Prof. Raffaele Di Laora

The conventional design of pile groups under vertical eccentric loading typically defines the ultimate external load as that which causes failure of the most stressed pile, while lateral loads are usually treated separately. Although safe, this approach is inherently conservative: it disregards the system’s ductile capacity and, in the case of reinforced concrete piles, the crucial influence of axial load on the sectional yielding moment. Moreover, the interaction among the three components of external loading, often detrimental, is generally neglected.

Recent advances have introduced more integrated design methods based on failure envelopes, which capture these coupled effects within a unified framework. The paper will examine the formulation and construction of such envelopes, highlighting their accuracy, simplicity of implementation, and the significant potential they offer for more rational and economical design at the Ultimate Limit State. Building on this basis, the discussion extends the concept to the Serviceability Limit State, outlining a consistent and practical pathway from ultimate to serviceability design. Selected applications demonstrate the effectiveness and versatility of the proposed approach in real engineering contexts.