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The Ordinary Engineering Behind the Horrifying Florida Bridge Collapse (wired.com)
An anonymous reader quotes a report from WIRED: The people of Sweetwater, Florida were supposed to wait until early 2019 for the Florida International University-Sweetwater University City Bridge to open. Instead, they will wait about that long for an official assessment from the National Transportation Safety Board of why it collapsed just five days after its installation, killing at least six people. In the immediate aftermath of the disaster, many queries have centered on the unconventional technique used to build the bridge, something called Accelerated Bridge Construction, or ABC. But ABC is more complicated than its acronym suggests -- and it's hardly brand new. ABC refers to dozens of construction methods, but at its core, it's about drastically reducing on-site construction time. Mostly, that relies on pre-fabricating things like concrete decks, abutments, walls, barriers, and concrete topped steel girders, and hauling them to the work site. There, cranes or specialized vehicles known as Self-Propelled Modular Transporter install them. A video posted online by Florida International University, which helped fund the bridge connects to its campus, showed an SPMT lifting and then lowering the span into place.
In a now-deleted press release, the university called the "largest pedestrian bridge moved via SPMT in U.S. history," but that doesn't seem to mean much, engineering-wise. SPMTs have been around since the 1970s, and have moved much heavier loads. In 2017, workers used a 600-axle SPMT to salvage the 17,000 ton ferry that sank off the coast of South Korea in 2014. The ABC technique is much more expensive than building things in place, but cities and places like FIU like it for a specific reason: Because most of the work happens far away, traffic goes mostly unperturbed. When years- or months-long construction projects can have serious effects on businesses and homes, governments might make up the money in the long run. Workers installed this collapsed span in just a few hours. These accelerated techniques are also much safer for workers, who do most their work well away from active roads. The report goes on to note that the bridge collapse is still under investigation and the search for a culprit is ongoing. "The answers could run the gamut, from design flaws to fabrication flubs to installation issues," reports WIRED. As of publication, The Washington Post is reporting that an engineer called the state to report cracking two days before its collapse.
In a now-deleted press release, the university called the "largest pedestrian bridge moved via SPMT in U.S. history," but that doesn't seem to mean much, engineering-wise. SPMTs have been around since the 1970s, and have moved much heavier loads. In 2017, workers used a 600-axle SPMT to salvage the 17,000 ton ferry that sank off the coast of South Korea in 2014. The ABC technique is much more expensive than building things in place, but cities and places like FIU like it for a specific reason: Because most of the work happens far away, traffic goes mostly unperturbed. When years- or months-long construction projects can have serious effects on businesses and homes, governments might make up the money in the long run. Workers installed this collapsed span in just a few hours. These accelerated techniques are also much safer for workers, who do most their work well away from active roads. The report goes on to note that the bridge collapse is still under investigation and the search for a culprit is ongoing. "The answers could run the gamut, from design flaws to fabrication flubs to installation issues," reports WIRED. As of publication, The Washington Post is reporting that an engineer called the state to report cracking two days before its collapse.
The engineering drawings I have seen show a tall tower with suspension supports coming down to support the span. Was the tower complete and the suspension in place when it broke or was that for completion later? Also the suspension when to both sides of the tower so it was balanced. Are there any pictures of the bridge while it was "good" to compare with the engineering drawing?
See here for a 3d view of the design. As far as I could tell the tower, the section over the water and the suspension lines were not in place when it collapsed.
https://youtu.be/Q2A1wS09p0k?t=5
The question I havenâ(TM)t seen asked, much less answered, is this: the final bridge was supposed to be supported by cables from a central pier. Why was safe to install the sections without that support?
In my town we have a footbridge that was installed this way, several years ago. It was factory-built in Phoenix, hauled 100 miles up I-17 using one of the smaller roadable version of the SPMT, and installed overnight to cross a creek. There hasn't been a problem since.
Offsite construction should be safer than site-built, so in this disaster let's focus on the design itself, rather than rushing to judgement on the offsite construction.
It's much more likely the fault of a diversity hire.
Sure, xe couldn't pass algebra, but xis skin color raised our minority numbers. It was well worth it, being this woke.
Like every engineering disaster
That isn't even remotely true. The vast majority of engineering disasters happen without identification and without warning. An even larger number of infrastructure disasters have nothing to do with engineering as well.
somebody found the problem, and failed to communicate its severity
Nope. Somebody found *a* problem and didn't know of the severity. Cracks don't mean much at all. It may or may not have had anything to do with the collapse.
There's no substitute for risk assessments by fully qualified engineers, of course
You're right. But you fail to realise that this takes time.
Obviously it wasn't strong enough to span the distance without them
That isn't obvious at all. That's why we do incident investigations. Just because it's final design was to have cables doesn't mean that during construction this wasn't taken into account. There is a lot of reasons why this incident could have happened.
Now imagine what would happen if enough people say "Fuck this, I am not voting for any shitty candidate."
One of the two losers still wins. There is no quorum requirement in American elections.
I assume that's what they were up to, but of course a bridge by its nature is more extreme in one direction. It may have had nothing to do with the collapse, it may have caused the collapse.
People in these situations want fast answers, so they jump to conclusions based on reports of cracks, or cables being tightened. But good answers take time, and it's a fair bet by the time we get good answers the public's curiosity will have waned. Even if the things drawing our attention now are involved, they're embedded in a much more complex scenario than most people have the patience for.
Post may contain irony: discontinue use if experiencing mood swings, nausea or elevated blood pressure.
Sure looks like one to me http://www.mcm-us.com/projects... you cunt.
Only the State obtains its revenue by coercion. - Murray Rothbard
or build the bridge. Instead, only woman or minority owned business were picked from. The president of FIU even bragged about that during the ground breaking ceremony. I bet he already regrets saying that.
It's not even about political beliefs anymore. It's about emotions, and more specifically virtue signaling. And it's not only with Americans, it's with most people living in Western societies, particularly white people. "Hello, I live in the West, I'm white, let me virtue signal."