Seismic force modification factors for light-gauge steel-frame - wood structural panel shear walls

Design guidelines for laterally loaded light-gauge steel-frame - wood structural panel shear walls are not available in Canadian codes. A design method for the calculation of shear stiffness and strength has been developed for use with the 2005 National Building Code of Canada (NBCC), however. This method was based on the analysis, using an equivalent energy elastic-plastic (EEEP) approach, of over 180 single-storey shear wall tests of various configurations. Ductility-related (R-d) and overstrength-related (R-o) force modification factors also need to be defined to calculate equivalent static seismic forces following the 2005 NBCC. This paper describes the development of these two factors based on the EEEP analysis of the shear wall test results. To verify the "test-based" R-d and R-o values, nonlinear time-history dynamic analyses of two representative buildings were carried out using a suite of 10 earthquake records scaled to the 2% in 50 year uniform hazard spectrum (UHS) for Vancouver, British Columbia. Preliminary values have been determined for the force modification factors, namely R-d = 2.5 and R-o = 1.7.