Cost-effective Steel Seismic Force Resisting Systems for Enhanced Response to Earthquakes

abstract : This presentation will introduce structural steel seismic force resisting systems that have been proposed to enhance the response of structures to earthquakes. The focus will be on braced frames used for building structures. The eccentrically braced frame system with replaceable ductile links will be introduced as an example where a minor modification can reduce fabrication costs, improve the seismic response and help post-earthquake recovery. Concentrically braced steel frames modified to exhibit self-centering response and eliminate structural damage by using either special brace members, rocking response or a combination thereof are then discussed. Controlled rocking response generally result in reduced seismic induced force demands on the structure and its foundations compared conventional designs. Such reductions can be significant and can be achieved at low cost for short-period, low-rise buildings responding essentially in their fundamental mode, which makes the concept attractive for the seismic retrofit of seismically deficient building structures. Single-storey steel buildings with large foot prints that are used for commercial and light industrial applications or sport facilities represent a large portion of the building stock in Canada. Seismic resistance for these structures is typically obtained using an horizontal roof diaphragm acting with vertical braced frames. Ductile brace fuses and rocking braced frames will be presented as options that can be implemented to enhance the response and reduce construction costs. Lastly, the presentation will discuss structural systems that are being investigated to achieve stable inelastic response for tall braced frames. These will include frames equipped with segmental elastic trusses and frames that are designed to exhibit post-yielding lateral stiffness.

Bio : Robert Tremblay is Professor of Structural Engineering at Polytechnique Montreal, Canada. He received his Bachelor (1978) and Master (1988) degrees from Université Laval and completed his Ph.D. in 1994 at the University of British Columbia in Vancouver. Before undertaking his doctoral studies, Prof. Tremblay worked for 10 years in the industry. He held a 14-year Canadian Research Chair in earthquake engineering between 2003 and 2017. His current research work is mainly directed towards the seismic design and response of steel structures. He is a member of the Standing Committee on Earthquake Design for the National Building Code of Canada, the CSA-S16 Technical Committee on Steel Structures for Buildings, the CSA S6 Technical Sub-Committee on Seismic Design of Bridge Structures, the AISC Task Committee 9 on seismic design of steel structures and the AISC Adhoc Task Group on Non-Building Structures and Industrial Buildings.