It is well recognized that the current AASHTO LRFD specifications for deep foundations (Chapter 10) are in serious need of updating. As a first step, NCHRP project 24-17 was conducted to begin addressing some of the current problems in that chapter, but primarily focused on the gathering of deep foundation data and the performance of calibrations to improve the resistance factors needed for deep foundation design.
The results from NCHRP Project 24-17, as well as other recently completed LRFD calibration work on deep foundations, must be incorporated or adapted to fit within the AASHTO LRFD specifications, and Chapter 10 needs to be rewritten to make it consistent with the design practice as described in the AASHTO Standard Specifications 17th edition. The rewriting of Chapter 10 is currently nearing completion through an FHWA contract, and the final steps in producing an agenda item for balloting will be undertaken by the AASHTO T-15 Technical Committee this year in preparation for submitting a formal ballot at the 2005 Bridge Subcommittee meeting. Through the recently completed review of Chapter 10, it has been discovered that the method for calculating drilled shaft resistance needs to be updated to the methodology provided in the updated FHWA manual on drilled shafts (O'Neil and Reese, 1999).
The objective of this study was to develop and populate a database for the behavior of single deep foundation elements under static load such that the measured strength and the parameters for the calculation of the nominal strength are readily available. The database will permit efficient computation of deep foundation resistance leading to simplification of the resistance factor calibration process.
Status: The project is complete. (NCHRP Staff: D. B. Beal)