Design Thickness Requirements for Hollow Structural Sections

Abstract

The Canadian design wall thickness requirements, t, for ASTM A500 hollow structural section (HSS) members is set at 0.90 times the nominal thickness, tnom. The American Institute of Steel Construction (AISC) specifies the same as 0.93tnom. This discrepancy gives rise to questions as to the economic sufficiency of the Canadian standard set by the Canadian Standards Association (CSA) and the Canadian Institute of Steel Construction (CISC). Dimensional data obtained from quality control records, field measurements, and the literature representing modern manufacturing practices for ASTM A500 HSS is compiled and used to compute basic statistics (i.e., means and coefficients of variation of actual-to-predicted cross-sectional area, moment of inertia, radius of gyration, elastic and plastic moduli). The forgoing statistics, combined with ASTM A500 HSS material property statistics, are used collectively to derive professional factors for modern CSA S16 design formulae. A reliability analysis is carried out to assess the level of safety obtained when using the currently prescribed design wall thicknesses and alternatives for ASTM A500 members in accordance with CSA S16.