Effect Of Temperature Rise Rate On Fire Resistance Period Of Simple Supported Beam With Fire Coating

As one type of building structure, steel structure is wildly applied in project constructions because of its own superiority in all directions. But the poor fire‐resistant is a fatal weakness of it. At present, domestic and foreign scholars have carried out many studies on fire resistance and fire response characteristic of steel structure. Simple supported steel beam that commonly seen in structures is as the research object, This paper adopted the finite element analysis method, based on building and tunnel fire curve, discussed the effect of temperature rise rate to fire resistance period of simple supported beam with thick‐layered fire coating. The main contents include:(1) This content analyzed the effect of temperature rise rate on fire resistance period of simple supported steel beam with fire coating. According to the difference on temperature rate of building and tunnel fire, based on ISO standard fire curve, hydrocarbons HC and RABT fire temperature curve. The paper analyzed the thermal‐structure‐coupled stress field under three different fire conditions. Simulation and theoretical calculation on temperature field of steel beam were compared, in order to verifying the finite element model of the simple supported steel beam reasonable and feasible.By the thermal‐structure‐coupled analysis of the protected simply supported steel beam under different fire temperature rise rate, the results indicate that temperature rise rate of fire is an important factor on the fire resistance period of steel beam. Under the high speed fire, the steel beam temperature quickly rose to fire‐resistant critical temperature, and displayed larger temperature distribution difference on its cross section. This lead to the failure on steel carrying capacity due to a sharp drop in strength, therefore the fire resistance period of steel beam is shorter. But the fire‐resistant critical temperature was basically agreed in the same load ratio.(2) Under the conditions of the three kinds of temperature rise rate which has been mentioned above, through the use of different thickness of thick‐layered fire coating, the temperature of steel beams variation with time has been studied. According to the theory that the same load ratio leads to the same fire‐resisting critical temperature of steel members, the fire endurance corresponding to different thickness of thick‐layered fire coating has been obtained. The results showed that increases the coating thickness can effectively extend the fire endurance of steel beams. Comparatively, the improvement of fire endurance under the slow temperature rise rate is more significant.(3) Based on the natural temperature curve BFD closer to nature fire, the paper take a specific room as an example, set two kinds of natural temperature curves at different temperature rate on basis of the fire growth coefficient, and analyzed the influence of the fire‐protected simply supported steel beam by fire temperature rate under equal fire conditions. It also revealed that steel beam has a shorter fire resistance period under high speed fire temperature rate.In a word, fire temperature rate, thickness of the fire coating are all the important factors that affect the fire resistance period of steel components, this paper, through analysis of fire resistance period of the fire‐protected simply supported steel beam at different fire temperature rate, aimed to provide certain reference for the fire resistant steel structure design and calculation of the fire coating thickness under different fire scenarios.