Study On Fire Resistance Of Double-layer Spherical Reticulated Shell With Metal Roof

While large-span buildings meet the requirements of large spaces,they also have the advantages of light structure,beautiful shape,and reasonable stress.They are mostly used in the roof load-bearing parts of large public buildings such as stadiums,terminal buildings,and convention and exhibition centers.Metal-faced sandwich panels are widely used in building roof systems due to their light weight and convenient assembly.In the event of a fire,the fire resistance of steel is poor,unprotected steel components are easily damaged,and the structure may collapse as a whole.Therefore,as a large-scale public place where people gather,large-span buildings are very necessary to study the fire resistance of their overall structure,to grasp the impact of high temperature fire on the overall structure,and to provide suggestions for scientific fire-resistant design of the structure,so as to be effective reduce the loss of life and property caused by fire.Based on the above objectives,this paper analyzes and studies the mechanical properties of metal roof pyramid and cross-truss double-layer spherical reticulated shells under high fire temperatures.The main research contents are as follows:Firstly,the fire dynamics software FDS is used to establish the double-layer spherical reticulated shell structure model of the metal roof system,and the field simulation analysis obtains the air temperature field inside the structure under fire.The temperature time history curve of the reticulated shell node and the stable combustion stage of the fire field are different along the roof.The air temperature of the path varies with the distance from the fire source and the cloud diagram of the air temperature distribution on the roof.The influence of the fire source power,fire source location,structural span,rise-span ratio,building height and other parameters on the air temperature field under fire is analyzed.Secondly,based on the finite element software ABAQUS,the methods of constant temperature loading and constant load heating are used to analyze the transient response of the metal roof system pyramid and cross-truss double-layer spherical reticulated shell structure under fire.Source position,structural span,rise-span ratio,building height and other parameters affect the limit state of the structure.A characterization method for the fire resistance limit of the structure based on the limit displacement and the temperature distribution of the roof is proposed,and the judgment standard for the overall instability of the double-layer spherical reticulated shell structure of the metal roof is established.Finally,the double-layer spherical reticulated shell structure of the metal roof is studied considering fire protection measures,and the effects of smoke exhaust conditions and fire protection coatings on its fire resistance performance are analyzed.Studies have shown that: considering natural smoke exhaust and applying ultra-thin fire-retardant coatings,the metal roof double-layer spherical reticulated shell structure will not cause overall instability damage under fire.In the smoke exhaust design,priority should be given to the scheme of roof exhaust smoke dominant and high side window smoke exhaust synergistic.Among them,the smoke exhaust efficiency of the roof horizontal exhaust vent accounts for 80% to 90% of the smoke exhaust effect is the best.