Design Build of New NY Bridge Foundations-Paper

Paper

Pdf Summary

The New NY Bridge project replaced the aging Tappan Zee Bridge with two 3.1-mile crossings over the Hudson River. Awarded as a $3.14 billion design-build contract, it was New York State’s largest such contract and a major early use of alternative project delivery in the state.<br /><br />Foundation design had to accommodate highly variable geology: deep, very soft clays and silts, glacial till, and bedrock that was steeply sloping and locally more than 750 feet below the riverbed. The solution combined more than 1,000 large-diameter steel pipe piles—including friction piles in clay and end-bearing piles at till or rock—with drilled shafts at the Westchester landing and other foundation types near shore.<br /><br />Accelerated design and review packages enabled test piles in permanent locations by August 2013 and production driving soon afterward. Foundation capacities were assessed using prior and project-specific testing, including 17 full-scale static pile tests, extensive dynamic testing, lateral tests, and a drilled-shaft load test. Results generally confirmed design capacities, while monitoring also documented substantial capacity gains as friction piles set up over time.<br /><br />Construction relied on multiple marine equipment work fronts, long spliced piles, carefully staged driving procedures, and underwater air-bubble systems to reduce pile-driving noise and protect fish. Precast concrete pile-cap tubs were used extensively on approach structures; their standardized designs improved fabrication, sequencing, and installation. The much larger main-span caps were built using suspended precast floor panels, temporary formwork, synchronized strand jacks, and large-volume concrete pours.<br /><br />The project demonstrates how design-build coordination among the owner, designers, and contractor can accelerate design and construction while tailoring foundation solutions to challenging ground conditions, construction equipment, and environmental requirements.

Keywords

New NY Bridge

Tappan Zee Bridge replacement

Hudson River crossings

design-build contract

foundation design

steel pipe piles

soft clays and silts

drilled shafts

pile testing

construction sequencing