Comparison of Three Flexural Retrofit Systems under Monotonic and Fatigue Loads
Publication: Journal of Bridge Engineering
Volume 10, Issue 6
Abstract
The majority of experimental work involving the flexural retrofit of concrete bridge girders has been conducted on beam specimens with adhesive-applied, soffit-mounted, fiber-reinforced polymer (FRP) composite systems, referred to in this study as conventional adhesive application (CAA). It has been observed that the performance of such girders is often controlled by the quality of the bond between the FRP and the concrete substrate and the substrate’s ability to transfer stress from the steel to the FRP. With the goal of improving the performance of bonded FRP in mind, two additional soffit-mounted retrofit schemes are investigated: near-surface mounted (NSM), where the FRP strips are embedded in adhesive within slots cut into the substrate concrete, and, powder-actuated fastener-applied (PAF) FRP, which uses a powder-actuated nail gun to install mechanical fasteners through predrilled holes in the FRP into the concrete substrate, “nailing” the FRP in place. The PAF application is a recent development, and little work has been done on it other than by the proprietors of the system. This study reports on a comparative study of the static and fatigue performance of reinforced concrete beams retrofitted with CAA, NSM, and PAF FRP retrofit systems. Ten medium-scale beams were tested: six strengthened specimens, two per retrofit method, were tested under cyclic loading conditions, and four specimens, one per retrofit method and one control specimen, were tested monotonically to failure. The results of this study indicate that although all three methods of FRP application result in significant strength increases over the control specimen under monotonic loading conditions, the CAA method is outperformed by the other methods under cyclic conditions. A number of other relevant detailed conclusions with respect to performance and practical application issues are presented for each of the methods of retrofit examined in this study. Significantly, clear evidence of FRP debonding in the midspan region prior to specimen failure is presented.
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Acknowledgments
The writers would like to thank Dr. Anthony Lamanna of Tulane University and Dr. Larry Bank at the University of Wisconsin–Madison for their assistance with the PAF specimens. Thanks also go to Ms. Sarah Witt and Mr. Edward Fyfe of Fyfe Company, San Diego, California, for providing material for the CAA and NSM specimens. This research was supported by the South Carolina Department of Transportation/Federal Highway Administration and the National Science Foundation (CMS 9908293). Their support is greatly appreciated.
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Information & Authors
Information
Published In
Journal of Bridge Engineering
Volume 10 • Issue 6 • November 2005
Pages: 731 - 740
Copyright
© 2005 ASCE.
History
Received: Jan 29, 2004
Accepted: Jan 25, 2005
Published online: Nov 1, 2005
Published in print: Nov 2005
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