Time-Dependent Behavior of RC Beams Retrofitted with CFRP Straps
Publication: Journal of Composites for Construction
Volume 15, Issue 1
Abstract
A retrofitting technique that uses prestressed unbonded carbon-fiber-reinforced polymer (CFRP) straps to provide additional shear capacity has previously been shown to be successful under short-term static loading conditions. The current study explores the longer-term behavior of this retrofitting technique through two experiments (a sustained load and a cyclic load experiment) and the development of a model based on the modified compression field theory. The experiments indicated that the strain in the CFRP straps changes with time due to changes in the load sharing with the concrete (caused by creep) and the steel stirrups (caused by yield of these elements). The predictive model was initially validated against static experimental results before being applied to the longer-term experiments. The model predicts the trends in behavior well although it is conservative in its estimates of strap strain. The model was then used to determine the influence of stirrup yielding, the load level before and after retrofitting, and the duration of loading on the CFRP strap strains. The initial results suggest that the largest increases in long-term strap strain will occur when the straps are installed early in the structure’s service life although further experimental validation is required.
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Acknowledgments
The writers would like to thank EMPA for their support of this project. The first writer is also indebted to the Cambridge Commonwealth Trust as well as Universities U.K. for providing financial assistance during the course of his studies.
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Information & Authors
Information
Published In
Journal of Composites for Construction
Volume 15 • Issue 1 • February 2011
Pages: 75 - 84
Copyright
© 2011 ASCE.
History
Received: Jan 15, 2010
Accepted: Jul 13, 2010
Published online: Jul 16, 2010
Published in print: Feb 2011
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