Rendering of the new Willamette River Bridge

Thursday, December 2, 2010

Arch ribs photo story- part 2 of 4

From ODOT- Over the last few months we've posted photos of work on the Willamette River Bridge, but as the southbound bridge arches near completion, let's look back at how they took shape. We've seen how the crews installed a rebar cage that provides critical strength for the foundation of the bridge. Next we'll explore the point where the arch ribs touch down - a point where we can begin to see the construction of the arch frame.

On top of the drilled shafts that anchor the bridge in place sit custom-designed shaft caps. The caps at each point where the arch ribs touch down are unique, created to perfectly match with the ribs and the bridge's vertical supports. At the single touch point in the middle of the Willamette River, building the shaft cap was exceptionally challenging. This point will support not only the north- and southbound arch ribs, but also two vertical pillars. This center shaft cap is 8 feet wide, 12 feet tall and 6 feet thick. It is shown here with rebar cages coming out of the top to frame the vertical supports and the arch rib connection points sprouting from its sides.

While one part of the team dug deep below the river, another was busy building a frame high above the work bridge to the support for the falsework that would shape the reinforced concrete arches. During construction, this frame will provide critical support to both the arch and the crews working on its construction.

Next time: framing the arches and building the skeleton.

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