Iraq Ahmad Reshi, Asif H. Shah, Abrak Jan, Zainab Tariq, Sahil Sholla, Sami Rashid, Mohammad Umer Wani
This study uses machine learning techniques to investigate the bond strength between steel and concrete under various elevated temperature scenarios. Five distinct machine learning algorithms, including Random Forest (RF), XGBoost, AdaBoost, Decision Tree, Linear Regression, and hyperparameteric optimisations, were used to predict changes in bond strength. The models underwent rigorous optimisation using GridSearchCV to achieve optimal performance. In this study, we evaluated several metrics such as Mean Squared Error, Root Mean Squared Error, Mean Absolute Error, and coefficient of determination (R2) Score to compare and assess the models' prediction capabilities. After optimisation, results indicate that the RF model exhibited exceptional performance in estimating bond strength across different temperature conditions, demonstrating minimal errors and a high R2 Score. Visual comparisons of actual and predicted values further confirmed the efficacy of the RF model in capturing complex fluctuations in bond strength. The findings of this study underscore the potential of machine learning models, particularly the optimized RF method, in accurately predicting bond strength under varying thermal conditions, with promising implications for engineering and construction practices.
{"title":"Machine learning enhanced modeling of steel‐concrete bond strength under elevated temperature exposure","authors":"Iraq Ahmad Reshi, Asif H. Shah, Abrak Jan, Zainab Tariq, Sahil Sholla, Sami Rashid, Mohammad Umer Wani","doi":"10.1002/suco.202400334","DOIUrl":"https://doi.org/10.1002/suco.202400334","url":null,"abstract":"This study uses machine learning techniques to investigate the bond strength between steel and concrete under various elevated temperature scenarios. Five distinct machine learning algorithms, including Random Forest (RF), XGBoost, AdaBoost, Decision Tree, Linear Regression, and hyperparameteric optimisations, were used to predict changes in bond strength. The models underwent rigorous optimisation using GridSearchCV to achieve optimal performance. In this study, we evaluated several metrics such as Mean Squared Error, Root Mean Squared Error, Mean Absolute Error, and coefficient of determination (<jats:italic>R</jats:italic><jats:sup>2</jats:sup>) Score to compare and assess the models' prediction capabilities. After optimisation, results indicate that the RF model exhibited exceptional performance in estimating bond strength across different temperature conditions, demonstrating minimal errors and a high <jats:italic>R</jats:italic><jats:sup>2</jats:sup> Score. Visual comparisons of actual and predicted values further confirmed the efficacy of the RF model in capturing complex fluctuations in bond strength. The findings of this study underscore the potential of machine learning models, particularly the optimized RF method, in accurately predicting bond strength under varying thermal conditions, with promising implications for engineering and construction practices.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"25 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587857","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Qiang Wang, Xu‐hua Liang, Xin Liu, Shi‐ping Guo, Chun‐ling Lu
To address the issue of easy shearing damage of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the axial compressive performance of CFRP and Ultra‐High‐Performance Concrete (UHPC) strengthened concrete columns, two methods, prestressed CFRP and UHPC with spiral stirrups, were employed for composite strengthening of reinforced concrete (RC) columns. A total of one unstrengthened column and eight strengthened columns were designed and fabricated to validate the effectiveness of the proposed methods. The axial compressive performance and bearing capacity of each specimen were analyzed by considering parameters such as single or composite strengthening method, presence of spiral stirrups in UHPC, and application of pre‐stressed CFRP. The results show that, compared with any single strengthened specimen, the ultimate bearing capacity of the composite strengthened specimen is greater than the sum of the corresponding single strengthened specimens, and the bearing capacity of the prestressed CFRP with spiral stirrup UHPC composite strengthened specimen is the most significant, reaching 235.63%. By incorporating spiral stirrups in the UHPC jacket, the phenomenon of uneven fragmentation during the failure of the strengthened column is improved. This helps prevent premature shearing damage of CFRP and enhances the fracture strain and effective utilization of CFRP. Additionally, prestressed CFRP effectively restrains the lateral deformation and crack development of the core concrete in the UHPC jacket, fully utilizing the high compressive strength of UHPC. This further enhances the ultimate bearing capacity and ductility of the specimens. Based on the experimental phenomena and strain of each material, the failure mechanism of prestressed CFRP‐spiral reinforced UHPC composite‐strengthened columns is proposed. Finally, a unified bearing capacity calculation formula for single and composite strengthened columns is established, based on the theory of confined concrete strength and the assumption of strength increment superposition. The formula is validated with experimental results from relevant literature, showing small errors in the calculated results and indicating good applicability of the formula.
{"title":"Axial compressive performance of RC columns strengthened with prestressed CFRP fabric and UHPC jacket with spiral stirrups","authors":"Qiang Wang, Xu‐hua Liang, Xin Liu, Shi‐ping Guo, Chun‐ling Lu","doi":"10.1002/suco.202400072","DOIUrl":"https://doi.org/10.1002/suco.202400072","url":null,"abstract":"To address the issue of easy shearing damage of Carbon Fiber Reinforced Polymer (CFRP) in enhancing the axial compressive performance of CFRP and Ultra‐High‐Performance Concrete (UHPC) strengthened concrete columns, two methods, prestressed CFRP and UHPC with spiral stirrups, were employed for composite strengthening of reinforced concrete (RC) columns. A total of one unstrengthened column and eight strengthened columns were designed and fabricated to validate the effectiveness of the proposed methods. The axial compressive performance and bearing capacity of each specimen were analyzed by considering parameters such as single or composite strengthening method, presence of spiral stirrups in UHPC, and application of pre‐stressed CFRP. The results show that, compared with any single strengthened specimen, the ultimate bearing capacity of the composite strengthened specimen is greater than the sum of the corresponding single strengthened specimens, and the bearing capacity of the prestressed CFRP with spiral stirrup UHPC composite strengthened specimen is the most significant, reaching 235.63%. By incorporating spiral stirrups in the UHPC jacket, the phenomenon of uneven fragmentation during the failure of the strengthened column is improved. This helps prevent premature shearing damage of CFRP and enhances the fracture strain and effective utilization of CFRP. Additionally, prestressed CFRP effectively restrains the lateral deformation and crack development of the core concrete in the UHPC jacket, fully utilizing the high compressive strength of UHPC. This further enhances the ultimate bearing capacity and ductility of the specimens. Based on the experimental phenomena and strain of each material, the failure mechanism of prestressed CFRP‐spiral reinforced UHPC composite‐strengthened columns is proposed. Finally, a unified bearing capacity calculation formula for single and composite strengthened columns is established, based on the theory of confined concrete strength and the assumption of strength increment superposition. The formula is validated with experimental results from relevant literature, showing small errors in the calculated results and indicating good applicability of the formula.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"35 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587859","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper proposes a new design code formulation for calculating crack widths for regular and more special reinforced concrete (RC) members. The more comprehensive Modified Tension Chord Model (MTCM) has been simplified (SMTCM) to facilitate an alternative method for calculating crack widths to Eurocode 2 and fib Model Codes. The model is based on mechanical principles without empirical modifications and is benchmarked against a previously published experimental crack width database. The SMTCM predicts crack widths quite as accurately as the MTCM and provides a broader range of applicability, such as for large covers and RC ties having arbitrary rebar configurations and thus a better crack width model than the current design codes for RC ties. In addition, there are no openings for ambiguous interpretations of the calculations, which can increase the risk of obtaining two different crack widths from two different designers. To further justify the SMTCM code formulation and concept, several RC ties with experimental crack width profiles were used and discussed. The results show a considerable difference between the crack width profile at the surface and at the reinforcement location, depending on the concrete cover and rebar size. These observations are interesting regarding durability design and requirements and show that the approach using a maximum design crack width at a specific surface as a decisive parameter should be further investigated, especially for large concrete covers.
{"title":"Simplified modified tension chord model: An alternative crack width calculation model to Eurocode 2 and fib model codes","authors":"Otto Terjesen, Terje Kanstad, Reignard Tan","doi":"10.1002/suco.202400329","DOIUrl":"https://doi.org/10.1002/suco.202400329","url":null,"abstract":"This paper proposes a new design code formulation for calculating crack widths for regular and more special reinforced concrete (RC) members. The more comprehensive Modified Tension Chord Model (MTCM) has been simplified (SMTCM) to facilitate an alternative method for calculating crack widths to Eurocode 2 and <jats:italic>fib</jats:italic> Model Codes. The model is based on mechanical principles without empirical modifications and is benchmarked against a previously published experimental crack width database. The SMTCM predicts crack widths quite as accurately as the MTCM and provides a broader range of applicability, such as for large covers and RC ties having arbitrary rebar configurations and thus a better crack width model than the current design codes for RC ties. In addition, there are no openings for ambiguous interpretations of the calculations, which can increase the risk of obtaining two different crack widths from two different designers. To further justify the SMTCM code formulation and concept, several RC ties with experimental crack width profiles were used and discussed. The results show a considerable difference between the crack width profile at the surface and at the reinforcement location, depending on the concrete cover and rebar size. These observations are interesting regarding durability design and requirements and show that the approach using a maximum design crack width at a specific surface as a decisive parameter should be further investigated, especially for large concrete covers.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"78 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141587856","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Although plain round or square section reinforcement is no longer used in new construction, there are many older structures still in service built with such bars. In recognition of the need for guidance on the assessment of load‐carrying capacity of structures reinforced with such bars, design codes are now introducing or re‐introducing provisions to assess the capacity of laps and anchorages of such reinforcement. The authors have contributed to the introduction of design rules in the fib Model Code 2020. This paper describes the derivation of these provisions. Starting from the form of expression proposed earlier by the authors, the data from which these proposals are derived is specified and modifications in interpretation preparatory to a statistical analysis are outlined. A rigorous multivariate statistical procedure is then employed firstly to determine a mean strength expression for the capacity of anchorages and laps which is then validated against test data. Further statistical analysis is subsequently used to determine a design expression using the approach outlined in EN 1990, taking appropriate account scatter in test data. Finally, some comparisons are presented between the assessment expressions proposed and design provisions that were in place when these types of bars were in common use. Areas where earlier design provisions may be non‐conservative are identified.
尽管普通圆形或方形截面钢筋已不再用于新建筑中，但仍有许多使用此类钢筋的旧建筑在使用中。考虑到需要对使用此类钢筋加固的结构的承载能力评估提供指导，设计规范目前正在引入或重新引入有关条款，以评估此类钢筋的搭接和锚固的承载能力。作者为在《2020 纤维示范规范》中引入设计规则做出了贡献。本文介绍了这些规定的推导过程。从作者早先提出的表达形式开始，具体说明了这些建议所依据的数据，并概述了为统计分析做准备的解释修改。然后采用严格的多元统计程序，首先确定锚固件和搭接件承载力的平均强度表达式，然后根据测试数据对其进行验证。随后，使用 EN 1990 中概述的方法进行进一步的统计分析，以确定设计表达式，同时适当考虑测试数据的分散性。最后，对提出的评估表达式与这些类型的钢筋普遍使用时的设计规定进行了比较。确定了早期设计规定可能不严谨的地方。
{"title":"Anchorage and lap capacity of plain surface and square twisted bars in existing R.C. Structures: A comprehensive approach","authors":"John Cairns, Lisa R. Feldman, Fabrizio Palmisano","doi":"10.1002/suco.202400081","DOIUrl":"https://doi.org/10.1002/suco.202400081","url":null,"abstract":"Although plain round or square section reinforcement is no longer used in new construction, there are many older structures still in service built with such bars. In recognition of the need for guidance on the assessment of load‐carrying capacity of structures reinforced with such bars, design codes are now introducing or re‐introducing provisions to assess the capacity of laps and anchorages of such reinforcement. The authors have contributed to the introduction of design rules in the <jats:italic>fib</jats:italic> Model Code 2020. This paper describes the derivation of these provisions. Starting from the form of expression proposed earlier by the authors, the data from which these proposals are derived is specified and modifications in interpretation preparatory to a statistical analysis are outlined. A rigorous multivariate statistical procedure is then employed firstly to determine a mean strength expression for the capacity of anchorages and laps which is then validated against test data. Further statistical analysis is subsequently used to determine a design expression using the approach outlined in EN 1990, taking appropriate account scatter in test data. Finally, some comparisons are presented between the assessment expressions proposed and design provisions that were in place when these types of bars were in common use. Areas where earlier design provisions may be non‐conservative are identified.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"20 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568139","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carlos H. Mosquera, Melissa P. Acosta, William A. Rodríguez, Diego A. Mejía‐España, Jonhatan R. Torres, Daniela M. Martinez, Joaquín Abellán‐García
Rising environmental awareness has prompted in‐depth studies on how the concrete industry affects the environment. Using recycled concrete aggregates (RCAs) and supplementary cementitious materials (SCMs) in concrete manufacturing provides advantages for sustainability. However, the broader chemical composition of SCMs and the inferior qualities of RCAs compared with natural aggregates (NAs) often lead to a decrease in concrete mechanical strength. The difficulty lies in foreseeing how the inclusion of SCMs and RCAs will affect the concrete compressive strength. The artificial neural network (ANN) approach presented herein can precisely forecast the recycled aggregate concrete (RAC) compressive strength, even when incorporates SCMs. The analysis employing the connection weight approach (CWA) determines how input variables influence compressive strength. Results indicate silica fume contributes most to compressive strength, followed by cement content, silica modulus, fine natural aggregate dosage, and coarse natural aggregate. Additionally, the amount of water utilized, the water/cement ratio, and the presence of RCA are all detrimental to compressive strength. The adverse effect of the cementitious materials' alumina modulus can be attributed to increased water demand during their reaction. Performance metrics of the final ANN model on the testing data subset include R2 = 0.94, and RMSE = 3.11, utilizing 834 data observations after outlier treatment for training and validation purposes. In summary, the ANN‐based approach demonstrates its efficacy in predicting concrete compressive strength when incorporating SCMs and RCAs, shedding light on the influential factors in concrete performance.
{"title":"ANN‐based analysis of the effect of SCM on recycled aggregate concrete","authors":"Carlos H. Mosquera, Melissa P. Acosta, William A. Rodríguez, Diego A. Mejía‐España, Jonhatan R. Torres, Daniela M. Martinez, Joaquín Abellán‐García","doi":"10.1002/suco.202400024","DOIUrl":"https://doi.org/10.1002/suco.202400024","url":null,"abstract":"Rising environmental awareness has prompted in‐depth studies on how the concrete industry affects the environment. Using recycled concrete aggregates (RCAs) and supplementary cementitious materials (SCMs) in concrete manufacturing provides advantages for sustainability. However, the broader chemical composition of SCMs and the inferior qualities of RCAs compared with natural aggregates (NAs) often lead to a decrease in concrete mechanical strength. The difficulty lies in foreseeing how the inclusion of SCMs and RCAs will affect the concrete compressive strength. The artificial neural network (ANN) approach presented herein can precisely forecast the recycled aggregate concrete (RAC) compressive strength, even when incorporates SCMs. The analysis employing the connection weight approach (CWA) determines how input variables influence compressive strength. Results indicate silica fume contributes most to compressive strength, followed by cement content, silica modulus, fine natural aggregate dosage, and coarse natural aggregate. Additionally, the amount of water utilized, the water/cement ratio, and the presence of RCA are all detrimental to compressive strength. The adverse effect of the cementitious materials' alumina modulus can be attributed to increased water demand during their reaction. Performance metrics of the final ANN model on the testing data subset include <jats:italic>R</jats:italic><jats:sup>2</jats:sup> = 0.94, and RMSE = 3.11, utilizing 834 data observations after outlier treatment for training and validation purposes. In summary, the ANN‐based approach demonstrates its efficacy in predicting concrete compressive strength when incorporating SCMs and RCAs, shedding light on the influential factors in concrete performance.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"14 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568140","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Tarek Sharaf, Sara Ismail, Mohamed Elghandour, Ahmed Turk
This paper investigated the blast behavior of a low‐rise composite steel structure of three stories subjected to internal and external explosions for the same explosive charge of 250 kg TNT. A comparison of three various blast scenarios is aimed at better understanding how blast waves propagate in confined risk zones and their damage effects on far and exposed elements to an explosive charge. Evaluation of the damage level and the overall response of the proposed numerical model is done by estimating the adequacy of structural members subjected to blast loading using general limits in attempting to check the structure's strength and regularity. The analysis was based on load combinations and damage criteria according to the Unified Facilities Criteria which are general design approaches suitable for civil design applications in forecasting blast loads and structural system responses. The overall behavior of this structure was simulated based on a dynamic analysis by the direct simulation approach, which was chosen for modeling blast loads using the Friedlander blast load equation, and the simpler, less expensive, more accurate, and realistic A.T.‐BLAST model to deduce the simplified blast‐wave overpressure profile. The material nonlinearity at a high strain rate using the Johnson‐Cook strength and concrete plasticity damage model is studied dynamically using ABAQUS finite element code to simulate the explicit dynamic nonlinear analysis. The overall response of the proposed numerical model was evaluated by estimating the adequacy of structural members, considering the blast load as the initial cause of failure, such as axial plastic strain, internal forces limits, maximum deformation, support rotation, demand‐capacity‐ratio (DCRshear/moment), drift index and material damage model. The position of the explosive charge played an important role in determining the rate at which the structural element begins to plastic strains, displacements, moments, or rotations beyond the limits, and then key elements should be considered in structural design against progressive collapse. Results showed that steel members exhibit early indicators of failure, such as buckling necking, shear tearing, or plastic hinges, whereas concrete slabs break up immediately due to brittleness. DCRmoment values successfully showed the columns in which the first plastic joint can occur, whereas DCRshear values signaled the onset of shear failure at connections. Besides, plastic hinges played an important role in dissipating energy and preventing total structural collapse via the Strong Column‐Weak Beam design concept, which appears repeatedly in this study. The structure is a well‐designed and ductile building capable of supporting higher loads and is considered to be repairable and intact.
{"title":"Numerical study of low‐rise composite steel frame responses to blast loading using direct simulation method","authors":"Tarek Sharaf, Sara Ismail, Mohamed Elghandour, Ahmed Turk","doi":"10.1002/suco.202400363","DOIUrl":"https://doi.org/10.1002/suco.202400363","url":null,"abstract":"This paper investigated the blast behavior of a low‐rise composite steel structure of three stories subjected to internal and external explosions for the same explosive charge of 250 kg TNT. A comparison of three various blast scenarios is aimed at better understanding how blast waves propagate in confined risk zones and their damage effects on far and exposed elements to an explosive charge. Evaluation of the damage level and the overall response of the proposed numerical model is done by estimating the adequacy of structural members subjected to blast loading using general limits in attempting to check the structure's strength and regularity. The analysis was based on load combinations and damage criteria according to the Unified Facilities Criteria which are general design approaches suitable for civil design applications in forecasting blast loads and structural system responses. The overall behavior of this structure was simulated based on a dynamic analysis by the direct simulation approach, which was chosen for modeling blast loads using the Friedlander blast load equation, and the simpler, less expensive, more accurate, and realistic A.T.‐BLAST model to deduce the simplified blast‐wave overpressure profile. The material nonlinearity at a high strain rate using the Johnson‐Cook strength and concrete plasticity damage model is studied dynamically using ABAQUS finite element code to simulate the explicit dynamic nonlinear analysis. The overall response of the proposed numerical model was evaluated by estimating the adequacy of structural members, considering the blast load as the initial cause of failure, such as axial plastic strain, internal forces limits, maximum deformation, support rotation, demand‐capacity‐ratio (DCR<jats:sub>shear/moment</jats:sub>), drift index and material damage model. The position of the explosive charge played an important role in determining the rate at which the structural element begins to plastic strains, displacements, moments, or rotations beyond the limits, and then key elements should be considered in structural design against progressive collapse. Results showed that steel members exhibit early indicators of failure, such as buckling necking, shear tearing, or plastic hinges, whereas concrete slabs break up immediately due to brittleness. DCR<jats:sub>moment</jats:sub> values successfully showed the columns in which the first plastic joint can occur, whereas DCR<jats:sub>shear</jats:sub> values signaled the onset of shear failure at connections. Besides, plastic hinges played an important role in dissipating energy and preventing total structural collapse via the Strong Column‐Weak Beam design concept, which appears repeatedly in this study. The structure is a well‐designed and ductile building capable of supporting higher loads and is considered to be repairable and intact.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"8 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141568141","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Aimin Yuan, Xinge Miao, Qi Chen, Xi Wang, Hu Kong, Keqin Wang, Jingquan Wang
Prestress concrete composite girders with full‐depth precast bridge deck panels (PC composite girders) have been widely utilized in civil engineering due to their high production quality, reduced construction duration, potential weight reduction, and lower life‐cycle cost. The interface shear behavior in ultra high‐performance concrete (UHPC)–normal concrete (NC) connection interface of full‐depth deck PC composite girder has been extensively studied. This study conducted seven push‐off tests to examine the shear performance of UHPC‐filled joints between precast I‐girders and full‐depth precast concrete slabs. The testing variables included the quantity, and spacing of the Ubars, as well as the type of UHPC‐filled joints (longitudinal trough connector or pocket connector). The experimental results show the quantity and spacing of Ubars have a significant impact on both the interface shear capacity and residual shear resistance. For continuous shear connectors with reserved notches specimens, the ultimate load of the 4Ubar and 6Ubar specimens increased by 93% and 194%, respectively, compared with the 2Ubar specimens. With the increase of the spacing of the Ubar, the ultimate load will decrease. When the spacing between Ubars increases from 100 to 150 mm, the normalized ultimate load decreases by 51 kN. The type of joints also plays a crucial role in determining the ultimate shear‐bearing capacity of the specimens. The Ubars in pocket connector specimens will provide a greater contribution to the ultimate shear bearing capacity than longitudinal trough connector specimens and the ultimate stress of the 4Ubar and 6Ubar pocket connector specimens are greater than that of the longitudinal trough connector specimens by 232% and 323%. The study introduces the concept of pulling angle. In the experiment, the specimen with a large length is less affected by the pulling force. The experimental results in this study can rarely be predicted well by typical equations developed in current design codes and previous studies. Therefore, a more accurate equation was developed to predict the interface shear transfer stress between precast common concrete I‐girder and full‐depth precast concrete slab with UHPC‐filled joints.
{"title":"Comparative shear performance of ultra high‐performance concrete filled pocket and longitudinal trough connector of PC composite girder with full‐depth deck","authors":"Aimin Yuan, Xinge Miao, Qi Chen, Xi Wang, Hu Kong, Keqin Wang, Jingquan Wang","doi":"10.1002/suco.202400410","DOIUrl":"https://doi.org/10.1002/suco.202400410","url":null,"abstract":"Prestress concrete composite girders with full‐depth precast bridge deck panels (PC composite girders) have been widely utilized in civil engineering due to their high production quality, reduced construction duration, potential weight reduction, and lower life‐cycle cost. The interface shear behavior in ultra high‐performance concrete (UHPC)–normal concrete (NC) connection interface of full‐depth deck PC composite girder has been extensively studied. This study conducted seven push‐off tests to examine the shear performance of UHPC‐filled joints between precast I‐girders and full‐depth precast concrete slabs. The testing variables included the quantity, and spacing of the Ubars, as well as the type of UHPC‐filled joints (longitudinal trough connector or pocket connector). The experimental results show the quantity and spacing of Ubars have a significant impact on both the interface shear capacity and residual shear resistance. For continuous shear connectors with reserved notches specimens, the ultimate load of the 4Ubar and 6Ubar specimens increased by 93% and 194%, respectively, compared with the 2Ubar specimens. With the increase of the spacing of the Ubar, the ultimate load will decrease. When the spacing between Ubars increases from 100 to 150 mm, the normalized ultimate load decreases by 51 kN. The type of joints also plays a crucial role in determining the ultimate shear‐bearing capacity of the specimens. The Ubars in pocket connector specimens will provide a greater contribution to the ultimate shear bearing capacity than longitudinal trough connector specimens and the ultimate stress of the 4Ubar and 6Ubar pocket connector specimens are greater than that of the longitudinal trough connector specimens by 232% and 323%. The study introduces the concept of pulling angle. In the experiment, the specimen with a large length is less affected by the pulling force. The experimental results in this study can rarely be predicted well by typical equations developed in current design codes and previous studies. Therefore, a more accurate equation was developed to predict the interface shear transfer stress between precast common concrete I‐girder and full‐depth precast concrete slab with UHPC‐filled joints.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"1 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141549296","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
When building a tunnel in an environment rich in high‐temperature hot water, it is particularly necessary to pay attention to the influence of sulfate ions in underground hot water on tunnel shotcrete. In order to study the sulfate erosion mechanism and mechanical properties of shotcrete in a real high‐temperature hot water environment, this study was carried out by setting the curing temperature (20, 40, 60, and 80°C), humidity (55% RH, 95% RH), and erosion age (0, 15, 30, 60, and 90 d) as the test influencing factors; a full combination of dry‐wet cycle test was carried out, and the specimens under different conditions were analyzed macroscopically and microscopically. The results show that with the increase of the number of dry‐wet cycles, the quality of shotcrete increases first and then decreases, and the mechanical properties gradually decrease. In the early stage of erosion, the erosion product is mainly ettringite, and the macroscopic damage is aggregate spalling. In the later stage of erosion, the erosion product is mainly gypsum, and the macroscopic damage is expansion damage. Compared with standard curing, a certain degree of high temperature curing has little effect on the sulfate attack resistance of shotcrete, but when the curing temperature exceeds 60°C, the concrete is seriously damaged. Finally, by constructing the damage model of sulfate attack shotcrete, the variation of compressive strength of shotcrete with age after sulfate attack under different curing conditions was successfully predicted.
{"title":"A study on the sulfate erosion deterioration law and damage model of shotcrete in high geothermal tunnels","authors":"Jianjun Tong, Lulu Xiang, Yanshan Cai, Mingnian Wang, Pei Ye, Xingwang Miao","doi":"10.1002/suco.202301117","DOIUrl":"https://doi.org/10.1002/suco.202301117","url":null,"abstract":"When building a tunnel in an environment rich in high‐temperature hot water, it is particularly necessary to pay attention to the influence of sulfate ions in underground hot water on tunnel shotcrete. In order to study the sulfate erosion mechanism and mechanical properties of shotcrete in a real high‐temperature hot water environment, this study was carried out by setting the curing temperature (20, 40, 60, and 80°C), humidity (55% RH, 95% RH), and erosion age (0, 15, 30, 60, and 90 d) as the test influencing factors; a full combination of dry‐wet cycle test was carried out, and the specimens under different conditions were analyzed macroscopically and microscopically. The results show that with the increase of the number of dry‐wet cycles, the quality of shotcrete increases first and then decreases, and the mechanical properties gradually decrease. In the early stage of erosion, the erosion product is mainly ettringite, and the macroscopic damage is aggregate spalling. In the later stage of erosion, the erosion product is mainly gypsum, and the macroscopic damage is expansion damage. Compared with standard curing, a certain degree of high temperature curing has little effect on the sulfate attack resistance of shotcrete, but when the curing temperature exceeds 60°C, the concrete is seriously damaged. Finally, by constructing the damage model of sulfate attack shotcrete, the variation of compressive strength of shotcrete with age after sulfate attack under different curing conditions was successfully predicted.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"21 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-07-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141523052","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In internally post‐tensioned (PT) prestressed concrete (PC) structures, the prestressing system is usually made of high‐strength steel tendons embedded within concrete through either metallic or plastic ducts filled with cement grout or grease. Construction defects or degradation phenomena may lead to insufficient covering, exposing the prestressing steel to a harmful environment, potentially compromising the durability and load‐bearing capacity of the structure. Based on experimental tests on six 1:5 scaled PT specimens, this study presents accurate numerical simulations of four‐point bending tests on girders with unbonded and partially bonded tendons having different levels of initial prestress. Nonlinear finite element analyses (FEAs) were developed to reflect the friction‐type interaction mechanism between unbonded tendons and external ducts under increasing external load up to failure. Both global and local response parameters of the girders were studied validating numerical results against experimental findings. The numerical simulations provide insights on the stress pattern of unbonded and partially bonded strands, shedding light on the lower bearing capacity of defective girders compared to those with bonded tendons. Such findings contribute to a multi‐scale assessment and decision‐making framework for existing PT girders with defective grouting and low residual prestress levels, enhancing the understanding of their structural behavior and informing maintenance or retrofitting decisions.
{"title":"Numerical simulation of post‐tensioned concrete girders with defective grouting including local stress–strain tendons response","authors":"Simone Galano, Daniele Losanno, Fulvio Parisi","doi":"10.1002/suco.202400416","DOIUrl":"https://doi.org/10.1002/suco.202400416","url":null,"abstract":"In internally post‐tensioned (PT) prestressed concrete (PC) structures, the prestressing system is usually made of high‐strength steel tendons embedded within concrete through either metallic or plastic ducts filled with cement grout or grease. Construction defects or degradation phenomena may lead to insufficient covering, exposing the prestressing steel to a harmful environment, potentially compromising the durability and load‐bearing capacity of the structure. Based on experimental tests on six 1:5 scaled PT specimens, this study presents accurate numerical simulations of four‐point bending tests on girders with unbonded and partially bonded tendons having different levels of initial prestress. Nonlinear finite element analyses (FEAs) were developed to reflect the friction‐type interaction mechanism between unbonded tendons and external ducts under increasing external load up to failure. Both global and local response parameters of the girders were studied validating numerical results against experimental findings. The numerical simulations provide insights on the stress pattern of unbonded and partially bonded strands, shedding light on the lower bearing capacity of defective girders compared to those with bonded tendons. Such findings contribute to a multi‐scale assessment and decision‐making framework for existing PT girders with defective grouting and low residual prestress levels, enhancing the understanding of their structural behavior and informing maintenance or retrofitting decisions.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"30 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Islam N. Fathy, Alaa A. El‐Sayed, Bassam A. Tayeh, Alaa A. Mahmoud, Mohamed A. Abouelnour, Maged E. Elfakharany
This study investigates the individual and combined effects of micro and nano lead monoxide (PbO) and granodiorite (GD) on concrete's mechanical and radiation shielding properties. Both materials were partially substituted for cement at varying ratios. Additionally, mixtures with optimal radiation shielding performance were prepared to explore the synergy of combining them. The mentioned materials are used for the first time in an extensive study at the nano scale to investigate their impact on concrete's mechanical properties, microstructure, and gamma radiation attenuation. Two gamma ray sources of uranium (U238) and cesium (Cs137) were used measure the radiation attenuation coefficients for all designed concrete mixes. A simple methodology was followed to assess the concrete shields efficiency via utilizing portable handheld gamma‐ray spectrometer that offers two reading modes. Results indicated that increasing the ratio of PbO is directly proportional to the concrete ability to attenuate radiation, where the optimal individual replacement ratios were recorded at 5% for micro and nano particle sizes. At this ratio, the linear attenuation coefficient (μ) values were improved by 39.57% and 24.78% for the nano and micro PbO, respectively. Additionally, the optimal ratio for improving mechanical properties was at 3% and 2% for nano and micro PbO, while the higher ratios showed a decline in mechanical properties especially at 5% micro PbO with 7.02% reduction in the compressive strength value. Regarding GD powder, the optimal replacement ratios for improving concrete radiation shielding were consistent with those enhancing its mechanical properties at 4% and 7% in both nano and micro scales, respectively. The combined mixes further enhanced the overall concrete performance, especially its radiation shielding ability. Compared to the control mix, the compressive strength, tensile strength, and μ were increased by 25.7%, 16.2%, and 44.7% at the optimal mixture of 5% nano PbO + 4% nano GD.
{"title":"Enhancing mechanical and radiation shielding properties of concrete with lead monoxide and granodiorite: Individual and synergistic effects at micro and nano particle scales","authors":"Islam N. Fathy, Alaa A. El‐Sayed, Bassam A. Tayeh, Alaa A. Mahmoud, Mohamed A. Abouelnour, Maged E. Elfakharany","doi":"10.1002/suco.202400454","DOIUrl":"https://doi.org/10.1002/suco.202400454","url":null,"abstract":"This study investigates the individual and combined effects of micro and nano lead monoxide (PbO) and granodiorite (GD) on concrete's mechanical and radiation shielding properties. Both materials were partially substituted for cement at varying ratios. Additionally, mixtures with optimal radiation shielding performance were prepared to explore the synergy of combining them. The mentioned materials are used for the first time in an extensive study at the nano scale to investigate their impact on concrete's mechanical properties, microstructure, and gamma radiation attenuation. Two gamma ray sources of uranium (U<jats:sup>238</jats:sup>) and cesium (Cs<jats:sup>137</jats:sup>) were used measure the radiation attenuation coefficients for all designed concrete mixes. A simple methodology was followed to assess the concrete shields efficiency via utilizing portable handheld gamma‐ray spectrometer that offers two reading modes. Results indicated that increasing the ratio of PbO is directly proportional to the concrete ability to attenuate radiation, where the optimal individual replacement ratios were recorded at 5% for micro and nano particle sizes. At this ratio, the linear attenuation coefficient (<jats:italic>μ</jats:italic>) values were improved by 39.57% and 24.78% for the nano and micro PbO, respectively. Additionally, the optimal ratio for improving mechanical properties was at 3% and 2% for nano and micro PbO, while the higher ratios showed a decline in mechanical properties especially at 5% micro PbO with 7.02% reduction in the compressive strength value. Regarding GD powder, the optimal replacement ratios for improving concrete radiation shielding were consistent with those enhancing its mechanical properties at 4% and 7% in both nano and micro scales, respectively. The combined mixes further enhanced the overall concrete performance, especially its radiation shielding ability. Compared to the control mix, the compressive strength, tensile strength, and <jats:italic>μ</jats:italic> were increased by 25.7%, 16.2%, and 44.7% at the optimal mixture of 5% nano PbO + 4% nano GD.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"61 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-06-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141529248","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：