Another update. Tl;dr: NTSC says that the bridge designers done fucked up.
Updated:
OSHA says warning signs were ignored. FIGG Bridge Engineers disagree with the OSHA report.
Yeah, they did everything absolutely correct :dubious:
Res ipsa loquitur.
I’m just a senior undergrad engineering student, not an engineer. And mechanical, not Civil, although i did quite well in statics. But from the very first time I saw that bridge, it just rubbed me the wrong way. It doesn’t even LOOK right, engineering wise. And why would you go through the trouble of cosmetically making it look like a cable stayed bridge? Just make it a cable stayed bridge!! It would have been much more structurally sound and you would have had a much easier time with the funky truss angles.
Reminds me of this:
Just trying to lock it in place — and then it killed 35.
I don’t even have those credentials and it didn’t look right to me, either. Until I read the original article in the OP, looking at the pictures I figured they were just some kind of esthetic embellishment, not a load bearing part of the bridge.
Engineering News Record has an article with a few more details, and a link to the full report.
I never realized until this morning that the finished bridge was going to have a tall tower with fake cable stays (see schematic here). This was the first time that all those oddball angles of the diagonal truss elements made sense. The Wikipedia does confirm that it was going to be a “faux” cable-stay tower, so apparently all of the structural strength was in the existing truss. The non-repeating angles of the truss elements do make it look “not right” in the absence of the bogus cable stays, but it seems like it should have held up, provided the elements of the truss had adequate tensile/compressive strength as needed (they did not).
Maybe I’m tone-deaf but the only thing that seemed off to me is the fact that the top of the bridge was so much narrower than the bottom. The cables didn’t look any weirder or uglier than other cables around the area, fake or real, and if there had been no cables and the concrete were a little rawer it would have looked like a perfectly respectable modernist structure.
The latest findings. (tl;dr: just about everyone involve done fucked up.)
The NTSB is completing its report:
https://ntsb.gov/news/press-releases/Pages/NR20191022.aspx
Here is an abstract of the report:
The final report will be published in a few weeks.
This is a short and useful video.
It points out that cracks developed in the highest-stress point of the bridge (the base of member #11) before the bridge was moved onto its piers, and how they steadily widened and spread over the 5 days before the collapse.
The pictures of the extensive cracks taken shortly before the failure make you wonder how anyone could believe this was anything other than an imminent disaster. It was a “single point of failure” bridge design - those cracks (in an area that ought to have been pristine) were far past the “time to run screaming down to the road and close it immediately” stage.