188 publications from this institution
Four 6.5 m long two span continuous beams were tested to investigate the feasibility of using FRP grids as shear reinforcement. The beams were longitudinally reinforced with equal amounts of CFRP reinforcement while transversely two beams were reinforced with steel stirrups and two with CFRP grids. The two spans of each beam had identical amount and disposition of reinforcement, and were symmetrically loaded with a point load at the center of each span. For the beams with steel stirrups, the so-called Av/s = 2.0 mm while for the ones with CFRP grids the equivalent quantity was 1.75 mm. The elastic modulus of the grid was half the elastic modulus of the steel. The beams were monotonically loaded to destruction and they all failed in flexure. Despite their lower shear reinforcement ratio, the beams with the CFRP grid performed as well as those with the steel stirrups. They actually failed at 10% higher load than the beams with steel stirrups. Strain values of up to 0.4% were measured in the grids. Recognizing the practical convenience of grid shear reinforcement over custom manufacturing of stirrups, and considering their satisfactory performance, as observed in the present testing program, the use of FRP grids as shear reinforcement is indeed feasible.
A hybrid reinforcement system is proposed which consists of a low modulus polymeric reinforcement combined with CFRP, and which is believed to overcome the lack of ductility in FRP reinforced concrete members. Three 4.2 m long and 400 mm deep, high strength concrete inverted T-beams were designed using this new concept and were tested under four point bending. Two of the beams contained hybrid reinforcement while the third contained only CFRP reinforcement (control beam). The control beam failed suddenly, following the rupture of the CFRP reinforcement. The beams with hybrid reinforcement failed in a ductile manner at 63% higher load and they had at least three times more deflection at failure than the control beam. In the later beams, deflections substantially increased following the rupture of CFRP, but the moment of resistance of the beams decreased marginally. Upon release of the load, the hybrid reinforced beams rebounded and had very little deflection under self-weight.
