Behavior of RC Beams Shear Strengthened with Bonded or Unbonded FRP Wraps
Publication: Journal of Composites for Construction
Volume 13, Issue 5
Abstract
Reinforced concrete (RC) beams shear-strengthened with fiber-reinforced polymer (FRP) fully wrapped around the member usually fail due to rupture of FRP, commonly preceded by gradual debonding of the FRP from the beam sides. To gain a better understanding of the shear resistance mechanism of such beams, particularly the interaction between the FRP, concrete, and internal steel stirrups, nine beams were tested in the present study: three as control specimens, three with bonded FRP full wraps, and three with FRP full wraps left unbonded to the beam sides. The use of unbonded wraps was aimed at a reliable estimation of the FRP contribution to shear resistance of the beam and how bonding affects this contribution. The test results show that the unbonded FRP wraps have a slightly higher shear strength contribution than the bonded FRP wraps, and that for both types of FRP wraps, the strain distributions along the critical shear crack are close to parabolic at the ultimate state. FRP rupture of the strengthened beams occurred at a value of maximum FRP strain considerably lower than the rupture strain found from tensile tests of flat coupons, which may be attributed to the effects of the dynamic debonding process and deformation of the FRP wraps due to the relative movements between the two sides of the critical shear crack. Test results also suggest that while the internal steel stirrups are fully used at beam shear failure by FRP rupture, the contribution of the concrete to the shear capacity may be adversely affected at high values of tensile strain in FRP wraps.
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Acknowledgments
The writers are grateful for the financial support received from the Research Grants Council of the Hong Kong SAR (Grant No. UNSPECIFIEDPolyU 5151/03E) and The Hong Kong Polytechnic University (Grant No. UNSPECIFIEDBBZH). The writers also thank Ms. Maggie Fung and Mr. Simon Morton for their valuable contribution to the experimental work.
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Information & Authors
Information
Published In
Journal of Composites for Construction
Volume 13 • Issue 5 • October 2009
Pages: 394 - 404
Copyright
© 2009 ASCE.
History
Received: Sep 13, 2008
Accepted: Mar 20, 2009
Published online: Sep 15, 2009
Published in print: Oct 2009
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