Restoring force characteristics and model of concrete filled steel tube column

A restoring force model of concrete filled steel tube column (CFT column) is obtained from the cyclic loading test of CFT column. The restoring force model is composed of the Tri-linear model and the Clough model and easily applicable to seismic response analysis of CFT frames under strong ground motion. The proposed model is defined by the yield strength, the ultimate strength and the accumulated plastic deformation capacity of CFT column. The equations to express these characteristics of CFT column are also derived from the test results. By the use of the energy absorbing capacity of CFT column it is ascertained that the presented model can predict the restoring force characteristics of the CFT specimens.