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The National Academies

NCHRP 12-116A [Completed]

Proposed AASHTO Specifications for Design of Piles for Downdrag

  Project Data
Funds: $420,000
Research Agency: University of Arkansas
Principal Investigator: Dr. Richard A. Coffman
Effective Date: 10/15/2020
Completion Date: 2/29/2024
Comments: The final deliverables have been received. A publication decision is pending.

BACKGROUND 

The AASHTO LRFD Bridge Design Specifications recognize that piles in settling soil experience downdrag forces from negative skin friction and may also move downward with the adjacent soil. Many bridges are constructed in areas where there is compressible soil or liquefiable soil, which necessitates the consideration of downdrag forces and associated settlement. Downdrag for static and seismic conditions has increasingly placed greater demands on existing and new foundations and also led to higher construction costs. Therefore, there is an immediate need to review the fundamental behavior of piles subject to downdrag and propose design specifications for the implementation of the neutral plane method for the evaluation of downdrag and the static and seismic design of piles.

 

OBJECTIVES

 

The objectives of this research were to (1) propose modifications to the AASHTO LRFD Bridge Design Specifications for the static and seismic design of piles for downdrag and (2) develop design examples to demonstrate the application of the proposed design specifications.

 

STATUS: The final deliverable has been received. Publication decision is pending.

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