Constitutive models for hollow steel tubes and concrete filled steel tubes considering the strength deterioration

This paper studies the stress-strain models to simulate the strength deterioration of the confined concrete and various sectional steel tubes in hollow steel tubular (HST) columns and concrete filled steel tubular (CFT) columns. The stress-strain models for above components by considering strength deterioration are simplified as to analyze steel and CFT frames subjected to ground motions. The model consists of an elastic-plastic curve up to the peak and a bi-linear after the peak which expresses the strength deterioration by negative slopes. The characteristic parameters of the stress-strain models for in-filled concrete and steel tubes are calibrated by comparing the component test results and the corresponding analytical results, and the proposed formulae for the deteriorating models of HST and CFT columns can accurately simulate the strength, stiffness and deterioration after local-failures.