Experimental investigation of CHS T/Y-joints fabricated from high-strength steel

In this study, an experimental program on welded hollow section joints fabricated from high-strength steel is presented. The experimental program tested a total of six T or Y cold-formed circular hollow section (CHS) joints under brace axial compression. One mild steel with a nominal yield stress of 355 MPa and two high-strength steels with nominal yield stresses of 460 and 650 MPa were included. The test results and existing test database were used to evaluate the relevant design provisions for high-strength steel joints. The material factor - used in the current standards to reduce the design resistance of high-strength steel tubular joints - was found to be adequate for CHS T/Y-joints with steel grades up to 700 MPa. The chord stress effect resulting from a particular test setup needs to be considered when evaluating the experimental joint strength. The experimental load-indentation relationships were analysed to appraise the behaviour of high-strength steel CHS T/Y-joints from the perspectives of ductility and serviceability. The ductility of high-strength steel T/Y-joints is slightly lower than that of mild steel joints. T/Y-joints show relatively lower ductility and serviceability performance compared to CHS X-joint counterparts that comprise identical members. Local strain distributions in tested T/Y-joints of different steel grades were analysed to identify the location and intensity of strain concentration. The possibility of fracture failure near the weld seam of the cold-formed chord member is discussed.