Ultimate strength of welded thin-walled SHS-CHS T-joints under in-plane bending

Welded thin-walled T-joints made up of square hollow section (SHS) chords and circular hollow (CHS) section braces are tested under static in-plane bending load. The hollow sections are cold-formed and have thicknesses less than 4 mm. The SHS-CHS T-joints are used in building the undercarriages and structural supports of equipment and structural systems used in the road transport and agricultural industries. Failure in the SHS-CHS T-joints was observed to occur as a result of chord-face yielding. Chord cracking was also observed after large deformations, resulting in a peak load being attained in these joints. In this paper, load versus chord flange indentation graphs, for the SHS-CHS T-joints are used to determine the deformation limit that can be used in defining the ultimate strength of the joints. The deformed shape of the chord observed from experimental tests is used to create a yield line model. A formula is derived, for the ultimate strength of the SHS chord and CHS brace vierendeel connections based on a plastic mechanism analysis using yield line theory. The ultimate strength determined through the use of the deformation limit criteria is compared to the ultimate strength calculated using the formula obtained from yield line theory.