Wall-diaphragm interactions in seismic response of building systems I: Parametric models and elastic response

Abstract

The objective of this paper is to study the elastic seismic response of simplified building models that include considerations of the vertical lateral force resisting system (walls) and the horizontal lateral force resisting system (floor diaphragms) through parametric study. The assumption of rigid diaphragms is often used in the seismic design of buildings; however, research suggests that the diaphragm may influence the fundamental building period and the seismic building response. In this paper, a simplified model is presented for single and multi-story buildings utilizing two degrees of freedom per story for the vertical system, for example, the walls, and one degree of freedom per story for the floor diaphragm. The number of stories, the stiffness of the walls and diaphragm(s), and the mass distribution between the walls and diaphragm are varied to represent a large range of potential building compositions. Eigen analyses of the models indicate that the wall and diaphragm interact when at similar periods resulting in elongation of the overall building period. Response of elastic time-history analyses of the building models are presented in this paper where it is shown that the force demands in both the wall and diaphragm(s) are dependent on the relative stiffness of the walls and diaphragm(s), and the mass-distribution between these two systems. In the companion paper “Wall-Diaphragm Interactions in Seismic Response of Building System II: Inelastic Response and Design” the parametric building study is extending to nonlinear time-history analyses including different levels of assumed inelasticity in both the walls and diaphragm.