Bridge Footing Strengthening Using Various FRP Systems

Bridge footing plays an important role in transferring the load from the bridge superstructure to the soil underneath. It might need structural strengthening due to insufficient flexural or shear capacity, while in most cases punching shear failure is the dominant failure mode. The most commonly applied retrofit strategy is to enlarge the dimensions of the footings, where dowel splice connections are installed to connect additional concrete to the existing footing. However, the splice connection is not practical. In this paper, a series of upgraded enlarging footing retrofit methods for spread footing using FRP systems are proposed, including an active strengthening system and three passive strengthening systems. For all systems, the connection at the interface is achieved by composite action, instead of dowel connection. Thus, the new connection type is simple and effective. In the active system, circular external prestressing strands were installed. While in the passive systems, the exterior surface of the retrofitted footing was wrapped with different materials including CFRP, BFRP, and steel. A total of Eighteen footings were simulated using Abaqus CAE, and the punching shear capacity of each model was calculated. The results of this investigation suggest that both the active and the passive retrofit systems can significantly improve the punching shear capacity of the spread footing.