Mechanical properties and creep strain of Q355 cold-formed steel at elevated temperature

Abstract

This paper aims to investigate the mechanical properties and thermal creep of Q355 cold-formed steel (CFS) through tests. The yield strength, ultimate strength, and elastic modulus of the steel at elevated temperatures were obtained through steady tensile tests. The thermal creep tests were conducted in the temperature range of 450 °C to 750 °C under four different stress ratios, and creep strain versus time curves were obtained. To assess the difference of creep behaviour between CFS and virgin steel, the test results were compared with that of the Q355 virgin steel sheet available in the literature. It was found that CFS was more susceptible to the thermal creep, and its creep strain rate was at least twice that of the virgin steel at the same condition. The test results were fitted into a creep model and incorporated into a numerical simulation to reproduce fire tests of the CFS columns conducted in transient-state temperature with different heating rates. The simulation results demonstrated that the models with considering of creep provided better predictions on fire behaviour of the column than those without accounting creep, and the creep could significantly reduce the fire-resistance of CFS columns.