Performance of RC Beams Strengthened Using Prestressed NSM-CFRP Strips Subjected to Fatigue Loading
Publication: Journal of Composites for Construction
Volume 16, Issue 3
Abstract
The fatigue performance of Reinforced Concrete (RC) beams strengthened using prestressed Near Surface Mounted (NSM) Carbon Fiber Reinforced Polymer (CFRP) strips was evaluated in this paper. Five full-scale RC beams were tested under fatigue loading simulating in-service loading conditions: one control unstrengthened beam and four beams strengthened using NSM-CFRP strips prestressed to 0, 20, 40, and 60% of the CFRP ultimate tensile strength. All beams were subjected to fatigue loading for 3 million cycles at a frequency of 2.0 Hz such that the stress range induced in the tension steel, during the initial cycle, is 125 MPa as specified by the Canadian Highway Bridge Design Code. Experimental test results show that the percentage deflection increase at the end of fatigue loading was almost the same for all beams, which implies that damage accumulation is independent from the prestress level. CFRP strain variation at midspan indicated the occurrence of deboning during the initial cycling of beams prestressed to 0 and 20%, whereas no signs of bond degradation were observed in the other beams. Therefore, prestressing the CFRP strips was shown to enhance the bonding properties and results in an overall CFRP strain increase at the completion of the fatigue loading. For all beams, steel and concrete strains and crack widths at midspan increased rapidly in the initial 500 cycles, followed by stabilized linear increase trends for the rest of the fatigue loading.
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Acknowledgments
The authors would like to express their gratitude to Lafarge Canada for providing the concrete, Sika for providing the epoxy, Hughes Brothers for donating the CFRP strips, and the technical staff at the University of Calgary for their assistance in the laboratory. The authors are also grateful for the financial support toward this research provided by the Canadian Networks of Centers of Excellence on Intelligent Sensing for Innovative Structures (ISIS Canada), the Natural Sciences and Engineering Research Council of Canada (NSERC), and the University of Calgary.
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Information
Published In
Journal of Composites for Construction
Volume 16 • Issue 3 • June 2012
Pages: 300 - 307
Copyright
© 2012. American Society of Civil Engineers.
History
Received: May 17, 2011
Accepted: Oct 14, 2011
Published online: Oct 18, 2011
Published in print: Jun 1, 2012
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