Residual mechanical properties of high strength steels after exposure to fire

Abstract

This paper presents an experimental investigation on residual mechanical properties of high strength steels (HSS) after exposure to fire. A test program was conducted to study the post-fire mechanical properties of cold-formed HSS. A total of 41 tensile coupon specimens was extracted from cold-formed tubular sections with nominal yield stresses of 700 and 900 MPa. The specimens were exposed to various elevated temperatures ranged from 200 to 1000 °C and then cooled down to ambient temperature before testing. Stress-strain curves were obtained and the mechanical properties of Young's modulus, yield stress (0.2% proof stress), ultimate strength, ultimate strain and fracture strain of the cold-formed high strength steel materials after exposure to elevated temperatures were derived. The post-fire retention factors that obtained from the tests were compared with existing predictive equations in the literature. The influence of heating rate on post-fire mechanical properties was also investigated. New predictive curves for the determination of residual mechanical properties of HSS after exposure to fire are proposed. It is demonstrated that the proposed predictive curves are suitable for both cold-formed and hot-rolled HSS with nominal yield stresses ranged from 690 to 960 MPa.