Use of HSS and VHSS in steel structures in civil and offshore engineering - Requirements regarding material properties

In Memoriam of Prof. Dr. Bernt Johansson
The use of high-strength steels (HSS, 460 < fy ≤ 700 MPa) and particularly very high-strength steels (VHSS, fy > 700 MPa) is limited in steel structures in civil and offshore engineering. This is due to a lack of experience in structures made of these materials and a lack of understanding of the structural performance of HSS and VHSS. The main questions that are unanswered concern the topics of static strength, fracture toughness, fatigue, material (in)homogeneity and manufacturing. With regard to the static strength, it is unclear as to whether requirements currently stated in the Eurocodes for the yield-to-tensile strength ratio (fy/fu) as well as the Von Mises yield criterion are applicable to structural designs in HSS and VHSS. With regard to fracture toughness, it is unclear as to whether the crack arrest capability of HSS and VHSS is currently sufficiently covered in Eurocode requirements. Furthermore, Eurocode requirements for maximum plate thickness are quite restrictive if they are extrapolated to HSS and VHSS. Other questions relate to the homogeneity of the material. Are HSS and VHSS sufficiently resistant to lamellar tearing and is material testing in different orientations necessary? This study gives an overview of the relevant questions, outlines the requirements in the current Eurocode system, presents answers to these questions where possible and provides a recommended research focus for the coming years.