Study On The Failure Mechanism And Safety Performance Of Steel Frame Structure At High Temperature (on Fire)

Steel structure has been rapidly applied in modern society due to light weight, high strength, short building cycle and other advantages. However the poor fire-resistance ability is the main weakness of steel structure. If steel structure is on fire, it will be seriously damaged or even collapsed because of the rapid decline in mechanical properties under the condition of fire. People's lives and property suffer huge losses. Steel structure exists obvious flaws in the security of structure precisely because of the characteristics of the poor fire resistance of steel under fire. So it is very necessary to study the failure mechanism of steel structure at high temperature.Based on previous studies, the paper studied the reaction mechanism of plane steel frame and steel members under fire by using finite element analysis software ANSYS. In this progress, the basic theories of fire science and engineering structure were applied in this study. Firstly, this article analyzed the temperature change rules of steel members' section and the destruction mechanism of steel frame under thermal-force coupling.Secondly, this thesis discussed the affection of the fire resistance of steel framework under different fire location. Thirdly, this paper explored the response characteristics of steel beam with fixed ends under different fire exposure cases. Lastly, this article summarized fire protection design methods in domestic or international and analyzed the distribution of temperature field of steel structure under the conditions of fire retardant coating and different fire exposure cases.Through the simulation analysis, the following conclusions are achieved.(1) The temperature distribution of steel frame under high temperature is very uneven. The temperature on the surface suffered fire is high, while the back surface is low.(2)Beam-column joints of steel frame are vulnerable to be damaged owing to complex stress condition and measures should be taken to strengthen protection.(3) Different fire locations have some certain effection on the response characteristics of steel frame. When the side span expose to fire, horizontal displacement at the top of the lateral column is larger than the medium span. However, the deflection of beam is smaller than the medium span exposed to fire.(4) Usually the steel beam is heated on its three sides, when fire break out. Temperature on the web and bottom flange of the beam rises rapidly, but the temperature on the top flange is very small.(5) The expansion of material at hightemperature has obvious influence on the stress of the steel members.(6) For steel beam fixed at both ends, when the ranges and areas exposed in fire are greater, the fire resistance time is shorter.(7) Compared with no fire retardant coating of steel members, the protection of fire retardant coating on the steel members is more significant and delay increasing rate of temperature of section.(8) Different fire exposure cases have great effection on the fire resistance of steel components. The greater the areas of the steel component subjected the fire are, the intenser the reaction of the component it will be.Hope that the study on the failure mechanism of the steel frame in fire(high temperature) and safety protection performance research through this paper can provide some beneficial research and reference for steel structure fire resistance.