Safety Evaluation Method For Components Of Prestressed Steel Truss Under High Temperature (Fire)

Under the background of the great development of urbanization in China,the proportion of steel structure buildings in urban buildings is becoming higher and higher.Over the past 20 years,Chinese steel production has increased in a straight line,and the production of China’s steel is now at the top of the world.Compared with other materials,the main advantages of steel are energy saving,light weight and fast construction speed.At present,the steel structure is still based on fire protection design,and the behavior of steel structure in fire is not well incorporated into the design.Although the steel structure fire prevention specification is drawn up,there is still a lack of sufficient research results to support it.There is no guarantee that the designed steel structure has good fire resistance,moreover,the fire resistance of prestressed steel truss is especially prominent.In view of the shortage of fire resistance of prestressed steel truss structures,the failure of members under fire will result in serious consequences of overall truss structure performance.Therefore,the research on safety evaluation of prestressed steel truss structures under thermal coupling has been one of the key points in steel structure engineering research.There are few research results on safety evaluation methods of steel structure buildings at high temperature at home and abroad,it mainly focuses on steel frame structure and steel structure workshop,but no system theory is applied to actual engineering,in general,technical personnel in the fire site investigation,through the standard specifications and structural characteristics of the value of statistical identification.Therefore,the conclusion of safety assessment depends on the level and experience of professionals,this development is contrary to the present steel structure theory and investigation research.In this paper,the following research work has been done on the above issues:(1)Based on steel truss fire resistance design requirements,the model is calculated by the proposed pre-stressed steel truss,the bearing capacity of steel truss and prestressed steel truss in normal temperature and high temperature is analyzed by theoretical calculation formula,at high temperature,the bearing capacity of the component is reduced greatly.(2)Using ISO834 standard heating curve,selecting steel characteristic parameters at high temperature,after taking the number of the prestressed steel truss all components in turn,using the finite element numerical simulation software,study onthermo-mechanical coupling of prestressed steel truss members with reference to geometric nonlinearity of materials,analysis of the prestressed steel truss stress after fire,and obtain the stress distribution of steel members.Through statistical analysis:in case of fire,the change of the upper chord member in the fire is especially obvious,as the most unfavorable component.(3)Collect the literature under the high temperature of steel structure(fire),based on the fire resistance analysis of steel structures at home and abroad,the stress characteristics of steel structures in fire environment and the safety evaluation after fire are studied.On the results of previous analyses,the detailed steps,types and quantity of combustible materials are summarized,the calculation of fire load density of various building types,the method of determining fire burning time and fire temperature and the method of determining fire surface temperature of truss members are summarized,and the bearing capacity of truss is calculated.In the process of above analysis,the basic procedure for evaluating the safety performance of prestressed steel truss under high temperature(fire)is constructed,Based on the strength and deformation of the component to determine whether the component need to reinforcement,to avoid blind reinforcement,and keep safe.Safety evaluation and analysis method of prestressed steel truss members under high temperature(fire),it is expected to provide some technical suggestions for post-fire safety evaluation and reinforcement of steel structures in the future.