Definition of Seismic Input for Out-of-Plane Response of Masonry Walls: II. Formulation

Abstract

The seismic input expected on an out-of-plane wall (or a generic secondary element) in a URM building is the ground excitation filtered by the in-plane response of the walls and the response of the floor diaphragms. More generally, the dynamic response of the primary structure, which can be nonlinear, contributes to the filtering phenomenon. Inelastic response of the primary structure can alter the secondary system response considerably in comparison to that under elastic structural response. The current article proposes a semi-analytical formulation to estimate the acceleration demand on an out-of-plane URM wall that explicitly takes into account the level of inelasticity in the primary structure in terms of the displacement ductility demand. A simplified approach to determine the acceleration profile over the height of a structure is also introduced. The formulation is based on statistical evaluation of the results of several inelastic time-history analyses treated within a parametric framework, which are presented in the companion article.