The Abernethy Bridge's Changing Silhouette
A new bridge column emerging from the water between a work platform and the existing bridge support.
If you've recently driven your car across the Abernethy Bridge or floated your boat beneath it, you may have noticed our most recent project milestone: the bridge's new support columns emerging from the water. These seismically-upgraded supports will rise into the air alongside the bridge in the coming months—and help make the Abernethy Bridge the first earthquake ready freeway bridge to span the Willamette River in the Portland area.
While only recently visible above the surface of the water, this accomplishment has been many months in the making. First, teams needed to bore deep (really deep!) all the way down to the bedrock 200 feet below the surface. Then they needed to anchor the new bridge support shafts into the bedrock. No standard equipment was up to the task. A new oscillator – lovingly nicknamed Oscar – was built in Germany and shipped to Oregon to accomplish this. Bedrock doesn't move during earthquakes, so these new supports will ensure the bridge is stable even during a Cascadia-level event.
Before the start of the Abernethy Bridge construction, April 2022 (left) and during construction May 2023 (right).
These new, secure columns will continue to rise into the air until they are level with the existing bridge supports. Then, sometime in 2024, construction crews will slide the existing bridge decks outward eight feet in both directions towards these new support columns. A 16-foot workspace will remain in the center after the bridge slides are complete. The bridge will then be widened from the existing spans toward the center in order to join the bridge spans back together. A helpful animation is on the project website that depicts how these improvements will provide the needed surface area to have three travel lanes in each direction and auxiliary lanes to make merging on and off I-205 safer and easier. When construction is complete, the Abernethy Bridge will be the first earthquake-ready freeway bridge to span the Willamette River in the Portland area. These seismic upgrades, auxiliary lanes, and other safety improvements that are part of the I-205 Improvements Project will make travel to and through the southern metro area safer for everyone.
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