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Giant hinged span coming to world’s longest floating bridge

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Date:  Thursday, June 26, 2014

Contact: Contact: Ian Sterling, WSDOT communications, 206-819-7230

Installation on new SR 520 bridge begins Friday

MEDINA – What will be the world’s longest floating bridge is getting a new feature. Contractor crews for the Washington State Department of Transportation will begin installing a massive, hinged transition span (pdf 2.52 mb) on Friday, June 27, and will have it fully in place the following day.

Five girders make up the span, each of which is 190 feet long and weighs 45 tons. Once assembled, the transition span will serve as the threshold between the moveable, floating bridge and the highway’s stationary, elevated segment near Lake Washington’s eastern shore.

“The span is a unique piece of hardware integral to the new floating bridge,” says Deputy Construction Manager Greg Meadows for WSDOT. “In the same way a hinge allows a door to move while the frame stays rigid, this span moves up, down and side-to-side along with the floating bridge, while the highway remains stationary.”

Washington state has four of the five longest floating bridges in the world, Meadows noted, and the new bridge’s hinged transition span is bigger than any previously installed here. Along with the new floating bridge itself, the span is engineered to last at least 75 years and will carry tens of thousands of vehicles every day across Lake Washington.

The span will support the new bridge’s roadway for eastbound lanes at the east end of the new floating bridge. A wider hinged span for the westbound lanes and a cross-lake bicycle/pedestrian path will be installed later. Similar spans will also be installed at the west end of the floating bridge in 2015.

WSDOT would like to remind drivers to be cautious near the worksite. The installation process, employing a large derrick crane, is expected to be a visual distraction. Drivers approaching the construction site from the existing SR 520 floating bridge should pay extra attention to driving conditions and the road in front of them and be mindful that other drivers could slow down or brake as they pass the construction site.

The installation is one of many milestones for the SR 520 Bridge Replacement and HOV Program. Sixty of the new bridge’s 77 pontoons are now constructed, with the remainder scheduled for completion by early 2015. The Eastside Transit and HOV Project will be finished later this summer, as will the new West Connection Bridge. Late summer also will see the start of construction on the corridor’s West Approach Bridge North. The new SR 520 floating bridge will open to drivers in the spring of 2016.


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