Plastic stress distribution method for predicting interaction strength of steel-concrete composite cross sections

Steel-concrete composite columns are efficient structural members that possess significant strength, stiffness, and ductility. Accurate methods of assessing the strength of these members are necessary to realize their benefits. Several design codes rely on the plastic stress distribution method for computing the cross-sectional strength of composite columns subjected to axial compression and flexural bending. However, there has been limited validation of this method over the wide range of material properties, cross-sectional geometries, and loading conditions to which it is permitted to be applied. This paper presents a study of the behavior of short composite columns and methods of evaluating their strength. The use of the plastic stress distribution method and the strain compatibility method to evaluate the strength of composite columns is validated against detailed fiber cross section analyses and published experimental data. The results of this study indicate that the plastic stress distribution method can yield significantly unconservative strength predictions, especially for encased composite members with high steel yield strengths and high steel ratios. Motivated by these results, a simple modification factor which can be applied to the results of the plastic stress distribution method to achieve greater accuracy was derived. This modification factor is suitable for use in design practice and enables better predictions of the strength of short composite columns. (C) 2020 Elsevier Ltd. All rights reserved.