Effect of material properties on hollow section performance

Abstract

Hollow structural sections for onshore steel construction are manufactured in diverse locations around the world, by either a hot-finishing or seamless process or – far more commonly – by cold-forming. The implications of using material by a particular process in various statically loaded or dynamically loaded applications are not fully appreciated. This paper hence reviews some of the key geometric and material properties that are inherent in several common hollow section production standards. Problems that have been encountered with certain cold-formed square and rectangular hollow sections, particularly with regard to hot-dip galvanising in North America and Asia, are elaborated. Besides galvanising, these same sections are now also subject to constraints for seismic applications. The difference in seismic performance between cold-formed, cold-formed and stress-relieved, and hot-finished hollow sections, when used as energy-dissipating members such as braces, has been a point of debate and speculation to date. An experimental project, in which the relative performance of each material type is evaluated by performing inelastic cyclic testing of large-scale tubular braces, is described, with comments on the suitability of various tube material types for concentrically braced steel frames under severe seismic loading. Considering all of these material and production issues, an industry-driven reappraisal of the cold-formed hollow structural section manufacturing specification in North America is being undertaken, which is also presented herein.