Experimental Study on Seismic Performance of Reinforced Concrete Columns Retrofitted with Composite-Materials Jackets

In order to improve seismic performance of existing R/C buildings which were designed on the basis of the old seismic design code before 1981, the various retrofitting methods have been proposed, especially after the Hyogo-ken Nanbu earthquake happened in 1995 in Japan. In this study, an experimental study was conducted to examine the seismic performance of existing R/C columns retrofitted with composite-materials such as carbon fiber or aramid fiber sheets. Quantity, retrofitting types and kinds of continuous fiber sheets were adopted as the experimental variables. As a result, by retrofitting columns with continuous fiber sheets, the failure mode of the columns changed from shear failure to flexural one. However, if the ply of continuous fiber sheets is not enough, the columns collapse because of hinge region concrete crashing just after longitudinal rebar yielding and its ductility is poor. Therefore, to make R/C column retrofitted with fiber sheets have good ductility, the fiber sheets should have a certain amount of membrane stiffness.