Performance of outside filament-wound hybrid FRP-concrete beams

A novel configuration of a hybrid FRP-concrete beam is presented. The beam consists of a GFRP pultruded profile, a CFRP laminate, and a concrete block all wrapped up using filament winding. Three different concrete blocks were used: high strength concrete, normal strength concrete and steel fibres reinforced high strength concrete. The major feature of the design is that it does not mimic that of reinforced concrete as reported previously. The CFRP laminate is not designed to fail first to serve as a warning of imminent failure, but rather to enhance the stiffness of the beam by compensating for the lack of stiffness of the GFRP profile. The experimental results have shown that this approach is successful. The wrapping did not only eliminate the risk of premature failure as a result of the concrete block debonding from the pultruded profile, but it was also found to enhance the stiffness and load carrying ability of the beams. The beams with a high strength concrete block showed increased stiffness and load carrying ability but failed in a catastrophic manner. On the other hand, the beams with normal strength and steel fibres reinforced high strength concrete showed improved ductility. The amount of energy dissipative behaviour was found to depend on the thickness of the concrete block. When the latter is too thin, failure akin to shear punching appears to take place.