UNIFIED STRENGTH THEORY FOR CONCRETE FILLED STEEL TUBE COLUMNS

This paper focuses on the yielding criterion of a high-strength concrete filled steel tube column under axial compression with flexure. The steel tube and infill concrete are all governed by unified strength theory, and their different material properties are reflected by parameters b and α. Considering the additional bending moment caused by horizontal displacement, a new constitutive equation is proposed associated with the flow rule based on the generalized unified failure criterion by which the vertical stress distributes linearly from the tension side to the compression side of a section. The yielding strength can be calculated from a plastic potential function while the column bottom remains in a plastic state. In addition, this new method is verified by the comparisons with the specification results of high-strength concrete filled steel tube columns under reciprocating tension and compression loading.