Wall‐diaphragm interactions in seismic response of building systems ii: Inelastic response and design

Abstract

AbstractAn elastic parametric study of simplified single‐ and multi‐story building models presented in a companion paper shows that seismic building response depends on the period(s) of the vertical lateral force resisting system (vLFRS), the period of the diaphragm (i.e. the horizontal LFRS, or hLFRS) and the mass distribution between the walls and floors. This paper extends the study to include the potential for inelasticity (ductility) in both the v‐ and hLFRS and examines the impact of this inelasticity on the building response. Increased ductility in the vLFRS reduces vLFRS forces, but to what extent are hLFRS (diaphragm) demands reduced? Similarly, ductile hLFRS presumably reduce hLFRS forces, but what about vLFRS forces? Past work has shown that hLFRS forces are difficult to predict. The building model responses indicate wall‐diaphragm interactions may occur between higher modes of the vertical system and the rigid diaphragms causing increased force demands. Ductility demands are observed to be driven by the element (wall or diaphragm) with the larger inelasticity. Significant ductility demands are observed for short period buildings. A simplified formula for an effective ductility seismic force response modification coefficient for the horizontal LFRS is proposed that considers force reductions from both the inelastic vertical and horizontal LFRS.