Behind the orange cones: the skeleton of the bridge

From ODOT-

In our latest video, crews tie together miles of rebar to form the intricate web of steel reinforcing bars that is the unseen skeleton of the entire bridge. The rebar ranges from as small as one-half inch in diameter up to 2 1/4 inches across.



For this project, we use the largest diameter rebar available, which weighs 14 pounds per linear foot. These big steel bars are so heavy that it takes several steelworkers to move them into place and tie them into the reinforcing framework that supports the bridge piers and arches.



It’s fascinating to see up-close the cages that will become the concrete columns supporting the bridge. I interviewed ODOT Quality/Quantity Coordinator Thor Alvarado about the training and experience needed to work with this heavy and intricate material.



Thor’s job is to inspect bridges under construction throughout the state. His experience is valuable on a complicated project like ours because he makes sure bridges are built properly, safely and within budget.



According to Thor, the biggest challenges of working with rebar are harsh weather and lifting the long and heavy steel bars into place. He says teamwork is important because it’s dangerous work.



Do you know what happens to the rebar if steelworkers try to bend it with a torch? Watch the video to find out!



And feel free to post your comments and questions. Your feedback is important to us.

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.

Miles of steel create strong skeleton for new bridge

From ODOT-

Reinforcing steel, or rebar, is one of the most integral parts of a bridge even though you never see it.

Ironworkers from Manske Construction form and tie together miles of rebar cages, creating the strong skeleton for the piers that will support the new northbound I-5 bridge. Then, they install the steel framework into the drilled shafts before the concrete is poured to form piers, creating the part of the bridge that you do see.

The span of the rebar ranges from as small as 1/2 inch in diameter up to 2.25 inches. For this project, we use the largest diameter rebar available, which weighs 14 pounds a linear foot. The new southbound bridge contains 2.7 million pounds of rebar, the weight of more than 3 fully loaded jumbo jets at takeoff. The northbound bridge will contain a similar amount of reinforcing steel.



Ironworkers tie the steel rebar to form the pier cages in a work area in Alton Baker Park, just north of the Knickerbocker Bridge.

Ironworkers and welders build the steel structures by typing together miles of rebar.

A large crane lowers the tied rebar down into a shaft to form an abutment wall.

Here is how the rebar looks inside of the pier shaft, before the concrete is poured. The bridge pier shafts average about 35 feet deep below the riverbed.