Towards improved seismic design procedures for steel structures
European seismic design procedures are currently undergoing a process of evolution and development. This process is guided by improved understanding of structural behaviour based on new research findings, coupled with the need to address issues identified from the practical application in real engineering projects. Developments in design guidance however need to balance technical advancements with the desire to maintain a level of stability and simplicity in codified rules. To this end, this paper summarises the main changes proposed in the imminent revision of Eurocode 8 with respect to the design of steel framed structures. Proposed code modifications in terms of seismic loading, behaviour factors, ductility considerations, capacity design verifications, as well as drift-related requirements, are outlined and discussed. In order to illustrate the implications of several of the main suggested code modifications on key performance aspects, a set of moment frames satisfying Eurocode 8 are utilised within a series of nonlinear static and dynamic analysis. It is shown that several of the proposed code changes lead to fundamentally improved seismic performance, whilst others result in more efficient design at the expense of safety margins at the design and ultimate levels. Importantly, the results emphasise the imbalance between the focus given to ductility supply compared to assessing the expected inelastic demand considering salient seismic loading characteristics such as frequency content and duration effects. The paper concludes with an appraisal of proposed code modifications and highlights areas in which further developments are still required to improve the reliability of seismic design procedures.
Professor Ahmed Elghazouli is Head of the Structural Engineering Section and Director of the MSc programme in Earthquake Engineering at Imperial College London. He has over 25 years of research and consulting experience in seismic design and structural robustness under extreme loads, and has published over 250 papers in related areas. He is a Fellow of the Royal Academy of Engineering, a Chartered Engineer and a Fellow of the Institutions of Civil and Structural Engineers. He has participated in key national and European code development activities. He is also a past chairman of SECED and currently chairs the BSI B/525/8 committee on seismic design.