Residual Mechanical Properties of Q345FR Steel Exposed to High Temperatures

Steel structures used in engineering projects and infrastructure should withstand high loading capacities with excellent resistance to fire. A new Q345 fire-resistant (Q345FR) steel has been recently developed in China. The residual mechanical properties of steel structures are critical indicators for assessing structural damage and reusability, so in-depth research is urgently needed. Considering temperatures ranging from room temperature to 900 °C, as well as air and water cooling methods, the residual elastic modulus, yield stress, ultimate tensile strength and ultimate strain were explored. Comparison of the residual mechanical properties of Q345FR steel with other structural steels confirmed their close relation to temperatures and cooling methods through testing. The loss of its mechanical properties could be ignored when the temperature is up to 600 °C and the aforementioned cooling methods are used. When the temperature is above 600 °C, the exposed temperatures and cooling methods impact the residual mechanical properties of Q345FR steel significantly. Q345FR steel boasts the comprehensive advantages of excellent strength, high ductility and fire resistance. The prediction equations are offered for predicting such properties of Q345FR steel to accurately evaluate its residual mechanical properties exposed to high temperatures.