After nearly half a century of service, the world's longest floating bridge is now clogged by traffic, showing its age, and in need of replacement. The Washington State Department of Transportation (WSDOT) is building a new State Route (SR) 520 floating bridge capable of withstanding heavier windstorms, and moving significantly more people and goods.Much like a large floating marine dock, the new bridge will consist of concrete pontoons moored to 58 deep water anchors by 8 miles of steel cables. The bathymetry and subsurface conditions of Lake Washington pose unique challenges for the moorage of floating pontoons. The water depths at the anchor locations vary from 30 feet to 210 feet, and subsurface conditions range from very dense to very soft and include soils with unique engineering properties. These conditions necessitated the use of three anchor types: drilled shaft, gravity, and fluke.

No abstract

No abstract

Anchoring floating structures in deep water can be challenging because of varying water depths, soil types, uses, and environmental loads. Three different anchor types, drilled shaft, gravity, and fluke anchors were used to meet these challenges for the new SR520 Evergreen Point Floating Bridge and Landings project in Seattle, Washington. The anchors were designed to resist the horizontal and vertical components of the maximum resultant anchor cable load of 570 tons under static and seismic conditions. The anchors are being proven through exhaustive full-scale field load tests. Verification tests are being loaded to a maximum of 570 tons, performance tests to 425 tons, and proof tests on all remaining production anchors to 300 tons. All anchors tested to date, including all performance and verification tests for all three anchor types, have met all (creep and total displacement) testing requirements.

No abstract