Keywords: masonry, finite element method, computer-aided detection, soil defect impact, control-profile, distributed network, soil-structure interaction.

The literature clearly acknowledges that masonry structures exhibit poor tensile strength capacities. In this framework, such structures often reveal a serious susceptability to defects occurring underground. In day-to-day engineering practice, it sometimes remains difficult to estimate to what extent a given soil defect is likely to influence the stress state inside a masonry system and, once it is the case, to objectively quantify the impact of this defect on the structure.

The present paper is organized in four parts. The first part sets up the context in which most of the problems will occur, insisting on the relationship between the intrinsic weaknesses of the masonry material (widely used worldwide), the usual symptoms associated with soil defects (soil settlements, soil sliding, etc.) and the pathologies that will affect a masonry building. The current challenges in the field of risk management are then presented in order to justify the interest in an automatic calculation tool likely to detect and objectively quantify the impact of a given soil defect on a given building.

The second part concerns the method proposed by the authors in order to achieve the presented aim: the recourse to a network of control-profiles that will be used as a grid of analyses super-imposed on the stress fields obtained using a classical finite element calculation. For each control-profile, an equivalent force pattern will be calculated (a Maunder [1] like method) which may be used for determining a conventional fictitious reinforcement contribution. By integrating the entirety of fictitious reinforcement contributions inside the same matrix, it is then possible to establish an impact code associated with a given soil defect with a building configuration. Such impact codes (distributed network analysis codes) constitute a digested rendering of a situation that may be used for performing comparisons between situations. From a comparison between a state with and without soil defect, it is possible to mathematically detect whether an impact of the soil defect may be noticed. Once the case occurs, a spatial integration of each fictitious reinforcement contribution may then lead to the computation of a global indicator associated with the studied configuration (building plus the given soil defect).

The third part of the paper proposes a preliminary implementation of the different concepts of an automatic tool developed inside the Matlab environment. This tool may be coupled with any classical FE program.

The fourth part presents a case study: an ancient un-reinforced masonry building located in a karstic region of Belgium illustrating the extent that the tool coupled with Abaqus provides very encouraging results that may now be used as the base-data for an optimization process in an inverse analysis.

1

E.A.W. Maunder, "Thrust line solutions for masonry arches derived from finite element models", in C. Melbourne, "Arch Bridges", Thomas Telford, London, 215-224, 1995.

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