Large Diameter Auger Cast Piles at Audi Field, DC United's New Soccer Stadium-PPT Presentation

PPT Presentation

Pdf Summary

The DC United soccer stadium at Buzzard Point in southwest Washington, D.C., was built in a former industrial area targeted for neighborhood redevelopment. The original foundation concept used driven precast concrete piles, large pile caps, and ground improvement. A value-engineered alternative replaced it with single large-diameter augercast piles—18, 36, or 48 inches in diameter—supporting axial loads up to 1,450 kips and lateral loads up to 300 kips. The piles were connected by grade beams, without pile caps.<br /><br />Design requirements included strict settlement and pile-head deflection limits, consideration of downdrag, and partial pile-head fixity. Conventional single-pile analysis with LPILE posed challenges: empirical p-y curves based on SPT data were considered insufficient, and analyzing hundreds of load envelopes under different fixity assumptions would have required roughly 950 separate analyses.<br /><br />Site-specific DMT and CPT testing improved estimates of soil strength and p-y curves, supported eliminating downdrag loads and ground improvement, and informed the design. The team also used FB-Multipier, a three-dimensional finite-element tool that could model grade beams and pile caps with their stiffness properties. Design coordination was complicated by differing interpretations of partial fixity and software limitations; an additional moment release was introduced at pile heads to reach an approved, conservative design.<br /><br />Three Osterberg-cell (O-cell) tests were performed to validate pile properties, though one showed divergence below the cell due to its placement. A calibrated model also supported lateral load assessment.<br /><br />Key lessons were to use site-specific data and appropriate analysis tools, align the design team on assumptions such as head fixity, and validate the design where possible. The presentation cautions against combining overly prescriptive design parameters with performance-based criteria.

Keywords

DC United stadium

Buzzard Point

augercast piles

pile foundation design

ground improvement

lateral load analysis

partial pile-head fixity

DMT CPT testing

FB-Multipier

O-cell tests