New approaches to seismic design of steel framed buildings

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The majority of the international seismic design provisions, including the National Building Code of Canada (2005), employ the principles of capacity design to obtain structures capable of withstanding seismic solicitations. Although the main design objectives are usually achieved using this approach, the method presents several intrinsic inconsistencies. For instance, the procedures used to predict design values of displacements and deformations are not transparent and rely on somewhat artificial rules which fail to reflect the complex interactions that exist in actual structures. For certain structural systems, this can result in an important increase of structural mass without significantly improving the seismic behaviour.The research program described herein aims to develop new design procedures for the seismic design of steel structures based on performance objectives. The studies will focus on (i) the definition of performance criteria and (ii) the preliminary development of design procedures. Initially seismic behaviour of eccentrically braced frames will be examined in the framework of the global structural response through extensive numerical studies and innovative experimental program using shaking table. In particular, the relationship between the inelastic shear link rotation and the inelastic storey drifts will be examined to define the drifts associated with specific link performance. Subsequently, different approaches to performance-based design will be assessed to determine the appropriate methodology for this system and to propose design procedures suitable for practical use. The results will help better understand the global behavior of buildings under seismic loads and contribute to develop Canadian code provisions for seismic design of steel structures.