Verification of LRFD approach for piles in sand and mixed soils

Abstract

The potential consequences of switching the design and construction of bridge foundations in sand and mixed soil profiles from an interim procedure based on Allowable Stress Design to the Load and Resistance Factor Design (LRFD) procedure were examined. Independent data of 451 production steel H-piles driven in sand and 173 production steel H-piles driven in mixed soil profile were used to evaluate the adequacy of the regionally calibrated LRFD procedure and investigate its economic implications. This study concludes that the regional LRFD procedure will increase the plan pile length by 25% for sand and 12% for mixed soil profile as opposed to 86% and 93%, respectively, if the American Association of State Highway and Transportation Officials (AASHTO) procedure had been implemented. Despite the additional cost incurred by switching to the regional LRFD procedure, it satisfies the target reliability index of 2.33 for a redundant pile group and the 1% probability of failure stipulated in the AASHTO LRFD Specifications. Alternatively, it can be stated that the currently used method has a reliability index of 1.7 for sand and 2.00 for mixed soil profile with approximately 30% and 10% more probability of failures, respectively. Although the research and findings presented in this paper are specific to a local area, these methods could be adopted globally to facilitate the implementation of the regional LRFD procedure in bridge foundations.