Residual mechanical properties of stainless steels S30408 and S31608 after fire exposure

With excellent corrosion resistance and appearance, stainless steels have been widely used in building structures. Although fire accidents in steel buildings have happened occasionally in recent years, only few steel structures have collapsed entirely and most can still be used after reasonable assessment, repair, and reinforcement, thus reducing economic losses of fire accidents. The post-fire mechanical properties of stainless steels are the key parameters in the process of structural assessment after a fire. In this paper, the effects of exposure temperature, exposure duration, and cooling mode on mechanical properties of common stainless steels S30408 and S31608 were studied through experiments. The following conclusions were obtained: 1) when the exposure temperature is lower than 1000 °C, the post-fire ultimate tensile strength, rupture stress, and post-fracture elongation of S30408 and S31608 have little weakening; 2) When the temperature is lower than 1000 °C, the post-fire elasticity modulus of S30408 and S31608 increased to some extent, initially increasing then decreasing with exposure temperature increase, reaching the peak at 800 °C with an increase coefficient of about 50%. 3) The post-fire nominal yield strength of S30408 and S31608 decreased significantly, and when exposure temperature reached 1100 °C, the post-fire nominal yield strength of S30408 and S31608 decreased by about 30% and 20%, respectively. 4) Cooling mode (natural cooling in air and water cooling) and high temperature exposure duration (30 min and 180 min) had slight effects on the post-fire elasticity modulus, nominal yield strength, ultimate tensile strength, rupture stress, and post-fracture elongation of stainless steels.