Finite Element Analysis of Failure Modes of Directly Welded KT-type Overlapped SHS Joints

Finite element analysis on the failure modes of the overlapped KT-type square hollow section(SHS) joints was carried out by using ANSYS program.Influences of parameters including side lengh ratio of brace and chord,width-thickness ratio of chord,thickness ratio of brace and chord on the failure modes of joints were mainly analyzed.The analytical educed that the joints were found to fail in four modes.The 1st failure mode was local buckling failure of the upper chord surface behind the tensile brace.The 2nd mode was plastic failure of the upper chord surface.The 3rd mode was strength failure of the tensile brace.The 4th mode was chord bending failure.For joints without chord axis pressure,it is concluded that the joint is prone to fail in the 3rd mode when width-thickness ratio of chord,or thickness ratio of brace and chord is small and more joints with intermediate side lengh ratio of brace and chord fail in the 3rd mode than joints with big or small side lengh ratio of brace and chord.For joints with chord axis pressure,it is concluded that the main failure mode is changing from the 3rd mode to the 2nd mode then the 1st mode when width-thickness ratio of chord,thickness ratio of brace and chord increase and that the 1st failure mode happens more frequently when side lengh ratio of brace and chord increases and that a few joints with side lengh ratio of brace and chord equaled to 0.8 fail in the 4th mode.