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Old 16th March 2018, 11:40 AM   #81
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Originally Posted by ahhell View Post
Semi-professsional opinion.
It was a suspension bridge supporting a truss, the load from the bridge was meant to be supported from the center tower via the suspension cables. It doesn't appear as though the cables were in place yet or they were slack.

The cables were not in place because the pylon which carried them was not built yet. This was a function of the design sequence of the construction plan.

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The load was likely supported entirely by the truss and the end points of the bridge. This condition was not accounted for in design.

Of course it was. This is made evident by the entire process used to erect merely that section.

Quote:
Either the truss failed because it was meant to be supported at multiple points midspan instead of just the ends or the embankment failed because it wasn't designed to support the bridge at all.

It seems clear to me that this particular sequence of construction was a planned and intended part of the design process. I don't see that it could have been anything otherwise. The process which was used just to get to the point where that bridge section was installed was lengthy and complex, spanning months. No structural engineer's office practicing even the most 'lick and a promise' diligence could possibly have not understood exactly what was planned. I expect that every step of the process received oversight from multiple directions long before they even began building the bridge section, much less putting it in place.

Quote:

I am a structural engineer, I rarely account for how parts of an incomplete structure are meant to be supported prior to completion. We design details for the completed structure, not for the intermediate stages. (Typically)

Maybe you don't, but in four decades of actually building PIP concrete buildings I can say with confidence that there have always been engineered drawings for exactly that purpose as part of the contract drawings we have used in the field. We have even worked with the engineers providing such drawing to determine alternative placement of shoring when we needed to make some areas more open for materials access, or the required placement of additional shoring for anticipated loads from materials storage during the building process.

Such interim support drawings are a standard component of the build process. Sometimes they might be commissioned by the contractor (or sub-contractor) doing the actual formwork, but they are always at least reviewed and approved by the project's engineer of record or their office.
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Old 16th March 2018, 11:58 AM   #82
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The couple of buildings I have been involved with with post-tensioned slabs it was just about reducing the depth of the slab/ amount of concrete. In a relatively small slab like the bridge, I'm curious why they (appear to) have opted for this over more orthodox reinforcement.
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Old 16th March 2018, 12:06 PM   #83
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Originally Posted by Steve View Post

I think you are very much on track here. On the highlighted link above there is a statement that says the slab is post-tensioned in two directions. I suspect that is going to turn out to be the weak link.

There's nothing intrinsically wrong with post-tension as a reinforcing technique. In fact it has many advantages over standard rebar reinforcement.

It does require some special care in areas of installation which have to be practiced by all the various trades involved, so that unanticipated problems due to a lack of awareness of the behavior of the material don't occur (usually suddenly). I could tell you scare stories for hours.

I can't say that something like that was the proximate cause of this particular failure. Post-tension reinforcing is a commonly used technique in the commercial (and even the residential) building industry in that part of the country, so most of the related trades involved are going to be aware of its peculiarities.
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Old 16th March 2018, 12:13 PM   #84
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Originally Posted by MikeG View Post
The couple of buildings I have been involved with with post-tensioned slabs it was just about reducing the depth of the slab/ amount of concrete. In a relatively small slab like the bridge, I'm curious why they (appear to) have opted for this over more orthodox reinforcement.


Post-tension has significant advantages over standard rebar reinforcing in many design applications. Slab depth is certainly one. Its ability to provide sufficient tension reinforcement across long unsupported spans is another, and is why it is widely used in long-span concrete structures.

There are many applications where the desired structure simply cannot be supported using only rebar. You can build structures which could not be built otherwise.
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Old 16th March 2018, 12:30 PM   #85
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Originally Posted by ahhell View Post
This is a strong possibility. My bet is on some change do design that occurred during construction. Mostly because most structural failures that occur during or shortly after construction are due to the unforeseen consequences of such changes.

Most such projects are overhyped. Its generally the builders responsibility to support structures during construction. Most construction contracts clearly state that as well. The design engineer should understand how the project can be built but the typical don't provide that plan to the builder.




It's pretty difficult for that to go unnoticed during construction. The truck arrives with a ticket that lists the concrete mix design and relevant specified properties. It under goes visual inspections prior to placement and their are regular samples taken for later testing.

Granted, you have to wait 28 days to test those samples.
They will likely have 7 day and 14 day breaks. As often as not the 7-day breaks will match or exceed design strength.
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Old 16th March 2018, 12:58 PM   #86
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Originally Posted by MikeG View Post
Not that would make any great difference to the structure. I say again, I reckon this is Rubio misunderstanding what he's been told on site, blurting out some nonsense to the media, who are now pursuing "cables" as their latest craze. It's a red herring.
Rubio can never get anything right.
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Old 16th March 2018, 01:08 PM   #87
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Originally Posted by quadraginta View Post
The cables were not in place because the pylon which carried them was not built yet. This was a function of the design sequence of the construction plan.




Of course it was. This is made evident by the entire process used to erect merely that section.




It seems clear to me that this particular sequence of construction was a planned and intended part of the design process. I don't see that it could have been anything otherwise. The process which was used just to get to the point where that bridge section was installed was lengthy and complex, spanning months. No structural engineer's office practicing even the most 'lick and a promise' diligence could possibly have not understood exactly what was planned. I expect that every step of the process received oversight from multiple directions long before they even began building the bridge section, much less putting it in place.




Maybe you don't, but in four decades of actually building PIP concrete buildings I can say with confidence that there have always been engineered drawings for exactly that purpose as part of the contract drawings we have used in the field. We have even worked with the engineers providing such drawing to determine alternative placement of shoring when we needed to make some areas more open for materials access, or the required placement of additional shoring for anticipated loads from materials storage during the building process.

Such interim support drawings are a standard component of the build process. Sometimes they might be commissioned by the contractor (or sub-contractor) doing the actual formwork, but they are always at least reviewed and approved by the project's engineer of record or their office.
Most often in my experience they are commissioned by the contractor or sub not produced by the design engineer. Our disagreement seems mostly a matter of perspective. Until recently, my industry rarely did design build. There were clear lines between the design team and construction team. Temporary shoring during construction was pretty much always the responsibility of the construction team. Sure, we reviewed them but we were clear that we didn't take responsibility for them. Means and methods.

Obviously something was went wrong, I am in no way saying I have the definitive answer, I'm just musing on possible causes.

I'm now leaning towards overstressing the concrete during tensioning. Which could be under-strength concrete, could be over tensioning, could be mislaid ducts(that seems less likely to me.) Could also be that it somehow something knocked it off or pulled it off the support. Early reports seemed claim a support failed but I don't see any pictures that support that claim. It could just be a massive design failure, that seems unlikely to me. As I mentioned earlier, the most common cause of early failure is changes during construction with unforeseen consequences. So, that's still in the running.

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Old 16th March 2018, 01:19 PM   #88
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Why might they have been fiddling with the (slab) cable tensions at all? Surely that is a one-off procedure, at a certain specified point after the casting of the slab? Would anyone expect it to be done (again?) after moving the structure into place?
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Old 16th March 2018, 01:32 PM   #89
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Originally Posted by MikeG View Post
Why might they have been fiddling with the (slab) cable tensions at all? Surely that is a one-off procedure, at a certain specified point after the casting of the slab? Would anyone expect it to be done (again?) after moving the structure into place?
I understand, from a college course, that they do occasionally have different tensioning schemes for intermediate and final positioning of precast post tensioned structures. Half remembered from my college days so take that for what it worth.
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Old 16th March 2018, 07:21 PM   #90
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Engineer on Florida bridge project called state two days before deadly collapse to report crack, state says

Originally Posted by The Washington Post
A lead engineer responsible for a pedestrian bridge that collapsed near Miami left a voicemail message for a state transportation official warning of “some cracking” two days before the structure crashed, state officials said Friday night.

The engineer with the private contractor FIGG Bridge Engineers did not consider it a safety issue, he said. The message was not retrieved until Friday because the Florida Department of Transportation official to whom the voicemail was directed was out of the office on assignment, the state agency said. The message about the bridge being built to connect Florida International University with the neighboring city of Sweetwater was left on a land line.

“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,” the engineer said, according to a transcript of the call released by the Florida Department of Transportation.

“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.”...
https://www.washingtonpost.com/news/...=.9abf14fc098a
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Old 16th March 2018, 07:32 PM   #91
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Originally Posted by Trebuchet View Post
Obviously not the suspension cables. May have been some sort of temporary ones associated with the move or intended to stabilize it until completion.
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Old 16th March 2018, 07:53 PM   #92
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Originally Posted by MikeG View Post
I suspect it is far more likely that Rubio got hold of the wrong end of the stick, then spouted something about cables to the press, who without checking have passed it on verbatim, and thus a whole new set of rumours have started.
There wouldn't have been any "checking" to do. The press wasn't reporting what happened to the bridge, they were reporting what Rubio had said:

Quote:
Florida Sen. Marco Rubio, who visited the bridge site Thursday, posted on Twitter: …
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Old 16th March 2018, 11:15 PM   #93
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Originally Posted by William Parcher View Post
Engineer on Florida bridge project called state two days before deadly collapse to report crack, state says


https://www.washingtonpost.com/news/...=.9abf14fc098a

My father was a civil construction site foreman that was given high priority trouble-shooting projects. He took a look at a bridge in Natal South African that was at the end of being loaded tested. Load testing means putting heavy sacks of sand on it for a few weeks and checking the structure.

The engineers had passed the bridge, and my fathers interest was just passing look. But he inspected the bridge closely and with an experienced eye. He looked where others did not look and found some small cracks.

He called in and raised the alarm. He knew those cracks should not have been there. The bridge was found to be defective - there was a serious design flaw. The scandal nearly bankrupted the company but at least there were no fatalities.
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Old 17th March 2018, 12:46 AM   #94
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Originally Posted by ahhell View Post
It's pretty difficult for that to go unnoticed during construction. The truck arrives with a ticket that lists the concrete mix design and relevant specified properties. It under goes visual inspections prior to placement and their are regular samples taken for later testing.

Granted, you have to wait 28 days to test those samples.
And yet it happens. Especially if the Mafia is involved with one of the subcontractors. See the Ted Williams tunnel collapse in Boston some years back.
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Old 17th March 2018, 05:06 AM   #95
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Originally Posted by Elagabalus View Post
AvE does the takedown:

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follow up video here

looks like one of the post tensioning rods snapped
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Old 17th March 2018, 05:25 AM   #96
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Clearer video of the collapse taken from a dashcam available here (you may want to run it at half speed):

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Old 17th March 2018, 05:36 AM   #97
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Old 17th March 2018, 06:04 AM   #98
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Old 17th March 2018, 06:57 AM   #99
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so no crisis actor, false flag, controlled demolition claims yet?
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Old 17th March 2018, 07:17 AM   #100
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I can't find a link just now but the teevee is reporting confirmation that they were indeed tightening cables when the accident occurred.
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Old 17th March 2018, 07:23 AM   #101
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Originally Posted by Whip View Post
so no crisis actor, false flag, controlled demolition claims yet?
Here ya go.

No, I haven't watched any of that crappe.
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Old 17th March 2018, 08:37 AM   #102
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Originally Posted by ddt View Post
I was wondering about that too. How is a (pedestrian) bridge over a road different than a (car) bridge over the busiest river in NW Europe? Here's some pictures of the bridge put in place near my home, Nov 2013. I'm not in the construction business, so I may be overlooking a simple explanation, but the idea to build the bridge off-site and then sail/drive it into place doesn't seem very revolutionary to me.
I can think of a few rail bridges - some over other rail tracks, so over roads - that have been built within London in the last decade by similar methods. A good example is one built at Borough Market to increase the number of tracks to the west of London Bridge station. This blog entry shows the main section - painted grey with the curved tubular side - as constructed on top of the new viaduct, before it was slid over the road. Once the supports on the other side of the road (shown in the fifth picture) were completed, the section was moved across over the course of a three-day Bank Holiday weekend, as seen here.

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Old 17th March 2018, 09:08 AM   #103
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Originally Posted by ginjawarrior View Post
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follow up video here

looks like one of the post tensioning rods snapped
The TL/DW on that, as I understand it:
The rod in question may have already been overstressed and was yielding. They saw it was loose, didn't understand why, and were tightening it further, causing it to snap. It's a fairly reasonable hypothesis. It'll probably take six months or more before we have an official result.
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Old 17th March 2018, 09:29 AM   #104
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Originally Posted by Trebuchet View Post
Here ya go.

No, I haven't watched any of that crappe.
*sigh* dopes
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Old 17th March 2018, 11:08 AM   #105
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Originally Posted by ginjawarrior View Post

follow up video here

Nice twofer - a guy who's in love with the sound of his own voice AND takes forever to get to the damn point.
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Old 17th March 2018, 11:31 AM   #106
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Originally Posted by Trebuchet View Post
I can't find a link just now but the teevee is reporting confirmation that they were indeed tightening cables when the accident occurred.

What puzzles me a little bit about this is that PT cables are generally tensioned one at a time, not all at once, and there are generally quite a few of them, in different configurations depending on the design.

The failure of one tendon (the technical term for a PT cable) doesn't generally result in a catastrophic failure because the others are still there, working, unless some other factor exacerbates the failure.

The cable used for PT reinforcing is usually a seven strand, 5/8" cable in a plastic sheath, well greased so that it can move easily when the tension is being applied. The number of tendons used is a function of the design load, as is the placement pattern.

There are other PT systems, and I have installed a few of them, too. One, called DYWIDAG is a threaded rebar post-tension system much like the cables I described above, only more biggerer. ()

Like I mentioned upthread, I've installed a lot of PT and that includes the tensioning. I've seen a lot of failure modes. I've had to re-tension tendons for various reasons under different circumstances and conditions. It's always a bit more of a ticklish procedure than the first time they are tensioned, but one tendon breaking (which has happened to me) isn't what causes any of the more flamboyant failures I've witnessed. That has almost always been a result of substandard concrete, or improper placement of the concrete during the pour. This would include the tendons themselves being moved out of position during the placement of the concrete.
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Old 17th March 2018, 11:32 AM   #107
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Originally Posted by ddt View Post
I was wondering about that too. How is a (pedestrian) bridge over a road different than a (car) bridge over the busiest river in NW Europe? Here's some pictures of the bridge put in place near my home, Nov 2013. I'm not in the construction business, so I may be overlooking a simple explanation, but the idea to build the bridge off-site and then sail/drive it into place doesn't seem very revolutionary to me.

It isn't.
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Old 17th March 2018, 12:11 PM   #108
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Originally Posted by ginjawarrior View Post
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follow up video here

looks like one of the post tensioning rods snapped

I watched all the way through this video, and I can't find any fault with his diagnosis.

I recommend watching it. Once you get past his long-winded intro it moves pretty smoothly.

It was cool that he got hold of some actual drawings of the bridge, detailing the PT tendons.

They were using a PT rebar system similar to the one I just mentioned. He's exactly right about the behavior of the ram (the gizmo that actually applies the tension to the tendon). It looks like the bar they were pulling broke.

Because of the nature of the rebar PT system they were using, and the application in a concrete member of limited cross-section there probably weren't a lot of tendons, which would mean less redundancy in the case of a failure of one. There may only have been one. I'm going to go back to the blowup of the failure point in his video and see if i can pick out any more anchor points in the debris around the one which failed. But the failure of one may have been enough, lacking the redundancy of sufficient multiple tendons, to reach the failure point of the structure.

There's a lot I could say about the what should have been seen as that rod was being tensioned, but suffice it to say that the workers operating the ram should have realized from the behavior of the pressure gauge that something was wrong.

One minor, trivial point. Toward the end of his video he mentions the crane that was there at the area where they were stressing (tensioning) the bar, as if it might have been there to assist support. It wasn't doing anything. At least not when the failure occurred. It was just sitting there.

If it had been connected to that bridge in any way when the failure occurred then the crane would probably have come down too. They aren't designed to do anything but lift stuff and lower it ... slowly. If you want to bring a crane down then pull the load out of plumb, in any direction. Some cranes can resist more, some less, But anything like the way that bridge came down, and the crane would be down as well.

If you watch the dashcam video showing the moment it failed you can see that the crane didn't even wiggle.

Anyway, thanks gw, for sharing the link. I'd say that as far as explaining the moment of failure itself, it is spot on.
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Old 17th March 2018, 12:13 PM   #109
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Originally Posted by Checkmite View Post
Nice twofer - a guy who's in love with the sound of his own voice AND takes forever to get to the damn point.
In fairness, he's probably had a few beers.
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Old 17th March 2018, 12:17 PM   #110
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Basic question (and I apologize if I missed the answer earlier): If this bridge was supposed to be supported by cables extending from a central tower, as drawings indicate, how/why could they remove the temporary supports under it before the tower and cables were constructed? The bridge wasn't designed to support itself.
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Old 17th March 2018, 12:27 PM   #111
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Originally Posted by quadraginta View Post
I watched all the way through this video, and I can't find any fault with his diagnosis.

I recommend watching it. Once you get past his long-winded intro it moves pretty smoothly.

It was cool that he got hold of some actual drawings of the bridge, detailing the PT tendons.

They were using a PT rebar system similar to the one I just mentioned. He's exactly right about the behavior of the ram (the gizmo that actually applies the tension to the tendon). It looks like the bar they were pulling broke.

Because of the nature of the rebar PT system they were using, and the application in a concrete member of limited cross-section there probably weren't a lot of tendons, which would mean less redundancy in the case of a failure of one. There may only have been one. I'm going to go back to the blowup of the failure point in his video and see if i can pick out any more anchor points in the debris around the one which failed. But the failure of one may have been enough, lacking the redundancy of sufficient multiple tendons, to reach the failure point of the structure.

There's a lot I could say about the what should have been seen as that rod was being tensioned, but suffice it to say that the workers operating the ram should have realized from the behavior of the pressure gauge that something was wrong.

One minor, trivial point. Toward the end of his video he mentions the crane that was there at the area where they were stressing (tensioning) the bar, as if it might have been there to assist support. It wasn't doing anything. At least not when the failure occurred. It was just sitting there.

If it had been connected to that bridge in any way when the failure occurred then the crane would probably have come down too. They aren't designed to do anything but lift stuff and lower it ... slowly. If you want to bring a crane down then pull the load out of plumb, in any direction. Some cranes can resist more, some less, But anything like the way that bridge came down, and the crane would be down as well.

If you watch the dashcam video showing the moment it failed you can see that the crane didn't even wiggle.

Anyway, thanks gw, for sharing the link. I'd say that as far as explaining the moment of failure itself, it is spot on.
Would this “something was wrong” have occurred slowly as the rod was being tensioned or quickly as a certain level was reached? Also, what would the solution be? I’m guessing that stopping the process would have prevented collapse.
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Old 17th March 2018, 12:29 PM   #112
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Originally Posted by quadraginta View Post
One minor, trivial point. Toward the end of his video he mentions the crane that was there at the area where they were stressing (tensioning) the bar, as if it might have been there to assist support. It wasn't doing anything. At least not when the failure occurred. It was just sitting there.

If it had been connected to that bridge in any way when the failure occurred then the crane would probably have come down too. They aren't designed to do anything but lift stuff and lower it ... slowly. If you want to bring a crane down then pull the load out of plumb, in any direction. Some cranes can resist more, some less, But anything like the way that bridge came down, and the crane would be down as well.

If you watch the dashcam video showing the moment it failed you can see that the crane didn't even wiggle.
I think that crane was there to lift the tension gear. It certainly was not to support the bridge.
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Old 17th March 2018, 12:35 PM   #113
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Originally Posted by quadraginta View Post
One minor, trivial point. Toward the end of his video he mentions the crane that was there at the area where they were stressing (tensioning) the bar, as if it might have been there to assist support. It wasn't doing anything. At least not when the failure occurred. It was just sitting there.
I disagree.

YouTube Video This video is not hosted by the ISF. The ISF can not be held responsible for the suitability or legality of this material. By clicking the link below you agree to view content from an external website.
I AGREE


Watch the dashcam video of the collapse again. I believe it may help to open the video on the YouTube page and increase its size to make the events clearer to see.

On the top of the bridge, partially hidden by the crane structure, you can see a pair of workers above one of the bridge "struts", right where they should be if they were tightening the tension bolts in that location as described. When the bridge snaps and falls, the visible worker can be seen falling with it, and for a split second some kind of object is "left behind" in the air above him before it too falls. Since real life is not a Wile E. Coyote cartoon, the only reasonable explanation seems to be that the object had been suspended on something and then fell off - I believe it was the end of the crane's cable (which is mostly invisible in the video). I don't know what the object is or why or how it was being used, but it does seem to have been attached to the crane.
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Old 17th March 2018, 12:49 PM   #114
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I've started reading the thread on an engineering message board which is linked to in the above video.

A couple of good photos are linked to in one of the early posts,

This one shows the typical PT cable slab reinforcement coming out from the edge of the bridge slab right before the place it. Look at the bottom right of the photo just above the pier they are about to set it on. You'll see some black spots in a line on the edge of the slab, which are actually voids, the pockets that the cable ram sticks into to engage and pull the cables. If you look closely you can see the ends of the cables themselves hanging out.

ETA: Okay, I didn't get that right. Here's a much larger blow-up of that area. I still think those have to do with the bridge slab PT, but it's a system I'm unfamiliar with. At any rate, it wasn't involved in the failure.

The other is a large, clear blow-up of the area of the collapse. You can see the rebar tendon which they had been stressing, with the ram they were using still on the rebar tendon itself.

If you go back to the dashcam clip linked to upthread, and watch the moment of failure closely, you can see one of the guys who was operating that ram when the tendon failed ... falling through the air after the fallen bridge.

It kinda gives you an idea of how quickly that thing came down. He had to catch up to it.

And I take back what I said about the crane. It was hooked up to something he was working with or near, but still not connected to the bridge.

At first I thought that maybe it was hooked up to a safety harness he was wearing, but unless it was an almost unbelievably cheap one, he wasn't. It failed too quickly.

Whatever it was it was small, and it went down with him
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Old 17th March 2018, 01:01 PM   #115
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Originally Posted by quadraginta View Post
The other is a large, clear blow-up of the area of the collapse. You can see the rebar tendon which they had been stressing, with the ram they were using still on the rebar tendon itself.
In that case, we know what the crane was hooked up to - the ram. The crane's cable is still hooked up to it and wrapped around it in that photo. Presumably it's a heavy piece of equipment and having it hoisted by the crane made it easier to manipulate than trying to handle it manually.
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Old 17th March 2018, 01:32 PM   #116
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Originally Posted by quadraginta View Post
And I take back what I said about the crane. It was hooked up to something he was working with or near, but still not connected to the bridge.

At first I thought that maybe it was hooked up to a safety harness he was wearing, but unless it was an almost unbelievably cheap one, he wasn't. It failed too quickly.

Whatever it was it was small, and it went down with him
could it be the pump for the ram? it could have been lifted up there with rope that broke when the hydraulic pipes dragged it down
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Old 17th March 2018, 01:47 PM   #117
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Another note from the second AvE video: He points out that the jack thingummies used to support and move the bridge weren't located as shown on the original drawing, especially at the end that failed. One that should have been under the end of the bridge was instead near the center, because the ground where it should have been wasn't suitable. That left the overhanging end of the bridge unsupported during the move. It wasn't designed for loads in that direction. I'm therefore wondering if that load caused the stretching of the post-tension member which led to its failure when being tightened.
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Old 17th March 2018, 02:06 PM   #118
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Originally Posted by Checkmite View Post
In that case, we know what the crane was hooked up to - the ram. The crane's cable is still hooked up to it and wrapped around it in that photo. Presumably it's a heavy piece of equipment and having it hoisted by the crane made it easier to manipulate than trying to handle it manually.

Maybe the hydraulic pump when they sent it up top. The ram itself is still threaded onto the bar. They wouldn't have left the crane hooked up to it.
The hydraulic pumps which power the rams are boxes about twelve to sixteen inches to a side and maybe a foot or so high. All the ones I ever used, anyhow. They aren't all that difficult for one man to tote around, although they certainly might have used the crane just to set it up on top where the work area was.

Neither one is too heavy for one man to handle, although if you want to carry the ram they use for PT rebar very far two peope are definitely preferable (I know this from personal experience). That one looks smaller than the ones I've used to stress DYWDAG, but I'm sure they've been improved a lot since I worked with them in the 70s. And I suspect that may be a different system than the ones I used. One of the vehicles crushed under that bridge is a VSL truck, and back when I was installing reinforcing I worked with them a lot, and I don't think they used the DYWIDAG system. They may have their own now.


That line you see coming from the end of the ram itself is the hydraulic line that operates the ram. I'm not sure that the line we're looking at hanging in the air in that photo is something which was there at the moment of failure. It might be.

The resolution of the dashcam makes it hard to tell, but I couldn't see the load line from the crane hanging down all the way to the debris after the fall. It wouldn't have been in freefall like that anyway. It looks like whatever was hooked to the crane broke loose and fell along with everything else. That crane wasn't hooked to anything which was connected to any part of the bridge when it collapsed. Not for long, anyway.
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Old 17th March 2018, 02:07 PM   #119
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Originally Posted by ginjawarrior View Post
could it be the pump for the ram? it could have been lifted up there with rope that broke when the hydraulic pipes dragged it down

Yes. You anticipated me.
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Old 17th March 2018, 02:20 PM   #120
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Originally Posted by DGM View Post
I think that crane was there to lift the tension gear. It certainly was not to support the bridge.

I expect it was there for all sorts of things. It isn't a very big crane. Yeah, if it was handy they certainly would have taken advantage of it to get the gear up there. If it wasn't they would have carried or roped it up. That equipment is designed to be managed by one or two men. It isn't that heavy. I've carried a DYWIGAG ram up a few flights of stairs when we needed it up top and the jobsite's crane was busy with more important stuff.
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