Seismic strengthening of circular bridge pier models with fiber composites

An experimental investigation was conducted to study the seismic behavior of reinforced concrete columns strengthened with fiber reinforced plastic (FRP) composite straps. Five concrete column-footing assemblages were constructed with a 1/5-dimensional scale factor. The unidirectional glass fabric straps were impregnated with polyester resin and wrapped around the potential plastic hinge zone of the columns. An epoxy layer was applied to the straps while wrapping for interlaminar bond. All specimens were tested under inelastic reversal loading while simultaneously subjected to a constant axial load. Test results show that seismic resistance of retrofit concrete columns improves significantly as a result of the confining action of the FRP composite straps. The straps are highly effective in confining the core concrete and preventing the longitudinal reinforcement bars from buckling under cyclic loading.