Behaviour of cold-formed steel RHS members under cyclic loading

Technical Abstract

Three steel members and a stub column made from cold-formed rectangular hollow sections (RHS) were tested under cyclic axial tension and compression loading. The section tested was a 150 x 100 x 6 RHS with a specified yield stress of 350 Mpa. Three different overall slenderness ratios were tested, 40, 60 and 80. Pin ended and fixed ended connections were tested. It was found that local buckling occurred relatively quickly and that the magnitude of the local buckles increased under repeated loading. Eventually this led to fractures developing at the sharp local buckles giving reduced ductilities. The ratio of the width to the thickness for the element of a cold-formed section allowed by NZS 3404 steel structures standard may need to be reduced, where high ductility is required for design against earthquakes.