Seismic Behavior of Steel Pile to Precast Concrete Cap Beam Connections

Precast concrete is increasingly being used for bridge construction. One useful modular bridge system consists of precast box deck units on precast concrete cap beams connected to exposed steel piles. This creates the difficult problem of a connection between the cap beam and the piles. A convenient design, favored by the Ministry of Transportation and Highways of British Columbia (MoTH), consists of a steel anchorage plate embedded in the concrete. The plate is then welded to the pile top after placement in the field. This research is an investigation of the performance of the MoTH design. A simple behavior model was devised that is suitable for preliminary design calculations, and a related finite element analysis was performed. The MoTH design was modified on the basis of the preliminary design. The connection was then fabricated and tested under cyclic loading to evaluate strength and ductility. The connection behaved as predicted, and plastic hinging in the pile was achieved. The principle of “capacity design,” in which the failure mode is controlled to ensure a favorable ductile response (e.g., pile yielding), was found to be difficult to implement due to numerous sources of overstrength of the materials, such as the pipe pile steel strength.