Experimental study on post-fire mechanical properties of high strength Q460 steel

In order to evaluate the residual strength of high strength Q460 steel structures after fire, an experimental study was undertaken to investigate the post-fire mechanical properties of high strength Q460 steel. Tensile coupons taken from high strength Q460 steel sheets were exposed to different temperatures up to 900 °C, and were then allowed to cool down to ambient temperature before they were tested to failure. Two cooling methods were considered, namely; natural air cooling and cooling by water. Tensile coupon tests were conducted to obtain their post-fire stress-strain curves and associated mechanical properties (yield strength, elastic modulus, ultimate strength and elongation). It was found that the post-fire mechanical properties of high strength Q460 steel are significantly reduced below the original ambient temperature mechanical properties if they had been exposed to temperatures exceeding 600 °C. Hence a new set of equations is proposed to predict the post-fire mechanical properties of high strength Q460 steel. Such post-fire mechanical property assessments allows structural and fire engineers to make an accurate prediction of the safety of fire exposed high strength Q460 steel buildings.