A distributed plasticity model for cyclic analysis of concrete-filled steel tube beam-columns and composite frames

Abstract

This paper presents the constitutive formulation and cyclic analysis capability of a three-dimensional fiber-based distributed plasticity finite element for square or rectangular concrete-filled steel tube (CFT) beam-columns. A related paper outlines the geometrically nonlinear formulation and the element's formulation for interlayer slip between the steel tube and concrete core. The present paper discusses the steel and concrete cyclic material models, which are each based on stress-space bounding-surface plasticity formulations. The paper details the calibration of these models to steel coupon tests and to experiments of short CFTs in flexure which yield moment-curvature-thrust results. Verification of the model is provided by comparing to several experiments of CFT beam-columns loaded monotonically and cyclically, proportionally and nonproportionally, and in single and reverse curvature. A final example presents a comparison of the analysis to the experimental results of a composite subassemblage consisting of three steel I-girders framing rigidly into a CFT beam-column, which is thus subjected to axial force plus cyclic biaxial bending.