Experimental study of ferritic stainless steel tubular section beam-columns subjected to moment gradients

This paper presents a comprehensive experimental study of the buckling behaviour of ferritic stainless steel tubular section beam-columns subjected to unequal end moments. The experimental investigation included material tensile coupon tests, initial geometric imperfection measurements and twenty-four beam-column tests under unequal end moments. The experimental results were carefully analysed and then compared with the design strength predictions determined from current international design standards, enabling the accuracy of each codified method to be evaluated. Generally, the European code resulted in the most conservative and scattered strength predictions, 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 effect 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.