SOURCE: ENR | August 1, 2019
Sound Transit is installing light rail track on a floating bridge connecting Seattle to Bellevue, requiring special engineering to safely construct. Crews are currently starting installation of the “trickiest” part of the project– transitioning light rail vehicles onto the floating bridge.
According to ENR, the specialized track attachments will “minimize weight and isolate stray current from the electrical system that powers the trains.” While the process of installing the rail is finally underway, the article reports that the project has been in the preparation stage for several years.
The I-90 bridge has a floating span of nearly 1 mile, connecting to fixed bridges on either side. To get a 300-ton light rail train across, the concept has to include a 43-foot curved platform that can move freely.
While the process of installing the rail has been underway for a year, the planning and preparation took several years to execute. To begin, crews completed post-tensioning of the bridge’s pontoons, which reinforced concrete and tensioned strands.
According to the article, nearly 9,000 specially constructed concrete blocks will be affixed to the bridge deck, with steel tie bars placed between them. So far, crews have installed eight of these track bridges. The light rail schedule is set for completion at the end of 2019.
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