A Simplified Performance-Based Method for Deriving Interaction Domains of Eccentrically Loaded Pile Groups

This contribution presents a simplified approach for deriving performance-based interaction domains for eccentrically loaded pile groups. The construction of interaction domains in the Q–Mx (or Q–My) space typically requires, as input parameters, the basic mechanical properties of the soil (stiffness and strength) as well as the geometry of the pile group. Most previous research has focused on the development of interaction domains corresponding to Ultimate Limit State (ULS) conditions, while only a few recent publications have addressed interaction domains related to the Serviceability Limit State (SLS). The approach developed in this work is capable of considering both Serviceability Limit State (SLS) and Ultimate Limit State (ULS) conditions, thereby enabling a comprehensive performance-based analysis of the foundation system. In this framework, pile group effects are modeled through interaction coefficients derived from a boundary element method solution. The contribution of the pile cap is neglected, and the connecting structure is modeled as infinitely rigid, with piles connected via spherical hinges. Furthermore, the proposed approach allows for the modeling of pile groups with heterogeneous geometric characteristics, such as variable spacing, differing lengths, and non-uniform diameters. This flexibility enables the simulation of a wide range of foundation configurations, including those resulting from retrofitting interventions. Finally, the approach can be extended to the analysis of complex conditions, such as riverbed piers affected by localized scour phenomena and generalized riverbed lowering, by incorporating different scour geometries into the model.