Assessment of Steel and Fiber Reinforced Plastic Jackets for Seismic Retrofit of Reinforced Concrete Columns with Structural Flares

Abstract

An analytical and experimental study of reinforced concrete flared bridge columns was conducted to determine an appropriate retrofit method for columns with inadequate shear capacity under earthquake loads. Four 0.3-scale models were tested on a shake table to failure, one representing as-built columns and the other three retrofitted with jackets, one with steel, one with a glass fiber reinforced plastic (FRP), and the third with a carbon FRP jacket. The jackets were designed to keep the plastic hinge away from the column end. A new lay up method was developed for FRP fabrics used on nonprismatic members. The results showed that all jackets improved the seismic performance. The effectiveness of the jackets was nearly the same for all materials. The method to estimate shear capacity based on the guidelines of the California Department of Transportation and a modified version of that method were found to closely estimate the shear capacity. However, the method in the Federal Highway Administration seismic retrofit manual overestimated the shear capacity and was unconservative.