Governor Mario M. Cuomo Bridge

The new NY bridge project produced a crossing of rather epic proportions.

The $3.98 billion undertaking—one of the largest transportation design-build contracts in the United States to date—replaced the old Tappan Zee Bridge with the new 3.1-mile-long, twin-span Governor Mario M. Cuomo Bridge over the Hudson River, located approximately 20 miles north of New York City. It is designed for a 100-year service life and carries a newly enhanced regional bus service in addition to typical road traffic; the foundations are designed to carry future commuter/light rail tracks on structures erected between the two spans. The largest bridge project in New York history provides greater traffic capacity while improving operations and safety for motorists crossing one of the widest parts of the Hudson River.

The new bridge features parallel 3.1-mile-long structures, each with a 2,230-ft, cable-stayed main span and ten 1,750-ft, five-span continuous approach units composed of 350-ft steel girder spans. It provides eight general traffic lanes, plus dedicated bus lanes and shoulders for emergency access. The design team selected structure types with proven service life and efficiency in order to maximize span lengths and minimize foundation demands while engaging local trade expertise. The approach structure design maximized span lengths using a long-span steel girder sub-stringer system with an average span length of 350 ft, so fewer foundations were needed. In the deep clay area, the highest-capacity friction piles (2,100 tons) ever used in these types of soils have proven successful.

As the lead designer, HDR analyzed, designed, and detailed the approach structure steel girder sub-stringer system, which included composite steel girder design, sub-stringer design, and cross-frame design in accordance with AASHTO LRFD Bridge Design Specifications. The team created 3D finite element models to analyze the steel system as a whole and to develop demands for design. Half of the units were located on a curved alignment, which required the design of continuous curved steel girders in which the effects of torsion were considered in both the temporary and permanent state.

Design of the approach spans was based primarily on five-span continuous units. The steel framing supporting each roadway deck included five main girders and four substringers to minimize foundation loads. Overall, 110,000 tons of fabricated structural steel went into the project.

Choosing steel allowed much of the superstructure construction to be modularized. The relatively light superstructure allowed for large picks, saving time, minimizing the number of construction activities that needed to occur at elevation, and providing a safer construction process. The light steel superstructure also allowed the team to optimize the pier and foundation designs. The reduced mass and increased flexibility of the superstructure reduced the gravity loads and seismic demands, when compared with other structure types the team considered.

Most of the approach structures are founded on either 3-ft- or 4-ft-diameter steel pipe piles, and the towers, anchor piers, and approach piers adjacent to the anchor piers are founded on 6-ftdiameter steel pipe piles. A portion of the site over Metro-North Railroad tracks, where crane access was limited, highlights the flexibility of a steel superstructure. HDR worked with the contractor to develop a steel girder system that could be launched from the Westchester abutment in multiple phases during overnight track outages. The designer worked hand-in-hand with the erection engineer up front to ensure that the design could accommodate variations in loading during launching activities, which minimized changes during the fabrication process.

Project Team

• Steel fabricators:

  • High Steel Structures LLC, Lancaster, Pa. (approach unit superstructure, also detailer) *AISC MEMBER* *AISC CERTIFIED*

  • W&W | AFCO Steel, Greensboro, N.C. (approach unit superstructure, also detailer) *AISC MEMBER* *AISC CERTIFIED*

  • Canam-Bridges, Point of Rocks, Md. (main span superstructure) *AISC MEMBER*

  • L&M Fabrication & Machine, Inc., Bath, Pa. (main span superstructure) *AISC MEMBER* *AISC CERTIFIED*

• Additional detailer: Tenca Steel Detailing, Inc., Quebec City *AISC MEMBER* 

• Design/builder: Tappan Zee Constructors, LLC, a joint venture of:

  • Fluor

  • American Bridge Company *AISC MEMBER* *AISC CERTIFIED*

  • Granite Construction Northeast

  • Traylor Bros., Inc. *AISC MEMBER*

• Engineer: HDR, New York

• EOR of main span: COWI, New York

• Owner: New York State Thruway Authority, Albany, N.Y.