Study On Mechanical Properties And Design Method Of Unconventional Welded Hollow Spherical Joints

The spatial structure has the advantages of reasonable stress,unique shape,convenient construction and good economy.In recent decades,it has been widely concerned,studied and built.More and more spatial structures appear in various buildings such as stadiums,museums,convention and exhibition centers,terminals and so on.As an important part of space structure,welded hollow spherical joints are the key to affect the stress of the structure.However,at present,the research on the mechanical properties and design methods of welded hollow spherical joints mainly focuses on the conventional circular steel pipe welded hollow spherical joints.In order to adapt to the continuous development and innovative structural forms of spatial structures,some related studies on special forms of welded hollow spherical joints are rarely involved.Therefore,in this paper,the mechanical properties of three special types of welded hollow spherical joints,including H-section steel welded hollow spherical joints,drum welded hollow spherical joints and cross ribbed plate welded hollow spherical joints,are systematically studied,and the joint forming process is preliminarily explored.The main research contents and results are as follows:(1)Study on mechanical properties of H-section steel welded hollow spherical joints.The mechanical properties of 24 H-beam welded hollow spherical joints under axial compression,axial tension and eccentric compression were studied.The effects of joint size,material,stiffener and loading mode on the mechanical properties were investigated.The failure mode,load-displacement curve,ultimate bearing capacity and strain distribution of the joint under different forces are obtained and analyzed.The finite element model of the joint is established and the parametric analysis is carried out,and the relationship between the joint size and bearing capacity is obtained.The calculation formulas of tensile and compressive bearing capacity of H-section steel welded hollow spherical joints and the simplified design formula under eccentric compression are proposed and verified.(2)Study on mechanical properties of drum welded hollow spherical joints.The full-scale axial compression and axial tension properties of six drum welded hollow spherical joints are studied.The main mechanical properties of the joints under different forces,such as failure mode,load-displacement curve,ultimate bearing capacity and strain distribution,are obtained and analyzed.The finite element model of the joint is established and the parametric analysis is carried out,and the relationship between the joint size and bearing capacity is obtained.The calculation formulas of tensile and compressive bearing capacity of drum welded hollow spherical joints are proposed and verified.(3)Study on mechanical properties of welded hollow spherical joints with cross ribbed plates.The axial compression,axial tension and bias tests were carried out on19 cross ribbed plate welded hollow spherical joints,and the axial tension tests were carried out on 6 single plate welded hollow spherical joints.The effects of joint size,material,stiffener,eccentricity and loading mode on mechanical properties were investigated.The failure mode,load-displacement curve,ultimate bearing capacity and strain distribution of the joint under different forces are obtained and analyzed.The finite element models of cross ribbed plate welded hollow spherical joint,circular steel pipe + cross ribbed plate combined welded hollow spherical joint and single plate welded hollow spherical joint are established,the parametric analysis is carried out,and the relationship between joint size and bearing capacity is obtained.The calculation formulas of compression bearing capacity of cross ribbed welded hollow spherical joints and welded hollow spherical joints connected by circular steel pipe + cross ribbed plates are proposed and verified,the calculation formulas of axial tensile bearing capacity of three kinds of cross ribbed welded hollow spherical joints and the calculation formulas of bias bearing capacity of cross ribbed welded hollow spherical joints are proposed and verified.(4)Numerical simulation and mechanical properties analysis of the whole machining process of welded hollow spherical joints.Taking the drum welded hollow spherical joint as an example,the numerical simulation method of the joint in the process of stamping and welding is established,and the parametric analysis is carried out.The effects of joint size and stamping speed on wall thickness thinning rate and the effects of joint size,welding heat source and stiffener on welding residual stress are analyzed.Furthermore,the effects of wall thickness thinning rate and welding residual stress on the ultimate bearing capacity and initial stiffness of the joint are obtained.