The unified theory for concrete-filled steel tube (CFST) columns under various loads

Abstract

This paper presents the stress distribution, confinement distribution and complete average longitudinal stress-strain curves for concrete-filled steel tubular elements. Based on the definition of the “Unified Theory”, the CFST is looked upon as an entity of a new composite material. In this paper, the research achievement of the strength and stability for centrifugalhollow and solid concrete filled steel tube are introduced. These behaviours relate to the hollowness ratio and the confining indexes of corresponding solid CFST. If the hollow ratio equals to 0,4-0,5 and over, the N- ε relationship exists steady descending stage. The stage of behaviours are changed with the change of hollow ratio, it is series and continuity. The critical stress of CFST elements stability is determined as an eccentric member with the initial eccentricity by use of finite element method.