Saturday, January 29, 2022

A Bridge Collapsed in Pittsburgh, PA at 6:30am, Jan 28, 2022

(Bridge Hunter; Satellite)

There were no fatalities even though there were cars and an articulated bus on the bridge when it fell.

Street View

Brian Shields posted four photos with the comment: "BREAKING NEWS: Bridge collapse in Pittsburgh. Injuries reported. Info just coming out… (Forbes Ave. Bridge)"
[This post has 13K comments. I didn't read them.]
Vince Diventura shared
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[Note the posted load limit of 26 tons.]

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But this comment did catch my eye.
Dawn Renee commented on Brian's post
Yeah, they knew that bridge was damaged for years. So scary.
[So the bridge inspectors and repair engineers didn't think that diagonal member was carrying any compression forces? Cables help only with tension forces.]

Richard Butterworth commented on Brian's post
The average fully loaded articulated bus weighs between 28 to 32.5 tons. With a bridge weight limit of 26 tons, the bus probably shouldn't have been there in the first place.
[I wonder what the fine print for "load limit" is. That is, 26 tons in how many feet? An articulated bus may be long enough that it legally spreads its weight out over the bridge.]

"Design: Batter-Post steel rigid frame, constructed from weathering steel (also known as Cor-Ten steel)" [BridgeHunter] Some BridgeHunter comments indicate that Cor-Ten has proven to have a problem with salted roads.

The Chicago Tribune reported that the most severe condition of those hospitalized was "fair." I'm not going to bother to read any more of the media reports since I know there were no fatalities. I'm sure they will report the accident is under investigation. I will record the NTSB URL that Nathan Holth provided in BridgeHunter, https://www.ntsb.gov/investigations/Pages/HWY22MH003.aspx, so that eventually I can access some real information.

I capture the rating of the bridge so that I can compare it to the I-80 bridges in Joliet, IL.
BridgeHunter

I-80's report:
BridgeHunter-I-80

If this collapsed bridge was "just" poor, then why are vehicles still allowed to drive over a bridge that is Critical? Especially since normally there is a continuous line of trucks over the whole bridge because of the intermodal yards south of Joliet and the congested traffic on the bridge. Secondly of all, how can the individual numbers for I-80 be worse than the Fern Hollow Bridge but the Sufficiency Rating is more than three times better? If the trillion dollars is allocated based on Sufficiency Rating, then I-80 is screwed. (I had seen a Sufficiency Rating of 6, which is "intolerable." Who changed the 6 to 60?)

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