Backbone Model for Confined Masonry Walls for Performance-Based Seismic Design

In this study, a performance-based model is proposed, capable of simulating seismic behavior of typical confined masonry (CM) walls whose response is governed by shear deformations. This model is developed on the basis of both monotonic and reversed-cyclic experiments assembled in an extensive database, and derived through an iterative linear regression analysis. Owing to the limited data available and inconsistencies in observed behavior in some tests, only specimens with two tie columns, one on either edge of the wall; multiple longitudinal rebar per confining element; no bed joint reinforcement; no openings within the confined panel; and a height-to-length ratio that varies from 0.7 to 1.2, are considered for the purpose of model development. The effect of openings on strength characteristics, the capability of existing models to predict seismic behavior of CM walls, and the limitations of the proposed equations are discussed in detail. The accuracy of the model is also verified for CM walls with different characteristics. The proposed model simulates reasonably well the seismic behavior of CM walls whose properties conform to the assumptions of the model and that correspond to typical CM walls.