Enhancing the Debonding Strain Limit for CFRP-Strengthened RC Beams Using U-Clamps: Identification of Design Parameters
Publication: Journal of Composites for Construction
Volume 20, Issue 1
Abstract
In simply-supported reinforced-concrete (RC) beams strengthened by carbon-fiber-reinforced polymer (CFRP) plates, plate debonding is initiated at the beam ends, where the principal compression, predominantly composed of a vertical component, detaches the plate externally bonded to the unconfined cover concrete. A CFRP wrap acting as a U-clamp can provide confinement to enhance the moment capacity by resisting premature cover debonding. The wrap design parameters in terms of clamping location, width, and stiffness were identified from a set of fundamental experiments. The ultimate moment capacities of 22 tested specimens with different end anchorage conditions were compared against control specimens. The debonding strain, and consequently the ultimate moment capacity, gradually increased with increasing U-clamp width and stiffness. The failure patterns confirmed the effect of U-clamps in inducing a partial confinement effect on the sides and bottom of a beam end. The resulting changes in the compressive principal stress distribution in the compression arch were considered in formulating relationships for debonding strain prediction. The proposed relationship successfully predicted values regarding strengthened stone and brick aggregate concrete beams. The relationships for both unclamped and U-clamped anchorages better reproduced the experimental moment capacity enhancements than did the known equations. To assess the derived relations’ wider applicability, the estimates obtained using the proposed relations were compared against published results for 42 test beams.
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Acknowledgments
The authors are grateful to the members and staff of the Concrete Laboratory and Structural Mechanics Laboratory, Department of Civil Engineering, Bangladesh University of Engineering and Technology for their support and cooperation in conducting the tests. The authors gratefully acknowledge the kind cooperation extended by LaMaCo System Sdn Bhd, Malaysia, who provided samples of the fiber-reinforced polymer plate used in this investigation. Special thanks go to Ratanpur Steel Re-Rolling Mills Ltd. and Shun Shing Group, who provided the steel reinforcements and cement, respectively. The authors also sincerely appreciate the funding provided by the Committee for Advanced Studies and Research, BUET, Dhaka, Bangladesh, and the technical support of Bangladesh Bridge Authority and M/S Aziz & Company Limited, Dhaka, Bangladesh, for this research.
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Published In
Journal of Composites for Construction
Volume 20 • Issue 1 • February 2016
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© 2015 American Society of Civil Engineers.
History
Received: Feb 27, 2015
Accepted: Jun 5, 2015
Published online: Jul 22, 2015
Discussion open until: Dec 22, 2015
Published in print: Feb 1, 2016
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