Post-fire mechanical properties of YSt-310 cold-formed steel tubular sections

An experimental programme to study the residual mechanical strength of Tata Structura-YSt 310 cold-formed steel square and rectangular tubular sections (conforming to Indian Standard 4923) after being exposed to elevated temperature is described in this paper. First, the coupon specimens extracted from the flat regions are exposed to pre-determined elevated temperature in the range similar to 300-800 degrees C, arid then the residual mechanical properties and hardness value were estimated at ambient temperature after natural air cooling. The results from the experimental programme are reported in this paper in the form of post-firestress-strain curves and associated basic material properties (e.g. elastic modulus, proof stresses, tensile strength, percentage elongation at fracture, Ramberg-Osgood material parameters etc.) as well as surface hardness values, The test results showed that most post-fire mechanical properties are appreciably different from ambient temperature material properties when exposed to a temperature higher than similar to 400 degrees C; whilst elastic modulus appears to remain unaffected even when the exposed temperature is up to similar to 800 degrees C. A near linear relationship of post-fire material strengths and hardness value was observed. Two sets empirical equations are proposed separately to predict the residual post-fire reduction factors based on the i)current experimental results of Tata Structura-YSt 310 cold-formed steel, and ii) cold-formed steel of various grades presently available in the literatures. (C) 2018 Elsevier Ltd. All rights reserved.