1 Abstract The paper presents a novel micro-mechanical model for the homogenized limit analysis of out-of-plane loaded masonry walls. In the framework of homogenization combined with limit analysis, masonry thickness is subdivided in several layers and for each layer polynomial distributions for the stress fields are a-priori assumed inside a fixed number of sub-domains. In this way, a simple linear optimisation problem is derived in order to obtain out-of-plane homogenized failure surfaces of masonry. Then, the surfaces so recovered are implemented in FE limit analysis codes for upper and lower bound analyses on entire masonry panels out-of-plane loaded. Some of these numerical investigations are reported in the paper in order to show the reliability of the results obtained (in terms both of collapse loads and failure mechanisms) in comparison with experimental evidences. Keywords: masonry, homogenization, limit analysis, out-of-plane loads, lower bound, upper bound. 1 Introduction The prediction of the ultimate load bearing capacity of masonry walls out-of- plane loaded is technically very interesting. In fact, out-of-plane failures are mostly related to seismic and wind loads and earthquake surveys have demonstrated that the lack of out-of-plane strength is a primary cause of failure in the most traditional forms of masonry. This fact is confirmed in the case of historical buildings, where the façades are often characterized by a relative small thickness (see for instance [1]). Furthermore, many damages suffered by old masonry buildings during earthquakes might be ascribed to out-of-plane collapses. Another important aspect to underline is that masonry structures are usually subjected simultaneously to in-plane compressive vertical loads and out-of-plane actions. As shown by experimentations, Paper 185 A Micro-Mechanical Model for the Homogenized Limit Analysis of Out-Of-Plane Loaded Masonry Walls G. Milani†, P.B. Lourenço‡ and A. Tralli† † Department of Engineering University of Ferrara, Ferrara, Italy ‡ Department of Civil Engineering University of Minho, Guimarães, Portugal Civil-Comp Press, 2005. Proceedings of the Tenth International Conference on Civil, Structural and Environmental Engineering Computing, B.H.V. Topping (Editor), Civil-Comp Press, Stirling, Scotland.