Effects of Bond Configurations on Flexural Response of RC Beams Externally Strengthened with CFRP Sheets

This paper investigates experimentally how various bond configurations influence the flexural response of FRP-strengthened RC beams. A total of seven beams(200×200×2200mm) were tested. One was the reference without strengthening. Two were strengthened with CFRP sheets using hard and soft adhesive bonding, respectively, along the whole test span. The remaining four were applied a combination of hard and soft adhesives but in two different ways. One way is to use the soft adhesive at the flexure-dominating zone only and another is to use it for the shear-dominating zone only. Pair tests were conducted for these four specimens under both normal and low temperature (-10C). It is revealed that a sole use of soft adhesive improves the ultimate member strength and ductility but leads to a loss of stiffness. Using the soft adhesive at the flexure-dominating zone can not improve the member strength but improve the member ductility only. However, use of hard adhesive at the flexure-dominating zone and the soft one for the remaining parts can improve the member strength and ductility while avoiding loss of member stiffness. This test program provides an in-depth understanding of the debonding mechanisms in the FRP-strengthened RC beams. In addition, it is verified that that a low temperature of -10C does not influence the global flexural response of FRP strengthened beams using the combined bonding system.