Seismic performance of hollow-bridge piers repaired by FRP

Designed by the principle of weak column-strong beam, bridge piers are vulnerable following an earthquake. Failures of existing bridge column such as longitudinal bar fracture, shear failure and bond loss at lap splice are commonly seen. The objective of this research is to propose an effective repair technique for hollow bridge columns so that bridge function can be quickly restored after earthquakes. The repair aims to restore seismic capacity in terms of strength and ductility without altering above-mentioned design principle for bridges. To repair the longitudinal fractured bars in plastic hinge, a newly designed dog-bone shape bar was applied. After replacing damaged concrete, various FRP wraps were applied to enhance deformation capacity of columns failed due to flexure, shear and bond loss. Four full-size hollow-bridge piers were constructed, tested, repaired and retested. Test result validate that fractured bars can be successfully repaired by a newly design dog-bone shape bar. And FRP wraps can enhance the deformation capacity of hollow columns; however, column strength is not restored as high as expected due to concrete deterioration at cracks and bars buckled in inner layer. Column with flexure-shear deficiency was upgraded to flexural dominance by FRP wraps and dog-bone bars. The applied analytical models may evaluate the column strength and predict its failure modes.