A study of current research achievements and challenges on the application of High Strength Steel (HSS) endplates in seismic resisting systems

Abstract

High strength steel is increasing in demand due to economic and mechanical benefits. A typical mechanical characteristic of HSS is that the ductility of the material decreases along with the increase in strength. This has been one of the main concerns of HSS in construction applications. The Y/T ratio and elongation requirement in Eurocode 3(1-8) and in NZS 3404 significantly constrains the application of HSS in seismic resisting systems, especially when dependable ductility from plastic action is required from the HSS component. Furthermore, the amount of strength loss resulted from high heat input during welding process is therefore a significant factor that may affect the performance of the connections. The implications of this are not straightforward to determine. This means that the mechanical performance of HSS beam-to-column connection has not been systematically studied, especially for bolted endplate connections which are widely used across New Zealand. In these connections, the HSS steel could be used to significantly reduce the thickness of the currently used thick endplates leading to appreciable reduction in weight and cost of these connections. To achieve that, it is necessary to study the impact of HSS on the structural behaviour of moment resisting endplate connections comprehensively and to determine what the performance limits are so that, ultimately, the limits in the standards can be relaxed. This paper discusses the current achievements and challenges of HSS connections in seismic resisting systems, and the key areas that need to be researched to better understand HSS connections behaviour under seismic loading.