US pedestrian bridge collapse

Conekicker · Post by **Conekicker** » Thu Mar 15, 2018 19:54

http://www.bbc.co.uk/news/world-us-canada-43418898

That looks a very slender construction for the width of the span.

WHBM · Post by **WHBM** » Thu Mar 15, 2018 20:20

The more apparent part of the collapsed bridge seems to be a combined roof/truss structure, which presumably gave strength to the minimalist deck. However the vertical trusses all seem to have failed in the collapse. Looks like a "clever" bit of design. 900 tons does seem a lot for that, though, all precast concrete.

However, as it was only lifted in 4 days previously, and probably hadn't even opened to pedestrians, I would be looking at the installation. When we put a pre-fab bridge structure over the M8 in Blochairn in the east of Glasgow in 1974, it was swung in by a heavylift crane. One end came down too hard on the bearing and damaged it, which was just mortared over. True. We all went into the office the next day and shook our heads, but the bridge is still there.

Conekicker · Post by **Conekicker** » Thu Mar 15, 2018 20:35

First of it's kind according to the report.
And the last?

nirs · Post by **nirs** » Thu Mar 15, 2018 21:25

I was looking at the images. The diagonal trusses seem to be generally intact from what I can see - a number have been forced up through the roof which probably happened as a result of the impact with the ground rather than being the cause of the collapse. At one end the deck is lying sloped down at an angle, but at the other end it looks as if the end of the deck has completely sheared away from the pillar and dropped straight down. Perhaps the sequence of events is that one end of the lower deck has snapped, close to the pillar, with the result that the rest of the bridge then pivoted down on the opposite pillar, and the impact with the roadway then resulted in the central portion crumpling.

Glen · Post by **Glen** » Thu Mar 15, 2018 21:38

It seems it was going to be cable stayed when complete. Which begs the question what temporary works were in place?

Dadge · Post by **Dadge** » Thu Mar 15, 2018 22:19

Yes, they must've calculated that it'd stay up in this incomplete state...

Earlier videos https://www.youtube.com/watch?v=5Y_71L35CvM
https://www.youtube.com/watch?v=hvZVuN-CHnE
https://www.youtube.com/watch?v=juRvYb9_0f4

WHBM · Post by **WHBM** » Fri Mar 16, 2018 07:28

Glen wrote:It seems it was going to be cable stayed when complete. Which begs the question what temporary works were in place?

DYW1vOzUQAAiV5h.jpg

That seems to show the bridge was incomplete, the second span not across the road was not in place. As far as I can see the tower was not either, nor the cable stays. I wonder who thought it could even temporarily stay up unsupported like that.

One US news report says they were doing stress tests - at the time. With live traffic underneath ...

Bryn666 · Post by **Bryn666** » Fri Mar 16, 2018 12:12

The CDM Regulations were just something that happened to other people, weren't they, Baldrick...

KeithW · Post by **KeithW** » Fri Mar 16, 2018 14:38

WHBM wrote:
Glen wrote:It seems it was going to be cable stayed when complete. Which begs the question what temporary works were in place?

DYW1vOzUQAAiV5h.jpg
That seems to show the bridge was incomplete, the second span not across the road was not in place. As far as I can see the tower was not either, nor the cable stays. I wonder who thought it could even temporarily stay up unsupported like that.

One US news report says they were doing stress tests - at the time. With live traffic underneath ...

The pictures on the CBS website show show major supports in place while the bridge was positioned. One eye witness reported that the central pillar collapsed after the temporary supports had been removed while construction crews were adjusting cable tensions.

https://www.cbsnews.com/news/florida-in ... 018-03-15/

One driver had a luck escape when stopped partly under the bridge. She reported what seemed like rocks hitting the roof of her car just before the bridge collapsed crushing the rear half of the vehicle. Reportedly they were using an 'innovative accelerated construction technique' which as an old engineer with lots of construction experience raises red flags to the mast head. Its certainly not something I would want to do over a live road.

http://www.miamiherald.com/news/local/c ... 16174.html

mikehindsonevans · Post by **mikehindsonevans** » Fri Mar 16, 2018 15:17

WHBM wrote:
Glen wrote:It seems it was going to be cable stayed when complete. Which begs the question what temporary works were in place?

DYW1vOzUQAAiV5h.jpg
That seems to show the bridge was incomplete, the second span not across the road was not in place. As far as I can see the tower was not either, nor the cable stays. I wonder who thought it could even temporarily stay up unsupported like that.

One US news report says they were doing stress tests - at the time. With live traffic underneath ...

Along with a healthy dose of "there but for the grace of God go I", it makes me appreciate the UK regulations which seem to ban any access close to an unsupported overhanging superstructure. Thank heavens the Queensferry Crossing construction teams were not using the new innovative methods for the new cable-stayed bridge across the Firth of Forth.

Given that this is happening in the former Colonies, I am sure that the cause will be leaked regularly as the enquiries gather pace. What price a follow-on rule preventing traffic from stopping under an overbridge? You may laugh now.....
Mike

Post by **Big L** » Fri Mar 16, 2018 21:23

Of course, if you apply recent Trump logic, this could have been prevented by arming the construction crew.

fras · Post by **fras** » Fri Mar 16, 2018 23:52

I do remember this one: -

http://www.bbc.co.uk/blogs/wales/entrie ... 135633558c

Somebody obviously got the maths wrong. It was all slide rules and pen and ink stuff then of course.

sydneynick · Post by **sydneynick** » Sat Mar 17, 2018 00:41

It seems the lessons of the Cleddau Bridge did not sink in fast enough. It collapsed during construction on 2 June 1970. On 15 October 1970, the similar West Gate Bridge in Melbourne also collapsed during construction.

B1040 · Post by **B1040** » Sat Mar 17, 2018 08:28

Looks like an engineer saw a crack but only "left a message".
https://www.theguardian.com/us-news/201 ... lt-walkway

the Florida department of transportation (FDOT) revealed that the lead engineer working for one of the companies involved in the bridge construction reported a crack in the structure two days before its collapse. The engineer, W Denney Pate, left a voicemail on the landline of a department employee.

“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,” a transcript of the recording reads.

“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.”

jimbob69 · Post by **jimbob69** » Sat Mar 17, 2018 12:34

According to AvE on YouTube it looks like failure of tensioning cables, possibly caused by them lifting the bridge in a non-prescribed way.

Links (NB, strong language and very candid discussion)

https://www.youtube.com/watch?v=ioC61QW7SHQ
https://www.youtube.com/watch?v=KtiTm2dKLgU

KeithW · Post by **KeithW** » Sat Mar 17, 2018 17:38

jimbob69 wrote:According to AvE on YouTube it looks like failure of tensioning cables, possibly caused by them lifting the bridge in a non-prescribed way.

Links (NB, strong language and very candid discussion)

https://www.youtube.com/watch?v=ioC61QW7SHQ
https://www.youtube.com/watch?v=KtiTm2dKLgU

I am somewhat bemused by the fact that they went to the extent of building an expensive cable stayed custom design concrete bridge when as a footbridge with a 53 m span its hardly cutting edge. If you used a central support you could buy a steel truss bridge pretty much off the shelf. Hell you can buy bailey bridges off the shelf with a 60 m span that you can drive HGV's across !

The Jane Coston Cycle Bridge over the A14 at Milton is rather elegant bridge with a 73 m span which was prefabricated off site and installed in 2004 at a cost of £ 2 million. The A14 was closed overnight while they positioned it and then the ramps and access paths completed. As is all too common with UK road projects the consultation phase was MUCH longer than the construction and installation.

I suspect the fact the University that ordered the Miami Footbridge supposedly specialises in Innovative Designs and Accelerated Construction Techniques played its part. Leading Edge can all too often mean Bleeding Edge.

firefly · Post by **firefly** » Sat Mar 17, 2018 21:43

Am I the only one, who wonders why a bridge is being built there at all? It is a surface street after all. And the crossroads next to the bridge contains pedestrian crossings and is controlled by traffic lights. I fail to see the need for a bridge.

mikehindsonevans · Post by **mikehindsonevans** » Sat Mar 17, 2018 21:58

firefly wrote:Am I the only one, who wonders why a bridge is being built there at all? It is a surface street after all. And the crossroads next to the bridge contains pedestrian crossings and is controlled by traffic lights. I fail to see the need for a bridge.

Firefly - no, you are not alone.
Is this an "Emperor's new clothes" scenario, perhaps? No-one thought to state the haemorrhagingly obvious.
At least it wasn't California.

ANiceEnglishman · Post by **ANiceEnglishman** » Sat Mar 17, 2018 22:35

mikehindsonevans wrote:
firefly wrote:Am I the only one, who wonders why a bridge is being built there at all? It is a surface street after all. And the crossroads next to the bridge contains pedestrian crossings and is controlled by traffic lights. I fail to see the need for a bridge.
Firefly - no, you are not alone.
Is this an "Emperor's new clothes" scenario, perhaps? No-one thought to state the haemorrhagingly obvious.
At least it wasn't California.

Here's the PR blurb

https://news.fiu.edu/2016/03/fiu-sweetw ... ture/98724

Further enhancing an already solid relationship, FIU broke ground March 29 on a bridge that will connect the Modesto A. Maidique Campus to its northerly neighbor, the City of Sweetwater.

Part of a larger transportation initiative, the idea is to create a safer path for the students and local residents who cross between Sweetwater and FIU each day. Though the exact number of pedestrians crossing SW 8th Street at 109th Avenue is unknown, it is estimated that more than 4,000 FIU students currently live in Sweetwater, in addition to the Sweetwater youth who aspire to attend college one day.

“There are thousands of young people who deserve the hope, deserve the opportunity that our university can provide,” Rosenberg said. “So it made no sense to allow this fence of Tamiami Trail to impeded the relationship that we have, that we needed to have, that we wanted to have, that is so much in our DNA.”

The bridge also represents the partnership that FIU and the City of Sweetwater have forged through projects and student engagement in the community, including research and service initiatives in the Honors College; health care services provided to the community by the Herbert Wertheim College of Medicine; the Frost Art Museum’s partnership with Sweetwater Elementary to enhance art education; and more.

“This bridge literally connects FIU with the rest of the community,” said Congresswoman Ileana Ros-Lehtinen, who attended the groundbreaking ceremony. “Some schools like to be ivory towers and be set apart. FIU, that’s never been their mission. They’ve been a community-centered school, and this bridge is a symbolism of how connected FIU wants to be with our community.”

Pendlemac · Post by **Pendlemac** » Sat Mar 17, 2018 23:13

mikehindsonevans wrote:
firefly wrote:Am I the only one, who wonders why a bridge is being built there at all? It is a surface street after all. And the crossroads next to the bridge contains pedestrian crossings and is controlled by traffic lights. I fail to see the need for a bridge.
Firefly - no, you are not alone.
Is this an "Emperor's new clothes" scenario, perhaps? No-one thought to state the haemorrhagingly obvious.
At least it wasn't California.

One of the reasons for building the bridge was that at least one student has been killed crossing the road.

The design of the bridge incorporates a lift at each end, making a much safer route for anyone who is mobility-impared.

SABRE

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