The connection between solid ground and the world’s longest floating bridge—a new one that will prove even longer than its predecessor at 7,578 ft—doesn’t happen lightly.

Crews working for the Washington State Dept. of Transportation in Seattle recently completed the transition by installing a hinged transition span that acts as a threshold between the highway’s floating roadway and its stationary, elevated segment near Lake Washington’s eastern shore.

The new transition span includes eight girders, each 190 ft long and weighing 45 tons.

The substantial span operates somewhat like a hinge on the door, according to information provided by WSDOT. The span moves with the floating bridge while connecting to the highway’s stationary east high-rise, transitioning between the two and mitigating the movement in the bridge along the way.


The span supports the new bridge’s westbound lanes and a bike/pedestrian path at the east end of the new floating bridge. A smaller hinged span for the eastbound lanes was installed last June. Similar spans will get added to the west end of the bridge prior to the bridge’s spring 2016 opening.

WSDOT says that installing the hinge marks a significant milestone for the project. All of the new bridge’s 77 pontoons now sit on Lake Washington. Joined and anchored pontoons stretch well over halfway across the lake and work continues in Seattle on the West Approach Bridge North Project. 

Tim Newcomb is Engineering News-Record’s Pacific Northwest contributor. He also writes for Popular MechanicsSports Illustrated and more. You can follow him on Twitter at @tdnewcomb or visit his website here.