Response Analysis Of Portal Frame Structure Under Whole Fire Process Based On Field Simulation

The light portal frame structure is widely used in production plants,storage warehouses,wholesale markets and other buildings in China.However,fire is considered to be the biggest threat to the structure.Because common structural steels lose most of their strength and stiffness beyond a certain temperature,causing structural damage and even collapse.At present,most of the fire-resistant design for steel structures is for the small space,and the uniform temperature field distribution is based on the ISO834 standard heating curve.However,the temperature field of large space steel structure is non-uniform distribution.Therefore,it is necessary to study and analyze the displacement,deformation and internal force response of the structure under the action of the whole process fire.This article selects a plane rigid frame and three span rigid frame structure with a secondary structure in the “Light-Weighted Steel Portal Frame” and uses the shell element for numerical simulation under the whole fire procee.The main contents of this paper focus on the following aspects:A summary of the characteristics of large-scale building fires,the determination of various parameters in the process of fire,the use of fire dynamic analysis software FDS analysis of the spatial temperature distribution in different fire scenarios The physical and mechanical properties of structural steels under high temperature suitable for this study are selected through comparison of domestic and foreign specifications.The finite element software ABAQUS is used to analyze the heat transfer of the rigid frame,and the temperature field distribution of the components is obtained.The results show that the change of temperature along the cross-section gradient is very small,and the temperature of the cross-section measuring points is very close to the corresponding air temperature.Therefore,it can be simplified to represent the cross-section temperature with the air temperature under the effect of fire.Through numerical simulation and comparison of existing experimental results,it was verified that ABAQUS can use thermo-mechanical coupling analysis to accurately analyze the response during structural fires.On the basis of considering material nonlinearity and geometrical nonlinearity and non-uniform distribution of spatial temperature field are taken into consideration,the response of plane portal frame during the whole process fire under the action of the numerical simulation of five different factors The results show that the different fire scenarios different protective layer parameters,different span three factors directly affect the distribution of component temperature field,the horizontal load is very easy to cause the whole frame due to excessive lateral displacement and instability of member fire resistance is extremely unfavorable,column rigid increase of structural redundancy,relative to the column foot hinge can prolong the structure failure time.Three span rigid frame structure with a secondary structure as the overall study object.The load design values are applied to the rigid frame.The nonlinear and geometric nonlinearities of the material are considered to study the deformation and displacement response of the space frame in different fire scenarios.Results show that the spatial rigid frame has good collaborative constraint function.in temperature rising stage,Spatial structure can effectively reduce deformation magnitude,but the traction generated by the thermal expansion of secondary structures such as purlin,wall beam and rigid tie bar has a great influence on the main frame out-of-plane deformation,causing frame above the out-of-plane instability destruction,while the plastic development of the rigid frame is more noticeable.Therefore,it is necessary to strengthen the secondary components in the fire resistance design of the spatial structure.