Connections between precast elements―failure outside connection region

The performance of moment-resisting connections between precast columns and precast partially prestressed beams was investigated. The specimens represented exterior beam-column joints. The only variable among the specimens was the type of connection used. The four connection types considered were: posttensioned (BMA); threaded rebar (BMB); composite-post-tensioned in the bottom of the beam with a cast-in-place top (BMC); and welded (BMD). The structures were designed to develop a primary plastic hinge in the beams outside of the connection region (at 35 in. from the column face) where the prestressing strands were considered fully developed. All of the structures were subjected to identical cyclic lateral load histories. The connections were evaluated based on their performance in terms of strength, ductility and energy dissipation characteristics, as well as, their fabrication feasibility. Of the connection types tested, the most promising details were the threaded rebar and composite connections.