This afternoon a 950 ton concrete pedestrian bridge crossing 8 lanes of traffic collapse before I was even opened to the public.?ÿFrom some initial news footage it appears to have been a cable stayed structure, but current new coverage does not show collapsed elements that should have been there. Several people are dead and heavy debris still has to be cleared off the street and a number of cars.
I cannot speculate on the collapse at this time, but feel that the span could have been built using considerably less steel, and also see no reason that a span of that length had to be supported by cable stays.
Paul in PA, PE, PLS
It's been all over the News in Fl. Another example of human incompetence. Last I heard there are still 6 crushed cars under the collapsed walkway. CNN is covering it also.
It's here too:?ÿ http://www.dailymail.co.uk/news/article-5506597/Pedestrian-bridge-collapses-cars-people-campus.html
It was a bridge built using "accelerated construction practices" according to the news. They showed time-lapse footage of the placement, which looked like they had pre-constructed it, then shipped it in and bolted it in place. It wasn't open to the public yet, but obviously they were allowing traffic to flow underneath.
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I just watched a vid of this last week about them placing the span:
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Fact Sheet:
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https://news.fiu.edu/wp-content/uploads/17703_EXT_FIU_Bridge_Move_Fact_Sheet_030918_DIGITAL.pdf
That article claims they used a new type of environmentally friendly concrete for very first time. Perhaps it is not strong enough.
The new bridge is the first in the world to be constructed entirely of ?ÿself-cleaning concrete. Titanium dioxide will keep its surface white, remove pollutants from the air, and decompose UV radiation. The titanium dioxide, when exposed to sunlight, captures the pollutant particles from the air and self-cleans its own concrete surfaces. This reduces maintenance. This self-cleaning concrete is considered a promising tool for reducing pollutant load on heavily congested traffic routes.
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It's at Florida International University in Miami, Florida Atlantic University is in Boca Raton
Here is the firm that designed it (according to my local news channel)?ÿ
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N10,000, E7,000, Z100.00
PLS - IL, MO, AR, KS, MN, KY
It collapsed during a post tensioning process because of "sag". Everybody involved is going to blame each other and it will take some time to figure it all out.
It collapsed during a post tensioning process because of "sag". Everybody involved is going to blame each other and it will take some time to figure it all out.
Wow!, and they didn't think to?ÿshut down traffic during?ÿthat process?
If this is true, there will be plenty of ambulance chasing lawyers heading to the area.
It collapsed during a post tensioning process because of "sag". Everybody involved is going to blame each other and it will take some time to figure it all out.
Wow!, and they didn't think to?ÿshut down traffic during?ÿthat process?
If this is true, there will be plenty of ambulance chasing lawyers heading to the area.
Both the engineering firm and the contractor are probably going to go bankrupt.?ÿ Even if the design and/or construction were correct SOMEONE is going to pay.?ÿ In cases like this the attorneys use the "shotgun" method, sure everyone.?ÿ A firm for whom I worked was sued when a contractor left a ditch open overnight and someone ran off the road and into the ditch.?ÿ We were not the inspectors on the job and had had nothing to do with it since the bids and award of the contract, but the insurance company settled because it was cheaper than the cost of legal defense.
Don't get me wrong.?ÿ If one or the other screwed up they SHOULD pay, but I'll wait until ALL the facts come out before I make any judgement.
Andy
It collapsed during a post tensioning process because of "sag". Everybody involved is going to blame each other and it will take some time to figure it all out.
Wow!, and they didn't think to?ÿshut down traffic during?ÿthat process?
If this is true, there will be plenty of ambulance chasing lawyers heading to the area.
"Wow!, and they didn't think to?ÿshut down traffic during?ÿthat process?"?ÿ
Who knows, was it because the bridge designer wanted to show off new construction methodology that wouldn't disrupt traffic flow, or was the concrete mix incorrect, or did they post tension incorrectly......
I agree about shutting down the roadway during the process that caused the failure, that was a stupid decision on someone's behalf.?ÿ
The Lawyers are in litigation heaven.
I feel bad for the Families that are missing a loved one because of this.
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It collapsed during a post tensioning process because of "sag". Everybody involved is going to blame each other
It collapsed during a post tensioning process because of "sag". Everybody involved is going to blame the surveyor.
There, I fixed it.?ÿ?ÿ
Why wouldn't they post tension it with the bottom forms in place to insure positive camber. Then move it. We never move a precast member prior to tensioning it unless it's fully supported.?ÿ Otherwise something like that will happen. To my way of thinking that would be pure negligence and very hard for me to believe.
Steve
Don't understand how they can post-tension the bridge, when not even 1/2 of it was in place.?ÿ The design photos show that it is partially a cable-stay (unless that is all for looks) .?ÿ They still hadn't constructed the 1/2 over the canal, which I would assume would be needed in order to post-tension across the whole structure.?ÿ
I hate it when people speculate after an incident like this, so I am hating myself here: I am betting on one of 2 things.?ÿ
ONE, the 174' span does not reach full strength until the full span is installed, and cable stays installed - meaning someone messed up on the stresses of the single span and it could not bear its own weight until complete.
TWO: The most likely is the soil gave way next to the center abutment.?ÿ If you look at the photos, the abutment looks like it is intact, but leaning away from the bridge on the end which obviously came down first.?ÿ The abutment shifted and the bridge slipped off lacking the other half of the bridge to hold it in place.
It is a tragedy for sure and we feel for all those affected.?ÿ It is hard to think of such things after a tragedy, but I hope they had a scanner in there overnight to preserve the scene so they can remove sections to quickly recover the dead today.
According to the .pdf information sheet, the elements corresponding to cable stays were to be made out of pipe. I'm not an engineer, but I've never seen a cable-stayed bridge with pipe in place of cables. The pipe members would have to be fabricated and hoisted into place, and then how would you tension them? That suggests that the pylon and stays were to be 99% decorative.
This screen grab from the first video shows the span in place before the collapse. There is an object under the span that I thought at first was a temporary support. But on closer examination it's a palm tree and some other object in the background, and there is a line of cars in front of it.
From the other material, it looks as though the pylon was to have been at the left-hand end of the span shown here, with the span across the canal to the left of that.
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Vid of the collapse.?ÿ I think we need vid of the other end though.
The video shows the collapse initiating at the first panel point far end of the lower slab. There is no need to see video of the other end as that end hit the road intact. The design was for cable stays to meet design strength. The only way that section of span should have been set in place without the stays is for temporary supports to be in place. I surmise several people are going to jail.
It is being reported that cables designed to support the bridge became loose and were being retightened. That is incorrect as no such cables or a supporting tower for them was yet in place. It is also being reported that the bridge had undergone a stress test. That to is incorrect. It is probable that the reporter misinterpreted the fact that prestress cables within the bridge are most likely to have been undegoing post tensioning once the span was in place.?ÿ It is also being reported that the firm that was hired to do an analysis of the bridge design was not prequalified to undertake such a job. Based on visible evidence I would consider that statement to be true.
Paul in PA, PE, PL.
The firm that designed the bridge also designed the PA Turnpike bridge over the Allegheny River and the PA Turnpike bridge over the Susquehanna. Not the same type of design of course, but the same company. I grew up about 1/4 mile from the Allegheny River bridge, I used to climb all over the old bridge (steel). I did not understand why they replaced that one, it seemed in good shape, built in the 60's. I very rarely cross that one now, it is not near where I live. But the one over the Susquehanna I do cross probably a dozen times a year.?ÿ
When I lived in Mexico I saw quite a few pedestrian bridges being constructed over wide highways, in fact I had to do a report on one for a pre-stressed class I was taking. They do a lot more concrete construction than we do, so I took three concrete course at the university there: concrete, reinforced concrete, and pre-stressed concrete.?ÿ
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Just my opinion, The bottom slab that appears to be about 30 foot wide would have been in tension and possibly was post-tensioned.
The last diagonal on that end would have been in compression.
I don't picture in my mind how the compressed force in the 3ft. +/- wide diagonal would have been distributed evenly thru the post tensioned 30 ft +/- wide slab. It seems to me there would have been a lot of shear force at that point.
James
(disclaimer, it has been 40+ years since I was in a statics class)