Technical details
Client
Washington State Department of Transportation
Dates

September 2011: Construction started
April 2016: The new bridge was opened to traffic

Missions
Conceptual design, detailed design, and construction engineering
Location
Seattle, Washington, United States
Activity
Floating Bridge, Precast Segmental

The SR 520 Evergreen Point Floating Bridge is a 2,652m long project crossing Lake Washington near Seattle, in the USA, combining both floating and fixed base bridge segments.

A unique design

The unique construction consists of a 5,135ft (1,566m) long low-rise structure of precast segments supported at a typical 9m spacing on top of the floating bridge. This innovative two-way post-tensioned structure is designed to be low profile, with a maximum thickness of 2.5ft (0.76m) with a total deck width of 113’-4” (34.6m) carrying 6 lanes of traffic and a pedestrian walkway.

SYSTRA is responsible for technical oversight and construction engineering for the cast-in-place segmental twin box-girder long span at the east side of the project, which has a total length of 192m and a main span of 98m. Both structures are pre-designed to be expandable for two additional mass transit lanes in the future.

Numerous awards

The SR 520 Evergreen Point Floating Bridge has received the following honors:

  • 2017 American Council of Engineering Companies
  • Grand Conceptor Award
  • 2016 Design-Build Institute of America
  • National Award of Merit
  • Excellence in Design

Project Key figures

  • Total length: 1,566m
  • Width: 34,6m
  • Thickness: 0,76m
  • 6 traffic lanes and a pedestrian walkway
  • 77 concrete pontoons
  • 58 anchors
  • 74,000 vehicles per day

The project in pictures