Behavior of Beams Strengthened with Novel Self-Anchored Near-Surface-Mounted CFRP Bars
Publication: Journal of Composites for Construction
Volume 15, Issue 4
Abstract
A commonly observed failure mode in laboratory tests involving surface bonded fiber-reinforced polymer (FRP) laminates or near-surface-mounted (NSM) bars is premature delamination, that is, the separation of the FRP from the substrate well before the FRP reaches its ultimate strain capacity. To delay the onset of delamination and to ensure that the NSM FRP reinforcement continues to contribute to member strength after partial delamination, a new self-anchored carbon fiber-reinforced polymer (CFRP) bar was developed and tested for this investigation. This bar is made with a series of monolithic spikes that can be anchored deep inside the concrete. In addition to cutting grooves into the concrete cover for the placement of the primary reinforcing bar, holes are drilled deep into the concrete to insert the spikes. To test the performance of this bar, six large, simply supported, reinforced, concrete beams were retrofitted with NSM bars and tested in four-point bending. Two beams were strengthened with NSM bars without anchors or spikes but were otherwise similar to the self-anchored bar and served as control specimens (Series B1). Two beams were strengthened in flexure with the new self-anchored NSM bars (Series B2), and the remaining two beams (Series B3) were strengthened in flexure and shear by using the self-anchored NSM bars as partial shear reinforcement. The effect of the proposed strengthening system on the beams’ strength, failure mode, deformability, and ductility are discussed on the basis of the experimental results. The anchors delayed delamination and enabled the NSM bar to experience at least a 77% higher strain at failure than the companion bar without anchors. The anchors also increased beam displacement ductility and energy ductility at a 20% strength degradation by at least 34% and 42%, respectively.
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Acknowledgments
The writers would like to thank the NSERCNatural Sciences and Engineering Research Council of Canada for its continuing financial support of the first writer’s research. They would also like to thank the Centre for Effective Design of Structures at McMaster University for its financial support. Finally, they are grateful to AUTOCON Composites of Toronto and its officers Messrs. John Crimi and Leo Cammalleri for donating the CFRP grid used in the manufacturing of the proposed self-anchored bar and for their ongoing support of this research.
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Published In
Journal of Composites for Construction
Volume 15 • Issue 4 • August 2011
Pages: 625 - 634
Copyright
© 2011 American Society of Civil Engineers.
History
Received: Jun 3, 2010
Published online: Oct 1, 2010
Accepted: Oct 18, 2010
Published in print: Aug 1, 2011
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