Reliability-Based Optimization of Design Code for Tension Piles

A reliability-based calibration of a design code for offshore tension pile foundations in clay is presented by an example. The design against pullout in ultimate loading is considered. The calibration is performed by means of a numerical optimization technique in conjunction with probabilistic and deterministic models for load and capacity. The probabilistic models allow for predictions of the reliability against pullout. The deterministic models express design load and design capacity in terms of characteristic values and partial safety factors. The code calibration consists of determination of the partial safety factors such that—over a specified scope of code—designs with reliabilities with minimum deviations from some prescribed target reliability result when applying the deterministic models with this particular set of partial safety factors. For tutorial purposes, the scope of code is represented by a limited number of design cases, and emphasis is placed on the demonstration of the code calibration principles and a proper formulation of the code format.