Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 11 21 Using wavelet theory in the dynamic analyses of retaining walls coupled with soil medium Using wavelet theory in the dynamic analyses of retaining walls coupled with soil medium 7 21 12737 10.22034/24.6.7 FA AhmadReza Seifoddin Department of Civil Engineering, Faculty of Technology and Engineering, Shahrekord University, Shahrekord, Iran. Heisam Heidarzadeh Department of Civil Engineering, Faculty of Technology and Engineering, Shahrekord University, Shahrekord, Iran HamedReza Zarif Department of Civil Engineering, Faculty of Technology and Engineering, Shahrekord University, Shahrekord, Iran. Journal Article Retaining structure or retaining wall is a wall that acts as supporting structure and the stability of another structure. This wall is used for preventing collapse of soil and generally wherever lateral support is needed. The retaining wall can be designed as gravity, cantilever and supported. Considering that the retaining walls are essential in protecting the related structures to them, therefore, studying the dynamic behavior of these structures is very important due to the financial and human damages. Such structures should be stable against the forces acting on the wall. In addition to static loads, which are always an inseparable part of the calculations of such walls, forces such as cyclic forces caused by the movement of machinery and also dynamic forces caused by earthquake occur on the wall during the period of operation. These forces can be effected on retaining walls and should be investigated and evaluated. Trying to investigate and analyze the dynamic behavior of different retaining walls is one of the most challenging for different researchers. The wavelet theory in the dynamic analysis of the issues related to civil engineering is going to be widespread. This research aims to investigate the effect of using wavelet theory in the dynamic analyses of concrete retaining walls. For this purpose, a soil medium along with concrete retaining walls with different dimensions (heights) are considered. Dynamic analyses are performed based on the finite element method. In the first stage of modeling, the Sarpol-e Zahab earthquake record is filtered during four steps using the discrete wavelet theory. The numerical models are prepared and subjected to the available records. The percentage of the difference in the results of the analyses done with the records obtained from the different steps of filtering record with wavelet compared to the analyses done with the main record, along with the reduction of the time consumption, is evaluated. As expected, the best match of the post-filtering results to the main earthquake results is for the first-step filter. It can be seen that even the first step filter reduces the analysis time by about 60%. Based on the obtained results, the difference between the results obtained with the filtered records becomes less compared to the main earthquake with the increase in the height of the wall. It has also been observed that acceptable results are still obtained, and the analysis time is reduced by almost 80% until the third step filter. It should be noted that the Mohr-Coulomb behavioral model is used in the conducted analyzes in this research. This behavioral model is not inherently able to model hysteresis damping behavior at low strains. Therefore, this issue can affect the results of deformations and stresses obtained from dynamic analysis. However, the purpose of this research is to evaluate the performance of the wavelet in the dynamic analysis of the retaining wall. Considering that in all the analyses (both the performed analysis with the main earthquake and the performed analyzes with the wavelet filtered records) the same structure and trend are used, it can be concluded that the effect of using the wavelet compared to the main earthquake gives an acceptable overview and quality Retaining structure or retaining wall is a wall that acts as supporting structure and the stability of another structure. This wall is used for preventing collapse of soil and generally wherever lateral support is needed. The retaining wall can be designed as gravity, cantilever and supported. Considering that the retaining walls are essential in protecting the related structures to them, therefore, studying the dynamic behavior of these structures is very important due to the financial and human damages. Such structures should be stable against the forces acting on the wall. In addition to static loads, which are always an inseparable part of the calculations of such walls, forces such as cyclic forces caused by the movement of machinery and also dynamic forces caused by earthquake occur on the wall during the period of operation. These forces can be effected on retaining walls and should be investigated and evaluated. Trying to investigate and analyze the dynamic behavior of different retaining walls is one of the most challenging for different researchers. The wavelet theory in the dynamic analysis of the issues related to civil engineering is going to be widespread. This research aims to investigate the effect of using wavelet theory in the dynamic analyses of concrete retaining walls. For this purpose, a soil medium along with concrete retaining walls with different dimensions (heights) are considered. Dynamic analyses are performed based on the finite element method. In the first stage of modeling, the Sarpol-e Zahab earthquake record is filtered during four steps using the discrete wavelet theory. The numerical models are prepared and subjected to the available records. The percentage of the difference in the results of the analyses done with the records obtained from the different steps of filtering record with wavelet compared to the analyses done with the main record, along with the reduction of the time consumption, is evaluated. As expected, the best match of the post-filtering results to the main earthquake results is for the first-step filter. It can be seen that even the first step filter reduces the analysis time by about 60%. Based on the obtained results, the difference between the results obtained with the filtered records becomes less compared to the main earthquake with the increase in the height of the wall. It has also been observed that acceptable results are still obtained, and the analysis time is reduced by almost 80% until the third step filter. It should be noted that the Mohr-Coulomb behavioral model is used in the conducted analyzes in this research. This behavioral model is not inherently able to model hysteresis damping behavior at low strains. Therefore, this issue can affect the results of deformations and stresses obtained from dynamic analysis. However, the purpose of this research is to evaluate the performance of the wavelet in the dynamic analysis of the retaining wall. Considering that in all the analyses (both the performed analysis with the main earthquake and the performed analyzes with the wavelet filtered records) the same structure and trend are used, it can be concluded that the effect of using the wavelet compared to the main earthquake gives an acceptable overview and quality

https://mcej.modares.ac.ir/article_12737_a5f2b2528bd068e1643b5ec310cd5d8c.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 11 21 Determining of Sand behavior through model tests of Strip Footing with Micropile Skirts Determining of Sand behavior through model tests of Strip Footing with Micropile Skirts 23 37 12738 10.22034/24.6.23 FA Behrad Bakhtiari Department of Civil Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, Ahang Bld., Abouzar Bld., Basij Highway, Tehran, Iran. Arash Razmkhah Department of Civil Engineering, Faculty of Engineering, Islamic Azad University, South of Tehran Branch, Ahang Bld., Abouzar Bld., Basij Highway, Tehran, Iran. Hassan Ghasemzadeh Faculty of Civil Engineering, K.N. Toosi University of Technology, Mirdamade Ave, Tehran, Iran. Faradjollah Askari Geotechnical Engineering Research Centre, International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan Street, North Dibajee, Farmanieh, Tehran, Iran. Journal Article Recently, the modification of bearing capacity and the reduction in settlement of existing foundations and buildings has become one of the important topics in the field of geotechnical engineering. Also, the foundation of the buildings on the problematic and flowing sand bed, especially in the coastal strips is inevitable. In general, when faced with problematic soils such as loose soils with low load-bearing capacity, high settlement, liquefaction, disturbed soils, etc., there are two ways for geotechnical engineers, one of which is to use bearing elements in the soil and the other is to improve and modify the physical-mechanical properties of the soil mass. In addition to acting as a bearing and settlement-resistant element, the micro pile also improves the bearing strength of the surrounding soil due to the injection of cement slurry. In many projects, micro piles are used as structural elements. In fact, micro piles are small replacement piles (usually less than 300 mm in diameter) that are often accompanied by steel reinforcement and cement grout injection. Micro piles can be designed and used at any angle and for different purposes, including bearing axial and lateral loads, replacing conventional piles, or as part of a soil-pile system, depending on the purpose of the design. In this study, by physical modeling, the effect of using micro piles on the edge the foundation on sand bed was investigated. For this purpose, the effect of the boundary conditions of the chamber was first investigated. The parameters included the width of the foundation (B), the distance of the foundation from the end surface of the tank (Z), the distance of the foundation from the right/left wall of the chamber (X, X'), unreinforced bearing capacity (Q0) and unreinforced sand settlement (S0). Also, the investigation of the effect of the distance of the foundation from the lower surface of the steel chamber to the width of the foundation (B) showed that when the distance of the foundation from the lower surface of the chamber was less than twice the width of the foundation, the lower boundary affected the results of physical modeling. The evaluation of the lateral boundaries given the distance of the foundation from the chamber wall (X) to the width of the foundation showed that for X/B≥5, the lateral boundary had no effect on the results. Influences of various micropile skirt configurations were investigated, including micropile length (L) and spacing between two consecutive micropiles (S) on bearing capacity-settlement. The micropile skirts improved the bearing capacity of shallow foundations, depending on the L/B ratio and spacing between micropiles depending on the S/D ratio. Analysis of the results indicated that improved bearing capacity upon increasing the length of micropile skirt and reducing the spacing between two consecutive micropiles. Comparison of the pressure-settlement curves showed that in constant micropile lengths, the optimum Bearing Capacity Ratio (BCR) was in S/D=2. Further, the skirt piles reduced the settlement of strip footing. The Micropile Skirted Strip Footing (MSSF) led to increased failure surface and, depending on the pile length and spacing micropiles, it changed the failure pattern of the soil. Recently, the modification of bearing capacity and the reduction in settlement of existing foundations and buildings has become one of the important topics in the field of geotechnical engineering. Also, the foundation of the buildings on the problematic and flowing sand bed, especially in the coastal strips is inevitable. In general, when faced with problematic soils such as loose soils with low load-bearing capacity, high settlement, liquefaction, disturbed soils, etc., there are two ways for geotechnical engineers, one of which is to use bearing elements in the soil and the other is to improve and modify the physical-mechanical properties of the soil mass. In addition to acting as a bearing and settlement-resistant element, the micro pile also improves the bearing strength of the surrounding soil due to the injection of cement slurry. In many projects, micro piles are used as structural elements. In fact, micro piles are small replacement piles (usually less than 300 mm in diameter) that are often accompanied by steel reinforcement and cement grout injection. Micro piles can be designed and used at any angle and for different purposes, including bearing axial and lateral loads, replacing conventional piles, or as part of a soil-pile system, depending on the purpose of the design. In this study, by physical modeling, the effect of using micro piles on the edge the foundation on sand bed was investigated. For this purpose, the effect of the boundary conditions of the chamber was first investigated. The parameters included the width of the foundation (B), the distance of the foundation from the end surface of the tank (Z), the distance of the foundation from the right/left wall of the chamber (X, X'), unreinforced bearing capacity (Q0) and unreinforced sand settlement (S0). Also, the investigation of the effect of the distance of the foundation from the lower surface of the steel chamber to the width of the foundation (B) showed that when the distance of the foundation from the lower surface of the chamber was less than twice the width of the foundation, the lower boundary affected the results of physical modeling. The evaluation of the lateral boundaries given the distance of the foundation from the chamber wall (X) to the width of the foundation showed that for X/B≥5, the lateral boundary had no effect on the results. Influences of various micropile skirt configurations were investigated, including micropile length (L) and spacing between two consecutive micropiles (S) on bearing capacity-settlement. The micropile skirts improved the bearing capacity of shallow foundations, depending on the L/B ratio and spacing between micropiles depending on the S/D ratio. Analysis of the results indicated that improved bearing capacity upon increasing the length of micropile skirt and reducing the spacing between two consecutive micropiles. Comparison of the pressure-settlement curves showed that in constant micropile lengths, the optimum Bearing Capacity Ratio (BCR) was in S/D=2. Further, the skirt piles reduced the settlement of strip footing. The Micropile Skirted Strip Footing (MSSF) led to increased failure surface and, depending on the pile length and spacing micropiles, it changed the failure pattern of the soil.

https://mcej.modares.ac.ir/article_12738_889b8a538b90aab7d224bba4306971fb.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 11 21 Water Quality Monitoring and Eutrophication Simulation of Dez River Water Quality Monitoring and Eutrophication Simulation of Dez River 39 53 12739 10.22034/24.6.39 FA Sina Jahanimehr Jundi-Shapur university of technology, Dezful, Iran. M. Zakermoshfegh Jundi-Shapur university of technology, Dezful, Iran. B. Lashkar-Ara Jundi-shapur university of technology F. Gholinezhad General Department of environmental protection of Khuzestan province. Journal Article The biological response to high concentrations of nutrients such as phosphorus and nitrogen in a river is called eutrophication in water-resources engineering. Due to increasing withdrawals of water, successive dry years, and the discharge of urban, industrial, and agricultural wastewater into the Dez River, the quality of the river is being threatened. In this research, for the purpose of field monitoring and then simulating the eutrophication of Dez river, eight monitoring stations were selected considering the way pollutants enter the river. A number of water quality variables, including dissolved oxygen and water temperature, were measured directly by the portable device, while phosphate and nitrate variables were measured through sampling and laboratory tests. Then, the water quality simulation of the river with 18 Km of length was conducted by the HEC-RAS model. A comparison was made between the simulation results and the observed data, in which parameters including dissolved oxygen, temperature, nitrate, and phosphate were in good agreement with the observed data. To measure the accuracy of the model, the root mean square error (RMSE) statistical function was used. The results of the sensitivity analysis showed that the amount of dissolved oxygen is more sensitive to the parameters of oxygen demand and wind speed function coefficients, and also the model is less sensitive to the parameters of diffusion coefficient and dust coefficient, and the change of these two parameters has no effect on the dissolved oxygen graph. This was used in the model calibration process so that only parameters affecting the model were used in the calibration process. The results showed that the variables of nitrate, water temperature, dissolved oxygen and phosphate were modeled with appropriate accuracy. In model calibration, RMSE values for nitrate, water temperature, dissolved oxygen and phosphate parameters were calculated as 0.25, 0.29, 0.67 and 0.67 mg/L, respectively. Also, the results of the model confirmation show the acceptable compatibility of the simulated and observed values. After the model Sensitivity analysis, calibration and validation, it was used to simulate the river's response to the nutrition reduction scenario, which involved the impact of the discharge increasing on the concentration reduction of nutrition in the river. The results of nitrate and phosphate concentration changes during the simulation period in the river course showed that the amount of phosphate and nitrate concentration increases from the upstream to the downstream of the river. Also, the simulation results for the dissolved oxygen variable show that in most of the sampling months, the concentration of dissolved oxygen is higher than 4 mg/l. The simulation results showed that in the scenario of discharge increasing, the nutrition concentration reduced significantly. On average, in all the stations, with the increase of the flow by 70 cubic meters per second, there is an increase in DO by 0.5-0.9 mg/l, a decrease in nitrate between 0.4 and 6 mg/l, and a decrease in phosphate by 3 0.0 mg/l and a decrease of 0.5 to 1 degree in water temperature. This shows the impact of this scenario on the amount of nitrate and phosphate variables, which are the main factors in creating the phenomenon of eutrophication and algal growth. The biological response to high concentrations of nutrients such as phosphorus and nitrogen in a river is called eutrophication in water-resources engineering. Due to increasing withdrawals of water, successive dry years, and the discharge of urban, industrial, and agricultural wastewater into the Dez River, the quality of the river is being threatened. In this research, for the purpose of field monitoring and then simulating the eutrophication of Dez river, eight monitoring stations were selected considering the way pollutants enter the river. A number of water quality variables, including dissolved oxygen and water temperature, were measured directly by the portable device, while phosphate and nitrate variables were measured through sampling and laboratory tests. Then, the water quality simulation of the river with 18 Km of length was conducted by the HEC-RAS model. A comparison was made between the simulation results and the observed data, in which parameters including dissolved oxygen, temperature, nitrate, and phosphate were in good agreement with the observed data. To measure the accuracy of the model, the root mean square error (RMSE) statistical function was used. The results of the sensitivity analysis showed that the amount of dissolved oxygen is more sensitive to the parameters of oxygen demand and wind speed function coefficients, and also the model is less sensitive to the parameters of diffusion coefficient and dust coefficient, and the change of these two parameters has no effect on the dissolved oxygen graph. This was used in the model calibration process so that only parameters affecting the model were used in the calibration process. The results showed that the variables of nitrate, water temperature, dissolved oxygen and phosphate were modeled with appropriate accuracy. In model calibration, RMSE values for nitrate, water temperature, dissolved oxygen and phosphate parameters were calculated as 0.25, 0.29, 0.67 and 0.67 mg/L, respectively. Also, the results of the model confirmation show the acceptable compatibility of the simulated and observed values. After the model Sensitivity analysis, calibration and validation, it was used to simulate the river's response to the nutrition reduction scenario, which involved the impact of the discharge increasing on the concentration reduction of nutrition in the river. The results of nitrate and phosphate concentration changes during the simulation period in the river course showed that the amount of phosphate and nitrate concentration increases from the upstream to the downstream of the river. Also, the simulation results for the dissolved oxygen variable show that in most of the sampling months, the concentration of dissolved oxygen is higher than 4 mg/l. The simulation results showed that in the scenario of discharge increasing, the nutrition concentration reduced significantly. On average, in all the stations, with the increase of the flow by 70 cubic meters per second, there is an increase in DO by 0.5-0.9 mg/l, a decrease in nitrate between 0.4 and 6 mg/l, and a decrease in phosphate by 3 0.0 mg/l and a decrease of 0.5 to 1 degree in water temperature. This shows the impact of this scenario on the amount of nitrate and phosphate variables, which are the main factors in creating the phenomenon of eutrophication and algal growth.

https://mcej.modares.ac.ir/article_12739_597073e68fcefaa6bdf39ca6b399c28c.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 03 01 Physical Modeling of Sand Beds Using a New Approacha of Rainer System Physical Modeling of Sand Beds Using a New Approacha of Rainer System 55 68 12740 10.22034/24.6.55 FA Ehsan Saeedi Department of Civil Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, Ahang Bld., Abouzar Bld., Basij Highway, Tehran, Iran. Arash Razmkhah Department of Civil Engineering, Faculty of Engineering, South Tehran Branch, Islamic Azad University, Ahang Bld., Abouzar Bld., Basij Highway, Tehran, Iran. Mohsen Kamalian Geotechnical Engineering Research Centre, International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan Street, North Dibajee, Farmanieh, Tehran, Iran. Faradjollah Askari Geotechnical Engineering Research Centre, International Institute of Earthquake Engineering and Seismology (IIEES), No. 21, Arghavan Street, North Dibajee, Farmanieh, Tehran, Iran. Journal Article It is common to apply physical modeling for a more precise investigation of phenomena in geotechnical engineering. The reconstitution of specimens is an appropriate way to study soil behavioral parameters in laboratories due to the restrictions of acceptable undisturbed sample preparation. Reconstitution of the sand sample is one of the most well-known challenges of physical modeling. One of the most significant aspects of physical modeling geotechnical engineering is the repeatability of bed preparation. The reconstitution of sample and bed preparation in physical modeling are divided into two general approaches, depending on the type of porosity control employed. Methods where the porosity is adjusted after deposition, is only appropriate for dense beds with diverse layers. This category includes the methods of tamping and vibration. Another methods where the porosity is controlled during deposition, which aim at obtaining any porosity within the maximum-minimum porosity limits of the material that is pluviation technique. Because of the favorable conditions and prompt modeling it enables, the preparation of layers by the pluviation technique is one of the most reliable bed preparation methods. The pluviation technique can be divided into three categories, air pluviation, vacuum pluviation, and water pluviation. In addition, each category is divided into three minor subgroups that monitor sand-rain outflow intensity as follows, controlling the deposition intensity of sand output from single or multiple nozzles of various shapes, controlling the deposition intensity of the sand output from single or multiple sieves, controlling the deposition intensity of the sand output from longitudinal aperture (curtain pluviation). The effective parameters on pluviation system are deposition intensity and fall height. Deposition intensity, itself, is affected by aperture width, traveling pluviator speed, and the number of opening. The sand reconstitution technique must properly provide real sample conditions in a wide range of soil density (loose to dense), the uniform void ratio in the entire reconstructed specimen, fully saturated conditions for undrained status, the samples should be well mixed without particle size segregation, regardless of particle size gradation and simulation of the studied depositional fabric characteristic. In this research, a novel approach focusing on a traveling sand pluviator with two apertures was developed for the reconstitution of large-scale samples. Experiments on Iran’s Firuzkuh sand (#161) _Silica sand with fine-grained content of about 1% that is known as the standard sand in Iran and has been the most widely used sand for laboratory studies_ evaluated the effects of opening width, traveling pluviator speed, fall height, and number of openings on deposition intensity and relative density. The results showed that a decrease in deposition intensity is correlated with a decrease in aperture width and an increase in traveling pluviator speed, which significantly enhances relative density. With changes in the effective parameters, a broad range of relative densities could be obtained—from 12 to 93 percent. Comparisons between the findings of the experiments revealed that double-aperture pluviation plate, given the increases in sand outlet and deposition intensity, had a density equivalent to that of single-aperture pluviation plate whit; moreover, each aperture behaved as separate, resulting in prompt sand bed preparation. The findings also revealed that increase in fall height leads to increase in relative density. It is common to apply physical modeling for a more precise investigation of phenomena in geotechnical engineering. The reconstitution of specimens is an appropriate way to study soil behavioral parameters in laboratories due to the restrictions of acceptable undisturbed sample preparation. Reconstitution of the sand sample is one of the most well-known challenges of physical modeling. One of the most significant aspects of physical modeling geotechnical engineering is the repeatability of bed preparation. The reconstitution of sample and bed preparation in physical modeling are divided into two general approaches, depending on the type of porosity control employed. Methods where the porosity is adjusted after deposition, is only appropriate for dense beds with diverse layers. This category includes the methods of tamping and vibration. Another methods where the porosity is controlled during deposition, which aim at obtaining any porosity within the maximum-minimum porosity limits of the material that is pluviation technique. Because of the favorable conditions and prompt modeling it enables, the preparation of layers by the pluviation technique is one of the most reliable bed preparation methods. The pluviation technique can be divided into three categories, air pluviation, vacuum pluviation, and water pluviation. In addition, each category is divided into three minor subgroups that monitor sand-rain outflow intensity as follows, controlling the deposition intensity of sand output from single or multiple nozzles of various shapes, controlling the deposition intensity of the sand output from single or multiple sieves, controlling the deposition intensity of the sand output from longitudinal aperture (curtain pluviation). The effective parameters on pluviation system are deposition intensity and fall height. Deposition intensity, itself, is affected by aperture width, traveling pluviator speed, and the number of opening. The sand reconstitution technique must properly provide real sample conditions in a wide range of soil density (loose to dense), the uniform void ratio in the entire reconstructed specimen, fully saturated conditions for undrained status, the samples should be well mixed without particle size segregation, regardless of particle size gradation and simulation of the studied depositional fabric characteristic. In this research, a novel approach focusing on a traveling sand pluviator with two apertures was developed for the reconstitution of large-scale samples. Experiments on Iran’s Firuzkuh sand (#161) _Silica sand with fine-grained content of about 1% that is known as the standard sand in Iran and has been the most widely used sand for laboratory studies_ evaluated the effects of opening width, traveling pluviator speed, fall height, and number of openings on deposition intensity and relative density. The results showed that a decrease in deposition intensity is correlated with a decrease in aperture width and an increase in traveling pluviator speed, which significantly enhances relative density. With changes in the effective parameters, a broad range of relative densities could be obtained—from 12 to 93 percent. Comparisons between the findings of the experiments revealed that double-aperture pluviation plate, given the increases in sand outlet and deposition intensity, had a density equivalent to that of single-aperture pluviation plate whit; moreover, each aperture behaved as separate, resulting in prompt sand bed preparation. The findings also revealed that increase in fall height leads to increase in relative density.

https://mcej.modares.ac.ir/article_12740_e6b73239f1c528d79233c34ffe4ccf8b.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 11 21 Effect of frequency dependency of impedance functions on seismic damage index of soil-structure systems Effect of frequency dependency of impedance functions on seismic damage index of soil-structure systems 69 80 12741 10.22034/24.6.69 FA Hanieh Zahedi University of Mazandaran Behnoud Ganjavi Associate Professor, Department of Civil Engineering, Mazandaran University, Babolsar 0000-0002-4414-5063 Majid Bararnia PhD, Department of Civil, Water and Environmental Engineering, Shahid Beheshti University, Tehran Journal Article In seismic analysis and design of conventional structures, it is generally assumed that the soil beneath the foundation is rigid and, thus, its flexibility is not taken into account. Soil flexibility can affect the response of structures through complex phenomenon of dynamics soil-structure interaction (SSI) effect. It is believed that effective soil and structural parameters could in some case significantly influence seismic response of structures in different manners and conditions. In this study, through an intensive parametric study, the effect of frequency dependency of impedance functions on constant-ductility damage index parameter of soil-structure SDOF systems subjected to ordinary strong ground motions were investigated. To this end, the soil-structure system was modeled by sub-structure method and the foundation was modeled as a homogeneous elastic half-space using the concept of the cone model. The soil-structure systems with shallow foundation were modeled based on various SSI key parameters, and were then analyzed under 15 earthquake ground motions recorded on soft soils. Results of this study show that, in average, the maximum effect of excitation frequency dependency on seismic damage index is referred to the intensive SSI models, slender structures and with low level of inelastic behavior, which, in critical case, will occur in one or limited values of fundamental period. The maximum mean value is about 13.56% which cannot be considered as a criterion for practical application. Therefore, to have a logical criterion for practical purpose, the average values of entire periodic region in 15 earthquake ground motions were computed and, then, the maximum value, i.e., 5.76, was considered to make a decision. Overall, the results indicate that for soil-structure SDOF systems with shallow foundation, frequency dependency of impedance functions on damage index of structures subjected to earthquake ground motions would not have a remarkable effect and thus can be practically ignored in seismic analysis and design of soil-structures systems with shallow foundations. This finding being debated by researchers can lead to using a simple soil-structure system with less computational time and effort. In seismic analysis and design of conventional structures, it is generally assumed that the soil beneath the foundation is rigid and, thus, its flexibility is not taken into account. Soil flexibility can affect the response of structures through complex phenomenon of dynamics soil-structure interaction (SSI) effect. It is believed that effective soil and structural parameters could in some case significantly influence seismic response of structures in different manners and conditions. In this study, through an intensive parametric study, the effect of frequency dependency of impedance functions on constant-ductility damage index parameter of soil-structure SDOF systems subjected to ordinary strong ground motions were investigated. To this end, the soil-structure system was modeled by sub-structure method and the foundation was modeled as a homogeneous elastic half-space using the concept of the cone model. The soil-structure systems with shallow foundation were modeled based on various SSI key parameters, and were then analyzed under 15 earthquake ground motions recorded on soft soils. Results of this study show that, in average, the maximum effect of excitation frequency dependency on seismic damage index is referred to the intensive SSI models, slender structures and with low level of inelastic behavior, which, in critical case, will occur in one or limited values of fundamental period. The maximum mean value is about 13.56% which cannot be considered as a criterion for practical application. Therefore, to have a logical criterion for practical purpose, the average values of entire periodic region in 15 earthquake ground motions were computed and, then, the maximum value, i.e., 5.76, was considered to make a decision. Overall, the results indicate that for soil-structure SDOF systems with shallow foundation, frequency dependency of impedance functions on damage index of structures subjected to earthquake ground motions would not have a remarkable effect and thus can be practically ignored in seismic analysis and design of soil-structures systems with shallow foundations. This finding being debated by researchers can lead to using a simple soil-structure system with less computational time and effort.

https://mcej.modares.ac.ir/article_12741_b2651c9921723afdfd04ed61ec302a6b.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 03 01 Development of thermal-insulating high-performance geopolymer concrete containing rubber and PET powders with calcium oxide-activated materials Development of thermal-insulating high-performance geopolymer concrete containing rubber and PET powders with calcium oxide-activated materials 81 92 12742 10.22034/24.6.81 FA Hadi Bahmani PhD, Department of Civil Engineering, Isfahan University of Technology (IUT), Isfahan, Davood Mostofinejad Professor, Department of Civil Engineering, Isfahan University of Technology (IUT), Isfahan Journal Article Prior research has not explored the creation of concrete with superior thermal insulation properties using calcium oxide-activated materials. Furthermore, the impact of substituting large proportions of sand with worn rubber powder and PET on the mechanical and thermal characteristics of high-performance geopolymer concrete remains uninvestigated. This study addresses these gaps by examining the development of geopolymeric concrete with enhanced thermal insulation properties using calcium oxide-activated materials. A novel mixing method has been devised to improve the compaction of thermally insulating concrete, which includes calcium oxide-activated slag. For the purposes of this research, worn rubber powder and PET powder have replaced 10%, 20%, 30%, 40%, and 50% of the aggregates. The mechanical properties of the concrete were determined through compressive strength, four-point bending, and tensile strength tests. Lastly, the thermal conductivity coefficient was tested to ascertain the thermal properties of the developed concrete. The findings revealed that in the developed concrete, substituting 10% of the aggregates with worn rubber powder or PET powder increased the energy absorption capacity of the concrete by 143% and 107%, respectively, while its mechanical properties decreased by 10% and 7%, respectively. Moreover, using 50% worn rubber powder and PET as aggregate substitutes reduced the samples’ thermal conductivity by 70% and 60%, respectively. Prior research has not explored the creation of concrete with superior thermal insulation properties using calcium oxide-activated materials. Furthermore, the impact of substituting large proportions of sand with worn rubber powder and PET on the mechanical and thermal characteristics of high-performance geopolymer concrete remains uninvestigated. This study addresses these gaps by examining the development of geopolymeric concrete with enhanced thermal insulation properties using calcium oxide-activated materials. A novel mixing method has been devised to improve the compaction of thermally insulating concrete, which includes calcium oxide-activated slag. For the purposes of this research, worn rubber powder and PET powder have replaced 10%, 20%, 30%, 40%, and 50% of the aggregates. The mechanical properties of the concrete were determined through compressive strength, four-point bending, and tensile strength tests. Lastly, the thermal conductivity coefficient was tested to ascertain the thermal properties of the developed concrete. The findings revealed that in the developed concrete, substituting 10% of the aggregates with worn rubber powder or PET powder increased the energy absorption capacity of the concrete by 143% and 107%, respectively, while its mechanical properties decreased by 10% and 7%, respectively. Moreover, using 50% worn rubber powder and PET as aggregate substitutes reduced the samples’ thermal conductivity by 70% and 60%, respectively.

https://mcej.modares.ac.ir/article_12742_97208e4cb6de9c04b325c2185316439f.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 11 21 Effects of acceleration and frequency of input motion on the seismic behavior of offshore wind turbine supported by monopile Effects of acceleration and frequency of input motion on the seismic behavior of offshore wind turbine supported by monopile 95 106 12743 10.22034/24.6.95 FA Alireza Bateni Faculty of Civil Eng., University of Tehran Majid Moradi Associate Prof., Faculty of Civil Eng., University of Tehran Journal Article In recent years, the surge in pollutants from fossil fuels has prompted a heightened emphasis on transitioning to clean and renewable energies, with a particular focus on wind power. The deployment of offshore wind turbines stands out as a prominent approach to harnessing wind energy. However, these turbines consistently endure cyclic loading induced by wind, waves, and ocean currents, necessitating foundations that exhibit robust resistance to such repeated stress. Offshore wind turbines are commonly mounted on monopiles, singular tubular structures with diameters ranging from 2 to 8 meters. While these turbines were initially deployed in Europe, their utilization has expanded to seismically active regions such as USA, China and Japan in recent years, owing to their numerous advantages. As a result, their seismic behavior has become a subject of interest. The seismic design of these turbines, similar to other structures, should be based on past earthquakes in the region and adapted to saturated conditions. Until now, a multitude of studies has delved into these turbines, predominantly through numerical research. However, the scarcity of experimental investigations into their seismic behavior has left the impacts of acceleration and frequency of input motion on their design not thoroughly explored. Furthermore, in certain instances, the design of these turbines makes reference to regulations designed for dry conditions. This research investigates the impact of acceleration and frequency of input motion on the seismic response of offshore wind turbines through 9 experiments conducted on samples using a 1g shaking table. Various input motion with different acceleration and frequencies were applied under both dry and saturated conditions, allowing for a comprehensive comparison of turbine behavior. The modeling process included creating a soil environment with specific dimensions through dry deposition and compaction, followed by the embedding of sensors for measuring acceleration and pore water pressure. After these initial steps, the monopile was vertically drove into the soil, and the superstructure was assembled. Displacement sensors were installed to capture the superstructure's displacement at different heights and to measure the settlement of the soil surface on the samples. Then the sample started to be saturated from the bottom of the box and water was placed on the soil surface up to 10 cm to model sea water. Subsequently, harmonic sinusoidal loading was applied, with 9 loadings featuring frequencies of 10 Hz, 5 Hz, and 3 Hz, along with maximum accelerations of 0.2 g, 0.3 g, and 0.4 g, respectively. As indicated by the findings of this research, turbine seismic behavior becomes significantly more critical during resonance phenomena in the most critical state, with the impact of other factors on seismic performance proving negligible in such instances. Moreover, the seismic behavior of these turbines consistently exhibits more critical behavior in saturated conditions compared to dry conditions. In saturated conditions, acceleration amplification in surface soil layers is up to 5 times, profoundly influencing seismic performance, whereas in dry conditions, amplification is limited to 1.2 times. Additionally, as excitation acceleration rises and excitation frequency decreases, the superstructure's maximum acceleration and the turbine's maximum and permanent displacement all increase, signifying a more critical behavior of this structure. In recent years, the surge in pollutants from fossil fuels has prompted a heightened emphasis on transitioning to clean and renewable energies, with a particular focus on wind power. The deployment of offshore wind turbines stands out as a prominent approach to harnessing wind energy. However, these turbines consistently endure cyclic loading induced by wind, waves, and ocean currents, necessitating foundations that exhibit robust resistance to such repeated stress. Offshore wind turbines are commonly mounted on monopiles, singular tubular structures with diameters ranging from 2 to 8 meters. While these turbines were initially deployed in Europe, their utilization has expanded to seismically active regions such as USA, China and Japan in recent years, owing to their numerous advantages. As a result, their seismic behavior has become a subject of interest. The seismic design of these turbines, similar to other structures, should be based on past earthquakes in the region and adapted to saturated conditions. Until now, a multitude of studies has delved into these turbines, predominantly through numerical research. However, the scarcity of experimental investigations into their seismic behavior has left the impacts of acceleration and frequency of input motion on their design not thoroughly explored. Furthermore, in certain instances, the design of these turbines makes reference to regulations designed for dry conditions. This research investigates the impact of acceleration and frequency of input motion on the seismic response of offshore wind turbines through 9 experiments conducted on samples using a 1g shaking table. Various input motion with different acceleration and frequencies were applied under both dry and saturated conditions, allowing for a comprehensive comparison of turbine behavior. The modeling process included creating a soil environment with specific dimensions through dry deposition and compaction, followed by the embedding of sensors for measuring acceleration and pore water pressure. After these initial steps, the monopile was vertically drove into the soil, and the superstructure was assembled. Displacement sensors were installed to capture the superstructure's displacement at different heights and to measure the settlement of the soil surface on the samples. Then the sample started to be saturated from the bottom of the box and water was placed on the soil surface up to 10 cm to model sea water. Subsequently, harmonic sinusoidal loading was applied, with 9 loadings featuring frequencies of 10 Hz, 5 Hz, and 3 Hz, along with maximum accelerations of 0.2 g, 0.3 g, and 0.4 g, respectively. As indicated by the findings of this research, turbine seismic behavior becomes significantly more critical during resonance phenomena in the most critical state, with the impact of other factors on seismic performance proving negligible in such instances. Moreover, the seismic behavior of these turbines consistently exhibits more critical behavior in saturated conditions compared to dry conditions. In saturated conditions, acceleration amplification in surface soil layers is up to 5 times, profoundly influencing seismic performance, whereas in dry conditions, amplification is limited to 1.2 times. Additionally, as excitation acceleration rises and excitation frequency decreases, the superstructure's maximum acceleration and the turbine's maximum and permanent displacement all increase, signifying a more critical behavior of this structure.

https://mcej.modares.ac.ir/article_12743_701348eb3b6b2574acfaa8058063dc58.pdf

Tarbiat Modares University Modares Civil Engineering Journal 2476-6763 24 6 2024 03 01 Damage detection method utilizing modal strain energy and modal flexibility damage indexes and deep neural network in steel beams Damage detection method utilizing modal strain energy and modal flexibility damage indexes and deep neural network in steel beams 107 120 12744 10.22034/24.6.107 FA Sara Zalaghi Department of Civil Engineering, Science and Research Branch, Islamic Azad University Armin Aziminejad Department of Civil Engineering, Science and Research Branch, Islamic Azad University Hossein Rahami School of Engineering Science, College of Engineering, University of Tehran Abdolreza Sarvghad Moghadam International Institute of Earthquake Engineering and Seismology (IIEES), Tehran, Iran Mirhamid Hosseini Department of Civil Engineering, Science and Research Branch, Islamic Azad University Journal Article Civil structures inevitably undergo damage over time due to various reasons such as environmental changes, material aging, load variations, and insufficient maintenance. Monitoring these structures, especially aging ones, is crucial to detect damage early on and implement suitable retrofitting measures, ensuring their continued safe and reliable operation without unexpected failures. Consequently, there has been significant research in this field, focusing on damage detection in both simple and complex structures. Health monitoring of highway bridges is essential for achieving a reliable transportation system. The vibration-based damage detection method uses changes in the vibrational properties of structures to detect damages and ensure a healthy state. In this study, the absolute value of the modal flexibility damage index and the modal strain energy damage index simultaneously are utilized to prevent unsafe decisions. These absolute values of modal strain energy and flexibility damage indexes are utilized as the bases for training deep neural networks (DNNs). These indexes are applied to provide safe decisions and reliable damage evaluation in steel girder of the highway bridges. The convolution neural network (CNN) is utilized for damage quantification estimation. The CNN is one of the deep learning models that can currently be applied in 2D dominant approaches, such as pattern recognition and speech recognition. In addition, these networks can utilize the 1D time domain and vibrational signal data via the convolutional layer. The initial stage of CNN model comprises combined convolutional and pooling layers that apply different filters to extract features. Following this, fully connected layers, similar to a hidden layer of a multilayer perceptron are incorporated. Ultimately, these layers are classified together with a softmax layer. The convolution layer acts as a filter that convolutes the input layer with a set of weights, adding bias and applying an activation function to the outcome. Gradient descent momentum methods (SGDM) can be employed to optimize the parameters in CNN network architecture. SGDM estimates the gradient with high velocity in any dimension. This method mitigates issues such as jittering and saddle points by utilizing high-velocity inconsistent gradient dimensions and the SGD gradients, respectively. Additionally, when the Current gradient approaches zero, the SGDM provides some momentum. The convolution neural network is trained to utilize damage indexes obtained from numerical simulation of the validated finite element model of the bridge. The damage indexes as the inputs for the neural network, which are achieved from different damage scenarios. Once network training and validation are completed, a well-trained neural network is used to detect, localize, and quantify the intensity of unknown damages. The proposed method overcomes previous damage detection problems such as false positive indications, the unreliability of a single damage index, and insufficient precision in determining the intensity. The results revealed that the presented method, based on the dual updated damage indexes and CNN, practically and accurately identified unspecified single damages' location and severity in multi-span beams. The new training method of deep neural network systems overcomes some shortcomings in ANN. Moreever, this deep neural network training scheme can reduce the need for huge amounts of input data and enhance the accuracy of network training. The method is capable in predicting single damage scenarios in steel beam. Civil structures inevitably undergo damage over time due to various reasons such as environmental changes, material aging, load variations, and insufficient maintenance. Monitoring these structures, especially aging ones, is crucial to detect damage early on and implement suitable retrofitting measures, ensuring their continued safe and reliable operation without unexpected failures. Consequently, there has been significant research in this field, focusing on damage detection in both simple and complex structures. Health monitoring of highway bridges is essential for achieving a reliable transportation system. The vibration-based damage detection method uses changes in the vibrational properties of structures to detect damages and ensure a healthy state. In this study, the absolute value of the modal flexibility damage index and the modal strain energy damage index simultaneously are utilized to prevent unsafe decisions. These absolute values of modal strain energy and flexibility damage indexes are utilized as the bases for training deep neural networks (DNNs). These indexes are applied to provide safe decisions and reliable damage evaluation in steel girder of the highway bridges. The convolution neural network (CNN) is utilized for damage quantification estimation. The CNN is one of the deep learning models that can currently be applied in 2D dominant approaches, such as pattern recognition and speech recognition. In addition, these networks can utilize the 1D time domain and vibrational signal data via the convolutional layer. The initial stage of CNN model comprises combined convolutional and pooling layers that apply different filters to extract features. Following this, fully connected layers, similar to a hidden layer of a multilayer perceptron are incorporated. Ultimately, these layers are classified together with a softmax layer. The convolution layer acts as a filter that convolutes the input layer with a set of weights, adding bias and applying an activation function to the outcome. Gradient descent momentum methods (SGDM) can be employed to optimize the parameters in CNN network architecture. SGDM estimates the gradient with high velocity in any dimension. This method mitigates issues such as jittering and saddle points by utilizing high-velocity inconsistent gradient dimensions and the SGD gradients, respectively. Additionally, when the Current gradient approaches zero, the SGDM provides some momentum. The convolution neural network is trained to utilize damage indexes obtained from numerical simulation of the validated finite element model of the bridge. The damage indexes as the inputs for the neural network, which are achieved from different damage scenarios. Once network training and validation are completed, a well-trained neural network is used to detect, localize, and quantify the intensity of unknown damages. The proposed method overcomes previous damage detection problems such as false positive indications, the unreliability of a single damage index, and insufficient precision in determining the intensity. The results revealed that the presented method, based on the dual updated damage indexes and CNN, practically and accurately identified unspecified single damages' location and severity in multi-span beams. The new training method of deep neural network systems overcomes some shortcomings in ANN. Moreever, this deep neural network training scheme can reduce the need for huge amounts of input data and enhance the accuracy of network training. The method is capable in predicting single damage scenarios in steel beam.

https://mcej.modares.ac.ir/article_12744_829807aa78485041f87d209b458fcdf3.pdf