PILE FOUNDATION IN 3D MODELLING OF BUILDING DAMAGE DUE TO SETTLEMENT

This paper focuses on different modelling approaches to soil-structure interaction in the 3D finite element analysis of settlement-induced damage on buildings. Settlement-induced damage on historical structures can be a relevant consequence of excavations in urban areas. Numerical analyses adopted to predict the potential damage need to take into account the influence of the soil-structure interaction, which includes the foundation response. In case of pile foundation, the most detailed method consists of using solid elements for the piles and plane interfaces to represent the soil-pile interaction. Because of the need to match the pile and interface element faces with the soil element faces, this approach implies a complex mesh generation process; furthermore, a great computational expense is required, due to the large number of elements. In this paper, two simplified modelling approaches are compared. The first is based on the use of 3D embedded beam elements with interface slip; this allows simplification of the mesh, without neglecting important aspects of the soil-pile behaviour. Every single pile is still modelled explicitly. In the second approach, the piles are "smeared" to horizontal interface elements with equivalent nonlinear behaviour to represent the soil-structure interaction. Both of the methods are applied to the analysis of a masonry structure subject to tunnelling in soft soil. A crack model is adopted for the building, and the tunnelling advanced is simulated through a stage analysis. Results are compared in terms of structural damage and the feasibility of the two modelling strategies is evaluated. It is shown that the selected modelling approach affects the way the soil settlements are transferred to the structure and significantly influences the predicted damage.