I just saw a video of the bridge collapsing. Horrific. I can’t believe they were allowed to do testing on it without first shutting down the road below
I thought I read an article saying the bridge wasn’t scheduled to open to pedestrians until 2019, so it was still a ways from being finished. That article I read also said the final connections to the primary supports hadn’t been made yet, and the bridge was using temporary supports, all of which meant it was in a fragile stage of construction.
So sad and hopefully others will learn lessons to prevent similar tragedies, which should NEVER have happened!
This quote, by a catastrophic risk expert, jumped out at me: “Innovations always bring potential ‘failure modes’ that have not been previously experienced,” he said.
It sounds like one of those was “failure of imagination” – to not not see the potential disaster of testing while the traffic was underneath (or other new, questionable ‘innovations’ that where used.)
Read more here: http://www.miamiherald.com/news/local/community/miami-dade/article205422719.html#storylink=cpy
^“failure of imagination” - which is also called incompetence. Unacceptable.
^Exactly.
Apparently they were tightening cables at the time of collapse. Why wouldn’t they stop traffic while doing that???
Negligence of epic proportions.
Sickening.
I read somewhere there was a stop light where the bridge collapsed and cars were waiting for the light to change. This is unbelievable.
Looks like it could be a failure on three fronts. Construction (company has a rep for shoddy workmanship), design (you’d need to design for stability at every stage, not just final) and implementation (allowing testing during use).
Maybe the constructions guys will say they have sleep apnea and don’t remember anything. It seems to work for locomotive engineers.
In any case, if you look at the pictures and future rendering in this article
http://www.miamiherald.com/news/local/community/miami-dade/article205432029.html
you’ll see that there is supposed to be a support tower with large cables that are there to support the bridge. The article notes, as the pictures post-collapse confirm, that the support tower and cables had not yet been installed. And yet it appears that the bridge had been place across the span and was “self-supporting” for the first five days…until it wasn’t. It would seem that the cable adjustment that they refer to must be some internal tensioning cable assembly in the concrete and not the supporting cables shown in the drawing/rendering of the bridge, since they weren’t up yet.
I would have thought that the first order of business was to get the tower and cables installed, and then place the walkway and attach the cables. Anyone with any sense of mechanics and physics can see that a concrete span of that length is going to be under enormous stress from just its own weight, and probably wouldn’t be able to stand by itself without some steel frame skeleton. From the collapse photos it looks like the only steel involved was rebar in the concrete. It is a mystery to me why the tower and cables weren’t done first, and why the bridge itself was place on the piers without the supporting tower and cable.
Typically, the structural engineer’s job is to make sure the bridge is strong/stable enough once it is constructed. “Means and methods” of construction fall on the contractor’s shoulders. So the contractor hires an engineer to run stability/strength calculations for the bridge during construction.
I read that it’s a concrete truss, which is a perfectly acceptable structure - there’s a concrete truss bridge in Norridgewock, Maine that we drive over occasionally. But this walkway sounds like it was a more complicated structure. If I have any insights after learning more, I will share them. I’ll also see what my dad thinks - he’s a forensic engineer who studies problems and collapses (he investigated the collapse of the Dallas Cowboys’ practice facility a few years ago).
From that article, we get quotes with internal inconsistencies:
If this is a new technology, then the fact that “there’s never been any issue with it” seems besides the point, since apparently the time span of using it is very short. And now there is.
@MaineLonghorn Clearly it was not stable during construction. IDK but if it is an instant bridge in place on an operational highway, you’d think it would have to be designed for stability at every stage including with temporary supports.
What I am saying is that it is usually not the “design engineer’s” responsibility to design the bridge for stability during construction - that is the responsibility of the contractor’s engineer.
The pedestrian bridge my husband designed in Portland was also constructed off site and moved into place. My husband was NOT responsible for the stability of the bridge as it was being put in position - the contractor had to figure out the temporary supports.
Our liability insurance company would not be happy if we agreed to be responsible for a structure’s stability during its construction. We can’t be responsible for a contractor’s means and methods, because we’re not on site all the time.
While I understand that for normal bridges, the instant bridge seems like a different animal and the requirement for stability at all phases during use seems like it could affect the final design. This really seems like this “new technology” requires a team approach in which design and construction is working hand in hand at every stage.
I am always terrified when I have stop under bridges - seeing images of the infamous Oakland quake that happened almost 30 years ago made its imprint.
Well, the investigation will be illuminating, I’m sure!
I can’t believe it’s been so long since the Hyatt Regency walkways collapse. It’s been many years since I was in civil engineering undergrad, but that example was used to underscore our responsibility as budding engineers.
Hard to say if this will be design or construction related. I don’t want to hazard a guess- it’s sad regardless. But we learn a lot from failures like these, and they are harsh lessons for young engineers. How awful for the engineering students at FIU particularly.
^Horrific. Only up 5 days.
@BunsenBurner I won’t be stopping under bridges any time soon.