The Behavior Of Portal Frame Structures During Fire Fighting

The portal frame structure is widely used in various types of buildings such as industrial plants,warehouses and supermarkets due to its advantages in comprehensive economic benefits.Significant loss of human life and property will be caused once tthe structures are collapsed in fire.In the process of fire extinguishing,The structure is partially cooled,then the additional stress is produced under the constraint condition,which causes the stress redistribution in the whole structure,and this may lead to structural damage.At present,the fire resistance analysis of the portal frame structure mainly focuses on the temperature rising stage,and the research on the damage caused by fire cooling is few.The spatial and temporal distribution of the temperature field in the fire-fighting process of the portal frame plants are investigated,and the fire response of the single planer portal frames are studied using the numerical simulation method.The main research content of this paper is as follows:(1)On the basis of full review of the literature and reliable verification,the fire model for fire protection of portal frame structure factory buildings are established using FDS.Then the spatial distribution and evolution of the inside of the portal frame plant are studied by using the parameters such as the average heat release rate of combustibles,the time and position of fire intervention,etc..Besides,the temperature gradient distribution characteristics of the steel beam are also analyzed.(2)The finite element software ABAQUS is employed to establish the plane portal frame models.The temperature field of the plane portal frame structure obtained by FDS is introduced into ABAQUS with transient thermal analysis,the temperature distribution and the variation curve of thecomponents under various fire conditions are obtained.The temperature of the components at different times obtained is applied to the structure in the form of loads for thermal-mechanical coupling analysis.Then,the response of the portal frame structure during the fire cooling process and the influence of various parameters are analyzed.The analysis results show that,during the process of fire extinguishing,stress redistribution will cause in the portal frame structure due to local cooling of the components,which can cause structural collapse in severe cases.Therefore,it is necessary to prevent structure from collapsing due to water spray during the fire-fighting process.