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

Three different fiber-reinforced polymer (FRP) strengthening schemes were tested for their effectiveness in improving not only strength but also ductility of existing, nonconforming reinforced concrete beams. Eight full-size, two-span rectangular beams were considered in pairs, tested under monotonic or cyclic loading. One (control) pair was detailed with conventional steel reinforcement only for ductile flexural response and the remaining were strengthened in flexure using top, bottom, or side face FRP sheets or surface-mounted FRP rods, whereas transversely-wrapped glass FRP sheets were applied in all three pairs to prevent shear failure. 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. Cyclically loaded beams, however, failed at the first hinge critical region by debonding of the transverse FRP, diagonal shear cracking of the concrete, and buckling of the longitudinal steel. [PUBLICATION ABSTRACT]