Load and Resistance Factor Design of Driven Piles

Abstract

A load and resistance factor design (LRFD) bridge specification has been accepted by the AASHTO Bridge Committee. This design approach is now being implemented for highway bridges in the United States, including the design of driven pile foundations. To test the new specification's practicality and usefulness, an example problem has been solved using it. In the example, a pipe pile was designed to be driven into a granular soil to support a bridge column subjected to a factored axial compression load of 10 MN. The nominal strength selected for the pile was 1.58 MN with an estimated length of 25 m. Since the resistance factors are defined by the specified quality control procedures, the number of piles required in the foundation also depends on the quality control. In this example, the number of piles required varied from 15 to 8 with improved quality control, for a savings of almost half of the piles. This example indicated that the new AASHTO LRFD specification for driven pile design can be used effectively to produce a more rationally designed foundation. Some modifications should be made to include additional serviceability limit states, and additional research may indicate that changes should be made in some of the resistance factors.