Study On Fire Resistance Of High Strength Steel Beams

In modern times, high strength steel has been widely used in the design of high-risebuilding structure and large-span structure. At the same time, the high-strength-steelstructure suffers from a major drawback with poor fire resistance which has not beenresolved yet. After fires with heavy losses occurred in Shanghai and Beijing, fireresistance for steel structure has been paid more and more attention specially and wehave to find ways of overcoming the weakness. Therefore, aiming at the basiccomponents of high-strength-steel, the study on fire resistance performance has theimportant theoretical significance and engineering practical value.In this dissertation, we pay more attention to the fire resistance of flexural designmember made of high-strength-steel Q460. According to the sectional temperaturedistributions of the steel member at elevated temperature with finite difference method,this paper gives the temperature correction formula. Based on the previous experimentresult for the mechanical properties at elevated temperature, equivalent stiffness methodwas adopted by considering the influence of temperature gradient. Lateral torsionalbuckling resistance, critical temperature and stability factor were obtained whenhigh-strength-steel subjected to bending at elevated temperature.By the comparison of fire resistance between high-strength-steel beams and mildsteel beams with critical stress method, we get their differences on the lateral torsionalbuckling resistance and other aspects. The calculation result shows that the differenceson fire resistance are obvious between high-strength-steel and mild steel.Through building the member model, the fire resistance of the flexural memberwas analyzed with finite element analysis software—ANSYS. Then analysis results andtheoretical results are compared clearly and their agreeableness is good. Therefore thefire resistance calculation results for high-strength-steel beam were validated byconsidering the influence of temperature gradient.Finally, according to the theoretical calculation and finite element analysis, thesimplified design method of flexural member is proposed for fire resistance design ofhigh-strength-steel structure, and it can provide reference to engineering design.