Postfire Residual Capacities of Aluminum Alloy Unequal-Leg Angle Sections

This paper presents the laboratory testing, numerical modeling, and structural design of aluminum alloy unequal-leg angle sections after exposure to fire. A testing program was carried out which included heating tests, postfire material tests and unequal-leg angle stub column tests. Eight different levels of elevated temperature exposure were considered ranging from 25°C to 550°C. The testing program was supplemented by finite-element analysis, in which numerical models were developed to simulate the postfire behavior, and the test results were adopted to validate the modeling approach. Then parametric studies were conducted to develop a deeper understanding of the influence of a number of important parameters on the postfire behavior. The experimental and numerical results were compared to various international design codes, and the continuous strength method, the latter of which is the only method which accounts for the effects of strain hardening in the material in the capacity predictions. The results from the design analysis indicate that the existing international standards generally yield underpredicted postfire capacities for aluminum alloy unequal-leg angles after exposure to elevated temperatures, especially between 300°C and 550°C. The continuous strength method was shown to offer significant design improvement over the examined international codes for the postfire design of aluminum alloy unequal-leg angles, especially for stocky angles, mainly due to the consideration of postfire strain hardening.