Limit analysis of loaded out-of-plane rubble masonry: a case study in Portugal

Abstract

An integrated methodology for the characterization of the response of rubble masonry is presented. The behaviour at collapse of a wall belonging to the Guimarães castle (Portugal) is investigated through a rigid-plastic homogenization procedure, accounting both for the actual disposition of the blocks constituting the walls and texture irregularity, given by the variability of block dimensions. A detailed survey is conducted by means of a photogrammetric technique, allowing for a precise characterization of blocks dimensions and disposition. After a geometric simplification assuming mortar joints reduced to interfaces, homogenized masonry in- and out-of-plane strength domains are evaluated on a number of different representing elements of volume (RVEs) having different sizes and sampled on the walls of the castle. Strength domains are obtained using a finite element (FE) limit analysis with a heterogeneous discretization by triangles and interfaces. Finally, a series of limit analyses are carried out on the façade for the safety assessment under seismic loads by means of two numerical models, the first one being a heterogeneous model and the second a homogenized approach. The reliability of the results, in terms of limit load and failure mechanism, provided by the homogenized model, when compared to the heterogeneous one is satisfactory.