Experimental Investigation on Seismic Retrofitting of Square RC Columns by Carbon FRP Sheet Confinement Combined with Transverse Short Glass FRP Bars in Bored Holes

Jacketing is less effective to large square/rectangular RC columns due to the inability of the rectangular-shaped jacket in restraining the dilation of concrete in the middle of a straight side. A new retrofit method is proposed in this work by fiber reinforcing the surface concrete in the middle of a straight side. Fiber reinforcing is achieved by inserting small fiber-reinforced polymer (FRP) bars into the concrete in the plastic hinge zone. The inserted FRP bars act as horizontal reinforcement to increase the ductility of the concrete in a similar way as that in normal fiber-reinforced concrete. When this fiber reinforcing technique is combined with the conventional jacketing, the concrete in all parts of a cross section may be effectively confined. In this work, experimental tests were undertaken to investigate the effectiveness of this new retrofit technique. Six half-scaled columns were tested and the test results demonstrated the effectiveness of the method.