Application of binomial system-based reliability in optimizing resistance factor calibration of redundant pile groups

Abstract

Recent research has indicated the potential of optimizing the design of pile groups using system-based reliability. Binomial distribution can be used to optimize the design of redundant pile groups. The application of binomial system-reliability is challenged by the need for determining a framework for calculating a key input variable related to the maximum number of defective piles a pile group can have without collapsing under applied loads, m factor. The objective of this research is to develop two robust finite element (FE) based methods to calculate m and utilize these methods in developing a framework for optimizing the calculation of pile resistance factors in redundant pile groups using binomial reliability. The methods were developed, verified, and applied to optimize the calibration of pile resistance factors for gravity loaded pile groups in sand. The resistance factors were optimized for the number of piles in a group, spacing of piles in a group, and the method of designing the pile as opposed to the current code approach of specifying a constant resistance factor for pile design irrespective of the pile group configuration. Analysis results show that resistance factors range from 0.31 to 0.96 for a system target reliability index of 3.0.