Cracking occurs in reinforced concrete members when principal tension stresses exceed the tensile strength of the concrete. This paper examines five types of cracking in concrete columns under compressive axial load caused by creep and shrinkage, by the cement heat of hydration, by ambient temperature changes and by unloading. Following types of cracks are considered: unloading cracks; cracks in thick columns under light loads; cracks in heavily reinforced columns; cracks from heat of hydration; and cracks from imposed displacements. The paper describes the causes of cracks, analyzes them and provides photos of cracked columns. Also provided are design and construction recommendations to prevent or reduce these cracks.
{"title":"Tension Cracking in Columns Under Compression Loads","authors":"D. J. Carreira","doi":"10.14359/14430","DOIUrl":"https://doi.org/10.14359/14430","url":null,"abstract":"Cracking occurs in reinforced concrete members when principal tension stresses exceed the tensile strength of the concrete. This paper examines five types of cracking in concrete columns under compressive axial load caused by creep and shrinkage, by the cement heat of hydration, by ambient temperature changes and by unloading. Following types of cracks are considered: unloading cracks; cracks in thick columns under light loads; cracks in heavily reinforced columns; cracks from heat of hydration; and cracks from imposed displacements. The paper describes the causes of cracks, analyzes them and provides photos of cracked columns. Also provided are design and construction recommendations to prevent or reduce these cracks.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"38 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114642956","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}
M. Pigeon, R. Bissonnette, J. Marchand, D. Boily, L. Barcelo
This paper presented results that indicated that the stress due to early age restrained autogenous shrinkage varies quite a lot, partly because of the variation in the relaxation capacity of the mixtures. Both the relaxation ratio, defined as the stress generated divided by the theoretical stress, and the relative relaxation, defined as the absolute value of stress relaxation divided by the average applied stress, can be used to illustrate and analyze the variation of the relaxation phenomena as a function of the type of mixture testes.
{"title":"Stress Relaxation of Concrete Under Autogenous Early-Age Restrained Shrinkage","authors":"M. Pigeon, R. Bissonnette, J. Marchand, D. Boily, L. Barcelo","doi":"10.14359/14438","DOIUrl":"https://doi.org/10.14359/14438","url":null,"abstract":"This paper presented results that indicated that the stress due to early age restrained autogenous shrinkage varies quite a lot, partly because of the variation in the relaxation capacity of the mixtures. Both the relaxation ratio, defined as the stress generated divided by the theoretical stress, and the relative relaxation, defined as the absolute value of stress relaxation divided by the average applied stress, can be used to illustrate and analyze the variation of the relaxation phenomena as a function of the type of mixture testes.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115768817","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 general approach of creep analysis of structures based on the linear theory of viscoelasticity and on extended use of the four fundamental theorems leads to very compact and theoretical solutions for homogeneous structures with rigid and delayed restraints. This paper introduces an interactive web site for quick automatic calculation of the three basic functions: compliance, relaxation and redistribution, with reference to the principal creep models presently considered by international civil engineering societies. The program has been designed to be easy to use and to allow control pn all the parameters involved by the prediction models.
{"title":"Design Aids for the Evaluation of Creep Induced Structural Effects","authors":"Mario Sassone, M. A. Chiorino","doi":"10.14359/14433","DOIUrl":"https://doi.org/10.14359/14433","url":null,"abstract":"The general approach of creep analysis of structures based on the linear theory of viscoelasticity and on extended use of the four fundamental theorems leads to very compact and theoretical solutions for homogeneous structures with rigid and delayed restraints. This paper introduces an interactive web site for quick automatic calculation of the three basic functions: compliance, relaxation and redistribution, with reference to the principal creep models presently considered by international civil engineering societies. The program has been designed to be easy to use and to allow control pn all the parameters involved by the prediction models.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129148164","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 purpose of this study was two fold: to observe the magnitude of shrinkage of typical Virginia Department of Transportation (VDOT) concrete mixtures; and to assess the accuracy of the existing unrestrained shrinkage prediction models. The results indicated the following conclusions: The portland cement concrete mixtures exhibited about the same amount of drying shrinkage as expected for mixtures with small differences in cement, water, and aggregate content and similar strengths; the mixtures containing fly ash exhibited greater drying shrinkage than those containing microsilica and slag cement; the CEB 90 model appears to be the best predictor of drying shrinkage for the VDOT portland cement mixtures; for the lightweight high strength concrete mixtures, the CRB 90 model ranked higher at early ages, while the Bazant B3 model ranked higher at later ages; and for the high strength concrete mixtures, the G/L 2000 model ranked higher than the other models.
{"title":"Shrinkage of Virginia Transportation Concrete Mixtures","authors":"D. Mokarem, R. Weyers, M. Sprinkel","doi":"10.14359/14432","DOIUrl":"https://doi.org/10.14359/14432","url":null,"abstract":"The purpose of this study was two fold: to observe the magnitude of shrinkage of typical Virginia Department of Transportation (VDOT) concrete mixtures; and to assess the accuracy of the existing unrestrained shrinkage prediction models. The results indicated the following conclusions: The portland cement concrete mixtures exhibited about the same amount of drying shrinkage as expected for mixtures with small differences in cement, water, and aggregate content and similar strengths; the mixtures containing fly ash exhibited greater drying shrinkage than those containing microsilica and slag cement; the CEB 90 model appears to be the best predictor of drying shrinkage for the VDOT portland cement mixtures; for the lightweight high strength concrete mixtures, the CRB 90 model ranked higher at early ages, while the Bazant B3 model ranked higher at later ages; and for the high strength concrete mixtures, the G/L 2000 model ranked higher than the other models.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114557862","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 focus of this study is investigating the sensitivity of each creep prediction model wjen using various modulus of elasticity equations. Nine high strength concrete (HSC) mixes containing pozzolans were made and tested in the laboratory. The mixes consisted of three mixes with varying percentage of silica fume, three mixes with varying percentage of fly ash, and three mixes with different combination of silica fume and fly ash. Data on elastic modulus from these mixes as well as from other tests have been used to form the basis of developing an elastic modulus equation for HSC. Three creep prediction models are considered in the study.
{"title":"Effect of Modulus of Elasticity on Creep Prediction of High Strength Concrete Containing Pozzolans","authors":"Nakin Suksawang, H. Nassif","doi":"10.14359/14434","DOIUrl":"https://doi.org/10.14359/14434","url":null,"abstract":"The focus of this study is investigating the sensitivity of each creep prediction model wjen using various modulus of elasticity equations. Nine high strength concrete (HSC) mixes containing pozzolans were made and tested in the laboratory. The mixes consisted of three mixes with varying percentage of silica fume, three mixes with varying percentage of fly ash, and three mixes with different combination of silica fume and fly ash. Data on elastic modulus from these mixes as well as from other tests have been used to form the basis of developing an elastic modulus equation for HSC. Three creep prediction models are considered in the study.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"118 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132695715","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}
Even though volumetric changes of concrete slabs on grade in response to an environmental changes have been recognized for decades, they are still not well understood. Drying shrinkage induced curling of slabs on grade and thermal warping of pavements have been investigated numerous times, but a procedure for pavement design linking structural analysis and environmental behavior has not yet been developed. This study describes the behaviors and presents a theoretical framework for unraveling the complex nature of pavement response to the environment.
{"title":"Evaluation of Thermal Warping in Pavements","authors":"M. Miltenberger, E. Attiogbe, A. R. Stoddard","doi":"10.14359/14440","DOIUrl":"https://doi.org/10.14359/14440","url":null,"abstract":"Even though volumetric changes of concrete slabs on grade in response to an environmental changes have been recognized for decades, they are still not well understood. Drying shrinkage induced curling of slabs on grade and thermal warping of pavements have been investigated numerous times, but a procedure for pavement design linking structural analysis and environmental behavior has not yet been developed. This study describes the behaviors and presents a theoretical framework for unraveling the complex nature of pavement response to the environment.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122479323","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 outlines the results of a research study which was intended to better document how commercially available shrinkage reducing admixtures (SRA) influence the early-age shrinkage and residual stresses that develop when shrinkage is prevented. The paper will describe surface tension measurements of water SRA solutions for a commercially available SRA to quantify how SRAs can be used to alter the surface tension of a pore solution. Length change measurements were performed to measure the autogenous length change of setting mortar, and free shrinkage was measured after 24 hours for sealed and drying mortar. The effect of shrinkage, mechanical property development, elastic stress, and relaxation are discussed.
{"title":"Shrinkage Behavior and Residual Stress Development in Mortar Containing Shrinkage Reducing Admixtures (SRAs)","authors":"B. Pease, H. Shah, J. Weiss","doi":"10.14359/14435","DOIUrl":"https://doi.org/10.14359/14435","url":null,"abstract":"This paper outlines the results of a research study which was intended to better document how commercially available shrinkage reducing admixtures (SRA) influence the early-age shrinkage and residual stresses that develop when shrinkage is prevented. The paper will describe surface tension measurements of water SRA solutions for a commercially available SRA to quantify how SRAs can be used to alter the surface tension of a pore solution. Length change measurements were performed to measure the autogenous length change of setting mortar, and free shrinkage was measured after 24 hours for sealed and drying mortar. The effect of shrinkage, mechanical property development, elastic stress, and relaxation are discussed.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128197437","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 common structural system for bridges and highway overpasses often consists of precast, prestressed concrete girders made continuous through a cast-in-place deck and diaphragms. To assess the risk of cracking under service conditions the designer needs to estimate the internal stresses in the concrete. The paper will first compare, for a particular case study, differences in the time dependent response predictions resulting from changes in the structural analysis methodology and/or the material models used to describe concrete behavior. Second, the paper will assess the variability of the material models used in making predictions. A straightforward statistical approach is used to determine the 95% confidence intervals on predictions of the material properties critical to time dependent deformation. The study instrumented and monitored two precast, prestressed girders for strains and deflections for a five month period from fabrication to erection.To describe the behavior of the concrete used in the girders, laboratory tests were conducted to measure comparative strength, modeled of elasticity, creep, and shrinkage.
{"title":"Estimating Time-Dependent Deformations of Prestressed Elements: Accuracy and Variability","authors":"M. Paulsen, S. Alexander, D. Rogowsky","doi":"10.14359/14431","DOIUrl":"https://doi.org/10.14359/14431","url":null,"abstract":"A common structural system for bridges and highway overpasses often consists of precast, prestressed concrete girders made continuous through a cast-in-place deck and diaphragms. To assess the risk of cracking under service conditions the designer needs to estimate the internal stresses in the concrete. The paper will first compare, for a particular case study, differences in the time dependent response predictions resulting from changes in the structural analysis methodology and/or the material models used to describe concrete behavior. Second, the paper will assess the variability of the material models used in making predictions. A straightforward statistical approach is used to determine the 95% confidence intervals on predictions of the material properties critical to time dependent deformation. The study instrumented and monitored two precast, prestressed girders for strains and deflections for a five month period from fabrication to erection.To describe the behavior of the concrete used in the girders, laboratory tests were conducted to measure comparative strength, modeled of elasticity, creep, and shrinkage.","PeriodicalId":254369,"journal":{"name":"SP-227: Shrinkage and Creep of Concrete","volume":"26 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129134456","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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