Over the weekend, technicians working on the West Seattle Bridge removed the last two hanging work platforms that were affixed to the bridge for access to repairs. The removal of the work platforms indicates that bridge repairs are approaching completion as we prepare to restore the bridge on September 18.
In January of 2022, the work platforms were hauled into place. The platforms provided workers with secure access to the bridge’s underbelly so they could inject epoxy filling into outside cracks and subsequently apply carbon-fiber wrapping. The job was completed last week, and the work platforms are no longer necessary.
20 August time-lapse footage of the work platforms being lowered. Video credit: SDOT.
Epoxy injections into concrete fractures are a widespread method of repairing bridges and other structures throughout the world. The steel within concrete fractures is susceptible to corrosion from salt and water. The injection of epoxy protects the steel by penetrating deeply into the concrete to patch cracks and re-fuse the concrete. Crews have used over 240 liters of epoxy for crack injection in 2022.
Once cracks have been filled, workmen wrap carbon-fiber sheets like a cast over vital components of the bridge. The carbon-fiber material is as robust as steel and weighs one-tenth as much, preventing eventual cracking of the concrete beneath. During the final phase of bridge repairs, more than 100,000 square feet of carbon-fiber wrapping was added.
This video from earlier this year shows employees working on epoxy filling and carbon fiber wrapping. More photographs and videos of bridge construction are available on YouTube and Flickr.
These restoration techniques work in tandem with the recently finished post-tensioning system, which consists of approximately 60 miles of steel cables that serve as the bridge’s backbone. These three rehabilitation techniques (epoxy injections, carbon-fiber wrapping, and post-tensioning) significantly boost the bridge’s strength, enabling it to withstand decades of heavy traffic, temperature fluctuations, and extreme summer and winter weather.
The West Seattle Bridge contains post-tensioning cables. Tim Durkan is given photo credit.
The following additional tasks must be accomplished prior to the bridge’s opening:
Restore the bridge deck’s pavement
Perform safety tests and conduct a thorough inspection of the repairs
Install permanent inspection platforms within the framework of the bridge
Remove construction equipment and make the bridge public-ready.