SEATTLE — One of Sound Transit’s latest light rail projects is featuring what the transit agency says is a first-of-its kind rail line on a floating bridge.
The Seattle Times reports that after more than a decade dealing with the technical challenges involved, the agency is installing tracks on the Interstate 90 bridge across Lake Washington as part of a route from Seattle to Bellevue and Overlake, Wash., scheduled to open in 2023.
The most significant part of the engineering to make the project work are eight steel platforms, called “track bridges,” where the rails pass over the hinged joints of the highway bridge, which can rise or fall up to 2 feet depending on water levels, and also move because of wind, waves and traffic. The track bridges will allow the rails to stay in line even when the platforms move to accommodate the motion of the bridge, thanks to flexing bearings similar to those used to protect buildings from earthquake motion. Trains will be able to operate at 55 mph across the bridge.
To offset the additional weight on the bridge from the rail line, concrete barriers along tracks the are being replaced with cable fencing to prevent a derailing train from falling into the lake.
— Updated at 4:55 p.m. CDT on July 25 to restore missing words in last paragraph, clarify attribution on claim that floating bridge is a first.
The Rutland Railroad had a floating bridge on the Addison Branch linking their mainline at Lecister Junction north of Rutland the the D&H mainline. It was abandoned early as it connected no major points.
The last paragraph makes no sense to me.
The Milwaukee Road had a floating bridge between Marquette, Iowa, and Prairie du Chien, Wisconsin, on the line from Milwaukee/Chicago to Rapid City, South Dakota. The bridge was taken out when the through passenger train to Rapid City was taken off. Bits of the route are visible from the highway bridge and the track still extends west of Prairie du Chien to the first island. I believe there was another on the Milwaukee Road across the Mississippi in Minnesota for a branch line into Wisconsin.
My days as a combat engineer with the 237th Engineering battalion, US Army, we built floating bridges, the M4T6 floating bridge, which were used to cross anything from M60 tanks to light vehicles. Wow, crossing at 55mph! Cool.
Mr. Friedman, Lake Washington is deep and has a muddy bottom, so putting in bridge piers would have been problematic.
The light rail line that is currently under construction goes along Bellevue Way after exiting the bridge to the eastside of downtown Bellevue where I understand they will be tunneling. Then exiting downtown will cross I-405 freeway and will run along the south side of the Washington State Route 520 freeway to the Overlake district. Eventually, from what I understand, the line will go to downtown Redmond.
There is no town called Overlake, Washington, It is the Overlake District of Redmond, Washington.
Yeah , that last paragraph is stupid .
What is up with Seattle’s obsession with floating bridges?
Old news, this was known well over a year ago, if not more than that…also, nothing that hasn’t been done before for other forms of transportation.