CCEER-95-4: Seismic Retrofit of Column-Pier Cap Connections in Bridges in Northern Nevada

Abstract

The purpose of this study was to evaluate and improve the seismic resistance of the column-pier cap connection of bridges with inadequate column bar development and no shear reinforcement in the joint region. The study focused on highway bridges built on Interstate 80 in the Reno area, during the 1960's. Other bridge components were studied, but are described in other reports. A 0.4 scale specimen representing the essential features of the connections in these bridges was constructed and tested. The tests results showed that the as-built specimen had little energy dissipation capacity and it failed at less than 1 percent drift.

A retrofit was developed and implemented on an identical specimen. The retrofit included increasing pier cap depth, adding a concrete bolster to the joint, and placing a steel jacket around the column. The retrofitted specimen was then tested in the same manner as the as-built specimen. All the retrofit design objectives were met. A plastic hinge formed in the column, the joint damage was minimized, and the energy dissipation capacity increased by a factor of five. Based on the test results, recommendations were given for retrofitting bridges with deficient column-pier cap connection strength (Abstract by authors).