Reduction model of hot- and cold-rolled high-strength steels during and after fire

There is an increasingly booming demand for hot- and cold-rolled high-strength steels in building construction. Their material properties have been determined using numerous tests under fire conditions, based on which, however, their reduction factors show a high scatter between different previous tests, thus there is a significant lack of knowledge about the fully fire-induced behaviour of high-strength steels. Accordingly, this paper compares the behavioural differences caused by hot- and cold-rolled procesrses according to a consistent database and then demonstrates the admissibility of the existing reduction models of mild steels for high-strength steels with various steel grades. Consequently, reduction factors of cold-rolled high-strength steels behave at a more dramatically downward trend than those of hot-rolled ones, and their reduction factors do not increase with the upgrading of steel grades. Given the codified reduction models restrictedly valid for high-strength steels and limited to very specific tests without response to a consistent dataset, the statistically proposed reduction models with a lower confidence interval of 95% are recommended for high-strength steels during or after fire, thus implying that the newly proposed reduction models have improved markedly over the existing ones, the accuracy of which can guarantee fire resistance safety without being too conservative.