The Anslysis Of Temperatuer Field And Mechanical Properties Of Steel Frame Structure In Fire

Steel can be applied to many different kinds of high-rise and large span structures due to its advantages such as the high strength,the light weigh,the great plasticity and toughness.With the development of steel structures,the fire resistance ability of steel frame is increasingly paid more and more attention.However,because of the high experimental expense and the limitation on the test equipment,the experts at home and abroad put their attention to the data simulation and make research for thirty years.During the time,they come up with many valuable design method and analysis ways.The research on the fire resistance of steel frame is started relatively late in our country,which gain some valuable design theories,among which is a widely used code called《Technical Code For Fire Safely Of Steel Structure In Building》.It proposed to some fire resistance methods based on the fire resistance limitation about construction members.Although this method is simple and pragmatic,it needs large numbers of steel and increases the cost because the method is conservative.so it is not applicable.The behavior of steel frame under fire can be simulated completely through the numerical method at present.Through the contrast between the domestic and foreign methods,the method by coding is too trivial to discover the mistakes,which leads to the misconvergence in calculation,To solve those problems,the constraint equation is automatically established by CERIG,which can not only simulate the rigid connection between 3D solid elements and 3D beam elements,but also can reduce mistakes,and improve the speed and accuracy of calculation.The above method is used to do the following research:1.Summarize and induce the provisions of various countries,including physical and mechanical parameters,such as the coefficient of thermal expansion,the heat conduction coefficient,the specific heat,the density,in addition to the yield strength,the modulus of elasticity,the constitutive relationship of steel,the Poisson’s ratio.Select the suitable and appropriate parameter values according to the actual situation of the steel frame structure.2.Firstly,the model of the plane steel frame structure under the temperature and static load are established with using of large-scale finite element software ANSYS.The ISO834 standard fire temperature-rise curve is applied in the environment.Based on this,the typical fire scene of steel frame structures are simulated according to the selected physical parameters.Thus the internal temperature field of structures is calculated and obtained.Subsequently,the static structure field of steel frame structures based on practical staticload and the weight of the structure itself is calculated by ANSYS progress.Finally,the temperature field of steel frame structures was put into the structure progress by the coupling progress of ANSYS to obtain the respond of mechanics,refractory time and temperature of the steel frame structures.After that,the parametric study analysis was carried out to determine the effect of fire scene,intensity of steel,stress ratio on the deformation and internal force of plane steel frame structure during overall fire process of heating.3.After the thermal-stress analysis of the plane steel frame structure,the model of the space steel frame structure was built to analyze the mechanical response of the whole structures under different fire scenarios by the software ANSYS.Meanwhile,the deformation and internal force of structure under the plane and space steel frame structure were compared to obtain the fire-resistance time and temperature of the steel frame structures.