Reliability index for offshore piles subjected to bending

A first order second moment formulation is developed for analyzing the reliability of individual cross sections of piles driven on soft soils and subjected to random lateral static loads. The soil properties are expressed in terms of random p–y curves for a set of non-linear Winkler springs. The stiffness of the pile is taken as deterministic, but uncertainty about bending strength is accounted for. An algorithm is proposed and applied for determining probabilistic second moment estimates of internal forces and lateral displacements of a pile, taking into account both non-linear behavior and uncertainty about the parameters of the p–y curves. The cases studied include hypothetical piles driven on identical soft clays, and the loads correspond to the design conditions representative of several locations throughout the world. Very wide variations are found for the reliability index β of piles designed in accordance with ordinarily accepted regulations.