Study On Welded Hollow Spherical Joints Strengthened While Under Load

The space grid structure has been widely used in public buildings such as airports,railway stations,stadiums,etc.With the increase in the years of use,the structural bearing capacity is insufficient due to aging,disaster,and functional changes,so the research on the reinforcement of the space structure in service need to be improved.Welded hollow ball joints are one of the most popular nodes in space structure.At present,the research on the reinforcement method of welded hollow ball joints mainly focuses on the reinforcement after complete unloading,but the load consolidation problem is common in engineering practice,so it is necessary to load the working conditions.The method of strengthening the welded hollow ball joints is studied to meet the needs of actual engineering.In this paper,the mechanical properties of welded hollow spherical joints before and after reinforcement with extra-spherical ribs under axial force and the mechanical properties of welded ball joints under axial compressive stress are tested experimentally.The calculation formula of bearing capacity of welded and welded welded ball joints under load is studied.The main research work is as follows:Firstly,considering the rib reinforcement in the ball,whether the welded hollow ball is reinforced,and the load size during reinforcement,12 welded hollow ball joints are designed,and the axial compression test of the unreinforced ball,the zero-load reinforcing ball and the load-reinforced ball joint is obtained.The coefficient of axial bearing capacity of the welded ball joints under different working conditions is improved;8 welded hollow ball joints are designed considering whether the ball is ribbed or welded or not,and the unreinforced ball and the zero-load reinforcing ball shaft are pulled.In the test,the coefficient of improvement of the axial tensile capacity of the reinforced welded ball joint was obtained.Through the experiment,the basis for the verification of the finite element model is provided,and the influence of each factor on the bearing capacity after reinforcement is analyzed.Secondly,the finite element model is established by finite element software ABAQUS.The load reinforcement process and the axial compression and axial pull process under the axial compression of the welded ball joint are simulated.Compared with the test results,the finite element model is more accurate.According to the different initial load ratios,the axial bearing capacity of the welded hollow ball joints and the tensile bearing capacity after reinforcement are studied.Consider the width of the outer ribs,the ribs in the ball,the diameter of the welded hollow spheres,the ratio of the diameter of the spherical tube,Eight factors including hollow wall thickness,material type,diameter of steel pipe and outer rib plate arrangement are used to analyze the bearing capacity of welded ball joints after load consolidation,and the bearing capacity improvement coefficient and residual capacity of load-bearing bearing capacity are obtained.The influence trend provides a basis for the calculation of the welding reinforcement bearing capacity calculation formula under the load.Finally,the finite element analysis data is further supplemented by the results of parametric analysis.The residual coefficient of bearing capacity after welding ball reinforcement under different load ratios is obtained by ORIGIN software.The calculation formula of bearing capacity improvement coefficient after reinforcement is obtained by SPSS software.In the Technical Regulations for Grid Structures,the calculation formula for the bearing capacity of welded ball joints at normal temperature is obtained,and the calculation formula for the bearing capacity of welded welded ball joints under load is obtained.