TESTS AND DESIGN OF LONGITUDINAL FILLET WELDS IN VERY HIGH STRENGTH (VHS) STEEL CIRCULAR TUBES

摘要

Very high strength (VHS) tubes offer superior strength and enormous reduction in weight. Test carried out at Monash University showed that the average yield stress of the VHS tubes is around 1,350 MPa with an ultimate tensile strength of 1,500 MPa. There is no information on the behaviour of longitudinal fillet welded connections in VHS tubes. Existing research on this topic was limited to square and rectangular hollow sections (SHS and RHS) with a yield stress up to 450 MPa. Existing design rules may not be appropriate for VHS circular tubes. This paper describes a series of tests on longitudinal fillet welds in VHS steel circular tubes. The thickness of VHS tubes varies from 1.6mm to 2.0mm. The weld length (L_w) of longitudinal fillet welds varies from 15mm to 65mm. Two failure modes were observed, namely failure along the weld and tube failure. The test results were compared with the formulae developed for C450 SHS. The effect of strength reduction in the heat-affected-zone (HAZ) on design was included in the proposed design formulae. Critical weld length formula was derived, which can be used to predict the failure mode.