is resistant to aerobic degradation and under anaerobic condition is reduced to potential carcinogenic aromatic amines. Different physical methods such as adsorption, ultrafiltration, reverse osmosis, coagulation and electro coagulation are widely used for efficient dye removal but they just transport contaminants from water to sludge and generate secondary wastes which need more treatment. Advanced oxidation processes (AOPs) are suitable to mineralize dye wastewater. They are almost characterized by the efficient production of hydroxyl radicals. Radicals are highly reactive oxidant. Ozonation and photocatalytic treatment are often applied for decolorization of dye wastewaters. It is reported that ozone is an effective agent for reducing the color of wastewater especially azo dyes. TiO2 photocatalytic process is safe and does not require expensive oxidants, against ozonation. This process classified as an AOP method and can be carried out at mild temperature and pressure. The purpose of this study was to investigate hybrid photocatalytic and ozonation processes. Therefore, according to debarment of light penetration in dye wastewater, decoloration ability of ozone was used for improving photocatalytic process efficiency in a hybrid process. The effect of pH, dye and nano catalyst concentration, irradiation source power and ozone injection rate were investigated on removal efficiency in this process. Dye removal efficiencies decreased with increase in dye concentration and decrease in pH, ozone injection rate, catalyst concentration and irradiation source power. Optimum conditions of the process was occurred in pH of 9, UV-A lamp of 120 W, and nano material concentration of 128 mg/L with 50 mg/L of dye concentration and 20 mg/min of ozone injected (with 1 bar pressure and 1 lit/min of gas flow). In these conditions, dye removal was completed after 65 minutes. The result confirm the cleavage of the azo bonds, benzene and naphthalene rings as a result of treatment. The intensities of the absorbance peak at 485nm decrease rather fast than 230 and 310 nm. This shows that faster degradation of azo band in comparison with benzene and naphthalene rings. GC-MS analysis was performed to identify the intermediate products of process. According to GC-Mass test, 5-amino-1-naphthol, 1-naphthol and benzene compound (phenol, aniline and phthalic acid) were in decolorized solution. These compounds concentration increased in the first hour and then decreased. 3 and 7 hour were needed to reach optimum condition for removing naphthalene and benzene compounds, respectively. Reaction was followed by first order kinetic and was fitted to langmuir–hinshelwood model in optimum condition in all cases. First order reaction rate of decoloration (K) decreased with increase in dye concentration and decrease in pH, catalyst concentration and irradiation source power.}, Keywords = {Azo,dye removal,Kinetic,by-products}, volume = {15}, Number = {2}, pages = {79-89}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-6520-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-6520-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {ghadak, paym}, title = {Application of reverse osmosis membraine for mercury removal from refinery wastewater}, abstract ={Oil and gas processing activities is causes excess water consumption, which leads to excessive production of wastewater. This produced waste water contains mineral and biological compounds which can contaminate water and ground water. Vast amount of this industries’ produced wastewater in Oil-rich countries which mostly are arid countries, lead them to find more effective methods for water reuse as a new water resources. One of the most important water pollutant are heavy metals, so investigator are believe that heavy metals toxicity into environment is more than which disperse from radioactive toxicity to ground water and seas. Various physical, chemical and biological methods of waste water treatment are applied in refining and petrochemical industries. considerable amount af mercury with different operational units’ wastewater is discharge to environment from refinery units. Since mercury is not biodegradable and tend to accumulate in living organisms, we must be able to control it by using effective methods. Application of membrane filtration is new method for water and wastewater treatment industry. In this research, by application of case study on one of the nation’s gas refineries, reverse osmosis membrane system performance under different operating conditions, was studied. For this purpose effects of variable parameters, namely operating pressure (5, 7, 9 and 11 bar), pH (3, 6, 9, 11) and mercury concentration (1, 2, 4, 8 and 12 mg/l) on removal performance were studied. Considering removal performance of mercury, COD, TDS, EC, Turbidity and also membrane flow rate, optimum operating condition was obtained. Base on the results, reverse osmosis membrane performance is efficient in optimum parameters’ value, namely 7 bar pressure and pH=9 from permeate water quality and economical aspects. by increasing system pressure a significant decline in mercury and COD removal efficiency was observed. removal efficiency of mercury, COD, and TDS in 7 bar pressure condition was 91.35%, 99.55%, and 94.89% respectively and also permeat flowrate was acceptable, so 7 bar was found as optimum pressure. On the next stage af investigation, although by increasing wastewater sampel’s pH, a considerable increase in mercury and COD removal efficiency was observed, it cause a dramatic rise in TDS and turbidity in feed wastewater and also in permeate stream. More over high value of pH, namely pH=11 can make system prone to fouling. So pH=9 was choosen as a optimum pH. Finally reverse osmosis membrane performance in encountering with possible shocks and high concentration of influent mercury was investigated. Although results shows a significant decrease in membrane removal efficiency in encountering with high influent mercury concentration, reverse osmosis membrane system efficiency in mercury removal is acceptable in encountering conventional mercury concentration of refineries. reverse osmosis membrane performance is efficient in optimum parameters’ value namely 7 bar pressure and pH=9, so removal efficiency of mercury,COD, and TDS was 97.5%, 99.755 and 93.29% respectively.}, Keywords = {Mercury,Refinery wastewater,membrane filtration,Reverse osmosis}, volume = {15}, Number = {2}, pages = {91-101}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-6891-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-6891-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Experimental Study of Combined models of berm, side slope and slot in decreasing the bed erosion around bridge piers}, abstract ={In this paper, the experimental results of 12 combined bridge pier models to reduce the maximum scour depth in clear-water condition have been presented. Experimental models are classified in four groups, namely: 1) berm and semi-conical piers, 2) combination of berm and semi-conical piers with variable diameter in the bed, 3) combination of berm and semi-conical piers with constant diameter in the bed, and 4) combination of third group with trapezoidal centered slot. In this regard, 12 laboratory piers models have been examined in a flume of 12m long, 1m wide and 0.85m deep. At first, for the reference cylindrical pier model, the experiments have been carried out for 48 hours and it has been shown that the time of 24~35 hours is usually sufficient to reach the equilibrium condition. At the beginning of the each test, the time interval to get the scour depth was chosen very short (e.g. every ten minutes), but this interval increased gradually with continuing the experiment so that at the end of experiment it was 1 hrs. Firstly, significant decrease (up to 46 percent) in scour depth was observed for berm pier with respect to the cylindrical reference pier. This reduction was also observed for semi-conical pier, however, it was much lower than that of the berm pier. For the second group, the semi-conical combined pier with side slope angle of 2 degrees of model piers had the least bed erosion in comparison to that of the other two groups. For this model, the width of the berm is larger and diameter of the pier is smaller in bed level. Scour depth is then increased in comparison to that of the berm pier model in this group but it is decreased when compared with that of the cylindrical reference pier. Very slight decrease has been observed in the scour depth for the third group model piers by keeping the pier diameter constant in the bed. Hence, increasing the pier diameter in the bed level has intensified the bed erosion in the semi-conical combined piers. Finally, applying slot in the combined piers of third group was ineffective in increasing the protective role of model piers for the fourth group. Therefore, it can be concluded that the effect of berm model pier in decreasing scour depth was much more than the other countermeasures for the piers and their combinations. Then it was found that the different countermeasures for the bed erosion could not have positive influence on decreasing the scour depth for all the cases and a combined model of them may be less effective against scour process than a single countermeasure. The comparison of maximum scour depth has been conducted for all models with relative to those of the cylindrical reference and berm piers.}, Keywords = {Bridge pier,Combined Model,Berm,Semi Conical Pier,slot}, volume = {15}, Number = {2}, pages = {103-116}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7879-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7879-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {KaramiMohammadi, Reza and Shahryari, Homayoo}, title = {Generation Artificial Accelerograms to Estimate the Incremental Dynamic Analysis Parameters}, abstract ={These days the accurate estimation of seismic demand and capacity of structures are truly significant in the field of performance based earthquake engineering. Several methods exist to determine these parameters such as non-linear time history analysis and Incremental dynamic analysis (IDA). Because the history of seismic accelerogram records refers to the current century, in some areas there still exists no appropriate seismic record to perform the analyses; therefore in these cases we need to generate artificial accelerograms. In this paper a new combinational method is introduced to generate far-field artificial accelerograms using artificial neural network and wavelet packet transform (WPT) methods. In this method according to the geoseismic characteristics of the site and non-linear characteristics of the equivalent single degree of freedom (SDOF) system, several artificial accelerograms are generated. In order to consider the non-linear parameters to generate the accelerograms, IDA method is used. The values of intensity measure (IM) for all IDA curves are determined at specific levels of damage measure (DM) and are considered as the input data of the multilayer feed forward (MLFF) neural network. Accelerograms which are selected according to the geoseismic characteristics of the site are changed to standard forms and then decomposed using wavelet packet transform. The effective wavelet packet coefficients are selected according to an appropriate desired effective variance ratio of wavelet packet coefficient. Then, effective coefficient of each packet is considered as the output of a neural network. In order to enhance the efficiency of the network, principal components analysis (PCA) is used to reduce the number of the input data dimensions. In this paper neural network is trained by backpropagation algorithm as repetitive. After training the MLFF neural network, we should test the network for accelerograms not included in the training set. For this purpose we should use the IDA curve of each accelerogram out of the training set as the input of the neural network to generate the effective WPT coefficients. When a neural network is trained properly, we can now generate artificial accelerograms using a 50% fractile IDA curve as the input of the neural network. Adding a Gaussian random number to the output of each neuron in the neural network layers, we are able to generate several accelerograms according to 50% fractile IDA curve. In order to improve the condition of generated accelerograms according to 50% fractile IDA curve, a correction factor is used repeatedly for detail coefficients of discrete wavelet transform in jth level of generated accelerogram. Finally a SDOF system with perfectly elasto-plastic initial loading curve is used to show the efficiency of the proposed method to generate artificial accelerogram. The accuracy of this method depends on the accuracy of the trained neural networks. If the neural networks are trained appropriately with IDA curve, the generated accelerogram can estimate the IDA parameters of the SDOF system more properly. Also it is shown that suggested method can generate artificial accelerograms with frequency content almost close to the initial earthquake records.}, Keywords = {Artificial Accelerogram Generation,Wavelet Packet Transform,artificial neural networks,Incremental dynamic analysis}, volume = {15}, Number = {2}, pages = {117-126}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7165-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7165-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Pressure Flushing with Expanding Bottom Outlet Channel within Dam Reservoir}, abstract ={Currently, large dams in the world, due to high amount of sediments in the reservoir, especially around the intake, have operational problems. One of the solutions for this problem is pressure flushing which is an efficient method for extracting the accumulated sediments behind the dams, where, the valves and turbines are placed over there. In this type of flushing, previously deposited sediments are removed by opening the bottom outlets. Sediment is scoured and a funnel shaped crater is created in the vicinity of the bottom outlet opening. Amount of the flushed sediments depend on many parameters such as water depth on the bottom outlets, discharge released through bottom outlets, size of the outlets, geometry of the reservoir, size and kind of the deposited sediments in the reservoir. But the extent of flushing impact range is limited. On the other hand, since in this method, the waste of water in the reservoir is relatively low; therefore, an appropriate solution for increasing the efficiency of the pressure flushing process, would be able to increase the dam’s lifetime with minimal amount of water waste. In laboratory experiments carried out in this study, the effect of expansion of bottom outlet channel within the reservoir is investigated on the volume and dimensions of the flushing cone. In order to achieve the objective of this study, experiments done by means of a physical model with length 7.1 m, wide 1.4 m and height of 1.5 m. Experiments performed with three bottom outlet channel lengths 10, 20 and 30 cm, three water heights 47.5, 55 and 64.5 cm over center of outlet and three discharge flows equal to 1, 2 and 3 (l/s) for each height. Preliminary results showed that, expansion of bottom outlet channel within the reservoir has positive and tangible effects on the size of the flushing cone. As, with the expansion of bottom outlet channel within the reservoir, new hydraulic conditions are introduced, which affects the mechanism of flushing and by increase in the length of outlet channel, dimension of flushing cone increases. But the rate of increase in dimensions decreases with increment in expansion amount. So the relative amount of bottom outlet channel expansion for 0.5, 1 and 1.5 times height of the sediment in the reservoir, leads to increase in flushing cone volume for average amount of 50, 74 and 96% compared to the case with the no developed bottom outlet channel. according to the experimental data, non-dimensional equations are derived for estimation of the flushing cone size. These equations show high regression coefficients and provide good estimations. Also the results indicate that, In the higher discharges of flow, effect of the expansion size of bottom outlet channel on the amount of the sediment discharged is high.}, Keywords = {"Pressure flushing","Physical model","Expansion of bottom outlet channel ",Flushing impact range","Dimensional analysis"}, volume = {15}, Number = {2}, pages = {127-136}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-6942-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-6942-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {khatibi, mehdi and Soltani, Amin and RaeesiEstabragh, Ali}, title = {Experimental and statistical assessment of expansive soil treatment using artificial fiber and chemical stabilizer}, abstract ={Expansive soils are found in many parts of the world particularly in arid and semi-arid regions. They are considered a worldwide problem as they cause extensive damage to civil engineering structures. As a result, a clear understanding of the behavior of such soils is required for the effective design of structures and infrastructures on these soils. Researchers have demonstrated various methods to reduce expansive soils swelling potential, with one being soil treatment. In this paper an experimental program was developed to study the treatment of an expansive soil using mechanical and chemical techniques. Two different types of artificial fiber consisting of polyethylene (bar shaped) with a diameter of 0.3mm and polypropylene (tape shaped) with a width of 3mm were used in order to randomly reinforce soil samples with various fiber contents of 0.5%, 1% and 1.5%; and fiber lengths of 10, 20 and 30mm. Chemical treatment was carried on using lime and cement as soil stabilizers with various percentages of 5%, 8% and 10%; for curing times of immediate, 3 and 7 days. Uniform and repeatable moist-compacted soil samples were prepared by static compaction at a chosen moisture content and dry density less than the optimum water content and maximum dry density from standard proctor compaction tests. Free swelling and swelling pressure tests were conducted using a one-dimensional oedometer apparatus. In addition multiple regression equations with 3 and 2 independent variables were developed based on experimental results. The proposed multiple regression equations present an understanding of the variation of free swelling and swelling pressure as a function of swelling time, fiber or chemical stabilizer content and fiber aspect ratio (fiber length divided to fibers diameter or width) or curing time for various values. Experimental results and statistical analysis indicated that soil treatment with artificial fibers and chemical stabilizers can indeed reduce swelling potential in expansive soils. Reduction of free swelling and swelling pressure in samples randomly reinforced with artificial fiber was seen to be dependent on fiber content, fiber length and fiber shape, where tape shaped fibers showed more reduction in free swelling and swelling pressure thus being more effective compare to bar shaped fibers. Furthermore reduction of free swelling in samples treated with chemical stabilizers were seen to be a function of percentage of chemical stabilizer and curing time with cement showing to be more effective compare to lime. In addition chemical stabilizers proved to be more effective in reducing soils swelling potential compare to artificial fibers. The suggested regression equations can predict and estimate the free swelling curve, final free swelling and swelling pressure for various swelling time, fiber or chemical stabilizer content and fiber aspect ratio or chemical stabilizer curing time with accuracy and a high degree of agreement between experimental and predicted values. Also, the regression equations can aid the performance of a sensitivity analysis which indicates the importance of each independent variable (fiber or chemical stabilizer content, fiber aspect ratio or chemical stabilizer curing time) in estimating final free swelling and swelling pressure.}, Keywords = {Expansive soils,soil treatment,free swelling,swelling pressure,multiple regression}, volume = {15}, Number = {2}, pages = {137-147}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7357-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7357-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {sedaghat, arman and sodagari, jav}, title = {The effect of concrete additives on physical properties of soil stabilized with lime}, abstract ={Sand and gravel materials are commonly use for structure layers of roads. These materials are providing from riverbeds and mines, which are usually far from the operation site area. While the process involves manipulation of riverbeds and mines it also has a significant cost, most of it in extraction, transportation, Gradation correction, fuel and machinery.Researches done in different countries are showing that in cases soil is in good quality, stabilized mixture of soil can be used instead of sand and gravel. These can reults a signifactnt amount of money saving by providing soil from near the road and eliminating the process of Gradation correction. However, there are resistance and inflammatory parameters of fine soils, which play an important, usually problematic, role in structure buildings. The abundance of fine-grained clayey soils in the country, have created serious problems in construction projects. One of the ways to modify or improve the properties of these soils is stabilizing. Lime as a stabilizer for fine-grained soils is famous. In this thesis, the effect of four chemical additives on the CBR strength of soil stabilized with lime is studied. In addition, effect of additives on properties such as swelling, water absorption and density of soil stabilized with lime is studied. These additives with names "Panplast R", "RB - PC 386", "RB - PC 375" and "Planicrete SP" as a lubricant and concrete superplasticizer have the desired effect on the chemical and physical properties of concrete. Moreover, the Cementation act of stabilized soil with lime is like cement. In this study, the effects of those additives on lime-stabilized soil are studied. First four different combinations of soil and different percentages of lime made. The results obtained optimized percentage of lime. Then optimized percentage of lime and different percentages of additives used to build the different samples. In order to avoid faults and testing errors, each combination made by two samples. All desired results were presente as mean values obtained from two samples. Total of 49 samples were built and tested. Due to determine the effect of curing time of each combination, two sample with 7-day curing time and two other with 14-day curing time are made. In order to preserve the moisture in the samples during the curing time they were stored in sealed thick nylon bags. After curing time for each sample for 96 hours at constant temperature water baths were maintaine to monitor inflation and the water absorption. After time the CBR test done. Finally, the Additives "Panplast-R" and "RB-PC 375" had a favorable impact on listed properties, so that the CBR result was 90% and 99%, the "RB-PC 386" was almost effectless, and the "Planicrete-SP" has shown Negative impact on the properties of interest. so that the CBR result was 65%.}, Keywords = {CBR,soil,lime,Stabilization,Additives,CBR}, volume = {15}, Number = {2}, pages = {149-160}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3146-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3146-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Goodarzi, Amir rez}, title = {Effect of iron industry slags on the geotechnical properties and mineralogy characteristics of expansive smectite clay}, abstract ={Expansive clayey soils, which are predominantly distributed throughout the world, have complicated behavior. Heaving and settling in these soils may pose considerable problems and severe damage to structures that come into their contact or constructed out of them and consequent distress to people if not adequately taken care of. Granulated blast furnace slag (GBFS) and basic oxygen furnace slag (BOS) are two types of by-product materials resulting from the manufacture of iron that are produced in large amount throughout the world. The proper disposal of such byproducts is one of the major issues for environmentalists since leaving them to the environment directly may cause health problems. Hence, the aim of this study is to investigate the potential use and effectiveness of expansive soils treatment using GBFS and BOS. To achieve the objectives, the admixtures were added to the clay smectite samples in proportion of 0 to 30% by weight and tests of the pH value, electrical conductivity (EC) measurement, Atterberg limits, swelling, unconfined compression strength (UCS) and X-ray diffraction analysis were performed on those samples at different curing period (i.e. 1, 3, 7, 14, 28, 45 and 90 days). Lime as a conventional additive was also used to evaluate the performance of GBFS and BOS. The results reveal that in the limited curing condition (i.e. less than 3 days) and with the addition of 20% slag, the swelling could be eliminated mainly due to the short term reactions (i.e. cation exchange and osmotic pressure increasing). On the other hand, based on the X-ray graphs it was found that with appropriate curing (more than 7 days) and due to the growth of the cementation compounds such as calcium silicate hydrates (CSH) and calcium aluminate hydrates (CAH), especially in samples containing BOS, the needed slag to control heave potential will be declined up to 4 times. The presented results indicate that highly expansive clayey soils can be stabilized satisfactorily by lime and following adequate curing due to development of the pozzolanic reaction. Beside, with a further increase in the lime content, the pozzolanic activity can not continuously take place and the excessive addition of lime caused a reduction in the mechanical capacity. On the other hand, the samples containing slag show a progressive increase in the strength with increasing the additive content and could overcome the difficulties associated with the use of lime. For example, the USC of smectite sample with 30% BOS and after 90 days of curing was almost 12 times higher than the untreated sample. However, in the presences of GBFS due to lower solubility and limitation of pozolanic activity the lower change was observed. The The macro and micro level experiments results of this study indicate that the utilization of iron and steel slags especially basic oxygen furnace slag (BOF) is a good alternative for lime stabilization which reduces the cost of soil treatment project and help the management of these byproducts.}, Keywords = {GBFS,BOS,Smectite,GBFS,BOS,Stabilization,Swelling potential}, volume = {15}, Number = {2}, pages = {160-170}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7597-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7597-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {tavakoli, keiv}, title = {A numerical study on site location of one vane in a U shape channel bend with lateral intake with respect to lateral intake edges}, abstract ={Submerged vanes are small flow training structures, designed to modify the near bed flow pattern and redistribution of flow and sediment transport whit in channel cross section. The vanes generating secondary circulation in the flow. The flow field around lateral intake located in the outer bank of channel bends and the interaction between this flow field and secondary flow due to submerged vanes in completely three dimensional and complex. The purpose of this paper is determination of appropriate location of the one submerged vane with respect to the downstream and upstream edge of the lateral intake in a U shape channel bend and choice the best angle of vane for reduce the sediment entry to the lateral intake. In this order we use the Fluent software to numerical simulation of 3D flow pattern around the one vane that locating in front of downstream edge of a lateral intake in a U shape channel bend. The results of numerical were verified with the existing experimental data. Comparison of the predicted x velocity and y velocity field with laboratory measurements indicates that the model capture experimental trend with reasonable accuracy. Computations are performed using Reynolds Stress Model. After model verification, the effect of different position of the vane with respect to downstream of intake (the first, middle and end point of vane is in front of downstream edge of intake) and upstream edge of intake (the first, middle and end point of vane is in front of upstream edge) and effect of different angle of vane (15, 17, 20, 25, 30 degree) on flow pattern and shear stress pattern of bed is considered. The appropriate position and angle of the vane has been selected by effect of the vane on area of high shear stress zone and area of low velocity contour around the vane and reduction of dimension of saddle point near the downstream edge of lateral intake and situation of stream line around the vane and in front of the intake at the bottom of the channel. The results show the best position of vane with respect to downstream edge of lateral intake is the case that the first point of vane is in front of downstream edge of intake and the best position of vane with respect to upstream edge of intake is the case that the end point of vane is in front of upstream edge of intake. Also the results show that the appropriate value for angle of attack of the vane at downstream edge of intake (the first point of vane is in front of downstream edge of intake) is about 20-25 degree and optimum value for angle of attack of the vane at upstream edge of intake (the end point of vane is in front of upstream edge of intake ) is about 17-20 degree.}, Keywords = {flow field,Numerical simulation,one submerged vane,180° bend,lateral intake}, volume = {15}, Number = {2}, pages = {171-181}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-9388-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-9388-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {NourbakhshDehkordi, Ali Asghar}, title = {The effect of Performance Levels on the Material Quantity of Steel Moment Resisting Dual Systems Utilizing Nonlinear Static and Dynamic Analysis}, abstract ={}, Keywords = {}, volume = {15}, Number = {2}, pages = {183-197}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7091-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7091-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Anis-hoseini1, Masoud and Zakermoshfegh, Mohamm}, title = {Comparison between phase space-based local chaotic models for riverflow forecasting}, abstract ={Generally, The dynamics which is observed in time series of a hydrologic system variable have been considered as complex and random behavior. During last decades, using various artificial intelligence approaches such as chaos theory to analyze and prediction of hydrologic systems have been increased. In chaos theory viewpoint, complexity and random-like behavior of a system can be resulted from a simple and hidden determinism. Therefore, systems such as dominant hydrologic system which controls flow in a river can have this kind of determinism. If such determinism is existed, can be observed through system phase space, which can be reconstructed using a time series by lags method. Based on such a pattern that formed in reconstructed phase space, various prediction models can be used to forecast system behavior in future. Hence, chaotic behavior of the Kashkan river daily discharge time series have been studied using False Nearest Neighbors and Lyapunov Exponent methods which evaluated fractal attractor and sensitivity to initial condition as two major characteristics of a chaotic system. Average Mutual Information method was used to determine optimal delay time in phase space reconstruction by delay method. In this paper, it has been suggested to use first global minimum of mutual information function as standard to select optimal delay time. According to the results which have been obtain by these methods, chaotic behavior in daily runoff time series of the Kashkan river have been observed. In False Nearest Neighbors method, the percent of false neighbors have been significantly decreased due to rising embedding dimension of phase space, which have been shown the existence of a fractal attractor in system phase space. In lyapunov exponent method, the sensitivity to initial condition has been evaluated through reconstructed phase space and positive lyapunov exponent has been obtained. Hence, chaos theory-based models can be used to forecast daily runoff in this system. Various local models were used to make prediction based on reconstructed phase space and the results have been compared. Local Average and Local Polynomial was among local models that employed in this study. In addition, as a new hybrid approach, Multi Layer Prespetron Artificial Neural Networks have been used to local modeling based on phase space. All prediction results show appropriate quality of local prediction models in base of attractor pattern in phase space of dominant system of the Kashkan river flow. The accuracy which have been resulted from local hybrid model with Artificial Neural Networks, have been not shown significant difference with other current local models such as Local Average and Local Polynomial prediction methods. However, the Local Polynomial model has been shown better forecasting accuracy in compare with other methods. Totally, Local chaotic methods are suggested to make daily prediction of runoff in the Kashkan river.}, Keywords = {Chaos Theory,Phase Space,Local Models,artificial neural networks,The Kashkan River}, volume = {15}, Number = {3}, pages = {13-24}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4895-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4895-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Akrami, Vahid and Erfani, Saee}, title = {A Numerical Investigation on the Appropriate Corner Radii of Beam Web Opening in Steel Moment Frames}, abstract ={Web openings may be provided in structural floor beams for different purposes. The corner radii of web openings can have a significant effect on stress and strain concentrations around the opening. AISC's design guide for steel and composite beams with web openings states that web openings are not recommended for members subjected to significant high cycle-low stress or low cycle-high stress fatigue loading even if a rational corner radii is provided for web openings. This is because, at the time the specification was written, there were only limited references available to the committee which indicates the need for further studies in this field. In this paper, effect of opening corner radii on cyclic behavior of steel moment connections with Reduced Web Beam Section (RWBS) is investigated using finite element analysis. For this purpose, a T-shaped moment connection (without web opening) which has been tested under cyclic loading by another author is used as the reference model. To see effect of opening corner radii, the reference model is considered with square and rectangular web openings of different corner radii. Fracture initiation in models is simulated using Cyclic Void Growth Model (CVGM) which is based on micro-void growth and coalescence. According to this model, fracture under cyclic loading is predicted to occur when the void size exceeds the critical value. Based on the results, for both square and rectangular openings the maximum equivalent plastic strain and fracture index at the opening corners will decrease as the opening corner radii increase. For openings with small corner radii the fracture index at corners will be very high. This is in accordance with recommendation of ASCE 23-97 which indicates that these configurations should not be used in real practice. However, it should be noticed that in the case of rectangular opening the damage index at the corners may be greater than unity even if ASCE 23-97 limitations are met. This means that if it is intended to achieve high rotation capacity at RWBS connections, ASCE 23-97 requirement about minimum corner radii may be non-conservative. As another result, as the opening corner radii increase local buckling around the web opening occurs at higher rotations. In addition to the local effects, the choice of opening corner radii can also affect the global behavior of RWBS connections. In the case of rectangular perforation, as the opening corner radii increase the load carrying and rotation capacity of connection increase too. This is because in these models, the weakening area prevents welds from failure and fracture occurs in the opening corners. As a result, as the opening corner radii increase the fracture index at opening corners decreases and hence the connection can undergo higher rotation capacities. This is not true for square perforation where fracture occurs at connection welds and the connection rotation capacity makes no change as the opening corner radii increase. As a general recommendation it can be said that web openings with the largest corner radii (elongated circular holes) is the best case for perforated steel connections.}, Keywords = {Moment frame,Beam Web Opening,Cyclic Void Growth Model,Low Cycle Fatigue}, volume = {15}, Number = {3}, pages = {14-25}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-5595-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-5595-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Simulation of Dam break flows using ‌ Weakly compressible moving-particle semi-implicit method}, abstract ={Simulation of free surface flows using Weakly compressible moving-particle semi-implicit method Mesh-free particle (Lagrangian) methods, such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH), are the newest methods in computational fluid dynamics, which have been applied in flow problems with large deformations and inconsistency. The aim of ths research was to develop and improve the simulation of free surface flows, using the new method of weakly compressible MPS (WC-MPS). In the MPS method, pressure is determined by solving Poisson equation. This equation is solved implicitly, which needs too much computer time. In the present research, the WC-MPS method is used to calculate pressure. In this method, as in SPH method, the state equation is used. This equation is solved explicitly, which does not occupy too much computer time. To evaluate the proposed method, the famous applied flow problem of dam break is analyzed. The program is written in C language and validations are performed for this code. To compare the Lagrangian approach with Eulerian approach, dam break is modeled by using FLOW-3D software too. The results of modeling approaches and physical models showed that both approaches have acceptable accuracy in modeling the free surface flow, but the accuracy of Lagrangian approach, especially the WC-MPS, is more than Eulerian approach. The proposed methos had some pressure oscillations, which were analyzed thereafter. Simulation of free surface flows using Weakly compressible moving-particle semi-implicit method Mesh-free particle (Lagrangian) methods, such as moving-particle semi-implicit (MPS) and smoothed particle hydrodynamics (SPH), are the newest methods in computational fluid dynamics, which have been applied in flow problems with large deformations and inconsistency. The aim of ths research was to develop and improve the simulation of free surface flows, using the new method of weakly compressible MPS (WC-MPS). In the MPS method, pressure is determined by solving Poisson equation. This equation is solved implicitly, which needs too much computer time. In the present research, the WC-MPS method is used to calculate pressure. In this method, as in SPH method, the state equation is used. This equation is solved explicitly, which does not occupy too much computer time. To evaluate the proposed method, the famous applied flow problem of dam break is analyzed. The program is written in C language and validations are performed for this code. To compare the Lagrangian approach with Eulerian approach, dam break is modeled by using FLOW-3D software too. The results of modeling approaches and physical models showed that both approaches have acceptable accuracy in modeling the free surface flow, but the accuracy of Lagrangian approach, especially the WC-MPS, is more than Eulerian approach. The proposed methos had some pressure oscillations, which were analyzed thereafter. Simulation of free surface flows using Weakly compressible moving-particle semi-implicit method}, Keywords = {Lagrangian Approach ",Eulerian Approach ",moving-particle semi-implicit method ",Free Surface Flow ",Dam Break}, volume = {15}, Number = {3}, pages = {25-37}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3492-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3492-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Jafarian, Yaser}, title = {Laboratory study on cyclic behaviour and pore water pressure generation of Boushehr calcareous sand}, abstract ={As a disastrous cyclic response of soils, liquefaction commonly takes place in the saturated soils overlaid in seismic regions. Earthquake excitation in loose deposits enforces the soil particles to displace towards a more compacted state. This tendency causes generation of excessive pore water pressure when drainage is prevented or its rate is less than the generation rate. Comprehensive laboratory investigations have been carried out so far in order to capture cyclic behavior of silicate soils. However, cyclic behaviour and liquefaction resistance of calcareous soils has not been fully recognized as well. Calcareous soils evolve from biological resources due to the physiochemical process of marine organisms. Such soils have excessive crushing capability; and thus, their mechanical behaviour is expected to be different than that of terrestrial soil deposits. The current study presents results of several undrained cyclic tests on isotropically and anisotropically consolidated samples of Boushehr calcareous sand. The tests were conducted via a triaxial machine in strain-controlled condition. Bulk samples of the sand were gathered from the coast of Boushehr city located in the southwest of Iran, north bank of Persian Gulf. The sand samples were reconstituted with dry deposition method of sample preparation under various initial relative densities and confining pressures. The consolidation phase of the tests was performed in drained condition for either isotropically or anisotropically consolidated samples. The cyclic loading phase of the tests was conducted by multi-stage procedure in order to recognize soil potential for excess pore water pressure generation. Various levels of controlled cyclic axial strains were applied on the sample in each stage of the cyclic loading phase and the samples were allowed to be drained at the end of each stage. The results are presented in terms of threshold shear strain and dissipated strain energy concept. Comparison is made between the tests results and those reported by the previous studies. The results revealed that liquefaction resistance of the studied sand increases with increasing initial relative density and effective confining pressure whereas the samples with high initial effective stress never liquefied even after one hundred cycles of loading. Relationships between excess pore water pressure and the normalized number of cycles as well as the normalized dissipated strain energy are studied and compared with the relationships presented by the previous researchers for silicate sands. According to the results, such relationships are strongly affected by type of cyclic loading i.e. strain or stress-controlled when excess pore water pressure is correlated to the normalized number of cycles. In fact, evaluation of excess pore pressure is more reasonable to be done with the normalized strain energy in order to minimize the influence of loading type. The threshold shear strain for the studied sand was found to be 0.015% which is comparable with this value for silicate sands.}, Keywords = {Liquefaction,Cyclic Triaxial,Calcareous Sand,Threshold shear strain}, volume = {15}, Number = {3}, pages = {37-50}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2581-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2581-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Khalilian, Marzieh}, title = {Angle Shear Connectors Capacity}, abstract ={The steel-concrete composite beams are increasingly used in bridge and building construction in recent years. In this system, a shear connection between steel and concrete should be provided to effectively transfer the shear forces and to make the two materials act as a single unit. The mechanical shear connectors provide this means. They are the essential component of any composite beam system. Many studies have been performed on shear connectors and many different steel shapes have been suggested for connectors. The steel studs and channels are the most popular code accepted connectors. However, economic considerations continue to motivate the development of new products. Present knowledge of the capacity and behavior of the shear connectors are mainly limited to the data obtained from the push-out or beam tests with the latter being more expensive and accurate. Therefore, analytical procedures that can predict the nonlinear response and the capacity of the composite beams are necessary when the experimental resources are not available. In this study a three-dimensional FE model using the computer code ABAQUS is developed to simulate the push-out tests of angle shear connectors. The main objective of this study is to investigate the behavior and to find the ultimate strength of angle shear connectors in a solid slab. In order to obtain dependable results from the FE analysis, all components of the connection should be correctly modeled. There are four parts in this model: concrete slab, shear connector, steel beam and the rigid base. Because of symmetry, only a quarter of the push-out specimen is modeled.Nonlinear material and large displacement capability are employed. The load-slip behavior, capacity and maximum displacement at failure obtained from the finite element model were validated against available push-out test results. The results show the FEM can predict the capacity of the angle shear connectors with adequate precision. Using the FE model, a parametric study was conducted to evaluate the effect of variations in angle dimensions and concrete strength. The parametric study reveals that: • The capacity of angle connector increases with increasing concrete strength. • The Flange width has no measurable effect on angle connector capacity and its behavior. • The height of the angle has no considerable effect on load-displacement behavior of the connector. • The capacity of angle connector increases whereas the maximum slip decreases with increasing angle thickness. • The stress value is not constant along the angle length and it decreases from the center of the angle towards the edges. The shorter the length of the connector, the lower the stress change. Therefore, long angle shear connectors become ineffective. An equation is suggested to predict the angle effective length. Finally, an equation is proposed to predict the ultimate shear strength of the angle connectors.}, Keywords = {Shear connectors,Composite beams,Angles,finite element method}, volume = {15}, Number = {3}, pages = {51-62}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7717-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7717-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Ganjidoust, Hossei}, title = {Evaluation of kinetic models in water salinity reduction by phytoremediation method with three halophyte plants}, abstract ={Water scarcity has led to the search for alternative water resources. One solution is the recycling of wastewater for irrigation. Wastewater treatment is often based on biological systems such as activated sludge or other engineered units in urban areas. In rural areas, low-cost, environmentally-friendly alternative treatments such as constructed wetlands (CW), are more common. CWs are man-made planted systems that utilize natural processes to improve water quality for human benefit. Salinity in treated wastewater is often increased, especially in arid and semi-arid areas. Phytoremediation can be used to remove much of this problem. Phytoremediation is the use of plants for remedying water and soil pollution. This approach is based on plants that are especially tolerant to salt environments. Around 1% of all plant species are halophytes that can complete their life cycle in relatively high saline environments, as much as 200 mM NaCl or more. In the current study, we addressed the problem of soilsalinization due to the use of treated wastewater that is often more saline than fresh water, especially in desert environments. We aimed at testing the potential to recruit halophyte plants for salt phytoremediation in constructed wetlands. Therefore this study was performed to evaluate the ability of reducing salinity of wastewater by three halophyte plant species such as Frankenia, Atriplex and Festuca. The experiments were performed with different concentrations of saltwater. Reducing the electrical conductivity, salt removal and its uptake rate, the concentration of sodium stored in plant tissues at different levels of salinity, were analyzed. Also by matching the data with Michaelis- Menten and Lineweaver- Burk kinetic models, some results were obtained from each plant. The electrical conductivity decreased with increasing salinity levels in all three species. The highest salt absorption amount in Frankenia was in 4500 µs/cm about 20 percent, in Festuca was in 2600 µs/cm about 17 percent and Atriplex was in 5000 µs/cm about 14 percent. Of course reducing of salt uptake in each plant had its own reason for example; Atriplex plants due to having less compatible with wetland situation, Festuca plants due to facing with salinity stress and Frankenia plants because of salt replenishment faced with yield loss and withered state. Based on these results Frankenia, Festuca and Atriplex plants during the treatment with saline water, had the first order of kinetic equation with a correlation coefficient of respectively 97.7, 95.9 and 97.01, gradually with increasing of salinity these plants had the kinetic equations of 2, 0 and 1 order that as this result, Atriplex plants showed more resistance in salt uptaking. In reduction range also Atriplexand Frankenia had a better performance. The highest conformity of data in Frankenia plant related to Lineweaver- Burk and Atriplex plant related to Michaelis- Menten.}, Keywords = {Frankenia,Festuca,Atriplex,Salinity reduction,Kinetic models}, volume = {15}, Number = {3}, pages = {63-72}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3237-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3237-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {salimi, ali}, title = {Optimizing of spatial allocation for manucipal solid waste collection utilizing GIS}, abstract ={Urbanization and population density in big cities, including gathering materials and urban waste and pollution is followed by increasing environmental pollution so that a much significant percentage of municipal budgets, especially in large cities and municipalities, is spent to collect waste materials. On the hand, the use of computer softwares, in accordance with the daily discriminate increases of environmental issues and management of urban waste are growing. One of the most important case that distinguishes GIS from other systems is the existence of distinct functions in spatial analysis. Including network analysis functions, one feature of network analysis can be finding the shortest path which is the most important applicant in transportation issues. One of the issues of allocation is the issue of allocation of areas where the facilities are used. There are three components in allocation issue: 1. Applicant’s services. (It is the capacity of waste collection depository.) 2.The sever (The machines with the capacity of specific waste collection and road network) 3. The objective function or the cost ( it is the time in this research.) What is at stake in this issue is to set a time to optimize the time to collect the waste. It primarily reduces the time for collection and reduces cost, manpower, distances and environmental pollution. First, the overall research method have been collected and described to optimize the paths, and then a specific methodology will be introduced. material and method Understanding the current situation, it is classified into two general and case studies. In the overall social structure, utilizing the communication network and access routes will be studied and the amount of waste produced, the method of operation and maintenance are studied in order to collect the waste and review the current situation regarding waste management system performance. Major impact on waste producers is dedicated to the study of the area population itself. In this context, it is necessary to determine the scope of the population, family size and population density. Other feature of the area is devoted to the user. User types in this area of study such as the existing users of residential, offices commercial, educational, health, culture and sport should be studied. Each user’s share along with specifications and plans within the designated user is produced at this stage. Like the previous stage, the users are determined according to the block scheme in each block. Communication network is the most important feature of each area of study to determine optimal routes. The information that is needed to be fully collected includes the followings: Names of all studied streets of area, length of the streets, width, bilateral and unilateral streets, and the street traffic if they are unilateral. As already explained, what is important in this research is to optimize the path of collected waste, resulting the time reduction in waste collecting. So to obtain the required time, it is necessary to have the average speed of each vehicle in every street and it should be marked with the relationship between the speed and the time along the way. Speed of vehicles on streets is usually determined by the type of vehicle, street width and traffic levels. It is necessary to obtain this speed through field studies. At nights the traffic is not involved, but the type and speed of vehicles, and the width of streets must be achieved. Eventually we have to determine two speeds for every street, one for days and one for nights and it should be recorded in the Arc GIS information. Now , by modeling the problem with the software, it is described. Initially utilizing GIS a network is formed including roads and reservoir network. The network should be marked whether the streets are bilateral and direction of unilateral streets. The area is divided into N optimal ranges according to the number and capacity of machines. For the allocation options in, Arc GIS service area should be used. Our service areas are reservoir sites. After introducing the service areas which are reservoir sites and have a certain capacity, The problem will be solved. The study area s divided into some optimal ranges according to the number of machines to collect the waste. Now in each divided area, we should choose the most optimal route to collect the waste. This route should be selected and begun from the first reservoir tank to the nearest machines station. Passing all tanks to the final tank, which is close to the transmitting station, Arc GIS chooses the optimal path.}, Keywords = {Urban Waste Collection,Geographical Information System,network analysis,Allocation,Shortest Path}, volume = {15}, Number = {3}, pages = {73-85}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-7287-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-7287-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Mohebkhah, Amin and Sarvecheraghi, Ahm}, title = {Nonlinear Analysis of Unreinforced Masonry Buildings Using Distinct Element Method}, abstract ={The majority of building population in Iran and other developing countries consists of unreinforced masonry buildings and sometimes confined masonry (CM) buildings. In such buildings, masonry shear walls are the main earthquake resistant components. The Iranian seismic standard IS2800 provides some specifications for seismic design and construction of confined and reinforced masonry buildings which all are based on the observed behavior of them during the past destructive earthquakes. In other words, the specifications are merely qualitative. This shows the necessity of assessment of masonry buildings behavior both experimentally and numerically. Despite the extensive numerical studies available in the literature, it seems that the lateral load behavior of masonry buildings cannot be properly investigated by continuum mechanics based methods such as traditional finite element method. As an alternative to the available finite element methods, a distinct/discrete element method (DEM) can be used to investigate the nonlinear lateral load behavior of masonry buildings. Distinct element method has the capability to con-sider large displacements, shear sliding and complete joints openings between bricks as well as automatic detection of new contacts during the analysis process. In this paper a two-dimensional numerical model is developed using distinct element method using the specialized distinct element software UDEC (Itasca, 2004) for the nonlinear static analysis of unreinforced masonry buildings subjected to in-plane monotonic loading. The Univer-sal Distinct Element Code (UDEC) is a 2D program based on the DEM to simulate the behavior of jointed materials subjected to either static or dynamic loading. The developed DEM model is validated using the results of a two-story unreinforced masonry building designed and tested based on the Iranian seismic standard IS2800 regulations at the Building and Housing Research Center (BHRC). Due to low intensity of gravitational normall stresses in conventional masonry buildings, the bricks were built using an elastic material model. In order to develope a DEM micro-model based on interface elements with zero thickness, the size of the bricks was expanded by the mortar thickness in both directions and the elastic properties of the expanded brick were assumed to be the same as that of the real brick. Howevr, For the joints, simulating the characteristics of the mortar, a Mohr–Coulomb slip model was employed. It was found that the model can be used confidently to simulate nonlinear behavior of unreinforced masonry buildings for parametric studies. The Iranian seismic standard IS2800 specifications pertain mainly to the masonry shear walls percentage need in each direction. In other words, the perpendicular shear walls are not taken into account in masonry buildings’ lateral load capacity calculations. However, unreinforced masonry buildings resist lateral loads through box action behavior of all constituent components (i.e. walls, foundation and diaphragms). Therefore, a parametric study was conducted to investigate the contribution of perpendicular masonry shear walls on buildings’ lateral load capacity. Parametric study showed that perpendicular masonry shear walls contribute considerably to the shear capacity of the masonry building.}, Keywords = {Unreinforced masonry building,Distinct Element Method (DEM),Nonlinear analysis,Seismic behavior,Shear capacity}, volume = {15}, Number = {3}, pages = {85-92}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11533-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11533-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Assessment the Effective Parameters on Punching Shear in Slab-Column Connections and Strengthed with FRP}, abstract ={Many flat slab -column frame structures have been built in many parts of the world, since the beginning of the century. The absence of beams makes the form work simple, increase the clear story height, and decreases total building height. However brittle punching failure is a problem that unnecessarily limits the widespread use of flat plates in active earthquake zones. Many slab -column connections in flat plate structures were damaged and failed in punching shear after the 1985 Mexico City earthquake, the 1989 Loma Prieta earthquake, and the 1994 Northridge earthquake. These shows that slab–column connections are prone to punching shear failure when lateral forces, due to earthquake loading, cause substantial unbalanced moments to be transferred from the slab to the column. Slabs with low or medium reinforcement ratios tend to fail in flexure rather than in punching shear. For slabs with reinforcement ratios of 1% and more, the mode of failure tends to be the punching shear type of failure. Fiber-Reinforced Polymers (FRPs) have gained increasing popularity in retrofit of reinforced concrete members in the last two decades. Using FRP materials to enhance slabs in flexure is very desirable from the application point of view due to the ease of handling and installing. FRP material, unlike steel, are not subject to either corrosion or rust in the long term. There is limited amount of research available on srengthening of slab connections. These studies include investigations where the slabs were strengthened using FRP laminates around a central stub column or bonded over the entire width of the slab. with regard to flexural strengthening, externally bonded FRP strips have been used for the strengthening of one way slabs as well as two way slabs. The determination of the structural behavior of FRP–strengthened concrete slabs requires extensive experimental and/or advanced numerical methods. as far as theoretical methods are concerned, Reitman and Yankelevsky have developed a nonlinear finite element grid analysis based on the yield line theory. Other researchers have employed finite element packages to investigate the structural behavior of strengthened slabs with FRP that a full bond between the concrete and the adjacent strengthening FRP materials was assumed. Recently, Binici and Bayrak reported the test results of a strengthening method using carbon fiber reinforced polymers (CFRPs) as shear reinforcement. Previous studies concentrated on enhancing shear capacity of slab-column connections for new construction. Stirrups, bent up bars and shear studs were used as shear reinforcement in previous studies. This study investigates the application of different methods of strengtheing of flat slabs. At first, slabs were model in ABAQUS in order to study the parameters that influences punching shear capacity. Analytical result indicate that increasing concrete compressive strength improves punching shear capacity. Based on this result, steel reinforcement ratios determines the mode of failure. Then, FEM models of slab were strengthend, and type of strengthening, type of FRP materials, number of strip and layer were investigated. The results show that using FRP strip increases punching shear capacity and reduces energy absorption.}, Keywords = {Flat Slab,Punching Shear,Retrofit,Strengthening,Abaqus}, volume = {15}, Number = {3}, pages = {93-104}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-9231-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-9231-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {mirzakhani, aboozar and Hassani, Behrooz and khanlari, karen and ga,}, title = {Control point grid improvement in isogeometric analysis of axisymmetric structures using error estimation methods based on stress recovery}, abstract ={This research is devoted to the adaptive solution and control point net improvement of axisymmetric problems in isogeometric analysis using the error estimation based methods for stress recovery. For this purpose, after the calculation of the energy norm, the estimated value of error in the vicinity of each control point is assigned to the neighboring members of a hypothetical truss-like structure as an artificial thermal gradient. By analysis of this network of rods under the temperature variations a new arrangement of control points is obtained. Repeating this process of thermal isogeometric analysis will eventually lead to a better distribution of errors in the domain of the problem and results in an optimal net of control points for the calculation of the integrals. To demonstrate the performance and efficiency of the proposed method, two axisymmetric elasticity problems with available analytical solutions are considered. The obtained results indicate that this innovative approach is effective in reducing errors of axisymmetric problems and can be employed for improving the accuracy in the context of the isogeometric analysis method. Innovated method of this research focuses on adaptive analysis and Network improving of axisymmetric problems in isogeometric analysis using error estimation methods based on stress recovery. For this purpose after calculation the energy norm, estimated value of error in the vicinity of control points is assigned to each rod as the thermal gradient. Thus after analyzing the hypothetical rods network under the temperature changes a new arrangement of control points and knot vectors can be obtained. The use of multi-cycle of this process in isogeometric analysis will lead to a better distribution of errors in the domain and thus achieve optimal network to calculate the integrals. To measure the efficiency of this method and demonstrate the increased carefully in axisymmetric problems, which has the analytical solution, two elasticity problem is evaluated. The results show that innovative network improving method has good efficiency to reduce the error rate and can be used to increase the accuracy of isogeometric analysis results. Innovated method of this research focuses on adaptive analysis and Network improving of axisymmetric problems in isogeometric analysis using error estimation methods based on stress recovery. For this purpose after calculation the energy norm, estimated value of error in the vicinity of control points is assigned to each rod as the thermal gradient. Thus after analyzing the hypothetical rods network under the temperature changes a new arrangement of control points and knot vectors can be obtained. The use of multi-cycle of this process in isogeometric analysis will lead to a better distribution of errors in the domain and thus achieve optimal network to calculate the integrals. To measure the efficiency of this method and demonstrate the increased carefully in axisymmetric problems, which has the analytical solution, two elasticity problem is evaluated. The results show that innovative network improving method has good efficiency to reduce the error rate and can be used to increase the accuracy of isogeometric analysis results.}, Keywords = {Isogeometric analysis,Control Point,Adaptive Analysis,Axisymmetric,Error Norm}, volume = {15}, Number = {3}, pages = {105-118}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3051-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3051-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Nadi, Alireza and Goshtasbi, Kamran and Naghdabadi, Reza and Arghavani, Jamal and Ashrafi, Mohammad Jav}, title = {Experimental investigation of dynamic behavior of sandstone under high strain rates}, abstract ={Rock dynamics as a branch of rock mechanics deal with dynamic behavior of rocks under high loading rates. Considering that many problems in rock engineering including earthquackes, explosions and projectile penetrations deal with high loading rates, rock dynamics has been of high significance to explore. In order to design and stability analysis of many of defense and military structures constructed on and in rocks, designating of dynamic behavior of rocks under different loading rates is essential. However, detailed understanding of rock dynamics has been of high challenge due to the additional ‘4th’ dimension of time. The split Hopkinson pressure bar test (SHPB) is the most applicable and famous technique in determination of dynamic behavior of materials under high loadin rates. In this thechnique, a pressure wave with a high domain is dispatched to the specimen and the reflected and transmitted waves of specimen will be captured by means of strain gauges glued on the bars of Hopkinson apparatus. A dynamic stress-strain curve will be obtained for the specimen applying some known equations upon physical conditions of SHPB test. A great majority of studies have been shown that dynamic strength of rocks increases with an increase in loading rate. Also, it has been shown that inertial and heterogeneity effects are the most impressive factors on dynamic strength increase of rocks under high loading rates. It is of note that Inertial effect boils down to a sudden increase in inner pressure of rock. Although, heterogeneity causes a more proper dynamic stress equilibrium as well as an increase in strain rate of specimen before the failure relative to those of homogenous one. The more the loading rate is, the more the strength of rock increases. In the present study, efforts have been applied to explore the effect of loading rate on dynamic behavior of rocks using split Hopkinson pressure bar as the most known and common apparatus in studying dynamic behavior of materials under high loading rates. The specimens have been cored of the same block of sandstone with a diameter of 21.5 mm and aspect ratio of 2. First of all, some quasi- static tests including uniaxial and Brezilian have been done to obtain uniaxial compressive strength, Young’s modulus, poison’s ratio and tension strength. In the meantime, Ultra-sonic test has been applyied to group the specimens of same p-wave velocity before doing Hopkinson test. The dynamic stress-strain curves for the specimen under different loading rates have been gained after capturing incident, reflected and transmitted waves by the strain gauges. Results show that there is an intense dependence of dynamic strength of sandstone to the loading rate so that with imposing the strain rate of 150 s^(-1) on the specimen, the dynamic strength of sandstone has been increased to 260 MPa from 160 MPa in quasi-static conditions. That’s why DIF, as the ratio of quasi-static strength to the dynamic one, has been obtained 1.6 at the 150 s^(-1) strain rate.}, Keywords = {Rock Dynamics,SHPB test,Sandstone,Quasi-Static Strength,Dynamic Strength}, volume = {15}, Number = {3}, pages = {119-128}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11414-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11414-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {An experimental study on the hydroelastic behavior of continuous and multi component very large floating structures with hinge connection against waves}, abstract ={.Hydroelastic behavior plays a significant role in designing and constructing very large floating structures. There are different ways to reduce structure displacement and its stress due to wave. These structures are usually made separately out of the sea, and then components are connected to each other with rigid connection in installation location. Connecting components with joint connections to each other is one way to reduce the hydroelastic response. In this paper, the hydroelastic behavior of continuous structures is compared experimentally with structures composed of two and three sections. In order to simulate the hydroelastic behaviors of floating structure, the applied floating structure was 300 meters in height, 60 meters in width and its bending rigidity was equal to 4.77×1011 N.m2. Experimental model of aluminum was fabricated with length, width and height of 2, 0.55 and 0.04 meters respectively. polyethylene was used beneath aluminum plate in order to provide floating. The first model had no connection in its length; it was continuous. In the second model which consisted of two sections with 1 meter in length, there was a joint connection as a cross line in the middle of it. The third model consisted of three sections is made up by attaching three aluminum plates 67 centimeters in length which were connected together by hinges. In a wave generated tank of Graduate University of Advanced Technology laboratory with 16 meters in length and 1 meter in width and height, strain and vertical displacement measured at different points of experimental model. 5 regular waves’ periods of 0.67, 0.80, 0.91, 1.01 and 1.10 seconds were created. water depth was 70 centimeter. Comparison of the results shows that in all three models, the displacement in long waves is more than other waves. Also, in the models with hinge connection compared to the continuous model, the stress has been significantly reduced and its value has almost halved. At the first wave whose period is 0.67 second, the maximum stress is almost equal in the models with connections; so the models with three components reflected better performance regarding displacement and bending in comparison with other models. Due to the second wave (with periods of 0.8) displacement in the model with three components was less than the others, but the stress of this model was more than the model with two components. In such a case, in structure designing regarding the ratio of wave length to structure length, the more significant factor (displacement or stress) for the project must be preferred. In the last three waves (waves with longer length) the continuous model had less displacement. On the other hand, in this model which had no connections, the stress was more than the other cases. Therefore, a parameter which may offer both advantages can't be recommended. Since bending moment difference in the continuous model is twice more than the models with joint connections, if the structure displacement be within permissible limit of the project, using joint connection would be economical in designing.}, Keywords = {Hydroelastic behavior,Very large floating structure,Hinge connection,Multi component structures}, volume = {15}, Number = {3}, pages = {129-140}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-6425-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-6425-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Experimental Study of projectiles Penetration into Steel Fiber Reinforced High Strength Concrete Targets}, abstract ={It is necessary to investigate the concrete performance against impact loads due to increasing use of concrete in structure for available materials in many regions in one hand, and war or terroristic events on the other hand. Normal concrete has weakness against projectiles. For example spalling, scabbing and multiple impacts reduce concrete potential to tolerate imposing loads. Hence, improving normal concrete characteristics for better performance against these loads is essential. So, increasing compressive strength is the first alternative. However, numerous investigations reported that increasing compressive strength resulted in brittleness of the concrete. While, improving the performance of concrete against impact loads is contradictory to brittleness. One of the recommended alternatives for enhancing compressive strength of concrete and prevailing of its brittleness is reinforcing high-strength concrete by still fiber. In this study the performance of normal and high strength concrete with and without steel fiber was evaluated against the impact of ogive nose projectile with 7.62 mm caliber diameter, 12.5 gr weight and 830 m/s impact velocity. Concrete targets included 18 semi-infinite thickness cylindrical samples. Results showed that the pressure strength reduced in the SFRHSC samples as compared with NC samples. This is due to air locking in the samples which may be arise from the one: no suitable vibration for decreasing concrete slump, and the second: discontinuity in the concrete aggregates resulting from the steel fibers with improper aspect ratio. Results of the penetration tests showed that increasing compressive strength duo to reduction in water to cementitious materials ratio and partial replacing the cement with silica fume decreased penetration depth, crater diameter and volume as 10, 15 and 23%, respectively. While, adding of 0.5% steel fiber reduced penetration depth, crater diameter and volume as 7, 10 and 58%, respectively. Furthermore, in all no fiber steel samples expanded cracks and then sample collapse were observed. However, there were small cracks in fiber steel samples and damaged region was significantly reduced. In other words, about double increasing in compressive strength of concrete (from 452 to 860 kg/cm2) and 0.5% adding still fibers had a little effect on decreasing penetration depth and crack diameter. However, the effect of still fiber on depressing crack volume resulting from impact projectile was 252% more than increasing compressive strength (Figure 1). Furthermore, reinforced sample by still fiber were more :union: after impact projectile compared with the samples without still fiber which were disturbed completely (Figure 2). Finally, it may be concluded that for improving concrete performnace against impact loads including explosion and projectile impact, it is better to increase the compressive strength of concrete by using stronger aggregate such as cilice and quartz rather than decreasing water:cementitious ratio, increasing cement quantity and using silica-fume. Figure 1. Spalling crater volume in different concrete samples Figure 2. Crack extension in SFRC (left) and NC (right) samples}, Keywords = {SFRHS Concrete,Projectile,Penetration Depth,Crater Diameter,Crater Volume}, volume = {15}, Number = {3}, pages = {141-148}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3600-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3600-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Ameri, Mahmoud and Vamegh, Mostafa and Rohoolamini, Hamed and bemana, keyv}, title = {Evaluation of Nanoclay Effects on the Permanent Deformation of Hot Mix Asphalt}, abstract ={Permanent deformation or rutting in wheel paths is one of the most important failure modes in asphalt pavements that affect the pavement life . Permanent deformation in asphalt mixtures can be defined as the unrecoverable cumulative deformation that occurs mainly at high temperatures in the wheel paths as a result of repeated traffic loading . The deformation results in depressions on the pavement surface along the wheel tracks relative to other points on the surface . Permanent deformation in wheel paths is one of the fundamental defects that occur due to lack of bearing capacity in flexible pavement layers . This type of defect usually occurs in the roads in the tropical areas . Rutting occurs due to cumulative non - reversible Permanent deformations in the pavement layers under repeated traffic loading . In order to increase pavement life and consequently decrease maintenance related traffic delays , great demands are placed on permanent deformation resistance of asphalt mixtures . Hot Mix Asphalt is composed of aggregates and asphalt binder . Properties of these materials have important effects on the pavement structure performance. Although , asphalt binder is a little part of mixture ( in comparison with aggregates ) , but has major effects on the performance , durability and stability of the asphalt concrete mixture . Any change in asphalt properties will result significant changes in the asphalt concrete mixture performance . Since asphalt cement ( AC ) never fully satisfying lacks the physical and mechanical properties , researchers are constantly trying to improve the asphalt cement properties . Asphalt cement modification will result improved quality and increased life of the pavement . Nano - particles is one of the additives that are used to modify the properties of asphalt cement . Nano - clays are unique materials as additives to make significant improvements in the material properties of polymer Nano -composites. Nano-clay polymer materials typically strengthen the mechanical properties, modulus and stability of these cases. In this research, it is assumed that subgrade, sub-base and base layers of flexible pavement have sufficient resistance to rutting. Nanoclay is used to modification of bitumen properties for Hot Mix Asphalt mixtures better bearing capacity and resistance to rutting. So, limestone aggregate with 4 degration number, AC 60-70 and two types of montmorillonite Nanoclay: Cloisite 15A and Cloisite 30B are used in this study. Marshall and Dynamic creep tests in two stress levels ( 300 and 450 KPa ) at 50 ° C , as well as rutting test on the HMA samples with 0 , 2 , 4 and 6 percent of each Nanoclay were performed . Test results show that adding Nanoclay will result the better performance of HMA samples .}, Keywords = {Hot mix asphalt,Nanoclay,Permanent deformation,Marshall,Dynamic creep}, volume = {15}, Number = {3}, pages = {149-158}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10143-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10143-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Ghazali, Fatemeh and SalehiNeyshabouri, Seyed Ali Akbar and Kavianpour, Mohammad Rez}, title = {The effect of bottom outlet geometry changes on hydraulic characteristics of flow}, abstract ={Outlet conduits are one of the important parts of dams. Due to the high flow rate and pressure drop, problems such as cavitation can affect these structures. Considering these problems, detailed design is necessary. Laboratory studies are usually carried out which are expensive, thus, numerical models for determining complex flow characteristics have attracted the attention of the designers. In this study, the numerical simulation of Jegin dam outlet conduit in south of Iran with the scale of 1:10 is provided and the results are verified by experimental information taken from physical model built and tested at Water Research Institute. Gate opening in this research is always 70% and the water head is the constant value of 38.6m. The research is focused on the intake gate and not the service one, so the service gate is always fully opened. FLUENT computer code is considered for the numerical model studies. In the numerical simulation the Finite volume mixture two phase flow scheme is used together with k–e turbulence model. The flow discharge and air supply from the air vent downstream of the gate is then computed by 3D numerical model for different channel geometries. Reasonable agreement between the numerical model and experimental results shows reliable performance of the numerical model. This study showed the ability of the numerical model to simulate the complex air water flow in high speed gated tunnels. This study also includes the effect of the height to width ratio of the conduit on flow discharge and aeration downstream of the gate. To do this, different numerical models are simulated among which the difference is the height to width ratio of the conduit. Height and width of the conduit are measured at the gate section and changes are applied in two cases of constant height (depth) and variable width, and constant width and variable height. Results show more aeration and more flow discharge while heightening and widening of the outlet. Flow discharge has also been determined as function of the height to width ratio of the conduit at gate section of the channels. One of the important results is that in comparison with the width changes, height changes of the channel affect hydraulic characteristics of flow more and the diagram rates vary more sharply. Researches show that 1.5 to 2 ranges for height to width ratio is the best range hydraulically and other ranges have effect on reducing aeration and Air demand ratio β (β in this research agrees more with the relation Kalinske and Robertson presented), so the pressure in a conduit may fall considerably below atmospheric pressure which results in cavitation and vibration. To avoid these problems, suggests not to heightening the conduit more than a specific value.}, Keywords = {bottom outlet,Numerical analysis,aeration,conduit geometry,Fluent}, volume = {15}, Number = {3}, pages = {171-182}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10367-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10367-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Turbulent flow structure around submerged T-shape spur dike}, abstract ={Spur dikes are the training structures that may be used for river bank erosion protections. These structures may increase the navigation depth. The spur dike creates stable pool for aquatic habitat. Most of the previous researches focused on scour hole dimensions and the flowfield around the emerged spur dikes. As the spur dikes may be submerged during the floods, in this paper, the flowfield around a submerged T-shape spur dike was investigated using Vecterino apparatus. The experiment was conducted in a channel with 8m length, 60cm width and 80 cm depth at TarbiatModares University (Tehran- Iran). The parameters that were investigated in this paper includes, mean velocities, turbulence parameters and streamlines. The results of this study indicate that the high velocity region of the flow elongates to the far distance of downstream in the upper layers. There is a recirculating flow downstream of spur dike. Due to the effect of the spur dike overflow, the downstream recirculating flow, rotates in the opposite direction as compare to the emerged spur dike. The recirculating flow elongates to the far distance of downstream as compare to the submerged trapezoidal spur dike. Turbulence parameters analyzed in this research include normal Reynolds stress, bed shear stresses, the probability of each process and triple correlations. Maximum normal Reynolds stresses were observed at the upstream tip of the spur dike. In addition, the maximum shear stress was observed at the same region. The high stress region around the spur dikes showed a shear layer region around the spur dikes. Analysis of the probability of the turbulent bursting events in streamwise direction shows that ejection and sweep events are the most probable events in the upstream section of the spur dikes. In the streamwise direction, the interaction events are the most probable process near the upstream tip of the spur dike, while ejection and sweep events in the widthwise direction are the most probable events near the upstream tip of the spur dike. In the downstream recirculation zone of the spur dike, the probability of the events approximately are the same in the streamwise direction and interaction events are the most probable events in widthwise directions. Triple correlations presented useful information about the turbulent bursting process. The triple correlation analysis in widthwise direction showed that the ejection is the strongest event in shear layer region. Triple correlation analysis in the streamwise direction, showed that ejection was the strongest event in the upstream of the spur dike and in the region between near channel wall and spur dike wing. This causes sediment transport in streamwise direction as suspended load. The interaction events are the strongest events in the downstream recirculation zone, hence the sediments were deposited in this region.}, Keywords = {ADV,Spur dike,Flowfield,ADV,turbulence}, volume = {15}, Number = {3}, pages = {171-178}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1721-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1721-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Jabbari, Ebrahim and Chavoshian, Seyyed Ali and Boroumand, Amir and Masoumi, Fariborz}, title = {A New Approach to Selecting Optimum Locations of Sampling Stations in Karkheh Dam Reservoir Using CE-QUAL-W2 Model}, abstract ={Preservation and optimal usage of water resources are that main aspects of sustainable development in each country. Knowing qualitative and quantitative problems in water resources monitoring systems is one of the most important steps in water resources system management and pollution reduction plan. Recent studies in the field of water quality monitoring network has showen the needs for more researches, despite the abilities and investments in this field. One of the most important problems is the difference between required data and provided data in monitoring networks. So, monitoring systems should be revised and modified in several cases. High monitoring expenses necessitates optimizing monitoring systems to prevent cost loss. Being aware of network properties is an essential step in evaluating existing quality monitoring network. Locations of sampling stations, time frequencies, qualitative variables specifications and sampling duration should be considered in these evaluations. Reduce the cost of monitoring networks and maximize the obtained information, is the common objectives of the monitoring networks planning. From a monitoring perspective, identification of the reservoir eutrophication situation is of particular importance. Eutrophication phenomenon affects water quality strongly and causes serious limitations on the water utilization ability. Autotrophic organisms and algae overgrowth increased turbidity, toxic substances, increased sedimentation rate, oxygen concentration in the middle of the day and reduced severely by decreasing sunlight from sunset until next day morning, which causes anaerobic regions creation in deeper areas of the reservoir as the result. In this study, locations of Karkheh dam reservoir that there was maximum variations in quality indices values using CE-QUAL-W2 model, was identified. PO_4, NO_3, chlorophyll A and dissolved oxygen was studied to eutrophication control in reservoir. Because of limited available data from the time frequencies and sampling location point of view, dam reservoir was modeled by CE-QUAL-W2, 2D qualitative model for a period of one year. Using time series developed in previous step in model cells, time variance of studied parameters in the entire model cells was calculated and was used as a measure of its value change during time. Critical path from monitoring point of view was obtained after fitting best curve to cells with maximum time variance for studied qualitative indices. Placement of monitoring stations on this route will get the maximum information about the quality of the monitoring operation. The results showed that the proposed methodology is efficient in determination of critical paths for quality indices from monitoring perspective, in the dam reservoirs. ...Being aware of network properties is an essential step in evaluating existing quality monitoring network. Locations of sampling stations, time frequencies, qualitative variables specifications and sampling duration should be considered in these evaluations. Reduce the cost of monitoring networks and maximize the obtained information, is the common objectives of the monitoring networks planning. From a monitoring perspective, identification of the reservoir eutrophication situation is of particular importance. Eutrophication phenomenon affects water}, Keywords = {Water Quality Monitoring,CE-QUAL-W2 model,Eutrophication,Time Variance}, volume = {15}, Number = {4}, pages = {1-8}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11273-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11273-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Jafarian, Yaser and Haddad, Abdolhossein and Javdanian, Hame}, title = {Estimating the shearing modulus of Boushehr calcareous sand using resonant column and cyclic triaxial experiments}, abstract ={Shear modulus is one of the most important properties of soil deposit that should be evaluated as a preliminary step for site response analysis. Although numerous studies have been conducted to evaluate this parameter for silicate soils, there are considerably less studies on calcareous soils. However, extensive regions of the earth is covered with calcareous soils. This type of soil is typically observed near offshore hydrocarbon industries, such as the Persian Gulf. Calcareous sand is the accumulation of pieces of carbonate materials, originated from reworked shell fragments and skeletal debris of marine organism. These soils typically include huge oil and gas reservoirs which are continuously under an extending construction. Therefore, assessment of dynamic behavior of calcareous soils is a vital step for engineering projects. In this study, shear modulus of calcareous sand are investigated in the range of small and large strains using resonant column and cyclic triaxial tests, respectively. Bulk samples of Boushehr sand were collected from the North bank of the Persian Gulf near the Boushehr port. Preliminary mineralogy tests were conducted in order to estimate carbonate content of the samples. The sand contains considerable level of carbonate content and skeletal structure of the soil can be observed easily. Remolded samples of this sand were prepared via dry deposition method for either triaxial or resonant column tests. The results are presented in terms of shear modulus versus shear strain. The effects of confining pressure and relative density on the shear modulus of the calcareous soil are investigated. Moreover, for evaluating the effect of stress anisotropy on the shear modulus of calcareous soil, dynamic and cyclic tests were conducted under both isotropic and anisotropic conditions. The experimental results confirm that confining pressure has an important influence on the shear modulus of the tested samples. Increase of the mean confining pressure and relative density increases the shear modulus of the sand, as previously reported for the other sands. The results indicate that the effect of stress anisotropy on dynamic properties of calcareous sand is less important than those of mean confining pressure and relative density. With increasing mean confining pressure, the effect of relative density and initial stress anisotropy on the shear modulus increases. The normalized shear modulus are compared with the G-reduction ranges proposed for silicate sand by the previous researchers. This comparison show the need for some modification of the previous proposed ranges for normalized shear modulus curves. Finally, a modified hyperbolic model is presented for estimating the normalized shear modulus of Boushehr calcareous sand. It is demonstrated that the proposed model has more capability for prediction of the experimental G-reduction curves, compared with the models recommended for silicate soils. One advantage of the proposed model is the simple correlation developed for the reference shear strain in terms of initial effective confining pressure. The modified hyperbolic model presented in this study can be employed for site response analysis of the calcareous deposits of the Boushehr city.}, Keywords = {Calcareous Sand,Shear modulus,Stress Anisotropy,Resonant Column,Cyclic Triaxial}, volume = {15}, Number = {4}, pages = {9-19}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-5873-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-5873-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Derakhshan, Zahra and Baghapour, Mohammad and Nasseri, simin and Faramarzian, Mohamm}, title = {Performance of Submerged Aerated Biofilter for Atrazine Removal from Aquatic Environment}, abstract ={With less availability of land and loss of crops by pest, the use of pesticide such as Atrazine is increasing significantly. Atrazine is a member of s-triazine group herbicides and is a probable human carcinogen (Group 2B). Atrazine is resistant in the environment and, as a result, causes serious environmental problems. Moreover, it penetrates through the surface and subsurface water bodies as well as groundwater due to its excessive usage and high persistence and mobility. In general, several methods, such as adsorption, incineration, oxidation-reduction, photolysis, hydrolysis, dehalogenation, reverse osmosis, and chemical degradation, are available for removing Atrazine from contaminated water and wastewater; however, these methods are very costly, have many performance problems, produce a lot of toxic intermediates which are very harmful and dangerous, and cannot completely mineralize Atrazine. Biodegradation is an economically viable technology which leads to complete degradation and mineralization of Atrazine and produce simple compounds, such as carbon dioxide, water, nitrogen, and organic materials. Biological methods having enzymatic system that which is Atrazine used as carbon, nitrogen and energy source and completely mineralization occur, also submerged aerated filters to their treatment mechanism greatly contributed to reduce treatment cost. In this study potential of Biological Aerated Filter (BAF) in Atrazine removal from aquatic environment, at 4 concentration of Atrazine and 3 hydraulic retention times (HRTs) was evaluated. Based on the results Atrazine degradation potential of the mixed aerobic consortium was evaluated under various Atrazine concentrations and HRTs. It was shown that maximum efficiency in Atrazine and Soluble Chemical Oxygen Demand (SCOD) removal was 97.9% and 98.3%, respectively. Also stover-kincannon model have very good fitness (R2 > 99%) in loading Atrazine in this biofilter. Submerged aerated filter, a good performance in the removal of toxic and sustainable organic. High degradation rate of Atrazine at comparatively high Atrazine concentration might be due to the effect of concentration gradient. At high concentration gradient, the pollutant has a higher chance to be exposed to and/or penetrate through the cell which is essential for biodegradation. Co-metabolic process is used for bioremediation of most persistence contaminants, such as Atrazine. In co-metabolic processes, by utilizing primary carbon source or nitrogen source, microbes produce enzymes or cofactor during microbial activities which are responsible for degradation of the secondary substrates (toxic compounds, Atrazine). Also, the contaminants degrade in this process in order to trace concentrations. Cometabolism process was effective in Atrazine degradation process and aerobic mixed biofilm culture was observed to be suitable for the treatment of Atrazine from aqueous solutions. The present study investigated the ability of an BAf to remove Atrazine from aqueous environment. The BAF was operated at 3 different aerobic retention times in order to determine the optimum retention time for the highest Atrazine and COD removal.}, Keywords = {Atrazine,Herbicide,Biodegradation,Submerged Aerated Filter,Biological Filter}, volume = {15}, Number = {4}, pages = {21-30}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4286-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4286-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {A Study on Geotechnical Properties of Four Carbonates Sands From the Southern Coastal of Iran}, abstract ={General attention to carbonate sandshas been begun since the early 1960 in Iran. When the first bore drilled the Persian Gulf’s bed, it drew out layers of this soil type along with sand and shell. However, the large amount of carbonates in this soil was not first diagnosed. The first knowledge of the unique behavior of this type of soil was obtained during pile driving in the construction of an oil platform in Lavan Island, Persian Gulf, in 1968. In this operation, after a number of 30 inch pipe sank into the cemented soil for about 25 feet, they suddenly had a free fall with no resistance up to depth of 50 feet. Carbonate materials and aggregates can be found in nature in different shapes. The majority of them are made of calcium carbonate or other types of carbonate with soft and loose grains that can break easily. These soils are of remarkable importance in offshore engineering. Since early 70s, a great amount of studies have globally been conducted for identifying the unique engineering characteristics of carbonate sands. Different behavioral parameters including strain-stress behavior, shear strength, internal friction angle, volumetric behavior, elastic and shear modulus, Poisson’s ratio, carbonate content, shape of carbonate grains andetc have been studied. No certain laboratory methods or field study plan have yet been provided to obtain appropriate parameters for designing foundations in carbonate soils. Despite this, performing a number of laboratory and field experiments can be helpful. Executing at least amount of experiments to determine the following matters are essential: • Material composition, especially calcium carbonate content • The origin of the materials to distinguish between skeletal and non-skeletal deposits • The properties of the gains such as angularity, porosity, and initial void ratio • Compressibility of materials (using consolidation test) • Strength parameters of the materials, especially internal friction angle • Cementation, at least quantitatively In this paper, shear behavior of four skeletal carbonate sand samples obtained from the northern coasts of Persian Gulf and Oman Sea are investigated. Regarding some parameters of samples such as particle size distribution, physical properties, microscopic images of grains, compressibility, drained triaxial shear behavior, elastic modulus and internal friction angle it was attempted to promote geotechnical knowledge and improve civil engineers understandings of carbonate soils in this part of the world. On the basis of experimental tests like one-dimensional consolidation and triaxial tests, it was determined that despite a number of similarities between the shear behavior of carbonate sands, behaviorally they depend on the grains shape and size, initial particle size distribution and void ratio, calcium carbonate content, confining stresses and applied strains. Although all specimens were selected from the southern coasts of Iran, but a large number of difference was observed between them in terms of shear behavior and strength}, Keywords = {Carbonate sands,Triaxial experiment,Shear behavior,Persian Gulf,Oman Sea}, volume = {15}, Number = {4}, pages = {31-40}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-11729-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-11729-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {samaee, seyyed saee}, title = {Study of the effect of energy absorbing element in seismic performance of steel frames with symmetric y-shape concentric bracings}, abstract ={One of the common bracing systems in our country is Y-shaped bracing system. Because of architectural advantages, it attracts more attention in comparison to x shape concentric braced frame (CBF). But, its stiffness is less and it has more potential for out of plane buckling. One of the extensively used methods for improving the seismic behavior of the structural systems is using the passive control systems. By reducing seismic demand and increasing ductility, this control way can reduce the rate of seismic damage. Yielding dampers are one of the elements to achieve this kind of control in the structures. Because of good ability of yielding dampers in earthquake energy dissipation, the use of these dampers is increased through recent decade in passive control of structures. Due to development of passive control methods for earthquake energy dissipation and for preventing the structures from earthquake losses, this paper proposes a new improved dissipating element for Y shape bracing systems which could be used for structural rehabilitation of steel structures. The basis of the proposed element operation is its operation as a fuse element to improve the bracing elements behavior. The operation of the proposed element is in such a way that before formation of a hinge in bracing element, the presented element is yielded and by absorbing appropriate energy, prevents the bracing elements from inappropriate performance. Before inserting the proposed element in the bracing frames, using the ANSYS software, the element performance is studied for different dimensions and appropriate dimensions are determined. The energy absorbing element is inserted into two different positions in the bracing systems of interest. 2D steel frames with three different number of stories (4, 6 and 8 story frames) are modeled in SAP 2000 software, using conventional braced frames and their behavior is compared to braced frames with the proposed energy absorbing element. The frames are analyzed through nonlinear time history analysis, using appropriate time history records from near source and far source locations. The results show the appropriate ductility of the proposed element, the improvement of bracing elements behavior and also, the higher energy dissipation of the new bracing system, which can be shown through comparison of the hysteresis loops of the bracing frames, solely and those with proposed elements. It could be shown that the ductility of the system is affected by the position of the proposed element. Reducing the base shear due to earthquake records and also decreasing the permanent displacement of the structural stories after earthquake occurrence are some of other advantageous of the presented element. Inserting the new proposed elements in bracing system can also reduce the input energy of the system, during the earthquake. In general view, it can be concluded that by appropriate design of the proposed element, the other structural elements behave elastically and the inelastic behavior is happened in the presented elements, which is resulted in improving the seismic structural performance of the new system.The results of this study can be used in seismic design of earthquake resistant structures}, Keywords = {Y-shape bracing frame,Energy Dissipation,Seismic control,Rehabilitation,ductility}, volume = {15}, Number = {4}, pages = {41-53}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-8907-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-8907-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {1, 1}, title = {Development of COMAC and Damage Index Methods for Damage Detection in the Near of Abutments of Bridges}, abstract ={Bridges are exposed to damage during their service life which can severely affect their safety. Thus, it is important to monitor bridges for existence of damage. A damage in a structure alters its dynamic characteristics. Changes in properties such as the flexibility or stiffness matrices derived from measured modal properties and changes in mode shape curvature have shown promise for locating structural damage. Since damage alters the dynamic characteristics of a structure, namely its eigenproperties (natural frequencies and modes of vibration), several techniques based on experimental modal analysis have been developed in recent years. Therefore vibration characteristics of a structure can be used as the basis for vibration based damage detection (VBDD) techniques. These techniques have been recently subjected to a considerable amount of attention for damage detection due to their relative simplicity and the moderate cost of dynamic measurements. Damage detection methods based on the dynamic measurements of structures are one of the most important techniques for damage evaluation in bridges. VBDD methods use damage-induced changes to the dynamic properties of a structure to detect, locate, and sometimes quantify the extent of damage.VBDD methods are able to detect damage with information from the dynamic response of the bridge only. The performance of these methods for damage detection in bridges has not been fully proven so far and more research needs to be done in this direction. In this article a new method base on developing the Co-Ordinated Modal Assurance Criteria and Damage Inedx (DI) is present. For applying these methods, mode shapes and natural frequencies that came from health bridges model and damage bridges model are used. The bridges that used are a two-span bridge and a five-span bridge that modeled and verified. To verifying the models, five natural frequencies of the models that created with software, copmared to natural frequencies of the original models. In this article just one element defined as damage location. The damage created by redusing stiffness in one element near the abutments. The four level damage that considered are 15%, 30%, 70% and 90% reduce in module of elasticity. At first the unability of COMAC and DI methods to detecting the damage near the abutment is shown. Then the new method base on these method is presented. This new method is use of mode shapes that obtained from several longitudinal section instead of one longitudinal section. Results confirmed that if mode shapes are just extract from one longitudinal section like before, methods can not always detecting the damaged cross section or damaged longitudinal section. But if mode shapes obtain from several longitudinal sections, these methods will be able to assessment the damaged cross section plus damaged longitudinal section. Although in the most of the times these methods detecting the elements at the abutment as damage location wrongly. So it is necessarily to eliminate the result of the element at the abutment and then decided for the damage location. Besides it is concluded that for detecting the damage near the abutment, COMAC method has better}, Keywords = {Damage detection,Bridge,Mode Shape,Natural Frequency}, volume = {15}, Number = {4}, pages = {55-62}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4814-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4814-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Boroujerdian, Amin Mirz}, title = {Traffic movements risk evaluation on the physical area at intersections without lights by TTC index}, abstract ={The safety attracts attention increasing of traffic engineering to itself. The development of cities caused increasing of vehicles and accidents. The accident statistics show that the intersection points are one of the most eventful that occur 50 percent of all accident and 25 percent of human casualties. The first step in improving traffic safety is identification of hazardous situations. To improve traffic safety and design safety measures, It is important to recognize hazardous situations and causes of them. In addition, evaluating the effectiveness of measures implemented is also important. Based on traffic accident data, hazardous situations can be identified in roads and network. However, in small areas such as intersections, especially in resolution of maneuvers, identification of hazardous situations is impossible by using accident data for reasons such as the low occurrence of accidents in a particular area and record the exact location of the accident event. Due to shortcomings of traffic accident data, using surrogate measures such as traffic safety indicators have been taken into consideration. Therefore, in this study was used the traffic conflict. According to different problems of traditional traffic safety evaluation, the using of necessary methods is needed. In recent years, using of traffic conflict indexes has increased. Time-to-Collision (TTC) is one of the first and most widely used time-based indicators and many of the indicators are based on it. For using of these indexes the users’ speed, moving direction is needed. For high attention in safety evaluations and considering the type of the vehicle, two dimensional modeling of vehicle is presented. The critical interactions density index was based on the accident time index and traffic volume. The risk areas were identified three-dimensional by using ARC GIS software in the physical area of the intersection. By using this method, there is possible to identify high-risk areas based on critical traffic conflict. By using information obtained, determined how to improve intersection safety. As a case study the intersection of Vesal Shirazi to Bozorgmehr without traffic light in Tehran were selected. By video analyzing, data was recorded and risk areas were determined by using the method proposed in this paper. The evaluation results show that entry minor path to major path is riskiest because of conflict of the right movement minor path with the direct movement of the major path and the left movement minor path with the direct movement major path. The risk of right movement of minor path conflict to direct movement of the major path is 245.1 that about 8 times the average risk of all movements and , the risk of similar conflict on the other side of the intersection is 89.These conflict are the main reason for the increasing of the intersection risk.}, Keywords = {Traffic Safety,Traffic conflict,Accident Time Index,Risk,Hazardous Situations}, volume = {15}, Number = {4}, pages = {63-72}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3888-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3888-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Golshani, Aliakbar and biukaghazadeh, roshan and Asgari, ali}, title = {NumericalModeling of Seismic Behavior of Piles in Liquefiable Soil}, abstract ={The lateral spreading of mildly sloping ground and the liquefaction induced by earthquakes can cause major destruction to foundations and buildings, mainly as a result of excess pore water pressure generation and softening of the subsoil. During many large earthquakes, soil liquefaction results in ground failures in the form of sand boils, differential settlements, flow slides, lateral spreading and loss of bearing capacity beneath buildings. Such ground failures have inflicted much damage to the built environment and caused significant loss of life. The risk of liquefaction and associated ground deformation can be reduced by various ground improvement methods, including densification, solidification (e.g., cementation), vibro-compaction, drainage, explosive compaction, deep soil mixing, deep dynamic compaction, permeation grouting, jet grouting, piles group and gravel drains or SCs. Nowadays, using pile foundation is one of the popular solution for soils vulnerable to liquefaction. the pile with enough length more than liquefiable soil depth can reduce the large deformation and unacceptble settlements. Liquefaction and lateral deformation of the soil has caused extensive damage to pile foundations during past earthquakes. Several example of significant damages in pile foundation have been reported in the literature from the 1964 Niigata,1983Nihonkai-Chubu,1989 Manjil and 1995 kobe earthquakes. These damage have been observed mainly in coastal areas or sloping ground. evaluation of liquefaction in order to develop the northern and southern ports and implement coastal and offshore structures in Iran is of particular importance due to locating in a high seismic hazard zone and Liquefactable soil in coastal areas. Although, in recent years many studies have been conducted to understand the various aspects of this phenomenon, yet a lot of uncertainties have remained about the lateral deformations of the soil and its effects on deep foundations. In this study, behavior of pile groups (2 × 1, 1 × 3, 2 × 2 and 3 × 3) were evaluated using fully coupled three-dimensional dynamic analysis. Therefore, the influence of effective parameters such as number of piles, ground slope angle on soil and pile behavior has been studied using the finite element software Opensees SP v2.4. results indicate that most of the factors affecting the behavior of the pile, soil are not considered in the current design codes (such as JRA 2002) and these issues indicate the need to revise the current design and analysis methods.Lateral Pressures compared to that of JRA regulations show that these regulations cannot exactly predict pressures on pile and pile groups. Altogether comparing the results of numerical model of this research to various laboratory observations indicate that the use of numerical method can be reliable to predict the behavior of the soil and pile qualitatively and quantitatively using appropriate constitutive model and parameters for soil and pile. Keywords: Liquefaction soil, pile group, fully coupled numerical analysis, multi-surface-plasticity constitutive model.}, Keywords = {Liquefaction soil,pile group,fully coupled numerical analysis,multi-surface-plasticity constitutive model}, volume = {15}, Number = {4}, pages = {73-84}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10961-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10961-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Scour around a square pier with parabolic nose in presence of woody debris in front of pier}, abstract ={Woody debris accumulates in front of bridge piers, reduces the flow area, deviates the flow and increases the velocity around the bridge piers. Debris accumulation in front of bridge piers increases the downward flow, and shear stress around the bridge pier, therefore, the scour hole depth increases and bed degradation accelerates. Most of previous researchers focused on the scour depth around the bridge piers, and less researchers have investigated the effect of debris accumulation on the scour depth. To the best of our knowledge, the effect of debris accumulation on the scour depth has not been reported in previously published literature, as explored in this work. The purpose of this study is to experimentally investigate the effect of accumulation of woody debris in front of a square pier with a parabolic nose on the scour depth. The experiments were performed in clear water condition, with and without debris accumulation and with 20, 30 and 40 l/s discharges and for different debris dimensions. The experiments were performed in a sixty centimeter width channel at the hydraulic laboratory of Shahrekord University. Previous field studies showed that most debris accumulates in front of bridge piers in rectangular shapes, therefore three different rectangular shapes debris are designed and are placed in front of bridge piers during the experiments. Since, performed experiments at twelve hours showed the maximum equilibrium scour depth occurs at the first seven hours, therefore, all experiments are done in 420 minutes. The results showed that when woody debris is placed over, at, and below the water surface respectively, the ratio of scour depth to the scour depth of control sample is 2.2, 2.36 and 1.44, respectively. Moreover, when the percentage of blockage (ratio of the occupied flow area by debris to the flow cross section) is 30% and when debris is located below the water surface, the maximum scour depth will occur (2.36 with respect to the control sample). Also, the comparison between a square pier with parabolic nose and a sharp nose piers at the same hydraulic condition, show when there are no debris, the scour depth around the square pier with a parabolic nose is less than the scour around a sharp nose square pier (1.5 times). For the case in which debris are placed in front of bridge pier, the scour depth, width, and length around a square pier with a parabolic nose are significantly decreased with respect to a sharp nose square pier (2.3 times). Also, using dimensional analysis an equation is presented for predicting the maximum scour depth around a square pier with a parabolic nose in presence of woody debris accumulation. The results show that there is good agreement between predicted and observed scour depth.}, Keywords = {Local Scour,Dimensional analysis,Bridge pier,Flow blockage,Experimental study}, volume = {15}, Number = {4}, pages = {85-96}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2041-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2041-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Hadavifar, Mojtaba and bahramifar, nader and younesi, habibollah}, title = {Application of Amino and Thiolated Multi-walled Carbon Nanotubes for Removal of Mercury from Aqueous Solutions}, abstract ={Mercury is a highly toxic and accumulative metal and its compounds, especially methyl mercury, are neurotoxins which cause blockage of the enzyme sites and interfere in protein synthesis. The fate of inorganic, mercury ions in nature is its turning into methyl mercury due to the aerobic action of microorganisms. Mercury is a toxic metal that causes the serious environmental problems. The main sources of mercury ions in aquatic ecosystems are divergent, chloralkali wastewater, oil refineries, power generation plants, paper and pulp manufacturing, rubber processing and fertilizers industries. Various methods have been used for removing heavy metals from aqueous environment such as reverse osmosis, chemical precipitation, ion exchange, coagulation and adsorption. Many carbon-based nanoparticles (CNTs) have been developed to remove heavy metals from aqueous media. They are promising material for numerous applications due to their unique electrical, mechanical, thermal, optical and chemical properties. In addition, CNTs are proven to be superior adsorbents for several divalent metal ions in water, because of their capability to establish (π–π) electrostatic interactions as well as for their large surface areas. Therefore, they have received considerable attention for usage in analytical chemistry and environmental remediation. Multi-walled carbon nanotubes (MWCNTs) were the first observed CNTs involving of up to several tens of graphite shells. The sorption capability of MWCNTs is related mainly to the functional groups attached on its surface. Generations of functional groups on the surface carbon nanotubes improves the reactivity and provides active sites for further chemical modifications. Many researchers have developed amino and thiol functionalization on carbon-based adsorbents and CNTs in order to increase the adsorption capacity, selectivity and removal efficiency of heavy metals and organic compounds. Among these functional groups, the thiols have an excellent binding ability to some metals such as silver, mercury, copper, nickel and zinc. In present study, multi-walled carbon nanotubes were functionalized in four stages to create thiolated multi-walled carbon nanotubes (MWCNTs-SH). The synthesized amino and thiolated MWCNTs were characterized by Fourier transform infrared spectroscopy (FT-IR) and elemental analysis (CHNS) to ensur successfully entailing the functional groups on MWCNTs surface. The efficiency of all synthesized MWCNTs in mercury removal was investigated. MWCNTs-SH was more efficient rather than other synthetized adsorbents in mercury removal from aqueous solutions. Increasing in adsorbent dosage concluded an enhanced mercury removal. Solution pH has a more effect on mercury removal. When the pH increased from 2 to 8 the removal percentage ranged from 9.8 to 92%. The data fitted by Langmuir isotherm model (R2=0.966) better than Freundlich model (R2=0.935). The obtained maximum adsorption capacity (qm) by Langmuir model was 206.64 mg/g while its experimental value was 160.90 mg/g and was higher than that reported in other literatures. Thus the prepared synthetized adsorbent has high efficiency for mercury removal from aqueous solutions.}, Keywords = {MWCNTs,Mercury,Functionalizing,thiol functional group,Isotherm models}, volume = {15}, Number = {4}, pages = {97-104}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10023-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10023-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {YEGANEH, NAVID and AKHTARPOUR, ALI and BolouriBazaz, Jafar}, title = {Parameters Determination of Soil-Anchor Interaction for Numerical Modelling According to Field Data}, abstract ={Anchors play a special role in geotechnical structures such as excavations. The anchor section in soil is generally divided into five zones including reinforcement element, grout, grout and surrounding soil mixture, shear zone and soil media. The main objective of the present research is to determine the soil-anchor interaction parameters for numerical modeling of anchored wall using FLAC2D software. Basically, the injection area determining is the main challenge in the anchor force nomination. According to the proposed method, the diameter of the injected area is determined based on the injection pressure, grout volume, porosity and shear zone thickness. It is shown that the diameter of the injected area is approximately increased by 40% relatively to the drilling diameter. The diameter of the injected area in rock media, however, is equal to the drilling diameter. The other parameters are determined using equalization of rock media formulas for soil media. In order to ensure the validity of the proposed method, the pull-out test is numerically simulated in FLAC2D software. The numerical results have been then verified with anchor tension results in an excavation project. The results indicate that ultimate load of anchor calculated from the numerical model is comparable with equations proposed by many researches. Also, there is a negligible difference between the displacement obtained in numerical simulation and pull-out test results. This method is therefore can be used in numerical modeling of anchored wall in soil media with high precision. Anchors play a special role in geotechnical structures such as excavations. The anchor section in soil is generally divided into five zones including reinforcement element, grout, grout and surrounding soil mixture, shear zone and soil media. The main objective of the present research is to determine the soil-anchor interaction parameters for numerical modeling of anchored wall using FLAC2D software. Basically, the injection area determining is the main challenge in the anchor force nomination. According to the proposed method, the diameter of the injected area is determined based on the injection pressure, grout volume, porosity and shear zone thickness. It is shown that the diameter of the injected area is approximately increased by 40% relatively to the drilling diameter. The diameter of the injected area in rock media, however, is equal to the drilling diameter. The other parameters are determined using equalization of rock media formulas for soil media. In order to ensure the validity of the proposed method, the pull-out test is numerically simulated in FLAC2D software. The numerical results have been then verified with anchor tension results in an excavation project. The results indicate that ultimate load of anchor calculated from the numerical model is comparable with equations proposed by many researches. Also, there is a negligible difference between the displacement obtained in numerical simulation and pull-out test results. This method is therefore can be used in numerical modeling of anchored wall in soil media with high precision.}, Keywords = {Excavation,Numerical Modeling,Soil-anchor interaction,finite difference method,FLAC2D}, volume = {15}, Number = {4}, pages = {105-116}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10620-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10620-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {yousefi, maryam and assadollahfardi, gholamreza and elyasi, siamak}, title = {Mathematical model development for odor emission from landfills and composting plants toward residential cities, a case study for ammonia emission from Kahrizak landfill}, abstract ={Odour emission has been an obstacle for the development of composting facilities. Composting is an environment friendly process which produces secondary pollutants. Ammonia is the most existing compound in these facilities; therefore Odour dispersion studies depended on geographic and metrological conditions of these kinds of places toward residential cities are required. Ammonia is a Tang, toxic, reactive and corrosive compound. Determination the place of landfills and composting facilities must concord with environmental laws; otherwise the blowing wind could transmit pollutants toward residential cities. Industrial source complex is the most common method for modeling of odour emission from volume and area sources. Kahrizak landfill is located in the south of Tehran with latitude and longitude of 51°20'39" E and 35°28'05" N. The amount of waste discharged to this landfill is about 7000 ton per day. A mathematical model for odour and ammonia emissions from Kahrizak landfill based on Gaussian fluctuating plume theory has been developed in this paper. Using the two-dimensional theory of dispersion, the odour emission from that landfill has been calculated. Since the Gaussian dispersion equation is used for point sources, this equation should be changed to determine the ammonia concentration emitted from volume sources. Virtual point method is used to consider this problem. The mathematical dispersion model is based on Pasquill Gifford and Gauss theory. By using meteorological data cumulated from Emam airport meteorological station, In Pasquill Gifford equations, dispersion parameters and emission equation were calculated. WRPLOT software was used to determine the wind direction and Land gem software was used to calculate the ammonia emission rate. The data needed for this software cumulated from Kahrizak waste management Organization of Tehran. Monin obokhov length and net radiation used for stability class specification. Radiation angle and topographic parameters effects were considered in these calculations The wind velocity and temperature were respectively about 3.6 m/s and 8.4°C.. Bowen ratio, albedo ratio and surface roughness of the site were respectively 1.5, 0.35 and 1. The stability class in the mentioned condition was calculated C. Results show that ammonia emission rate from this landfill and composting facility are respectively about 60 g/s and 103g/s. According to EPA reports these values are reasonable. Finally ammonia dispersion equation was solved by Matlab computing program. Maximum ammonia concentration is about 180mg/m3 when x, the distance, is 80 meters and He, effective height, is1.5 m. Emitted ammonia from Kahrizak landfill could transport toward 2kms from this landfill. Since the nearest residential city is about 8.1 km far away from this landfill, therefore there is not a serious problem threatening people who live there. In order to protect environment and people, It’s recommended not to build any residential, commercial or industrial organization about 2 km from here.}, Keywords = {ammonia emission modeling,Kahrizak landfill,Gaussian dispersion equation,Industrial source complex model}, volume = {15}, Number = {4}, pages = {117-126}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4070-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4070-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {pirooznia, amir and pasbanikhiavi, maji}, title = {Investigation of the effect of isolation layer on reduction of seismic response of concrete gravity dams considering interaction effects}, abstract ={One of the important aspects which may affect the seismic response of gravity dams is dam-reservoir-foundation interaction. The dam-reservoir interaction must be taken into account, since the dam undergoes deformation which influences the motion of water in the reservoir. Due to the complexity of a dam­reservoir-foundation system, the finite element method is an efficient tool for studying the dynamic response of such a system not only due to the complicated geometry of the dam-reservoir-foundation system but also due to the mechanism of incident earthquake waves and different boundary conditions which can be simulated more appropriately. In order to seismic analysis of gravity dams, a computational procedure for two-dimensional finite-element analysis of dam­reservoir­foundation systems subjected to seismic excitations is developed using Ansys software in this research. Water is assumed as a compressible, inviscid fluid with small amplitude displacements and the dam is modeled as an elastic solid. The analysis is carried out in time domain considering dynamic excitations. Newmark time integration scheme is developed to solve the time­discretized equations which are an unconditionally stable implicit method. An application of the procedure to a study of the seismic optimization of concrete gravity dams using hydrodynamic isolation layer under horizontal and vertical ground motions is presented and discussed. In this study, the hydrodynamic isolation layer is used for the geometry and seismic optimization of concrete gravity dams. For this purpose, the volume of dam body is considered as the objective function and constraints of various geometrical and structural behaviors in order to optimize the concrete gravity dam under seismic loading. To demonstrate the effectiveness of the developed numerical model, the response of Koyna dam in India due to Taft ground motion is presented as a case study to show the hydrodynamic isolation effects on seismic optimization of concrete gravity dams. The model was analyzed and compared for the cases in which the isolation layer attached along the upstream face of dam for different conditions. Consider to obtained results, it is revealed that the isolation layer can have the reducing effect on responses of dam model because of damping the induced hydrodynamic pressure due to earthquake. The layer reduces the dam response due to the hydrodynamics effect of the reservoir in essentially two different ways: (a) the layer serves as a boundary for the reservoir with a low reflection coefficient which results in reduction in the developed hydrodynamic pressure in the reservoir compared with the case of a completely reflective boundary. This effect was addressed in the previous part of the theoretical solution excluding the layer's isolation effects. (b) the isolation of the dam from the hydrodynamic pressure is the result of the layer thickness as well as its material properties which alter the amplitude of the transmitted pressure wave across the layer.}, Keywords = {Concrete gravity dam,Interaction,Isolation layer,Time history analysis}, volume = {15}, Number = {4}, pages = {127-136}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1361-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1361-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {sharifnejadazizi, zahra and SalehiNeishabouri, Seyed Aliakbar}, title = {Numerical study on effective parameters on block-ramps energy dissipation}, abstract ={One of the most efficient energy dissipatoion structures in open channels are block ramps; which has been considered and used most often recently because of the the simple performance. This kind of energy dissipatores can be assumed as a particular type of baffle block chutes, but with natural base materials and without cement structure. In laboratories, several physical models have been built and examined about their efficiencies. Regardless of the cost and time of tests and examinations, they have had the scale change problems. Today by using efficient computational fluid dynamics codes (CFD) fluid hydraulic behavior is more widely examined. This paper at first, reviews the classification of this structures from the point of fabrication and roughness from various point of views. Then deals with the formation of some types of flow regimes (volume flow rate) on them. In continue to the study, numerical simulation on one kind of this block ramps have performed and energy dissipation mechanism on various flow regimes on them have surveyed. For this reason, in this study Flow-3D software is utilized. In this research, incompressible fluid assumption, VOF method to calculate the free surface and LES turbulence model is used. The results showed the more energy dissipation with more turbulence and more turbulence with forming the recirculating flow and extending the distance of the reattachment point from the boulders. Consequently, energy dissipation is maximom for lower volume flow rate and higher slope of the ramp. Because in these two conditions, the flow involves with roughness of the ramp more and more; hence it gets easier for turbulent flow to happen. In other words, energy dissipation is also maximom for the non-submerged boulders. Flows in which boulders are submerged have different mechanism of energy dissipation. In these type of flows, energy dissipation is maximom for the wake-interface flow condition and isolated roughness flow condition respevtively. Therefore, in order to enhance the energy dissipation in flow over block ramps it is advised to reduce the effective cross section or reduce the submergence of scale roughness with holding the same effective cross section and the volume of fluid flowing over the structure. Because in these two conditions, the flow involves with roughness of the ramp more and more; hence it gets easier for turbulent flow to happen. In other words, energy dissipation is also maximom for the non-submerged boulders. Flows in which boulders are submerged have different mechanism of energy dissipation. In these type of flows, energy dissipation is maximom for the wake-interface flow condition and isolated roughness flow condition respevtively. Therefore, in order to enhance the energy dissipation in flow over block ramps it is advised to reduce the effective cross section or reduce the submergence of scale roughness with holding the same effective cross section and the volume of fluid flowing over the structure.}, Keywords = {Block ramp,Energy disssipation,Numerical simulation,FLOW-3D software,Size of Boulders}, volume = {15}, Number = {4}, pages = {137-146}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1400-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1400-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Investigating Durability Time Interval of Three-Dimensional Steel Frame with Angle Connections under Elevated Temprature}, abstract ={The effect of fire on the structural steel frames has been frequently studied in the recent years due to its special importance. Because steel is sensitive to the temperature and reinforcing of steel frames against fire is highly expensive it is needed that behavior of steel frames in high temperature for reduction of undesired effect of temperature increase to be studied exactly. Now, for achieving to this goal and with regard to the expensive costs laboratory test and their limitations in analyzing at various parameters in each test, employing of finite element method as a strong tool for modeling of steel frames has depicted its value under temperature conditions. With respect to the above mentioned remarks, this paper aimed is to study the effect of fire on steel structures considering the softening behavior of connections and decreasing of strength. Then by using ANSYS software the duration of structure against ignition analyzed and the tested frame is a single span with three dimension and finally different conditions on frame has been compared, which this condition include the effect of connection type, studying the effect of longitudinal expansion, the effect of temperature loading type and beam length as well as fire type. After providing computer data, this result has been compared with results of other researchers.}, Keywords = {critical temperature,durability time,Fire}, volume = {15}, Number = {4}, pages = {147-154}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2781-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2781-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Azarbakht, Alirez}, title = {Influence of concrete behavior modeling on the nonlinear response of oscillators}, abstract ={Reinforced concrete structures are one of the most commonly used structures all over the world. However, the high nonlinear behaviour of this kind of structures still needs more research, e.g to shed light into the effects of nonlinear modelling and the structure characteristics. One of the most common methods to predict the nonlinear response of concrete structures is the simplified nonlinear spectra. The nonlinear spectra have been widely used in the seismic design and rehabilitation procedures e.g, ATC40 and FEMA 274. A set of closed-form formulas have been proposed in this manner to predict the strength reduction factor for a given period and ductility. The design and rehabilitation procedures can significantly simplified by using this kind of closed-form formulas. The aim of this paper is to evaluate the seismic behaviour of a set of 4620 single-degree-of-freedom (SDOF) oscillators, which was taken into account based on their period, damping and nonlinear backbone curve parameters. Eleven different periods, three damping ratios, five cracking states, seven ductility ratios, five hardening slopes and two collapse negative slopes were taken into account to cover a wide range of nonlinear behaviour of oscillators. The all combination of nonlinear characteristics with eleven periods and three damping ratios produces 4621 different oscillators to be investigated. The SDOF oscillators were analyzed for two sets of ground motion records which are representative of far and near field records. The far-field records contain 30 strike-slip records with moment magnitude of 6.5 to 6.9. The records are corresponding to the firm soil without any directivity effects. The near-field set contain 31 strike-slip records corresponding to four different earthquake events. They were all recorded within 16 kilometre of the earthquake epicentre. The incremental dynamic analysis was employed to calculate the system demand ductility in a wide range of earthquake intensity levels. The relationship between the strength reduction factor and the ductility factor was then derived for all considered SDOF systems. The results show that the natural period of vibration as well as the primary concrete cracking can significantly influence on the predicted strength reduction factors. The incremental dynamic analysis was employed to calculate the system demand ductility in a wide range of earthquake intensity levels. The relationship between the strength reduction factor and the ductility factor was then derived for all considered SDOF systems. The results show that the natural period of vibration as well as the primary concrete cracking can significantly influence on the predicted strength reduction factors. The incremental dynamic analysis was employed to calculate the system demand ductility in a wide range of earthquake intensity levels. The relationship between the strength reduction factor and the ductility factor was then derived for all considered SDOF systems. The results show that the natural period of vibration as well as the primary concrete cracking can significantly influence on the predicted strength reduction factors.}, Keywords = {Strength reduction factor,ductility,natural period of vibration,nonlinear spectrum,near field,Far field}, volume = {15}, Number = {5}, pages = {1-8}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2465-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2465-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Modeling of surcharge due to building on a liquefaction soil}, abstract ={Soil liquefaction describes a phenomenon whereby a saturated or partially saturated soil substantially loses strength and stiffness in response to an applied stress, usually earthquake shaking or other sudden change in stress condition, causing it to behave like a liquid. If the pressure of the water in the pores is great enough to carry all the load, it will have the effect of holding the particles apart and of producing a condition that is practically equivalent to that of quicksand the initial movement of some part of the material might result in accumulating pressure, first on one point, and then on another, successively, as the early points of concentration were liquefied.The phenomenon is most often observed in saturated, loose (low density or uncompacted), sandy soils. This is because a loose sand has a tendency to compress when a load is applied; dense sands by contrast tend to expand in volume or 'dilate'. If the soil is saturated by water, a condition that often exists when the soil is below the ground water table or sea level, then water fills the gaps between soil grains ('pore spaces'). In response to the soil compressing, this water increases in pressure and attempts to flow out from the soil to zones of low pressure (usually upward towards the ground surface). However, if the loading is rapidly applied and large enough, or is repeated many times (e.g. earthquake shaking, storm wave loading) such that it does not flow out in time before the next cycle of load is applied, the water pressures may build to an extent where they exceed the contact stresses between the grains of soil that keep them in contact with each other. These contacts between grains are the means by which the weight from buildings and overlying soil layers are transferred from the ground surface to layers of soil or rock at greater depths. This loss of soil structure causes it to lose all of its strength (the ability to transfer shear stress) and it may be observed to flow like a liquid (hence 'liquefaction'). The effect of structure on liquefaction potential of soil is very important, because it may prevent the occurrence of liquefaction phenomena or may to increase the intensity of liquefaction in the lower layers; hence the surcharge due to structures can be an important factor in the occurrence of liquefaction. Therefore in this study to model the surcharge of constructing a structure on liquefiable soil, first introduced the finite difference numerical analysis, then using FLAC 2D nonlinear dynamic analysis modeling of surcharge is carried. In this analysis, the modeling of surcharge due to building on a liquefaction soil and the effect of liquefaction potential of the economy has been studied. Also, the validation process and ensure the results of numerical analysis, modeling and comparing the results with a numerical model of centrifuge tests have been conducted. Results showed a significant decrease in the use of numerical modeling cost structures will be studied.}, Keywords = {FLAC 2D,Liquefaction,Surcharge,Centrifuge,FLAC 2D,Finn Model}, volume = {15}, Number = {5}, pages = {9-18}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1445-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1445-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {gordan, marjan and Niaomran, mahamm}, title = {Numerical Evaluation of the Retrofit Effectiveness for Fiber Reinforced Polymers (FRPS) Retrofitted Concrete Slab Subjected to Blast Loading}, abstract ={For retrofitting structures against blast loads, sufficient ductility and strength should be provided by Using high-performance materials such as fiber reinforced polymer (FRP) composites. The effectiveness of retrofit materials needs to be precisely evaluated for the retrofitting design based on the dynamic material responses under blast loads. The structural behavior of reinforced concrete (RC) slab retrofitted with fiber reinforced polymer (FRP) under blast pressure is simulated using nonlinear transient analysis of Ls-Dyna software. And the analysis results are verified with the previous experimental results. It was determined that overall the FRP retrofitted panels performed better than the companion control panels. Parametric studies are performed to examine the influence of FRP thickness, FRP strength, Compressive strength of concrete, ratio of steel bars on the response of retrofitted panel. Improvement on slab blast load resistance capacity is achieved by increasing all of parameters. But effect of increasing Compressive strength of concrete is more than another, In other words, increasing Compressive strength of concrete is economical. The relative effectiveness of CFRP and GFRP in strengthening deficient slabs can be evaluated by comparing the behavior of specimens. The two slabs in each set of specimens are similar in every aspect except that one slab was retrofitted by CFRP whereas the other one was confined by GFRP. The layers of the GFRP were as those of the CFRP. Comparisons of the ductility parameters show that both slabs in each set behaved in a similar manner and had comparable ductility parameters, the ultimate tensile strength of the CFRP fabric was higher than that of the GFRP fabric. The effectiveness of CFRP measured was larger than that of GFRP. From these test results, it appears that the effectiveness of FRP in enhancing slab ductility closely relates to its ultimate tensile strength..For retrofitting structures against blast loads, sufficient ductility and strength should be provided by Using high-performance materials such as fiber reinforced polymer (FRP) composites. The effectiveness of retrofit materials needs to be precisely evaluated for the retrofitting design based on the dynamic material responses under blast loads.The structural behavior of reinforced concrete (RC) slab retrofitted with fiber reinforced polymer (FRP) under blast pressure is simulated using nonlinear transient analysis of Ls-Dyna software. And the analysis results are verified with the previous experimental results. It was determined that overall the FRP retrofitted panels performed better than the companion control panels. Parametric studies are performed to examine the influence of FRP thickness, FRP strength, Compressive strength of concrete, ratio of steel bars on the response of retrofitted panel. Improvement on slab blast load resistance capacity is achieved by increasing all of parameters. But effect of increasing Compressive strength of concrete is more than another, In other words, increasing Compressive strength of concrete is economical. The relative effectiveness of CFRP and GFRP in strengthening deficient slabs can be evaluated by comparing the behavior of specimens.}, Keywords = {Reinforced Concrete slabs,fiber reinforced polymers,nonlinear transient analysis,Explosion,LS-DYNA Software}, volume = {15}, Number = {5}, pages = {19-30}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-12276-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-12276-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {nasiri, FARZIN and Afkhami, Maryam}, title = {Evaluation of the Application Distributed and Lumped Hydrologic Models in Simulation of Mean Daily Flow Discharge in Gharasoo river basin in Ardebil (Iran)}, abstract ={In this research, MIKE SHE distributed hydrologic model and MIKE NAM lumped hydrologic model has been used for simulation of mean daily flow discharge in Gharasoo river basin in Ardebil province (Iran). Generally in the distributed models, the whole watershed is divided to small elements and the amount of each effective parameter on watershed for each element is considered separately. While in lumped models, watershed is considered as an integrative unit and effective parameters on watershed are considered with their intermediate quantity. Progressed and comprehensive hydrological models for more accurate calculation of flow discharge in watershed have been highly applied in recent years and progresses performed in the development of distributed and physically based models, oriented the research towards the evaluation and comparative studies with other models including lumped models.Because of the lack of the correct knowledge of complex hydrologic cycle in consequence of incorrect planning of water resources in watersheds, it is necessary to take an effective act for calculating flow discharge by using progressed and comprehensive models in direction of stable development of watersheds in our country. As mentioned above, the application of distributed and lumped models has been evaluated in simulation of mean daily flow discharge in Gharasoo river basin.The watershed area is about 4100 Km2 and its elevation ranges from 1200 to 4788 m above the mean sea level. the study area lies between 470 45' and 480 40'E longitude and 370 49' and 380 30' N latitude. The average annual precipitation of this study area is about 284 mm. The most part of the study area has been covered by grass lands and crop lands. For confidence of correct simulation of hydrological processes by both models, the simulated discharge has been compared with observed discharge related to Samiyan hydrometry station that situated in out of the watershed for calibration and validation periods by using of evaluation criteria. The evaluation criteria including Root Mean Squre Error (RMSE), Standard Deviation of the Residuals (STDres), Correlation Coefficient (r) and Nash Sutcliffe Correlation Efficiency(E) have been used for evaluation of the application of the modeles along calibration and validation periods.The MIKE SHE model simulated daily discharge well as corroborated by correlation coefficients of 0.85 and o.80, root mean square errors of 4.0571 and 1.598 m3/s, standard deviation of the residuals of 4.0523 and 1.6m3/s and nash sutcliffe correlation efficiencyof 0.71 and 0.63 respectively for calibration and validation periods. The MIKE NAM model simulated daily discharge well as corroborated by correlation coefficients of 0.87 and o.78, root mean square errors of 3.13 and 1.6651 m3/s, standard deviation of the residuals of 3.122 and 1.6650m3/s and nash sutcliffe correlation efficiencyof 0.83 and 0.60 respectively for calibration and validation periods. The results of comparision between two models show that both of the models have appropriate application in simulation of mean daily flow discharge in the watershed. Also according to the calculated coefficient of efficiency in validation period, MIKE SHE distributed model had more appropriate application than the MIKE NAM lumped model.}, Keywords = {Mean daily flow discharge,MIKE SHE distributed model,MIKE NAM lumped model,Gharasoo river basin - Ardebil}, volume = {15}, Number = {5}, pages = {31-40}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3875-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3875-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Khaji, Naser}, title = {Devolopment of Decoupled Equations Methods for calculating hydrodynamic pressures on concrete gravity dams}, abstract ={Dams as one of the most important structures are always exposed to various hazards such as earthquake. As dam failure may lead to financial damages and fatalities, it should be designed with most economical and accurate methods. An earthquake causes hydrodynamic pressure waves exerting on the dam. This is one of the important factors in design of dams that are always considered by consulting engineers. Helmholtz equation is the governing relation on the propagation of hydrodynamic pressure waves in dam reservoirs during an earthquake. In order to solve the Helmholtz equation to calculate hydrodynamic pressures on dams, the reservoir’s boundary conditions (BCs) should be taken exactly into account. The BCs include (a) the interface boundary of dam and reservoir (as initial zone of reservoir excitation), (b) bottom boundary (with partial absorption of wave energy by accumulated sediments), (c) upstream boundary (with radiation of another part of the wave energy from the reservoir), and (d) formation of surface waves in the upper boundary of the reservoir. The purpose of present study is to model the mentioned physical phenomena in the frequency domain, using a new semi-analytical method, called Decoupled Equations Method (DEM). In the DEM, only the domain boundaries are discretized by specific high-order non-isoparametric elements. The main features used for modeling of geometry and physics of the problem consists of: (1) high-order Chebyshev polynomials as mapping functions, (2) special shape functions of 2n_η+1 degree polynomials for (n_η+1)-node elements , (3) Clenshaw-Curtis quadrature, and (4) integral forms produced by weighted residual method. By using these features and their properties, coefficient matrices of the system of governing equations become diagonal. This means that the governing partial differential equation for each degree of freedom (DOF) becomes independent from other DOFs of the domain to be analyzed. Therefore, this reduction in space dimensions of the main problem may significantly reduce computational costs in comparison with other available numerical methods. In this study, for the first time in order to provide a solution by low costs to calculate the hydrodynamic pressure distribution on the gravity dams, the relations of reservoir’s BCs are derived in local coordinates by using of the DEM and, the process of applying derived equations is then expressed into the solution of Helmholtz equation. To verify this method, an example of this field is solved by using the DEM, where dam and its rigid foundation are excited by horizontal harmonic vibration. The obtained responses from the solution of this example indicates that the present method for modeling of the potential problems with natural boundary conditions under earthquake excitations, by considering propagation of hydrodynamic waves in the reservoir, show acceptable accuracy and feasibility in comparison with the available analytical solution. The results of the DEM should be developed for more general condition of dam-reservoir interaction, which include flexible concrete gravity dams with inclined dam-reservoir interaction boundary conditions along with partial absorption of wave energy by accumulated sediments. These features are being followed by the authors, and will be disseminated in new papers soon.}, Keywords = {decoupled equations,rigid dam,hydrodynamic pressure,Frequency domain,semi-analytical method}, volume = {15}, Number = {5}, pages = {41-52}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-5039-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-5039-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Jahanmohammadi, Atefeh and Soltani, Masoud and Tasnimi, Abbas Ali}, title = {Local-average stress field concept in the post-crack analysis of RC members}, abstract ={Common smeared crack approach, which is mainly defined on the basis of average stress field concept, represents average constitutive models for both concrete and steel bars, in the post-cracking phase. These models are highly dependent on the cracking state and the local mechanisms, so the smeared crack approach is not accurate enough in the analysis of the problems including highly localized mechanisms. These mechanisms appear in anisotropically-reinforced or under-reinforced members, members with large crack spacing or the ones include discrete cracking. The "local stress field concept" is proposed herein to introduce the effect of the local characteristics into the average models. To represent a combine local-average stress field concept, the state of local strain and stress in the RC domain must be determined. Based on several parametric studies and validation procedures, a proposed closed form slip-strain relation is introduced to find out the local strain state along the steel rebar embedded in RC domain. This relation includes the effect of rebar diameter, average tensile stress in steel, initial characteristics of concrete and steel and the cover effect. Adopting the local stress-strain model for the steel rebar, along with the known local strains, the local stress distribution is also determined. Afterward, two main stress states are introduced for the definition of the combined local-average stress algorithm, one in the center of the between-crack length and the other, on the crack surface. Introducing the participated local stresses locating on the crack surface in equilibrium with the related local stresses in the centerline of the crack spacing, the cracking growth is detected. The procedure of the cracking is stopped where the concrete’s maximum stress at the centerline is less than the cracking stress and the crack spacing is fixed afterward. Representing another stress equilibrium condition between the local stresses at the crack surface and the average stress of both steel bar and concrete in the centerline, the average tension softening/stiffening parameter of concrete (C) is updated by use of the relation adopted for the average constitutive model of concrete. By use of the yield slip value, corresponding to the crack spacing and average tensile strain, the average yield stress of the steel, as its main average characteristic, is determined by the application of the proposed slip-strain relation. Considering the effects of the local mechanisms by updating average characteristics of concrete and steel, the combined local-average stress field concept is interpreted in the finite element programming procedure. To express the importance of introducing the local effects into the average behavior, the accuracy of the concept is assessed for the analysis of several experimental specimens including RC shear panels and walls. The concept is also evaluated for some specific cases where the localized mechanisms directly affect the total response.}, Keywords = {Smeared crack,local stress field,Slip-Strain relation,Nonlinear analysis,Finite Element}, volume = {15}, Number = {5}, pages = {53-66}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2206-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2206-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {khajepour, amir and behbahani, hami}, title = {select preventive maintenance treatments using AHP}, abstract ={In addition to existing rehabilitation and maintenance treatments, new treatments must be identified to optimize maintenance and management of pavement. Preventive maintenance treatments are used to reduce pavement distress rate and improve the pavement surface. These treatments can be effective when the pavement has no structural distress, so choose of optimum preventive maintenance is difficult. In addition, choose of optimum preventive maintenance treatment is dependent on many factors that makes choosing more difficult. Identifying these factors and knowing the fact that how preventive maintenance methods affect these factors, can significantly help managers to select the best method. In this paper, these factors have been identified and models for selecting the best preventive maintenance treatment have been presented. Due to lack of measuring devices, a simple calculation method for these factors has been presented. Finally, the importance of each factor has been analyzed by Analytical Hierarchy Process and models for selecting the best preventive maintenance method have been presented.}, Keywords = {pavement management,pavement maintenance,preventive maintenance treatment,analytical hierarchy process}, volume = {15}, Number = {5}, pages = {67-76}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4764-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4764-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {SalehiNeyshabouri, Seyed Ali Akbar and Zarrati, Amir Rez}, title = {Simulation of flow and sediment in bend and lateral intake of bend}, abstract ={Flow and sediment analysis is required for organizing or managing research projects in rivers. Due to fully three-dimensional nature of the flow in the river bend, streams and sediment are difficult to analyze. Development of three-dimensional numerical models and advanced computing power of computers has led to the increasing use of numerical modeling studies of hydrodynamic and sediment flow. But accuracy and validity of numerical results of flow especially in conjunction with the sediment at complex Geometry has not been determined yet. In the present study, in order to simulate the hydrodynamic of flow and sediment in the bend and lateral intake of bend, three-dimensional numerical model SSIIM2 has been used. Simulation results show that the model's prediction accuracy of hydrodynamic flow and the secondary flow in the bend, hydrodynamic flow in the lateral intake of the bend, and water surface in the lateral intake of the bend is acceptable. Model error in predicting the topography of the bed in the bend with lateral intake is relatively high. The error of the numerical model is due to using two-equation turbulence model k- ε and the sediment transport equations. Flow and sediment analysis is required for organizing or managing research projects in rivers. Due to fully three-dimensional nature of the flow in the river bend, streams and sediment are difficult to analyze. Development of three-dimensional numerical models and advanced computing power of computers has led to the increasing use of numerical modeling studies of hydrodynamic and sediment flow. But accuracy and validity of numerical results of flow especially in conjunction with the sediment at complex Geometry has not been determined yet. In the present study, in order to simulate the hydrodynamic of flow and sediment in the bend and lateral intake of bend, three-dimensional numerical model SSIIM2 has been used. Simulation results show that the model's prediction accuracy of hydrodynamic flow and the secondary flow in the bend, hydrodynamic flow in the lateral intake of the bend, and water surface in the lateral intake of the bend is acceptable. Model error in predicting the topography of the bed in the bend with lateral intake is relatively high. The error of the numerical model is due to using two-equation turbulence model k- ε and the sediment transport equations. Flow and sediment analysis is required for organizing or managing research projects in rivers. Due to fully three-dimensional nature of the flow in the river bend, streams and sediment are difficult to analyze. Development of three-dimensional numerical models and advanced computing power of computers has led to the increasing use of numerical modeling studies of hydrodynamic and sediment flow. But accuracy and validity of numerical results of flow especially in conjunction with the sediment at complex Geometry has not been determined yet.}, Keywords = {SSIIM2,Bend,lateral intake,scour,SSIIM2}, volume = {15}, Number = {5}, pages = {77-88}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3717-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3717-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Ayati, Bit}, title = {Comparison of Phosphorus Removal Efficiency in Reed, Bamboo & Cyperus}, abstract ={One of the major water pollution factors in receiving water bodies is the presence of excessive nutrients (nitrogen & phosphorous compounds) due to wastewater discharge to the environment. If phosphorus level exceeds its discharge standard (6 mg/L), it will cause eutirification which resulted in secondary water pollution due to algal blooming crisis. Development of different methods to remove phosphorus from the year 1950 was performed in response to the need of reducing the discharged phosphorus amount to surface waters. Phosphorus is removed using different chemical and biological methods that have disadvantages such as greater capital and operational costs, operational problems, high sludge production and safety operational & maintenance requirement. So phyto-remediation method can be used to overcome these disadvantages. This useful technology is actually a genneric term for several ways in which plants can be used to clean up contaminated soils and water. Considering this fact phyto-remediation is a bioremediation process in which a particular type of plant used to remove, transfer, stabilize, degrade and volatilize of contaminants (such as pathogens, heavy metals, pesticides, solvents, crude oil, arsenic, cyanide and radioactive elements) by accumulation, stabilization, extraction, rhizofiltration, rhizodegradation or volatilization mechanisms. Phytoextraction is the name given to the process where plant roots uptake polltants from the soil and translocate them to their above soil tissues. Rhizofiltration is similar in concept to Phytoextraction but is concerned with the remediation of contaminated groundwater rather than the remediation of polluted soils. The contaminants are either adsorbed onto the root surface or are absorbed by the plant roots. Phytostabilisation is the use of certain plants to immobilise soil and water contaminants. Contaminant are absorbed and accumulated by roots, adsorbed onto the roots, or precipitated in the rhizosphere. Selection of appropriate plant and microbial species, biological accumulation and transmission of pollutants, contaminant concentration and its disposal are the most important factors in phyto-remediation process. Environmental factors including ambient temperature, solar radiation, the presence of nutrients, water and oxygen and the type of material removal will also affect the process. In this study reed, bamboo and umbrella plant were evaluated in removal phosphorus from water in different concentration of 2,10, 25, 50 and 100 ppm in vitro condition (ambient temperature of 23-25 ◦C, DO of 4.5 – 6.5 and pH of 6.5- 8.5). According to the results, the maximum phosphorous removal was observed in reed plant pilot at concentration of 25 ppm. The percent removal efficiencies were found to be 17.3, 35.81, 87.94, 78.77, 48.63, 52.4, 92.01 for reed, 15.66, 21.07, 68.08, 57.89, 34.41, 48.33 and 73.69 for bamboo and 15.89, 21.5, 37.23, 32.41, 22.33, 30.48 and 54.47 for umbrella plant at mentioned concentrations, respectively. Overall phosphorous removal for reed plant, bamboo and umbrella plant were 59, 45.5 and 30.65, respectively.}, Keywords = {Phosphorus removal,Phytoremediation,Biomass}, volume = {15}, Number = {5}, pages = {89-96}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4344-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4344-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {mazloom, sajjad and saffarzadeh, mahmoo}, title = {An Integrated Fleet Scheduling and Allocation Model to Bus Rapid Transit Network}, abstract ={In this article has been tried to find a new solution for fleet assignment to BRT network through scheduling assigned fleet to routes. Vehicle scheduling in each route is done with regard to passenger waiting time at stations and in consequence assigned vehicle dispatching model is related to the first station at each route. In designing the model, it has been tried to develop it in a way that it can be extended and be useful on a worldwide scale. The proposed model for Tehran BRT network has been developed by lingo software with data acquired from the Tehran municipality transportation department and the results analyzed. One of the important finding in this research is that a necessity of using buses with high capacity in BRT systems.}, Keywords = {Public transport,BRT system,Assignment,scheduling,Lingo software}, volume = {15}, Number = {5}, pages = {97-106}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-10083-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-10083-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {صنایعی, Mehdi}, title = {Effects of distance between pontoons on wave transmission coefficient of dual floating breakwaters.}, abstract ={Abstract In spite of the large amount of work that has been done on coastal regions, a specific design for low-cost shore protection was serious need in small ports. Coastal protection structures are using to provide secured area for navigation and berthing of vessels. Using the breakwaters is the most popular method of coastal protection. Floating breakwaters are also using to provide partly calm water area by less cost in comparison with other breakwaters. Mentioned breakwater type is usually performed in small craft harbors that need impermanent calmness with low costs. Floating pontoons are one of the most usual floating breakwater types that composed of connected pontoons. Reports show that pontoon type floating breakwaters have appropriate performance in order to coastal protection. Floating breakwaters used to create tranquility in port. The floating breakwater use plenty in marine works, military operations, fishery activities, and recreational ports are abundant. In many ports, output ports are significantly affected by influx of waves, hence the existence of a floating breakwater seems to be necessary to increase efficiency and provide a safe environment for the ship. Breakwaters made in practical work, trying to reduce wave’s height in a specific location. The first record about a floating structure as a breakwater dates back to the early19th century. In 1811 General Bentham, the Civil Architect and Principle Surveyor of the Royal Navy of Great Britain, proposed a breakwater model for the British fleet at Plymouth. The Breakwater would consist of triangular sections of floating wooded frames moored with iron chain. The project cost was about one-tenth the cost of the rubble and granite mound structure which was finally adopted. The idea was rejected due to the concerns about its effectiveness during severe storms. In present research that conducted at hydraulic and marine structures laboratory of Tarbiat Modares University, two separated pontoons with variable distances, have been used as floating breakwater system. Considering the wave transmission coefficient as a main performance parameter, performance of the floating breakwater studied under the effect of the variation of distances between pontoons. In order to this, 160 tests lead in the wave flume and their results were compared with each other. Frequency domain method was used to analysis the raw data to decrease errors that may occur in time domain analysis method. In present research effects of distance between pontoons have been examined and the optimum distance of pontoons that leads to minimum transmission coefficient have studied. Results show that wave transmission coefficient of dual floating breakwaters is minimum at the range of the relative distance about 0.8 – 0.9 and its quantity will be maximum when relative distance of dual floating pontoons is at the range of 1.3-1.4. Keywords: irregular wave, dual pontoon floating breakwater, wave transmission coefficient, distance between pontoons.}, Keywords = {Irregular wave,dual pontoon floating breakwater,wave transmission coefficient,distance between pontoons}, volume = {15}, Number = {5}, pages = {107-116}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3678-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3678-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Arabzadeh, Abolfazl and AmaniDashlejeh, Asghar and MahmoudzadehKani, Iraj}, title = {Experimental Study of prestressed RC Deep Beams retrofitted by CFRP}, abstract ={Deep beams are the members that their behavior is different from conventional beams due to their special geometry and loading condition. Due to the low thickness compared with the height of the beams, the flexural reinforcement’s ratio is usually high and need to be placed in several layers. One of the most effective ways to reduce the ratio of the flexural reinforcement is to use of the prestressed reinforcement instead of conventional reinforcement which more conventional reinforcement can be replaced by a prestressed reinforcement. If that happens, there will be discussion of prestressed deep beams. In recent decades, along with the serious discussion of prestressed deep beams, reinforced concrete members retrofitted with FRP are also considered and in the last years the similar studies have also done on deep beams. The girders are usually prestressed deep beams in the structures such as reinforced concrete bridges, and if the retrofitting of them is considered, it will encounter with prestressed deep beams and it is necessary to have knowledge of the behavior of such members. However, the simultaneous effect of prestressing together with retrofitting has not been studied. For this, the experimental study was carried out in this paper for a better understanding of their behavior and comparing of their behavior with other deep beams. This paper study the behavior of simply supported deep beams experimentally by different conditions and has been examined their behavior compared to conventional deep beams, prestressed deep beams, and deep beams strengthened with CFRP. For this purpose, 10 deep beams with span to depth ratio of 2 are constructed and subjected to single-point failure load. Considering of this span to depth ratio is due to more compatibility with existing codes. The concrete cylindrical strength is considered greater than 400 kg/cm2 because of prestressed specimens. The test indicates that the idea of replacing of the prestressing cable instead of conventional reinforcements is appropriate and can increase the shear strength and initial stiffness of deep beams in addition to their bending strength. The analysis of experimental results shows that the effects of prestressing and strengthening are not the sum of prestressing and strengthening individually. Moreover, if two conventional and prestressed deep beams with equal shear capacity strengthen with the appropriate arrangements of CFRP, ultimate strength of prestressed deep beam will be 7% higher than conventional deep beam. The energy absorption and ductility of prestressed deep beams strengthened with CFRP are higher than strengthened conventional deep beams. Furthermore, the comparison of experimental results with existing codes and relations in the literature shows that none of the relations have the ability to predict the behavior of deep beams tested in this paper. It is necessary to generalize the existing relations to obtain to the accurate prediction.}, Keywords = {Deep Beam,Prestress,Post-tension,Carbon Fiber Reinforced Polymer (CFRP)}, volume = {15}, Number = {5}, pages = {117-126}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-478-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-478-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Alirezaei, Mehdi and HoseiniHashemi, Behrokh}, title = {Introduction and evaluation a combined system in order to a two-level performance}, abstract ={In this paper a new and innovative configuration of lateral bracing for steel frame construction is presented and discussed. Eccentrically Knee Bracing (EKB) frame, as it is called in this paper, is made up of four structural elements, the knee element, the diagonal brace element, the link element and the columns. The knee and link elements are a fuse-like element that dissipates energy by the formation of plastic shear hinges or flexural hinges when the building is subjected to moderate and severe lateral loads, respectively. The diagonal brace element, on the other hand, provides the required level of lateral stiffness and remains in the elastic range at all time. In order to examine this system behavior, ANSYS, which is a well-known finite element software is used. Also two half-scale EKB were tested using the SAC loading protocol and an innovative loading protocol. The experimental and numerical results indicated that in this system, ductility and cumulative dissipated energy can be significantly increased. Eccentrically braced frames (EBFs) have been indicated as the excellent elements of a structural typology suitable for satisfying the different design objectives of modern performance-based seismic engineering in medium or high-rise steel buildings. EBFs address the desire for a laterally stiff framing system with significant energy dissipation capability to accommodate large seismic forces. EBFs combine the high elastic stiffness of concentrically braced frames (CBFs) with the high ductility and energy dissipation capacity of moment resisting frames (MRFs). The excellent seismic behavior of EBFs reported in the first numerical studies on traditional eccentrically braced structures subjected to lateral static forces. To improve the seismic performance and behavior of the steel framed structures, further modification and innovation to enhance the structural performance is essential. For this purpose, a modified structural form that adopts eccentrically knee brace elements in the corner regions of the beams and columns, namely Eccentrically Knee Braced frame (EKB) is considered in this study. In an EKB, one end of the brace is connected to a short knee element instead of beam-column joint and other end of brace is connected to a short link element. The link element which is the short beam segment between the brace-beam and beam-column joint, is designed to dissipate energy through shear yielding during severe earthquakes. Thus, the link element acts as a ductile fuse to safeguard the brace against possible buckling. In this study, the knee element is designed in such a way that the knee yields in shear instead of flexure under moderate excitation and link element is designed to yield under severe excitation. The seismic performance and ductility of this proposed system is of great concern, which is covered in the current paper. All tests were of the cyclic quasi-static type for which similar displacement time histories were considered.}, Keywords = {Braced frame,Hysteretic behavior,Steel frames,Two levels performance}, volume = {15}, Number = {5}, pages = {127-136}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-9519-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-9519-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {abbasi, mohammad and fathi, mojtab}, title = {Renovation of Orthotropic steel decks to control fatigue in rib-to-deck joints}, abstract ={One of the main reasons for the fatigue problems in Orthotropic steel decks is the low stiffness of the deck plate. In this study, By increase the deck plate stiffness with three methods of renovation, Reducing stress in the rib-to-deck connections is investigated. For this purpose, a orthotropic steel deck is modeled with ABAQUS finite element Software, and According to the AASHTO LRFD Bridge Design Specification is simulation of fatigue and Then with the help of three methods of Renovation Bonded steel plate, Sandwich steel plate and Reinforced High Performance Concrete ,This reduction of Stresses is studied. The analysis results indicate that at the rib-to-deck joints, Stresses on the deck plate can be reduced by 80% and on the rib web can be reduced by 70% using this renovation methods, As a result, fatigue life of the deck will increase significantly. Also, The comparison of the Renovation methods shows that among renovation methods, Reinforced High Performance Concrete method will give the best results. An orthotropic bridge deck (OBD) consists of a deck plate supported in two perpendicular directions by a system of longitudinal stiffeners and transverse crossbeams which are, in turn, spanned by main girders. All these elements are connected by welding. Fatigue is a well-known phenomenon in orthotropic bridge decks. Several welded details appeared to be extremely sensitive to fatigue loading and shortened drastically the life span of orthotropic bridge decks. One of the most threatening fatigue cracks concerning the traffic safety running on the bridge is the one at the longitudinal welds between the deck plate and trapezoidal stiffener. The main reason is the low stiffness of the deck plate, which is insufficient to deal with the wheel loads of heavy traffic. Moreover, the increase of heavy traffic in the last decades makes the fatigue phenomena an even greater concern. It became clear that existing orthotropic bridge decks needed to be stiffened in order to decrease the stresses at the welds and extend their fatigue life. In the past decades, this subject attracted international attention and several studies have been performed on the fatigue phenomena and on the possible reinforcement systems. The transverse distribution of wheel loads in orthotropic decks generates significant out-of-plane bending moments in the deck plate and rib wall at the rib-to-deck joint. Due to the relatively small thickness of both the deck plate and rib wall, the out-of-plane bending moments result in high local flexural stresses causing fatigue cracks to develop at the joint. in the rib-to-deck connections, Due to the geometry of the welding, there are four potential spots around the weld where the fatigue cracks may initiate, wherein: Crack 1 initiates in the weld root and propagates through the deck plate Crack 2 initiates in the weld toe in the deck plate and propagates through the deck plate Crack 3 initiates in the weld toe in the trough web and propagates through the trough web Crack 4 initiates in the weld root and propagates through the weld throat.}, Keywords = {Orthotropic steel deck,Rib-to-deck joints,points susceptible to fatigue damages,Renovation methods}, volume = {15}, Number = {5}, pages = {149-160}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-9509-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-9509-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {fakhri, mansour and hassani, abolfazl and kari, mohamm}, title = {Analysis of friction and texture of asphalt pavement by British pendulum tester and sand patch test}, abstract ={Slipperiness of the road surface is one of the factors which increase the risk of accident. In fact slip occurs when the coefficient of friction between the tire and road surface is not enough to keep the adherence between the two. Skid should not be considered as a separate issue, but to solve this problem, we should optimize properties of tire and road which leads to decrease in possibility of skid. This is a fact that the less the skid resistance value, the more accidents in fall and winter which have more rain. Road friction changes with change of many factors such as properties of pavement surface, properties of tire, moisture of road and performance of vehicle. There is a need to manage skid resistance systematically to maintain the level of safety performance of roadway surfaces. This study focused on the development of a skid resistance deterioration model based on the analysis of skid data inventory collected in Tehran. This field study has been performed by examining the statistical information related to traffic and accidents and case study of a street with heavy trafficin inTehran as follows. Hot mix asphalt was provided from factories of municipality of Tehran and was distributed and tests of hot mix asphalt were done by Marshal test; then British pendulum method was used to determine the microtexture, and sand patch test was used to determine mean surface macrotexture depth. Finally by repeating the test in time intervals within 18 months and investigating the relationship between the data and test results, charts of state of changes of skid resistance over time were presented which indicated that slip resistance of asphalt pavement decreases by time and traffic crossing. First this decrease is more and then gradually declines. By comparing the results with standard it is concluded that the skid resistance of asphalt pavement should be improved after 7 months. result shows the variation of pavement skid resistance versus pavement age. Also by investigating the statistical reports given by the road police in the aforesaid street it was found that about 50% of the accidents are related to function of brakes of vehicles and friction resistance and comparing the statistics reveals that after the road surface is improved by asphalt, accidents in case study street decreased by 25%. After that with comparing the number of accidents in the studied street in the second 6-month of year and during the year especially in accident prone points it was found that number of accidents in the second 6-month is 70% of the whole year. This indicates the particular effect of weather condition in rainy season and decrease of skid resistance of pavement due to roads surface wetting on number of accidents.}, Keywords = {skid resistance,British pendulum tester,pavement texture,accidents}, volume = {15}, Number = {5}, pages = {161-168}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-731-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-731-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {sabri, Mansour and Ghazvinian, Abdolhadi and nejati, Hamidrez}, title = {EXPERIMENTAL AND NUMERICAL INVESTIGATION OF CRACK PROPAGATION IN PARTICLE SIZE HETEROGENEOUS ROCK LIKE MATERIAL}, abstract ={An experimental and numerical approach on crack propagation and fracture toughness of Central Straight-through Crack Brazilian Disk (CSCBD) samples under compression is carried out to be investigated the effect of particle size heterogeneity. To accomplish this goal, six type of specimens with different silica sand particle size but same combination are used for preparation CSCBD specimens. Diametrical compression load with a rate of 0.3 mm/min in two directions respect to the central crack orientation is applied to the discs and the failure loads corresponding to the each test are recorded. Also In this study, a numerical simulator based on RFPA (Rock Failure Process Analysis) is used to study the crack propagation path and fracture load in simulated CSCBD specimens with different particle size (Similar laboratory specimens). In this simulator, the heterogeneity of specimens is considered by assuming that the material properties of elements conform to a weibull distribution. Result of laboratory tests indicates a nonlinear relation between specimen’s particle size and mode I and mode II fracture toughness. The specimen whit medial particle size (2-2.38 mm) has the maximum fracture toughness in two fracture mode. Toughness of specimens decreased with increase and decrease of silica sand particle size. Numerical results shows, the trajectory of crack path for fine particle are more regular and initiated from the crack tip, propagate parallel to the load direction. But it’s for coarse particle, initiated from the boundary of grains in whole of the specimen and lead it to failure in an unexpected path. An experimental and numerical approach on crack propagation and fracture toughness of Central Straight-through Crack Brazilian Disk (CSCBD) samples under compression is carried out to be investigated the effect of particle size heterogeneity. To accomplish this goal, six type of specimens with different silica sand particle size but same combination are used for preparation CSCBD specimens. Diametrical compression load with a rate of 0.3 mm/min in two directions respect to the central crack orientation is applied to the discs and the failure loads corresponding to the each test are recorded. Also In this study, a numerical simulator based on RFPA (Rock Failure Process Analysis) is used to study the crack propagation path and fracture load in simulated CSCBD specimens with different particle size (Similar laboratory specimens). In this simulator, the heterogeneity of specimens is considered by assuming that the material properties of elements conform to a weibull distribution. Result of laboratory tests indicates a nonlinear relation between specimen’s particle size and mode I and mode II fracture toughness. The specimen whit medial particle size (2-2.38 mm) has the maximum fracture toughness in two fracture mode. Toughness of specimens decreased with increase and decrease of silica sand particle size. Numerical results shows, the trajectory of crack path for fine particle are more regular and initiated from the crack tip, propagate parallel to the load direction. But it’s for coarse particle, initiated from the boundary of grains in whole of the specimen and lead it to failure in an unexpected path.}, Keywords = {Fracture toughness,particle size heterogeneity,Rock Failure Process Analysis}, volume = {15}, Number = {5}, pages = {169-180}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-12239-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-12239-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Komakpanah1, Hamed and Yasrebi, , Seyyed Sahahboddin and Golshani, Aliakbar}, title = {Application of Artificial Neural Networks in Prediction of Expansive Behavior of Clay Soils}, abstract ={  In the recent years, new techniques such as artificial neural networks were used for developing of the predictive models to estimate the needed parameters in Geotechnical Engineering such as swelling potential. If over 50% of the particles in a sample are able to pass through a number 200 screen or sieve then the sample is classified as either silt or clay or some combination of both. Regardless of the percentage of “fines” in a particular sample, a significant presence of clay minerals in a sample can indicate a possible expansive soil problem. When they absorb water they increase in volume. The more water they absorb the more their volume increases. Expansions of ten percent or more are not uncommon. This change in volume can exert enough force on a building or other structure to cause damage. Cracked foundations, floors and basement walls are typical types of damage done by swelling soils. Damage to the upper floors of the building can occur when motion in the structure is significant. Expansive soils will also shrink when they dry out. This shrinkage can remove support from buildings or other structures and result in damaging subsidence. Fissures in the soil can also develop. These fissures can facilitate the deep penetration of water when moist conditions or runoff occurs. This produces a cycle of shrinkage and swelling that places repetitive stress on structures. Determination of swell potential of soil is difficult, expensive and time consuming and also involves destructive tests. Multi-layer Perceptron model is one of the most sufficient methods of the Artificial Neural Networks in most of the research applications in engineering etc. In this research, Multi-layer Perceptron model and Radial Basis Function model of ANN (artificial neural networks) were used in order to predict expansive behavior of clayey soils (i.e., swell percent). All data have been modeled by using many types of architectural Multi-layer Perceptron network. Then, the output result of these networks are compared with each other according to the assessment indexes which has been leaded to the best architectural network selection in viewpoint of accusation and usage. It is noticeable that the parameters such as Natural Water Content, Plastic Index, Dry Density and Fine Soil Percent are considered as input parameters and swell percent (S%) is considered as output parameter. The Soils which are selected for this research is clayey soils from different areas of Iran. Consequently this ANN has the ability to predict expansive behavior of diverse types of clayey soils. To train this network, results of previous researches, geotechnical consultant engineering data and the available thesis about Expansive soils are used. It was found that the Multi-layer Perceptron (MLPst and MLPdy) models exhibited a higher performance than Radial Basis Function (RBF) model for predicting expansive behavior of clayey soils. Also, the comparison of the MLPst and MLPdyn network models indicates that their accuracies are almost the same. However, the time taken by MLPst is less than that of MLPst in this study. Since the population of the analyzed data is relatively limited in this study, the practical outcome of the proposed models could be used with acceptable accuracy at the preliminary stage of design.}, Keywords = {}, volume = {15}, Number = {5}, pages = {181-190}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-8121-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-8121-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {}, title = {Removal of methylene blue from aqueous solution using graphene oxide nanosheets: kinetic and isotherm study}, abstract ={In this study, graphene oxide nanosheets have been used for the adsorption of methylene blue, a cationic dye from aqueous solution. The physical characteristics of graphene oxide nanosheets studied using Fourier transform infrared (FTIR) and X-ray diffraction (XRD). The adsorption of the methylene blue onto the graphene oxide nanosheets has been carried out at different experimental condition such as contact time (1- 4 hours), adsorbent dosage (0.05 - 0.7 g/l), pH of solution (3 - 9) and initial concentration of dye (50 – 400 mg/l). The results show that the maximum adsorption (910 mg/g) under these conditions; adsorbent dosage of 0.05 g/l, initial concentration of 50 mg/l, two hours contact time and pH=6. The kinetic of adsorption data analyzed using three kinetic models such as elovich model, pseudo first-order model and pseudo second order model. Kinetic study indicated that the maximum adsorption was reached at two hours and follows the linear form of pseudo second-order kinetic model. The adsorption isotherm has been investigated in the pH range of 3 to 9, initial concentration of 50 to 400 mg/l and the adsorbent dosage of 0.05 to 0.7 g/l in 25 °C. The equilibrium data fitted to the Langmuir isotherm model well. Thus, graphene oxide nanosheets can be known as a good adsorbent for the adsorption of cationic pollutants. In this study, graphene oxide nanosheets have been used for the adsorption of methylene blue, a cationic dye from aqueous solution. The physical characteristics of graphene oxide nanosheets studied using Fourier transform infrared (FTIR) and X-ray diffraction (XRD). The adsorption of the methylene blue onto the graphene oxide nanosheets has been carried out at different experimental condition such as contact time (1- 4 hours), adsorbent dosage (0.05 - 0.7 g/l), pH of solution (3 - 9) and initial concentration of dye (50 – 400 mg/l). The results show that the maximum adsorption (910 mg/g) under these conditions; adsorbent dosage of 0.05 g/l, initial concentration of 50 mg/l, two hours contact time and pH=6. The kinetic of adsorption data analyzed using three kinetic models such as elovich model, pseudo first-order model and pseudo second order model. Kinetic study indicated that the maximum adsorption was reached at two hours and follows the linear form of pseudo second-order kinetic model. The adsorption isotherm has been investigated in the pH range of 3 to 9, initial concentration of 50 to 400 mg/l and the adsorbent dosage of 0.05 to 0.7 g/l in 25 °C. The equilibrium data fitted to the Langmuir isotherm model well. Thus, graphene oxide nanosheets can be known as a good adsorbent for the adsorption of cationic pollutants. Thus, graphene oxide nanosheets can be known as a good adsorbent for the adsorption of cationic pollutants.}, Keywords = {Dye adsorption,Adsorption isotherm,Kinetic,Grahene oxide,Methylene blue}, volume = {15}, Number = {5}, pages = {191-198}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-3322-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-3322-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Garivani, Sadegh}, title = {Introducing Comb-Teeth Yielding Metallic Dampers}, abstract ={Passive energy dissipation devices have been widely used in structures in the last decades, as effective and relatively low-cost systems to reduce the earthquake damage. Inelastic deformation of ductile metals in metallic dampers is a mechanism which may be used to dissipate seismic energy. The research on yielding metallic dampers was started by the pioneering works of Kelly et al. (1972), which was continuously followed by other researchers. These dampers, if used effectively, can dissipate significant portion of seismic energy through inelastic deformation of ductile metals. Generally, depending on the yielding mechanism, metallic dampers can be divided into four groups of flexural, axial, shear, and torsional. The most wide spread yielding dampers are Added Damping and Stiffness, ADAS, Triangular-ADAS. Yielding shear panels and slit dampers are other types of yielding dampers that are studied more recently. Slit dampers are known as a special type of metallic dampers, in which plates with a number of slits or openings are subjected to in-plane shear deformations. The slits/openings divide the steel plate to a series of links acting in flexure under the global in-plane shear deformation of damper. Based on the concept of slit dampers, researchers have proposed and tested various types of dampers. In addition some attempts have been made to find out the optimum geometry of openings and usually, rhombus-like openings have found to be more suitable than others. Considering the results and observations of previous studies on slit dampers, this paper presents a new yielding metallic damper called comb-teeth damper, CTD, which consists of a series of steel links/teeth acting in parallel and dissipating energy through in-plane flexural yielding deformation. Special attention is paid to the geometric design of links in order to generate uniform stress distribution along their length and to prevent strain localization and premature failure. The design is then checked out through a set of nonlinear finite element analyses and finally, experimental specimens are fabricated and tested under cyclic loads. Experimental studies have confirmed very stable hysteretic behavior of CTDs under cyclic loading with large displacement amplitudes. For example, a specimen was loaded under twenty fully reversed cycles at amplitude of 40 mm and even after these cycles, hysteretic curves were quite stable and thus displacement amplitude was increased to 60 mm. It should be noted that 40 and 60 mm in amplitude respectively correspond to more than 20 and 30 times the yield displacement of outer fiber of links. After numerical and experimental investigation of the behavior of CTD specimens, the behavior of three simple steel frames equipped with such dampers is studied under cyclic loading. In this regard, CTDs are installed between beams and Chevron bracing. The results of experiments show that the dampers can reproduce the satisfactory performance observed in the tests on individual devices and as a result the hysteretic behavior of frames is very stable. Therefore this type of dampers has a potential for application in building frames. The experimental set up and results will be reported in detail in the paper.}, Keywords = {Yielding metallic dampers,Comb teeth damper,Energy Dissipation,Steel frames}, volume = {15}, Number = {5}, pages = {199-212}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-2930-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-2930-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Akbari, Jalal}, title = {Determination of Seismic Response of Structures based on Spectral Analysis using Elliptic Envelope}, abstract ={In the design or analysis of structures for seismic loads, the effects of forces acting simultaneously in a member must be considered. The most common case is the interaction of bending moments and axial load in columns. The usual response spectrum method provides the maximum values of individual responses, but the critical combination of these responses may not involve any of these maxima. In this Paper, the response-spectrum-based procedure for predicting the envelope that bounds two or more responses in a linear structure is implemented. It is shown that, for an assumed orientation of the principal axes along which the ground motion components are uncorrelated, this envelope is an ellipsoid. For the case when the orientation of the principal axes is unknown, a ‘‘supreme’’ envelope is derived, which corresponds to the most critical orientation of the axes. The response envelope can be superimposed on the capacity curve to determine the adequacy of a given design. In the commercial softwares such as SAP and ETABS seismic designs of structures are based on rectangular spectrums that they are usually over estimated ones. Therefore, implementation of such accurate envelope instead of rectangular one is felt in design softwares. In the design or analysis of structures for seismic loads, the effects of forces acting simultaneously in a member must be considered. The most common case is the interaction of bending moments and axial load in columns. The usual response spectrum method provides the maximum values of individual responses, but the critical combination of these responses may not involve any of these maxima. In this Paper, the response-spectrum-based procedure for predicting the envelope that bounds two or more responses in a linear structure is implemented. It is shown that, for an assumed orientation of the principal axes along which the ground motion components are uncorrelated, this envelope is an ellipsoid. For the case when the orientation of the principal axes is unknown, a ‘‘supreme’’ envelope is derived, which corresponds to the most critical orientation of the axes. The response envelope can be superimposed on the capacity curve to determine the adequacy of a given design. In the commercial softwares such as SAP and ETABS seismic designs of structures are based on rectangular spectrums that they are usually over estimated ones. Therefore, implementation of such accurate envelope instead of rectangular one is felt in design softwares. It is shown that, for an assumed orientation of the principal axes along which the ground motion components are uncorrelated, this envelope is an ellipsoid. For the case when the orientation of the principal axes is unknown, a ‘‘supreme’’ envelope is derived, which corresponds to the most critical orientation of the axes. The response envelope can be superimposed on the capacity curve to determine the adequacy of a given design. In the commercial softwares such as SAP and ETABS seismic designs of structures are based on rectangular spectrums that they are usually over estimated ones. Therefore, implementation of such accurate envelope instead of rectangular one is felt in design softwares.}, Keywords = {Rectangular envelope,Ellipsoid envelope,Seismic loads,Spectral response,Finite Elements}, volume = {15}, Number = {5}, pages = {213-222}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-8475-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-8475-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Mohammadi, Seyed Davood and MoharamzadeSaraye, khalil}, title = {The study of workability of lime on improvement of oil materials contaminated soils around the Tabriz oil refinery}, abstract ={This paper has investigated the affect of quicklime on engineering behaviour of contaminated soils from the Tabriz Oil Refinery. The type of contamination of studied soil was alkali hydrocarbons that had more than 14 carbon atoms (C14) and is classified in the solid phase. The laboratory tests that were undertaken are included the pH, Atterberg limits, standard compaction, uniaxial compressive strength and direct shear test. The quicklime is added to samples in 1%, 3%, 5%, and 7% of values based on weight percentages and the results of tests are investigated at curing time of 1, 3, 7, 14, 21 and 28 days. Base on the results of improvement process of contaminated soils using quicklime, the soil plasticity has been decreased. To assessment of accuracy of the affect of quicklime on contaminated soils, pH values are determined. Based on results, with addition of 5% of quicklime, the pH value was increased and then stabled that is showing the stopping of reaction between quicklime and soil. The pH values of improved contaminated clayey for 1%, 3% and 5% of added quicklime were 10.56, 11.87 and 12.52, respectively. Also, the pH values of improved silty sand for the same of added quicklime were 10.13, 11.63 and 12.17, respectively. According to the results of different researcher, the suitable pH for reaction between soil and quicklime is 12.4. Thus, adding of quicklime to the contaminated soils from Tabriz oil refinery is efficient for soil improvement. The results of compaction test indicated a decrease in maximum dry density and an increase in optimum water content for improved contamination soils. The results of compaction test are according to the results obtained by other researchers on uncontaminated soils. According to the values of UCS measured in the uniaxial compression strength tests on improved contaminated soils, there is a direct correlation between UCS and quicklime content. Base on the relationship of consistency and compression strength of soils, the CL and SM samples changes from soft consistency to hard consistency at the quicklime content of 5%. Regarding to results, the clayey soils with contamination of 66.4 mg/kg and the clayey soils with contamination more than 66.4 mg/kg, by 3% and 5% of added quicklime showed maximum strength, respectively. The optimum quicklime for contaminated silty sandy soil is not under the contamination effect and was 3% of values based on weight percentages. Comparing the uniaxial compressive strength of improved soil samples showed that the sample with low oil material contamination had high strength. Also, with increase of curing time, the uniaxial compressive strength has been increased. Direct shear test were carried out to find the effect of quicklime on strength parameters of contaminated soils from Tabriz oil refinery. The present results show a direct correlation between quicklime content and both internal friction angle and cohesion with increasing of quicklime content. The result indicate that oil material contaminated soils of Tabriz oil refinery can be stabilized satisfactory with addition of 3% and 5% quicklime.}, Keywords = {contaminated soil,quicklime,oil materials,hydrocarbons,strength parameters}, volume = {15}, Number = {5}, pages = {223-234}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-4799-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-4799-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {Nili, Mahmou}, title = {Assessing the Setting Times and Strength Development of Concrete containing Pozzolanic Materials}, abstract ={.Setting time is considered as an identification boundary of fresh and hardened of concrete. Initial set refers to a change from a fluid to a rigid state, accompanied by a rapid temperature rise in the body of concrete structures. The early hydration of C3A and C3S in presence of gypsum plays an important role in concrete rheology, and setting points of concrete. The final set, on the other hand, express the start of strength development. Knowledge of the initial setting time will help not only in determining the time available for the transportation, placement, and consolidation of concrete; but also in identifying the effectiveness of various admixtures and pozzolanic materials. The use of different types of pozzolanic materials has allowed to reduce the carbon dioxide emission per ton of produced cement. In the present work, the effects of silica fume, fly ash and slag on the setting times and strength development of different concrete mixtures are examined. The setting times were conducted accordance to ASTM C403. The Concrete specimens were prepared with three water cement ratios of 0.35, 0.45, and 0.55. Silica fume at 7%, fly ash at 15% and 25% and slag at 25% and 35%, by weight of cement, were used as replacement for cement. The results showed that the setting times of the concrete increased as water-cement ratio increased and the lowest setting times corresponded to the specimens with 0.35 water-cement ratio. The setting time of the specimens with water cement ratios of 0.45 and 0.55 increased by 10% and 18%, respectively, compared to that for 0.35. Using silica fume, fly ash and slag, as replacement for cement, retarded the setting times of the mixtures. The more replacement contents led to increase of setting times. The setting time of the fly ash specimens at 15% and 25% increased by 6% and 12%, whereas addition of slag at 25% and 35% retarded the setting time by 11% and 18%, respectively, compared to those for reference specimens with 0.45 water-cement ratio. Silica fume caused a slight increase of setting time by 5.5% compared to those without pozzolan materials. These may attributed to the low cement content in the pozzolanic specimens which resulted to the low friction surface between cement particles and on the other hand enhancement of effectiveness of the super-plasticizer in the mixtures which led to the increase of setting times. The results also indicated that silica fume, as a very fine supplementary cementitious material, enhanced both the early and later age strength. Fly ash and slag, as replacement for cement, increased the later stage strength of the specimens, but had a negative impact on the early- age strength. This may attributed to the low pozzolanic activity of these cementing materials in the early age, however in the later ages which calcium hydroxide content increased in the mixtures the secondary induced gel enhanced the compressive strength. A power relationship was proposed for the early age strength and the final setting time relationships}, Keywords = {Setting time of Concrete,compressive strength,Silica Fume,Fly Ash,Slag}, volume = {15}, Number = {5}, pages = {235-243}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-8208-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-8208-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} } @article{ author = {AlizadehArmaki, Hossein and Ghodsian, Masoud and Vaghefi, Mohamad and Khosravi, mojtab}, title = {Experimental Investigation of Flow and Scour Pattern around Submerged Attracting and Repelling T head Spur Dike}, abstract ={Abstract In this paper, flow and scour pattern around submerged and attracting T head spur dike in a straight bend has been studied. For measuring 3D velocities and bed topography, Vectrino+ and Point gauge machines were utilized. 3D velocities were measured in rigid bed state. Flow pattern experiments were conducted in a way in which after installation of spur dike in their place the sediments of the bed were flattened and then the sediments around the spur dike were covered with a thin layer of cement grout using anairbrush. After 6 hours, once the cement grout dried, the experiments are initiated. During velocity record times no scour was observed. In this research, electrical current was plotted in lateral and horizontal plans and flow pattern was studied. The findings of this research showed that the maximum scour in attracting spur dike is stronger than that of repelling spur dike and in both states it occurs in the edge of upstream wing of spur dike. Besides, flow pattern results suggest presence of a separation plane in upstream spur dike where a part of flow acts as up flow and another part acts as down flow. Moreover, flow and scour pattern in lateral, vertical, and different other plans were presented in this research. Furthermore, the finding of this study revealed that dimensions of downstream scour hole for attracting spur dike are larger. The length of this hole for attracting and repelling spur dike is 3.8 and 3.1 times to the effective length of spur dike. This suggests stronger effect of attracting spur dike on downstream flow. Besides, the width of scour hole in repelling spur dike (4.2 times to the effective length of spur dike) was larger than that of attracting spur dike (5 times to the effective length of spur dike). The length of sediment ridge in the attracting spur dike, due to its stronger effect on its downstream area, was larger (20 times to the effective length of spur dike) than that of repelling spur dike (16.4 times to the effective length of spur dike). Moreover, through this research it was found that the down flow area in upstream spur dike in repelling spur dike is larger than that of the attracting spur dike - 0.77 and 1.4 times to the effective length of spur dike for attracting and repelling spur dike, respectively. This length corresponds with the vastness of down flow. Also, the length of circulation zone in downstream of attracting and repelling spur dikes were 3.8 and 3.1 times to the effective length of spur dike, respectively and this length is in consistent with length of scour hole in downstream spur dike in vicinity of the spur dike. Finally, through this research, it was found that the center of clockwise vortex developed in downstream of repelling spur dike, compared to the attracting spur dike, is closer to the spur dike and due to initiation of deposition in a distance closer to the spur dike in repelling spur dike.}, Keywords = {Flow pattern,T head spur dike,submergence,attracting,repelling}, volume = {15}, Number = {5}, pages = {254-254}, publisher = {Tarbiat Modares University}, url = {http://mcej.modares.ac.ir/article-16-1234-en.html}, eprint = {http://mcej.modares.ac.ir/article-16-1234-en.pdf}, journal = {Modares Civil Engineering journal}, issn = {}, eissn = {2476-6763}, year = {2015} }