Mechanical properties of hot-rolled and cold-formed steels after exposure to elevated temperature: A review

•Post-fire behaviors of different grade hot-rolled steels and cold-formed steels are reviewed.•The varying trends of residual mechanical properties are explained from the point of microstructures.•Post-fire residual behaviors are compared between different steel grades and steel types.•Two universal predictive equations are calibrated for practical post-fire structural assessment. Due to the structural integrity and redundancy in structural design, a steel building may not collapse in a fire hazard. Then the residual mechanical properties of steel materials are important indexes to evaluate the postfire performance of the entire structure and the reuse of the steel members. Many studies have been performed to explore the postfire residual performance of different structural steels. However, the observed varying trends and proposed evaluation guidance are too specific and are different from each other. In this paper, existing postfire test data for hot-rolled steels and cold-formed steels are collected from an extensive literature survey. Statistical analyses on the effects of heating experience on the mechanical properties of steels are conducted. The influencing mechanisms are explained from the point of microstructure phase changes during and after the fire heating. The cold-formed steels exhibit a higher level of influence from the fire heating due to the release of cold-working dislocation. Two series of predictive models for postfire residual strength evaluation are calibrated, and they are highly universal and can be easily applied for the residual strength assessment of hot-rolled and cold-formed steels after a fire.