Study On Strength Of CHS Joints Reinforced By External Stiffeners

As a common joint type in steel tubular structures,welded tubular joints are intensively studied since steel tubular structures are widely used in engineering projects.Usually the joint strength is lower than the tubular members,so researcher in the world have proposed many joint strentghening methods.This thesis compares the advantages and disadvantages of different joint strengthening methods by reviewing related literatures,and then carrys out research on the reinforcement of joints with external stiffeners.The research on the reinforcement of joints with external stiffeners is implemented through theoretical analysis and model test investgation.Three sets of tests were designed to compare the ultimate bearing capacity of T-joints and K-joints with external stiffeners,respectively.The ultimate bearing capacities of the six sets of joints were analyzed by the general finite element analysis software ABAQUS.The results of the tests and the finite element simulations were in good agreement,which indicated that the finite element simulation method were suitable for solving this kind of problem about tubular joints.In order to fully analyze the effect of joint size parameters and stiffener size parameters on the ultimate bearing capacity of joints,this thesis has performed comprehensive parametric studies based on the accurate and reliable research methods,and obtained quantitative conclusions.According to the existing research results,this thesis uses orthogonal design method to analyze the effect of the ratio of brace to chord diameter β,the ratio of chord diameter to twice of chord thickness γ,the stiffener height factor and the thickness factor on the enhancement coefficient of the joint ultimate bearing capacity.All parameters are orthogonal each other,and there are 240 strengthened T-joint models and 81 strengthened K-joint models.In order to realize rapid modeling,this thesis uses Python language script to complete modeling and pre-processing work through the second development interface provided by ABAQUS,saving considerable time and manpower.The parameter analysis results show that:For T-joints,the enhancement coefficient of the joint ultimate bearing capacity decreases with the increase of the ratio of brace to chord diameter β,but is rarely affected by the ratio of chord diameter to twice of chord thickness γ and the stiffener thickness factor.The stiffener height factor has the most significant influence on the enhancement coefficient of the joint ultimate bearing capacity,and the relationship between the two is almost linear.For K-joints,in order to obtain a better strengthening effect,a reasonable range of β value is 0.3~0.5.The effects of the ratio of brace to chord diameter β,the ratio of chord diameter to twice of chord thickness γ,the stiffener height factor and the thickness factor on the enhancement coefficient of the joint ultimate bearing capacity are analyzed.The stiffener thickness factor barely influences the enhancement coefficient of the joint ultimate bearing capacity,and the effect of γ on the ultimate bearing capacity of joints is not clear.Finally,a formula is proposed to calculate the enhancement coefficient of the joint ultimate bearing capacity by using the regression method.Base on the research results of this thesis,the further research on this issue is prospected.