Hardness and compressive capacity of longitudinally welded very high strength steel tubes

This paper presents a study on the hardness and compressive capacity of longitudinally welded very high strength (VHS) steel tubes. VHS tubes, with a nominal yield stress of 1350 MPa and an ultimate tensile strength of 1500 MPa, were welded longitudinally to Grade 300 steel plates using the GTAW welding method. The hardness in the heat affected zone (HAZ) dropped to around 40% of that of the VHS steel without welding. The lowest hardness occurred at a location of about 4 mm from the weld toe. The strength in HAZ of longitudinally welded VHS tubes is about 55% of that of VHS tubes. The newly derived HAZ strength reduction factor is applied to predict the load carrying capacity of VHS tubes longitudinally welded to plates, fabricated sections with VHS tubes as corners and concrete-filled fabricated sections.