Calibration of Resistance Factors Needed in the LRFD Design of Drilled Shafts: Tech Summary

The load and resistance factor design (LRFD) has been used increasingly and has become mandatory for the design of all bridge
projects funded by the Federal Highway Association (FHWA). Compared to the allowable stress design (ASD) method, LRFD can
achieve a compatible reliability between the bridge superstructure and substructure. The uncertainties of load and resistance are
quantifi ed separately and reasonably incorporated into the design process. Therefore, this reliability-based design approach will
generally produce a more effi cient and consistent design than the traditional ASD factor of safety approach. To achieve these goals
many researchers have been working to develop a reasonable way to implement the LRFD method in bridge substructure design and
to determine appropriate resistance factors for diff erent regional soil conditions.