Supporting the New Northbound Bridge Deck

From ODOT-

When most people think of the new Willamette River Bridge, the attractive arch deck sections spanning the river easily come to mind. But did you know that there are other types of supports for the bridge deck on either end of the arches?

One type of support being used is called a box girder. They are being built at the south end of the new northbound bridge, over Franklin Boulevard and the Union Pacific Railroad.

Driven steels piles on the south end of the project are used to established the falswork in support of construction of the box girder sections before the concrete sets and post-tensioning occurs.  Crews cut and cap the piles with a series of steel beams that form the critical flooring of the box. 

New columns taking shape on both sides of the railroad track on the south end of the project will support the box girder and top deck of the new northbound bridge.

To complete the box girders, carpenters build temporary wooden formwork that shape both the inside and outside of the boxes, ironworkers install rebar to provide reinforcement to the concrete, and then the concrete is poured. After the concrete cures and is post-tensioned, the falsework forms are removed, revealing the new boxes. The completed box girders are hollow and can be from 5 to 12 feet high.

Here, wooden and steel falsework takes shape where the new northbound bridge will touch down on the south end of the project.

Smaller, solid concrete beams are used at other locations on the bridge. Some are cast in place, while others are precast off site and transported to the project for installation.

The beam type used depends on the span length and strength needed to support the bridge at various locations.

Farther north, work is in the early stage on the columns and the arches that will support the deck beams where the bridge crosses the river.

We’ll take a closer look at the arch construction in a future blog post.