Evaluation of Regionally Calibrated Load and Resistance Factor-Design Method Used for Driven-Steel H-Piles

Abstract

Since October 2007, the Federal Highway Administration (FHWA) has required the implementation of LRFD methods in all new bridge designs, including pile design. The resistance factors provided nationally for LRFD of driven piles are relatively conservative. Therefore, the Iowa Department of Transportation and Iowa State University collaborated and established regional resistance factors that are more efficient than those provided in the AASHTO Specifications, which are complemented with improved construction control methods. Iowa's LRFD guidelines for piles have been used in enough completed projects since 2012, allowing an assessment of the accuracy of the regional resistance factors and construction control methods. The piles used in these projects included both end-bearing piles in rock and friction piles. The friction piles were installed in cohesive, noncohesive, and mixed soil sites. The evaluation for the different pile categories and soil types found that the regional LRFD resistance factors developed were successfully applied in Iowa's driven pile design and effectively reduced the piles' contract lengths, resulting in cost–benefit over AASHTO's recommended resistance factors.