Superstructures and Substructures

Construction crews have been working closely with BNSF to ensure safe construction practices around the railroad tracks.

Construction crews have been working closely with BNSF to ensure safe construction practices around the railroad tracks.

We’ve talked a lot about cranes, piers, and rebar at The 2020 Blog during the River ‘S’ Bridge replacement project. But there’s a bigger picture to bridge construction. Our project partners at the U.S. Department of Transportation offered this great explanation of, generally speaking, how bridges are designed:

“The most basic of bridge makeups include:

1. The superstructure, essentially the deck that we walk and drive on

2. The substructure, essentially the foundation of the bridge

As you can imagine, the substructure comes first. These are the components that connect the the deck (superstructure) with the water or ground. The specific type of foundation for the River 'S' Bridge is called 'drilled shafts'. Drilled shafts are comprised of rebar cages encased in concrete. On this project there are seven drilled shafts — one at each of three piers (the columns that hold the center span), and two at each of two abutments (the end points at each end of the bridge that connects to the road).”

Last week, the final pier drilled shaft was constructed. This week, the last of the abutment drilled shafts are scheduled to be constructed. The remaining substructure components include columns and pier caps.

A rebar cage for the ten-foot diameter piers.

A rebar cage for the ten-foot diameter piers.

This pier casing is installed prior to the rebar cage going in and has two jobs: 1) Keep concrete in, and 2) Keep soil out.

This pier casing is installed prior to the rebar cage going in and has two jobs: 1) Keep concrete in, and 2) Keep soil out.