Performance-based interaction domains for eccentrically loaded pile groups considering scour effects

This study presents a performance-based framework for constructing interaction domains for eccentrically loaded pile groups. The proposed approach enables the derivation of interaction domains in the Q–Mx (or Q–My) plane by employing input parameters directly related to the mechanical properties of the soil (stiffness and strength) and the geometric configuration of the pile group. Unlike most existing formulations, which primarily focus on the Ultimate Limit State (ULS), the present method is performance-based, thus both Serviceability Limit State (SLS) and ULS conditions (defined in terms of settlement and/or rotation) can be investigated. The approach provides a rational and displacement-driven assessment of the foundation’s performance. The formulation relies on a Boundary Element Method (BEM) model to capture pile-soil and pile–pile interactions, assuming a perfectly rigid connecting structure. A key feature of the proposed method is its ability to incorporate the effects of scour around the foundation. This capability is particularly relevant from a design perspective, as it allows engineers to account for site-specific modifications, such as those occurring in the case of bridge pier foundations in fluvial environments, that may significantly influence foundation behavior. The method can also accommodate pile groups with heterogeneous characteristics, such as non-uniform spacing, lengths, diameters and mechanical properties. The resulting performance-based interaction domains offer an efficient and reliable tool for the preliminary design and assessment of pile groups subjected to eccentric vertical loads, providing guidance for both new and retrofitted foundations.