Advanced seismic force resisting systems for cold-formed steel framed building structures

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Cold-formed steel (CFS) framed buildings are complex systems that under earthquake ground motion excitation experience the most severe demands of their life cycle. The current CFS lateral systems described in AISI S400 are intended for use in 1 to 3 storey buildings. Given the continually increasing population in urban centres, there exists a need to develop taller & larger buildings to better optimize land use in our cities; that is, CFS framed mid-rise buildings extending up to 8 storeys in height. The force and deformation demands placed on such buildings in a design level earthquake require the development of a lateral framing system that improves upon the capability of existing CFS systems. Preliminary studies at McGill have demonstrated the potential of a centre-sheathed framing system constructed of CFS members & panels to carry shear loads far in excess of what is possible using designs from AISI S400, with substantially improved ductility.   The objectives of the 5 year research program are: (i) Develop a CFS centre-sheathed shear wall system for use in mid-rise building construction, (ii) Expand on the CFS lateral seismic systems (R-values & height limits) listed in the NBCC, and (iii) Provide guidelines covering the design & construction of these systems for inclusion in the AISI design standards.   Methodology: Characterize through laboratory testing the response of framing / sheathing connections, frame action, response of chord members to combined loading, and the impact of non-structural components on shear resistance and stiffness. Complete a FE based parametric study of the shear walls and their chord stud configurations to broaden the database of characterization information. Establish an analytical design method for the centre-sheathed walls. Institute dynamic analyses of buildings using OpenSees models, capable of representing the high strength & ductility of the shear walls, the flexibility of the diaphragms, the added strength & stiffness of the non-structural components & bearing walls & the non-linear response of the chord studs, to verify the analytical design approach and to quantify the contribution of all wall components. Develop a design method for overturning / uplift and propose seismic R-values through dynamic analyses of building models for various locations and applicable suites of scaled ground motions. Use fragility curves to quantify the probability of failure. HQP: 1 PhD, 4 Master's, 5 Ugrad students & lab technicians.   This innovative research will advance the discipline of CFS framed mid-rise building seismic design. Codes & standards will be updated for the seismic design and analysis of CFS framed structures. The likelihood of collapse of CFS framed structures during a seismic event will be improved, as will the safety of building owners & occupants. Academic research programs beyond Canada will have access to these research findings that can be incorporated in comparable design guides worldwide.