Analysis of Snap-Back Instability due to End-Plate Debonding in Strengthened Beams
Publication: Journal of Engineering Mechanics
Volume 136, Issue 2
Abstract
The problem of end-plate debonding of the external reinforcement in strengthened concrete beams is analyzed in this paper. As experimentally observed, this mode of failure is highly brittle and poses severe limitations to the efficacy of the strengthening technique. A numerical analysis of the full-range behavior of strengthened beams in bending is herein proposed to study the stages of nucleation and propagation of interfacial cracks between the external reinforcement and the concrete substrate. This is achieved by modeling the nonlinear interface behavior according to a cohesive law accounting for Mode Mixity. The numerically obtained load versus midspan deflection curves for three- or four-point bending beams show that the process of end-plate debonding is the result of a snap-back instability, which is fully interpreted in the framework of the Catastrophe Theory. To capture the softening branch with positive slope, the interface crack-length control scheme is proposed in the numerical simulations. The results of a wide parametric study exploring the effect of the relative reinforcement length, the mechanical percentage of fiber-reinforced polymer sheets, the beam slenderness, and the ratio between Mode II and Mode I fracture energies are collected in useful diagrams. Finally, an experimental assessment of the proposed model completes the paper.
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Acknowledgments
The financial support provided by the UNSPECIFIEDEuropean Union to the Leonardo da Vinci ILTOF Project (Innovative Learning and Training on Fracture) is gratefully acknowledged.
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Published In
Journal of Engineering Mechanics
Volume 136 • Issue 2 • February 2010
Pages: 199 - 208
Copyright
© 2010 ASCE.
History
Received: Dec 20, 2007
Accepted: Oct 5, 2009
Published online: Jan 15, 2010
Published in print: Feb 2010
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