Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Comparative Study of Regression and Evolutionary Models for Prediction of Concrete Compressive Strength by Means of Concrete Cores Comparative Study of Regression and Evolutionary Models for Prediction of Concrete Compressive Strength by Means of Concrete Cores 7 20 12600 10.22034/23.2.1 FA K. Momeni Assistant Professor, Department of civil Engineering, Technical and Vocational TUV Tehran,Iran 0009-0003-9238-8873 S. Gholamrezaei Sarvelit Department of Elactrical Engineering,technical and Vocational TVU Journal Article Core testing is the most direct method to assess the in-situ concrete compressive strength in an existing structure, generally related to suspected construction malpractice or deficiency of concrete supply, to carry out the condition assessment of buildings before taking up repair and upgrading work. Although this test is quite simple to conduct, the results obtained may sometimes contain considerable errors because of the great variety of parameters involved. The general problems of core testing are well known. The factors including core diameter, length-to-diameter ratio (L/D), concrete age, aggregate characteristics, direction of coring and the moisture condition at the time of testing are known which affect the relationship between core strength and the corresponding standard cube or cylinder strength are fully reported by researchers. Another potential factor influencing the testing of cores is the presence of reinforcing bars within the core. The effects of the presence of steel bars on the strength of cores have been investigated by only a few researchers. Reinforcement bars passing through a core will increase the uncertainty of results and should be avoided wherever possible. Regression analysis and generalized GMDH network, whose structure is investigated using genetic algorithm and single-particle number optimization method for predicting the compressive strength of concrete using the results of coring tests with and without fittings. The form and ability of the multivariate linear regression models and the importance of regression coefficients based on the experimental data obtained for samples in two different processing conditions, in order to predict the cubic compressive strength of the concrete and using the input parameters including (1) the length to diameter ratio Core, (2) core diameter, (3) diameter, (4) number and (5) axial axial axis of the rebar in the core, (6) reinforcement of the rebar, and (7) core compressive strength as independent and input variables, as well as resistance Concrete pressure is evaluated as the response variable (or output of the models). This method is used for the GMDH neural network. The objective of the GMDH neural network method is to obtain a polynomial function that can be used to retrieve the output parameter by the input of the considered variables. The GMDH neural network can, after training, estimate the relationship between inputs and outputs in a polynomial, which depends on the accuracy of this polynomial on the data and structure of the network. The single-particle decomposition (SVD) method in the GMDH structure for the case where the number of equations is greater than that of unknowns, uses the least squares error method to solve such devices. The results showed that the models used have high ability to express the problem, since more than 95% of variations of response variables with fitted models in regression models and about 99% of changes in the response variable values in the GMDH model can be expressed. But in a comparative position, GMDH model with a general structure optimized with Genetic Algorithm and SVD has shown the best performance, with this superiority becoming noticeable, considering that about 75% of the data is involved in training the neural model. Subsequently, nonlinear regression models show a certain advantage over linear models. Core testing is the most direct method to assess the in-situ concrete compressive strength in an existing structure, generally related to suspected construction malpractice or deficiency of concrete supply, to carry out the condition assessment of buildings before taking up repair and upgrading work. Although this test is quite simple to conduct, the results obtained may sometimes contain considerable errors because of the great variety of parameters involved. The general problems of core testing are well known. The factors including core diameter, length-to-diameter ratio (L/D), concrete age, aggregate characteristics, direction of coring and the moisture condition at the time of testing are known which affect the relationship between core strength and the corresponding standard cube or cylinder strength are fully reported by researchers. Another potential factor influencing the testing of cores is the presence of reinforcing bars within the core. The effects of the presence of steel bars on the strength of cores have been investigated by only a few researchers. Reinforcement bars passing through a core will increase the uncertainty of results and should be avoided wherever possible. Regression analysis and generalized GMDH network, whose structure is investigated using genetic algorithm and single-particle number optimization method for predicting the compressive strength of concrete using the results of coring tests with and without fittings. The form and ability of the multivariate linear regression models and the importance of regression coefficients based on the experimental data obtained for samples in two different processing conditions, in order to predict the cubic compressive strength of the concrete and using the input parameters including (1) the length to diameter ratio Core, (2) core diameter, (3) diameter, (4) number and (5) axial axial axis of the rebar in the core, (6) reinforcement of the rebar, and (7) core compressive strength as independent and input variables, as well as resistance Concrete pressure is evaluated as the response variable (or output of the models). This method is used for the GMDH neural network. The objective of the GMDH neural network method is to obtain a polynomial function that can be used to retrieve the output parameter by the input of the considered variables. The GMDH neural network can, after training, estimate the relationship between inputs and outputs in a polynomial, which depends on the accuracy of this polynomial on the data and structure of the network. The single-particle decomposition (SVD) method in the GMDH structure for the case where the number of equations is greater than that of unknowns, uses the least squares error method to solve such devices. The results showed that the models used have high ability to express the problem, since more than 95% of variations of response variables with fitted models in regression models and about 99% of changes in the response variable values in the GMDH model can be expressed. But in a comparative position, GMDH model with a general structure optimized with Genetic Algorithm and SVD has shown the best performance, with this superiority becoming noticeable, considering that about 75% of the data is involved in training the neural model. Subsequently, nonlinear regression models show a certain advantage over linear models.

https://mcej.modares.ac.ir/article_12600_9e411b2d0cbcc1d9cd8775e89e96774f.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Evaluation of Cyclic Behavior of Steel Plate Shearwall Equipped with Added Damping and Stiffness (ADAS) Dampers Evaluation of Cyclic Behavior of Steel Plate Shearwall Equipped with Added Damping and Stiffness (ADAS) Dampers 21 37 12601 10.22034/23.2.2 FA I. Tolouei Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran A. Maleki Assistant Professor, Department of Civil Engineering, Maragheh Branch, Islamic Azad University, Maragheh, Iran M. Lotfollahi-Yaghin Professor, Department of Civil Engineering, University of Tabriz, Tabriz, Iran 0000-0003-2628-4083 Journal Article In the present study, the cyclic behavior of steel plate shear wall of a three-story steel frame equipped with added damping and stiffness (ADAS) dampers was evaluated. In this study, with the aim of investigating and improving the performance of the steel plate shear wall against lateral forces, the proposed dampers were applied in the distance between the columns and the steel plate shear wall infill plates. The parameters studied include the thickness of the damper sheet (8, 10, 12, 14 and 16 mm) and the thickness of the infill plate (3, 4, 5 and 6 mm) respectively. Evaluation of cyclic behavior of steel plate shear wall was performed using finite element method via ABAQUS software and the loading protocol based on ATC-24 was applied. In order to verify, the experimental specimen was simulated by ABAQUS software and it was observed that the experimental specimen and the finite element model are in good conformation and the finite element model can be applied to study and compare the parameters considered in this study such as energy dissipation, strength, stiffness and ductility. The results showed that as the thickness of the damper sheet increased, the energy consumption in the steel plate shear wall system increased from 12 to 66 percent compared to the model without dampers. Also, by reducing and increasing the thickness of the infill plates in the second and third floors compared to the model without dampers, we saw an increase in energy consumption from 52 to 64 percent compared to the model without dampers, which indicates the good performance of the dampers. The strength of the steel plate shear wall system increased from 2.40 to 3.14 times by considering different thicknesses for the damper compared to the model without damper, and further by considering the infill plates for the steel plate shear wall system. We saw an increase in strength from 2.30 to 2.81 times compare to the model without damper. The stiffness level of each steel plate shear wall model was investigated and compared, and we saw an increase in stiffness from 76 to 99 percent compared to the model without damper. Also, considering the thickness of different infill plates for the steel plate shear wall system, the stiffness increased from 82 to 98 percent compared to the model without damper. As the thickness of the damper sheets increased, the ductility increased from 2.32 to 2.55 times compare to the model without damper. Also, considering the thickness of different infill plates for the steel plate shear wall system, we saw an increase in strength from 2.29 to 2.55 times compare to the model without damper. Further, by examining the hysteresis curves and the hysteresis damping ratio of different models, it was evident that the models equipped with dampers are significantly superior to the models without dampers, and as the thickness of the dampers increased, the area under the curve of each model increased. As a result, the larger this level is, it indicates that the member is more malleable and has the ability to absorb more energy. Finally, the performance of the proposed dampers was investigated along with the damper failure mechanism. The results showed that ADAS dampers with their special deformations, significantly increase energy consumption and make the steel plate shear wall more malleable and by absorbing a large amount of energy they reduced the force applied to the main components and prevented the destruction of the steel plate shear wall. In the present study, the cyclic behavior of steel plate shear wall of a three-story steel frame equipped with added damping and stiffness (ADAS) dampers was evaluated. In this study, with the aim of investigating and improving the performance of the steel plate shear wall against lateral forces, the proposed dampers were applied in the distance between the columns and the steel plate shear wall infill plates. The parameters studied include the thickness of the damper sheet (8, 10, 12, 14 and 16 mm) and the thickness of the infill plate (3, 4, 5 and 6 mm) respectively. Evaluation of cyclic behavior of steel plate shear wall was performed using finite element method via ABAQUS software and the loading protocol based on ATC-24 was applied. In order to verify, the experimental specimen was simulated by ABAQUS software and it was observed that the experimental specimen and the finite element model are in good conformation and the finite element model can be applied to study and compare the parameters considered in this study such as energy dissipation, strength, stiffness and ductility. The results showed that as the thickness of the damper sheet increased, the energy consumption in the steel plate shear wall system increased from 12 to 66 percent compared to the model without dampers. Also, by reducing and increasing the thickness of the infill plates in the second and third floors compared to the model without dampers, we saw an increase in energy consumption from 52 to 64 percent compared to the model without dampers, which indicates the good performance of the dampers. The strength of the steel plate shear wall system increased from 2.40 to 3.14 times by considering different thicknesses for the damper compared to the model without damper, and further by considering the infill plates for the steel plate shear wall system. We saw an increase in strength from 2.30 to 2.81 times compare to the model without damper. The stiffness level of each steel plate shear wall model was investigated and compared, and we saw an increase in stiffness from 76 to 99 percent compared to the model without damper. Also, considering the thickness of different infill plates for the steel plate shear wall system, the stiffness increased from 82 to 98 percent compared to the model without damper. As the thickness of the damper sheets increased, the ductility increased from 2.32 to 2.55 times compare to the model without damper. Also, considering the thickness of different infill plates for the steel plate shear wall system, we saw an increase in strength from 2.29 to 2.55 times compare to the model without damper. Further, by examining the hysteresis curves and the hysteresis damping ratio of different models, it was evident that the models equipped with dampers are significantly superior to the models without dampers, and as the thickness of the dampers increased, the area under the curve of each model increased. As a result, the larger this level is, it indicates that the member is more malleable and has the ability to absorb more energy. Finally, the performance of the proposed dampers was investigated along with the damper failure mechanism. The results showed that ADAS dampers with their special deformations, significantly increase energy consumption and make the steel plate shear wall more malleable and by absorbing a large amount of energy they reduced the force applied to the main components and prevented the destruction of the steel plate shear wall.

https://mcej.modares.ac.ir/article_12601_47af10edfc4c96329531345635a4baa9.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Seismic Behavior of Precast Self-Centering Bridge Piers Seismic Behavior of Precast Self-Centering Bridge Piers 39 57 12602 10.22034/23.2.3 FA M. Sam Daliri Babol Noshirvani University of Technology H. Yousefpour Babol Noshirvani University of Technology H. Khosravi Babol Noshirvani University of Technology Journal Article Accelerated construction methods are extensively used worldwide to reduce the negative impacts of bridge construction on urban traffic. These methods usually require prefabricating parts of the bridge off-site, which reduces on-site construction time and improves the quality and safety of construction. While the use of precast elements for bridge decks is relatively common, using precast elements for bridge piers is a recent development, especially in high-seismicity regions. Prefabrication of bridge piers can further expedite the construction of bridges. Moreover, the use of precast elements can be combined with a self-centering capability, through which the earthquake-induced damage and cost of post-earthquake repairs are greatly reduced. Despite a number of previous numerical and experimental studies on the behavior of precast, self-centering bridge piers, limited information is available on the selection of design parameters for such piers, and important decisions such as the prestressing force needed to achieve suitable seismic behavior remains to a large extent uncertain. This study aims to investigate the seismic behavior of concrete bridges consisting of precast self-centering piers, in which unbonded, post-tensioned tendons are used for self-centering and reinforcing steel is used to dissipate earthquake energy. A two-dimensional numerical model was developed in OpenSees to simulate the behavior of concrete bridges consisting of precast self-centering piers. The model consisted of fiber elements to model concrete and mild steel, as well as truss elements to model unbonded post-tensioning steel. The model also involved the use of zero-length sections to model the bond-slip behavior of mild steel bars. The modeling approach was validated based on experimental results available in the literature on cyclic loading of four bridge piers. To evaluate the effects of various design parameters on the behavior of precast segmental bridge piers, 9 segmental piers with different percentages of prestressing force and reinforcing steel were designed according to 2017 AASHTO LRFD Bridge Design Specifications. All piers were designed to possess similar nominal flexural capacities. The piers were then subjected to monotonic, cyclic, and dynamic time history analyses. The results showed the positive effects of prestressing in delaying cracking and reducing the residual drifts of precast bridge piers. Increasing the prestressing force ratio up to 10 percent of compressive strength of the pier cross section was observed to improve the overall seismic behavior of the structure, above which a further increase in the prestressing level may result in a diminished performance. The optimal value for the prestressing force ratio, which resulted in the most desirable behavior for cyclic and dynamic loadings was therefore found between 0.1 and 0.15. In piers with a prestressing ratio above 0.15, a decrease was observed in the area of hysteresis loops, which was accompanied by negative stiffness of the base shear versus drift curve. Moreover, the residual drift of the pier increased when prestressing ratios greater than 0.15 were used. The maximum drift of the structure was found to be insensitive to the prestressing force ratio. The results of this study are of great value for optimal design of precast, self-centering bridge piers in high-seismicity regions. Accelerated construction methods are extensively used worldwide to reduce the negative impacts of bridge construction on urban traffic. These methods usually require prefabricating parts of the bridge off-site, which reduces on-site construction time and improves the quality and safety of construction. While the use of precast elements for bridge decks is relatively common, using precast elements for bridge piers is a recent development, especially in high-seismicity regions. Prefabrication of bridge piers can further expedite the construction of bridges. Moreover, the use of precast elements can be combined with a self-centering capability, through which the earthquake-induced damage and cost of post-earthquake repairs are greatly reduced. Despite a number of previous numerical and experimental studies on the behavior of precast, self-centering bridge piers, limited information is available on the selection of design parameters for such piers, and important decisions such as the prestressing force needed to achieve suitable seismic behavior remains to a large extent uncertain. This study aims to investigate the seismic behavior of concrete bridges consisting of precast self-centering piers, in which unbonded, post-tensioned tendons are used for self-centering and reinforcing steel is used to dissipate earthquake energy. A two-dimensional numerical model was developed in OpenSees to simulate the behavior of concrete bridges consisting of precast self-centering piers. The model consisted of fiber elements to model concrete and mild steel, as well as truss elements to model unbonded post-tensioning steel. The model also involved the use of zero-length sections to model the bond-slip behavior of mild steel bars. The modeling approach was validated based on experimental results available in the literature on cyclic loading of four bridge piers. To evaluate the effects of various design parameters on the behavior of precast segmental bridge piers, 9 segmental piers with different percentages of prestressing force and reinforcing steel were designed according to 2017 AASHTO LRFD Bridge Design Specifications. All piers were designed to possess similar nominal flexural capacities. The piers were then subjected to monotonic, cyclic, and dynamic time history analyses. The results showed the positive effects of prestressing in delaying cracking and reducing the residual drifts of precast bridge piers. Increasing the prestressing force ratio up to 10 percent of compressive strength of the pier cross section was observed to improve the overall seismic behavior of the structure, above which a further increase in the prestressing level may result in a diminished performance. The optimal value for the prestressing force ratio, which resulted in the most desirable behavior for cyclic and dynamic loadings was therefore found between 0.1 and 0.15. In piers with a prestressing ratio above 0.15, a decrease was observed in the area of hysteresis loops, which was accompanied by negative stiffness of the base shear versus drift curve. Moreover, the residual drift of the pier increased when prestressing ratios greater than 0.15 were used. The maximum drift of the structure was found to be insensitive to the prestressing force ratio. The results of this study are of great value for optimal design of precast, self-centering bridge piers in high-seismicity regions.

https://mcej.modares.ac.ir/article_12602_fd8979ada2fd5bab05e9c5f035a5c4c7.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Evaluation of Parametric and Non-parametric Models in Predicting Rare Traffic Events Based on Average Speed and Traffic Volume Evaluation of Parametric and Non-parametric Models in Predicting Rare Traffic Events Based on Average Speed and Traffic Volume 59 71 12603 10.22034/23.2.4 FA A. Rasaizadi Tarbiat Modares University S. Seyedabrishami Tarbiat Modares University Journal Article One of the information needed for all planning problems and specifically transportation planning is to have accurate prediction about the future. Traffic variables prediction is one of the efficient tools in travel demand management. Using this tool and advanced traveler information systems (ATIS), the predicted traffic variables are informed to the users and transportation system operators to make plans and set policies. In this study, the average speed and traffic volume of the Karaj to Chalus suburban road with the high variation of traffic variables in the north of Iran is predicted. The Karaj to Chalous road is part of the route from Tehran as the capital of Iran to the country's northern coast. Along the Karaj to Chalous road, three parallel roads, with different lengths, connect Tehran with the cities of the north. In general, finding the pattern of non-mandatory trips is more complicated than mandatory trips. Generally, the predictive methods are divided into three groups, naïve, parametric and non-parametric methods. Among the various predictive models, the SARIMA as a parametric model and the artificial neural network and the support vector machine as nonparametric models are employed. In the data pre-processing step, the variables affecting the average speed and traffic volume are extracted and added to the dataset as predictor variables. These variables are related to time, calendar, holidays, weather, and roads blockage. Also, because of the importance of the maximum and minimum values of traffic speed and volume, as critical values and rare events, models are evaluated with emphasis on the prediction of rare events compared to normal values. The results show that, for the test data, the lowest root mean square error of predicting the average traffic speed and traffic volume are obtained using artificial neural network and support vector machine models equals 139 vehicles per hour and 5 kilometers per hour, respectively. In terms of R2 of prediction-observation plot, the performance of SARIMA for predicting the average speed and traffic volume is the same for the test dataset. In contrast the R2 of hourly traffic volume prediction is higher for the training data. The R2 of artificial neural network model and the support vector machine for traffic volume prediction is higher than traffic speed prediction. The lowest root mean square error of predicting the first and fourth quartile of the observed average traffic speed values is obtained by support vector machine models and artificial neural network, respectively. Also, predicting the first quartile and fourth quartile of the observed traffic volume values by the support vector machine model is more accurate than two other models. Using predicted traffic parameters and providing them to travelers and transportation agencies by intelligent transportation systems leads to make a balance between travel demand and travel supply in the near future which is the main aim of this study. Travelers can have a better personal plan for their future trips based on these predictions. Also, the transportation agencies are more prepared to deal with critical traffic situations and can prevent traffic congestion. One of the information needed for all planning problems and specifically transportation planning is to have accurate prediction about the future. Traffic variables prediction is one of the efficient tools in travel demand management. Using this tool and advanced traveler information systems (ATIS), the predicted traffic variables are informed to the users and transportation system operators to make plans and set policies. In this study, the average speed and traffic volume of the Karaj to Chalus suburban road with the high variation of traffic variables in the north of Iran is predicted. The Karaj to Chalous road is part of the route from Tehran as the capital of Iran to the country's northern coast. Along the Karaj to Chalous road, three parallel roads, with different lengths, connect Tehran with the cities of the north. In general, finding the pattern of non-mandatory trips is more complicated than mandatory trips. Generally, the predictive methods are divided into three groups, naïve, parametric and non-parametric methods. Among the various predictive models, the SARIMA as a parametric model and the artificial neural network and the support vector machine as nonparametric models are employed. In the data pre-processing step, the variables affecting the average speed and traffic volume are extracted and added to the dataset as predictor variables. These variables are related to time, calendar, holidays, weather, and roads blockage. Also, because of the importance of the maximum and minimum values of traffic speed and volume, as critical values and rare events, models are evaluated with emphasis on the prediction of rare events compared to normal values. The results show that, for the test data, the lowest root mean square error of predicting the average traffic speed and traffic volume are obtained using artificial neural network and support vector machine models equals 139 vehicles per hour and 5 kilometers per hour, respectively. In terms of R2 of prediction-observation plot, the performance of SARIMA for predicting the average speed and traffic volume is the same for the test dataset. In contrast the R2 of hourly traffic volume prediction is higher for the training data. The R2 of artificial neural network model and the support vector machine for traffic volume prediction is higher than traffic speed prediction. The lowest root mean square error of predicting the first and fourth quartile of the observed average traffic speed values is obtained by support vector machine models and artificial neural network, respectively. Also, predicting the first quartile and fourth quartile of the observed traffic volume values by the support vector machine model is more accurate than two other models. Using predicted traffic parameters and providing them to travelers and transportation agencies by intelligent transportation systems leads to make a balance between travel demand and travel supply in the near future which is the main aim of this study. Travelers can have a better personal plan for their future trips based on these predictions. Also, the transportation agencies are more prepared to deal with critical traffic situations and can prevent traffic congestion.

https://mcej.modares.ac.ir/article_12603_ae9ed3423e5d1c1fe8769d705207f040.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Experimental and Numerical Evaluation of Hybrid Steel-FRP Floor Panels Under Bending Loading Experimental and Numerical Evaluation of Hybrid Steel-FRP Floor Panels Under Bending Loading 73 89 12604 10.22034/23.2.5 FA S. Jami Faculty of Civil and Environmental Engineering, Tarbiat Modares University H. Khezrzadeh Faculty of Civil and Environmental Engineering, Tarbiat Modares University Journal Article In recent decades, new materials have had widespread applications in the construction industry. In the present research, a steel-FRP flooring system is proposed and tested. The implanted experiments are performed in two sections: at first, tests of constituent materials used in composite decks are done, and then full-scale tests of hybrid composite decks are performed. Mechanical tests, including three-point bending, compression, and tensile tests of GFRP profiles, tensile tests of steel plate, shear, and tensile tests of epoxy adhesives, are done with the aim of reaching mechanical properties. Next, flexural tests on four decks are performed. The main variables considered are the length of composite decks, the cold-formed steel channel effect, and the number of GFRP profiles. In examining the composite decks, the fracture between cohesive layers was observed, and damage localization and fracture in profiles occurred. It found that the use of the steel plate increases the stiffness and load-bearing capacity of the decks. The primary failure mode in the experimental work was deboning between profiles and adhesive fracturing in the decks without steel plates. In the decks which are used steel channels, the complete composite action of the structure was observed, resulting in suppressing the debonding phenomenon. The decks with cold-formed steel channels exhibit higher reliability as a result of their ductile behavior. After the tests of composite decks, the composite decks were modeled in the Abaqus software, and the results of the experiments and simulations were compared together. The results of numerical analysis have good agreement with experimental data. In recent decades, new materials have had widespread applications in the construction industry. In the present research, a steel-FRP flooring system is proposed and tested. The implanted experiments are performed in two sections: at first, tests of constituent materials used in composite decks are done, and then full-scale tests of hybrid composite decks are performed. Mechanical tests, including three-point bending, compression, and tensile tests of GFRP profiles, tensile tests of steel plate, shear, and tensile tests of epoxy adhesives, are done with the aim of reaching mechanical properties. Next, flexural tests on four decks are performed. The main variables considered are the length of composite decks, the cold-formed steel channel effect, and the number of GFRP profiles. In examining the composite decks, the fracture between cohesive layers was observed, and damage localization and fracture in profiles occurred. It found that the use of the steel plate increases the stiffness and load-bearing capacity of the decks. The primary failure mode in the experimental work was deboning between profiles and adhesive fracturing in the decks without steel plates. In the decks which are used steel channels, the complete composite action of the structure was observed, resulting in suppressing the debonding phenomenon. The decks with cold-formed steel channels exhibit higher reliability as a result of their ductile behavior. After the tests of composite decks, the composite decks were modeled in the Abaqus software, and the results of the experiments and simulations were compared together. The results of numerical analysis have good agreement with experimental data.

https://mcej.modares.ac.ir/article_12604_359f449e012b58f30cbc80ea8b9e794a.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Error Estimation and Stress Improvement in Nonlinear Analysis of Materials by Isogeometric Method Error Estimation and Stress Improvement in Nonlinear Analysis of Materials by Isogeometric Method 91 106 12605 10.22034/23.2.6 FA A. Ganjali Faculty member of Islamic Azad University, Shahrood Branch A. Mirzakhani Faculty member of Islamic Azad University, Shahrood Branch A. Shahini PhD student in Structural Islamic Azad University, Shahrood Branch Journal Article With the growth of science and technology, engineering issues are becoming more complex. As problems become more complex and need to be resolved more quickly and accurately, past analytical methods no longer meet the growing needs of societies. With such an attitude, researchers have always tried to develop numerical methods in addition to developing the basics of science. In this direction, several methods have been developed by researchers. Each of these methods has its own applications and still researchers are trying to grow and develop these methods and invent new methods. The most important of these are the nonlinear isogeometric method which is based on non-uniform rational B-Splines (NURBS). In the nonlinear isogeometric method, while using the properties of the basic functions of spline and NURBS in the exact definition of curves and surfaces, they are also used for interpolation and approximation. Using all the capacity of the structure in load bearing causes nonlinear behavior of the structure which is due to improper performance of the structure geometry, weakness of the structural materials and weakness due to the combination of the two previous states. In this study, nonlinearity due to material weakness has been considered. Also, in solving nonlinear equilibrium equations, an incremental and iterative process of load is used and this increase is done until the total loads defined for each problem are entered. In each increase, the iterative process is adopted until convergence or the maximum number of iterations is achieved. Obviously, all numerical methods are approximate methods. The main source of error in numerical methods is related to the discretization error of the continuous environment and is due to the approximation of the displacement field by the shape functions. This group of errors is also reduced by making the elemental mesh smaller and increasing the degree of shape functions used. Error is an integral part of numerical analysis and has always been a concern for researchers in the reliability of the results. Therefore, in this study, the error estimation based on the stress recovery method based on points where the order of gradient convergence of a function is one time higher than the value expected from the approximation of the shape function related to the approximate solution (superconvergent points) is discussed. Thus, by considering the difference between the recovered stress level and the stress level obtained from nonlinear isogeometric analysis for each element, a criterion has been determined approximately to determine the amount of error in that element. All research relationalizations and linearization of equations have been performed using a numerical algorithm with the help of programming in Fortran software environment and the results of the analysis for validation have been compared with its classical solution. The results show acceptable numerical and distributive similarity; Therefore, it can be said that the analysis performed by the program has good performance for nonlinear analysis of problems. Also, the error estimation method used can be called a simple and engineering solution to estimate the error and improve the stress field obtained from elastoplastic analysis of problems by isogeometric method. With the growth of science and technology, engineering issues are becoming more complex. As problems become more complex and need to be resolved more quickly and accurately, past analytical methods no longer meet the growing needs of societies. With such an attitude, researchers have always tried to develop numerical methods in addition to developing the basics of science. In this direction, several methods have been developed by researchers. Each of these methods has its own applications and still researchers are trying to grow and develop these methods and invent new methods. The most important of these are the nonlinear isogeometric method which is based on non-uniform rational B-Splines (NURBS). In the nonlinear isogeometric method, while using the properties of the basic functions of spline and NURBS in the exact definition of curves and surfaces, they are also used for interpolation and approximation. Using all the capacity of the structure in load bearing causes nonlinear behavior of the structure which is due to improper performance of the structure geometry, weakness of the structural materials and weakness due to the combination of the two previous states. In this study, nonlinearity due to material weakness has been considered. Also, in solving nonlinear equilibrium equations, an incremental and iterative process of load is used and this increase is done until the total loads defined for each problem are entered. In each increase, the iterative process is adopted until convergence or the maximum number of iterations is achieved. Obviously, all numerical methods are approximate methods. The main source of error in numerical methods is related to the discretization error of the continuous environment and is due to the approximation of the displacement field by the shape functions. This group of errors is also reduced by making the elemental mesh smaller and increasing the degree of shape functions used. Error is an integral part of numerical analysis and has always been a concern for researchers in the reliability of the results. Therefore, in this study, the error estimation based on the stress recovery method based on points where the order of gradient convergence of a function is one time higher than the value expected from the approximation of the shape function related to the approximate solution (superconvergent points) is discussed. Thus, by considering the difference between the recovered stress level and the stress level obtained from nonlinear isogeometric analysis for each element, a criterion has been determined approximately to determine the amount of error in that element. All research relationalizations and linearization of equations have been performed using a numerical algorithm with the help of programming in Fortran software environment and the results of the analysis for validation have been compared with its classical solution. The results show acceptable numerical and distributive similarity; Therefore, it can be said that the analysis performed by the program has good performance for nonlinear analysis of problems. Also, the error estimation method used can be called a simple and engineering solution to estimate the error and improve the stress field obtained from elastoplastic analysis of problems by isogeometric method.

https://mcej.modares.ac.ir/article_12605_254b6cccc84a3b7e5c696e67c9ef656e.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Investigation of the Effects of Annular Baffles on the Seismic Behavior of Fixed-Base Cylindrical Liquid Tanks Investigation of the Effects of Annular Baffles on the Seismic Behavior of Fixed-Base Cylindrical Liquid Tanks 107 122 12606 10.22034/23.2.7 FA SH. Farahmandpey M.Sc. in Water and Hydraulic Structure Engineering at Shiraz University, Shiraz, Iran. P. Broumand Assistant Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. S. Amiri Assistant Professor, Department of Civil and Environmental Engineering, Shiraz University, Shiraz, Iran. M. Shekari Assistant Professor, Department of Civil Engineering, Estahban Higher Education Center, Estahban, Iran. Journal Article By studying the literature on liquid storage tanks and their seismic behavior, it is observed that sloshing waves have caused severe damages to the walls and upper parts of these structures. As a remedy, some researchers have provided passive control systems to mitigate the seismic responses; one of these passive systems is annular baffles which are mounted on different heights of the tank wall. In the present study, seismic behavior of the slender and broad fixed-based tanks with baffles of different geometries have been examined; for this purpose, the deformation of the tank shell and baffles in the time and frequency domains are considered. The coupled acoustic-structure formulation based on fluid pressure and structure displacement has been used in the framework of linear finite element method in ABAQUS commercial software. At the interaction surface, fluid pressure and the normal acceleration of the structure interact with each other using the surface-based interaction capability of the ABAQUS software. The liquid is assumed to be compressible, inviscid and irrotational, and seismic loading is applied to the liquid-filled storage tanks' supports. The models are verified by comparison with the results that are reported in the literature in frequency and time domains. A parametric study is performed on Ri/R radius ratio and h/H distance ratio of baffles in the slender and board tank. Results indicated that in the frequency domain, the geometry with ratios (Ri/R=0.3, h/H=0.1 ) of the baffles which has the biggest radial coverage and the smallest distance ratios from the liquid surface, has the highest reduction effect on the frequency of the first convective mode of the slender and broad tanks, equal to 43% and 68%, respectively. Therefore, top-mounted baffles with considerable radial coverage, have higher effects on reducing the frequency of the first convective mode of the tanks. Baffles have fewer effects on the frequency of the first impulsive mode than on the first convective mode. Besides, analyses in the time domain revealed that top-mounted baffles with medium and small radial coverage in the broad tanks caused the increase of the sloshing wave amplitudes by about 68%, at worst cases. Baffles with less effects on the first convective modes were more effective on decreasing the sloshing wave amplitudes. Therefore, satisfactory performance of the baffled liquid tanks may not be obtained by solely relying on the frequency of the first convective mode of the tanks, due to unwanted increase of sloshing amplitudes in the special cases of liquid tank geometry and baffles. According to the results, in the board tanks, top-mounted baffles may amplify the seismic response of the system and thus, considerable attention is required on the use of passive devices in such tanks. Unlike the broad tanks, baffles have satisfactory influences on the seismic behavior of the slender tank. It’s recommended that when the baffles are used as a passive controlling system in a broad tank, all of the tank responses such as base shear, hydrodynamic pressure, and etc. to be considered; since, these responses may increase significantly if top-mounted baffles are used. Analysis in time domain also indicates that the differentiation between the slender and broad tanks in studying the baffles' effects is crucial. In general, using middle-mounted baffles is recommended as an efficient passive system to mitigate the sloshing waves in broad tanks. By studying the literature on liquid storage tanks and their seismic behavior, it is observed that sloshing waves have caused severe damages to the walls and upper parts of these structures. As a remedy, some researchers have provided passive control systems to mitigate the seismic responses; one of these passive systems is annular baffles which are mounted on different heights of the tank wall. In the present study, seismic behavior of the slender and broad fixed-based tanks with baffles of different geometries have been examined; for this purpose, the deformation of the tank shell and baffles in the time and frequency domains are considered. The coupled acoustic-structure formulation based on fluid pressure and structure displacement has been used in the framework of linear finite element method in ABAQUS commercial software. At the interaction surface, fluid pressure and the normal acceleration of the structure interact with each other using the surface-based interaction capability of the ABAQUS software. The liquid is assumed to be compressible, inviscid and irrotational, and seismic loading is applied to the liquid-filled storage tanks' supports. The models are verified by comparison with the results that are reported in the literature in frequency and time domains. A parametric study is performed on Ri/R radius ratio and h/H distance ratio of baffles in the slender and board tank. Results indicated that in the frequency domain, the geometry with ratios (Ri/R=0.3, h/H=0.1 ) of the baffles which has the biggest radial coverage and the smallest distance ratios from the liquid surface, has the highest reduction effect on the frequency of the first convective mode of the slender and broad tanks, equal to 43% and 68%, respectively. Therefore, top-mounted baffles with considerable radial coverage, have higher effects on reducing the frequency of the first convective mode of the tanks. Baffles have fewer effects on the frequency of the first impulsive mode than on the first convective mode. Besides, analyses in the time domain revealed that top-mounted baffles with medium and small radial coverage in the broad tanks caused the increase of the sloshing wave amplitudes by about 68%, at worst cases. Baffles with less effects on the first convective modes were more effective on decreasing the sloshing wave amplitudes. Therefore, satisfactory performance of the baffled liquid tanks may not be obtained by solely relying on the frequency of the first convective mode of the tanks, due to unwanted increase of sloshing amplitudes in the special cases of liquid tank geometry and baffles. According to the results, in the board tanks, top-mounted baffles may amplify the seismic response of the system and thus, considerable attention is required on the use of passive devices in such tanks. Unlike the broad tanks, baffles have satisfactory influences on the seismic behavior of the slender tank. It’s recommended that when the baffles are used as a passive controlling system in a broad tank, all of the tank responses such as base shear, hydrodynamic pressure, and etc. to be considered; since, these responses may increase significantly if top-mounted baffles are used. Analysis in time domain also indicates that the differentiation between the slender and broad tanks in studying the baffles' effects is crucial. In general, using middle-mounted baffles is recommended as an efficient passive system to mitigate the sloshing waves in broad tanks.

https://mcej.modares.ac.ir/article_12606_4d91e93c7905243a769485162b66e3dc.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Polyvinyl Chloride Composite Paste for Coating in Concrete Canvas Structure with Casting Technology: Preparation and Characterization Polyvinyl Chloride Composite Paste for Coating in Concrete Canvas Structure with Casting Technology: Preparation and Characterization 123 133 12607 10.22034/23.2.8 FA M. Moslehi Imam Hosein Uni Researcher M. Fayyaz Civil Engineering Department. Assistant Prof S. Ahmadi Imam Hosein Uni- Assistant Professor Journal Article The concrete canvas product consists of three main parts: the three-dimensional (3D) substrate with the cement mixture, the geo-membrane layer and the desired adhesive to connect the geo-membrane layer to the three-dimensional substrate. The three-dimensional layer is generally made of polyester, polypropylene and other engineered polymer had good mechanical and chemical properties, and has different thicknesses, suitable for various applications. This three-dimensional layer is designed in such a way that it has different textures on both sides so that the cement is poured into the space of the three-dimensional layer on one side and nothing spills out of the other layer. In the next step, this process is completed by connecting the geo-membrane layer to it. In industrial application; the geo-membrane layer formulation (including polymer-based resin, emollient, impact curing, filler, etc.) is designed in such a way that in addition to moisture insulation properties, mechanical strength and good chemical resistance to moisture dilute alkaline and acidic environments. In this way, a desired adhesive with desired formulation (including adhesive base resin, solvent, activator and type of catalytic additive, etc.) was selected for connecting of geo-membrane to 3D substrate. To achieve a suitable product, in addition to the geo-membrane layer, the adhesive selected to connect the geo-membrane layer to the three-dimensional substrate must have the appropriate viscosity to be able to completely cover the three-dimensional substrate and cause the two layers to be fully connected to each other. . If the adhesive used cannot create a suitable coating on the geo-membrane layer, by penetrating the fluid around the adhesive, it will weaken and thus destroy the entire coating layer and thus separate the layered concrete layers. In this way, one of the main disadvantages of concrete canvas produced by conventional methods is the separation/layering of the coating layer from the concrete canvas substrate due to thermal and mechanical stress, which weakens the adhesive connecting the layer to the substrate which creates practical problem for this product. In this work, the polymer casting technology based on polyvinyl chloride paste was used to cover a concrete canvas and the properties of the product were investigated. In this method, the polymer paste is coated on the three-dimensional substrate in one step without using (geo-membrane / adhesive) by Dr. Blade knife in a certain thickness. The results showed that the fabric concrete made based on the PVC paste casting method, has good sealing, mechanical and chemical resistance and has good resistance against layering. The results showed that the fabric concrete product obtained from the polymer casting method based on (resin / polyvinyl chloride paste) in terms of mechanical strength, showed acceptable properties compared to the geo-membrane layer and the overall fabric concrete product and also in terms of chemical properties (resistance to various solvents), it has a much better resistance than the sample made by conventional methods (geo-membrane / adhesive). This product (concrete canvas) has also shown better resistance to water leakage against the sealing of the product, the overall product made by the polymer casting method. The concrete canvas product consists of three main parts: the three-dimensional (3D) substrate with the cement mixture, the geo-membrane layer and the desired adhesive to connect the geo-membrane layer to the three-dimensional substrate. The three-dimensional layer is generally made of polyester, polypropylene and other engineered polymer had good mechanical and chemical properties, and has different thicknesses, suitable for various applications. This three-dimensional layer is designed in such a way that it has different textures on both sides so that the cement is poured into the space of the three-dimensional layer on one side and nothing spills out of the other layer. In the next step, this process is completed by connecting the geo-membrane layer to it. In industrial application; the geo-membrane layer formulation (including polymer-based resin, emollient, impact curing, filler, etc.) is designed in such a way that in addition to moisture insulation properties, mechanical strength and good chemical resistance to moisture dilute alkaline and acidic environments. In this way, a desired adhesive with desired formulation (including adhesive base resin, solvent, activator and type of catalytic additive, etc.) was selected for connecting of geo-membrane to 3D substrate. To achieve a suitable product, in addition to the geo-membrane layer, the adhesive selected to connect the geo-membrane layer to the three-dimensional substrate must have the appropriate viscosity to be able to completely cover the three-dimensional substrate and cause the two layers to be fully connected to each other. . If the adhesive used cannot create a suitable coating on the geo-membrane layer, by penetrating the fluid around the adhesive, it will weaken and thus destroy the entire coating layer and thus separate the layered concrete layers. In this way, one of the main disadvantages of concrete canvas produced by conventional methods is the separation/layering of the coating layer from the concrete canvas substrate due to thermal and mechanical stress, which weakens the adhesive connecting the layer to the substrate which creates practical problem for this product. In this work, the polymer casting technology based on polyvinyl chloride paste was used to cover a concrete canvas and the properties of the product were investigated. In this method, the polymer paste is coated on the three-dimensional substrate in one step without using (geo-membrane / adhesive) by Dr. Blade knife in a certain thickness. The results showed that the fabric concrete made based on the PVC paste casting method, has good sealing, mechanical and chemical resistance and has good resistance against layering. The results showed that the fabric concrete product obtained from the polymer casting method based on (resin / polyvinyl chloride paste) in terms of mechanical strength, showed acceptable properties compared to the geo-membrane layer and the overall fabric concrete product and also in terms of chemical properties (resistance to various solvents), it has a much better resistance than the sample made by conventional methods (geo-membrane / adhesive). This product (concrete canvas) has also shown better resistance to water leakage against the sealing of the product, the overall product made by the polymer casting method.

https://mcej.modares.ac.ir/article_12607_388ac20c845a327f97edece8acba6237.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Evaluation of the Post-fire Seismic Response of Reinforced Concrete Frames by Finite Element Method Evaluation of the Post-fire Seismic Response of Reinforced Concrete Frames by Finite Element Method 135 150 12608 10.22034/23.2.9 FA M. Kamalvand Kharazmi University A. Massumi Kharazmi University A. Barimani Kharazmi University Journal Article Accidental fire can be a catastrophe for engineering constructions, especially in building structures. Among structures made of various engineering materials exposed to fire, the reinforced concrete (RC) structures show better performance against fire, due to lower relative thermal conductivity, higher specific heat capacity of concrete, and slower reduction of concrete mechanical characteristics compared with other types of the structure materials. However, in case of severe fire exposure, the RC structures may experience serious structural damage due to the explosive concrete spalling resulting in a high-temperature rise in the reinforcing rebars and relatively large deformation with very limited residual bearing capacity. Although the explosive spalling and significant loss of the cross-sectional area of RC structural elements is a sign of severe damage to these elements, the reduction of mechanical properties of the materials and the performance level of the structure due to chemical reactions such as C-S-H gel dehydration caused by penetration of high temperature in the interior layers of the element cross-section may not be easily visible and evaluated. A building that has experienced a fire, cannot be exploited for immediate reuse, even when the fire is completely extinguished until load bearing capacity of its members is determined. Therefore, it is necessary to determine the residual capacity of structural elements through logical engineering methods to facilitate the re-operation or development of strengthening methods in the fired RC structures. Due to the importance of recognizing the behavior and residual seismic capacity of the structures exposed to fire, in this paper, a numerical study based on the nonlinear finite element method has been performed on RC frames. In the first step of the research, the process of heat distribution in the frames located in the furnace based on the previous experimental study is simulated by heat transfer analysis. All three modes of heat transfer including convection, radiation, and conduction were considered in this analysis and the effect of moisture content and emissivity coefficient was evaluated. In the second step, using the residual mechanical properties of materials (reinforcing steel rebar and concrete) based on the maximum heat experienced in the previous step, the seismic behavior of RC frames is evaluated using the pushover analysis. The experimental RC specimens used to validate the proposed numerical model consist of two frames with various beam/column bending capacity ratios in two cases, at room temperature and after being exposed to fire. Due to the different relationships available to determine the residual compressive strength of concrete, the seismic response of the frame was investigated based on three common relations Shi, Lie, and Schneider. The results showed that the proposed numerical analysis method has good accuracy in both steps of analysis and different models for estimating the residual compressive strength, despite some differences, have the ability to predict the post-fire performance of RC frames. It was also shown that for the RC frame specimen with the strong beam-weak column, the ratio of reduced post-fire load bearing capacity and energy absorption is higher. Accidental fire can be a catastrophe for engineering constructions, especially in building structures. Among structures made of various engineering materials exposed to fire, the reinforced concrete (RC) structures show better performance against fire, due to lower relative thermal conductivity, higher specific heat capacity of concrete, and slower reduction of concrete mechanical characteristics compared with other types of the structure materials. However, in case of severe fire exposure, the RC structures may experience serious structural damage due to the explosive concrete spalling resulting in a high-temperature rise in the reinforcing rebars and relatively large deformation with very limited residual bearing capacity. Although the explosive spalling and significant loss of the cross-sectional area of RC structural elements is a sign of severe damage to these elements, the reduction of mechanical properties of the materials and the performance level of the structure due to chemical reactions such as C-S-H gel dehydration caused by penetration of high temperature in the interior layers of the element cross-section may not be easily visible and evaluated. A building that has experienced a fire, cannot be exploited for immediate reuse, even when the fire is completely extinguished until load bearing capacity of its members is determined. Therefore, it is necessary to determine the residual capacity of structural elements through logical engineering methods to facilitate the re-operation or development of strengthening methods in the fired RC structures. Due to the importance of recognizing the behavior and residual seismic capacity of the structures exposed to fire, in this paper, a numerical study based on the nonlinear finite element method has been performed on RC frames. In the first step of the research, the process of heat distribution in the frames located in the furnace based on the previous experimental study is simulated by heat transfer analysis. All three modes of heat transfer including convection, radiation, and conduction were considered in this analysis and the effect of moisture content and emissivity coefficient was evaluated. In the second step, using the residual mechanical properties of materials (reinforcing steel rebar and concrete) based on the maximum heat experienced in the previous step, the seismic behavior of RC frames is evaluated using the pushover analysis. The experimental RC specimens used to validate the proposed numerical model consist of two frames with various beam/column bending capacity ratios in two cases, at room temperature and after being exposed to fire. Due to the different relationships available to determine the residual compressive strength of concrete, the seismic response of the frame was investigated based on three common relations Shi, Lie, and Schneider. The results showed that the proposed numerical analysis method has good accuracy in both steps of analysis and different models for estimating the residual compressive strength, despite some differences, have the ability to predict the post-fire performance of RC frames. It was also shown that for the RC frame specimen with the strong beam-weak column, the ratio of reduced post-fire load bearing capacity and energy absorption is higher.

https://mcej.modares.ac.ir/article_12608_6afea581e2d33bf935e94036b41979b2.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Using Temperature Sweep Test to Develope Master Curves of Bitumen Viscoelastic Properties Using Temperature Sweep Test to Develope Master Curves of Bitumen Viscoelastic Properties 151 165 12609 10.22034/23.2.10 FA M. Gholami Department of civil and environmental engineering, Amirkabir university of technology (Tehran Polytechnic), Tehran, Iran P. Hajikarimi Department of civil and environmental engineering, Amirkabir university of technology (Tehran Polytechnic), Tehran, Iran A. Khodaii Department of civil and environmental engineering, Amirkabir university of technology (Tehran Polytechnic), Tehran, Iran Journal Article Asphalt mixtures and bitumens are faced with different traffic loading and thermal stresses during their lifetime. Due to their viscoelastic behavior, these materials exhibit different mechanical properties at different temperatures and traffic loading. Viscoelastic properties of bitumens are commonly expressed using the master curves of complex shear modulus (G*) and phase angle (δ) generally created by the horizontal shifting of the frequency sweep test results using shift factors. There are several methods for evaluating temperature shift factors, such as Williams, Landel, and Ferry (WLF) equation, modified Kaelble method, Log-Linear approach, and LCPC method. The LCPC method, developed using the Kramers-Kronig relationship, can be used to accurately evaluate the shift factor of bitumens, mastics, and asphalt mixtures. This study investigated the possibility of generating the master curves of bitumen based on temperature sweep test results rather than frequency sweep test results. Two types of bitumens were investigated in this study, neat bitumen with an 85-100 penetration grade (PG 58-22 performance grade) and SEPS modified asphalt binder with SEPS polymer content of 2, 4, and 6% by weight of the total binder. Temperature sweep tests were performed on all types of bitumens in a range of temperatures between 30 and 90 °C and the frequency of 1.59 Hz. Also, frequency sweep tests were performed on all kinds of bitumens in a range of temperature between 10 and 60 °C and a range of frequency between 0.1 and 100 Hz. The LCPC method was also investigated to calculate the shift factors for the master curves of complex shear modulus and phase angle, and the master curves of viscoelastic properties for all bitumen types are made based on temperature sweep and frequency sweep test results. The results indicated that the SEPS polymer could effectively increase the complex shear modulus and reduce the magnitude of phase angle. So, this polymer improved the rutting resistance of SEPS polymer-modified binders and led to better high-temperature performance of binders. In addition, the LCPC method effectively produced a valid and accurate form of the master curve using temperature sweep test results similar to the master curve using frequency sweep test results. Furthermore, the master curves of complex shear modulus (G*) and phase angle (δ) derived from temperature and frequency sweep test results exhibited comparable patterns and values. By plotting the value of complex shear modulus and phase angle obtained from the temperature sweep master curves versus the complex shear modulus and phase angle obtained from the frequency sweep master curves at the same reduced frequency, it was observed that all points were scattered in the vicinity of the y=x line. It was indicated that the master curves created based on temperature sweep test results have an acceptable approximation and accuracy with the master curves created based on frequency sweep test results. As a consequence, it may be preferable to generate the master curve of viscoelastic characteristics of bitumens using the results of the temperature sweep test, which is faster and more accurate in some conditions, compared to the results of the frequency sweep test. Asphalt mixtures and bitumens are faced with different traffic loading and thermal stresses during their lifetime. Due to their viscoelastic behavior, these materials exhibit different mechanical properties at different temperatures and traffic loading. Viscoelastic properties of bitumens are commonly expressed using the master curves of complex shear modulus (G*) and phase angle (δ) generally created by the horizontal shifting of the frequency sweep test results using shift factors. There are several methods for evaluating temperature shift factors, such as Williams, Landel, and Ferry (WLF) equation, modified Kaelble method, Log-Linear approach, and LCPC method. The LCPC method, developed using the Kramers-Kronig relationship, can be used to accurately evaluate the shift factor of bitumens, mastics, and asphalt mixtures. This study investigated the possibility of generating the master curves of bitumen based on temperature sweep test results rather than frequency sweep test results. Two types of bitumens were investigated in this study, neat bitumen with an 85-100 penetration grade (PG 58-22 performance grade) and SEPS modified asphalt binder with SEPS polymer content of 2, 4, and 6% by weight of the total binder. Temperature sweep tests were performed on all types of bitumens in a range of temperatures between 30 and 90 °C and the frequency of 1.59 Hz. Also, frequency sweep tests were performed on all kinds of bitumens in a range of temperature between 10 and 60 °C and a range of frequency between 0.1 and 100 Hz. The LCPC method was also investigated to calculate the shift factors for the master curves of complex shear modulus and phase angle, and the master curves of viscoelastic properties for all bitumen types are made based on temperature sweep and frequency sweep test results. The results indicated that the SEPS polymer could effectively increase the complex shear modulus and reduce the magnitude of phase angle. So, this polymer improved the rutting resistance of SEPS polymer-modified binders and led to better high-temperature performance of binders. In addition, the LCPC method effectively produced a valid and accurate form of the master curve using temperature sweep test results similar to the master curve using frequency sweep test results. Furthermore, the master curves of complex shear modulus (G*) and phase angle (δ) derived from temperature and frequency sweep test results exhibited comparable patterns and values. By plotting the value of complex shear modulus and phase angle obtained from the temperature sweep master curves versus the complex shear modulus and phase angle obtained from the frequency sweep master curves at the same reduced frequency, it was observed that all points were scattered in the vicinity of the y=x line. It was indicated that the master curves created based on temperature sweep test results have an acceptable approximation and accuracy with the master curves created based on frequency sweep test results. As a consequence, it may be preferable to generate the master curve of viscoelastic characteristics of bitumens using the results of the temperature sweep test, which is faster and more accurate in some conditions, compared to the results of the frequency sweep test.

https://mcej.modares.ac.ir/article_12609_112a8e92dcedcda4237de18e9126b2d2.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Experimental Study on Flow Over Rectangular Piano Key Weirs with Slopped Side Crests Experimental Study on Flow Over Rectangular Piano Key Weirs with Slopped Side Crests 167 175 12610 10.22034/23.2.11 FA M. Ghodsian TMU H. Sohrabzadeh Anzani Journal Article Abstract In this paper results of experiments on discharge coefficient of rectangular Piano key weirs are presented. Experiments were conducted using two Piano key weirs: one with sloped side walls crest and the other one with horizontal crest. Piano Key weirs with constant value of ratio of length to width were used. The results showed that water level upstream of weir with sloped side walls crest increased by about 11.02 percent. The discharge coefficient of weir with sloped side walls crest increased by about 4.8 percent. The efficiency of weir with sloped side wall crest is increases by about 7.3 percent. New equation for prediction of discharge coefficient of rectangular Piano key weir with sloped side walls crest and horizontal crest was obtained. Abstract In this paper results of experiments on discharge coefficient of rectangular Piano key weirs are presented. Experiments were conducted using two Piano key weirs: one with sloped side walls crest and the other one with horizontal crest. Piano Key weirs with constant value of ratio of length to width were used. The results showed that water level upstream of weir with sloped side walls crest increased by about 11.02 percent. The discharge coefficient of weir with sloped side walls crest increased by about 4.8 percent. The efficiency of weir with sloped side wall crest is increases by about 7.3 percent. New equation for prediction of discharge coefficient of rectangular Piano key weir with sloped side walls crest and horizontal crest was obtained.

https://mcej.modares.ac.ir/article_12610_e3743b463beb38a2a24eebe5ecbad410.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Seismic Behavior of Innovative Braces Using Incremental Dynamic Analysis Seismic Behavior of Innovative Braces Using Incremental Dynamic Analysis 177 192 12611 10.22034/23.2.12 FA R. Mardi School of Civil EngineeringUniversity of Tehran M. Ghassemieh School of Civil EngineeringUniversity of Tehran Journal Article BRBs are a new type of seismic resistance system that is being used extensively nowadays due to their enhanced seismic performance than conventional braces. In BRB braces, because the buckling of the steel core is prevented, the structure shows more stable behavior. In this type of bracing, the hysteresis performance of the bracing is similar to the hysteresis performance of the core material. Another feature of these braces is that the ductility of the steel material occurs over a considerable length of the brace. Although BRB braces are capable of dissipating large amounts of energy, they are unable to eliminate their residual strains. In other words, they do not have the property of self-centering. This leads to the non-return of the structure and to its original configuration after the seismic excitations; in the absence of a return mechanism. There may arise many permanent deformations in the structure during an earthquake. To overcome these permanent deformations, various innovative solutions have been developed in the construction of steel frames, including the use of shape memory alloys (SMA) that have two prominent features of shape memory and superelastic behavior and can return to their original position after subjected to the various loadings condition. In recent years, beside the Nitinol shape memory alloy (NiTi), Iron-based shape memory alloys (SMA-Fe), which have many advantages over previous SMAs and particularly due to their lower cost, have been introduced and being used in many construction projects. In this research, the seismic behavior of structures braced with BRB, and iron-based shape memory alloy and Nitinol shape memory alloys has been investigated. Seismostruct finite element software has been used to model these systems. Incremental dynamic analysis (IDA) has been performed on seven story structures equipped with X braces with different materials. The results of this study show that braced structures with iron-base shape memory alloys undergo less maximum displacement and permanent displacement compared to nitinol-braced structures. However, these structures experience more maximum displacement than BRB braced structure. The more the structures enter the nonlinear stage (in the maximum values of the relative inter-floor displacement demand) the more the dispersion of the results increases and the structure is more affected by the input accelerometers. The structure with buckling bracing will reach instability later than the two structures with shape memory alloy bracing. It is also observed that the elastic stiffness (slope of the linear behavior region) in all 3 braced frames is equal to each other. And finally, the IDA curve of the BRB structure is higher than the two shape memory alloy structures, and at equal acceleration, it is clear that the displacement of the shape memory alloy structures is more than the buckling structure, and it can also be seen that the iron-based shape memory alloy brace has a favorable performance and its curve is slightly higher than the NiTi shape memory alloy. Also, two shape memory alloy structures move almost together and reach instability at one point. According to the curves, it seems that the braced structures with shape memory alloys have performed well and until these structures reach instability. BRBs are a new type of seismic resistance system that is being used extensively nowadays due to their enhanced seismic performance than conventional braces. In BRB braces, because the buckling of the steel core is prevented, the structure shows more stable behavior. In this type of bracing, the hysteresis performance of the bracing is similar to the hysteresis performance of the core material. Another feature of these braces is that the ductility of the steel material occurs over a considerable length of the brace. Although BRB braces are capable of dissipating large amounts of energy, they are unable to eliminate their residual strains. In other words, they do not have the property of self-centering. This leads to the non-return of the structure and to its original configuration after the seismic excitations; in the absence of a return mechanism. There may arise many permanent deformations in the structure during an earthquake. To overcome these permanent deformations, various innovative solutions have been developed in the construction of steel frames, including the use of shape memory alloys (SMA) that have two prominent features of shape memory and superelastic behavior and can return to their original position after subjected to the various loadings condition. In recent years, beside the Nitinol shape memory alloy (NiTi), Iron-based shape memory alloys (SMA-Fe), which have many advantages over previous SMAs and particularly due to their lower cost, have been introduced and being used in many construction projects. In this research, the seismic behavior of structures braced with BRB, and iron-based shape memory alloy and Nitinol shape memory alloys has been investigated. Seismostruct finite element software has been used to model these systems. Incremental dynamic analysis (IDA) has been performed on seven story structures equipped with X braces with different materials. The results of this study show that braced structures with iron-base shape memory alloys undergo less maximum displacement and permanent displacement compared to nitinol-braced structures. However, these structures experience more maximum displacement than BRB braced structure. The more the structures enter the nonlinear stage (in the maximum values of the relative inter-floor displacement demand) the more the dispersion of the results increases and the structure is more affected by the input accelerometers. The structure with buckling bracing will reach instability later than the two structures with shape memory alloy bracing. It is also observed that the elastic stiffness (slope of the linear behavior region) in all 3 braced frames is equal to each other. And finally, the IDA curve of the BRB structure is higher than the two shape memory alloy structures, and at equal acceleration, it is clear that the displacement of the shape memory alloy structures is more than the buckling structure, and it can also be seen that the iron-based shape memory alloy brace has a favorable performance and its curve is slightly higher than the NiTi shape memory alloy. Also, two shape memory alloy structures move almost together and reach instability at one point. According to the curves, it seems that the braced structures with shape memory alloys have performed well and until these structures reach instability.

https://mcej.modares.ac.ir/article_12611_c4dc035d67bc669546c560622ac4bdd4.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Numerical Modeling of Contamination Transport Equation in Porous Media for Transient Flow Regime by Finite Volume Method Numerical Modeling of Contamination Transport Equation in Porous Media for Transient Flow Regime by Finite Volume Method 193 205 12612 10.22034/23.2.13 FA R. Asadi Department of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran K. Azizi Department of Civil Engineering, K.N. Toosi University of Technology, Tehran, Iran Journal Article Groundwater is an essential source of fresh water, which is less prone to pollution in comparison to surface water, and access to this valuable resource is affordable. These issues make groundwater a viable source during surface water shortages such as drought, especially in arid and semi-arid countries. In this research, the equation of contamination transport in groundwater is modeled by a novel dual discrete finite volume method (DDFVM). Using this numerical method, the contamination concentrations are obtained at the center and vertices of each element. This model has been applied to an unstructured triangular mesh that could be fitted to complex geometric boundaries. For the transient flow regimes, the flow equation has been coupled with the contaminant transport problem, and the results of the numerical model are validated with the model of Modflow. Finally, the flow and transport FV coupled model has been applied in a porous media with strong heterogeneity. The free-oscillation results for the two parameters of head and concentration demonstrate the stability of the model. Groundwater is an essential source of fresh water, which is less prone to pollution in comparison to surface water, and access to this valuable resource is affordable. These issues make groundwater a viable source during surface water shortages such as drought, especially in arid and semi-arid countries. In this research, the equation of contamination transport in groundwater is modeled by a novel dual discrete finite volume method (DDFVM). Using this numerical method, the contamination concentrations are obtained at the center and vertices of each element. This model has been applied to an unstructured triangular mesh that could be fitted to complex geometric boundaries. For the transient flow regimes, the flow equation has been coupled with the contaminant transport problem, and the results of the numerical model are validated with the model of Modflow. Finally, the flow and transport FV coupled model has been applied in a porous media with strong heterogeneity. The free-oscillation results for the two parameters of head and concentration demonstrate the stability of the model.

https://mcej.modares.ac.ir/article_12612_1b31a4f23c784d5b162a3066fa9aaf4f.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Experimental and Analytical Assessment of Soil Settlement Due to Groundwater Rising in the Framework of Unsaturated Soil Mechanics Experimental and Analytical Assessment of Soil Settlement Due to Groundwater Rising in the Framework of Unsaturated Soil Mechanics 207 221 12613 10.22034/23.2.14 FA J. Pargar Civil Engineering Department, Faculty of engineering, Ferdowsi University of Mashhad A. Akhtarpour Civil Engineering Department, Faculty of engineering, Ferdowsi University of Mashhad 0000-0003-1654-0194 Journal Article In the present study, with the help of experimental studies and based on the basic relationships of unsaturated soil mechanics theory, an analytical model is proposed to estimate soil settlements due to groundwater level rise after construction and its importance in accurately estimating the final soil subsidence. To determine the geotechnical parameters used in the design, experiments are performed either under saturated conditions or at natural moisture, and the effects of changes in moisture; in other words, drying and wetting paths are not considered. However, in the event of rainfall, the burst of water and sewage pipes, leakage from absorption wells, rising groundwater levels, and similar phenomena, the soil becomes wet and its behavior changes, eventually leading to softening and imposing additional settlement which can cause damage to the surface structures. In traditional laboratory studies, this wetting is partially evaluated using the double consolidation test with the calculation of the collapsibility index. This assessment method is limited to soil with fully saturation in a one-dimensional and uncontrolled matric suction device. The results are qualitative and without enough accurate for use in settlement calculations in wetting paths for unsaturated soils. In this study, the behavior of silty soil under consolidated isotropic tests under saturated and unsaturated conditions as well as controlled wetting of consolidated specimens at constant loading with the help of an unsaturated triaxial device was investigated; Afterward; using the results of laboratory studies with presenting a analytical model based on the basic relationships of unsaturated soil mechanics and the theory of calculation of terzagi consolidation, the effect of water level rising on the shallow foundation settlements under constant loading was investigated. The results showed that the amount of soil settlements due to this phenomenon is related to the initial density and soil consolidation properties in unsaturated conditions, volumetric change characteristics in the wetting paths, dimensions and intensity of foundation loading, initial groundwater level depth and ascent rising rate. In the present study, for a square foundation with dimensions of 10 to 20 meters with constant loading located on the silty soil mass, the depth of the initial groundwater level of 25 meters and its rise from 1 to 10 meters, the settlement amount of about 5.5 mm ( For minimum foundation width and minimum water level rise) up to 49.5 mm (for maximum foundation width and maximum water level rise) was calculated. The results also show that the amount of settlement due to soil wetting is more dependent on the depth of the initial groundwater level and the rate of rising comparing with the dimensions and intensity of loading of the foundation. In the present study, with the help of experimental studies and based on the basic relationships of unsaturated soil mechanics theory, an analytical model is proposed to estimate soil settlements due to groundwater level rise after construction and its importance in accurately estimating the final soil subsidence. To determine the geotechnical parameters used in the design, experiments are performed either under saturated conditions or at natural moisture, and the effects of changes in moisture; in other words, drying and wetting paths are not considered. However, in the event of rainfall, the burst of water and sewage pipes, leakage from absorption wells, rising groundwater levels, and similar phenomena, the soil becomes wet and its behavior changes, eventually leading to softening and imposing additional settlement which can cause damage to the surface structures. In traditional laboratory studies, this wetting is partially evaluated using the double consolidation test with the calculation of the collapsibility index. This assessment method is limited to soil with fully saturation in a one-dimensional and uncontrolled matric suction device. The results are qualitative and without enough accurate for use in settlement calculations in wetting paths for unsaturated soils. In this study, the behavior of silty soil under consolidated isotropic tests under saturated and unsaturated conditions as well as controlled wetting of consolidated specimens at constant loading with the help of an unsaturated triaxial device was investigated; Afterward; using the results of laboratory studies with presenting a analytical model based on the basic relationships of unsaturated soil mechanics and the theory of calculation of terzagi consolidation, the effect of water level rising on the shallow foundation settlements under constant loading was investigated. The results showed that the amount of soil settlements due to this phenomenon is related to the initial density and soil consolidation properties in unsaturated conditions, volumetric change characteristics in the wetting paths, dimensions and intensity of foundation loading, initial groundwater level depth and ascent rising rate. In the present study, for a square foundation with dimensions of 10 to 20 meters with constant loading located on the silty soil mass, the depth of the initial groundwater level of 25 meters and its rise from 1 to 10 meters, the settlement amount of about 5.5 mm ( For minimum foundation width and minimum water level rise) up to 49.5 mm (for maximum foundation width and maximum water level rise) was calculated. The results also show that the amount of settlement due to soil wetting is more dependent on the depth of the initial groundwater level and the rate of rising comparing with the dimensions and intensity of loading of the foundation.

https://mcej.modares.ac.ir/article_12613_03c4207fa67ee3ea4f42c748980eda86.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 23 2 2023 05 22 Investigation and Laboratory Sensitivity Measurement of the Capabilities of the Large Scale Particle Image Velocimetry (LSPIV) in Determining the Flow Rate and Flow Field Investigation and Laboratory Sensitivity Measurement of the Capabilities of the Large Scale Particle Image Velocimetry (LSPIV) in Determining the Flow Rate and Flow Field 223 234 12614 10.22034/23.2.15 FA ASH. Noori Graduated from Master's degree, Department of Civil Engineering, Technical and Engineering Faculty, Kharazmi University, Tehran, Iran S. Mohajeri Assistant Professor, Department of Civil Engineering, Technical and Engineering Faculty, Kharazmi University, Tehran, Iran M. Nabipour PhD graduate,Department of Civil Engineering and Environment, Technical and Engineering Faculty, Tarbiat Modares University, Tehran, Iran M. Khani Graduated from Master's degree, Department of Civil Engineering, Technical and Engineering Faculty, Kharazmi University, Tehran, Iran M. Mehraein Assistant Professor, Department of Civil Engineering, Technical and Engineering Faculty, Kharazmi University, Tehran, Iran Journal Article In order to estimate the amount of flood damage, knowledge of flow characteristics such as speed and flow rate is very important. Nowadays, the use of large-scale particle image velocimetry method is used to estimate flow parameters and flow field in laboratory and field scale. But image processing in relation to important environmental parameters has not been well investigated. To be more precise, the effect of environmental parameters such as; The position of the camera, the speed coefficient, and the sensitivity of the probe window have not been measured. The basis of this research is based on image processing methods, through which flow rate and flow field are calculated. In this study, the capabilities of this method have been accurately measured on a laboratory scale in relation to effective environmental parameters. In this regard, the investigation window of this study shows that the window of 20 pixels provides better results in different depths. In relation to the position of the camera, the studies showed that the placement of the camera obliquely provides the desired results. Regarding the speed coefficient, the studies show that the coefficient between 0.85 and 0.9 provides the best results. The results of the research in laboratory conditions based on the depths of 12.5, 15.5 and 18.5 cm indicate that by using the large-scale particle surface velocimeter system, according to the selection of the optimal conditions, the selection of the appropriate computing network ; camera position; Selection of the search window optimization; hydraulic specifications as well as the appropriate selection of the speed coefficient; It estimates the values of flow rate and flow speed with optimal accuracy. The relative error values of discharge and flow velocity in this research based on the LSPIV method for depths of 12.5, 15.5 and 18.5 cm are equal to 6.5,3.1 and 2.1 percent. In order to estimate the amount of flood damage, knowledge of flow characteristics such as speed and flow rate is very important. Nowadays, the use of large-scale particle image velocimetry method is used to estimate flow parameters and flow field in laboratory and field scale. But image processing in relation to important environmental parameters has not been well investigated. To be more precise, the effect of environmental parameters such as; The position of the camera, the speed coefficient, and the sensitivity of the probe window have not been measured. The basis of this research is based on image processing methods, through which flow rate and flow field are calculated. In this study, the capabilities of this method have been accurately measured on a laboratory scale in relation to effective environmental parameters. In this regard, the investigation window of this study shows that the window of 20 pixels provides better results in different depths. In relation to the position of the camera, the studies showed that the placement of the camera obliquely provides the desired results. Regarding the speed coefficient, the studies show that the coefficient between 0.85 and 0.9 provides the best results. The results of the research in laboratory conditions based on the depths of 12.5, 15.5 and 18.5 cm indicate that by using the large-scale particle surface velocimeter system, according to the selection of the optimal conditions, the selection of the appropriate computing network ; camera position; Selection of the search window optimization; hydraulic specifications as well as the appropriate selection of the speed coefficient; It estimates the values of flow rate and flow speed with optimal accuracy. The relative error values of discharge and flow velocity in this research based on the LSPIV method for depths of 12.5, 15.5 and 18.5 cm are equal to 6.5,3.1 and 2.1 percent.

https://mcej.modares.ac.ir/article_12614_ed71773d43d53fa70ecf593c6582d9cc.pdf