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UBC Theses and Dissertations

Performance based evaluation of prequalified steel seismic force resisting structures in Canada Murphy, Michael

Abstract

Structural Steel is one of the most important building materials used worldwide; special Seismic Force Resisting Systems (SFRS) have been developed to use steel to resist seismic forces in earthquake prone regions. In Canada, several steel SFRS have been adopted in the code, these include Moment Resisting Frames, Concentrically and Eccentrically Braced Frames, Buckling Restrained Braced Frames and Steel Plate Shear Walls; conventional construction frames may also be designed which have no seismic detailing. The design of these systems is covered comprehensively in literature; however no guidance has been provided regarding the selection of the best system for a project. In this thesis, the relative merits of each of the prequalified systems have been studied. A five story office building located in Vancouver, British Columbia, was redesigned nine times implementing each of the clauses for seismic design in CSA S16-09. The relative performance of each are compared using the Performance Based Earthquake Engineering (PBEE) method. PBEE accounts for the uncertainties in the seismic hazard, structural response and structural damage and their effect on the building performance during an earthquake. The relative merits of these systems were evaluated in terms of material usage and financial loss of the structure after a seismic event. The conclusion is that although the Moment Resisting Frame carries the lowest repair costs, it uses 20% more steel than the Eccentrically Braced Frame. The optimum systems in terms of material usage and repair costs were the Steel Plate Shear Wall (type ductile) and the Eccentric Braced Frame. The worst performing were the buildings designed with low ductility; both the conventional construction and limited ductility Concentrically Braced Frame structures performed poorly. Analysis shows that under the conditions of this thesis, most of the repair costs are related to the acceleration sensitive nonstructural components. Systems designed with higher ductility experienced lower accelerations and therefore lower costs. The PBEE methodology is an effective approach for evaluating different structures and comparing how they perform dynamically in an earthquake. Using PBEE, this thesis shows the advantages of frames designed in Canada for high ductility in economic terms.

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