Design of Class 4 hollow structural section compression members

Abstract

This paper presents a study on the CSA S16:19, AISC 360-16, and EN 1993-1-1 approaches to determine the nominal capacity (Cn) of Class 4 hollow structural section compression members. Class 3 limits and effective width (be) equations are compared, and the effect of member slenderness (KL/r), width-(or diameter-)to-thickness ratio, and height-to-width (or aspect) ratio on the relative Cn predictions are evaluated. For Class 4 rectangular hollow sections, CSA S16:19 is shown to under-predict Cn by up to 34% relative to AISC 360-16. A more economical, yet still safe, method to calculate be (and hence, Cn) is proposed. For Class 4 circular hollow sections, a new method to calculate Cn utilizing the “effective area method” is proposed. This new method removes the need for having an “effective yield stress method” in CSA S16 Clause 13.3.4.