Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Moisture Susceptibility and Fracture Resistance of Hot Mix Asphalt Containing Treated Recycled Concrete Aggregate Moisture Susceptibility and Fracture Resistance of Hot Mix Asphalt Containing Treated Recycled Concrete Aggregate 7 19 12642 10.22034/23.5.1 FA A. Kavussi Tarbiat Modares University M. Bayzidi Tarbiat Modares University F. Kazemian Tarbiat Modares University Journal Article The construction industry produces substantial amounts of waste materials, which contribute to negative environmental impacts when disposed of in landfills. Recycling Construction and Demolition Waste (CDW) as secondary materials is an effective approach to reducing these negative effects. Recycled Concrete Aggregates (RCA) derived from distressed pavements, buildings, and concrete structures have potential for a variety of applications, including in asphalt mixes. This paper reports experimental research on the use of treated and untreated RCAs in preparing Hot Mix Asphalt (HMA). RCA materials were added in both treated and untreated form to HMA mixes. To improve the quality of recycled mixes, RCAs were treated with lime solutions. In order to improve quality of recycled mixes, RCAs were treated with lime solutions before that the recycled mixes were subjected to various tests. The treatment was applied to coarse RCA materials. The coarse RCAs were washed thoroughly, so that all noticeable impurities, including wood chips and other similar materials, were removed. These were then dried at ambient temperature for 24 h before that the treatment was applied. In order to reduce stripping susceptibility of the recycled asphalt mixtures, hydrated lime was added as a treatment additive. The addition of hydrated lime solution was beneficial due to, its abundance the convenience of application in HMA mixes. RCAs were impregnated in a 6% solution of hydrated lime for 24h at ambient temperature. Then these were dried at ambient temperature before being used in asphalt mixes. The physical and mechanical characteristics of the treated/untreated RCAs were determined. Asphalt mixtures were prepared that contained 25% and 50% RCAs of the size ranging from 4.75 to 12.5 mm. Various asphalt mixtures containing different amounts of RCAs were prepared. Moisture susceptibility of HMA mixes were evaluated using indirect tensile strength test (ITS). Fracture properties of mixes applying Semi-Circular Bending (SCB) were determined. SCB testing was performed according to ASTM D 8044 Standard testing method. Samples were prepared containing three different notches of 25, 32, and 38 mm. SCB samples were tested using a UTM machine. The loading mode as in monotonic compression at the speed of 0.5 mm/min. J-integral suggests as a criterion for resistance of materials to cracking. Testing was performed on HMA mixes treated and untreated samples. The results indicated that although treating RCAs might require more effort in production processing, significant benefits result in reducing moisture susceptibility and increasing fracture toughness of samples. It was also found that replacing virgin aggregates with RCA, improved fracture properties of HMA mixtures. The results indicated that with using RCA instead of conventional aggregates in asphalt mixes, has positive benefits for the environment and enhanced mechanical properties of HMA mixtures. A limited percentage of RCAs can be used in asphalt mixtures without significantly affecting performance of asphalt mixtures. The treatment resulted in reduced water absorption and increased fracture energy of mixes. Asphalt mixes containing 50% untreated RCA materials showed some moisture susceptibility while asphalt mixes containing 50% treated RCA showed improved moisture resistance. In conclusion, the study demonstrated that treating RCAs with hydrated lime solution improved the moisture susceptibility and fracture resistance of recycled HMA mixtures. Furthermore, utilizing recycled construction materials as secondary materials in asphalt mixes has significant environmental benefits. Future research can explore the potential use of various waste materials, including RCAs, in asphalt mixes. The construction industry produces substantial amounts of waste materials, which contribute to negative environmental impacts when disposed of in landfills. Recycling Construction and Demolition Waste (CDW) as secondary materials is an effective approach to reducing these negative effects. Recycled Concrete Aggregates (RCA) derived from distressed pavements, buildings, and concrete structures have potential for a variety of applications, including in asphalt mixes. This paper reports experimental research on the use of treated and untreated RCAs in preparing Hot Mix Asphalt (HMA). RCA materials were added in both treated and untreated form to HMA mixes. To improve the quality of recycled mixes, RCAs were treated with lime solutions. In order to improve quality of recycled mixes, RCAs were treated with lime solutions before that the recycled mixes were subjected to various tests. The treatment was applied to coarse RCA materials. The coarse RCAs were washed thoroughly, so that all noticeable impurities, including wood chips and other similar materials, were removed. These were then dried at ambient temperature for 24 h before that the treatment was applied. In order to reduce stripping susceptibility of the recycled asphalt mixtures, hydrated lime was added as a treatment additive. The addition of hydrated lime solution was beneficial due to, its abundance the convenience of application in HMA mixes. RCAs were impregnated in a 6% solution of hydrated lime for 24h at ambient temperature. Then these were dried at ambient temperature before being used in asphalt mixes. The physical and mechanical characteristics of the treated/untreated RCAs were determined. Asphalt mixtures were prepared that contained 25% and 50% RCAs of the size ranging from 4.75 to 12.5 mm. Various asphalt mixtures containing different amounts of RCAs were prepared. Moisture susceptibility of HMA mixes were evaluated using indirect tensile strength test (ITS). Fracture properties of mixes applying Semi-Circular Bending (SCB) were determined. SCB testing was performed according to ASTM D 8044 Standard testing method. Samples were prepared containing three different notches of 25, 32, and 38 mm. SCB samples were tested using a UTM machine. The loading mode as in monotonic compression at the speed of 0.5 mm/min. J-integral suggests as a criterion for resistance of materials to cracking. Testing was performed on HMA mixes treated and untreated samples. The results indicated that although treating RCAs might require more effort in production processing, significant benefits result in reducing moisture susceptibility and increasing fracture toughness of samples. It was also found that replacing virgin aggregates with RCA, improved fracture properties of HMA mixtures. The results indicated that with using RCA instead of conventional aggregates in asphalt mixes, has positive benefits for the environment and enhanced mechanical properties of HMA mixtures. A limited percentage of RCAs can be used in asphalt mixtures without significantly affecting performance of asphalt mixtures. The treatment resulted in reduced water absorption and increased fracture energy of mixes. Asphalt mixes containing 50% untreated RCA materials showed some moisture susceptibility while asphalt mixes containing 50% treated RCA showed improved moisture resistance. In conclusion, the study demonstrated that treating RCAs with hydrated lime solution improved the moisture susceptibility and fracture resistance of recycled HMA mixtures. Furthermore, utilizing recycled construction materials as secondary materials in asphalt mixes has significant environmental benefits. Future research can explore the potential use of various waste materials, including RCAs, in asphalt mixes.

https://mcej.modares.ac.ir/article_12642_845375903f6dbadda379558e905089f2.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Crack Detection in Concrete Structures Using Convolutional Neural Network Crack Detection in Concrete Structures Using Convolutional Neural Network 21 34 12643 10.22034/23.5.2 FA M. Seifollahi M.Sc., Graduated of Civil-Hydraulic Structures Eng., Faculty of Civil Eng., Univ. of Tabriz, Tabriz, Iran S. Abbasi M.Sc., Graduated of Civil-Hydraulic Structures Eng., Faculty of Eng., Univ. of Mohaghegh Ardabili, Ardabil, Iran M. Fahimi Farzam Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran R. Daneshfaraz Professor of Civil Eng., Faculty of Eng., Univ. of Maragheh, Maragheh, Iran Journal Article One of the active areas of research in concrete structure health monitoring is the detection of cracking in structural elements. Image classification and diagnosis have attracted the attention of many researchers nowadays. Due to the advancement of artificial neural networks and their fast processing, a convolution neural network has been established to detect these cracks. In this study, crack detection in concrete structures has been studied using a convolutional neural network, which can be generalized to all concrete structures for example dams, canals, bridges, shells, road infrastructure, foundations and concrete frames. Convolution neural network training was performed by the SGDM method with the ReLU activator function. Also, 250 iterations were employed for convolution neural network training, which gradually reduced the error rate and increased the accuracy of detecting cracked and uneaten concrete. The convolutional neural network is trained and validated with these 250 iterations. First, images with 32-pixel window dimensions are converted and separated. Then, the 32-pixel window, the 16-pixel, and the 8-pixel windows filter the images. A total of 3 stages of 32, 16, and 8-pixel filter images are analyzed and interpreted. During the training process, validation is performed every 20 iterations, and a diagram related to the accuracy of convolution network estimation and data classification error is drawn and completed. In convolutional neural networks, where the output is in pairs, the cracked and uncracked images of the network architecture are almost identical, differing only in minor specifications. The database of this research includes 20,000 images of cracked concrete and 20,000 uncracked concrete with dimensions of 3×227×227 pixels, 80% of it is used for training and the remaining 20% is used for validation of the convolution neural network. The accuracy of distinguishing cracked concrete from uncracked ones is about 98.16%, which is acceptable for operation and is considered practical. To evaluate the accuracy and performance of the proposed algorithm, each classification was performed against the overall accuracy, the confusion matrix was used for the validation data. According to the clutter matrix, 3861 images, in other words, 48.3% have been predicted to be correctly cracked, and 3992 images, equivalent to 49.9%, have been predicted to be correctly uncracked, and a total of 147 incorrect images have been predicted, which is equivalent to 1.8 percent. Images that are cracked and not accidentally cracked are predicted. They had crack lines in the corner of the image or cracks with a very small width, which the proposed convolutional neural network was mistaken for due to a very small crack width or crack position. Also, the results of the present study showed that the accuracy of this research has the best accuracy in less analysis time compared to previous studies. It should be noted that this method and its associated database can be used to produce a crack detection application on a smartphone, to be able to make a good initial estimate of the structure in question, such as a bridge or building after an unusual loading event, such as an earthquake or explosion. One of the active areas of research in concrete structure health monitoring is the detection of cracking in structural elements. Image classification and diagnosis have attracted the attention of many researchers nowadays. Due to the advancement of artificial neural networks and their fast processing, a convolution neural network has been established to detect these cracks. In this study, crack detection in concrete structures has been studied using a convolutional neural network, which can be generalized to all concrete structures for example dams, canals, bridges, shells, road infrastructure, foundations and concrete frames. Convolution neural network training was performed by the SGDM method with the ReLU activator function. Also, 250 iterations were employed for convolution neural network training, which gradually reduced the error rate and increased the accuracy of detecting cracked and uneaten concrete. The convolutional neural network is trained and validated with these 250 iterations. First, images with 32-pixel window dimensions are converted and separated. Then, the 32-pixel window, the 16-pixel, and the 8-pixel windows filter the images. A total of 3 stages of 32, 16, and 8-pixel filter images are analyzed and interpreted. During the training process, validation is performed every 20 iterations, and a diagram related to the accuracy of convolution network estimation and data classification error is drawn and completed. In convolutional neural networks, where the output is in pairs, the cracked and uncracked images of the network architecture are almost identical, differing only in minor specifications. The database of this research includes 20,000 images of cracked concrete and 20,000 uncracked concrete with dimensions of 3×227×227 pixels, 80% of it is used for training and the remaining 20% is used for validation of the convolution neural network. The accuracy of distinguishing cracked concrete from uncracked ones is about 98.16%, which is acceptable for operation and is considered practical. To evaluate the accuracy and performance of the proposed algorithm, each classification was performed against the overall accuracy, the confusion matrix was used for the validation data. According to the clutter matrix, 3861 images, in other words, 48.3% have been predicted to be correctly cracked, and 3992 images, equivalent to 49.9%, have been predicted to be correctly uncracked, and a total of 147 incorrect images have been predicted, which is equivalent to 1.8 percent. Images that are cracked and not accidentally cracked are predicted. They had crack lines in the corner of the image or cracks with a very small width, which the proposed convolutional neural network was mistaken for due to a very small crack width or crack position. Also, the results of the present study showed that the accuracy of this research has the best accuracy in less analysis time compared to previous studies. It should be noted that this method and its associated database can be used to produce a crack detection application on a smartphone, to be able to make a good initial estimate of the structure in question, such as a bridge or building after an unusual loading event, such as an earthquake or explosion.

https://mcej.modares.ac.ir/article_12643_08b1366504a4a5a1e679e2eaad38b595.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Macroscopic Modelling of the Concrete Shearwall with Asymmetrical Openings Macroscopic Modelling of the Concrete Shearwall with Asymmetrical Openings 35 49 12644 10.22034/23.5.4 FA M. Rezapour School of Civil EngineeringUniversity of Tehran M. Ghassemieh School of Civil EngineeringUniversity of Tehran Journal Article So far, various elements have been introduced for modeling concrete shear walls, which are classified into two general categories: microscopic and macroscopic. Compared to microscopic elements, macroscopic elements have less degrees of freedom and therefore require less time for analysis. This is the main advantage of these elements. In this article, a special type of macroscopic elements called Multiple-Vertical-Line-Element-Model (MVLEM) is used to model the concrete shear wall. These elements simulate the behavior of simple shear walls well, but when the opening is embedded in the wall, it does not work satisfactory. In this article, the modified MVLEM is used to model the concrete shear wall with asymmetric openings. For this purpose, an experimental concrete shear wall with asymmetric openings was selected and verified using the microscopic finite element method in Abaqus software. After validation, the shear wall was subjected to macroscopic modeling in Abaqus software. In this model, a method for macroscopic modeling of the coupling beam was proposed, which is based on the moment distribution diagram in the beam. When the wall is subjected to lateral loading, due to its geometric shape, the amount of moment on one side of the beam is almost zero and on the other side it is maximum. In simple concrete shear walls under lateral load, the amount of moment at the top of the wall is zero and at the bottom is maximum too. Therefore, the coupling beam can be considered as a simple shear wall. In the shear wall with asymmetric openings, the coupling beams are modeled as simple shear wall whose base is connected to the main wall. After modeling the coupling beam, three different methods were proposed to connect this beam to the main body of the wall. This research includes a microscopic wall with asymmetric openings, three macroscopic walls. The main difference between the macroscopic walls is in the way of connecting the beam to the shear wall, which is based on the difference in the stiffness of the connection. In order to check the accuracy of the proposed models, macroscopic and microscopic walls were subjected to static and quasi-dynamic loading. Based on the results of the aforementioned analyses, the models showed acceptable behavior. The amount of connection stiffness caused the behavior of macroscopic models to be different from each other. Based on the results, as the stiffness of the beam to the wall increases, the bearing capacity and elastic stiffness of the model increases and the ductility decreases. The degree of stiffness of the connection also affects the cyclic behavior of the wall. In such a way that the higher the stiffness of the connection, the greater the loss of carrying capacity is observed in cyclic loading. In the model whose stiffness is higher than the other models, it experiments a large resistance drop in the ninth and tenth cycles. In the model whose stiffness is less than the others, less drop is observed and it shows a soft behavior. The model in which the connection stiffness was in the middle level showed the most accuracy compared to other models. So far, various elements have been introduced for modeling concrete shear walls, which are classified into two general categories: microscopic and macroscopic. Compared to microscopic elements, macroscopic elements have less degrees of freedom and therefore require less time for analysis. This is the main advantage of these elements. In this article, a special type of macroscopic elements called Multiple-Vertical-Line-Element-Model (MVLEM) is used to model the concrete shear wall. These elements simulate the behavior of simple shear walls well, but when the opening is embedded in the wall, it does not work satisfactory. In this article, the modified MVLEM is used to model the concrete shear wall with asymmetric openings. For this purpose, an experimental concrete shear wall with asymmetric openings was selected and verified using the microscopic finite element method in Abaqus software. After validation, the shear wall was subjected to macroscopic modeling in Abaqus software. In this model, a method for macroscopic modeling of the coupling beam was proposed, which is based on the moment distribution diagram in the beam. When the wall is subjected to lateral loading, due to its geometric shape, the amount of moment on one side of the beam is almost zero and on the other side it is maximum. In simple concrete shear walls under lateral load, the amount of moment at the top of the wall is zero and at the bottom is maximum too. Therefore, the coupling beam can be considered as a simple shear wall. In the shear wall with asymmetric openings, the coupling beams are modeled as simple shear wall whose base is connected to the main wall. After modeling the coupling beam, three different methods were proposed to connect this beam to the main body of the wall. This research includes a microscopic wall with asymmetric openings, three macroscopic walls. The main difference between the macroscopic walls is in the way of connecting the beam to the shear wall, which is based on the difference in the stiffness of the connection. In order to check the accuracy of the proposed models, macroscopic and microscopic walls were subjected to static and quasi-dynamic loading. Based on the results of the aforementioned analyses, the models showed acceptable behavior. The amount of connection stiffness caused the behavior of macroscopic models to be different from each other. Based on the results, as the stiffness of the beam to the wall increases, the bearing capacity and elastic stiffness of the model increases and the ductility decreases. The degree of stiffness of the connection also affects the cyclic behavior of the wall. In such a way that the higher the stiffness of the connection, the greater the loss of carrying capacity is observed in cyclic loading. In the model whose stiffness is higher than the other models, it experiments a large resistance drop in the ninth and tenth cycles. In the model whose stiffness is less than the others, less drop is observed and it shows a soft behavior. The model in which the connection stiffness was in the middle level showed the most accuracy compared to other models.

https://mcej.modares.ac.ir/article_12644_2ac4692cb4f636b0769d2c291af6aa88.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Parametric Studies of Flat Cylindrical Friction Damper with Brakepad in Diagonal Brace Frame Under Cyclic Loading Parametric Studies of Flat Cylindrical Friction Damper with Brakepad in Diagonal Brace Frame Under Cyclic Loading 51 67 12645 10.22034/23.5.5 FA E. Soltani Baraftabi PhD candidate in Structural Engineering, Faculty of Civil Engineering, Islamic Azad University, Roudehen, iran. M. Alizadeh Elizei Assistant Professor, Faculty of Civil Engineering, Islamic Azad University, Roudehen, iran. R. Esmaeilabadi Assistant Professor, Faculty of Civil Engineering, Islamic Azad University, Roudehen, iran. Journal Article Nowadays, according to the performance of prefabricated friction dampers, which are expanding rapidly, they can increase the resistance of structural systems against earthquakes and depreciate the energies created by earthquakes in the structure. To control the vibrations of the structure at one level, it is very important to use passive control systems. But in the design at different levels, they cannot depreciate the incoming energy from the earthquake. Friction dampers focus on displacement variable and are mostly used in steel structures.The friction damper works according to the rules of a Coulomb damper or a friction brake that converts kinetic energy into heat through friction. In this article, a new type of friction damper called a flat cylindrical friction damper has been designed using brake pads in the diagonal brace, and the performance and seismic resistance of this system as well as the amount of energy loss have been investigated. The configuration of the damper is designed in such a way that grooved bolt connections and twin steel cables of different sizes and thicknesses are used.And the way the internal and external components are placed in the damper is such that innovation in tension and pressure has been created.Also, the movement of the cylindrical element in the damper has increased the amount of friction due to the presence of two types of brake pads with friction coefficients of 0.11 and 0.16 and bolt connections. It shows the performance of the damper by different sliding force at different friction levels. Geometric dimensions, thickness of brake pad, number of bolts, size of bolts, diameter of cables, sliding force, location of damper are among the variables investigated in this article. The role of brake pads, steel cables and bolt connections is very important and economically very affordable. The seismic performance of the intended frame has been investigated by 80 different modeling of the damper and the placement of the research variables. The desired optimal models were modeled in Abaqus software and analyzed and designed. The aim of this system is to reduce the relative horizontal displacement of floors and increase the amount of energy absorption. The increase in the axial force created in multiple loading cycles has always caused damage to the damper components and frames. In this article, it has been tried to use a special multi-level geometry that, in addition to reducing the axial force created in the damper, reduces the relative displacement of the frame, damages in the elements and increases the ductility.The results show that the friction surfaces of steel plates and brake pads is very high due to the displacement and damping of the cables And with the consumption of energy and its absorption by the damper in cyclic loads, displacement control is easily done. It also shows the seismic response of structures in terms of frame and damper displacement, base shear forces, energy absorption. Numerical study confirms the intended damper as an independent seismic resistant member in critical building structures when high seismic performance or seismic resilience in moderate and strong earthquakes is desirable. Nowadays, according to the performance of prefabricated friction dampers, which are expanding rapidly, they can increase the resistance of structural systems against earthquakes and depreciate the energies created by earthquakes in the structure. To control the vibrations of the structure at one level, it is very important to use passive control systems. But in the design at different levels, they cannot depreciate the incoming energy from the earthquake. Friction dampers focus on displacement variable and are mostly used in steel structures.The friction damper works according to the rules of a Coulomb damper or a friction brake that converts kinetic energy into heat through friction. In this article, a new type of friction damper called a flat cylindrical friction damper has been designed using brake pads in the diagonal brace, and the performance and seismic resistance of this system as well as the amount of energy loss have been investigated. The configuration of the damper is designed in such a way that grooved bolt connections and twin steel cables of different sizes and thicknesses are used.And the way the internal and external components are placed in the damper is such that innovation in tension and pressure has been created.Also, the movement of the cylindrical element in the damper has increased the amount of friction due to the presence of two types of brake pads with friction coefficients of 0.11 and 0.16 and bolt connections. It shows the performance of the damper by different sliding force at different friction levels. Geometric dimensions, thickness of brake pad, number of bolts, size of bolts, diameter of cables, sliding force, location of damper are among the variables investigated in this article. The role of brake pads, steel cables and bolt connections is very important and economically very affordable. The seismic performance of the intended frame has been investigated by 80 different modeling of the damper and the placement of the research variables. The desired optimal models were modeled in Abaqus software and analyzed and designed. The aim of this system is to reduce the relative horizontal displacement of floors and increase the amount of energy absorption. The increase in the axial force created in multiple loading cycles has always caused damage to the damper components and frames. In this article, it has been tried to use a special multi-level geometry that, in addition to reducing the axial force created in the damper, reduces the relative displacement of the frame, damages in the elements and increases the ductility.The results show that the friction surfaces of steel plates and brake pads is very high due to the displacement and damping of the cables And with the consumption of energy and its absorption by the damper in cyclic loads, displacement control is easily done. It also shows the seismic response of structures in terms of frame and damper displacement, base shear forces, energy absorption. Numerical study confirms the intended damper as an independent seismic resistant member in critical building structures when high seismic performance or seismic resilience in moderate and strong earthquakes is desirable.

https://mcej.modares.ac.ir/article_12645_1170a3c51dddd240000189d1884dfb1b.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 The Effects of Chelant Agent and Pulse Current on Enhancing Electrokinetic Remediation of Zn/Pb Contaminated Soil The Effects of Chelant Agent and Pulse Current on Enhancing Electrokinetic Remediation of Zn/Pb Contaminated Soil 69 84 12646 10.22034/23.5.6 FA F. Diba Department of Environment, College of Basic Sciences, Hamedan Branch, Islamic Azad University, Hamedan, Iran A. Goodarzi Faculty of Engineering, Hamedan Branch, Islamic Azad University, Hamedan, Iran S. Sobhan Ardakani Department of Environment, College of Basic Sciences, Hamedan Branch, Islamic Azad University, Hamedan, Iran M. Cheraghi Department of Environment, College of Basic Sciences, Hamedan Branch, Islamic Azad University, Hamedan, Iran B. Lorestani Department of Environment, College of Basic Sciences, Hamedan Branch, Islamic Azad University, Hamedan, Iran Journal Article Electrokinetic (EK) remediation is a very effective option for the soil decontamination; however, its efficiency depends on several factors. In the present study, the ability of Ethylene-diaminete-traacetic-acid (EDTA) and pulse current to improve this method for treating fine-grained soils containing heavy metals (HMs) was investigated. In so doing, first, the studied sample (mainly kaolinite) was mixed with a concentration of 5000 mg/kg zinc (Zn) and lead (Pb) and then subjected to an electrokinetic test with voltage gradient of 2 V(DC)/cm2 (in the form of continuous current and pulse) under 7, 14 and 28 days. The pulse current used was ON for 30 minutes and OFF for 10 minutes. In this process, different concentrations of EDTA (including a concentration of 0.1 M and 0.2 M) were also added to the anode and cathode reservoirs, separately and simultaneously. The obtained results showed that in the conditions of continuous current and without EDTA addtion (the common EK method), the EK removal efficiency, especially for lead, was not noticeable. According to the changes in the microstructure of soil sample and its electrical conductivity (EC) between the anode and the cathode electrodes, the reason can be ascribed to the decrease in current density due to precipitation of pollutants in the soil matrix and decresing the HMs transportation in the cathode side, as clearly confirmed by the XRD patterns and EC tests. In this case, increasing the test time from 7 to 28 days (despite more energy consumption) mainly caused the change of the pollution position in the around of anode side and the HMs removal in the cathode side is not enhanced, indicating that there is a limited effect (about 20%) on the total efficiency of the EK tests. It was found that the addition of EDTA only in the form of catholyte solution, even with the equivalent concentration of soil pollution, has a low effect on improving the electrokinetic response. On the other hand, the presence of the chelating agent in both reservoirs of the EK device, especially by applying the pulse current (with a frequency equal to 36 cycles/day) accelerates the treating process of EK remediation. In fact, as the results of macro-structural tests, scanning electron microscope (SEM) images and X-ray diffraction (XRD) analyses indicated, such improvement can be attributed to two major changes in soil-pollutant interaction. First of all, the presented EK method, by developing the penetration of the acid front towards the cathode side and limiting the polarization ability of clay particles, causes the formation of flocculation and reduces the soil ability to keep pollutants. Also, this system greatly reduces the contribution of insoluble phases through the processes of redissolution and formation of the stable complexes as well as generates a disturbance in the initial formation of metal precipitation due to the reduction in the hydrolysis reaction of the cathode part. Synergy of these changes has an prominent role in accelerating the EK mechanisms; so that compared to the conventional EK model, while reducing energy consumption by 25%, it can also increase the removal efficiency by nearly 2.6 times. Electrokinetic (EK) remediation is a very effective option for the soil decontamination; however, its efficiency depends on several factors. In the present study, the ability of Ethylene-diaminete-traacetic-acid (EDTA) and pulse current to improve this method for treating fine-grained soils containing heavy metals (HMs) was investigated. In so doing, first, the studied sample (mainly kaolinite) was mixed with a concentration of 5000 mg/kg zinc (Zn) and lead (Pb) and then subjected to an electrokinetic test with voltage gradient of 2 V(DC)/cm2 (in the form of continuous current and pulse) under 7, 14 and 28 days. The pulse current used was ON for 30 minutes and OFF for 10 minutes. In this process, different concentrations of EDTA (including a concentration of 0.1 M and 0.2 M) were also added to the anode and cathode reservoirs, separately and simultaneously. The obtained results showed that in the conditions of continuous current and without EDTA addtion (the common EK method), the EK removal efficiency, especially for lead, was not noticeable. According to the changes in the microstructure of soil sample and its electrical conductivity (EC) between the anode and the cathode electrodes, the reason can be ascribed to the decrease in current density due to precipitation of pollutants in the soil matrix and decresing the HMs transportation in the cathode side, as clearly confirmed by the XRD patterns and EC tests. In this case, increasing the test time from 7 to 28 days (despite more energy consumption) mainly caused the change of the pollution position in the around of anode side and the HMs removal in the cathode side is not enhanced, indicating that there is a limited effect (about 20%) on the total efficiency of the EK tests. It was found that the addition of EDTA only in the form of catholyte solution, even with the equivalent concentration of soil pollution, has a low effect on improving the electrokinetic response. On the other hand, the presence of the chelating agent in both reservoirs of the EK device, especially by applying the pulse current (with a frequency equal to 36 cycles/day) accelerates the treating process of EK remediation. In fact, as the results of macro-structural tests, scanning electron microscope (SEM) images and X-ray diffraction (XRD) analyses indicated, such improvement can be attributed to two major changes in soil-pollutant interaction. First of all, the presented EK method, by developing the penetration of the acid front towards the cathode side and limiting the polarization ability of clay particles, causes the formation of flocculation and reduces the soil ability to keep pollutants. Also, this system greatly reduces the contribution of insoluble phases through the processes of redissolution and formation of the stable complexes as well as generates a disturbance in the initial formation of metal precipitation due to the reduction in the hydrolysis reaction of the cathode part. Synergy of these changes has an prominent role in accelerating the EK mechanisms; so that compared to the conventional EK model, while reducing energy consumption by 25%, it can also increase the removal efficiency by nearly 2.6 times.

https://mcej.modares.ac.ir/article_12646_0702fc76fff062da3472e2794b6b6285.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Experimental Evaluation of the Strength Properties of Reactive Powder Concrete (RPC) Produced with Indigenous Materials Containing Industrial Steel Fibers Experimental Evaluation of the Strength Properties of Reactive Powder Concrete (RPC) Produced with Indigenous Materials Containing Industrial Steel Fibers 85 113 12647 10.22034/23.5.7 FA M. Gholizadeh Ph.D. Candidate of Engineering and Construction Management, Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran Journal Article Reactive powder concrete (RPC) is one of the ultra-high strength concretes with superior mechanical properties, which is made using cement and very fine powder materials such as quartz sand, microsilica, low amounts of water-cement ratio, super-lubricant and steel fibers. The main role of steel fibers in such concrete is actually a type of composite that has proper integrity and continuity and enables the use of concrete as a flexible material. The present study aimed to evaluate the effect of using different types of industrial steel fibers with different length (diameter) and percentages on the strength properties of RPC and to determine a series of experimental relationships for their estimation. To this end, by preparing three types of steel fibers with small diameters (group 1), medium (group 2) and large (group 3) and making a number of RPC samples using indigenous and common mineral materials, the strength characteristics of this type of concrete include compressive, bending and tensile strengths were determined at different ages. To investigate the effect of curing time as well as the diameter and percentage of steel fibers on the compressive strength of RPC, a total of 39 samples + 1 sample without fibers (control concrete) containing 1 to 5% of large steel fibers (with diameter of 0.8 mm), medium (with diameter of 0.6 mm) and small (with diameter of 0.4 mm) were made and their compressive strength was determined at different ages. In addition, to determine the bending and tensile strengths of RPC samples, a total of 18 standard RPC beam and cylindrical samples containing different percentages of medium diameter steel fibers were made. After these samples were cured, their 28-day strength was evaluated in comparison with the control samples. The results of compressive strength tests showed that by increase in the curing age, the strength of RPC increases in compared with the control sample (without fibers). The results of compressive strength tests showed that by reduce in the diameter of steel fibers, the 28-day compressive strength of RPC samples increased significantly and was determined to 423.5 MPa. In compared with the control sample (without fibers), the compressive strength is associated with a growth of 29.11%. Also, the optimal amount of medium steel fibers to achieve RPC with the highest strength was determined to be 2%. The results of flexural strength tests showed that 2% of group 1 steel fibers (with small diameter) and group 2 (with medium diameter) and 3% of group 3 steel fibers (with large diameter) as the optimal percentage of steel fibers to reach the maximum flexural strength in RPC. Therefore, the 28-day flexural strength of RPC samples containing 2%, 2%, and 3% of steel fibers of groups 1, 2, and 3, respectively, was equal to 40.9, 44.6, and 39.1 MPa. The highest tensile strength of RPC samples containing 1%, 2%, and 3% of steel fibers of groups 1, 2, and 3 compared to the control sample, was associated with a growth of 61.25%, 66.42%, and 68.21%, respectively. Also, the results of the tensile strength tests showed that the addition of group 2 steel fibers (medium) compared to the other two groups (small and large), had a greater impact on the growth percentage of tensile strength of RPC samples. Reactive powder concrete (RPC) is one of the ultra-high strength concretes with superior mechanical properties, which is made using cement and very fine powder materials such as quartz sand, microsilica, low amounts of water-cement ratio, super-lubricant and steel fibers. The main role of steel fibers in such concrete is actually a type of composite that has proper integrity and continuity and enables the use of concrete as a flexible material. The present study aimed to evaluate the effect of using different types of industrial steel fibers with different length (diameter) and percentages on the strength properties of RPC and to determine a series of experimental relationships for their estimation. To this end, by preparing three types of steel fibers with small diameters (group 1), medium (group 2) and large (group 3) and making a number of RPC samples using indigenous and common mineral materials, the strength characteristics of this type of concrete include compressive, bending and tensile strengths were determined at different ages. To investigate the effect of curing time as well as the diameter and percentage of steel fibers on the compressive strength of RPC, a total of 39 samples + 1 sample without fibers (control concrete) containing 1 to 5% of large steel fibers (with diameter of 0.8 mm), medium (with diameter of 0.6 mm) and small (with diameter of 0.4 mm) were made and their compressive strength was determined at different ages. In addition, to determine the bending and tensile strengths of RPC samples, a total of 18 standard RPC beam and cylindrical samples containing different percentages of medium diameter steel fibers were made. After these samples were cured, their 28-day strength was evaluated in comparison with the control samples. The results of compressive strength tests showed that by increase in the curing age, the strength of RPC increases in compared with the control sample (without fibers). The results of compressive strength tests showed that by reduce in the diameter of steel fibers, the 28-day compressive strength of RPC samples increased significantly and was determined to 423.5 MPa. In compared with the control sample (without fibers), the compressive strength is associated with a growth of 29.11%. Also, the optimal amount of medium steel fibers to achieve RPC with the highest strength was determined to be 2%. The results of flexural strength tests showed that 2% of group 1 steel fibers (with small diameter) and group 2 (with medium diameter) and 3% of group 3 steel fibers (with large diameter) as the optimal percentage of steel fibers to reach the maximum flexural strength in RPC. Therefore, the 28-day flexural strength of RPC samples containing 2%, 2%, and 3% of steel fibers of groups 1, 2, and 3, respectively, was equal to 40.9, 44.6, and 39.1 MPa. The highest tensile strength of RPC samples containing 1%, 2%, and 3% of steel fibers of groups 1, 2, and 3 compared to the control sample, was associated with a growth of 61.25%, 66.42%, and 68.21%, respectively. Also, the results of the tensile strength tests showed that the addition of group 2 steel fibers (medium) compared to the other two groups (small and large), had a greater impact on the growth percentage of tensile strength of RPC samples.

https://mcej.modares.ac.ir/article_12647_c97d0fb623809a739977f3cf12cba70c.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Effect Of anchors on FRP-Concrete Bond Behavior In EBR and EBROG Joints Effect Of anchors on FRP-Concrete Bond Behavior In EBR and EBROG Joints 115 127 12648 10.22034/23.5.8 FA M. Garakyaragh Isfahan University of Technology D. Mostofinejad Isfahan University of Technology Journal Article Fiber-reinforced polymer (FRP) sheets are lightweight and offer high tensile strength and durability under harsh environmental conditions. For this reason, FRP sheets are used extensively for the strengthening of concrete structures. Concrete structures reinforced with FRP composites commonly experience debonding failure of the reinforcement sheet before the tensile capacity of the FRP sheet has been fully utilized. One method used to prevent the debonding of FRP sheets is the use of FRP anchors. FRP anchors are made by rolling the FRP sheet and impregnating it with epoxy resin as a matrix. One end of the FRP anchor then is placed into a hole drilled in the concrete and the other end is fanned out across the FRP composite. In this research the bond technique, method of fan application, length of fan part, the anchor cross-section to reinforcement sheet cross-section ratio, and converting the failure mode to FRP rupture for straight FRP anchors were investigated. The FRP anchors were examined by the externally-bonded reinforcement (EBR) method and the externally-bonded reinforcement on grooves (EBROG) technique. To strengthen the specimens, FRP with a net thickness of 0.131 mm (SikaWrap-230C), a bond length of 70 mm, and a width of 48 mm was used. In the EBROG technique, two grooves with widths of 10 mm, depths of 10 mm, and spaced 20-mm apart were cut on the concrete surface. The matrix phase of the composite was Quantom-EPR 3301 epoxy resin. FRP composites were prepared by the wet lay-up method. To determine the bond behavior of FRP anchors, 15 single-lap shear tests on T-shaped specimens were conducted. The results showed that, in EBR method an increase in the anchor cross-section had a positive effect on the bond strength, so an increase of about 58% in bond strength of the EBR-60-3 specimens was observed. The failure mode in EBR specimens was debonding. The load-slip curves of the EBR joints showed that in the first part, the load increases sharply and linearly up to the initiation of debonding; In the second part, slippage increased significantly and the slope of the curve decreased. The use of straight FRP anchors significantly increased the bond strength and the final slip values compared to the control specimens. In the EBROG method, anchors with a cross-section ratio of twice eliminated the debonding and the failure mode for this group was the rupture of the FRP sheet. The load-slip curves for the EBROG method ascended and did not exhibit the almost two-line behavior of the EBR specimens. The load-slip curves consisted of an ascending branch with an initial slope that was greater than at the end. The slippage of the EBROG specimens was significantly lower than for the EBR specimens. This small amount of slip versus the high bond strength reveals the high stiffness of the bond. A comparison of the EBR and EBROG methods shows that the EBROG eliminated debonding at lower FRP fan and bond length values. Also, the bond strength of the EBROG specimens with FRP anchors increased by 136% compared to the EBR specimens. In this research, an embedment depth of 50 mm transferred stress to the concrete without pulling out the fibers. Fiber-reinforced polymer (FRP) sheets are lightweight and offer high tensile strength and durability under harsh environmental conditions. For this reason, FRP sheets are used extensively for the strengthening of concrete structures. Concrete structures reinforced with FRP composites commonly experience debonding failure of the reinforcement sheet before the tensile capacity of the FRP sheet has been fully utilized. One method used to prevent the debonding of FRP sheets is the use of FRP anchors. FRP anchors are made by rolling the FRP sheet and impregnating it with epoxy resin as a matrix. One end of the FRP anchor then is placed into a hole drilled in the concrete and the other end is fanned out across the FRP composite. In this research the bond technique, method of fan application, length of fan part, the anchor cross-section to reinforcement sheet cross-section ratio, and converting the failure mode to FRP rupture for straight FRP anchors were investigated. The FRP anchors were examined by the externally-bonded reinforcement (EBR) method and the externally-bonded reinforcement on grooves (EBROG) technique. To strengthen the specimens, FRP with a net thickness of 0.131 mm (SikaWrap-230C), a bond length of 70 mm, and a width of 48 mm was used. In the EBROG technique, two grooves with widths of 10 mm, depths of 10 mm, and spaced 20-mm apart were cut on the concrete surface. The matrix phase of the composite was Quantom-EPR 3301 epoxy resin. FRP composites were prepared by the wet lay-up method. To determine the bond behavior of FRP anchors, 15 single-lap shear tests on T-shaped specimens were conducted. The results showed that, in EBR method an increase in the anchor cross-section had a positive effect on the bond strength, so an increase of about 58% in bond strength of the EBR-60-3 specimens was observed. The failure mode in EBR specimens was debonding. The load-slip curves of the EBR joints showed that in the first part, the load increases sharply and linearly up to the initiation of debonding; In the second part, slippage increased significantly and the slope of the curve decreased. The use of straight FRP anchors significantly increased the bond strength and the final slip values compared to the control specimens. In the EBROG method, anchors with a cross-section ratio of twice eliminated the debonding and the failure mode for this group was the rupture of the FRP sheet. The load-slip curves for the EBROG method ascended and did not exhibit the almost two-line behavior of the EBR specimens. The load-slip curves consisted of an ascending branch with an initial slope that was greater than at the end. The slippage of the EBROG specimens was significantly lower than for the EBR specimens. This small amount of slip versus the high bond strength reveals the high stiffness of the bond. A comparison of the EBR and EBROG methods shows that the EBROG eliminated debonding at lower FRP fan and bond length values. Also, the bond strength of the EBROG specimens with FRP anchors increased by 136% compared to the EBR specimens. In this research, an embedment depth of 50 mm transferred stress to the concrete without pulling out the fibers.

https://mcej.modares.ac.ir/article_12648_1bff3f64f354e35b89422273e74cab8f.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Comparison Df discharge Capacity of Piano Key Weir with Ogee And Sharp Crest Weirs Comparison Df discharge Capacity of Piano Key Weir with Ogee And Sharp Crest Weirs 129 138 12649 10.22034/23.5.9 FA M. Ghodsian TMU H. Sohrabzadeh Anzani1 Journal Article In this research, comparison of piano key weir with sharp crested weir and ogee spillway is addressed. The experimentally measured values of discharge of piano key weir were compared with their corresponding computed values for ogee spillway and sharp crested weir. By using the dimensional analysis technique, dimensionless equation was obtained for discharge coefficient of rectangular piano key weir. Experiments were conducted in a rectangular channel with 10 m length, 0.75 m width and 0.9 m height. Experiments were conducted for various discharges and flow depths. All the experiments were conducted under free flow conditions at weir outlet. The discharge coefficients for the rectangular piano key weir were obtained based on the measured discharges and flow depth. The discharge of ogee spillway and sharp crested weir were estimated by using conventional weir equations. The variations of discharge versus total upstream head showed almost linear increasing trend of discharge with total head. The plotted data showed a decreasing trend of discharge coefficient with increasing relative total head. The obtained discharge coefficients for the rectangular piano key weir varied between 0.3 and 0.55. The average discharge coefficient for this weir was 0.4. At Ht/P = 0.28, the discharge through the rectangular piano key is almost 4 times the discharge of the ogee spillway. The average discharge of the piano key weir is about 2.5 times of the ogee spillway and about 3 times that of the sharp crest weir. The energy dissipation of the piano key weir is about 0.3. According to the results, the piano key weir performs better than the ogee spillway and the sharp crest weir. Therefore, in the circumstances that the design discharge of the dams has increased due to climate changes, the piano key weir is a better alternative to ogee spillway, due to its higher efficiency. In this research, comparison of piano key weir with sharp crested weir and ogee spillway is addressed. The experimentally measured values of discharge of piano key weir were compared with their corresponding computed values for ogee spillway and sharp crested weir. By using the dimensional analysis technique, dimensionless equation was obtained for discharge coefficient of rectangular piano key weir. Experiments were conducted in a rectangular channel with 10 m length, 0.75 m width and 0.9 m height. Experiments were conducted for various discharges and flow depths. All the experiments were conducted under free flow conditions at weir outlet. The discharge coefficients for the rectangular piano key weir were obtained based on the measured discharges and flow depth. The discharge of ogee spillway and sharp crested weir were estimated by using conventional weir equations. The variations of discharge versus total upstream head showed almost linear increasing trend of discharge with total head. The plotted data showed a decreasing trend of discharge coefficient with increasing relative total head. The obtained discharge coefficients for the rectangular piano key weir varied between 0.3 and 0.55. The average discharge coefficient for this weir was 0.4. At Ht/P = 0.28, the discharge through the rectangular piano key is almost 4 times the discharge of the ogee spillway. The average discharge of the piano key weir is about 2.5 times of the ogee spillway and about 3 times that of the sharp crest weir. The energy dissipation of the piano key weir is about 0.3. According to the results, the piano key weir performs better than the ogee spillway and the sharp crest weir. Therefore, in the circumstances that the design discharge of the dams has increased due to climate changes, the piano key weir is a better alternative to ogee spillway, due to its higher efficiency.

https://mcej.modares.ac.ir/article_12649_a0f92eb7964639eff4effce7901714bc.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Stochastic Analysis of Elastostatic Problems with Material Uncertainty Using Spectral Cell Method Stochastic Analysis of Elastostatic Problems with Material Uncertainty Using Spectral Cell Method 139 149 12650 10.22034/23.5.10 FA P. Zakian Department of Civil Engineering, Faculty of Engineering, Arak University 0000-0002-7252-9531 Journal Article Nowadays, advances in numerical methods have led to model real-life physical problems effectively. One of the difficulties in modelling the real-life physical problems is the geometric creation, because the mesh definition for a complex geometry is hard. In order to overcome this issue, one can use the spectral cell method due to employing a Cartesian mesh even for a complex geometry, such that constant Jacobian is considered for cells in the mesh. Spectral cell method is a combination of the spectral element method and the fictious domain concept, which uses an adaptive integration employing the quadtree or octree partitioning for the cells intersecting arbitrary boundaries as well as the cells including nonuniform material distribution. The interpolation functions of Lobatto family of spectral elements are utilized in spectral cell method. The spectral cell method is an efficient numerical method to solve the governing equations of continuum structures with complicated geometries. On the other hand, uncertainty naturally exists in the parameters of an engineering system (e.g., elastic modulus) and the input of that system (e.g., loading). Thus, the effects of those uncertainties are important in the response calculation of the engineering system. There are two types of uncertainty: aleatoric and epistemic. Aleatoric uncertainty is defined as an intrinsic variability of certain quantities, while epistemic uncertainty is defined as a lack of knowledge about certain quantities. An alternative to a deterministic modelling is a stochastic modelling, but analysing such a stochastic model is harder than a deterministic model having deterministic material properties and configuration. This is because the behaviour of the stochastic model is inevitably stochastic. Traditionally, Monte-Carlo simulation analyses a stochastic model by generating numerous realizations of the stochastic problem, and then solves each one like a deterministic problem. Nevertheless, Monte-Carlo simulation needs very high computational cost, particularly for large-scale problems. A systematic technique for uncertainty quantification is the stochastic finite element method providing a variety of statistical information. However, the method is computationally expensive with respect to the finite element method, and thus there are many developments for stochastic methods. Consequently, this paper presents stochastic form of spectral cell method to solve elastostatic problems considering material uncertainties. Therefore, uncertainty quantification of an elastostatic problem with geometrically complex domain can be modelled more efficiently than the traditional stochastic finite element method. In the proposed method, Fredholm integral equation is discretised using spectral cell method to solve Karhunen-Loève expansion used for the random field decomposition. Also, this method uses fewer cells than the stochastic finite cell method, and does not require formation of the eigenfunctions. In addition, Karhunen-Loève and polynomial chaos expansions are used to decompose the random field and to consider the response variability, respectively. Simple mesh generation, desirable accuracy and computational cost are the main features of the present method. In this study, two benchmark numerical examples are provided to demonstrate the efficiency and capabilities of the proposed method in the solution of elastostatic problems. The results are compared to those of stochastic finite element method and stochastic spectral element method. Nowadays, advances in numerical methods have led to model real-life physical problems effectively. One of the difficulties in modelling the real-life physical problems is the geometric creation, because the mesh definition for a complex geometry is hard. In order to overcome this issue, one can use the spectral cell method due to employing a Cartesian mesh even for a complex geometry, such that constant Jacobian is considered for cells in the mesh. Spectral cell method is a combination of the spectral element method and the fictious domain concept, which uses an adaptive integration employing the quadtree or octree partitioning for the cells intersecting arbitrary boundaries as well as the cells including nonuniform material distribution. The interpolation functions of Lobatto family of spectral elements are utilized in spectral cell method. The spectral cell method is an efficient numerical method to solve the governing equations of continuum structures with complicated geometries. On the other hand, uncertainty naturally exists in the parameters of an engineering system (e.g., elastic modulus) and the input of that system (e.g., loading). Thus, the effects of those uncertainties are important in the response calculation of the engineering system. There are two types of uncertainty: aleatoric and epistemic. Aleatoric uncertainty is defined as an intrinsic variability of certain quantities, while epistemic uncertainty is defined as a lack of knowledge about certain quantities. An alternative to a deterministic modelling is a stochastic modelling, but analysing such a stochastic model is harder than a deterministic model having deterministic material properties and configuration. This is because the behaviour of the stochastic model is inevitably stochastic. Traditionally, Monte-Carlo simulation analyses a stochastic model by generating numerous realizations of the stochastic problem, and then solves each one like a deterministic problem. Nevertheless, Monte-Carlo simulation needs very high computational cost, particularly for large-scale problems. A systematic technique for uncertainty quantification is the stochastic finite element method providing a variety of statistical information. However, the method is computationally expensive with respect to the finite element method, and thus there are many developments for stochastic methods. Consequently, this paper presents stochastic form of spectral cell method to solve elastostatic problems considering material uncertainties. Therefore, uncertainty quantification of an elastostatic problem with geometrically complex domain can be modelled more efficiently than the traditional stochastic finite element method. In the proposed method, Fredholm integral equation is discretised using spectral cell method to solve Karhunen-Loève expansion used for the random field decomposition. Also, this method uses fewer cells than the stochastic finite cell method, and does not require formation of the eigenfunctions. In addition, Karhunen-Loève and polynomial chaos expansions are used to decompose the random field and to consider the response variability, respectively. Simple mesh generation, desirable accuracy and computational cost are the main features of the present method. In this study, two benchmark numerical examples are provided to demonstrate the efficiency and capabilities of the proposed method in the solution of elastostatic problems. The results are compared to those of stochastic finite element method and stochastic spectral element method.

https://mcej.modares.ac.ir/article_12650_0bf04bee73b4f705123f3183a081ce28.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2024 01 21 Damage Control and Seismic Behavior of Self-centering RC Shear Wall with Replaceable Steel Member Utilizing Nonlinear Numerical Analysis Damage Control and Seismic Behavior of Self-centering RC Shear Wall with Replaceable Steel Member Utilizing Nonlinear Numerical Analysis 151 163 12651 10.22034/23.5.12 FA Fahimah Shahpory tarbiat modares university A. Tasnimi استاد مهندسی سازه، گروه مهندسی سازه و زلزله، دانشکده مهندسی عمران و محیط زیست، دانشگاه تربیت مدرس Journal Article The use of passive control systems to enhance the safety of structures and their attachments against earthquake-induced damages has gained attention in recent years. On the other hand, new seismic systems called "self-centering systems" have been developed that create a flag-shaped capacity curve by using pre-tension forces and creating a joint in the structural elements. The most important feature of the self-centering system is minimizing damage to the main structural elements and eliminating residual deformations. When these two approaches are combined, passive control systems are employed as energy dissipation devices within the self-centering reinforced concrete shear walls. In elf-centring reinforced concrete shear walls, the concrete at the corners of the walls is susceptible to damage and crushing of concrete due to concentrated compressive forces in those areas. Consequently, passive control elements are used to eliminate this damage and to make these areas more ductile, replacing the concrete. In this paper, the use of a replaceable steel member in the corners of a shear wall is investigated using numerical analysis. The steel member is installed as a passive control system to dissipate energy in the wall's foot and heel regions. Two similar walls, one with a replaceable member and the other without, are analyzed to compare the results. The results show that the wall with a replaceable member has better capacity, ductility, and energy dissipation than the wall without a replaceable member. The use of passive control systems to enhance the safety of structures and their attachments against earthquake-induced damages has gained attention in recent years. On the other hand, new seismic systems called "self-centering systems" have been developed that create a flag-shaped capacity curve by using pre-tension forces and creating a joint in the structural elements. The most important feature of the self-centering system is minimizing damage to the main structural elements and eliminating residual deformations. When these two approaches are combined, passive control systems are employed as energy dissipation devices within the self-centering reinforced concrete shear walls. In elf-centring reinforced concrete shear walls, the concrete at the corners of the walls is susceptible to damage and crushing of concrete due to concentrated compressive forces in those areas. Consequently, passive control elements are used to eliminate this damage and to make these areas more ductile, replacing the concrete. In this paper, the use of a replaceable steel member in the corners of a shear wall is investigated using numerical analysis. The steel member is installed as a passive control system to dissipate energy in the wall's foot and heel regions. Two similar walls, one with a replaceable member and the other without, are analyzed to compare the results. The results show that the wall with a replaceable member has better capacity, ductility, and energy dissipation than the wall without a replaceable member.

https://mcej.modares.ac.ir/article_12651_6fbb698655e6b0fdd299a543951c27ec.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Assessment of Seismic Performance of Eccentrically Braced Frames (EBF) by Fragility Curves Assessment of Seismic Performance of Eccentrically Braced Frames (EBF) by Fragility Curves 165 178 12652 10.22034/23.5 FA M. Fallah Asl Department of Earthquake Engineering, Faculty of Civil Engineering, Semnan University, Iran M. Gerami Professor of Department of Earthquake Engineering, Faculty of Civil Engineering, Semnan University, Iran A. Kheyroddin Professor of Faculty of Civil Engineering, Semnan University, Semnan, IRAN Journal Article Studies have been shown that conventional concentrically braced frames have undesirablity seismic performance since satisfy the displacement-controlled conditions in moment resistant frames are difficult. Then in the decades of 1970, researchers developed a system that had a good performance in strength and stiffness and in lateral displacement-controlled conditions either, the reason for this can be expressed that eccentrically braced frame (EBF) link acts as a fuse. Considering the limited research conducted in the field of investigating the seismic performance of eccentrically braced systems under strong ground motions by powerful dynamic nonlinear analyses, as well as knowing as much as possible the seismic behavior of these types of frames and choosing a suitable system to deal with seismic forces, the necessity of this research was felt. Therefore, in this paper, the seismic performance of 5, 10, and 15-story eccentrically braced frames with link beams with different types of performance in the ranges of shear, shear-flexural, and flexural performances has been investigated using incremental dynamic analyses (IDAs) under near-field ground motions. The results showed that, the performance of EBFs with Shear link in collapse prevention (CP) performance level are more desirable than EBFs with shear-flexural link and also performance of EBFs with shear-flexural link are more desirable than EBFs with Flexural link. Studies have been shown that conventional concentrically braced frames have undesirablity seismic performance since satisfy the displacement-controlled conditions in moment resistant frames are difficult. Then in the decades of 1970, researchers developed a system that had a good performance in strength and stiffness and in lateral displacement-controlled conditions either, the reason for this can be expressed that eccentrically braced frame (EBF) link acts as a fuse. Considering the limited research conducted in the field of investigating the seismic performance of eccentrically braced systems under strong ground motions by powerful dynamic nonlinear analyses, as well as knowing as much as possible the seismic behavior of these types of frames and choosing a suitable system to deal with seismic forces, the necessity of this research was felt. Therefore, in this paper, the seismic performance of 5, 10, and 15-story eccentrically braced frames with link beams with different types of performance in the ranges of shear, shear-flexural, and flexural performances has been investigated using incremental dynamic analyses (IDAs) under near-field ground motions. The results showed that, the performance of EBFs with Shear link in collapse prevention (CP) performance level are more desirable than EBFs with shear-flexural link and also performance of EBFs with shear-flexural link are more desirable than EBFs with Flexural link.

https://mcej.modares.ac.ir/article_12652_b252e54edce965ac4408effd7ce41fb7.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Optimization of P-nitrophenol-Contaminated Water by Non-thermal Plasma Technology and Ozonation by Response Surface Method Optimization of P-nitrophenol-Contaminated Water by Non-thermal Plasma Technology and Ozonation by Response Surface Method 179 193 12653 10.22034/23.5.13 FA A.h Khourshidi Master's student of Noshirvani University of Technology, Babol F. Qaderi Babol Noshirvani University of Technology Journal Article Industrial progress has ushered in the production of a diverse array of pollutants, encompassing both organic and non-biodegradable substances, such as hydrocarbon compounds derived from petroleum. As the discernible environmental ramifications of these pollutants continue to escalate, the quest for efficacious methodologies for wastewater remediation assumes paramount importance. Among the emergent technologies, plasma technology has garnered considerable acclaim due to its capacity to obliterate a myriad of pollutants. Plasma, which ensues from the application of high voltage to either a gaseous or liquid medium, engenders profoundly reactive species capable of dismantling intricate organic compounds. Similarly, ozone, an exceedingly potent oxidizing agent, has long commanded recognition for its aptitude in the degradation of pollutants. Its robust oxidative attributes render it an invaluable instrument in the realm of wastewater treatment. Ozone treatment entails the infusion of ozone gas into the contaminated aqueous medium, whereupon it engages pollutants in a transformative reaction, rendering them into less deleterious byproducts. By amalgamating the ozonation process with plasma technology, we can harness the merits of both modalities and achieve synergistic effects. This hybridized approach proffers several advantages vis-à-vis individual treatment methodologies, including augmented pollutant removal efficiency, diminished treatment duration, and amplified energy efficiency. The plasma-ozonation process exploits plasma's propensity for the generation of reactive species, capable of reacting with the organic constituents in wastewater. The ensuing ozonation phase augments the degradation of these constituents, engendering a more efficacious and comprehensive removal process. Prior investigations have scrutinized the efficacy of ozone and plasma in isolation for the eradication of p-nitrophenol, a ubiquitous organic pollutant encountered in industrial wastewater. These inquiries have methodically examined various parameters to ascertain their influence on pollutant removal efficiency. Factors such as applied voltage, ozone dosage, initial pH, reaction duration, and initial solution concentration have been subjected to meticulous scrutiny to optimize the treatment regimen. In the present study, we have devised an innovative mathematical model to probe the interplay between these two independent variables: plasma technology and ozonation. The model incorporates a quadratic equation and employs analysis of variance (ANOVA) to gauge the significance of each variable and discern the optimal conditions for pollutant removal. Through scrutiny of the model, we have ascertained that the pinnacle of removal efficiency, surpassing 95%, materializes under specific parameters. These parameters encompass an applied voltage of 14 kV, an oxygen flow rate of 6 L/min, an initial pH of 10, a reaction duration of 6 minutes, and an initial concentration of 200 mg/L. These revelations offer valuable insights into the operational parameters that yield superlative results for pollutant removal within the context of the plasma-ozonation process. The efficacious integration of ozone and plasma technologies in wastewater treatment proffers a promising panacea for the elimination of p-nitrophenol pollutants and sundry other organic constituents. By fine-tuning the process parameters in alignment with the model's recommendations, we can attain exceptional levels of pollutant elimination whilst concurrently minimizing energy consumption and treatment duration. This research significantly contributes to the perennial endeavors aimed at fashioning sustainable and efficient remedies for industrial wastewater treatment, endowing valuable perspectives for their future deployment and widescale application in industrial settings. Industrial progress has ushered in the production of a diverse array of pollutants, encompassing both organic and non-biodegradable substances, such as hydrocarbon compounds derived from petroleum. As the discernible environmental ramifications of these pollutants continue to escalate, the quest for efficacious methodologies for wastewater remediation assumes paramount importance. Among the emergent technologies, plasma technology has garnered considerable acclaim due to its capacity to obliterate a myriad of pollutants. Plasma, which ensues from the application of high voltage to either a gaseous or liquid medium, engenders profoundly reactive species capable of dismantling intricate organic compounds. Similarly, ozone, an exceedingly potent oxidizing agent, has long commanded recognition for its aptitude in the degradation of pollutants. Its robust oxidative attributes render it an invaluable instrument in the realm of wastewater treatment. Ozone treatment entails the infusion of ozone gas into the contaminated aqueous medium, whereupon it engages pollutants in a transformative reaction, rendering them into less deleterious byproducts. By amalgamating the ozonation process with plasma technology, we can harness the merits of both modalities and achieve synergistic effects. This hybridized approach proffers several advantages vis-à-vis individual treatment methodologies, including augmented pollutant removal efficiency, diminished treatment duration, and amplified energy efficiency. The plasma-ozonation process exploits plasma's propensity for the generation of reactive species, capable of reacting with the organic constituents in wastewater. The ensuing ozonation phase augments the degradation of these constituents, engendering a more efficacious and comprehensive removal process. Prior investigations have scrutinized the efficacy of ozone and plasma in isolation for the eradication of p-nitrophenol, a ubiquitous organic pollutant encountered in industrial wastewater. These inquiries have methodically examined various parameters to ascertain their influence on pollutant removal efficiency. Factors such as applied voltage, ozone dosage, initial pH, reaction duration, and initial solution concentration have been subjected to meticulous scrutiny to optimize the treatment regimen. In the present study, we have devised an innovative mathematical model to probe the interplay between these two independent variables: plasma technology and ozonation. The model incorporates a quadratic equation and employs analysis of variance (ANOVA) to gauge the significance of each variable and discern the optimal conditions for pollutant removal. Through scrutiny of the model, we have ascertained that the pinnacle of removal efficiency, surpassing 95%, materializes under specific parameters. These parameters encompass an applied voltage of 14 kV, an oxygen flow rate of 6 L/min, an initial pH of 10, a reaction duration of 6 minutes, and an initial concentration of 200 mg/L. These revelations offer valuable insights into the operational parameters that yield superlative results for pollutant removal within the context of the plasma-ozonation process. The efficacious integration of ozone and plasma technologies in wastewater treatment proffers a promising panacea for the elimination of p-nitrophenol pollutants and sundry other organic constituents. By fine-tuning the process parameters in alignment with the model's recommendations, we can attain exceptional levels of pollutant elimination whilst concurrently minimizing energy consumption and treatment duration. This research significantly contributes to the perennial endeavors aimed at fashioning sustainable and efficient remedies for industrial wastewater treatment, endowing valuable perspectives for their future deployment and widescale application in industrial settings.

https://mcej.modares.ac.ir/article_12653_3be14122a3c78d9070cae09a16adcbb1.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Detecting Damage in Steel Buildings through Ambient Vibration Tests Detecting Damage in Steel Buildings through Ambient Vibration Tests 195 209 12654 10.22034/23.5.14 FA M. Pourgholi Assistant Professor, Department of Civil Engineering, Islamic Azad University, Sarab, Iran. M. Ghanadi Assistant Professor, Department of Civil Engineering, Islamic Azad University, Sarab, Iran. M. Mohammadzadeh Gilarlue Assistant Professor, Department of Electrical Engineering, Islamic Azad University, Sarab, Iran. Journal Article Infrastructures such as bridges, buildings, pipelines, marine structures, etc., play an important role in human life. Since major disasters in these structures, such as the collapse of bridges or buildings, often result in many casualties, damages, and social and economic problems, most industrialized countries allocate significant funds to monitor their health. Failure detection strategies and continuous monitoring of the structure's condition, especially after natural and manufactured disasters, make necessary measures to be taken in the early stages of failure and can reduce the cost of maintenance and the possibility of collapse. Structural health monitoring methods often provide an opportunity to reduce maintenance, repair, and retrofit costs during the structure's life cycle. Most of the structural health monitoring methods proposed and implemented to identify possible damages depend on the structure's dynamic characteristics. One of the most practical methods, which uses the results of time domain system identification to detect failure, is the damage locating vector (DLV) method. The DLV method aims to identify load combinations that result in zero strain fields for damaged members in both healthy and damaged structures. To accomplish this, we find a vector in the null space of the difference between the plasticity matrices of the two structures. The singular value analysis method is used on the plasticity difference matrix to calculate this space. The method involves applying the space vectors to the healthy structure and recording the internal stresses of the members, which are then converted into weighted normal stress (WSI) using statistical tools. The member with a lower WSI is more likely to be damaged. Since truss structures are usually used in bridges, long-span structures, as well, as a wide range of steel buildings with simple and braced frames, this research uses the covariance-based random subspace optimal method in identifying the modal characteristics, which is very efficient in low excitations, has been taken into consideration to check and monitor health during operation. To investigate the capability of the DLV method in the damage detection of these structures, a 5-story residential building with a simple steel frame was subjected to the Centro earthquake. According to the desired damage scenario, the second and fifth floors were introduced as the damaged floors in this earthquake by applying a 30 and 50% reduction in the cross-section. To account for uncertainty in the data collection, we included the mean root square of the second sensor's data in the results for sensors 3 and 5. As a result of this uncertainty, the damping error between 5 and 10% has been shown in the damaged and healthy structure. Using the method (SSI_ORT), it was observed that two DLV vectors were extracted. Further, with the increasing uncertainty of the random vibration test results, it was observed that the extraction DLVs could extract the possible damaged elements with high accuracy. Next, the effect of input and output noises on the results obtained from the DLV method was investigated. This study found that by increasing the SNR of the outputs by 15% while increasing the error of the extracted modal characteristics, the extracted DlVs also lose sufficient accuracy in diagnosing structural damage. Infrastructures such as bridges, buildings, pipelines, marine structures, etc., play an important role in human life. Since major disasters in these structures, such as the collapse of bridges or buildings, often result in many casualties, damages, and social and economic problems, most industrialized countries allocate significant funds to monitor their health. Failure detection strategies and continuous monitoring of the structure's condition, especially after natural and manufactured disasters, make necessary measures to be taken in the early stages of failure and can reduce the cost of maintenance and the possibility of collapse. Structural health monitoring methods often provide an opportunity to reduce maintenance, repair, and retrofit costs during the structure's life cycle. Most of the structural health monitoring methods proposed and implemented to identify possible damages depend on the structure's dynamic characteristics. One of the most practical methods, which uses the results of time domain system identification to detect failure, is the damage locating vector (DLV) method. The DLV method aims to identify load combinations that result in zero strain fields for damaged members in both healthy and damaged structures. To accomplish this, we find a vector in the null space of the difference between the plasticity matrices of the two structures. The singular value analysis method is used on the plasticity difference matrix to calculate this space. The method involves applying the space vectors to the healthy structure and recording the internal stresses of the members, which are then converted into weighted normal stress (WSI) using statistical tools. The member with a lower WSI is more likely to be damaged. Since truss structures are usually used in bridges, long-span structures, as well, as a wide range of steel buildings with simple and braced frames, this research uses the covariance-based random subspace optimal method in identifying the modal characteristics, which is very efficient in low excitations, has been taken into consideration to check and monitor health during operation. To investigate the capability of the DLV method in the damage detection of these structures, a 5-story residential building with a simple steel frame was subjected to the Centro earthquake. According to the desired damage scenario, the second and fifth floors were introduced as the damaged floors in this earthquake by applying a 30 and 50% reduction in the cross-section. To account for uncertainty in the data collection, we included the mean root square of the second sensor's data in the results for sensors 3 and 5. As a result of this uncertainty, the damping error between 5 and 10% has been shown in the damaged and healthy structure. Using the method (SSI_ORT), it was observed that two DLV vectors were extracted. Further, with the increasing uncertainty of the random vibration test results, it was observed that the extraction DLVs could extract the possible damaged elements with high accuracy. Next, the effect of input and output noises on the results obtained from the DLV method was investigated. This study found that by increasing the SNR of the outputs by 15% while increasing the error of the extracted modal characteristics, the extracted DlVs also lose sufficient accuracy in diagnosing structural damage.

https://mcej.modares.ac.ir/article_12654_93fc5aed8c051ce4538e052cfe9f8692.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 5 2023 10 23 Probabilistic Assessment of Bearing Capacity of Strip Footings Seated on Heterogeneous Slopes Using Finite Element Limit Analysis (FELA) and Response Surface Method (RSM) Probabilistic Assessment of Bearing Capacity of Strip Footings Seated on Heterogeneous Slopes Using Finite Element Limit Analysis (FELA) and Response Surface Method (RSM) 211 222 12655 10.22034/23.5.3 FA M. Payan Assistant Professor, Department of Civil Engineering, Faculty of Engineering, University of Guilan. Journal Article This paper demonstrates the use of the response surface method (RSM) to carry out probabilistic assessment of the bearing capacity of shallow footings seated near naturally occurring heterogeneous slopes. The method substantially reduces the number of Monte Carlo simulations required to carry out cumbersome probabilistic slope stability analyses. A finite element limit analysis model based on the lower bound theorem is developed. The soil behaviour in this model has been assumed to follow the associated plastic flow rule by conforming to the perfectly plastic Mohr-Coulomb failure criterion. The model then used to generate a large synthetic database of numerical results for the bearing capacity of shallow foundations resting on inherently variable natural slopes. To this end, a permutation of the key parameters is formed and lower bound FELA-based limit loads are sought through optimization in MATLAB. A closed-form solution is formulated using RSM-based polynomials. The response surface method equations, which are acquired from least squares regression analyses, are used to carry out probabilistic Monte Carlo simulations. The results of the current study clearly show that the earth slope angle of 75o would give rise to the diminished factor of safety, or in other words, the substantially augmented probability of failure compared to the other two slope angles considered. On the other hand, the slope angle of 45o renders higher factor of safety and lower probability failure as compared to the slope angle of 60o. Moreover, it is observed that constructing the foundation at a farther distance relative to the slope would cause the probability of failure to substantially diminish while leading the reliability index to enhance for the majority of the safety factor scenarios considered. Indeed, targeting a particular probability of failure or a specific reliability index would demand smaller factor of safety for greater soil-footing distances. This paper demonstrates the use of the response surface method (RSM) to carry out probabilistic assessment of the bearing capacity of shallow footings seated near naturally occurring heterogeneous slopes. The method substantially reduces the number of Monte Carlo simulations required to carry out cumbersome probabilistic slope stability analyses. A finite element limit analysis model based on the lower bound theorem is developed. The soil behaviour in this model has been assumed to follow the associated plastic flow rule by conforming to the perfectly plastic Mohr-Coulomb failure criterion. The model then used to generate a large synthetic database of numerical results for the bearing capacity of shallow foundations resting on inherently variable natural slopes. To this end, a permutation of the key parameters is formed and lower bound FELA-based limit loads are sought through optimization in MATLAB. A closed-form solution is formulated using RSM-based polynomials. The response surface method equations, which are acquired from least squares regression analyses, are used to carry out probabilistic Monte Carlo simulations. The results of the current study clearly show that the earth slope angle of 75o would give rise to the diminished factor of safety, or in other words, the substantially augmented probability of failure compared to the other two slope angles considered. On the other hand, the slope angle of 45o renders higher factor of safety and lower probability failure as compared to the slope angle of 60o. Moreover, it is observed that constructing the foundation at a farther distance relative to the slope would cause the probability of failure to substantially diminish while leading the reliability index to enhance for the majority of the safety factor scenarios considered. Indeed, targeting a particular probability of failure or a specific reliability index would demand smaller factor of safety for greater soil-footing distances.

https://mcej.modares.ac.ir/article_12655_e4f037a7b0481cac2b28293cd99a559f.pdf