Seismic Strengthening of Column-Pier-Cap Connections

Abstract

Many bridges constructed in the 1960s in regions of high seismic risk have column–pier-cap connections with inadequate column bar development and no shear reinforcement in the joint region. The study described in this paper focuses on highway bridges built on Interstate 80 in the Reno, Nevada, area during the 1960s. Two 0.4-scale specimens representing the essential features of the column–pier-cap connections in these bridges were constructed and tested. One test showed that the asbuilt specimen had little energy dissipation capacity and failed at less than 1 percent drift. A second specimen was used to test a potential strengthening technique. The technique included increasing pier-cap depth, adding a concrete bolster to the joint, and placing a steel jacket around the column. After strengthening, a plastic hinge formed in the column, the joint damage was minimized, and the energy dissipation capacity increased by a factor of 5.