Seismic behavior of a bridge pier with innovative fiber composite and concrete elements

An innovative structural frame employing concrete, steel, and carbon fiber composite sheets was developed and implemented in a two-column bridge pier. The basic concept for the pier design is that the pier has pre-assigned plastic hinges in the columns. Outside plastic hinges, the pier is to remain elastic. The innovative concept incorporated in the frame is that where plastic hinging and ductility is required, steel reinforcement is used as the longitudinal reinforcement and where elastic behavior is required carbon fiber reinforced plastic (CFRP) sheets are used as the longitudinal reinforcement. Confinement and shear capacity are provided for by FRP sheets at all locations. The frame is detailed so that plastic hinges are shifted away from the column ends because shifted plastic hinges prevent damage from penetrating into the joint area and are easier to repair. A quarter-scale, two-column pier with square columns was designed and constructed based on the aforementioned concept. Ordinary concrete and mild steel were used in the frame. The unidirectional Replark carbon composite by the Mitsubishi Corporation was placed on the frame. The frame was studied using computer programs DRAIN 3-DX and RC-Shake and a shake table testing program was developed. The shake table tests were completed recently. The frame was subjected to successive runs of the 1994 Northridge-Sylmar record with increasing amplitudes until failure. The plastic hinges behaved as planned, and the failure occurred after the rapture of the FRP wraps in one of the plastic hinges. There was no apparent damage outside the plastic hinges.