Seismic Retrofit of CISS Pile Bent Cap Connections

Three 4/5-scale units were cast, retrofitted, and tested under simulated seismic loads. These units were built to model a bridge bent consisting of a cast in place steel shell (CISS) column foundation shaft and a bent cap configured to form a tee connection. Each unit was retrofitted in the column, bent cap, and their connection according to current seismic design standards. The main objective was to ensuring ductile performance under lateral loads. Specific seismic improvements made to the column and the bent cap system were: (1) the moment capacity of the column was reduced by cutting a portion of the column longitudinal reinforcement at the connection to the bent cap to levels that can ensure a proper ductile seismic response, (2) a section of the steel shell was cut and removed leaving a gap between the steel shell and the bent cap, and (3) the bent cap dimensions were increased to ensure proper reinforcement spacing and to install additional flexure and joint shear reinforcement. Empirical models were developed that account for the effects of joint rotation and damage