Investigation of shear lag failure in gusset-plate welded structural steel hollow section connections

Shear lag (SL) failure is a premature tensile failure that may occur in gusset-plate welded connections in structural steel hollow sections (SSHS). There have been a number of studies of SL failure in gusset-plate welded SSHS connections, but these are all limited to SSHS with a yield stress less than 500 MPa. This paper presents an investigation of SL failure for gusset-plate welded connections in very high strength (VHS) tubes with a yield stress of 1350 MPa, and SL design for gusset-plate welded connections in both VHS tubes and regular SSHS. Tensile tests on 16 specimens of gusset-plate welded connections in VHS tubes with various weld lengths were conducted. The experimental maximum connection strengths from the tensile tests were compared with predictions based on the existing SL design rules in the US, Canada and Australia. It was found that these design rules are not adequate. Therefore, modifications to these design rules were postulated and examined. Design rules are proposed for gusset-plate welded connections in all SSHS including VHS tubes. A capacity (resistance) factor of 0.70 is also proposed based on a reliability analysis using the first order second moment (FOSM) method.