MECHANICAL BEHAVIOUR OF DISCONNECTED PILE RAFTS: EFFECT OF RAFT-SOIL-PILES RELATIVE STIFFNESS INCLUDING SOIL NON-LINEARITY

Since the late 1970s, the study of Piled Rafts (PR) has revolutionized the design of foundations for tall buildings. Scientific and regulatory evolution has driven a shift from capacity-based approaches — where the entire load is assigned to the piles — to performance-based approaches. In the latter, piles are optimized primarily as "settlement reducers" to minimize both absolute and differential settlements. This thesis focuses on Disconnected Piled Rafts (DPR). In this specific configuration, the direct structural connection between the raft and the piles is eliminated by interposing a "cushion" of appropriately compacted granular material. This solution significantly reduces the structural demand on the piles, leading to substantial cost savings. However, it introduces complex soil-structure interaction mechanisms that necessitate advanced analytical tools. The objective of this research is to evaluate the overall performance of DPRs using 3D Finite Element Method (FEM) numerical analyses, accounting for soil non-linearity and complex interface behavior. The results from detailed three-dimensional modeling will be compared with simplified numerical models based on elasticity theory and implemented in Matlab/Python environments at Aarhus University (Denmark). This comparison will help identify the limits of applicability of simplified models while providing practical design guidelines for optimized foundation systems.