Material Strength Uncertainty and Seismic Capacity Design for Steel Structures: Considerations and Standards

The article reviews the current state of design standards concerning the material grades available for common steelwork structures in seismic regions. A comparison between European and American frameworks is presented. Particular emphasis is placed on how the aspect of material overstrength is treated. In the frame of capacity design, it is important to guarantee the plastic hinges formation at the beams end, as well as to prevent their formation in non-dissipative members. For this scope, material properties uncertainties must be considered in the design process. Design standards do at the current state consider the aspect with opportune factors, ensuring the effectiveness of capacity design and a consistent and reliable design approach. Focus is placed on the existing design approaches, which find applicability in conjunction with the material standards and the design codes. The current state of the approaches is reviewed based on latest up-to-date research results. Furthermore, a study of how research analyses the effect of material uncertainties is performed. It is pointed out how high-strength steels can further improve the structural safety having less uncertainty on the material properties. These high-strength steels permit to have a wider elastic range but are generally associated with lower ductility. It is highlighted which grades are compatible with the requirements for dissipative zones according to the current standard. Complementary aspects such as the weldability, toughness, and through-thickness requirements are also mentioned.