Simple approaches for piled foundations under combined axial-moment loading

The problem of piled foundations under combined axial-moment loading involving tension load on piles is investigated both theoretically and experimentally. A physically motivated mathematical framework based on the interaction factor method is first presented and discussed. Piles are modelled as interacting uniaxial elements characterized by a hyperbolic-truncated law and two yielding loads, one in compression and one in uplift, while pile-to-pile interaction effects are account for by superposition. An alternative macro-model for pile groups formulated in the framework of multi-surface plasticity is also introduced. The prediction capability of both these models is then evaluated against the results of a set of centrifuge tests recently carried out on model foundations of annular-shaped pile groups subjected to different load paths. Although derived from different conceptual frameworks, the two models match in a very satisfactory way the experimental benchmark and can be both considered well-suited for a wide class of foundation engineering problems.