Experimental Study of Ferritic Stainless Steel Tubular Beam-Column Members Subjected to Unequal End Moments

Abstract

This paper presents a comprehensive experimental study of the buckling behavior of ferritic stainless steel tubular section beam-column structural members subjected to unequal end moments. Testing was carried out on two cold-formed and seam-welded cross sections—one rectangular hollow section (RHS) 100×40×2 and one square hollow section (SHS) 60×60×3 made of grade AISI 410 (EN 1.4003) stainless steel. The experimental investigation included a series of material tensile coupon tests, initial local and global geometric imperfection measurements and 24 beam-column tests under unequal end moments. The experimental setup and procedures are described, and the test observations, including the key test results, the load-deformation histories, and the failure modes, are fully reported. The experimental results were carefully analyzed and then compared with the design strength predictions determined according to the current European code, American specification, and Australian/New Zealand standard for stainless steel structures, enabling the accuracy of each codified method to be evaluated. Generally, the European code resulted in the most conservative and scattered strength predictions among the three codified approaches, owing principally to the use of the same treatment for stainless steel beam-columns under both equal and unequal end moments. The American specification and Australian/New Zealand standard employ an equivalent uniform moment factor to consider the beneficial effects of moment gradient on beam-column strengths. These approaches were shown to offer more accurate and consistent capacity predictions for ferritic stainless steel beam-columns under unequal end moments, though further improvements remain possible.