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SDOT: High bridge repair: Steel cables installed in the bridge; beginning the tightening process for the post-tensioning system | Westside Seattle
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SDOT: High bridge repair: Steel cables installed in the bridge; beginning the tightening process for the post-tensioning system
SDOT: High bridge repair: Steel cables installed in the bridge; beginning the tightening process for the post-tensioning system
Fri, 07/15/2022
Information from Seattle Department of Transportation
This week, we finished installing the nearly 250,000 feet of steel cable needed for the new post-tensioning system inside the bridge. With these cables in place inside the protective ducts, we started the process of tightening the post-tensioning system by pulling on the cables with hydraulic equipment.
We’ll begin the tensioning process by tightening each steel cable to about 20% of its final tension force. Next, we will tighten each cable in a specific sequence to ensure that the bridge structure is compressed evenly and consistently throughout the process. Once the cables are fully tensioned, the concrete in the bridge structure will be stronger than ever. The next step will be to begin our final phase of epoxy crack injection and carbon-fiber wrapping work.
We inserted rods and tightened them into a concrete anchor block. This further strengthens the concrete and prepares it for the forces of the post-tensioning that will make the high bridge stronger. SDOT Photo
Steel cable is installed through protective ducts as part of the West Seattle Bridge’s newest post-tensioning system. SDOT photo
We are also continuing to reinforce the post-tensioning anchor components by inserting and tightening rods into the concrete anchors. This strengthens the connection between the post-tensioning system and the surrounding structure.
As we move through these final phases of repairs, we continuously inspect the bridge and check our work. Earlier this month during a routine crack inspection, we discovered a spall area that was about 2 by 9 feet. Spalling is when a part of the concrete surface naturally weathers, chips or breaks away. After looking into the spall, it’s clear that it is not related to the issues that are currently being repaired and it does not indicate any structural or systemic issues. We will be able to repair this spall with no impact to the bridge reopening schedule.
Low bridge rehabilitation: West span platform hoist complete
Last weekend, we successfully hoisted the final two platforms to the underside of the low bridge’s western span. This effort is part of our low bridge rehabilitation work that will strengthen the low bridge to keep it strong for years to come.
We will begin epoxy crack injection and carbon-fiber wrapping to reinforce the concrete on the low bridge in the coming months. This is the same concrete strengthening method we’ve been using on the high bridge.
