Armed Polite Society
Main Forums => The Roundtable => Topic started by: RoadKingLarry on March 15, 2018, 03:51:02 PM
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New Pedestrian bridge in Sweetwater Florida collapses on to road, multiple vehicle crushed.
http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article205316174.html (http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article205316174.html)
News reports said it was designed to withstand a Cat 5 hurricane and stand for 100 years.
Apparently it wasn't built to design specs.
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Wow. Collapsed onto a road where traffic was held up at a stop light. Looks bad.
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One article I read says it was assembled overnight and today was the first day in service.
edit: Not one day old, but first built on Saturday.
I wonder if there was a bunch of weight on the bridge while it was being finished and before is was ready for the weight.
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Not even in service yet. The large span was dropped in place very recently, but the approach steps/ramps weren't finished.
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It is very early, but a voice in the back of my head keeps asking if the corruption around the local Sheriff's office and the school district is more widespread.
I wasn't sure if people were still alive trapped under the rubble or not...so I hate to get into that now.
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New Pedestrian bridge in Sweetwater Florida collapses on to road, multiple vehicle crushed.
http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article205316174.html (http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article205316174.html)
Designed as a cable-supported bridge, the $14.2 million bridge project was a collaboration between MCM Construction, a prominent Miami-based contractor, and Figg Bridge Design, based in Tallahassee.[/quote]
Doesn't look like a cable supported bridge to me. It's a truss. I don't think there's any way a cable-supported bridge can be built off-site and then hoisted into position all in one.
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https://twitchy.com/gregp-3534/2018/03/15/mass-casualties-reported-after-brand-new-pedestrian-bridge-at-fiu-in-miami-collapses-photos-video/
This Twitchy thread has a video about half way down showing some footage of the span being put in place.
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One eye witness was being interviewed by Shep Smith on Fox and claimed that a large crane was holding a "piece of equipment" used to tension a cable; the crane's hook or cable broke, dropping the "piece of equipment" on the bridge and causing the collapse. We'll see what happens.
Bet the lawyers are furiously working to figure out who to sue - from the construction company to the programmers that made the FEA software the architect presumably used, and everyone in between.
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Apparently live coverage from the air at a good angle.
https://youtu.be/93BQG71Mr68
Audio is kind of crazy, with repetitive beeps sometimes.
They've got at least two large cranes out there working it over.
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Ancillary FYI "10 Worst" bridge collapses.
https://youtu.be/-IUkZmswYuc
Gravity wins again.
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Doesn't look like a cable supported bridge to me.
Maybe that's what they forgot.
I don't think there's any way a cable-supported bridge can be built off-site and then hoisted into position all in one.
I can think of a couple ways. Not practical ways, mind you, but that wouldn't stop government from insisting that contractors try them.
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I can think of a couple ways.
But where would they find that much used dental floss and chewing gum on such short notice?
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But where would they find that much used dental floss and chewing gum on such short notice?
More of a question of how to transport ballasts big enough, since cable-supported bridges normally use giant deadman anchors for the cables. If you're making a portable one, you need hundreds of tons of ballast to replace a couple tons of whatever buried in hundreds of tons of the ground off the ends.
Cable-stayed could be done, but they tend to be rather tall for a given span compared to a simple truss, so logistics of transport come into play.
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Designed as a cable-supported bridge, the $14.2 million bridge project was a collaboration between MCM Construction, a prominent Miami-based contractor, and Figg Bridge Design, based in Tallahassee.
Doesn't look like a cable supported bridge to me. It's a truss. I don't think there's any way a cable-supported bridge can be built off-site and then hoisted into position all in one.
The article says that the span was built next to the road, then they used a "mechanical transporter" to move it into place in one day, in order to minimize disruption. Looking at the pictures, it's a device like what they used to move the space shuttle into position, or transport nuclear power station cores to their site - basically all wheel drive tractors with massive numbers of wheels/axles, with hydraulic lifts that allow the devices to keep what they're carrying level despite minor grades. Also, to account for varying shapes for the object across multiple transports.
Well, it's certainly not minimized now.
As for truss vs suspension:
You don't have to have the cables above the bridge:
https://en.wikipedia.org/wiki/Millennium_Bridge,_London
Third video shows the theoretical completed bridge. It's only seen a couple times, but it's definitely suspension. Or perhaps, given the structure between the bridge bottom and the roof, a hybrid.
https://www.cnn.com/2018/03/15/us/fiu-pedestrian-bridge-stats-trnd/index.html
(https://s19.postimg.org/9kxyk1bo3/DX77gar_VAAAUBdw.jpg)
The bridge was supposed to be strong enough to survive without the suspension parts outside of hurricane conditions...
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Third video shows the theoretical completed bridge. It's only seen a couple times, but it's definitely suspension. Or perhaps, given the structure between the bridge bottom and the top, a hybrid.
https://www.cnn.com/2018/03/15/us/fiu-pedestrian-bridge-stats-trnd/index.html
(https://pbs.twimg.com/media/DX77garVAAAUBdw.jpg)
No cable stays in place when it fell. The bridge shown in the time lapse is only half the total length -- there was going to be a second span to crosss a river next to the highway. I don't think the pylon and cables were in place yet.
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Where did you see cables or suspension? I didn't see anything like that.
See the giant picture of the bridge I posted? The big central tower with the poles?
btw, if you replace the img with https://s19.postimg.org/9kxyk1bo3/DX77gar_VAAAUBdw.jpg it'll shrink a bunch, it's a tad large of a picture right now. Source I grabbed it from had resized it, sadly APS doesn't let me do that with images here. It's native or nothing.
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The team that designed and built this thing has prior experience with their bridges collapsing:
http://www.dailymail.co.uk/news/article-5507475/Two-construction-cos-Miamis-instant-bridge-collapses-violations.html
Good photo from the article showing the segment that collapsed. It is only half the total length, and doesn't have any cables attached. Those have to be tensioned symmetrically, so that part of the operation would have happened after the other span was erected.
(https://armedpolitesociety.com/proxy.php?request=http%3A%2F%2Fi.dailymail.co.uk%2Fi%2Fnewpix%2F2018%2F03%2F15%2F23%2F4A3B171A00000578-5507475-image-a-6_1521155254831.jpg&hash=fe78bcc8821893953762c5c1d3a4ca9160ac6c15)
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And holy *expletive deleted*it the anti-Trumpers are coming out of the frigging woodwork to blame the collapse on him...
I've seen some stuff from the left over this that's just... unfreakingbelievable.
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And holy *expletive deleted*it the anti-Trumpers are coming out of the frigging woodwork to blame the collapse on him...
I've seen some stuff from the left over this that's just... unfreakingbelievable.
And they accused the Obama "birthers" of being delusional!
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http://www.mammoet.com/
A neighboring site just built a large chemical plant and they were using those multi-wheeled crawlers to move heavy equipment in. Mammoet was the company doing all the rigging and heavy moving. They actually built up a barge dock a couple miles away on the Intercoastal and rolled the heavy equipment in from there at night. They put in a temporary heavy bridge across a canal as well.
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And holy *expletive deleted*it the anti-Trumpers are coming out of the frigging woodwork to blame the collapse on him...
I've seen some stuff from the left over this that's just... unfreakingbelievable.
I wonder if anyone has suggested the bridge was shot with an AR15 yet?
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I wonder if anyone has suggested the bridge was shot with an AR15 yet?
Oh, that's absurd. It would have exploded.
Remember how we blamed Obama for all this stuff? Neither do I.
https://en.wikipedia.org/wiki/Indiana_State_Fair_stage_collapse
https://en.wikipedia.org/wiki/2013_Philadelphia_building_collapse
https://en.wikipedia.org/wiki/I-5_Skagit_River_Bridge_collapse
http://www.latimes.com/local/lanow/la-me-ln-bridge-collapse-freeway-20140518-story.html
https://www.cnn.com/2014/03/13/us/manhattan-building-explosion/index.html
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Only people over 21 should be allowed to use bridges.
But seriously which politician got kickback from hiring this company ?
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Only people over 21 should be allowed to use bridges.
But seriously which politician got kickback from hiring this company ?
University President
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Only people over 21 should be allowed to use bridges.
But seriously which politician got kickback from hiring this company ?
It's Miami-Dade. All of them.
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Closed circuit tv of the actual collapse at 0:30
https://youtu.be/F0MBOQV7kuU
Don't know if it's been posted before.
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Thank you, Captain Obvious:
http://www.newser.com/story/256681/florida-bridge-collapse-may-lead-to-criminal-charges.html
One thing investigators are looking at is if it was a good idea to install the 174-foot bridge before the central tower.
Offhand, I think we can now conclude that it probably was not a good idea.
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Closed circuit tv of the actual collapse at 0:30
https://youtu.be/F0MBOQV7kuU
Don't know if it's been posted before.
Just curious how y'all see it. It almost looked like it cracked in 2 or 3 spots then it started folding up fell.
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Do we like smoking guns? Of course we like smoking guns.
https://www.abcactionnews.com/news/state/fdot-warned-about-fiu-bridge-cracking-2-days-before-fatal-collapse-but-didnt-hear-voicemail
Lead project engineer for Figg (the designers of the bridge) called a Department of Transportation employee two days BEFORE the collapse to report unanticipated cracking in the bridge -- near the north end (which is the end toward the center pylon, and thet's where the collapse started).
"Hey Tom, this is Denney Pate with FIGG bridge engineers. Calling to, uh, share with you some information about the FIU pedestrian bridge and some cracking that's been observed on the north end of the span, the pylon end of that span we moved this weekend. Um, so, uh, we've taken a look at it and, uh, obviously some repairs or whatever will have to be done but from a safety perspective we don't see that there's any issue there so we're not concerned about it from that perspective although obviously the cracking is not good and something's going to have to be, ya know, done to repair that. At any rate, I wanted to chat with you about that because I suspect at some point that's gonna get to your desk. So, uh, at any rate, call me back when you can. Thank you. Bye."
I think Figg is fubar on this one.
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Just curious how y'all see it. It almost looked like it cracked in 2 or 3 spots then it started folding up fell.
I couldn’t tell. There is another video out from someone’s dashcam in their car that is better quality.
Found it: https://m.youtube.com/watch?v=Ucflj-MsJBI
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I only see one spot where the bridge breaks, which is right next to the crane. Maybe the crane boom hit the bridge.
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I'm sure that Mr. Pate will be the scapegoat for all of this.
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The bridge deck broke at the intersection of two of the diagonal truss members. This is called a truss "panel point," and it's where stress concentrates in a truss. The roof broke at the upper panel point.
Video report on the phone call: https://www.youtube.com/watch?v=FNrAMYxp8CE
Being an olde pharte who has lived through several infamous collapses and read the reports on the causes, I'm baffled at the hubris that led them to open the road to traffic under a bridge that didn't have the structural cable system in place.
In April of 1987, a 16-story building was under construction in Bridgeport, Connecticut. The structural system was called "lift slab." In this system, the concrete floor slabs are all poured on the ground, one on top of another like a stack of pancakes. Once they're cured, they are hoisted up and clipped in place to the vertical columns. At L'Ambiance Plaza, something went wrong and one of the slabs came crashing down, taking down the entire structure and killing a number of workers who were under it. In the aftermath, Connecticut enacted a moratorium on lift slab construction (which may still be in effect), and the industry adopted rules that only essential workers are allowed under the slabs while they are being hoisted and secured.
This bridge is kind of the same idea. Instead of "lift slab," it's a "lift bridge." The idea of building bridges off to the side and then dropping them into place is not new, but in this case the bridge they dropped into place was NOT the complete structure. The completed structure would have included the central pylon (which hadn't even been built yet), the other span (across the canal), and the cables connecting and supporting the two spans. Obviously, someone thought the truss was structurally sufficient without the cables. That calculation was obviously incorrect. (Either that, or there was a massive flaw in the construction. That's possible, but probably unlikely.)
I just can't believe they opened the road to traffic with the structure not fully in place.
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Here's an interesting video discussing what can be gleaned from pictures and video.
https://youtu.be/KtiTm2dKLgU
AVE is a smart guy, and lots of engineers have been kicking this around on the internet. I think their theory is compelling. i.e. the crew was messing around with the post tensioning rods and they failed.
I read a report that they were doing a stress test, and had cranked up the tension on the rods for the test.
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The explanation in the AVE video makes a lot of sense.
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Somewhere, I read that in Roman times, engineers were required to stand under a new bridge as supports were removed... hmmm...
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Somewhere, I read that in Roman times, engineers were required to stand under a new bridge as supports were removed... hmmm...
It collapsed a week later. Unless the engineers were going to live there, that wouldn't work well. =D
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Surprised no one has posted video of this yet. The Tacoma Narrows Bridge collapse.
https://www.youtube.com/watch?v=CsKKDLKYsVU
This is a true failure of design and engineering.
No human deaths, apparently a dog was left in one of the cars and died when the driver abandoned it to run back to safety (why the ahole didn't drive is beyond me).
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No human deaths, apparently a dog was left in one of the cars and died when the driver abandoned it to run back to safety (why the *expletive deleted*hole didn't drive is beyond me).
My first guess is that he believed he'd be safer on foot, instead of in a much heavier car. In the film, though, he seems to be walking off slowly and calmly. Maybe he just didn't care about the dog. =(
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Somewhere, I read that in Roman times, engineers were required to stand under a new bridge as supports were removed... hmmm...
"AAACK! It was supposed to be III.I,IV,I,V,IX, you idiot, not III.I,VI,I,V,IX !"
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My first guess is that he believed he'd be safer on foot, instead of in a much heavier car. In the film, though, he seems to be walking off slowly and calmly. Maybe he just didn't care about the dog. =(
I don't think the guy in the film was the driver of the car. I think that was an engineering professor who showed up to investigate the bridge's behavior. I think his name was Farquharson, or something like that.
First-hand accounts: http://www.wsdot.wa.gov/TNBhistory/People/eyewitness.htm
The narrator says the Bronx-Whitestone bridge in New York is a twin, but it isn't. Galloping Gertie was two lanes wide -- the Whitestone is six lanes. (Four lanes plus pedestrian walkways when it was opened, converted to six vehicular lanes since.)
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"AAACK! It was supposed to be III.I,IV,I,V,IX, you idiot, not III.I,VI,I,V,IX !"
Took me a second, but that's pretty good! :rofl:
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Took me a second, but that's pretty good! :rofl:
I thought they were just random numbers, but I see what you mean.
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I was about to bring up a trip by bus my mother and I took to the Bronx to visit my sister when I was, I dunno, seven or eight yo during a windstorm. I'm pretty sure it was the Whitestone Bridge or one of the Triborough bridges. Thanks for the reminder. That bridge was whipping all over and the driver was really struggling to keep the bus on course.
Really scared the crap out of me and my Mom and the other passengers. I don't remember if it was a near hurricane or what, but the first time I ever saw that Tacoma Bridge video, it was just like that, with the pavement bending like rubber but maybe not as bad. So I'm not surprised that the guy left the car. I wondered about that dog, too.
Terry
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Surprised no one has posted video of this yet. The Tacoma Narrows Bridge collapse.
https://www.youtube.com/watch?v=CsKKDLKYsVU
This is a true failure of design and engineering.
No human deaths, apparently a dog was left in one of the cars and died when the driver abandoned it to run back to safety (why the *expletive deleted*hole didn't drive is beyond me).
I think I remember reading somewhere that he had tried to go back for the dog but couldn't.
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I did some more reading on it, and yes, he and another person did try to go back to the car to get the dog. Apparently it was so terrified that it bit him or the other guy when they tried to get it out of the car.
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Why didn't they use something like this? (http://gatorbridge.com/applications/pedestrian/)
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Why didn't they use something like this? (http://gatorbridge.com/applications/pedestrian/)
Yeah no kidding! Would have been a lot simpler, and cheaper!
I guess it wouldn't glorify an administrator's ego to build something small like that.
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Dave Barry spells it all out from way back in 1999. (http://www.unz.com/isteve/dave-barry-on-the-south-florida-infrastructure-industry/)
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Why didn't they use something like this? (http://gatorbridge.com/applications/pedestrian/)
I suspect you'd find an aluminum truss couldn't span the distance they needed and also hold the weight of anticipated pedestrian traffic. Obviously this particular concrete truss couldn't either, but in general a stressed concrete (either pre- or post-) is a good, low maintenance, strong, relatively cheap answer to bridging things.
The GatorBridge website you linked shows a bridge in Oakland that has several support piers and spans 120'. It is described as "one of the larger structures fabricated by [....] Gator [bridge]". That prefab aluminum stuff is a completely different scale.
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Just watched video of crews pulling out what was left of a full size Chevy pickup. Compacted to a mere fraction of its original height. Poor bastards inside never stood a chance. If there is any kind of positive to be gleaned, at least they didn't suffer.
Brad
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A rant on the diversity angle. (http://takimag.com/article/diversity_bridge_is_falling_down_my_fair_lady_david_cole)
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A rant on the diversity angle. (http://takimag.com/article/diversity_bridge_is_falling_down_my_fair_lady_david_cole)
Ah, yes -- DIVERSITY!
A decade ago I was working as an assistant building official in a small town that had seen its building inspection department suddenly grow from one person to four because of the workload created by a huge golf course condominium project being built in town by an out-of-state developer. I don't speak fluent Spanish, but my late wife was from Sudamerica so I was trying to learn, so I could converse with her family when we went there for visits. The boss kept complaining about the workers placing the reinforcing steel for the foundations, because they kept getting it wrong and they didn't speak English, so he couldn't get them to do it right.
So one morning, on the day before a foundation pour, the boss dragged me away from the plans I was reviewing and we went out to the site. Sure enough, the rebar was being set to close to the forms, so there wouldn't have been enough concrete to protect the rebar from water in the ground. And, just as the boss had said, when he tried to get it fixed, they just looked at him and gave him the "No hablo ingles" routine.
So the boss looked at me, and I looked at the workers, and I just said "Escuchame, muchachos, necesitan mas espacio entre el acero y la madura."
Oh, my! They just looked at each other ... and the look was clearly, "Oh, *expletive deleted*it -- he speaks Spanish. We're fooked."
The spacing got fixed, and the boss never had another problem. But "diversity" is a problem, because the "diverse" elements don't think like Americans. There used to be a saying that there were three ways to do anything: "the right way, the wrong way, and the Army way." Today that has become: "The right way, the wrong way, and the way we do it back home where we came from and you Anglos probably shouldn't ever set foot." Anyone who presumes to tell them that we do it this way in the United States is racist.
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<----------------------- !
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(https://i.imgur.com/omCDhiB.jpg)
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I think I saw him on the local news talking about road conditions yesterday.
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Why the Miami bridge collapsed: https://www.youtube.com/watch?v=JvmvFQKTrMY
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Why the Miami bridge collapsed: https://www.youtube.com/watch?v=JvmvFQKTrMY
There are some rather fundamental errors in his explanation of how post-tensioned concrete works, and he's VERY wrong about where and how long it has been used, but his theory of a strand having been over-stressed by the incorrect placement of one of the lifting carriages makes sense.
I went to graduate school in Pennsylvania and early in my career I worked in Connecticut and New England. There were plenty of post-tensioned concrete structures around both areas, even in the early 1970s. I suppose that's "recent" compared to the first uses of concrete in the time of the Roman Empire, but in any conversational context I don't think 40+ years is exactly what most people think of as "recent."
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I had a little trouble following how that one compression bar got loose.
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I had a little trouble following how that one compression bar got loose.
Tension strand, not compression bar. I think his thesis is that it was stressed beyond its yield point so it physically stretched. Then, when they attempted to tighten it, they stretched it farther ... until it failed.
The catch is that in a truss, half those diagonal web members are in compression and half are in tension. It's not intuitive which are which. 45 years ago I knew how to analyze a truss graphically and figure that out -- but I haven't done it since my thesis, and today I don't have even a fuzzy recollection of how to begin. He may be correct, but his explanation is terrible.
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Thanks for nomenclature correction. "Compression bar," to me, because that's what puts the "diagonal web members" (and presumably, the long horizontal members) in compression.
Glad to hear that it ain't an easy analysis. I feel less dumb now.
TNX, Terry
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The catch is that in a truss, half those diagonal web members are in compression and half are in tension. It's not intuitive which are which. 45 years ago I knew how to analyze a truss graphically and figure that out -- but I haven't done it since my thesis, and today I don't have even a fuzzy recollection of how to begin. He may be correct, but his explanation is terrible.
Used to be a couple of freeware apps for simple (simple being a relative term when you're talking about FEA) modeling, and I think a web-based tool too. I'll dig a bit if I remember when I get back from the laundromat.
But yeah, once steel stretches noticeably, pulling on it harder isn't going to fix the problem for long.
EDIT: https://trusstool.com/
And an online 2D modeler: http://engsci.stevenhe.com/trusssolver