Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Control of Offshore Jacket Platform under Wave Loads Using Self-Powered Semi-Active Tuned Mass Damper Control of Offshore Jacket Platform under Wave Loads Using Self-Powered Semi-Active Tuned Mass Damper 247 264 5019 10.22060/ceej.2022.21295.7707 FA Mazyar Fahimi Farzam Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran Babak Alinejad Department of Civil Engineering, Faculty of Engineering, University of Maragheh, Maragheh, Iran Rasool Maroofiazar Department of Mechanic Engineering. Faculty of Engineering University of Maragheh. Maragheh. Iran Motasam Mousaviyan Safakhaneh Department of Civil Engineering University of Maragheh. Maragheh. Iran Journal Article 2022 05 18 Offshore jacket platforms play an important role in the oil and energy industry, so controlling the vibrations of these structures and increasing their useful life is of great interest. In this study, the dynamic response of an offshore jacket platform has been investigated under the effect of wave load with a return period of 100 years. To reduce the dynamic response of the platform deck, a self-powered semi-active mass damper (SP-SATMD) was used and its mass ratio was set to 3% by default. The magneto-rheological damper (MR) energy in the semi-active tuned mass damper is supplied by the vibration of the tuned mass damper (TMD) through an energy harvesting system. This system includes DC direct current generator, rack, and pinion. The rack and pinion convert the linear motion of the TMD into an angular motion and apply it to a DC generator to generate the required electrical energy. The energy harvesting system can also act as an electromagnetic damper (EM) and a proportional control algorithm in determining the damping of the magneto-rheological damper. The results show that the maximum displacement and absolute acceleration of the deck of the controlled platform with a semi-active control strategy decreased by 15 and 16.24%, respectively, compared to the uncontrolled structure. Offshore jacket platforms play an important role in the oil and energy industry, so controlling the vibrations of these structures and increasing their useful life is of great interest. In this study, the dynamic response of an offshore jacket platform has been investigated under the effect of wave load with a return period of 100 years. To reduce the dynamic response of the platform deck, a self-powered semi-active mass damper (SP-SATMD) was used and its mass ratio was set to 3% by default. The magneto-rheological damper (MR) energy in the semi-active tuned mass damper is supplied by the vibration of the tuned mass damper (TMD) through an energy harvesting system. This system includes DC direct current generator, rack, and pinion. The rack and pinion convert the linear motion of the TMD into an angular motion and apply it to a DC generator to generate the required electrical energy. The energy harvesting system can also act as an electromagnetic damper (EM) and a proportional control algorithm in determining the damping of the magneto-rheological damper. The results show that the maximum displacement and absolute acceleration of the deck of the controlled platform with a semi-active control strategy decreased by 15 and 16.24%, respectively, compared to the uncontrolled structure.

https://ceej.aut.ac.ir/article_5019_53fdae58e861476b182b0cd6beade809.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Optimization of the Clay Core of Earth Dams with Regression Method Optimization of the Clay Core of Earth Dams with Regression Method 265 278 5021 10.22060/ceej.2022.21205.7651 FA Mostafa Zalnejad Civil Engineering Department Kharazmi University,Tehran,Iran Seyed Shahab Emamzadeh Civil Engineering Department, Kharazmi University. Tehran Journal Article 2022 03 11 In the optimal design for the core cross-section of an earth dam, the type of material, its dimensions, and its shape are very important. So with the least volume of materials, it has the greatest effect in reducing the amount of seepage from the dam body and maintaining its stability. The purpose of this research is to develop a model for optimizing the core geometry of Hajilerchai dam near Tabriz City based on the integration of the equations obtained from the simulation of seepage, hydraulic gradient, and stability reliability factor with the Simplex algorithm. In this study, two objective functions were considered, one is the volume of soil material per unit length of the dam and the other is the seepage rate from the dam body. Then, by defining 50 different sections of the core of the earth dam and using the results of numerical analysis of seepage regression relationships, stability coefficient and hydraulic gradient were obtained. To validate the regression relationships, the values of stability coefficient, hydraulic gradient, and seepage obtained from the optimal core model were compared with the results obtained from GeoStudio software models in three sections. This comparison showed a high correlation of about 99%. The results of the model developed to determine the optimal dimensions of the earth dam core were compared with the actual dimensions of the Hajilerchai dam which indicated a reduction in the volume of materials required for the construction of the dam core by about 12%, which also provides the necessary stability. In the optimal design for the core cross-section of an earth dam, the type of material, its dimensions, and its shape are very important. So with the least volume of materials, it has the greatest effect in reducing the amount of seepage from the dam body and maintaining its stability. The purpose of this research is to develop a model for optimizing the core geometry of Hajilerchai dam near Tabriz City based on the integration of the equations obtained from the simulation of seepage, hydraulic gradient, and stability reliability factor with the Simplex algorithm. In this study, two objective functions were considered, one is the volume of soil material per unit length of the dam and the other is the seepage rate from the dam body. Then, by defining 50 different sections of the core of the earth dam and using the results of numerical analysis of seepage regression relationships, stability coefficient and hydraulic gradient were obtained. To validate the regression relationships, the values of stability coefficient, hydraulic gradient, and seepage obtained from the optimal core model were compared with the results obtained from GeoStudio software models in three sections. This comparison showed a high correlation of about 99%. The results of the model developed to determine the optimal dimensions of the earth dam core were compared with the actual dimensions of the Hajilerchai dam which indicated a reduction in the volume of materials required for the construction of the dam core by about 12%, which also provides the necessary stability.

https://ceej.aut.ac.ir/article_5021_2fd5d41ec6cfab47e32164d5624269b1.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Numerical investigation of the effects of thermal expansion coefficient of pile and soil on the mechanical response of energy pile Numerical investigation of the effects of thermal expansion coefficient of pile and soil on the mechanical response of energy pile 279 300 5025 10.22060/ceej.2022.21718.7807 FA Mohammad Reza Sadeghzadeh Civil Engineering Faculty, Sharif university of technology, Tehran, Iran 0000-0002-0617-981X Mohammad Mehdi Ahmadi Civil Engineering Faculty, Sharif University of Technology, Tehran, Iran Journal Article 2022 08 24 Considering the environmental pollution resulting from the consumption of fossil fuels, replacing clean energy with fossil fuels has become one of the most critical issues in the world. In order to exchange the heat between superstructures and the ground, the use of energy piles can be considered as an approach to take advantage of clean energy. In order to maintain the safety and serviceability of structures built on energy piles, it is necessary to properly study the effects of heat exchange between energy piles and the ground on the mechanical response of energy piles and the influence of various parameters on the interaction between piles and the soil. In this paper, a 3D finite difference model was initially created using FLAC software for the thermo - mechanical analysis of energy piles, and it was validated by comparing the results of the present model with those of field tests and numerical models performed by other researchers. Using the present numerical model, the effects of changing the thermal expansion coefficient of the energy pile and clayey soil on axial stress, shaft friction, and axial displacement along the energy pile under cyclic thermal loading have been investigated. The results indicate that changing the thermal expansion coefficient of pile materials causes significant changes in the behavior of energy piles under heating and cooling conditions; however, changing the thermal expansion coefficient of the soil has little effect on the mechanical behavior of the energy pile during heating thermal loading. Considering the environmental pollution resulting from the consumption of fossil fuels, replacing clean energy with fossil fuels has become one of the most critical issues in the world. In order to exchange the heat between superstructures and the ground, the use of energy piles can be considered as an approach to take advantage of clean energy. In order to maintain the safety and serviceability of structures built on energy piles, it is necessary to properly study the effects of heat exchange between energy piles and the ground on the mechanical response of energy piles and the influence of various parameters on the interaction between piles and the soil. In this paper, a 3D finite difference model was initially created using FLAC software for the thermo - mechanical analysis of energy piles, and it was validated by comparing the results of the present model with those of field tests and numerical models performed by other researchers. Using the present numerical model, the effects of changing the thermal expansion coefficient of the energy pile and clayey soil on axial stress, shaft friction, and axial displacement along the energy pile under cyclic thermal loading have been investigated. The results indicate that changing the thermal expansion coefficient of pile materials causes significant changes in the behavior of energy piles under heating and cooling conditions; however, changing the thermal expansion coefficient of the soil has little effect on the mechanical behavior of the energy pile during heating thermal loading.

https://ceej.aut.ac.ir/article_5025_b6e584419a62da6229cf347e5ccfa166.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Damage detection of model reference adaptively-controlled structures using control force as a damage sensitive feature Damage detection of model reference adaptively-controlled structures using control force as a damage sensitive feature 301 318 5026 10.22060/ceej.2022.20786.7526 FA Hooman Shirzadi School of civil engineering, College of engineering, University of Tehran, Tehran, Iran Maryam Bitaraf University of Tehran, College of Engineering, School of Civil Engineering 0000-0002-7945-9388 Journal Article 2021 11 16 Civil infrastructures, nowadays, are an indispensable part of society, and any unpredicted damage can cause severe economic and life loss. Hence, developing smart structures has been the topic of many studies during the past decades. In this article, developing a smart structure by synthesizing structural control and health monitoring is suggested by extracting damage-sensitive features from the active control force. The autoregressive models have been deployed to extract damage-sensitive features in the time domain. Then, quadratic discriminant analysis is utilized to discriminant between different damage states of the structure. The active control force is obtained by two model reference adaptive controllers, namely the MIT rule and Lyapunov stability theorem, to attenuate the structural vibration caused by Gaussian white noise excitations. The proposed approach has been numerically studied on a three-story shear building with active ideal controllers in all floors. Results indicate that the proposed approach can detect the potential damage, as well as its severity and location, precisely. Civil infrastructures, nowadays, are an indispensable part of society, and any unpredicted damage can cause severe economic and life loss. Hence, developing smart structures has been the topic of many studies during the past decades. In this article, developing a smart structure by synthesizing structural control and health monitoring is suggested by extracting damage-sensitive features from the active control force. The autoregressive models have been deployed to extract damage-sensitive features in the time domain. Then, quadratic discriminant analysis is utilized to discriminant between different damage states of the structure. The active control force is obtained by two model reference adaptive controllers, namely the MIT rule and Lyapunov stability theorem, to attenuate the structural vibration caused by Gaussian white noise excitations. The proposed approach has been numerically studied on a three-story shear building with active ideal controllers in all floors. Results indicate that the proposed approach can detect the potential damage, as well as its severity and location, precisely.

https://ceej.aut.ac.ir/article_5026_f02208a057804ee16ac72ff4d3cec53b.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Semi-active control of structures with MR and Orifice dampers subjected to underground blast-induced vibration Semi-active control of structures with MR and Orifice dampers subjected to underground blast-induced vibration 319 336 5027 10.22060/ceej.2022.20819.7533 FA Amir Hossein Ghaffari civil engineering faculty, tabriz university, tabriz, iran Hosein Ghaffarzadeh Tabriz, Tabriz university, civil engineering faculty Journal Article 2021 11 26 Using the control tools is an efficient method to decrease the responses of the structure under external excitations. In this regard, this study investigates the performance of two structures equipped with MR dampers and Orifice dampers under blast-induced vibration. In addition to stimulating the underground blast-induced vibration (due to the different nature of these loads), seismic excitation has also been used to evaluate the efficiency of these dampers. These dampers are semi-active devices, which change the output force of the damper by changing the input voltage and magnetic field of dampers. Also, in this paper, clipped-optimal algorithm was used. This algorithm can generate optimal damper force by changing the voltage at each time step based on the input forces. In this research, structural responses based on optimal and maximum voltage are considered. Also, the numerical results of the structure are compared with LQR algorithm. The LQR algorithm is considered a criterion for reducing structural responses to blast-induced vibration. The results indicate that the proposed method (the different locations and types of dampers) is efficient for decreasing the responses of the structure. Using the control tools is an efficient method to decrease the responses of the structure under external excitations. In this regard, this study investigates the performance of two structures equipped with MR dampers and Orifice dampers under blast-induced vibration. In addition to stimulating the underground blast-induced vibration (due to the different nature of these loads), seismic excitation has also been used to evaluate the efficiency of these dampers. These dampers are semi-active devices, which change the output force of the damper by changing the input voltage and magnetic field of dampers. Also, in this paper, clipped-optimal algorithm was used. This algorithm can generate optimal damper force by changing the voltage at each time step based on the input forces. In this research, structural responses based on optimal and maximum voltage are considered. Also, the numerical results of the structure are compared with LQR algorithm. The LQR algorithm is considered a criterion for reducing structural responses to blast-induced vibration. The results indicate that the proposed method (the different locations and types of dampers) is efficient for decreasing the responses of the structure.

https://ceej.aut.ac.ir/article_5027_853c68de7253cdd55dc37be410a45c60.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Investigation of the behavior of Ahvaz sand soil stabilized with metakaolin Investigation of the behavior of Ahvaz sand soil stabilized with metakaolin 337 358 5028 10.22060/ceej.2022.21851.7838 FA Pouria Daneshgar Shahid Rajaee Teacher Training University/ Faculty of Civil Engineering Saeed Ghaffarpour Jahromi Department of Geotechnical Engineering and Water Engineering, Shahid Rajaee Teacher Training University 0000-0002-3033-7195 Hamed Arzani Civil Eng. Dep. Shahid Rajaee Teacher Training Univ. Lavizan. Tehran. Iran Journal Article 2022 10 13 Considering the growth of the population for the development of the country's infrastructure, stabilization and improvement of low-quality land in order to create a strong and resistant base are needed more than ever. So far, many improvement methods have been proposed in the world, which is one of the most common methods of chemical stabilization using lime or cement, which are not compatible with the environment. Therefore, nowadays, the use of pozzolans and geopolymeric cements instead of Portland cement has attracted the attention of various researchers. In this study, the stabilization of sandy soil in Ahvaz City with the help of metakaolin as an additive has been investigated. In this research, the effect of different amounts of variables such as the percentage of metakaolin, the ratio of sodium silicate to sodium hydroxide, the concentration of sodium hydroxide, and the ratio of alkaline activator solution to the additive at the curing ages of 7 and 28 days have been discussed. Samples are subjected to unconfined uniaxial compressive strength (UCS) evaluation and microstructural investigation, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses are used. The results of this research show that in order to achieve optimal resistance, it is necessary to mix 20% metakaolin, the ratio of sodium silicate to sodium hydroxide is 2.5, the concentration of sodium hydroxide is 12 Molar, and the ratio of activator solution to additive is 0.5. The strength of the sample with 28-day curing reaches about 5 MPa, which is about 3 times more than cement samples and 23 times more than unstabilized soil, which can be seen in the microstructural analysis of the presence of N-A-S-H gel as the main factor in increasing the strength in the geopolymerization process. Considering the growth of the population for the development of the country's infrastructure, stabilization and improvement of low-quality land in order to create a strong and resistant base are needed more than ever. So far, many improvement methods have been proposed in the world, which is one of the most common methods of chemical stabilization using lime or cement, which are not compatible with the environment. Therefore, nowadays, the use of pozzolans and geopolymeric cements instead of Portland cement has attracted the attention of various researchers. In this study, the stabilization of sandy soil in Ahvaz City with the help of metakaolin as an additive has been investigated. In this research, the effect of different amounts of variables such as the percentage of metakaolin, the ratio of sodium silicate to sodium hydroxide, the concentration of sodium hydroxide, and the ratio of alkaline activator solution to the additive at the curing ages of 7 and 28 days have been discussed. Samples are subjected to unconfined uniaxial compressive strength (UCS) evaluation and microstructural investigation, X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses are used. The results of this research show that in order to achieve optimal resistance, it is necessary to mix 20% metakaolin, the ratio of sodium silicate to sodium hydroxide is 2.5, the concentration of sodium hydroxide is 12 Molar, and the ratio of activator solution to additive is 0.5. The strength of the sample with 28-day curing reaches about 5 MPa, which is about 3 times more than cement samples and 23 times more than unstabilized soil, which can be seen in the microstructural analysis of the presence of N-A-S-H gel as the main factor in increasing the strength in the geopolymerization process.

https://ceej.aut.ac.ir/article_5028_bf8dd8c68d02e161c28dc9ea139d4784.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Role of personal barriers on willingness to walk in daily work trips across Rasht citizens Role of personal barriers on willingness to walk in daily work trips across Rasht citizens 359 388 5029 10.22060/ceej.2022.20832.7541 FA Zeinab Etemadi Naeini Amirkabir University of technology Meeghat Habibian Department of Civil and Environmental Engineering Geotechnics, Roads and Transportation Specialty Journal Article 2021 11 29 The walk-oriented pattern is an alternative travel pattern for daily trips; that a person walks more than her/his regular pattern. In order to examine the tendency to fulfill this pattern, it is necessary to examine the role of different types of barriers on pedestrian walking. This study intends to address the role of personal barriers which avoid people to walk more in their daily work trips. The studied barriers include laziness/tend to wake up late, physical/health problems, not interested in more walking, the importance of neat appearance at workplace and not feeling good about being seen on the streets. For this purpose, a sample of 432 employees living in the city of Rasht, Iran has been used. The studied variables are classified into three categories: socio-economic, travel and environmental characteristics. Five ordered logit models have been calibrated to investigate the importance of personal barriers including 11 variables of socio-economic characteristics, 6 variables of travel characteristics and 5 variables of environmental characteristics. The results show that while the effect of socio-economic characteristics on each of the personal barriers studied is different, the contribution of these characteristics on each of the five barriers: laziness/tend to wake up late, physical and health problems, not interested in more walking, the importance of neat appearance at work and not feeling good about being seen on streets are 41, 30, 13, 7 and 8 percent, respectively. Furthermore, the background variable of having at least 5 minutes daily walking in non-work trips of socio-economic characteristics, the total travel time variable of travel characteristics and the variable of walkability index of environmental characteristics are effective in tendency to walk more. The walk-oriented pattern is an alternative travel pattern for daily trips; that a person walks more than her/his regular pattern. In order to examine the tendency to fulfill this pattern, it is necessary to examine the role of different types of barriers on pedestrian walking. This study intends to address the role of personal barriers which avoid people to walk more in their daily work trips. The studied barriers include laziness/tend to wake up late, physical/health problems, not interested in more walking, the importance of neat appearance at workplace and not feeling good about being seen on the streets. For this purpose, a sample of 432 employees living in the city of Rasht, Iran has been used. The studied variables are classified into three categories: socio-economic, travel and environmental characteristics. Five ordered logit models have been calibrated to investigate the importance of personal barriers including 11 variables of socio-economic characteristics, 6 variables of travel characteristics and 5 variables of environmental characteristics. The results show that while the effect of socio-economic characteristics on each of the personal barriers studied is different, the contribution of these characteristics on each of the five barriers: laziness/tend to wake up late, physical and health problems, not interested in more walking, the importance of neat appearance at work and not feeling good about being seen on streets are 41, 30, 13, 7 and 8 percent, respectively. Furthermore, the background variable of having at least 5 minutes daily walking in non-work trips of socio-economic characteristics, the total travel time variable of travel characteristics and the variable of walkability index of environmental characteristics are effective in tendency to walk more.

https://ceej.aut.ac.ir/article_5029_ca172e964907a97d5ebd876bfdd4adbd.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Investigation of the corrosion initiation time of reinforced concrete structures at different distances from the Sea Investigation of the corrosion initiation time of reinforced concrete structures at different distances from the Sea 389 406 5030 10.22060/ceej.2022.20005.7312 FA Amirhossein Jafary Department of Civil engineering, Iran University of Science and Technology, Tehran, Iran Mohsen Ali Shayanfar Department of Structural Engineering, Iran University of Science and Technology, Tehran, Iran Mohammad Ghanooni-Bagha Department of Civil Engineering, East Tehran Branch, Islamic Azad University, Tehran, Iran Journal Article 2021 05 05 Corrosion is one of the crucial damages that may occur to reinforced concrete structures. It also may affect the expected performance of the structure during possible earthquakes. Onshore reinforced structures, bridges exposed to deicing salts in winter and also the pillars of marine structures under tidal waves, all of which are examples of corrosion damages. Corrosion mostly occurs due to two main reasons: chloride and carbonation which cause pitting corrosion and uniform corrosion, respectively. Corrosion starts with the reaching of those two ions to the bar surface, passing by the physical and chemical passive covers. Corrosion also affects the mechanical properties of the steel and the concrete and reduces the seismic performance of the structure. One of the most important parameters in studying corrosion and its effects on the seismic performance and life cycle of the structure is the corrosion initiation time. According to Fick’s law, the initiation time is a function of surface and critical chloride, chloride diffusion coefficient and concrete cover on armatures. In the present study, the chloride-based corrosion is considered. Besides, corrosion initiation time is determined by deterministic and probabilistic Monte-Carlo methods considering the uncertainties in the effective parameters. In the end, by comparing these two methods, the effect of uncertainties in the possibility of corrosion initiation time is presented. Furthermore, parameters like the distance from the sea and the water-to-cement ratio are discussed in a parametric study. Corrosion is one of the crucial damages that may occur to reinforced concrete structures. It also may affect the expected performance of the structure during possible earthquakes. Onshore reinforced structures, bridges exposed to deicing salts in winter and also the pillars of marine structures under tidal waves, all of which are examples of corrosion damages. Corrosion mostly occurs due to two main reasons: chloride and carbonation which cause pitting corrosion and uniform corrosion, respectively. Corrosion starts with the reaching of those two ions to the bar surface, passing by the physical and chemical passive covers. Corrosion also affects the mechanical properties of the steel and the concrete and reduces the seismic performance of the structure. One of the most important parameters in studying corrosion and its effects on the seismic performance and life cycle of the structure is the corrosion initiation time. According to Fick’s law, the initiation time is a function of surface and critical chloride, chloride diffusion coefficient and concrete cover on armatures. In the present study, the chloride-based corrosion is considered. Besides, corrosion initiation time is determined by deterministic and probabilistic Monte-Carlo methods considering the uncertainties in the effective parameters. In the end, by comparing these two methods, the effect of uncertainties in the possibility of corrosion initiation time is presented. Furthermore, parameters like the distance from the sea and the water-to-cement ratio are discussed in a parametric study.

https://ceej.aut.ac.ir/article_5030_faad95253aee7437871781018bdf3309.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Static examination of the interface behavior of the filter soil material-the asphaltic concrete core using direct shear apparatus- Case study: Mijran dam Static examination of the interface behavior of the filter soil material-the asphaltic concrete core using direct shear apparatus- Case study: Mijran dam 407 430 5031 10.22060/ceej.2022.20861.7548 FA Ashkan Gholipoor Noroozi Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran Rassoul Ajalloeian Department of Geology, University of Isfahan, Isfahan, Iran 0000-0001-9770-1695 Meysam Bayat Department of Civil Engineering, Najafabad Branch, Islamic Azad University, Najafabad, Iran 0000-0001-5525-5199 Journal Article 2021 12 07 Recently, the advantages of using asphalt concrete in the core compared to the clayey core have increased the application of core asphalt concrete in embankment dams. Due to the importance of the interfacial behavior of the asphaltic core and soil filter in the stability of these dams and the need for a more detailed investigation of the complex behavior of materials in the core-filter interface, in the present research, interfacial behavior of soil filter and asphalt core in the Mijran embankment dam (Mazandaran province) was investigated. For this purpose, a direct shear apparatus on a large scale is used. Soil materials, including clayey gravel (GC) and poorly graded gravel (GP), are according to the grain size distribution used in Mijran dam construction. In this research, the influence of factors such as compaction percentage of filter material and shear rate were investigated on shear strength and interlocking parameters (dilatancy angle and shear stiffness), as well as interaction ratio in the soil of filter and the core asphalt concrete interface. In this investigation, the ratio of the interfacial friction angle of soil material- asphalt concrete to the soil materials friction angle was defined as the interaction ratio. According to the findings, upon increasing the compaction level, the increasing amount in the interaction ratio in the interface GP material was higher compared to the GC material in the interface. On the other hand, the influence of the shear rate on the interaction ratio was similar in both the GC and GP materials in the interface. Recently, the advantages of using asphalt concrete in the core compared to the clayey core have increased the application of core asphalt concrete in embankment dams. Due to the importance of the interfacial behavior of the asphaltic core and soil filter in the stability of these dams and the need for a more detailed investigation of the complex behavior of materials in the core-filter interface, in the present research, interfacial behavior of soil filter and asphalt core in the Mijran embankment dam (Mazandaran province) was investigated. For this purpose, a direct shear apparatus on a large scale is used. Soil materials, including clayey gravel (GC) and poorly graded gravel (GP), are according to the grain size distribution used in Mijran dam construction. In this research, the influence of factors such as compaction percentage of filter material and shear rate were investigated on shear strength and interlocking parameters (dilatancy angle and shear stiffness), as well as interaction ratio in the soil of filter and the core asphalt concrete interface. In this investigation, the ratio of the interfacial friction angle of soil material- asphalt concrete to the soil materials friction angle was defined as the interaction ratio. According to the findings, upon increasing the compaction level, the increasing amount in the interaction ratio in the interface GP material was higher compared to the GC material in the interface. On the other hand, the influence of the shear rate on the interaction ratio was similar in both the GC and GP materials in the interface.

https://ceej.aut.ac.ir/article_5031_e327b1649d06bf74fceb4fe73f83bdba.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Simulation of delay factors in dam construction projects with a system dynamics approach Simulation of delay factors in dam construction projects with a system dynamics approach 431 454 5033 10.22060/ceej.2022.21250.7666 FA Sina Fard Moradinia Assistant professor, Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran 0000-0003-3539-7311 Iraj Alimi Ph.D. Candidate of Engineering and Construction Management, Department of Civil Engineering, Tabriz Branch, Islamic Azad University, Tabriz, Iran, Journal Article 2022 03 28 Delays are among the causes for financial loss in construction projects. Extensive research has thus been carried out on how to confront it, or reduce its consequences. The effect on dam construction projects is highly pronounced as a consequence of their high operation magnitude, and long initial execution duration. Numerous papers have thus far studied the causes of delay in projects from a dynamic systems’ approach, in such sectors as construction, railways and highways. However, a simple comprehensive exploration of literature on the study of construction delay through the dynamic systems method reveals a gap of research around dam construction. As this is the largest class of projects in the nation, numerous factors are involved in project delays. To investigate the causes of delay in these projects the Vensim software package has proven useful and imperative in carrying out dynamic system analyses. The present paper, involves a case study of the Marvak dam in Lorestan province. Based on previous studies and former practical experience in construction, a set of 10 common causes of delay was compiled into a questionnaire, for 20 dam construction experts who were asked to rate the causes from 1 to 10, depending on how much each factor actually causes delay in the project, with a rating of 1 and 10, signifying the highest, and lowest weight. Among the factors, the effect of four variables, namely human resources, machinery and equipment, financial resources of the contractor, and deficiency in technical blueprints, were selected as the most effective factors. The Vensim software package was then used to simulate the model based on project specifications. Results involved the project’s “overall predictable delay” with the share of each factor specified in a breakdown. Delays are among the causes for financial loss in construction projects. Extensive research has thus been carried out on how to confront it, or reduce its consequences. The effect on dam construction projects is highly pronounced as a consequence of their high operation magnitude, and long initial execution duration. Numerous papers have thus far studied the causes of delay in projects from a dynamic systems’ approach, in such sectors as construction, railways and highways. However, a simple comprehensive exploration of literature on the study of construction delay through the dynamic systems method reveals a gap of research around dam construction. As this is the largest class of projects in the nation, numerous factors are involved in project delays. To investigate the causes of delay in these projects the Vensim software package has proven useful and imperative in carrying out dynamic system analyses. The present paper, involves a case study of the Marvak dam in Lorestan province. Based on previous studies and former practical experience in construction, a set of 10 common causes of delay was compiled into a questionnaire, for 20 dam construction experts who were asked to rate the causes from 1 to 10, depending on how much each factor actually causes delay in the project, with a rating of 1 and 10, signifying the highest, and lowest weight. Among the factors, the effect of four variables, namely human resources, machinery and equipment, financial resources of the contractor, and deficiency in technical blueprints, were selected as the most effective factors. The Vensim software package was then used to simulate the model based on project specifications. Results involved the project’s “overall predictable delay” with the share of each factor specified in a breakdown.

https://ceej.aut.ac.ir/article_5033_91c77393975889bd08f301c9e13a44b7.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Effect of Soft Lens on the Behavior of Ordinary and Reinforced Stone Columns Located in Saturated Sandy Bed Effect of Soft Lens on the Behavior of Ordinary and Reinforced Stone Columns Located in Saturated Sandy Bed 455 470 5036 10.22060/ceej.2023.21390.7711 FA NIYOUSHA Bazazzadegan Department of Geotechnics, Faculty of Civil Engineering, Islamic Azad University, Science and Research Branch Navid Ganjian Assistant Professor of Science and Research branch of Azad University Javad Nazariafshar Assistant Professor, Department of Civil Engineering, Shahr-e-Qods Branch Islamic Azad University, Tehran, Iran 0000-0001-8807-1417 Journal Article 2022 05 20 One of the effective methods to improve the behavior of problematic beds containing soft lens is using stone columns. The capability of this soil improvement method increases by simultaneous use of the stone column and geosynthetic encasement, especially in the presence of soft lens near the ground surface or where the possibility of bulging failure is probable. In this research, the efficiency of using stone column embedded in a saturated sandy bed containing soft lens has been numerically investigated in terms of bearing capacity and failure mode. Also, the efficiency of reinforcing the stone column has been investigated in the presence of soft lens with different thicknesses and placement level. The results of numerical analysis obtained by finite element software (Abaqus) and validated by laboratory results of small-scale physical model experiments in real stress conditions shows that in the presence of soft lens, the change in the length of a stone column does not affect the occurrence of bulging failure and decreasing placement level of the soft lens, increases the bulging failure occurrence proportional. On the other hand, increasing the thickness of the soft lens reduces the bearing capacity of the ordinary and reinforced stone column. The phenomenon of bulging can occur at the level of the lens placement and up to a depth of about 4 times the diameter of the ordinary column because of the existence of a soft lens in a relatively loose sandy bed, while the mechanism of failure is not bulging anymore if using encasement. One of the effective methods to improve the behavior of problematic beds containing soft lens is using stone columns. The capability of this soil improvement method increases by simultaneous use of the stone column and geosynthetic encasement, especially in the presence of soft lens near the ground surface or where the possibility of bulging failure is probable. In this research, the efficiency of using stone column embedded in a saturated sandy bed containing soft lens has been numerically investigated in terms of bearing capacity and failure mode. Also, the efficiency of reinforcing the stone column has been investigated in the presence of soft lens with different thicknesses and placement level. The results of numerical analysis obtained by finite element software (Abaqus) and validated by laboratory results of small-scale physical model experiments in real stress conditions shows that in the presence of soft lens, the change in the length of a stone column does not affect the occurrence of bulging failure and decreasing placement level of the soft lens, increases the bulging failure occurrence proportional. On the other hand, increasing the thickness of the soft lens reduces the bearing capacity of the ordinary and reinforced stone column. The phenomenon of bulging can occur at the level of the lens placement and up to a depth of about 4 times the diameter of the ordinary column because of the existence of a soft lens in a relatively loose sandy bed, while the mechanism of failure is not bulging anymore if using encasement.

https://ceej.aut.ac.ir/article_5036_c731077c04035ac9e92a3706288db18f.pdf

Amirkabir University of Technology Amirkabir Journal of Civil Engineering 2588-297X 55 2 2023 04 21 Evaluation of the compressive strength and permeability of graphene oxide-reinforced concrete by using the results of the cylindrical chamber method Evaluation of the compressive strength and permeability of graphene oxide-reinforced concrete by using the results of the cylindrical chamber method 471 490 5053 10.22060/ceej.2023.18722.6941 FA Mahna Safarkhani Imam Khomeini International University Mahmood Naderi Department of civil engineering, Faculty of engineering, International Imam Khomeini university, Qazvin, Iran Journal Article 2020 07 13 Water permeability in cement materials is influenced by internal factors, including the type of porous network of cement materials, and external factors, including applied pressure. In this study, the effect of graphene oxide on the compressive strength and anisotropy of the concrete samples and also the effect of applying hydrostatic pressure on the permeability of concrete reinforced with graphene oxide (GO) have been investigated. One of the important reasons for not using graphene in cement composites is its hydrophobicity, which causes the inappropriate distribution of graphene in the structure. The hydrophobic properties of graphene can be converted into hydrophilic properties through the process of chemical functionalization or physical coating. The results of the compressive strength of concrete indicate that the use of these particles in the concrete mixture can increase the compressive strength and reduce the anisotropy in the strength compared to the control sample. This issue can be considered due to the random orientation of graphene oxide sheets in the volume of concrete. The results also show that the addition of a small amount of graphene oxide can reduce the permeability of concrete. In fact, by adding these nanoparticles, it is possible to improve the characteristics of water transfer in concrete and subsequently the durability of it. Water permeability in cement materials is influenced by internal factors, including the type of porous network of cement materials, and external factors, including applied pressure. In this study, the effect of graphene oxide on the compressive strength and anisotropy of the concrete samples and also the effect of applying hydrostatic pressure on the permeability of concrete reinforced with graphene oxide (GO) have been investigated. One of the important reasons for not using graphene in cement composites is its hydrophobicity, which causes the inappropriate distribution of graphene in the structure. The hydrophobic properties of graphene can be converted into hydrophilic properties through the process of chemical functionalization or physical coating. The results of the compressive strength of concrete indicate that the use of these particles in the concrete mixture can increase the compressive strength and reduce the anisotropy in the strength compared to the control sample. This issue can be considered due to the random orientation of graphene oxide sheets in the volume of concrete. The results also show that the addition of a small amount of graphene oxide can reduce the permeability of concrete. In fact, by adding these nanoparticles, it is possible to improve the characteristics of water transfer in concrete and subsequently the durability of it.

https://ceej.aut.ac.ir/article_5053_4aeae10ea1c6433c926cdfa558d31134.pdf