Assessing Initial Stiffness Models for Laterally Loaded Piles in Undrained Clay: Robust Design Perspective

The hyperbolic p-y curve method is commonly used to design laterally loaded piles. The initial stiffness (K) and the ultimate resistance per pile length (pu) are the two key parameters that are required to determine the hyperbolic p-y curve. Multiple competing models are available for determining the term K, which makes it difficult for the designer to select a proper initial stiffness model. Six existing initial stiffness models are assessed and compared from the robust design perspective in this paper. Specifically, a framework based on the concept of robust design is proposed for assessing these initial stiffness models considering multiple objectives such as safety, cost, and design robustness. This framework is illustrated with an example, the design of a laterally loaded pile in clay using the p-y curve method. Based on the outcome of this example study, the most preferred initial stiffness model for the laterally loaded pile design is suggested. To enhance applicability, the proposed framework based on the robust design concept is simplified and illustrated with a spreadsheet solution.