The accident involving a bridge under construction happened several days ago and I found a video of the actual collapse.

It also looks like this prestressed concrete bridge had no torsional strength and it was supported only at the ends at the time it fell. Also, it weighed over 900 tons which seems awfully heavy for just a pedestrian bridge. Seems the whole project was a catastrophe in the making -and it finally happened.

 

The accident involving a bridge under construction happened several days ago and I found a video of the actual collapse.

https://forum.allaboutcircuits.com/threads/thought-for-the-day.44743/page-8#post-1249039

It also looks like this prestressed concrete bridge had no torsional strength and it was supported only at the ends at the time it fell. Also, it weighed over 900 tons which seems awfully heavy for just a pedestrian bridge. Seems the whole project was a catastrophe in the making -and it finally happened.

One current theory is that the bridge was damaged during the move. The diagonal directly just left of the crane had a compression fault that caused the tension cable to loosen when the jack lifted the bridge for transport. When they tried to re-tension the cable there was a total compression fault of that one support the caused a shear fracture on the top then bottom plates. The breaks in the upper/lower plates happen where the diagonal support just right of the crane connects.

 

There was a voice mail before the collapse ... discovered after the collapse stating there were cracks but everything is safe.

http://www.miamiherald.com/news/local/community/miami-dade/article205627294.html

 

Tensioned cable reinforcement can be very hazardous if everyone doesn't check for every Dotted I and Crossed T.

Apparently, the concrete cracked and loosened one or more of the cables. Furthermore, the bridge was supposed to have overhead cables anchored to a tower that were not in place. In the mean time, it was supported only at the ends. A case of really bad planning.

 

Tensioned cable reinforcement can be very hazardous if everyone doesn't check for every Dotted I and Crossed T.

Apparently, the concrete cracked and loosened one or more of the cables. Furthermore, the bridge was supposed to have overhead cables anchored to a tower that were not in place. In the mean time, it was supported only at the ends. A case of really bad planning.

The overhead cables were not for the bridge support. They were designed as stiffeners to reduce harmonic oscillations when people walked on the bridge. Each section was designed to be self supporting when properly adjusted on the mounting pylons.

 

There are many pedestrian bridges over streets and highways, however that bridge was an overpriced white elephant.

I suspect it was one of those "pork" projects intended to run up design fees, change orders, and cost overruns. The same thing happened with the new bridge across San Francisco Bay. However, it hasn't collapsed - yet.

 

https://www.usatoday.com/story/news...se-suspension-cables-support-tower/431418002/

Corrections and clarifications: This story has been corrected to describe the pedestrian bridge as a truss design, despite its cosmetic appearance as a cable-stayed bridge.

The central column and cables that appeared in the design of a collapsed pedestrian bridge in Miami were decorative and not needed to support the span, federal investigators and bridge designers said Friday.
Bridge engineers had questioned why the column designed to rise above the bridge deck to a height of 109 feet wasn’t erected before a large section of the bridge deck was hoisted into place Saturday.
The 174-foot section of deck collapsed Thursday, killing at least six people.
But while the column would have been needed as part of the support for a cable-stayed bridge, it was not needed for a truss bridge.
Cheryl Stopnick, an outside spokeswoman for FIGG Bridge Engineers, which designed the bridge, said the structure was “truss bridge with above-deck truss elements.”

Just to be clear on the bridge type.

Robert Accetta, the National Transportation Safety Board investigator in charge, said diagonal elements between the bridge’s canopy and deck worked like a truss bridge. But the cables designed to fan out from the column weren’t needed to support the bridge deck, he said.

“As I understand it, these were cosmetic,” Accetta said. “They were not structural members.”

 

 

Looks like the media is finally getting a clue.
http://www.miamiherald.com/news/local/community/miami-dade/west-miami-dade/article206122229.html

Steel-truss bridges have been commonly used in roadway construction going back decades. But they have a well-known vulnerability: If a vehicle hits one of the horizontal support trusses, the entire span can collapse.

That’s what happened in the 2013 collapse of a 1955 steel-truss bridge over the Skagit River on Interstate 5 near Seattle: A truck carrying an oversized load struck supporting steel struts along one side of a bridge span, which split apart and fell into the river. That’s because there were no backup or redundant structural elements to support the span if one piece failed.
...
His source is not clear. But the Associated Press said in a story Tuesday that the Florida Department of Transportation ordered the northern support pylon be moved 11 feet to make room for future expansion of the trail. That required a design change that lengthened the span — and put the support pylon in the dirt well off the edge of the roadway, which could also explain why the northernmost truck could no longer follow its original planned route.

 

It collapsed when they were tuning the bridge.

 

It collapsed when they were tuning the bridge.

I'm thinking they were trying to fix what was broken during the move when something snapped. In single center row truss bridge every single truss is a trip-wire to total destruction.

That's a Hydraulic jack (blue on the cable A) and the blue box to the left of it looks like the fluid tank and controller. I think that cable should be still inside the truss 11 like cable B.

 

What ever went wrong and with the result of 6 fatalities, the personal injury lawyers are swarming like sharks in warm water off the coast of Miami.

 

What ever went wrong and with the result of 6 fatalities, the personal injury lawyers are swarming like sharks in warm water off the coast of Miami.

If a member of my family was crushed to a pancake by that bridge I would be looking for the best shark.

 

Hi,

Well that just shows ya how far American engineering has come. Cant even put up a walk bridge.

By comparison, look at what they did in Millau. A true monumental task completed in record time and here they cant even put up a simple walking bridge without terrible problems.

I am tempted to openly mock them for that deadly incident, but i realize that they will have to live with what they did for the rest of their lives.

 

The reason this is news is because this type of engineering (is seems to be a construction failure because the walkway was still being built) failure is so rare. No one yet has found a way to defeat Murphy.

American engineering is just fine. The Tillman Hoover Dam Bypass bridge is an amazing structure because the true Bridge Builders know their job.

 

Hello,

My theory is that they looked at it as being simpler than it really was.
With the larger projects, they pay more attention to detail because the loss is much worse.

We used to have a saying way back so long ago:
"The hardest thing to do in electronics design is to get a light bulb to light"

which in the modern sense includes an LED also.
The reason this came up was because it seems so simple to light up a bulb (or LED) that we often overlook something and thus it doesnt work, while the complicated things work out so well.
We've had the layout guys constantly mess up the three terminal voltage regulator board layouts, flipping two of the leads. The other IC's with 14 pins or more were almost always right on the first try when they came back for verification.

 

https://www.miamiherald.com/news/local/community/miami-dade/article216703455.html

 

Hello,

Thanks for posting that, very interesting and i'll be watching for more info on this.

As most people know by now, Italy just had a big bridge collapse too. I wont go into detail but it was very bad.
One of my uncles designs bridges.

 

hi Al,
People are blaming the bridge designer and poor maintenance being a possible cause of the Genoa bridge failure.
Italy is in a geological active zone, a number of recent earthquakes have occurred in that region, I wonder if that fact is being considered.?

E

 

hi Al,
People are blaming the bridge designer and poor maintenance being a possible cause of the Genoa bridge failure.
Italy is in a geological active zone, a number of recent earthquakes have occurred in that region, I wonder if that fact is being considered.?

E

Genoa bridge failure

There is a similar bridge designed by the same person that closed in 2017 for a period of time because of possible structural failures.
https://www.libyaobserver.ly/inbrief/authorities-east-libya-close-wadi-el-kuf-bridge-safety-reasons
https://en.wikipedia.org/wiki/Wadi_el_Kuf_Bridge

Another.
https://www.thelocal.it/20180817/fears-over-twin-of-collapsed-genoa-bridge-in-venezuela

Venezuelans are concerned over the safety of a "twin" viaduct of the collapsed Morandi bridge in Genoa, Italy, after a fire on the concrete structure caused a major blackout.
The 8.6 kilometer (five mile) General Rafael Urdaneta viaduct links second city Maracaibo with the rest of Venezuela.

Designed by Italian structural engineer Riccardo Morandi, it predates by five years his 1967 bridge in Genoa that collapsed this week causing the death of 39 people.

Experts are preparing a report on the condition of the Venezuelan structure following the fire last Friday which destroyed an electricity transformer, forcing the closure of the bridge and leaving millions without power for several days.
...
The Maracaibo bridge, inaugurated in 1962, remained closed between Friday and Monday and was only partially re-opened by Wednesday.

The incident heightened concerns over the structural integrity of the bridge and left the surrounding Maracaibo and San Francisco areas, home to four million people, without power for several days.