The Removal of Sodium Dodecyl Sulphate Anionic Surfactant from Wastewater Using UV/H2O2 Advanced Oxidation Process
N.
Ahmadi Mousa Abad
tmu
author
Gh.R
Moussavi
Tarbiat Modares University
author
text
article
2013
per
Surfactants are used to aid in cleaning equipment and surfaces by restaurants, dairy farms, and food processing plants and are among the basic constituents of organic pollutants in domestic as well as industrial wastewaters causing great environmental damages. Due to their high volume use, surfactant chemicals have the potential for broadscale release into aquatic and terrestrial environment. Surfactants can reach humans, animals and plants from the ground waters used as drinking water supplies. Besides the toxic effects of surfactants their existence in waters even under the toxic level causes many adverse effects on biological life. They cause pathological, physiological and biochemical effects on aquatic animals. A large number of surfactants, including the anionic types employed in the present study, have relatively low biodegradability. Due primarily to economic reasons, it is impractical to replace those low biodegradable surfactants in all household and industrial applications. In the past decades, ozonation and other advanced chemical oxidation has been suggested and investigated by many researchers for pretreatment of refractory surfactants. These investigators have found that the biodegradability of the refractory surfactants can be considerably enhanced by ozonation or photocatalytic treatment. Although effective in improving the biodegradability of refractory surfactants, strong oxidation by ozonation or photocatalytic treatment is a relatively costly method. An alternative advanced oxidation method which is as efficient and yet less expensive to implement would be highly desirable. A method meeting these requirements and deserving attention is the UV/H2O2 oxidation process. This method employs hydrogen peroxide (H2O2) and UV to form a strong oxidizing agent (hydroxyl radicals) during the oxidation process. Hydroxyl radicals have been known to possess a stronger oxidation potential than ozone, 2.8 V for OH and 2.07 V for ozone. This study carried out at a bench scale unit consisted of a batch UV reactor with a working volume of 80 ml to evaluate efficiency of UV/H2O2 AOP in the degradation of surfactant from synthetic wastewater.The effects of various parameters including reaction time, H2O2concentration was investigated. The concentration of model surfactant was determined by the acridin orange method.The
present study showed that the UV/H2O2 AOP have higher efficiency than singl UV and H2O2 processes for sodium dodecyl sulphate( SDS) anionic surfactant removal. In this process for the solution with a surfactant concentration of 700mg/L and H2O2 conentration of 0.5mMol, the removal efficiency of 92% was achieved with a reaction time of 30 minute. Also the degradation efficiency was found to be decreased by releasing in surfactant concentration. UV/H2O2 advanced oxidation process is capable of degrading the SDS surfactant from wastewater by high efficiency.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
1
10
http://mcej.modares.ac.ir/article_1849_4bee19473e071764f65cf75521121771.pdf
Inelastic Displacement Ratios for Structures on Firm Soil Sites Subjected to Iran Earthquakes Records
S.M. Parsaeian
Parsaeian
Earthquake Engineering and Seismology
author
, B.
Hosseini Hashemi
Earthquake Engineering and Seismology
author
A.R
Sarvghad Moghadam
Earthquake Engineering and Seismology
author
text
article
2013
per
In this paper, results of inelastic displacement ratios based on earthquake ground motions of Iran are presented. These ratios are calculated for single degree of freedom systems with elastic perfectly plastic behavior model and various strength reduction factors subjected to 204 earthquake ground motion records. These records are recorded on firm soil sites of Iran and have following characteristics 1) Recorded in earthquakes with seismic moment magnitude larger than 5, 2) At least one of the two horizontal components of records has peak ground acceleration larger than 50 cm/s2, 3) Recorded in free field stations so that potential soil-structure interaction effects omitted, 4) Records with hypo central distance larger than 15 km so that near fault effects omitted, 5) Recorded on soil conditions 1, 2 and 3 according to spectral ratio H/V of ground motions, 6) Records in which band pass range in correction process were at least between 0.33 to 20 Hz. 204 acceleration time histories including 70, 30 and 104 acceleration time histories related to soil condition 1, 2 and 3 respectively are used. In this statistical study, 422688 inelastic displacement ratios (related to 204 acceleration time histories, 296 period of vibration and 7 strength reduction factors) from response of SDOF systems with elastic perfectly plastic behavior model are calculated. Mean values of inelastic displacement ratios for each period of vibration and each strength reduction factor subjected to all 204 earthquake records and their dispersions are presented. The influence of period of vibration, strength reduction factor, soil condition, earthquake magnitude and hypocentral distance on inelastic displacement ratios are evaluated. This ratio in short period of vibration is larger than unit (maximum inelastic displacement larger than maximum elastic displacement) and for long period of vibration is close to unit (maximum inelastic displacement nearly equal to maximum elastic displacement). Soil condition effects on inelastic displacement ratio, for period of vibration larger than 1.5 second is very small and neglectable but neglecting of soil condition in periods between 0.4 and 1.5 second cause error up to 20 percent and for periods smaller than 0.4 second cause error up to 40 percent in estimation of inelastic displacement ratio. Neglecting of distance effects to focal of
earthquakes in estimation of inelastic displacement ratio, for period of vibration smaller than 1 second, causes error up to maximum 20 percent. This error increase when strength reduction factor increases. For period of vibration larger than 1 second, neglecting of distance effect doesn’t make considerable error. Neglecting of magnitude effects of earthquakes in estimation of inelastic displacement ratio, for period of vibration smaller than 1 second, causes error up to maximum 60 percent. This error increase when strength reduction factor increases. For period of vibration larger than 1 second, neglecting of distance effect doesn’t make considerable error.
By using of nonlinear regression analysis, a simplified equation based on mean results is calculated and Maximum inelastic displacement of single degree of freedom systems on Iran firm sites could be estimated using proposed equation and maximum elastic displacement demand. Finally, proposed equation is compared with C1 coefficient of target displacement in FEMA440.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
11
25
http://mcej.modares.ac.ir/article_1850_9cce03a4b855fa31a22db4170048b8cf.pdf
Designing Mathematical Routing Model of Hazardous Materials Transportation
(Case Study: the Fars Province Road Network)
A.
Azar
Tarbiat Modares University
author
M.
Saffarzadeh
Tarbiat Modares University
author
A.
Ehsani
Tarbiat Modares University
author
text
article
2013
per
In most cases, the place of producing and using hazardous materials is not the same and such materials should be transported from the production line to the consumption place. Because of the dangerous nature of such materials, safety indicators and criteria should be considered. More than 90% of hazardous materials transportation in Iran is by road. This shows the importance of attention to the safety factors. Although transportation departments or local governments are responsible for allocating acceptable paths that reduce risk, transportation companies usually look for some paths with lower travel times and fuel consumption. So many methods have been presented for designing the paths of hazardous materials transportation based on the trade -off between costs and risks of the transportation. Almost in all of them the national hazardous materials transport routing has been a decision for the matter in two levels, the government allocates a subset of the transport network to hazardous materials and the transportation corporations, choose their paths from this subset. However, the issue of justice in the distribution of risk is highly regarded in the states because feeling Injustice in received level of risk, might lead to public opposition to the routing of hazardous materials. Therefore in this research some routing models have been proposed. In the first mathematical model, we just consider the safety of paths and two major goals would be pursued. First we seek ways of minimizing risk in the whole studied path networks, and then this matter would be considered that the risk does not increase in each link more than certain amount, and in fact justice in the distribution of risk be established. This model was bi-level linear and transformed into a single-level mixed integer linear program by replacing the second level by its Karush–Kuhn–Tucker conditions and by linearizing the complementary constraints. Then we solve the MIP problem with a commercial optimization solver In the second model, in addition to the safety, the economic efficiency of the routes is considered. In fact, in this model, the results of the safety model will be used in a mathematical model with economic-safety approach. The real case study then has been used to evaluate mathematical In most cases, the place of producing and using hazardous materials is not the same and such materials should be transported from the production line to the consumption place. Because of the dangerous nature of such materials, safety indicators and criteria should be considered. More than 90% of hazardous materials transportation in Iran is by road. This shows the importance of attention to the safety factors. Although transportation departments or local governments are responsible for allocating acceptable paths that reduce risk, transportation companies usually look for some paths with lower travel times and fuel consumption. So many methods have been presented for designing the paths of hazardous materials transportation based on the trade -off between costs and risks of the transportation. Almost in all of them the national hazardous materials transport routing has been a decision for the matter in two levels, the government allocates a subset of the transport network to hazardous materials and the transportation corporations, choose their paths from this subset. However, the issue of justice in the distribution of risk is highly regarded in the states because feeling Injustice in received level of risk, might lead to public opposition to the routing of hazardous materials. Therefore in this research some routing models have been proposed. In the first mathematical model, we just consider the safety of paths and two major goals would be pursued. First we seek ways of minimizing risk in the whole studied path networks, and then this matter would be considered that the risk does not increase in each link more than certain amount, and in fact justice in the distribution of risk be established. This model was bi-level linear and transformed into a single-level mixed integer linear program by replacing the second level by its Karush–Kuhn–Tucker conditions and by linearizing the complementary constraints. Then we solve the MIP problem with a commercial optimization solver In the second model, in addition to the safety, the economic efficiency of the routes is considered. In fact, in this model, the results of the safety model will be used in a mathematical model with economic-safety approach. The real case study then has been used to evaluate mathematical
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
27
35
http://mcej.modares.ac.ir/article_1851_d1158fc6a1654d35acb2c61868e94371.pdf
Seismic Behavior of Soldier Pile Support Systems for Deep Excavations in Coarse Grain Alluvium
M.
Olyaei
tmu
author
S.Sh.
Yasrebi
tmu
author
M.
Emami
Tarbiat Modares University
author
text
article
2013
per
Soldier pile consists of the passive reinforcement (i.e., no post-tensioning) of existing ground by installing closely spaced steel bars (i.e., nails), which are subsequently encased in grout and transfer the loads from steel piles to soil. As construction proceeds from the top to bottom, concrete is also applied on the excavation face to provide continuity. Soldier pile is typically used to stabilize excavations adjustment to the buildings to prevent surface movement and cracks in the buildings where top-to-bottom construction is advantageous compared to other retaining wall systems. For certain conditions, soldier pile offers a viable alternative from the viewpoint of technical feasibility, construction costs, and construction duration when compared to ground anchor walls, which is another popular top-to bottom retaining system.
This paper addresses soil nails that are installed with a near horizontal orientation and are primarily subjected to tensile stresses together steel piles which act as cantilever beam with horizontal nails as supports. Soldier pile can be used for both temporary and permanent structures based on its service life or intended duration of use.
Soldier pile is a form of ground retention used when ground conditions comprise of dense to moderately dense soils such as coarse grain alluviums. Soldier pile systems with lateral nails are used in many excavation projects. This method is one of the appropriate support systems in deep excavations. However, most of the researches have been focused on the effects of wall height on the stability of excavations in static conditions, but with increasing of the use of soldier pile systems in seismic regions, the dynamic stability of these structures cannot be ignored. According to increasing of the usage of the soldier pile systems in seismic active zones, it’s important to study the dynamic behavior of these structures. Hence, in this paper, the seismic behavior of soldier pile systems in Tehran coarse grain alluvium has been investigated. The methodology is based on pseudo-static approach to equalize the dynamic analysis. The numerical modelings have been done according to Finite Difference Method (FDM) to this equalization.
Based on slope stability theory, it has been shown that the pseudo-static method is a suitable and simple approach to equalize dynamic behavior. Therefore, in this paper, a similar approach has been used to equalize dynamic behavior of soldier pile systems with considering a proposed pseudo-static coefficient. The failure surfaces in dynamic and pseudo-static
models efficiency. Network of this case study is the roads network of Fars province that it has 59 nodes and 80 arcs. Two groups of hazardous materials are considered and the risk factor is calculated for each group in all links. Each node can be the potential point of the demand or a point of supply. All paths can be used in both directions, and it has been assumed that the risk of passing hazardous material through the path between two nodes is equal for both directions. Risk index includes three factors, “population under effect”, “the environment assets”, and “the number and importance of road facilities across a link”. Results showed the best possible and the safest and most economical routes, would be obtained by solving the safety model and using the result of this model in the safety-economic model.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
37
49
http://mcej.modares.ac.ir/article_1852_6eab0bcbf6882b6813e7dcf38fef911c.pdf
Development of Pseudo-Static Method for Stability Analyses of Embankment Dams with egard to Foundation Effect
(Case study: Masjed Soleiman Dam)
A.
Ghanbari
Kharazmi University
author
M.
Davoodi
- International Institute of Seismology and Earthquake Eng
author
M.
Nasrollahtabar Ahangar
Kharazmi University
author
text
article
2013
per
Pseudo-static method is one of the oldest and simplest techniques for seismic stability analysis of embankment dams. Selection of appropriate seismic coefficients is the foremost part of analysis in Pseudo-static method. Previous researchers and design manuals often suggest constant values for selecting the seismic coefficient, regardless of geometry and stiffness of foundation and the dynamic characteristics of the structures.
In the proposed method, the seismic coefficient is a function of parameters α and β. Parameter β is indicative of acceleration amplification in the direction of the dam height, and is related to the geometrical specifications and material properties of the dam body and foundation. Therefore, β can be obtained through dynamic analysis. In this research, in order to obtain the effect of foundation on this parameter, a geometrical model of the Masjed Soleiman Dam has been analyzed dynamically using seismographs of earthquakes that occurred in different sites. Dam consultants used this value for the MDE of the Masjed Soleiman Dam site. Parameter was obtained by assessing the way in which the maximum acceleration varied at different points on the height of the dam. Also, the effect of far and near field records of earthquake are evaluated.
In this research, the safety factor in a wedge corresponding to the seismograph that causes the allowable displacement in that wedge is assumed to be equal to one. Thus, available seismographs were scaled to peak acceleration values and, using them, the wedge displacement values were calculated. The safety factor changes were then calculated using the seismograph that caused the allowable displacement in the wedge. These safety factors were assumed to be equal to one, and the dynamic safety factor for each wedge was determined by comparison of the results obtained from the original seismograph.
After comparison of the dynamic and pseudo-static safety factors, the desired safety factor was determined. The distribution of the horizontal acceleration corresponding to the safety factor was compared with the linear distribution of horizontal acceleration proposed in this article and the values of β were determined. Finally, a new technique to estimate the pseudo-static seismic coefficient is presented. Different conditions for foundation are assumed and results of analyses are evaluated. Results of this research imply that geometry, stiffness and analyses have been compared and based on the comparison of axial forces in the nails (as the most important factor of the stability), the equivalent horizontal acceleration coefficient for the model is proposed. The applied forces cause the reinforcement tension and the mobilized tension force can overcome the soil tension weakness. Thus, predicting mobilized forces in soldier pile nails during earthquake is very important.
The effects of most important parameters such as wall height, nail arrangements and soil types through numerical modeling of the soldier piles under dynamic loading by using FLAC have been investigated.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
51
61
http://mcej.modares.ac.ir/article_1853_350da7d93d057d114ee0a44c5e085a2b.pdf
Estimation of Overstrength Factor for Steel Plate
Shear Wall Structures
M.A.
Rahgozar
University of Isfahan
author
text
article
2013
per
Steel plate shear walls are very effective lateral load resisting systems with high lateral stiffness and ductility capacity. Although there are valuable experimental data available for such systems, most of the current seismic codes (including Iran’s Std. 2800) provide none or limited design provisions for such structural systems. One of the important seismic performance parameters of the structures is “over-strength factor” which is implicitly or explicitly part of seismic design base shear formulation. Most of the available data on this factor are obtained from experimental research and therefore results are limited to low-rise structures and/or with reduced scaled structures. The main objective in this research is to assess the over-strength factor for the steel shear walls. A closed-form-solution is proposed for obtaining this factor based on plate-frame interaction. It was found that the over-strength factors obtained by this method are in line with available experimental data and analytical results obtained in this study.
In derivation of this closed form solution the following assumptions are made: 1) beam-to-column connection is rigid, 2) SPSW behaviour is affected by the interaction of the steel plate and its surrounding frame members, 3) the first storey, usually the soft storey, controls ductility and strength of the structure in general, 4) the beam remains rigid and the plastic hinges only form in the columns, 5) stresses due to the bending action in the plate do not interfere with the stresses due to buckling in the plate, 6) stress-strain relationship of the steel plate and the steel frame members are elastic-perfectly plastic.
The experiments on SPSWs used in this study were conducted in four major universities three of which in Canada and USA. The analytical model used in this study for finite element verification of the results is a three storey building that is adopted from a previous study on SPSW structures which was based on SAC buildings.
It was found that the overstrength factor of a multistorey SPSW structure can be estimated by that of only the first storey of that. Also the results for the overstrength factor are not that sensitive to the angle of tension field in the plate. Moreover, it was found that this factor decreases with a decrease of plate thickness and the yield stress of the plate.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
63
78
http://mcej.modares.ac.ir/article_1854_00e675af0657094721f3f68b219a08e8.pdf
Property Improvement of Iranian LWAC: Investigation of Mechanical Properties and Stress-Strain Curve
M.
Khanzadi
University of Science and Technology
author
A.
Chalekaee
University of Science and Technology
author
text
article
2013
per
The potential use of leca and scoria aggregates available in Iran to produce high strength lightweight concrete has been studied. As a result of various concrete mixes with different lightweight aggregate amount, and using normal techniques, it was possible to obtain high quality lightweight concrete which is suitable for application in reinforced and prestressed concrete structures.In order to investigate the mechanical short term properties of this type of high strength concrete, different tests had done. The properties obtained include unit weight, compressive strength, static modulus of elasticity and poisson's ratio.Among the 28 day aged tested specimens, we could produce HSLWC containing scoria with 55 MPa compressive strength and 2070 kg/m3 weight.In LWC containing leca, a cube compressive strength of about 41 MPa with a unit weight of 1865 kg/m3 was reported.Static modulus of elasticity in concretes containingleca was between 15 to 19 GPa. It was between 17 to 19.5 GPa forconcretescontainingscoria. Some equations were offered to estimate static modulus of elasticity of these concretes based on their compressive strength and unit weight. The mechanical properties were improved by reducing the amount of lightweight aggregate. The results show that both scoria and leca were effective in improving the mechanical properties, but scoria could reach superior limits.Stress- strain curves of investigated concretes were studied and some recommendations are presented for estimating the curves.Stress-strain curves of investigated concretes are almost linear in ascending and descending branch.According to the observed coefficients, withincrease in concrete strength, the slope of the curve is reducedin comparison with modulus of elasticity. For scoria, the slope of curve is lower than modulus in all three mix designs, because of the higher modulus of elasticity of scoria aggregates, in comparison with leca.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
79
89
http://mcej.modares.ac.ir/article_1855_b97c0d84da586425a900490ee921f980.pdf
Bacteriological Modelling of Semnan Drinking Water Distribution
A.
Khodadi
Tarbiat Modares University
author
B.
Ayati
Tarbiat Modares University
author
F.
Bineshian
Tarbiat Modares University
author
text
article
2013
per
Microbial quality of potable water is of the most import guidelines of the World Health Organization (WHO). One of the main concerns of water supply and distribution network problems particularly in large cities is microbial growth in the pipelines that are significant non-compliers and repeatedly detect bacteria in finished drinking-water. In Iran, chlorine is mostly used as disinfection agent in conventional chemical treatment process in water treatment plants for supplying safe drinking water. This is done to maintain a residual concentration within a water distribution system for preventing the growth of pathogenic bacteria. Therefore, to meet water quality standards, it is necessary to maintain free chlorine residuals throughout the minimum and maximum levels for various reasons.
This study was conducted to examine the relationship between residual chlorine concentration, turbidity and microbial quality of water used for drinking in water distribution system of city of Semnan. Heterotrophic Plate Count (HPC) bacteria was used as an indicator for microbial quality and residual chloride concentration and turbidity were selected as the main parameters for determining correlation. In this research, for the first time Water-Gems as a comprehensive and easy-to-use water distribution modeling application bacteriological software with GIS system was employed as a tool to evaluate the microbial water quality in the network of Semnan city which is known as drawn area with limited water resources. Water-Gems is a multi-platform hydraulic and water quality modeling solution for water distribution systems with advanced interoperability, geospatial model-building, optimization, and asset management tools.
For the study, all required information from water supply system such as topographical references, type and diameter of pipelines, pressure head in the system and connections were imported in the software. Then sampling points were selected and 25200 samples were made for turbidity, residual chloride concentration and HPC bacteria. The results indicated that there is high correlation between free chloride residual, turbidity and HPC which means that lower chloride concentration caused the increase in turbidity and HPC number. This information can be used to formulate a bacterial growth control strategy.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
91
98
http://mcej.modares.ac.ir/article_1856_601b58279d2b4d36a56e714b31b9493f.pdf
Investigation on the Effect of Specimen Size and
Degradation of the Soils in the Strength Parameters
in Direct Shear Test
A.
Komak Panah
Tarbiat Modares University.
author
E.
Gangali
Tarbiat Modares University
author
text
article
2013
per
Although direct shear test has some limitations in test procedure and test results, still it is one the popular and prevalent test which is used in most laboratories for evaluation of shear strength parameters of soils. Most of direct shear test apparatus in laboratories are in the specimen dimensions ranging from 6*6 to 10*10 centimeters. There are very limited number of large direct shear apparatus in soil mechanics laboratories with specimen dimensions of 30*30 or larger. In order to perform direct shear tests on coarse graded materials, it is recommended to degrade material to finer gradation accepted by test standards relative to the box dimensions. It is clear that degradation by using exclusion or parallel method increases fine contents of soil samples in small shear boxes. When shear tests are performed on fine graded soil samples, the strength parameters become different from those of original coarse graded samples. Therefore it is necessary to investigate relation between these different parameters. The aim of this research is to compare the test results between shear strength parameters derived from both small and large direct shear tests. Three soil samples with 5,15 and 25 percent fine contents with three 80,90 and 100 percent relative densities were tested in large and small direct shear apparatus with box dimensions of 30*30*15 and 6*6*2.5 centimeters. Shear parameters were derived and compared carefully. The results indicated that degradation has great effect on the parameters. Also it was found out that degration by parallel method compared with exclusion method gives smaller parameters. It seams that the discrepancy is the result of fine content differences.
Comparing the fine contents in two samples prepared using both methods indicates that the fine content in samples produced by parallel method have greater amount.
Comparing resulting internal friction angles of original coarse graded material tested in large apparatus with the friction angles calculated from small degraded samples give larger values in the same relative densies. The increments are 2.5 degrees for degradation using exclusion method and 4.5 to 6 degrees using parallel method. Also the test result showed that the amount of increments increase in samples with higher amount of fine contents
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
99
106
http://mcej.modares.ac.ir/article_1857_c26d1a436be3c498181bffe7e754bb17.pdf
Evaluation of overstrength factor for steel plate shear wall structures
Mohammad Ali
Rahgozar
Assistant professor, Civil Engineering Department, University of Isfahan
author
text
article
2013
per
Steel plate shear walls are very effective lateral load resisting systems which have high lateral stiffness and high ductility capacity at the same time. Although there are valuable experimental data available for such systems, most of the current seismic codes (including Iran’s Standard NO. 2800) provide none or limited design provisions for such structural systems. One of the important seismic performance parameters of the structures is “over-strength factor” which is implicitly or explicitly part of seismic design base shear formulation. Most of the available data on this factor are obtained from experimental research and therefore results are limited to low-rise structures and/or with reduced scaled structures/specimens. The main objective in this research is to assess the over-strength factor for the steel plate shear walls. A closed-form-solution is proposed for obtaining this factor based on a plate-frame interaction. This formulation is on the basis of the assumption that steel plate yields first and then the frame undergoes into the inelastic range. Therefore, an important factor that controls the amount of overstrength in an steel plate shear wall panel is the ratio of the steel plate yield displacement to the that of the steel frame. The lower this ratio is the higher the overstrength factor would be. The results of four experiments from four different universities accross the world were considered. The results also include the geometric and material properties of the specimens as well as their hystresis behaviors under cyclic loading. From the hystresis loops one can obtain experimental overstrength factors. It was found that the over-strength factors obtained by this proposed method are in line with available experimental results obtained from these four tests. It was also found that as the steel plate thickness decreases, the overstrength factor increases. Also, as yield stress of the steel plare decreases, the overstrength factor increases. In other words, the softer the steel plate /panel becomes, the better the chance of the redistribuition of internal forces would be and therefore the higher the overstrength factor would become. Two sets of results and/or comparisons are made in this study. First for the purpose of vrification of the proposed closed form solution, one of the test specimens were extended and it was shown that for the certain condition of that the test the proposed formulation matched the experimental results however if the plate thickness were to increase the overstrength factor would drastically decreases. The second set of results were for steel plate/panels with real sizes and not small lab sizes. It was shown that for such moderate and realistic steel panel sizes and thicknesses the overstrength factor comes out to be about 1.3. In addition, an square like panel has the highest overstrength factor compared to a rectangle ones.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
63
78
http://mcej.modares.ac.ir/article_1862_d41d8cd98f00b204e9800998ecf8427e.pdf
PROPERTY IMPROVEMENT OF IRANIAN LWAC:INVESTIGATION OF MECHANICAL PROPERTIES AND STRESS-STRAIN CURVE
Mostafa
Khanzadi
Civil engineering Department,Iran University since and technology, Narmak, Tehran
author
Alireza
Chalekaee
Iran University of Science and Technology-Department of Civil Engineering
author
text
article
2013
per
The potential use of leca and scoria aggregates available in Iran to produce high strength lightweight concrete has been studied. As a result of various concrete mixes with different lightweight aggregate amount, and using normal techniques, it was possible to obtain high quality lightweight concrete which is suitable for application in reinforced and prestressed concrete structures, with a compressive strength higher than 40MPa at 28 days. In order to investigate the mechanical short term properties of this type of high strength concrete, different tests had done. The properties obtained include unit weight, compressive strength, splitting tensile strength, static modulus of elasticity and poisson's ratio. And, some relationships were given to estimate modulus of elasticity and splitting tensile strength of these concretes based on their compressive strength. The mechanical properties were improved by reducing the amount of lightweight aggregate. The results show that both scoria and leca were effective in improving the mechanical properties, but scoria could reach superior limits. Stress- strain curves of investigated concretes were studied and some recommendations are presented for estimating the curves. Based on results, curves were almost linear in ascending and descending branch.
Modares Civil Engineering journal
Tarbiat Modares University
2476-6763
12
v.
4
no.
2013
79
89
http://mcej.modares.ac.ir/article_1863_d41d8cd98f00b204e9800998ecf8427e.pdf