Since my post last night there has been a lot more information released.
I have also been chatting about this with my former grad advisor, a Ph.D., P.E., with decades of experience in failure analysis.
It seems that the bridge had successfully undergone a stress test and cables being used to support the bridge were being tightened.
Our speculation is that the cables may have been tightened unevenly, causing the weight of the bridge to be born by only one or two cables. Excessive stress would have most like caused the anchor to pull out or detach from the cable.
Prefab concrete and Accelerated Bridge Construction (ABC) ate standard practices now. The bridge was intended to be cable stayed and the support column had not been installed yet.
Failure of a temporary support cable seems like the likely cause of this collapse.
I take back my comments from previous post as new information became available.
In light of this your other story, with the wonderful headline typo (A Bride Too Far) seems like the probable explanation. It they tightened the cables incorrectly, it’s not crappy design, it’s crappy labor. Illegal immigrants? Low cost, unqualified labor? This argues for that explanation.
I’ve seen accelerated construction used in Holland decades ago, but that was different. The example I remember was a highway bridge over a large river (Rhine?), steel lattice truss construction. It was built at essentially a shipyard, fully finished and structurally complete, shipped by barge to the site, lifted in place, done.
It never occurred to me someone would install a structurally UNsound object and then only afterward make it sound. That’s not engineering, that’s gambling.
A friend told me that this same company also did the elevated sections of the Selmon Expressway in the Tampa area, of which a large section also collapsed (no fatalities, thank God). Coincidence?
In spite of my earlier comment that this event and the shooting last month have nothing in common and the media shouldn’t try to connect them, I’m starting to wonder. The information is still pretty early, but here are some tidbits.
1. Fox news headline saying that the contractor had been cited in the past for gross negligence. Apparently that didn’t stop them being used here. Feels like the FBI treatment of its tip line.
2. Student was quoted along the lines of “they built that bridge in 2 days? OMG, that’s scary”. No, actually, they didn’t *build* it in 2 days, they built it in something like the usual time and *installed* it in 2 days. Feels a bit like “OMB, an AR15 bullet travels at 3x the speed of a handgun bullet”.
3. Lot of publicity about the “new Accelerated Construction method”. I have not yet seen anyone propose to ban “accelerated construction”, but I suspect that will be proposed. Just like the proposed ban on “assault weapons”.