Overview of the Washington State Bridge Seismic Retrofit Program and Research Projects

This paper presents retrofit measures for improving the seismic performance of columns in Washington State. Tests on column specimens representing as-built conditions resulted in shear failures at modest displacement levels, accompanied by severe strength and stiffness degradation. Tests on column specimens retrofitted with FRP jacketing resulted in improved performance compared to that obtained for the as-built column specimens. It was found that the FRP jacket needs to be anchored in the reentrant corners of the cruciform-shaped columns to be effective. In addition, the FRP jacket does not provide adequate confinement to prevent flexural hinge degradation. The final retrofit design incorporating reentrant corner anchorage and groutfilled steel collars at the hinge regions produced a ductile flexural response.