Experiment of ductile fracture performances of HSSS Q690 after a fire

In this study, a total of 26 tests were conducted to investigate the post-fire properties of high strength structural steel (HSSS) Q690, including mechanical properties and ductile fracture properties. The purpose of this experimental study is to evaluate the residual properties of the HSSS Q690 after a fire. Tensile coupons obtained from the HSSS Q690 sheets were heated to various temperatures up to 900 °C, and then were cooled down in furnace to ambient temperature. Tensile coupon tests were carried out to obtain their post-fire nominal stress-nominal strain curves, post-fire true stress-true strain curves, corresponding mechanical properties (including yield stress, ultimate strength, Poisson's ratio, elastic modulus and elongation), and ductile fracture behaviors. Test results showed that the HSSS Q690 can keep the unchanged mechanical properties after it experiences temperatures up to 600 °C. And then two sets of prediction equations (one set of equations only based on test results in this study, and another set of equations based on test results of previous studies and this study) are obtained to evaluate the post-fire properties of HSSS. The results presented in this experimental study are expected to lead to accurate assessing the post-fire properties, including mechanical properties and ductile fracture properties, of the HSSS Q690.