A kinematic limit analysis approach for masonry buildings: in- and out-of-plane failure mechanisms

Historical and existing masonry structures have usually an inadequate resistance to horizontal actions. Furthermore, historical city centres present high vulnerability under horizontal loads and this is mostly due to the absence of adequate connections between the various parts [1] [2]. This characteristic leads to overturning collapses of the perimeter walls under seismic loads and combined in- and out-of-plane failures. Even if limit analysis is not sufficient for a full structural analysis under seismic actions, since it does not provide displacements at failure, it can be used in order to have a quick estimation of both collapse loads and failure mechanisms [3]. In this paper, the micro-mechanical model presented by the authors in [4] and [5] for the limit analysis of respectively in- and out-of-plane loaded masonry walls [6] is utilized for the 3D analysis of entire buildings. In the model, admissible and equilibrated polynomial stress fields are imposed in order to estimate the macroscopic masonry failure surface. Finally, such surface is implemented in a FE kinematic limit analysis code and an example of technical relevance is discussed in detail.