Analysis About The Response Of Square Pyramid Space Truss During Overall Fire Process Of Heating And Cooling

In this paper, the finite element method and numerical simulation tools are used to study the temperature field and mechanical response of square pyramid space truss in the fire process. According to the results of the analysis, putting forward some proposals about fire resistance design and strengthening of structure when structrure do not produce serious damage or collapse. The main work done in this paper is as follows:(1) Study on the mechanical properties of the steel materials during the whole process of the fire temperature rise and drop temperature. In the light of the mechanical properties of the steel during the whole process of fire temperature rise and drop, the research compares the existing representative theoretical model and selects the suitable structural steel material model of high temperature. Based on the assumption of the material properties linear cumulative damage under fire, put forward the calculation formula of cooling material properties of Q235 steel in the fire.(2)Research of structure internal temperature field distribution.Considering the characteristics of large space fire temperature field distribution is not uniform, Comprehensive analysis of large space fire heating Li Guoqiang experience formula and the ISO834 standard fire temperature formula,an thermal analysis program is composed for analyzing the temperature field of square pyramid space truss during the fire heating and cooling using the finite element method,getting the temperature distribution of square pyramid space truss under fire.(3) Structure mechanical response analysis in fire heating and cooling. A thermal-stress analysis program is composed for analyzing the square pyramid space truss mechanical response in the fire process using the finite element method. Considering material nonlinearity, geometric nonlinearity, the nonlinear temperature distribution, the support form of structure in analysis, getting the regularities of internal force, bearing force and displacement in fire heating and cooling when the structure in upper and bottom supporting.(4) The parametric analysis of the square pyramid space truss in upper supporting under fire.The parametric analysis was carried out to analyze the static loading ratio, the maximum temperature and span of the truss. The results show that the larger load ratio is, the more deformation of the structure is in the fire, the more residual deformation is when cooling to room temperature, the greater internal force of the bottom chord bar is; the higher the maximum temperature of heating, the more structure distortion in the fire,the larger residual deformation is. Under the same rigidity, the space span has little effect on the mechanical response of the structure in the fire process.(5) Basing on the mechanical response of square pyramid space truss in the fire process, some proposals about fire resistance design and strengthening of structure after fire.