{"title":"Effective Moment of Inertia of Concrete Beams Prestressed with Aramid Fiber-Reinforced Polymer (AFRP) Tendons","authors":"Y. Kim","doi":"10.14359/51663265","DOIUrl":"https://doi.org/10.14359/51663265","url":null,"abstract":"","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"65 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114228016","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}
This paper will discuss how serviceability related to deflections and cracking often controls design of fiber reinforced polymer (FRP) reinforced concrete. The existing approach prescribed in ACI 318 for computing deflection of steel reinforced concrete overestimates member stiffness when FRP is used as the reinforcement. Deflection is then underestimated. Numerous proposals have consequently been made for computing deflection of FRP reinforced concrete, and have mostly involved modifications to Branson’s original ACI expression for the effective moment of inertia Ie. This paper reviews the different procedures used in the past by ACI Committee 440 to compute deflection of FRP reinforced concrete members, and discusses deficiencies of past and present ACI 440.1R deflection calculation guidelines. A case is made for the need to adopt a more rational approach to compute deflection and the basis for proposed changes are reviewed and explained in detail. A statistical comparison of past, present, and proposed approaches for computing deflection are compared with an experimental database that justifies the need for a more rational approach to computing deflection. The paper ends with a clear set of deflection procedures for carrying out serviceability design of FRP reinforced concrete.
{"title":"The Story Behind Proposed Changes to ACI 440 Deflection Requirements for FRP-Reinforced Concrete","authors":"P. Bischoff, S. Gross, C. E. Ospina","doi":"10.14359/51663260","DOIUrl":"https://doi.org/10.14359/51663260","url":null,"abstract":"This paper will discuss how serviceability related to deflections and cracking often controls design of fiber reinforced polymer (FRP) reinforced concrete. The existing approach prescribed in ACI 318 for computing deflection of steel reinforced concrete overestimates member stiffness when FRP is used as the reinforcement. Deflection is then underestimated. Numerous proposals have consequently been made for computing deflection of FRP reinforced concrete, and have mostly involved modifications to Branson’s original ACI expression for the effective moment of inertia Ie. This paper reviews the different procedures used in the past by ACI Committee 440 to compute deflection of FRP reinforced concrete members, and discusses deficiencies of past and present ACI 440.1R deflection calculation guidelines. A case is made for the need to adopt a more rational approach to compute deflection and the basis for proposed changes are reviewed and explained in detail. A statistical comparison of past, present, and proposed approaches for computing deflection are compared with an experimental database that justifies the need for a more rational approach to computing deflection. The paper ends with a clear set of deflection procedures for carrying out serviceability design of FRP reinforced concrete.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128345960","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}
{"title":"Deflection Control of Reinforced Concrete Beams and One-Way Slabs with Externally Bonded FRP","authors":"C. E. Ospina","doi":"10.14359/51663264","DOIUrl":"https://doi.org/10.14359/51663264","url":null,"abstract":"","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128793344","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}
This paper will discuss an experimental study that was conducted to evaluate the increase in crack width occurring over time in fiber reinforced polymer (FRP) reinforced concrete as a result of sustained loading. Twelve beams (eight GFRP, two CFRP, and two steel-reinforced) were maintained under a constant sustained service load for nearly three years. Three flexural cracks were monitored on each beam over the duration of the test. The observed increase in flexural crack widths over the study was greater in the FRP-reinforced specimens than in the steel-reinforced specimens. On average, flexural crack widths in FRP-reinforced concrete specimens were observed to double over one year of sustained loading. A simple design approach, based on modification to the existing ACI 440 (2006) crack control procedure, is proposed to account for this observed increase in crack widths with time.
{"title":"Effect of Sustained Loads on Flexural Crack Width in Concrete Beams Reinforced with Internal FRP Reinforcement","authors":"S. Gross, J. Yost, D. J. Stefanski","doi":"10.14359/51663258","DOIUrl":"https://doi.org/10.14359/51663258","url":null,"abstract":"This paper will discuss an experimental study that was conducted to evaluate the increase in crack width occurring over time in fiber reinforced polymer (FRP) reinforced concrete as a result of sustained loading. Twelve beams (eight GFRP, two CFRP, and two steel-reinforced) were maintained under a constant sustained service load for nearly three years. Three flexural cracks were monitored on each beam over the duration of the test. The observed increase in flexural crack widths over the study was greater in the FRP-reinforced specimens than in the steel-reinforced specimens. On average, flexural crack widths in FRP-reinforced concrete specimens were observed to double over one year of sustained loading. A simple design approach, based on modification to the existing ACI 440 (2006) crack control procedure, is proposed to account for this observed increase in crack widths with time.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122328629","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}
This paper will discuss that due to concerns with corrosion, the use of fiber reinforced polymer (FRP) as a replacement to conventional steel reinforcement has greatly increased over the last decade. However, elastic modulus values of some commercially available FRP reinforcement hardly reach 20% of that for conventional steel. Existing code relationships for conventional steel have been modified to address this proprietary difference but the modifications are restricted by the empirical nature of the expressions. This paper provides an alternate approach to estimate the deflection of concrete beams by considering effects of tension stiffening that incorporate material properties of the reinforcement as well as the effects of concrete non-linearity in compression. A database containing experimental load-deflection records from 139 glass FRP (GFRP) and 48 carbon FRP (CFRP) reinforced concrete beams was used to calibrate a tension stiffening model for the proposed approach and establish its accuracy as well as precision through statistical analysis. Results were compared to those obtained from existing relationships and indicate that the revised approach provides higher accuracy at service conditions ranging from 25% to 80% of ultimate.
{"title":"Effective Moment of Inertia Expression for Concrete Beams Reinforced with Fiber-Reinforced Polymer (FRP)","authors":"H. Vogel, D. Svecova","doi":"10.14359/51663261","DOIUrl":"https://doi.org/10.14359/51663261","url":null,"abstract":"This paper will discuss that due to concerns with corrosion, the use of fiber reinforced polymer (FRP) as a replacement to conventional steel reinforcement has greatly increased over the last decade. However, elastic modulus values of some commercially available FRP reinforcement hardly reach 20% of that for conventional steel. Existing code relationships for conventional steel have been modified to address this proprietary difference but the modifications are restricted by the empirical nature of the expressions. This paper provides an alternate approach to estimate the deflection of concrete beams by considering effects of tension stiffening that incorporate material properties of the reinforcement as well as the effects of concrete non-linearity in compression. A database containing experimental load-deflection records from 139 glass FRP (GFRP) and 48 carbon FRP (CFRP) reinforced concrete beams was used to calibrate a tension stiffening model for the proposed approach and establish its accuracy as well as precision through statistical analysis. Results were compared to those obtained from existing relationships and indicate that the revised approach provides higher accuracy at service conditions ranging from 25% to 80% of ultimate.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"110 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132783116","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}
Synopsis: Design for deflection control is a critical part of the design of FRP reinforced members due to the relatively low modulus of elasticity and elastic-brittle nature of FRP reinforcement. This paper provides an overview of design for deflection control including a brief review of the basic mechanics of beam flexure and a review of methods to account for cracking, tension stiffening, shrinkage and creep. The basis for selecting appropriate deflection control criteria is also discussed and a framework is presented to incorporate deflection control into the overall design process.
{"title":"Deflection Control for FRP-Reinforced Concrete Members: An Overview","authors":"A. Scanlon","doi":"10.14359/51663257","DOIUrl":"https://doi.org/10.14359/51663257","url":null,"abstract":"Synopsis: Design for deflection control is a critical part of the design of FRP reinforced members due to the relatively low modulus of elasticity and elastic-brittle nature of FRP reinforcement. This paper provides an overview of design for deflection control including a brief review of the basic mechanics of beam flexure and a review of methods to account for cracking, tension stiffening, shrinkage and creep. The basis for selecting appropriate deflection control criteria is also discussed and a framework is presented to incorporate deflection control into the overall design process.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133662627","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}
This paper will discuss how the use of externally bonded FRP plates and sheets has been established as an effective mean to strengthen concrete beams in flexure and shear. Several investigators have shown that the direct use of Branson equation does not yield conservative deflection results especially after steel yielding. The authors have developed an analytical solution that generates closed form expressions for deflection in simple beams. These expressions were shown to reproduce results that compared well with experiments. These expressions were dependent on the loading condition while Branson equation is not load specific. Branson equation is modified by replacing the cracked section moment of inertia with an effective moment of inertia at steel yielding to evaluate deflections at the service load levels. This revised formula could be easily implemented in the ACI 440.2R format. The predictions are compared against Branson equation and experimental evidence. Furthermore, another new modification to Branson equation is proposed for the region covering response from steel yielding and up to ultimate capacity.
{"title":"Modified Branson’s Formula for Deflection of FRP Strengthened Concrete Beams","authors":"H. Rasheed, H. Charkas","doi":"10.14359/51663263","DOIUrl":"https://doi.org/10.14359/51663263","url":null,"abstract":"This paper will discuss how the use of externally bonded FRP plates and sheets has been established as an effective mean to strengthen concrete beams in flexure and shear. Several investigators have shown that the direct use of Branson equation does not yield conservative deflection results especially after steel yielding. The authors have developed an analytical solution that generates closed form expressions for deflection in simple beams. These expressions were shown to reproduce results that compared well with experiments. These expressions were dependent on the loading condition while Branson equation is not load specific. Branson equation is modified by replacing the cracked section moment of inertia with an effective moment of inertia at steel yielding to evaluate deflections at the service load levels. This revised formula could be easily implemented in the ACI 440.2R format. The predictions are compared against Branson equation and experimental evidence. Furthermore, another new modification to Branson equation is proposed for the region covering response from steel yielding and up to ultimate capacity.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134320650","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}
This paper will discuss that in order to understand and predict the effect of externally bonded reinforcement (EBR) on the serviceability behavior of FRP (fiber-reinforced polymer) strengthened members, four-point bending tests have been executed on reinforced concrete (RC) beams with span length 3.8 m (150 in.). This experimental campaign was further complemented with tests on strengthened tensile members. These so-called ‘tension stiffening’ tests typically consist of a tensile test on a reinforcing bar embedded in a FRP strengthened concrete prism. As the FRP EBR increases the stiffness of the beams and as a denser crack pattern with smaller crack widths is obtained, the serviceability limit state (SLS) of the strengthened members is positively influenced. Hereby, the behavior in terms of deflection and crack widths can be predicted in a fairly accurate way.
本文将讨论为了了解和预测外粘结钢筋(EBR)对FRP(纤维增强聚合物)增强构件的使用性能的影响，对跨度为3.8 m (150 in.)的钢筋混凝土(RC)梁进行了四点弯曲试验。这一实验活动进一步补充了加强拉伸构件的试验。这些所谓的“拉力强化”测试通常包括对嵌入FRP增强混凝土棱镜的钢筋进行拉伸测试。FRP - EBR增加了梁的刚度，获得了更密集的裂缝模式和更小的裂缝宽度，对增强构件的使用极限状态(SLS)产生了积极的影响。因此，可以相当准确地预测挠度和裂缝宽度方面的行为。
{"title":"Deflection and Cracking Behavior of RC Beams Strengthened in Flexure","authors":"S. Matthys, L. Taerwe","doi":"10.14359/51663262","DOIUrl":"https://doi.org/10.14359/51663262","url":null,"abstract":"This paper will discuss that in order to understand and predict the effect of externally bonded reinforcement (EBR) on the serviceability behavior of FRP (fiber-reinforced polymer) strengthened members, four-point bending tests have been executed on reinforced concrete (RC) beams with span length 3.8 m (150 in.). This experimental campaign was further complemented with tests on strengthened tensile members. These so-called ‘tension stiffening’ tests typically consist of a tensile test on a reinforcing bar embedded in a FRP strengthened concrete prism. As the FRP EBR increases the stiffness of the beams and as a denser crack pattern with smaller crack widths is obtained, the serviceability limit state (SLS) of the strengthened members is positively influenced. Hereby, the behavior in terms of deflection and crack widths can be predicted in a fairly accurate way.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"93 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126349816","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}
In this paper a laboratory investigation on the flexural behavior of carbon fiber reinforced polymer (CFRP)-reinforced concrete slab specimens extracted from Laurier-Tache Parking Garage (National Capital Region - Canada) after being in service field conditions for about eight years (1997-2005) is described. A total of four specimens, measuring 3 m long × 1 m wide × 0.19 m deep each, are extracted from the parking garage and then tested in flexure under four-point bending set-up. In addition, five FRP bar samples are extracted from the slabs and tested in tension to evaluate the strength or stiffness degradation of the CFRP bars, if any. The test results are presented in terms of deflection, crack widths, strains in concrete and reinforcement, ultimate capacity, and mode of failure. Based on the test results, the current provisions, provided by different FRP codes and design guidelines, are evaluated. The results showed that the CFRP bars as well as the CFRP-reinforced concrete slabs have not been adversely affected after being in service for eight years.
{"title":"Cracking and Deflection Behavior of One-Way Parking Garage Slabs Reinforced with CFRP Bars","authors":"S. El-Gamal, B. Benmokrane, E. El-Salakawy","doi":"10.14359/51663259","DOIUrl":"https://doi.org/10.14359/51663259","url":null,"abstract":"In this paper a laboratory investigation on the flexural behavior of carbon fiber reinforced polymer (CFRP)-reinforced concrete slab specimens extracted from Laurier-Tache Parking Garage (National Capital Region - Canada) after being in service field conditions for about eight years (1997-2005) is described. A total of four specimens, measuring 3 m long × 1 m wide × 0.19 m deep each, are extracted from the parking garage and then tested in flexure under four-point bending set-up. In addition, five FRP bar samples are extracted from the slabs and tested in tension to evaluate the strength or stiffness degradation of the CFRP bars, if any. The test results are presented in terms of deflection, crack widths, strains in concrete and reinforcement, ultimate capacity, and mode of failure. Based on the test results, the current provisions, provided by different FRP codes and design guidelines, are evaluated. The results showed that the CFRP bars as well as the CFRP-reinforced concrete slabs have not been adversely affected after being in service for eight years.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"33 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130763037","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}
This paper will present an alternative approach to examine uncertainty in predicting deflections of fiber-reinforced polymer-reinforced concrete (FRP-RC) beams. The use of nonspecificity of concrete cracking as a measure of cracking variability is proposed. Non-specificity is a type of uncertainty associated with having multiple alternatives to define variables (e.g. modulus of rupture, tensile strength to describe cracking). Nonspecificity in cracking can be described by considering cracking strength interval. Using a cracking strength interval, deflection intervals of FRP-RC beams are calculated. Deflection is modeled using cracked plane frame analysis integrated with recent models describing concrete tension stiffening with fiber reinforced polymers (FRP) reinforcement. A deflection database of FRP-RC beams is developed and examined. The uncertainty in deflection prediction is evaluated by comparing the measured deflection from the database with respect to the predicted deflection interval. The significance of deflection prediction parameters on the uncertainty in predicting deflection of FRP-RC beams was analyzed. It is shown that when the applied moment to cracking moment ratio gets close to unity, the uncertainty in predicting deflection of concrete beams reinforced with FRP increases.
{"title":"Significance of Cracking Uncertainty on Predicting Deflection of FRC-RC Beams","authors":"Jung J. Kim, A. Said, M. Taha","doi":"10.14359/51663267","DOIUrl":"https://doi.org/10.14359/51663267","url":null,"abstract":"This paper will present an alternative approach to examine uncertainty in predicting deflections of fiber-reinforced polymer-reinforced concrete (FRP-RC) beams. The use of nonspecificity of concrete cracking as a measure of cracking variability is proposed. Non-specificity is a type of uncertainty associated with having multiple alternatives to define variables (e.g. modulus of rupture, tensile strength to describe cracking). Nonspecificity in cracking can be described by considering cracking strength interval. Using a cracking strength interval, deflection intervals of FRP-RC beams are calculated. Deflection is modeled using cracked plane frame analysis integrated with recent models describing concrete tension stiffening with fiber reinforced polymers (FRP) reinforcement. A deflection database of FRP-RC beams is developed and examined. The uncertainty in deflection prediction is evaluated by comparing the measured deflection from the database with respect to the predicted deflection interval. The significance of deflection prediction parameters on the uncertainty in predicting deflection of FRP-RC beams was analyzed. It is shown that when the applied moment to cracking moment ratio gets close to unity, the uncertainty in predicting deflection of concrete beams reinforced with FRP increases.","PeriodicalId":205144,"journal":{"name":"SP-264: Serviceability of Concrete Members Reinforced with Internal/External FRP Reinforcement","volume":"9 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134458023","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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