Effect of temperature and cooling regime on mechanical properties of high-strength low-alloy steel

This paper presents results from experimental studies on the effect of temperature on mechanical properties of high-strength low-alloy ASTM A572 steel commonly used in structural members in bridges. A set of high-temperature tensile strength tests and post-temperature exposed residual strength tests is carried out on ASTM A572 steel coupons in 20-1000 degrees C temperature range. The residual strength tests on high-temperature exposed steel coupons are carried out after subjecting the coupons to two methods of cooling, namely, air cooling and water quenching. Results from these tests indicate that temperature-dependent strength and stiffness degradation in A572 steel follow the same trend as that of carbon steel but with some variations. A572 steel recovers almost 100% of its room temperature yield strength when heated to temperature up to 600 degrees C, regardless of the method of cooling, while the extent of strength degradation in coupons subjected to heating beyond 600 degrees C is dependent on heated temperature and method of cooling. Data generated in these tests are utilized to generate high-temperature stress-strain and residual stress-strain response of A572 steel. These results are also utilized to propose temperature-dependent strength, elastic modules, and residual strength reduction factors of A572 steel, which can be used in evaluating residual response of fire-exposed steel structures. Copyright (c) 2015 John Wiley & Sons, Ltd.