Four concrete columns using prestressing strand as transverse reinforcement were tested to establish design parameters for the use of high-strength transverse reinforcement under seismic loading. Two tests were dynamic. The confinement of flexural hinges was satisfactory at reinforcement levels below that called for by code, provided that the spiral pitch was small enough to prevent buckling of the longitudinal reinforcement. Dynamic loading did not have any unanticipated effect on flexural performance.
{"title":"Flexural Confinement of Plastic Hinges in Circular Bridge Columns Using Unstressed Prestressing Strand as Transverse Reinforcement","authors":"A. Budek, M. Priestley, Chin Ok Lee","doi":"10.14359/18285","DOIUrl":"https://doi.org/10.14359/18285","url":null,"abstract":"Four concrete columns using prestressing strand as transverse reinforcement were tested to establish design parameters for the use of high-strength transverse reinforcement under seismic loading. Two tests were dynamic. The confinement of flexural hinges was satisfactory at reinforcement levels below that called for by code, provided that the spiral pitch was small enough to prevent buckling of the longitudinal reinforcement. Dynamic loading did not have any unanticipated effect on flexural performance.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128938547","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 performance-based seismic design, evaluation of the deformation capacity of reinforced concrete columns is of paramount importance. The deformation capacity of a column can be expressed in several different ways: (1) curvature ductility, (2) displacement ductility, or (3) drift. Even though several performance-based confining reinforcement design procedures have been proposed, the relationship between different ductility factors is not clearly understood. The effect of concrete strength, longitudinal reinforcement ratio, volumetric ratio of confining reinforcement, shear span-to-depth ratio, and axial load level on the relationship between different ductility factors was studied. Finally, the confinement reinforcement design requirements of current design codes and recently proposed performance-based design methods were compared and critically examined.
{"title":"Performance-Based Design of Confining Reinforcement: Research and Seismic Design Provisions","authors":"S. Bae, O. Bayrak","doi":"10.14359/18263","DOIUrl":"https://doi.org/10.14359/18263","url":null,"abstract":"In performance-based seismic design, evaluation of the deformation capacity of reinforced concrete columns is of paramount importance. The deformation capacity of a column can be expressed in several different ways: (1) curvature ductility, (2) displacement ductility, or (3) drift. Even though several performance-based confining reinforcement design procedures have been proposed, the relationship between different ductility factors is not clearly understood. The effect of concrete strength, longitudinal reinforcement ratio, volumetric ratio of confining reinforcement, shear span-to-depth ratio, and axial load level on the relationship between different ductility factors was studied. Finally, the confinement reinforcement design requirements of current design codes and recently proposed performance-based design methods were compared and critically examined.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125325237","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The use of high-strength concrete (HSC) tied columns is becoming increasingly popular in engineering practice. Researchers are working to obtain the proper post-peak behavior of tied columns with concrete strength greater than 60 MPa. Many empirical confinement models have been reported in the literature for the prediction of stress-strain behavior under concentric loading. However, nothing significant has been said about the numerical modeling of the problems wherein the nonlinear response of HSC tied columns may be reasonably predicted. In the present study, the nonlinear behavior of concrete material has been idealized by William-Warnke five-parameter model, which, to date, is the most widely accepted and sophisticated criterion. Within the framework of rate independent associative elasto-plasticity, a full backward Euler integration algorithm for stress updating has been implemented in the present work. A fixed crack smeared approach based upon fracture energy concept and non-local material softening law has been employed for the tensile modeling of concrete material. The computational model also involves the provision for cover spalling. A couple of examples have also been presented for validation of the numerical methodology proposed in this work.
{"title":"Three-Dimensional Finite Element Modeling of Confined High-Strength Concrete Columns","authors":"P. Bhargava, R. Bhowmick, U. Sharma, S. Kaushik","doi":"10.14359/18276","DOIUrl":"https://doi.org/10.14359/18276","url":null,"abstract":"The use of high-strength concrete (HSC) tied columns is becoming increasingly popular in engineering practice. Researchers are working to obtain the proper post-peak behavior of tied columns with concrete strength greater than 60 MPa. Many empirical confinement models have been reported in the literature for the prediction of stress-strain behavior under concentric loading. However, nothing significant has been said about the numerical modeling of the problems wherein the nonlinear response of HSC tied columns may be reasonably predicted. In the present study, the nonlinear behavior of concrete material has been idealized by William-Warnke five-parameter model, which, to date, is the most widely accepted and sophisticated criterion. Within the framework of rate independent associative elasto-plasticity, a full backward Euler integration algorithm for stress updating has been implemented in the present work. A fixed crack smeared approach based upon fracture energy concept and non-local material softening law has been employed for the tensile modeling of concrete material. The computational model also involves the provision for cover spalling. A couple of examples have also been presented for validation of the numerical methodology proposed in this work.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124484430","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 describes a series of tests on concrete cylinders confined by carbon fiber jackets. The primary variables in the investigation were the thickness of the jackets (and therefore the lateral confinement stress), the size of the cylinders, the loading speed, and the loading type (monotonic vs. cyclic) and the jacket type (individual layers or continuous wrap). Of these parameters, the lateral confining stress was found to have the greatest influence, but the coefficient for the concrete used was found to be slightly lower than the 4.1 that is implicit in ACI318-02. The cylinder size, the loading speed and the cyclic loading regimes were found to have essentially no influence on stress and strain at failure. The continuously wound jackets were found to initiate failure by delamination, rather than fracture of the fiber, and to lower the stress and strain at failure.
{"title":"The Influence of Concrete Strength and Confinement Type on the Response of FRP-Confined Concrete Cylinders","authors":"J. Stanton, L. Owen","doi":"10.14359/18281","DOIUrl":"https://doi.org/10.14359/18281","url":null,"abstract":"This paper describes a series of tests on concrete cylinders confined by carbon fiber jackets. The primary variables in the investigation were the thickness of the jackets (and therefore the lateral confinement stress), the size of the cylinders, the loading speed, and the loading type (monotonic vs. cyclic) and the jacket type (individual layers or continuous wrap). Of these parameters, the lateral confining stress was found to have the greatest influence, but the coefficient for the concrete used was found to be slightly lower than the 4.1 that is implicit in ACI318-02. The cylinder size, the loading speed and the cyclic loading regimes were found to have essentially no influence on stress and strain at failure. The continuously wound jackets were found to initiate failure by delamination, rather than fracture of the fiber, and to lower the stress and strain at failure.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130725677","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 order to investigate the seismic behavior of existing reinforced concrete (R/C) rectangular columns which are strengthened by circular steel jackets, a total of twenty column specimens with and without strengthening were designed, constructed, and were tested under three different constant axial-stresses of 5.6, 13.2 and 19.4 MPa, and alternately repeated lateral forces. Test results of retrofitted columns with circular steel jackets are compared with those obtained from the column specimens with and without rectangular steel- and CF sheet-jackets, and circular CF sheet jackets. One of the main conclusions is that the ultimate flexural strengths and deformation capacity of the R/C rectangular columns which are confined laterally by the circular steel- and CF sheet-jacketing are quite effective, especially in case of the columns under high axial-compression.
{"title":"Seismic Retrofit for R/C Rectangular Columns by Circular Steel Jackets","authors":"Jun Wang, K. Yoshimura, K. Kikuchi, M. Kuroki","doi":"10.14359/18279","DOIUrl":"https://doi.org/10.14359/18279","url":null,"abstract":"In order to investigate the seismic behavior of existing reinforced concrete (R/C) rectangular columns which are strengthened by circular steel jackets, a total of twenty column specimens with and without strengthening were designed, constructed, and were tested under three different constant axial-stresses of 5.6, 13.2 and 19.4 MPa, and alternately repeated lateral forces. Test results of retrofitted columns with circular steel jackets are compared with those obtained from the column specimens with and without rectangular steel- and CF sheet-jackets, and circular CF sheet jackets. One of the main conclusions is that the ultimate flexural strengths and deformation capacity of the R/C rectangular columns which are confined laterally by the circular steel- and CF sheet-jacketing are quite effective, especially in case of the columns under high axial-compression.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116186716","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, an analytical stress-strain model of confined concrete columns is developed and presented. The model is based on the extensively obtained data from tests of column specimens subjected to concentric compression loading. The tests included a wide range of varieties including both normal and high-strength concretes. The cross sections of the columns were of circular, rectangular, or elliptical shapes. The model incorporates the effective relevant parameters of confinement like concrete strength, yield strength of transverse reinforcement, spacing between lateral confining element, and dimensional configuration of column specimen and its transverse reinforcement. The model can be used for concrete confined by spirals, rectilinear hoops, crossties, and combinations of these reinforcements. The model demonstrates good predictive capability for concrete columns of compressive strength ranging from 20 MPa to 120 MPa. In addition, the model is shown to be applicable for a wide range of quantity and configuration of lateral reinforcement with volumetric ratio to concrete from 0.2% to 4%.
{"title":"Modeling the Stress-Strain Behavior of Confined Concrete Columns","authors":"K. El-Dash, O. El-Mahdy","doi":"10.14359/18271","DOIUrl":"https://doi.org/10.14359/18271","url":null,"abstract":"In this paper, an analytical stress-strain model of confined concrete columns is developed and presented. The model is based on the extensively obtained data from tests of column specimens subjected to concentric compression loading. The tests included a wide range of varieties including both normal and high-strength concretes. The cross sections of the columns were of circular, rectangular, or elliptical shapes. The model incorporates the effective relevant parameters of confinement like concrete strength, yield strength of transverse reinforcement, spacing between lateral confining element, and dimensional configuration of column specimen and its transverse reinforcement. The model can be used for concrete confined by spirals, rectilinear hoops, crossties, and combinations of these reinforcements. The model demonstrates good predictive capability for concrete columns of compressive strength ranging from 20 MPa to 120 MPa. In addition, the model is shown to be applicable for a wide range of quantity and configuration of lateral reinforcement with volumetric ratio to concrete from 0.2% to 4%.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"128 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126156787","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}
A key of seismic design of ductile frame is to provide the adequate flexural ductility to potential plastic hinge regions. This is realized by limiting the amount of tension reinforcement index, providing transverse reinforcement and others. For columns, the application of transverse reinforcement to potential plastic hinge region is essential, that is, the compressive ductility of concrete is improved and results in larger flexural ductility. In the 1980s, a new reinforced concrete (RC) project was carried out as a Japanese National Project to establish the design and construction guidelines for high-rise buildings, up to 200 meters high. For columns at the lower part of high-rise buildings, the use of high-strength (HSC) concrete is required. However, HSC fails in brittle manner and results in small flexural ductility of potential plastic hinges. Therefore the new RC project gave an opportunity to re-recognize the importance of lateral confinement to concrete. This paper presents the recent research works on confined concrete in Japan, mainly for HSC. Some experimental works and idealizations of stress-strain curve of confined concrete are introduced. Maximum compressive strength covered in this paper is 176 MPa.
{"title":"Research Activities on Confined Concrete in Japan","authors":"F. Watanabe","doi":"10.14359/18264","DOIUrl":"https://doi.org/10.14359/18264","url":null,"abstract":"A key of seismic design of ductile frame is to provide the adequate flexural ductility to potential plastic hinge regions. This is realized by limiting the amount of tension reinforcement index, providing transverse reinforcement and others. For columns, the application of transverse reinforcement to potential plastic hinge region is essential, that is, the compressive ductility of concrete is improved and results in larger flexural ductility. In the 1980s, a new reinforced concrete (RC) project was carried out as a Japanese National Project to establish the design and construction guidelines for high-rise buildings, up to 200 meters high. For columns at the lower part of high-rise buildings, the use of high-strength (HSC) concrete is required. However, HSC fails in brittle manner and results in small flexural ductility of potential plastic hinges. Therefore the new RC project gave an opportunity to re-recognize the importance of lateral confinement to concrete. This paper presents the recent research works on confined concrete in Japan, mainly for HSC. Some experimental works and idealizations of stress-strain curve of confined concrete are introduced. Maximum compressive strength covered in this paper is 176 MPa.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133040203","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 order to evaluate the load carrying capacity and ductility of hinging zone of the concrete filled steel tubular (CFT) columns, tests are carried out on 12 circular specimens and 18 square specimens subjected to uniform bending under a constant axial load. The experimental parameters are: 1) depth to thickness ratio (D/t ratio) and width to thickness ratio (B/t ratio) of steel tube; 2) axial load ratio; 3) material strength; 4) deformation history; and 5) annealing. One of the features of the test is the wide range of D/t and B/t ratio. The range of D/t ratio of the circular CFT columns is 40.5-160 and the range of B/t ratio of the square CFT columns is 32.8-98.0, respectively. The experimental load-deformation relations are compared with those of the elasto-plastic analysis based on the supposed stress-strain relationships established for the filled concrete and for the steel tube. The analytical results show good agreement with the test results for all specimens. This implies that the proposed stress-strain relationships for CFT columns are useful to predict the characteristics of the filled concrete and the steel tube.
{"title":"Hysteretic Behavior of Concrete-Filled Steel Tubular Columns under Uniform Bending","authors":"H. Nakahara, K. Sakino","doi":"10.14359/18278","DOIUrl":"https://doi.org/10.14359/18278","url":null,"abstract":"In order to evaluate the load carrying capacity and ductility of hinging zone of the concrete filled steel tubular (CFT) columns, tests are carried out on 12 circular specimens and 18 square specimens subjected to uniform bending under a constant axial load. The experimental parameters are: 1) depth to thickness ratio (D/t ratio) and width to thickness ratio (B/t ratio) of steel tube; 2) axial load ratio; 3) material strength; 4) deformation history; and 5) annealing. One of the features of the test is the wide range of D/t and B/t ratio. The range of D/t ratio of the circular CFT columns is 40.5-160 and the range of B/t ratio of the square CFT columns is 32.8-98.0, respectively. The experimental load-deformation relations are compared with those of the elasto-plastic analysis based on the supposed stress-strain relationships established for the filled concrete and for the steel tube. The analytical results show good agreement with the test results for all specimens. This implies that the proposed stress-strain relationships for CFT columns are useful to predict the characteristics of the filled concrete and the steel tube.","PeriodicalId":104265,"journal":{"name":"SP-238: International Symposium on Confined Concrete","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124340494","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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