FLEXURAL STRENGTHENING OF RC BEAMS USING EXTERNALLY BONDED FRP SHEETS THROUGH FLEXIBLE ADHESIVE BONDING

Abstract

This paper reports summarily a flexible FRP/concrete bonding system for flexural strengthening of RC members. The bonding adhesive used in this system has very low elastic modulus but large elongation up to tensile fracture. Therefore, bonding line between FRP and concrete can bear large shear deformation to delay or prevent the occurrence of local interface debonding. Results from pullout tests of FRP sheet/concrete interfaces, laboratory tests on static and fatigue performance of RC members strengthened with FRP sheets, and a fullscale test on a T-beam of 15m span are reported in this paper. Failure mechanisms of strengthened members in cases of normal bonding and flexible bonding systems are clarified comparatively. Compared to the normal adhesive bonding system, the flexible one has proven its promising validity in strengthening RC beams in terms of their ultimate strength and deformability. However, this technique is favored for the ultimate limit state strengthening purpose only since it contributes less stiffness enhancement under the serviceability limit state.