The present study proposes a new technique for retrofitting corroded beam–column joints (BCJs) using high‐strength fiber reinforced concrete (HSFRC) and stirrups replacement. The entire corrosion‐affected concrete was removed and replaced with HSFRC. The corroded reinforcing bars were cleaned and treated to resist the progression of the corrosion mechanism. The severely pitted stirrups were replaced with new stirrups. Four exterior BCJ specimens were tested under seismic loading to determine the effectiveness of the proposed retrofitting scheme. The efficacy of the proposed retrofitting scheme is determined in terms of the hysteresis response, stiffness degradation, cumulative energy dissipation, ductility, and damage index. A significant delay in the fracture of severely pitted reinforcing bars was experienced for the corrosion‐damaged retrofitted specimens compared to the corroded unretrofitted specimen. The cumulative energy dissipation of the corroded unretrofitted and corroded retrofitted specimens was 0.4 and 1.3 times that of the reference specimen, respectively, indicating the effectiveness of the retrofitting strategy, as both specimens had similar corrosion rates. The test results indicated that the proposed retrofitting technique effectively improved the seismic performance of the corrosion‐damaged BCJs.
{"title":"Performance of corroded RC beam–column joints repaired using a hybrid scheme with HSFRC and stirrups replacement","authors":"Shubham Dangwal, Tasham Kumar, Heaven Singh, Raju Sharma","doi":"10.1002/suco.202400654","DOIUrl":"https://doi.org/10.1002/suco.202400654","url":null,"abstract":"The present study proposes a new technique for retrofitting corroded beam–column joints (BCJs) using high‐strength fiber reinforced concrete (HSFRC) and stirrups replacement. The entire corrosion‐affected concrete was removed and replaced with HSFRC. The corroded reinforcing bars were cleaned and treated to resist the progression of the corrosion mechanism. The severely pitted stirrups were replaced with new stirrups. Four exterior BCJ specimens were tested under seismic loading to determine the effectiveness of the proposed retrofitting scheme. The efficacy of the proposed retrofitting scheme is determined in terms of the hysteresis response, stiffness degradation, cumulative energy dissipation, ductility, and damage index. A significant delay in the fracture of severely pitted reinforcing bars was experienced for the corrosion‐damaged retrofitted specimens compared to the corroded unretrofitted specimen. The cumulative energy dissipation of the corroded unretrofitted and corroded retrofitted specimens was 0.4 and 1.3 times that of the reference specimen, respectively, indicating the effectiveness of the retrofitting strategy, as both specimens had similar corrosion rates. The test results indicated that the proposed retrofitting technique effectively improved the seismic performance of the corrosion‐damaged BCJs.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"1 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204003","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}
Tan Wang, Liwei Li, Lijun Dou, Qian Huang, Zhijie Zhou, Yibo Cao, Fan Yang, Zhu Zhu
The paper investigates the behavior of glass‐fiber reinforced polymer (GFRP) reinforced concrete columns with integrated steel spirals (hybrid reinforcement). Six concrete columns were tested under eccentric axial loading, resulting in failure due to bending. Columns with outer steel longitudinal bars experienced steel yielding at peak loads, while those with GFRP outer rebars failed due to concrete crushing. The results revealed that using GFRP as outer longitudinal bars led to peak loads 3–10% lower compared to columns with steel rebars. Inner confinement by steel spirals increased the load‐carrying capacity. Additionally, columns with inner tubular steel exhibited greater strength than those with steel spirals, indicating a slightly enhanced confinement effect. A finite element model was developed to analyze structural behavior, considering both material and geometric nonlinearity. The model's accuracy was validated by comparing predictions with test results. Parametric analysis from the nonlinear FE model showed that eccentricity significantly impacted column load‐carrying capacity. Increasing inner confinement area and the number of inner longitudinal bars improved structural stiffness and load‐carrying capacity. Furthermore, a simplified theoretical method was proposed. Comparison between experimental failure loads and theoretical predictions revealed differences within 20%, indicating satisfactory reliability of the proposed method.
{"title":"Behavior of GFRP reinforced concrete columns confined with inner steel spirals","authors":"Tan Wang, Liwei Li, Lijun Dou, Qian Huang, Zhijie Zhou, Yibo Cao, Fan Yang, Zhu Zhu","doi":"10.1002/suco.202300746","DOIUrl":"https://doi.org/10.1002/suco.202300746","url":null,"abstract":"The paper investigates the behavior of glass‐fiber reinforced polymer (GFRP) reinforced concrete columns with integrated steel spirals (hybrid reinforcement). Six concrete columns were tested under eccentric axial loading, resulting in failure due to bending. Columns with outer steel longitudinal bars experienced steel yielding at peak loads, while those with GFRP outer rebars failed due to concrete crushing. The results revealed that using GFRP as outer longitudinal bars led to peak loads 3–10% lower compared to columns with steel rebars. Inner confinement by steel spirals increased the load‐carrying capacity. Additionally, columns with inner tubular steel exhibited greater strength than those with steel spirals, indicating a slightly enhanced confinement effect. A finite element model was developed to analyze structural behavior, considering both material and geometric nonlinearity. The model's accuracy was validated by comparing predictions with test results. Parametric analysis from the nonlinear FE model showed that eccentricity significantly impacted column load‐carrying capacity. Increasing inner confinement area and the number of inner longitudinal bars improved structural stiffness and load‐carrying capacity. Furthermore, a simplified theoretical method was proposed. Comparison between experimental failure loads and theoretical predictions revealed differences within 20%, indicating satisfactory reliability of the proposed method.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"17 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204004","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 presents the experimental results of six full‐scale one‐way reinforced concrete slabs with variations in reinforcement detailing. Test specimens consisted of two reference concrete slabs reinforced fully with glass fiber reinforced polymer (GFRP) rebars or with steel rebars and four hybrid‐reinforced slabs. The variables included the arrangement of rebars, mechanical reinforcing ratio, and the ratio of steel rebar area to GFRP rebar area. The fabricated specimens were subjected to four‐point loading until failure in the strong floor laboratory. Experimental results indicated that hybrid reinforcement enhances stiffness compared to FRP reinforcement and provides a higher load‐bearing capacity than steel reinforcement. Also, it was observed that FRP bars placed as tensile reinforcement, similar in number and diameter size to steel bars placed as compressive reinforcement in a slab result in the highest ultimate capacity. Moreover, it was observed that while the mechanical reinforcing ratio contributes to the overall behavior of hybrid‐reinforced concrete slabs, the ratio of steel rebar area to GFRP rebar area is not considerably effective. Furthermore, image processing was employed to determine the exact crack widths of specimens after failure. Finally, finite element modeling results showed good agreement with the experimental results.
{"title":"Experimental, theoretical and numerical study on flexural behavior of hybrid steel‐GFRP reinforced concrete slabs","authors":"Zeinab Meghdadi, Alireza Khaloo","doi":"10.1002/suco.202301085","DOIUrl":"https://doi.org/10.1002/suco.202301085","url":null,"abstract":"This paper presents the experimental results of six full‐scale one‐way reinforced concrete slabs with variations in reinforcement detailing. Test specimens consisted of two reference concrete slabs reinforced fully with glass fiber reinforced polymer (GFRP) rebars or with steel rebars and four hybrid‐reinforced slabs. The variables included the arrangement of rebars, mechanical reinforcing ratio, and the ratio of steel rebar area to GFRP rebar area. The fabricated specimens were subjected to four‐point loading until failure in the strong floor laboratory. Experimental results indicated that hybrid reinforcement enhances stiffness compared to FRP reinforcement and provides a higher load‐bearing capacity than steel reinforcement. Also, it was observed that FRP bars placed as tensile reinforcement, similar in number and diameter size to steel bars placed as compressive reinforcement in a slab result in the highest ultimate capacity. Moreover, it was observed that while the mechanical reinforcing ratio contributes to the overall behavior of hybrid‐reinforced concrete slabs, the ratio of steel rebar area to GFRP rebar area is not considerably effective. Furthermore, image processing was employed to determine the exact crack widths of specimens after failure. Finally, finite element modeling results showed good agreement with the experimental results.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"40 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204005","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 modern construction, one of the most important factors in the execution of contracts is time. Standard procedures for assessing the frost resistance or concrete are usually very time‐consuming and can take up to 40 days. The current paper is experimentally and practically oriented. It presents an alternative testing method, based on air void network, that allows to assess the frost resistance of concrete within just a few days of taking the samples. X‐ray micro‐CT scans were introduced to obtain the quantitative and qualitative 3D information about the air void microstructure taking into account total air content: A (%), pores of the size below 300 μm in diameter content: A300 (%), specific surface of air voids: α (mm−1) and spacing factor: L (mm) to predict the freeze/thaw durability. To verify the assumptions of the frost resistance method, based on the analysis of pore microstructure, tests of freeze/thaw resistance in accordance with Polish supplement to European Standard were carried out. Presented research revealed that the appropriate microstructure of air pores, in particular, content of micropores with the diameter less than 0.3 mm: A300 combined with a spacing factor: L (mm) can constitute a reliable basis for determining concrete freeze/thaw durability. Thus, the method proposed in the current paper can be effectively used for fast and trustworthy determination of the air‐entrained concrete durability in a short time and without any special preparation of the tested sample that allows immediate preventive or repair actions to be taken if required.
{"title":"Method for prediction of the frost resistance ability of air‐entrained concrete based on the 3D air void characteristics by x‐ray micro‐CT","authors":"Łukasz Skarżyński, Mikołaj Miśkiewicz","doi":"10.1002/suco.202400309","DOIUrl":"https://doi.org/10.1002/suco.202400309","url":null,"abstract":"In modern construction, one of the most important factors in the execution of contracts is time. Standard procedures for assessing the frost resistance or concrete are usually very time‐consuming and can take up to 40 days. The current paper is experimentally and practically oriented. It presents an alternative testing method, based on air void network, that allows to assess the frost resistance of concrete within just a few days of taking the samples. X‐ray micro‐CT scans were introduced to obtain the quantitative and qualitative 3D information about the air void microstructure taking into account total air content: <jats:italic>A</jats:italic> (%), pores of the size below 300 μm in diameter content: <jats:italic>A</jats:italic><jats:sub>300</jats:sub> (%), specific surface of air voids: <jats:italic>α</jats:italic> (mm<jats:sup>−1</jats:sup>) and spacing factor: <jats:italic>L</jats:italic> (mm) to predict the freeze/thaw durability. To verify the assumptions of the frost resistance method, based on the analysis of pore microstructure, tests of freeze/thaw resistance in accordance with Polish supplement to European Standard were carried out. Presented research revealed that the appropriate microstructure of air pores, in particular, content of micropores with the diameter less than 0.3 mm: <jats:italic>A</jats:italic><jats:sub>300</jats:sub> combined with a spacing factor: <jats:italic>L</jats:italic> (mm) can constitute a reliable basis for determining concrete freeze/thaw durability. Thus, the method proposed in the current paper can be effectively used for fast and trustworthy determination of the air‐entrained concrete durability in a short time and without any special preparation of the tested sample that allows immediate preventive or repair actions to be taken if required.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"6 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204006","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}
Extrusion tests were conducted on recycled coarse aggregate concrete with circular steel tubes (RCCST, 100% replacement of recycled coarse aggregate) to investigate the impact of freeze–thaw cycles on bond properties. RCCST samples were subjected to 0, 25, 50, 75, 100, 125 and 150 freeze–thaw cycles and their bond properties were then compared with those of natural coarse aggregate concrete with circular steel tubes (NCCST) after 0, 100 and 150 freeze–thaw cycles. The experimental results indicate that freeze–thaw cycling damages the internal structure of RCCST, causing a significant decrease in interfacial bond strength with an increase in the number of freeze–thaw cycles. Freeze–thaw RCCST exhibits lower peak load and higher peak slip compared to NCCST, with increases of 25.2%, 73.2%, and 70.3% after 0, 100, and 150 freeze–thaw cycles, respectively. Regression analysis was used to derive an exponential equation that describes the relationship between longitudinal strain and strain gauge position. Additionally, a segmented fitting method was employed to obtain an expression for the bond slip of the freeze–thaw RCCST with a circular steel pipe.
{"title":"Experimental study on bond performance of recycled coarse aggregates concrete with circular steel tubes after freeze–thaw cycling","authors":"Dongxia Hu, Jin Wu, Zhe Feng, Liqiang Liu","doi":"10.1002/suco.202400110","DOIUrl":"https://doi.org/10.1002/suco.202400110","url":null,"abstract":"Extrusion tests were conducted on recycled coarse aggregate concrete with circular steel tubes (RCCST, 100% replacement of recycled coarse aggregate) to investigate the impact of freeze–thaw cycles on bond properties. RCCST samples were subjected to 0, 25, 50, 75, 100, 125 and 150 freeze–thaw cycles and their bond properties were then compared with those of natural coarse aggregate concrete with circular steel tubes (NCCST) after 0, 100 and 150 freeze–thaw cycles. The experimental results indicate that freeze–thaw cycling damages the internal structure of RCCST, causing a significant decrease in interfacial bond strength with an increase in the number of freeze–thaw cycles. Freeze–thaw RCCST exhibits lower peak load and higher peak slip compared to NCCST, with increases of 25.2%, 73.2%, and 70.3% after 0, 100, and 150 freeze–thaw cycles, respectively. Regression analysis was used to derive an exponential equation that describes the relationship between longitudinal strain and strain gauge position. Additionally, a segmented fitting method was employed to obtain an expression for the bond slip of the freeze–thaw RCCST with a circular steel pipe.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"12 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204010","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}
Weichen Xue, Qian Huang, Zhijun Xu, Jiayin Yu, Ya Li
The out‐of‐plane response of prefabricated (precast) concrete shear walls (PWs) are usually neglected in the structural designs. However, because of the relatively low stiffness and inevitable deformation of slabs, the out‐of‐plane behavior of PWs could influence the in‐plane response by causing premature failure or stability problems and affect the overall structural performance. This issue becomes significant when single‐row connections are employed because the neutral axial is shifted toward the compression side and the out‐of‐plane capacity is altered accordingly. In this study, PWs with grouted steel sleeve splices were tested under reciprocating cyclic loading. Both single‐row and paired connections were considered in test program. It was shown that all PWs suffered bending failure dominated by yielding of reinforcement at the bottom, and their load‐carrying capacity, stiffness degeneration trends were similar to the monolithic (cast‐in‐place) reference walls. Under the normalized compression of 0.12, the ductility of the prefabricated walls was 2.62 and 3.07, which was comparable to that of the reference cast‐in‐place wall (2.72). For the case that axial compression was not applied, the hysteresis curve of the PW with single‐row connection exhibited significant pinching. Nonetheless, the load‐carrying capacity of these walls did not exhibit significant drop at the end of the tests due to the lower axial compression, exhibiting high level of deformability. For both load cases, PWs with paired connection exhibited higher energy dissipation than the single‐row connected specimens.
{"title":"Out‐of‐plane response of prefabricated concrete shear walls connected via grouted sleeves","authors":"Weichen Xue, Qian Huang, Zhijun Xu, Jiayin Yu, Ya Li","doi":"10.1002/suco.202300619","DOIUrl":"https://doi.org/10.1002/suco.202300619","url":null,"abstract":"The out‐of‐plane response of prefabricated (precast) concrete shear walls (PWs) are usually neglected in the structural designs. However, because of the relatively low stiffness and inevitable deformation of slabs, the out‐of‐plane behavior of PWs could influence the in‐plane response by causing premature failure or stability problems and affect the overall structural performance. This issue becomes significant when single‐row connections are employed because the neutral axial is shifted toward the compression side and the out‐of‐plane capacity is altered accordingly. In this study, PWs with grouted steel sleeve splices were tested under reciprocating cyclic loading. Both single‐row and paired connections were considered in test program. It was shown that all PWs suffered bending failure dominated by yielding of reinforcement at the bottom, and their load‐carrying capacity, stiffness degeneration trends were similar to the monolithic (cast‐in‐place) reference walls. Under the normalized compression of 0.12, the ductility of the prefabricated walls was 2.62 and 3.07, which was comparable to that of the reference cast‐in‐place wall (2.72). For the case that axial compression was not applied, the hysteresis curve of the PW with single‐row connection exhibited significant pinching. Nonetheless, the load‐carrying capacity of these walls did not exhibit significant drop at the end of the tests due to the lower axial compression, exhibiting high level of deformability. For both load cases, PWs with paired connection exhibited higher energy dissipation than the single‐row connected specimens.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"12 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204011","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}
The shear wall system with cast‐in situ concrete infilled walls has been widely used in high‐rise buildings due to its significant advantages in construction. In this paper, quasi‐static tests were conducted on the shear walls with and without cast‐in situ concrete infilled walls to analyze their failure modes, load‐bearing capacity, stiffness, energy dissipation capacity, and ductility. A simplified model of the shear wall with cast‐in situ concrete infilled walls was proposed based on the fiber element model in OpenSees. The test results showed that the shear wall specimens with cast‐in situ concrete infilled walls exhibited full‐section compression or tension failure, and the cast‐in situ concrete infilled walls did not show obvious damage. Compared with the shear wall without infilled walls, the overall stiffness, load bearing capacity, and energy dissipation capacity of the shear wall specimens with cast‐in situ concrete infilled walls improved, indicating better seismic performance than those without infilled walls. Comparison between the hysteresis and skeleton curves derived from the tests and those simulated by the proposed simplified model revealed errors within 15% for stiffness, yield bearing capacity, and ultimate bearing capacity for shear walls with cast‐in situ concrete infill walls, affirming the effectiveness and accuracy of the model.
{"title":"Experimental and numerical study on seismic behavior of shear wall with cast‐in situ concrete infilled walls","authors":"Bo Zhou, Qi Si, Bing Li, Liang Zong, Songlin Li","doi":"10.1002/suco.202400330","DOIUrl":"https://doi.org/10.1002/suco.202400330","url":null,"abstract":"The shear wall system with cast‐in situ concrete infilled walls has been widely used in high‐rise buildings due to its significant advantages in construction. In this paper, quasi‐static tests were conducted on the shear walls with and without cast‐in situ concrete infilled walls to analyze their failure modes, load‐bearing capacity, stiffness, energy dissipation capacity, and ductility. A simplified model of the shear wall with cast‐in situ concrete infilled walls was proposed based on the fiber element model in OpenSees. The test results showed that the shear wall specimens with cast‐in situ concrete infilled walls exhibited full‐section compression or tension failure, and the cast‐in situ concrete infilled walls did not show obvious damage. Compared with the shear wall without infilled walls, the overall stiffness, load bearing capacity, and energy dissipation capacity of the shear wall specimens with cast‐in situ concrete infilled walls improved, indicating better seismic performance than those without infilled walls. Comparison between the hysteresis and skeleton curves derived from the tests and those simulated by the proposed simplified model revealed errors within 15% for stiffness, yield bearing capacity, and ultimate bearing capacity for shear walls with cast‐in situ concrete infill walls, affirming the effectiveness and accuracy of the model.","PeriodicalId":21988,"journal":{"name":"Structural Concrete","volume":"56 1","pages":""},"PeriodicalIF":3.2,"publicationDate":"2024-08-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142204012","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}
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