SR 520 Floating Bridge

The project team was responsible for demolishing the existing bridge, fabricating the large prestressed, precast concrete floating pontoons (mostly 360 ft by 75 ft by 28 ft), transporting and assembling the pontoons, installing anchors and anchor cables, and constructing the elevated roadway above the pontoons. Highlights of SGH’s work include the following:

• Developed a demolition work plan for dissembling the old bridge pontoons
• Designed a value engineering option to use a post-tensioning system for assembling and joining the floating bridge pontoons
• Performed dynamic structural analyses to evaluate the bridge’s structural integrity during varying construction stages and storm conditions
• Developed multiple monitoring and damage response contingency plans against accidental damages or larger-than-expected storms
• Performed mooring, floating stability, and ballast analyses for towing, mooring, assembly, and separation of floating pontoons
• Designed the mooring facilities and fenders for berthing and towing large concrete floating pontoons and construction vessels
• Designed cable anchor test frames used to evaluate the structural integrity of anchor cables
• Designed heavy lifts using floating derrick cranes used to install and remove bridge deck panels, girders, and columns
• Evaluated means and methods for installing, removing, and relocating anchor cables on the existing and new bridges to minimize the damage risk