Reliability of Existing and Proposed North American Design Provisions for RHS Compression Members with Slender Elements

Abstract

Design provisions for axially compressed rectangular hollow section (RHS) members with slender elements were evaluated using an approximate first-order reliability method analysis. A total of 342 nonlinear finite-element models, covering a range of width-to-thickness, height-to-thickness, and nondimensional slenderness ratios, were developed and analyzed. Calculated ranges of reliability indexes (β+) were computed and compared with β+ values obtained from the expanded separation factor approach and with target values in codes. The results showed that the Canadian Standards Association (CSA S16:19) design provisions for locally slender RHS compression members are imprecise, resulting in underpredictions of column strength by as much as 22%. AISC 360-16 design provisions, and a recently proposed modified CSA approach were shown to be better predictors. Considering all 342 columns together, the current resistance factor of ϕ=0.9 was shown to be acceptable in both codes.