Definition of interaction curves for the in-plane and out-of-plane capacity in brick masonry walls

• Numerical investigations indicate strong in-plane/out-of-plane capacity interaction.
• Wall aspect ratio and the material properties in tension have the most influence on the level of the interaction.
• An analytical method for in-plane/out-of-plane capacity interaction in brick walls is proposed.
• The analytical method provides results that are accurate and on the safe side.

During an earthquake a wall is subjected to a three dimensional acceleration field and undergoes simultaneous in-plane and out-of-plane loading. The action of one type of loading on the wall affects the strength of the wall against another type of loading. In this paper, a numerical investigation, supported by experiments, is conducted aimed at deriving appropriate relations for the in-plane/out-of-plane capacity interaction in unreinforced brick walls. Through a comprehensive parametric study, the main affecting parameters are recognised and their influences on the capacity interaction are established. The parametric study indicates that the aspect ratio of the wall and the elastic and inelastic material properties in tension have the most influence on the level of the in-plane and out-of-plane capacity interaction in masonry walls. Based on the results of these investigations, representing empirical relations for evaluating the interaction are derived and their accuracy is verified.