Analysis Of Suspendome Under Fire During Heating And Cooling Phase

The suspendome structure is composed of the upper single-layer lattice shell and the lower support system.It has high efficiency in force transmission mechanism.Compared with the cable dome,the construction difficulty is low and the stiffness is large.So it has been widely used.Suspendome structure is generally a large-space building.If a fire breaks out,its characteristics will be significantly different from ordinary indoor fires.High stress and uneven temperature field will reduce the prestress of cable members,redistribute the stress of lattice shell,reduce the structural stability,and even lead to the overall collapse.Therefore,the traditional fire-resistance design method based on standard fire is not suitable for large space suspendomes,and performance-based fire-resistance design is needed.When the fire scale is small,the structure may not be significantly damaged,but the stress of the cable and the structural form will change to different degrees.In this case,it is necessary to research the whole process of the structure being exposed to fire and the mechanical performance after the fire,so as to provide technical support for the evaluation of the structural performance after the disaster.In this paper,the method of combining experimental research with finite element simulation is adopted.Based on the concept of performance-based design,the research was carried out on the properties of structural steel and prestressed cables during heating and cooling,the temperature field of large space domes in the whole process of natural fire,and the mechanical response of the suspendome structure under fire.The main research contains and achievements are as follows:（1）On the basis of the relevant literatures on material properties of prestressed cable under and after high temperature,the material properties of steel wires(f_ptk=1670MPa,φ=7mm)were tested at 20℃～700℃for heating and cooling.The curve was used to fit the mechanical parameters of the steel wire,such as elastic modulus,ultimate strength and nominal yield strength with the temperature variation of the heating and cooling section respectively,and the fitting effect was good.The constitutive model of the heating and cooling section was proposed.The high temperature material model of structural steel was determined by comparing the relevant literatures and codes at home and abroad.（2）The characteristics of natural fire in large space,the design method of fire scene and the setting of key parameters of FDS were briefly summarized.FDS was used to simulate the whole process of fire development in the suspendome building in large space,and different fire scenarios were established.The influences of building height,ratio of structure span,heat release rate of fire source and location of fire source on air temperature field of large space suspendome were summarized.（3）The finite element analysis software ANSYS was used to establish the structural model of the suspendomes,considering the initial imperfection.The air temperature field was converted into the temperature field of structural members by the calculation formula.The mechanical response in the whole fire process was analyzed.Then,the influence of load ratio,heat release rate,location of the fire and rise-span ratio on the deformation and stress of the suspendome during the whole process of fire was analyzed.