Shear Strengthening of RC Beams by Externally Bonded Side CFRP Strips

Abstract

This paper presents results of an experimental investigation on the response of reinforced concrete beams strengthened in shear using externally applied epoxy-bonded unidirectional carbon-fiber plastic side strips. Three series of 1,300-mm-long reinforced concrete (RC) beams are considered: (1) a series of beams having full strength in shear; (2) a series of beams underreinforced in shear; and a (3) series of beams strengthened in shear. Side strips placed either perpendicularly or diagonally to a beam's longitudinal axis provided the external shear reinforcement. The beams were instrumented and tested under four-point load conditions. Results show the feasibility of using epoxy-bonded strips to restore or increase the load-carrying capacity in shear of RC beams while substantially reducing shear cracking. RC beams strengthened by diagonal side strips outperformed those strengthened with vertical side strips. However, under extreme loading conditions concrete may be torn off at anchorage zone where high concentration of tensile normal stresses is present.