Seismic performance of concrete-encased CFST piers : experimental study

Concrete-encased concrete-filled steel tube (CFST) box members have been recently used as piers and arches in bridges owing to their high stiffness and strength. However, the seismic behavior of these members has not been thoroughly investigated, which hinders the usage of such members in earthquake-prone zones. In this study, eight concrete-encased CFST box specimens and eight RC box counterparts were tested under constant axial load along the specimen and cyclic lateral load at the mid span. The experimental parameters were the axial load level and cross-sectional type of the column. The effects of these parameters on the strength, ductility, stiffness degradation, and energy dissipation were studied. Compared with the corresponding RC box columns, the performances of concrete-encased CFST box columns, including the lateral resistance, stiffness degradation, ductility, and energy dissipation capacity, were significantly improved. A simplified calculation method was proposed to evaluate the flexural resistance of concrete-encased CFST box columns