Seismic Retrofit of Flexural Bridge Spandrel Columns Using Fiber Reinforced Polymer Composite Jackets

Large-scale (80%) tests were conducted on one "as-built" and four composite jacketed rectangular flexural bridge spandrel columns to assess the effectiveness of different retrofit schemes using fiber reinforced polymer composite jackets. Retrofit challenges were in (1) the unknown response of the inclined interface between spandrel column and the arch rib and (2) the behavior of the column reinforcement lap splice located at the top of the spandrel column pedestal. Three of the four FRP retrofit systems only addressed the lap splice region, where as the fourth system connected the column jacket to the arch rib to improve the column/arch rib interface response. Final damage patterns and failure modes showed that only the latter scheme improve the seismic response whereas the other systems resulted in a sliding failure mode without improving the displacement capacity which for the prototype bridge response is less desirable than the original "as-built" lap splice debonding failure. All retrofit schemes successfully clamped the column reinforcement lap splice above the column pedestal construction joint. The tests showed that fiber reinforced polymer composite jacketing systems clearly can be installed without affecting the overall geometry or appearance of the structure, and emphasizes the importance of designing retrofit strategies to control the mode of failure. Retrofitting of one weakness without considering the next mode of failure can lead to ineffective and poor designs.