Case Study on the Frederick Douglass Memorial Bridge and the Use of Large Diameter Open End Steel Pipe Piles, Washington, DC-Paper

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The Frederick Douglass Memorial Bridge replacement in Washington, DC, uses 60-inch-diameter driven open-ended steel pipe piles for its main spans and 36-inch piles for a temporary construction trestle. The project’s preliminary design favored drilled shafts, partly because very dense and stiff soils were expected to make pile driving difficult. The Design-Build team instead selected pipe piles, reducing the bridge layout to two land abutments and two river piers.<br /><br />The site profile includes soft alluvial deposits, Pleistocene terrace soils, and strong Cretaceous Potomac Formation clays, sands, and gravels. Because the behavior and capacity of large-diameter open-ended piles are not well covered by established design guidance, engineers considered both unplugged and partially plugged pile assumptions. Capacity estimates primarily used the Meyerhof method, modified by Higgins for local conditions.<br /><br />A substantial load-testing program combined high-strain dynamic testing (PDA) with Statnamic testing on sacrificial test piles. Results showed that both pile sizes developed most of their resistance through shaft friction—about 88–91% on average—with relatively little end bearing. The piles showed no significant evidence of plugging under the tested loading conditions. Comparisons with predicted external shaft friction indicated substantial additional internal shaft friction, especially along the impact-driven portions of the piles. This effect appeared greater in the 36-inch piles than in the 60-inch piles.<br /><br />The findings supported the modified Meyerhof/Higgins approach and the project’s unplugged design assumptions when internal shaft friction was included. The API P2A method generally underpredicted capacity and led to longer estimated pile lengths. The study highlights the value of project-specific load testing and provides data to inform future design of large-diameter open-ended pipe piles.

Keywords

Frederick Douglass Memorial Bridge

open-ended steel pipe piles

driven piles

pile testing

Meyerhof method

Higgins modification

shaft friction

Statnamic testing

dynamic load testing

unplugged pile design