Mohamed A. Sakr, Ayman A. Seleemah, Omnia F. Kharoob, Mostafa Aboelnour
A finite element model (FEM) was created with the aim of analyzing the behavior of steel fiber reinforced recycled concrete (SFRRC)-filled steel tube columns under combined cyclic loading and monotonic axial load. The FEM considered the effect of steel tube confinement on the inner concrete behavior under cyclic loading. The numerical model was described in detail, with a focus on modeling the materials involved (normal concrete, SFRRC, and steel) under cyclic loading. A constitutive concrete model - with and without considering confinement - was based on utilizing a concrete damaged plasticity (CDP) model. The steel tube - concrete core interface was modeled by a surface-to-surface contact. A stress-strain constitutive concrete model, confined by circular steel tubes, was implemented, and validated using experimental results from the literature. The developed FEM considered various parameters: steel tube thickness, volume ratios of steel fibers, besides strengths of both concrete core and the steel tube. The FEM results showed great similarity to the under- cyclic- loading tested columns. The results indicated that the concrete confining pressure must be considered in CDP model. A good correlation between numerical and experimental findings was obvious, including failure modes, and hysteretic curves of load-displacement.
{"title":"Numerical Modeling of Steel Fiber Reinforced Recycled Concrete Filled Steel Tube Column Under Cyclic Loading","authors":"Mohamed A. Sakr, Ayman A. Seleemah, Omnia F. Kharoob, Mostafa Aboelnour","doi":"10.56748/ejse.24548","DOIUrl":"https://doi.org/10.56748/ejse.24548","url":null,"abstract":"A finite element model (FEM) was created with the aim of analyzing the behavior of steel fiber reinforced recycled concrete (SFRRC)-filled steel tube columns under combined cyclic loading and monotonic axial load. The FEM considered the effect of steel tube confinement on the inner concrete behavior under cyclic loading. The numerical model was described in detail, with a focus on modeling the materials involved (normal concrete, SFRRC, and steel) under cyclic loading. A constitutive concrete model - with and without considering confinement - was based on utilizing a concrete damaged plasticity (CDP) model. The steel tube - concrete core interface was modeled by a surface-to-surface contact. A stress-strain constitutive concrete model, confined by circular steel tubes, was implemented, and validated using experimental results from the literature. The developed FEM considered various parameters: steel tube thickness, volume ratios of steel fibers, besides strengths of both concrete core and the steel tube. The FEM results showed great similarity to the under- cyclic- loading tested columns. The results indicated that the concrete confining pressure must be considered in CDP model. A good correlation between numerical and experimental findings was obvious, including failure modes, and hysteretic curves of load-displacement.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"59 3","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141805519","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
To study the influence of bond-slip on the numerical simulation of steel reinforced lightweight concrete(SRLC) members, the push-out test and finite element analysis are carried out first, and then the nonlinear finite element simulation of SRLC beams is conducted. The calculated results are compared with the experimental results. Four factors as the concrete protective cover thickness, stirrup ratio, concrete strength and anchorage length of section steel are considered in test. The constitutive relation of interface bonding slip between the section steel and light concrete is introduced in the finite element analysis based on the test results. Finite element analysis of push-out specimens results indicate that the normal stress of the section steel is the same on the same cross section and the stress gradient gradually decreases from the loading end to the free end. Specimens with equivalent restraint coefficient γe less than 0.01 will be subjected to split failure and those specimens with the coefficient γe greater than or equal to 0.01 will be subjected to push-off failure. The bearing capacity and slip value obtained by finite element computation is consistent with experiment results. The stress distribution, crack shape and load-deflection curve are analyzed in numerical simulation of SRLC beams. Influence factors involving shear span ratio and position of section steel are considered．Analysis results show that the mechanical properties of the SRLC beams are similar with that of the steel reinforced normal concrete (SRNC)beams. Diagonal shear failure are gradually transformed into flexural failure with the shear span ratio increasing. Load- deflection curve is obviously divided into three stages. Finite analysis results considering the slip between section steel and concrete agree well with the test results, while the capacity and stiffness without considering the slip are bigger than the experimental values.
{"title":"Numerical Simulation of Steel Reinforced Lightweight Aggregate Concrete Beams Based on Analysis of Push-out Test","authors":"Jianwen Zhang, Fanyu Zhao, Zhipeng Xv","doi":"10.56748/ejse.24549","DOIUrl":"https://doi.org/10.56748/ejse.24549","url":null,"abstract":"To study the influence of bond-slip on the numerical simulation of steel reinforced lightweight concrete(SRLC) members, the push-out test and finite element analysis are carried out first, and then the nonlinear finite element simulation of SRLC beams is conducted. The calculated results are compared with the experimental results. Four factors as the concrete protective cover thickness, stirrup ratio, concrete strength and anchorage length of section steel are considered in test. The constitutive relation of interface bonding slip between the section steel and light concrete is introduced in the finite element analysis based on the test results. Finite element analysis of push-out specimens results indicate that the normal stress of the section steel is the same on the same cross section and the stress gradient gradually decreases from the loading end to the free end. Specimens with equivalent restraint coefficient γe less than 0.01 will be subjected to split failure and those specimens with the coefficient γe greater than or equal to 0.01 will be subjected to push-off failure. The bearing capacity and slip value obtained by finite element computation is consistent with experiment results. The stress distribution, crack shape and load-deflection curve are analyzed in numerical simulation of SRLC beams. Influence factors involving shear span ratio and position of section steel are considered．Analysis results show that the mechanical properties of the SRLC beams are similar with that of the steel reinforced normal concrete (SRNC)beams. Diagonal shear failure are gradually transformed into flexural failure with the shear span ratio increasing. Load- deflection curve is obviously divided into three stages. Finite analysis results considering the slip between section steel and concrete agree well with the test results, while the capacity and stiffness without considering the slip are bigger than the experimental values.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"67 12","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141346418","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Unbonded pre-tensioned systems, in which tendons are greased and wrapped in plastic sheathing, have several benefits in comparison to bonded systems. However, analytical evaluation of their capacity is taxing due to the iterative compatibility conditions necessary to determine the system’s behavior using the empirical equations available in the literature. To investigate the behaviour and strength of unbonded pre-tensioned RC slabs subject to flexural loads, four simply-supported post-tensioned slabs with unbonded tendons were tested in flexure. Experimental failure loads and tendon strains were compared to the ACI 318-19 provisions. While the provisions for unbonded specimens were found to be accurate, the strain in the unbonded tendons exceeded the yield stress in all specimens, suggesting that ACI 318-19’s stress limitations on unbonded post-tensioned concrete are unwarranted. The unbonded system also showed better crack control at the failure stage when non-prestressing steel reinforcement is used when compared to system with no non-prestressing steel.
{"title":"Investigating the Behaviour and Strength of Unbonded Pre-tensioned RC Slabs Subject to Flexural Loads","authors":"Ja Abdelhalim, George Iskander, E. Y. Sayed Ahmed","doi":"10.56748/ejse.24483","DOIUrl":"https://doi.org/10.56748/ejse.24483","url":null,"abstract":"Unbonded pre-tensioned systems, in which tendons are greased and wrapped in plastic sheathing, have several benefits in comparison to bonded systems. However, analytical evaluation of their capacity is taxing due to the iterative compatibility conditions necessary to determine the system’s behavior using the empirical equations available in the literature. To investigate the behaviour and strength of unbonded pre-tensioned RC slabs subject to flexural loads, four simply-supported post-tensioned slabs with unbonded tendons were tested in flexure. Experimental failure loads and tendon strains were compared to the ACI 318-19 provisions. While the provisions for unbonded specimens were found to be accurate, the strain in the unbonded tendons exceeded the yield stress in all specimens, suggesting that ACI 318-19’s stress limitations on unbonded post-tensioned concrete are unwarranted. The unbonded system also showed better crack control at the failure stage when non-prestressing steel reinforcement is used when compared to system with no non-prestressing steel.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"3 10","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141387961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Junling Qiu, Guanfei Yang, Xiaolong Huang, Hu Luo, Gang Si, Haoran Hu, Yuhua Chen
To provide reference and guidance for ensuring the safe construction of tunnel construction, taking a mountain road tunnel project as the background, the finite element numerical simulation method is used to study the excavation of large longitudinal slope tunnel by TBM method. The vertical displacement of surrounding rock shows the deformation trend of vault subsidence and arch bottom uplift, and the peak value of lateral displacement decreases gradually with the increase of longitudinal slope gradient. The segment at the vault and arch bottom of the tunnel are subjected to positive bending moment, and the spandrel arch waist and arch foot are subjected to negative bending moment. The maximum value of the absolute value of the axial force is located at the arch waist. In addition, the deformation characteristics of the surrounding rock and the stress characteristics of the segment during the tunnel crossing the fault fracture zone are analyzed. The research shows that the vertical displacement of the surrounding rock is significantly larger than that of the intact stratum, and the closer to the fault fracture zone, the larger the vertical deformation is, and the closer to the tunnel entrance section, the larger the uplift deformation is. The horizontal displacement of the surrounding rock is obviously smaller before it enters the fault fracture zone, and the displacement increases rapidly when it is constructed to the fault range and reaches the peak at the center of the fault. After crossing the fault, the displacement changes little.
{"title":"Response characteristics of surrounding rock and segment structure of large longitudinal slope tunnel","authors":"Junling Qiu, Guanfei Yang, Xiaolong Huang, Hu Luo, Gang Si, Haoran Hu, Yuhua Chen","doi":"10.56748/ejse.24552","DOIUrl":"https://doi.org/10.56748/ejse.24552","url":null,"abstract":"To provide reference and guidance for ensuring the safe construction of tunnel construction, taking a mountain road tunnel project as the background, the finite element numerical simulation method is used to study the excavation of large longitudinal slope tunnel by TBM method. The vertical displacement of surrounding rock shows the deformation trend of vault subsidence and arch bottom uplift, and the peak value of lateral displacement decreases gradually with the increase of longitudinal slope gradient. The segment at the vault and arch bottom of the tunnel are subjected to positive bending moment, and the spandrel arch waist and arch foot are subjected to negative bending moment. The maximum value of the absolute value of the axial force is located at the arch waist. In addition, the deformation characteristics of the surrounding rock and the stress characteristics of the segment during the tunnel crossing the fault fracture zone are analyzed. The research shows that the vertical displacement of the surrounding rock is significantly larger than that of the intact stratum, and the closer to the fault fracture zone, the larger the vertical deformation is, and the closer to the tunnel entrance section, the larger the uplift deformation is. The horizontal displacement of the surrounding rock is obviously smaller before it enters the fault fracture zone, and the displacement increases rapidly when it is constructed to the fault range and reaches the peak at the center of the fault. After crossing the fault, the displacement changes little.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"56 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140077852","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Seyed Saleh Sadeghi, Ali Abdi Kordani, Mohammad Zarei
Weather conditions such as rainfall and freeze-thaw cycles affect the pavement performance of airports; therefore, methods such as using de-icing chemicals are considered in order to maintain the normal condition of the airport runway. In addition to the above factors, de-icing chemicals play an important role in pavement performance and the damage caused to it due to their chemical nature. Therefore, investigating the effect of de-icing chemicals and determining the appropriate material to maintain the airport's pavement is a priority for engineers. In this study, the effect of three de-icing chemicals, sodium chloride, potassium acetate, and ethylene glycol (at concentrations of 23.3%, 49%, and 69.07%, respectively) on skid resistance (The British Pendulum Test (BPT) and The Road Test Machine (RTM)) and the mechanical properties (Compressive Strength Test) of the concrete under Freezing and Thawing Cycle were investigated. The BPT test results showed that sodium chloride resulted in better skid resistance than other chemicals when the number of cycles is more than 100 cycles. This result was also obtained for all cycles in the RTM test. Also, ethylene glycol was not suitable for improving skid resistance based on BPT and RTM tests. Furthermore, the results of the compressive strength of concrete mixtures showed that the de-icing chemicals reduced the compressive strength of concrete mixtures. Based on all the results, sodium chloride had better results than other chemicals.
{"title":"Evaluation of the Effect of De-icing Chemicals on Performance of Airport Concrete Pavement under Freeze-Thaw Cycles","authors":"Seyed Saleh Sadeghi, Ali Abdi Kordani, Mohammad Zarei","doi":"10.56748/ejse.24492","DOIUrl":"https://doi.org/10.56748/ejse.24492","url":null,"abstract":"Weather conditions such as rainfall and freeze-thaw cycles affect the pavement performance of airports; therefore, methods such as using de-icing chemicals are considered in order to maintain the normal condition of the airport runway. In addition to the above factors, de-icing chemicals play an important role in pavement performance and the damage caused to it due to their chemical nature. Therefore, investigating the effect of de-icing chemicals and determining the appropriate material to maintain the airport's pavement is a priority for engineers. In this study, the effect of three de-icing chemicals, sodium chloride, potassium acetate, and ethylene glycol (at concentrations of 23.3%, 49%, and 69.07%, respectively) on skid resistance (The British Pendulum Test (BPT) and The Road Test Machine (RTM)) and the mechanical properties (Compressive Strength Test) of the concrete under Freezing and Thawing Cycle were investigated. The BPT test results showed that sodium chloride resulted in better skid resistance than other chemicals when the number of cycles is more than 100 cycles. This result was also obtained for all cycles in the RTM test. Also, ethylene glycol was not suitable for improving skid resistance based on BPT and RTM tests. Furthermore, the results of the compressive strength of concrete mixtures showed that the de-icing chemicals reduced the compressive strength of concrete mixtures. Based on all the results, sodium chloride had better results than other chemicals.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"15 9","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140077737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xingzhong Nong, Xingkai Pei, Shuai Zhang, Gongning Liu
Based on the Tianhe East Station in Guangzhou Metro Line 11 engineering, this paper analyzes the formation mechanism of soil arching effect (SAE) of station by pile-beam-arch (PBA) method in the excavation process and studies the mechanics and deformation laws of side piles in different construction stages under different pile spacing conditions. The results show that the formation, development and destruction of SAE between piles are closely related to construction process. Both too large and too small pile spacings are not conducive to the development about SAE between piles; when it is located between them, the SAE between piles exerts greatly. In the form of composite lining system, supporting piles as well as SAE between piles play an effective role in supporting soil behind piles. The lateral deformation of pile body is most significant in the completion of buckle arch to the excavation of first soil layer, which is the critical construction phase to reduce lateral deformation of side pile. The axial forces of side pile increase gradually with the excavation of station, and the change is the most drastic at the excavation for first soil layer. The influence of pile spacing on vertical settlement and axial force of side piles is much greater than that of horizontal displacement and bending moment.
{"title":"Study on the dynamic construction mechanics of side piles in metro station using the pile-beam-arch method","authors":"Xingzhong Nong, Xingkai Pei, Shuai Zhang, Gongning Liu","doi":"10.56748/ejse.24532","DOIUrl":"https://doi.org/10.56748/ejse.24532","url":null,"abstract":"Based on the Tianhe East Station in Guangzhou Metro Line 11 engineering, this paper analyzes the formation mechanism of soil arching effect (SAE) of station by pile-beam-arch (PBA) method in the excavation process and studies the mechanics and deformation laws of side piles in different construction stages under different pile spacing conditions. The results show that the formation, development and destruction of SAE between piles are closely related to construction process. Both too large and too small pile spacings are not conducive to the development about SAE between piles; when it is located between them, the SAE between piles exerts greatly. In the form of composite lining system, supporting piles as well as SAE between piles play an effective role in supporting soil behind piles. The lateral deformation of pile body is most significant in the completion of buckle arch to the excavation of first soil layer, which is the critical construction phase to reduce lateral deformation of side pile. The axial forces of side pile increase gradually with the excavation of station, and the change is the most drastic at the excavation for first soil layer. The influence of pile spacing on vertical settlement and axial force of side piles is much greater than that of horizontal displacement and bending moment.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":" 38","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139627856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
There is a scarcity of research regarding the efficacy of Fiber Reinforced Polymer (FRP) confinement on low strength materials. This paper presents the findings of an experimental study that focuses on the behavior of concentrically loaded short concrete columns with low concrete strength, which are confined using CFRP wraps. A set of nine (9) square concrete columns of short length were subjected to testing. The experimental setup consisted of a single unconfined column, referred to as the control column, and eight additional columns that were confined utilizing externally bonded CFRP wraps. These confining schemes were determined based on the findings of a previous study conducted by the authors, which focused on short square columns with smaller cross sections. The study focused on examining the impact of various confinement schemes on the load carrying capacities of columns through the application of concentric uniaxial compression. The implementation of various confinement schemes led to an increase in the load carrying capacities of confined concrete columns, demonstrating the effectiveness of externally bonded CFRP wraps in enhancing the performance of short rectangular concentrically loaded concrete columns. The primary objective of this investigation is to examine the behavior of concrete columns with reinforcement that have been reinforced using carbon fiber composites. The findings demonstrated the efficacy of carbon fibers in the restoration of impaired columns, as evidenced by a notable enhancement in the load-bearing capacity of the columns, ranging from 35% to 90%.
{"title":"Study The Behavior of Square Reinforced Concrete Columns Strengthened with CFRP","authors":"Zainab Al-khafaji","doi":"10.56748/ejse.23487","DOIUrl":"https://doi.org/10.56748/ejse.23487","url":null,"abstract":"There is a scarcity of research regarding the efficacy of Fiber Reinforced Polymer (FRP) confinement on low strength materials. This paper presents the findings of an experimental study that focuses on the behavior of concentrically loaded short concrete columns with low concrete strength, which are confined using CFRP wraps. A set of nine (9) square concrete columns of short length were subjected to testing. The experimental setup consisted of a single unconfined column, referred to as the control column, and eight additional columns that were confined utilizing externally bonded CFRP wraps. These confining schemes were determined based on the findings of a previous study conducted by the authors, which focused on short square columns with smaller cross sections. The study focused on examining the impact of various confinement schemes on the load carrying capacities of columns through the application of concentric uniaxial compression. The implementation of various confinement schemes led to an increase in the load carrying capacities of confined concrete columns, demonstrating the effectiveness of externally bonded CFRP wraps in enhancing the performance of short rectangular concentrically loaded concrete columns. The primary objective of this investigation is to examine the behavior of concrete columns with reinforcement that have been reinforced using carbon fiber composites. The findings demonstrated the efficacy of carbon fibers in the restoration of impaired columns, as evidenced by a notable enhancement in the load-bearing capacity of the columns, ranging from 35% to 90%.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"15 16","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139129984","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The field of structural engineering has in recent times begun to widen its scope from the traditional analysis and design, into the development of new structural materials. This is because the use of non-renewable materials in forming and framing structural projects are raising serious environmental concerns bothering on sustainability of materials, especially cement, to produce structural concrete. Cement has been found to be a major contributor to greenhouse gases which affect the environment negatively. Waste from both the industrial and agricultural industries are gradually becoming sources of material to partly replace cement in concrete because of their pozzolanic properties. The agro-based pozzolanic materials include Rice husk Ash (RHA), Saw dust ash (SDA), Palm oil fuel ash (POFA) amongst others. To further widen the scope and resource base of pozzolanic materials for concreting, ternary blends consisting of agro-based pozzolans are being researched into. These research efforts however appear to be uncoordinated, and thus there is a need to juxtapose these efforts together to see the extent of work done on such ternary blends and present their relevant structural properties. This is with a view to helping identify gaps in such research as a means of preventing wastage of research energies. This paper presents a review of structural properties of some agro-based ternary blends used in structural concrete. It is concluded that more research effort is needed, especially in the development of practical and acceptable guidelines that will aid their application in concrete, for sustainable production of structural concrete.
{"title":"A Review of Structures and Performance of Ternary Blends of Rice Husk Ash and Some Wastes in Concrete","authors":"C. Fapohunda, O. E. Osanyinlokun, A. O. Abioye","doi":"10.56748/ejse.23473","DOIUrl":"https://doi.org/10.56748/ejse.23473","url":null,"abstract":"The field of structural engineering has in recent times begun to widen its scope from the traditional analysis and design, into the development of new structural materials. This is because the use of non-renewable materials in forming and framing structural projects are raising serious environmental concerns bothering on sustainability of materials, especially cement, to produce structural concrete. Cement has been found to be a major contributor to greenhouse gases which affect the environment negatively. Waste from both the industrial and agricultural industries are gradually becoming sources of material to partly replace cement in concrete because of their pozzolanic properties. The agro-based pozzolanic materials include Rice husk Ash (RHA), Saw dust ash (SDA), Palm oil fuel ash (POFA) amongst others. To further widen the scope and resource base of pozzolanic materials for concreting, ternary blends consisting of agro-based pozzolans are being researched into. These research efforts however appear to be uncoordinated, and thus there is a need to juxtapose these efforts together to see the extent of work done on such ternary blends and present their relevant structural properties. This is with a view to helping identify gaps in such research as a means of preventing wastage of research energies. This paper presents a review of structural properties of some agro-based ternary blends used in structural concrete. It is concluded that more research effort is needed, especially in the development of practical and acceptable guidelines that will aid their application in concrete, for sustainable production of structural concrete.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":"4 5","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139135540","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ming Zhang, Tie Wang, Xiaochuan Wang, Wentao Wu, Jiaqi Guo
To mitigate freeze-thaw damage in tunnels located in high-altitude cold regions, insulation layers are implemented to prevent the freezing of surrounding rocks. Currently, the selection of laying methods lacks a solid scientific basis, with the merits and demerits of various techniques remaining insufficiently evaluated. This study seeks to establish a scientifically grounded equilibrium between the anti-freezing efficacy and the construction impact of tunnel insulation in cold regions through the optimization of insulation design via numerical calculations. First, the advantages and disadvantages of the four insulation layer laying methods were summarized. Then, a multilayer media heat transfer model that accounts for the latent heat of phase change was developed, grounded in solid heat transfer and porous media heat transfer theories, and corroborated by typical case studies. Finally, taking Duolong tunnel as a case study, the insulation effect of various laying methods at different positions of the tunnel was analyzed based on the finite element method. The results show that the unfavorable position of the four laying methods is at the inverted arch of the tunnel, and the unfavorable time point occurs when the temperature rises from below 0℃ to above 0℃. Among the four laying methods, off-wall laying exhibits the superior insulation performance at tunnel vault, while sandwich laying has best insulation effect at the arch foot and inverted arch. The research results can provide reference and basis for the thermal insulation and anti-freezing design of tunnels in high-altitude cold regions.
{"title":"Analysis on the laying method and thermal insulation effect of tunnel insulation layer in high-altitude cold regions","authors":"Ming Zhang, Tie Wang, Xiaochuan Wang, Wentao Wu, Jiaqi Guo","doi":"10.56748/ejse.23376","DOIUrl":"https://doi.org/10.56748/ejse.23376","url":null,"abstract":"To mitigate freeze-thaw damage in tunnels located in high-altitude cold regions, insulation layers are implemented to prevent the freezing of surrounding rocks. Currently, the selection of laying methods lacks a solid scientific basis, with the merits and demerits of various techniques remaining insufficiently evaluated. This study seeks to establish a scientifically grounded equilibrium between the anti-freezing efficacy and the construction impact of tunnel insulation in cold regions through the optimization of insulation design via numerical calculations. First, the advantages and disadvantages of the four insulation layer laying methods were summarized. Then, a multilayer media heat transfer model that accounts for the latent heat of phase change was developed, grounded in solid heat transfer and porous media heat transfer theories, and corroborated by typical case studies. Finally, taking Duolong tunnel as a case study, the insulation effect of various laying methods at different positions of the tunnel was analyzed based on the finite element method. The results show that the unfavorable position of the four laying methods is at the inverted arch of the tunnel, and the unfavorable time point occurs when the temperature rises from below 0℃ to above 0℃. Among the four laying methods, off-wall laying exhibits the superior insulation performance at tunnel vault, while sandwich laying has best insulation effect at the arch foot and inverted arch. The research results can provide reference and basis for the thermal insulation and anti-freezing design of tunnels in high-altitude cold regions.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":" 464","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139137075","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Water inrush disaster of karst tunnel often lead to significant economic losses and serious casualties, which is an urgent engineering roadblock to be solved in the construction of tunnel in karst area. In this paper, three-dimensional discrete element method considering fluid-solid coupling effect and structural characteristics of water-mud resistant rock mass is adopted to systematically study the evolution law of displacement field and seepage field of intermittent joint type water-mud resistant rock mass of tunnel face and its water inrush critical characteristics during the process of sequential excavation of karst tunnel close to the frontal high-pressure water-rich karst cavity. The results show that: With the tunnel face gradually approaching the front-concealed high-pressure water-rich karst cavity, the stability of water-mud resistant rock mass is increasingly affected by high-pressure karst water, and karst water pressure gradually becomes the main control factor. The closer the tunnel face is to the front-concealed high-pressure water-rich karst cavity, the greater the extrusion displacement of karst tunnel face and its increase amplitude, the higher damage degree of water-mud resistant rock mass of face. With the advance of tunnel excavation, the intermittent cracks in the water-mud resistant rock mass of face gradually connect and form a stable hydraulic connection. The flow velocity and seepage pressure of karst water rise significantly at the moment of overall instability of face and the formation of water inrush channel, showing obvious precursor characteristics. The research achievements provide a reference for early warning and prevention and control of water inrush disaster of karst tunnel face.
{"title":"DEM-based analysis of water inrush process of underground engineering face with intermittent joints in karst region","authors":"Shuguo Zhang, Ling Dai, Xiaohu Yuan, Qirui Wang, Jingmao Xu","doi":"10.56748/ejse.23480","DOIUrl":"https://doi.org/10.56748/ejse.23480","url":null,"abstract":"Water inrush disaster of karst tunnel often lead to significant economic losses and serious casualties, which is an urgent engineering roadblock to be solved in the construction of tunnel in karst area. In this paper, three-dimensional discrete element method considering fluid-solid coupling effect and structural characteristics of water-mud resistant rock mass is adopted to systematically study the evolution law of displacement field and seepage field of intermittent joint type water-mud resistant rock mass of tunnel face and its water inrush critical characteristics during the process of sequential excavation of karst tunnel close to the frontal high-pressure water-rich karst cavity. The results show that: With the tunnel face gradually approaching the front-concealed high-pressure water-rich karst cavity, the stability of water-mud resistant rock mass is increasingly affected by high-pressure karst water, and karst water pressure gradually becomes the main control factor. The closer the tunnel face is to the front-concealed high-pressure water-rich karst cavity, the greater the extrusion displacement of karst tunnel face and its increase amplitude, the higher damage degree of water-mud resistant rock mass of face. With the advance of tunnel excavation, the intermittent cracks in the water-mud resistant rock mass of face gradually connect and form a stable hydraulic connection. The flow velocity and seepage pressure of karst water rise significantly at the moment of overall instability of face and the formation of water inrush channel, showing obvious precursor characteristics. The research achievements provide a reference for early warning and prevention and control of water inrush disaster of karst tunnel face.","PeriodicalId":502439,"journal":{"name":"Electronic Journal of Structural Engineering","volume":" 490","pages":""},"PeriodicalIF":0.0,"publicationDate":"2023-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139137020","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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