Research On Performance Of Resistance To Fire For Steel Frame Based On FDS

Generally speaking, the traditional design of resistance to fire on structure applies ISO834 standard warming up curve as environmental temperature, however, the practice proves that different fire sites have different warming up curves and sometimes there are huge difference. At present, the steel structure design of resistance to fire still utilizes the component design method of resistance to fire based on experiment. This method has many advantages such as simpleness, direct-viewing, convenience and so on, but there are still have some shortages. Several years' practical application shows that the method has a few disadvantages in theory, but the calculation for steel structure limit bearing capacity of resistance to fire can solve this problem well. It is necessary to develop profound research on the steel structure design method of resistance to fire based on calculation under the condition of true fire situation, and this research can provide important theory on resistance to fire and have engineering values. Based on consulting lots of documents, this paper has completed some research as follows.1) According to the design idea of resistance to fire on architectural performance, this paper performs the analysis and computation of fire duration in a certain fire site, at the same time, carries out the analysis of resistance to fire in the duration period.2) The fire simulation software (FDS) is used to calculate the practical warm up curve of air when a fire breaks out, and this curve is considered environmental temperature in structural analysis and compared with ISO834 standard warming up curve.3) Under the case of two sorts of warming up curve, the finite analysis software (ANSYS) is used to compute the temperature distribution of component section fired.4) Under the condition of practical warm up curve, the software (ANSYS) is utilized to analyze the couple of thermal-structure on steel frame structure. The paper examines the time of resistance to fire and limit temperature on structure and fired component in different load ratio, studies the responses of fired and unfired components based on temperature effect and judges weak part in structure of resistance to fire.The results show that, environmental temperature is confined by many factors, and the structure calculation of resistance to fire sometimes has large difference under the condition of applying ISO834 standard warming up curve uniformly and it can't truly reflect structure response of resistance. Because of the influence of beam catenaries effect, the plastic area in fired end of beam increases with the rise of temperature, but the plastic area will reduce when the temperature arrive at some value. The unprotected steel frame's performance of resistance to fire is much better than component. When a fire breaks out, under the action of high temperature, not only the stress of fired components is been influenced greatly, but also the stress of unfired components has a huge alteration.Through the response analysis of steel frame in resistance to fire, this paper provides reference for future research on resistance to fire in steel structure.