Shear Yield and Shear Rupture Strength of Welded Brace Members under Cyclic Loading

The shear yield (SY) and shear rupture (SR) are two critical failure modes in steel bracing members with welded gusset plate connections. These failures occur near the longitudinal welds in the member and ultimately cause separation of the brace member from the gusset plate. The SY appears as excessive displacement in the member connection region which ultimately leads to SR failure and separation. Existing research on these phenomena in welded braces is limited, particularly under compressive and cyclic loading conditions. Current studies focus mainly on monotonic tensile loading. This is despite the fact that braces are commonly subjected to reversible loads such as those from wind and seismic events. Compressive loads induce local buckling, and cyclic loading causes low-cycle fatigue, both of which significantly influence failure patterns. This study investigates the SY and SR behaviours of welded single and double-channel members under tensile, compressive, and cyclic loads. Nonlinear finite element (FE) models with ductile fracture prediction capabilities were developed and validated against experimental results. Eight specimens with varying channel sizes, gusset dimensions, weld lengths and throat thicknesses were analysed. The load-displacement results were plotted and compared, and the applicability of AISC design strength equations were evaluated. Results showed that AISC equations provide conservative estimates for monotonic loading. However, under cyclic loading, the equations slightly overestimate the shear rupture strength in some cases but remain generally safe if excessive deformation is acceptable. This research provides a detailed numerical investigations of SY and SR under compressive and cyclic loads. It highlights the effects of low-cycle fatigue and local buckling on shear capacity and failure patterns. These findings address gaps in design standards and improve the safety and reliability of welded brace connections in structures exposed to reversible loading conditions.