Study On Behavior Of Welded Hollow Spherical Joints After Exposure To Fire With Load

Welded hollow spherical joints have been widely used in space lattice structures.It is important to study the residual mechanical properties of welded hollow spherical joints exposure to fire with load for evaluating the mechanical properties of lattice structures after fire and reinforce them.In this paper,experimental and numerical studies were conducted to reveal the residual axial compressive bearing capacity of welded hollow spherical joints after fire exposure with load.The formula for calculating the residual axial compressive bearing capacity of welded hollow spherical joints after fire exposure with load is proposed.The main research work includes:Firstly,the residual mechanical properties of Q345 steel and welded hollow spherical joints after fire exposure with load were tested,and the mechanical properties such as proportional ultimate strength,yield strength and ultimate strength of the steel at high temperature and after high temperature with load were obtained.Twenty-three specimens of welded hollow spherical joints were processed for axial compression tests under high temperature and after high temperature with load,which considering factors such as types of steel,rib,temperature and residual deformation.The residual axial compressive bearing capacity of welded spherical joints under different working conditions was obtained.The influence of various factors on the residual axial compressive bearing capacity was preliminarily analyzed.Secondly,the finite element model is established by ABAQUS to simulate the axial compression process of welded spherical joints at high temperature and after high temperature with load.Compared with the test results,the finite element model is found to be accurate.According to the test results,suggestions are proposed to correct the finite element results.The parametric analysis of axial compressive bearing capacity and stiffness of welded spherical joints after high temperature with load is carried out,and the influencing trend of each influencing factor on residual axial compressive bearing capacity and stiffness is obtained.Finally,combined with the results of parametric analysis,the data of finite element analysis are further supplemented.ORIGIN software is used to fit the calculation formula of the influence of ribs on the residual axial compressive bearing capacity coefficient of joints of specific size.SPSS software is used to fit the formula of the coefficient of residual axial compressive bearing capacity of welded spherical joints after high temperature with load.Combined with the stipulation of the formula for calculating the axial bearing capacity of welded spherical joints under normal temperature in Technical Regulations for Reticulated Shell Structures,and considering certain safety factor and correction factor,the formula for calculating the residual axial compressive bearing capacity of welded spherical joints after high temperature with load is obtained.