Research On The Ultimate Strength Of The Tube-gusset K-joints

Nonlinear finite-element analysis of the ultimate strength of the tube-gusset K-joints and the regression formula about the ultimate strength of the tube-gusset K-joints are researched in this thesis.The tube-gusset K-joints are widely used in connection of chords and braces, joints of the frame, steel bridge joints, transmit electricity tower joints, support connections and other steel structures . Nonlinear finite-element analysis of the ultimate strength of the tube-gusset K-joints by ANSYS program are carried out in this thesis. The influence of nondimensional geometric parametersα,β,ν,Ï„₂,Ï„₂ ,γon the failure modes and the ultimate strength of the tube-gusset K-joints are studied. Four typical failure modes are discovered through the research on the ultimate strength of the tube-gusset K-joints. The four typical failure modes are brace local buckling ,plate yielding ,the combination of plate yielding and brace failure andthe combination of plate yielding and chord excessive plastic deformation failure . The geometric parameters is the main factor to the ultimate strength of the tube-gusset K-joints .The influence of nondimensional geometric parametersα,β,ν,Ï„₁,Ï„₂ ,γon the ultimate strength of the tube-gusset K-joints are studied and the rational values of nondimensional parameters are presented .The effects on the ultimate strength of the tube-gusset K-joint of the net distance between braces and chords, eccentricity of the joints ,the axis force of chords , the angle of chord and brace , the different support restriction are also considered .The failure of the joints in the finite-element results are mostly caused by the invalidation of connection plate. The connection plate is the weakness of the tube-gusset K-joints. Some plates are added to stiffen the joints in order to improve the ultimate strength of the tube-gusset K-joints .The effects on the ultimate strength of stiffened plate in different places are studied .The comparison of the ultimate strength between the tube-gusset K-joints and the stiffened tubular K-joints is also studied .The ultimate strength of the stiffened tubular K-joints is 30%higher than the tube-gusset K-joints when welding-defects and residual stress of the joints are not considered . But the constructions of the stiffened tubular K-joints are more complex than the tube-gusset K-joints. The ultimate strength ,the constructions and welding-defects and residual stress and other fators should be all considered in selecting joints. The regression formula of the ultimate strength of tube-gusset K-joints by the method of least squares are showed based on the results of the finite-element analysis.