Evaluation of ultimate limit state design of piles subjected to drag force based on Canadian Highway Bridge Design Code and AASHTO LRFD Bridge: field study and numerical modeling

Consideration of drag force in the geotechnical ultimate limit state (ULS) design of piled foundations influenced by ground settlement has posed a challenge due to inconsistencies across different codes. This study compares the geotechnical ULS design provisions of two widely used North American bridge design codes, AASHTO and Canadian Highway Bridge Design Code (CHBDC), through a case study of a production steel H-pile subjected to embankment-induced loading. The investigation includes direct field measurements, pile dynamic analysis, and numerical simulations. AASHTO incorporates drag force in geotechnical ULS design, leading to conservative estimates, whereas CHBDC omits it from ULS calculations. However, due to differing load and resistance factors and the magnitude of the drag force, CHBDC's design provisions were found to yield more conservative results in this study. Furthermore, adopting pile capacity derived from restrike measurements versus end of initial driving in dynamic analysis was found to provide higher resistance in geotechnical ULS design due to shaft setup.