Investigation of Monotonic and Cyclic Response of Fiber-Reinforced Polymer Strengthened Beams

Abstract

This study investigates the hysteretic characteristics, ductility and moment redistribution capacity of beams strengthened with fiber reinforced polymer (FRP) materials. Three different FRP strengthening schemes were tested for their effectiveness in improving strength and ductility of existing, nonconforming reinforced concrete beams. Eight full-size, two-span rectangular beams were considered in pairs, tested under monotonic or cyclic loading. Six were strengthened in flexure using top, bottom, or side face FRP sheets or surface mounted FRP rods, while transversely-wrapped glass FRP sheets were applied in all three pairs to prevent shear failure. One control pair was detailed with conventional steel reinforcement only for ductile flexural response. Results showed that monotonically loaded beams failed in flexure. Unlike top and bottom face strengthened beams, side strengthened beams exhibited superior performance comparable with the control, in terms of overstrength, ductility, and deformation capacity. All beams under increasing amplitude cyclic response were unable to develop the montonic capacity of a flexural mechanism. No matter which method of FRP strengthening had been used, cyclic behavior exhibited severe pinching and gradual strength and stiffness degradation.