Numerical analysis of the out-of-plane behavior of unreinforced masonry walls

Abstract

Out-of-plane stability of unreinforced masonry walls is an important aspect to be taken into account in edification. This construction technique is widely used and it is one of the most vulnerable to seismic loading. It has been observed that damage produced by out-of-plane loadings is one of the most commonly produced failure mechanisms in seismic hazards. Despite of that, research into the out-of-plane stability of masonry walls is not yet enough developed. The aim of this research is to create a three-dimensional finite element model in order to study the latter problem. A parametrical study is performed on two numerical models under monotonic and cyclic out-of-plane loads. The influence of various geometrical and boundary conditions are studied in two different models of a single wall: a homogenized and a distinct model.

A damage plasticity formulation, appropriate for brittle materials, is implemented for modeling the behavior of the wall. In the distinct model, frictional and cohesive interaction models are used for modeling the joints, which are constituted by mortar.

Firstly a monotonic homogeneous distributed out-of-plane pressure is applied, in order to determine both, the resistance of the wall in terms of its force-displacement curve, and the failure mechanism. Next, the same model is submitted to cyclic out-of-plane uniform pressure and energy dissipation, as well as stiffness degradation is analyzed.

Finally, some qualitative recommendations for the unreinforced masonry walls are derived from the results, with the purpose of maximizing the resistance in front of out-of-plane loading.