Unified system reliability approach for single and group pile foundations - Theory and resistance factor calibration

Load and Resistance Factor Design (LRFD) optimization is concerned with calibrating load and resistance factors against a pre-defined target safety level. The uncertainty in soil properties, the incomplete understanding of soil-structure interaction and the lack of statistical information slowed the development in the field of foundation optimization. A unified target reliability index is proposed for the design of a single pile, a non-redundant pile group, and a redundant pile group foundation. Resistance factors for axially loaded drilled and driven piles based on the statistical results of over 4000 pile load tests were calibrated using the proposed approach.