External FRP Poststrengthening of Scaled Concrete Slabs

This research investigates the effect of externally bonded fiber-reinforced polymer composite strips and fabric to the soffit of scaled slabs. Thirteen slabs of size 2,290 × 480 × 102 mm were tested to failure with varying configurations of externally bonded composites, while monitoring deflections, strains, and damage development. The measured response is compared with analytical results to demonstrate an approximate analysis method. It is shown that, although the ultimate load level can be increased significantly, failure is associated with a drastically reduced deformation capability and a change from the conventional ductile mode of failure to a more brittle one. Failure is dependent on the form of the reinforcement used and is shown to be different based on type and configuration of the external strengthening system used. Failure mechanisms range from delamination within the concrete cover and separation between tows in the prefabricated strips, to tensile rupture in the case of fabric-reinforced composite layers. Mechanisms of failure and efficiency of strengthening schemes based on fiber configuration are discussed.