Cyclic response of concrete-encased composite columns with low steel ratio

Abstract

Improved economy and speed of construction can be achieved through the use of prefabricated structural members. As a step in the advancement of prefabricated substructures, a precast composite column system for seismic regions is proposed in this work. In order to enhance the seismic performance of the reinforced concrete (RC) pier, it is customary to cover the plastic hinge areas of the RC column with close transverse reinforcements. Concrete-encased composite columns with core structural steel can be regarded as another useful method to reinforce RC columns. Eight concrete-encased composite specimens with a low steel ratio were fabricated in this work. The quasi-static test was carried out to investigate the cyclic response of composite columns embedded with single structural steel and multiple structural steels. The specimens were composed of a concrete-encased section and structural steel, the steel being an H-shaped or a circular tube. Concrete was partially in-filled inside a circular steel tube. The test parameters used are the amount of transverse reinforcement, structural steel and loading pattern. Seismic performance was investigated by measuring the ductility and the energy-absorption capacity of composite columns. The effects of embedded steel members and transverse reinforcements on the cyclic performance were estimated through the observation of local behaviour. It was observed from test results that structural steels increased the deformation capacity of RC columns. In order to satisfy required ductility in seismic regions for composite columns with low steel ratio, it is adequate to follow the detail requirements of transverse reinforcement for RC columns to satisfy required ductility in seismic regions.