Material Ductility of Very High Strength (VHS) Circular Steel Tubes In Tension

This paper investigates the material ductility of very high strength (VHS) circular steel tubes under tension in terms of the ultimate strength to the yield stress ratio, the percentage elongation, the fracture to ultimate load ratio and the ultimate to yield strain ratio. 15 tensile coupon tests and 12 full section tests on VHS tubes were carried out. The tested VHS tubes have a diameter ranging from 31.8 mm to 75 mm with wall thickness ranging from 1.6 mm to 2.0 mm. The non-heat-treated tubes, which were used to make VHS tubes, were also tested for comparison purposes. Different failure modes were observed for VHS tubes and non-heat-treated tubes. The ultimate strength to yield stress ratio of VHS tubes was compared with that of various cold-formed hollow sections, sheet steels and quenched and tempered steels. The test results were compared with ductility requirements in various codes. It has shown that the VHS tubes satisfied the material ductility requirement specified in the Australian/New Zealand Standard for Cold-Formed Steel Structures AS/NZS4600. © 2001 Elsevier Science Ltd. All rights reserved.