US-52 Bridge over Big Blue River near Morristown, IN and Corten Steel

(Satellite)

Corten is a brand name for US Steel. The generic term seems to be weathering steel.

Indiana Department of Transportation: East Central posted, cropped
📍 Shelby County 
The U.S. 52 bridge over the Big Blue River will have pre-rusted beams! You read that correctly! This is a process called weathering steel in which the weathered steel provides a protective rust that further inhibits corrosion.
Jim Williams: It's Corten steel. Not CorTen or Cor-Ten.
[The comments identify some buildings and other bridges that were built with Corten.
It is not used for automobiles because it does not bend well enough for thin sheets of steel to be stamped into shape.]
Hunter Stout: Done a few jobs with CorTen, it’s some neat stuff. Doesn’t work any different than mild steel, but watching it rust over the course of a day is fascinating.
Chris Arndt: The John Deere Admin building in Moline, IL designed by Eero Saarinen and built in the early 60s, was about the first major building constructed with Cor-Ten. After maybe 2 decades, it was learned that Cor-Ten was not suitable for setting in concrete footings bare and ultimately corroded.

John Shaffer commented on the above post
This was done with a bridge in Owego NY, still looks great even after 20 years.

Because a Pittsburgh bridge made with Corten collapsed on Jan 28, 2022, I followed up on that collapse. 

Note the articulated Port Authority bus that went down with the bridge.

Richard Butterworth commented on a post (whose link is now broke) via Dennis DeBruler

Getting that bus out of the ravine was non-trivial in its own right.

cbsnews_crane

The crane has a lot of counterweights for this lift.

cbsnews_1_year_later

cbsnews_1_year_later, NewsChopper 2/KDKA
PennDOT built the new bridge with concrete girders instead of steel girders. One lane in each direction was open by Christmas, 2022.

But they closed it for another month in June 2023 to finish construction and open all four lanes. [PittsburghMagazine]

After four months, the NTSB has a couple of photos from the forward-facing and curbside cameras of the bus. And they plan to a lot of testing, interviews and inspection of similar bridges.

ntsb_May_2022
This shows the bridge deck separating at the east expansion joint.

ntsb_May_2022
This shows that the west end had already fallen off the west abutment.

Two days short of  a year later, the NTSB has done a lot of testing, interviews and inspection of ten bridges. [ntsb_Jan_2023]