A displacement-based strength reduction factor for high-rise steel moment-resisting frames

Abstract

A preliminary study of the ‘displacement-based strength reduction factor’ for high-rise steel moment-resisting frames is presented in this paper. The base shear capacity required for a high-rise steel building in a displacement-based design can be estimated from the reduction of the displacement-based elastic response. The conventional force-based design procedure is still adopted as the initial stage of the displacement-based design. To establish an empirical formula of the proposed displacement-based strength reduction factor, non-linear time-history analyses of six moment-resisting frames are investigated. The conventional ‘equal displacement rule’ and ‘equal energy rule’ are no longer held when the displacement limitations are considered. As a result, a modification for conventional strength reduction factors is proposed for further applications in displacement-based design. An adjustment factor defined as ‘deformation energy ratio’, β, which is related to natural periods, is introduced. The final displacement-based strength reduction factor is defined as a function of ductility demand, fundamental period and the deformation energy ratio. Copyright © 2006 John Wiley & Sons, Ltd.