基于复杂应力状态的火灾后高强钢本构模型研究OA

Fire is a serious disaster threatening the safety of high-strength steel structures.After being exposed to fire,high-strength steel undergoes significant deterioration in its mechanical properties,and under complex stress states generated by external loads,it can even fracture and cause the collapse of entire structure.Therefore,it is particularly essential to accurately predict fracture behavior of high-strength steel.Use of a reasonable constitutive model is the basis for accurately predicting the fracture behavior of high-strength steel after a fire.In an addition,the proposed constitutive model should be applicable to different stress states.In this study,considering different stress states,Q690 steel smooth round specimens,notched round specimens,and grooved plate specimens are designed.They are exposed to high temperature ranging from 200 to 1000℃,and then cooled down using air-cooling and water-cooling methods,respectively.Tension tests are then conducted on these specimens to obtain their load vs.deformation curves.Based on the experimental data and finite element numerical analysis results,post-fire true stress-strain models of Q690 steel considering different stress triaxiality and lode angle parameters are established,and the post-fire fracture parameters are also calibrated in this study.The obtained true stress-strain model can accurately predict the performance of Q690 steel specimens under different stress states after fire.Using the calibrated fracture parameters,the fracture initiation of the specimens with different stress state can be reasonably predicted,which can provide an effective method for assessing the post-fire load and deformation bearing capacity of high-strength steel structures.