Weld effective lengths of rectangular hollow section T-connections under branch bendingHenry Granjon Prize 2014 winner Category C: Design and Structural Integrity

The 2010 AISC Specification for Structural Steel Buildings has expanded the scope in chapter K: design of HSS and box member connections to include a section K4: welds of plates and branches to rectangular HSS. An experimental programme was undertaken at the University of Toronto to test various unreinforced RHS-to-RHS 90° T-connections subject to branch in-plane bending moment with the objective of determining the effectiveness of the welded joint. Twelve unique test specimens were designed to be weld-critical, and the results from the full-scale tests revealed that the current equation for the effective elastic section modulus for in-plane bending, Sip, given in Table K4.1 of AISC 360-10 is very conservative. A modification to the current requirements that limits the effective width of the transverse weld elements is proposed, resulting in a safe and more economical weld design method for RHS-to-RHS T-, Y- and X- connections subject to branch axial load or bending moment. It is also concluded that the fillet weld directional strength enhancement factor, (1.00 + 0.50sin1.5θ), should not be universally applied to all connections between square and rectangular hollow structural sections in combination with effective weld properties as it may result in an unsafe design.