Experimental Investigation of Seismic Repair and Retrofit of Bridge Columns by Composite Jackets

Abstract

This paper summarizes the results of comprehensive experimental studies on half-scale bridge columns repaired and retrofitted with composite-material jackets. The experimental program was composed of two interrelated subprograms. Initially, a total of fourteen half-scale squat circular and rectangular reinforced concrete columns were tested under fully reversed cyclic shear in a double bending configuration. In order to provide a basis for comparison, a total of three as-built columns were tested. Another ten column samples were tested after being retrofitted with different composite-jacket systems. One circular as-built column was repaired after failure. The repair process involved both crack injection, as well as addition of carbon/epoxy composite jacket. The repaired column was then retested and evaluated. Experimental results showed that all as-built columns developed an unstable behavior and failed in brittle shear mode. The common failure mode for all retrofitted samples was due to flexure with significant improvement in the column ductility. The repaired column demonstrated ductility enhancement over the as-built sample. In the second subprogram, a total of thirteen half-scale circular and square column models were constructed with short lap-splice details at the base, and were tested in flexure under lateral cyclic loading. Three as-built columns were tested and a total of ten columns were tested after being retrofitted with different composite-jacket systems. In general, the common mode of failure for the as-built samples was a brittle failure due to bond deterioration of the lap-spliced longitudinal reinforcement. The jacketed circular columns demonstrated a significant improvement in their cyclic performance. However, tests conducted on square jacketed columns showed a very limited improvement in clamping on the lap splice region and for enhancing the ductility of the column.