Residual mechanical properties of Q890 high-strength structural steel after exposure to fire

Q890 high-strength structural steel has a promising application in engineering structures. However, little research has focused on its post-fire residual mechanical properties, which restricts its application extent. The present study aims to investigate the residual mechanical properties of Q890 high-strength quenched and tempered (QT) steel after exposure to fire. A series of experimental tests are conducted to obtain the post-fire stress-strain curves and microstructures of Q890 steel, considering the influence of temperature (room temperature to 1000 °C) and cooling methods (cooling in air and water). The residual elastic modulus, yield stress, ultimate tensile strength, ultimate strain, and microstructures were analyzed and discussed. A comparison of residual mechanical properties between Q890 steel and other high-strength QT structural steels was performed. Experimental results show that the post-fire mechanical properties are significantly dependent on temperature and cooling methods. Finally, empirical equations are proposed to predict the residual mechanical properties of Q890 steel, providing a basis for evaluating the post-fire performance of steel structures.