Bridge Collapse in Genoa, Italy 26

[thebard3]

https://www.cbsnews.com/news/italy-...noa-traps-cars-under-rubble-today-2018-08-14/

An interesting theory from the article: "Italian news agency ANSA said authorities suspected that a structural weakness caused the collapse".

Brad Waybright

It's all okay as long as it's okay.

 

[mdepablo]

^^ Here you have a good analysis of the collapse video included in this last link:

http://www.retrofutur.org/retrofutur/app/main?DOCID=1000116032

The video in YouTube:

https://www.youtube.com/embed/nv9bDogDEWw

Credits to krisu99 in Skyscrapercity.com:

https://www.skyscrapercity.com/showthread.php?t=484944&page=529

 

[IRstuff]

One needs to be careful in comparing different structures from different times; we don't know how many structures of old failed, we only see the ones that survived. Additionally, the level of overdesign, the investment, and consequences to the engineers are radically different.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[cranky108]

Good point. What do you think would happen to an engineer in Rome that designed a faulty structure?

On the other hand, what should happen to an engineer that designs a faulty structure?

 

[thebard3]

On the other hand, what should happen to an engineer that designs a faulty structure?

Well, you have to define 'faulty', and what the reason for it might be. In this case, the bridge was unique, and probably required additional and unconventional maintenance, but it DID stand for over 50 years. The design was probably less than ideal, but continuous improvement requires new designs and technologies that don't always show their shortcomings until years or decades later. Like hokie66 pointed out--

Your definition of "overbuilt" differs from mine. That big concrete dome is completely unreinforced. That would be considered inadequate today.

Just because the Pantheon has stood for 2000 years doesn't mean it's an ideal structure. If something is truly deemed 'faulty' because it used questionable materials, designs, techniques and the like, then there should probably be some culpability. If it seemed like a good design at the time and failed due to unforeseen circumstance, then not so much. That question probably gets addressed as part of the FIU bridge collapse.

Brad Waybright

It's all okay as long as it's okay.

 

[IRstuff]

There's also a big difference whether someone intentionally under-designs, as in the case of the Pinto, or simply doesn't know any better, as in the case of browser buffer overflow.

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[charliealphabravo]

I read a study once that tabulated compressive strengths for various samples from Roman concrete structures. I don't remember it being anything remarkable. Like nothing over 1500 or 2000 psi.

As JStephen explained it, the survival of structures made with this concrete is a direct function of their resemblance to a pile. In structural engineering terminology this means: mass concrete designed to operate at very low stress levels and without steel reinforcement. Concrete is exclusively or primarily in compression and has large effective safety factors against load cycles, instability, environmental effects, etc.

Edit: The Pantheon is a bit of an exception since it has more slender elements and had to accommodate potentially large tensile hoop stresses. The tensile stresses do not develop because of thrust reactions provided by additional mass concrete. Furthermore this structure has obviously survived due to constant attention and retrofitting over the centuries.

 

[cranky108]

Actually the Pinto, if what I have heard is correct, was very safe, until the accountants started changing things.

I also assume on the Pinto, an engineer signed off on the changes.

The fact that no steel was used in Roman structures likely was why they lasted so long. Don't get me wrong, I like steel, but it has it's limitations, like causing foundations to explode when the steel is exposed to fault current.

 

[waross]

Ah, the Pinto. The Pinto's problem stemmed not from the fact that the fuel tank was in the same location as almost every North American car built at the time.
The problem was that a Ford exec wrote a memo querying if this was a safe location for a gas tank.
Also, the Pinto being a light front wheel drive vehicle, a car striking from the rear could more easily lift the rear of the Pinto and contact the gas tank.
Anecdote.
During the Pinto publicity years when any fire involving a Pinto was national news, there was a local wreck.
A young lady was stopped in the left turn lane at a traffic light waiting for the light to change.
A speeder could not stop a and to avoid hitting a string of cars, swerved into the turn lane and hit the young ladies car.
He was breaking heavily and his car nosed under the other car and hit the gas tank.
The young ladies body was identified from dental records.
But, not a Pinto, no National news, only a small mention on an interior page of the local paper.
Crown Victorias; Interestingly, if something hit a Crown Vic hard enough to lift the rear and impact the gas tank, the bolts on the back of the differential housing would often puncture the gas tank and a fire would often follow.
It didn't happen that often because it takes a lot to lift the rear of a Crown Victoria.
I understand that Crown Vics built as police interceptors had a hard plastic ring covering the bolt pattern on the back of the differential.
Every car that I owned prior to and during the Pinto years had the gas tank in the same place, underneath and just ahead of the rear bumper.
Trucks had the gas tank behind the seat. I drove a dump truck with a leak in the gas tank. I ran with the seat tank empty and made sure that I didn't run out on the saddle tank. There was no gauge on the saddle tank, normally when the saddle tank ran dry the seat tank was the come home supply. Common back then.
PS I owned two Pintos. One was a station wagon bought new for my wife. The other was bought second hand and was still running when I gave it away to a student for a shop project with over 230,000 miles on the clock.
One thing I noticed was that the hatch-back had somewhat of an aerodynamic profile and got very light in the back end at about 70 MPH.
I used to like driving fast but not in the Pinto.
Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[IRstuff]

The Pinto was supposedly missing a couple of bucks of hardware that would have made it substantially safer; that's what the accountants drove.

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[3DDave]

The Pinto was rear wheel drive with a solid rear axle. There was a bracket that needed a cover plate to prevent can-opening the tank. As part of the engineering cost evaluation of every part the cover plate was rejected.

"Upon impact, the filler neck would tear away from the sheet-metal tank and spill fuel beneath the car. The tank was also easily punctured by bolts protruding from the differential and nearby brackets. One report later described the entire contents of a tank leaking out in less than a minute after an accident. These problems combined to create a serious risk of fire, so engineering teams proposed solutions. One was to borrow a design Ford already used in its Capri, a tank that sat above the axle and out of the way. Another alternative was installing tank shields to prevent punctures, and reinforcements around the filler to prevent tearing."

https://www.popularmechanics.com/ca...e-engineering-failures-ford-pinto-fuel-tanks/

 

[waross]

I stand corrected.
Despite my misinformation the point that I was trying to make is brought up in the Popular Mechanics atricle.

Reports range from 27 to 180 deaths as a result of rear-impact-related fuel tank fires in the Pinto, but given the volume of more than 2.2 million vehicles sold, the death rate was not substantially different from that of vehicles by Ford's competitors. The far more damaging result for Ford was the PR disaster.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[TenPenny]

Don't forget this one: in the early 1970s, the gas tank on all pickups was INSIDE the cab, behind the seat. The rules changed, and all the manufacturers had to move the gas tank outside of the cab. GM decided that if you hung the gas tank under the body, OUTSIDE the frame rails, that would be a good place.

Unless, of course, the truck got t-boned, in which case the gas tank was instantly ruptured.

 

[thebard3]

Maybe someone should start a Pinto thread. I'd tell stories about my sister's Vega.

Brad Waybright

It's all okay as long as it's okay.

 

[SFCharlie]

Report: Experts knew of Italian bridge weakening months before collapse

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[drawoh]

Maybe someone should start a Pinto thread. I'd tell stories about my sister's Vega.

Where is GregLocock when we need him? He has quoted figures to the effect that the Ford Pinto was somewhat safer than average for a subcompact of the mid-seventies. In the classic Pinto accident, three girls were incinerated when they were rear-ended at high speed by a van with a reinforced front bumper.

--
JHG

 

[waross]

For over 20 years the standard location for the gas tank was behind the rear axle.
What was different about the Pinto?
1. Someone wrote a memo questioning the safety of that location.
2. Ford conducted a cost analysis and decided that it was cheaper to "Let it Burn."
3. The memo and the cost analysis became public and became evidence in a court case.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

Root cause analysis should identify one, and one cause only, why the structure failed.

As a career practitioner in metallurgical failure analysis, I have to disagree. For the simple component failures I investigate for chemical process industry and boilers it is indeed most often true, but I categorize this as a system failure, where a variety of technical experts are required for the investigation. I reserve the term 'forensic' for such complex system failures.

If I want to get philosophical about failure analysis, I could ultimately ascribe every root cause as 'human factors', but that would trivialize the exercise. However I don't think it is being philosophical to think that in this tragic case the conclusion applies literally, where political machinations, public funds, and designer hubris are implicated.

We need to let the investigators do their work, which will take some time and hopefully will not be compromised by the political blame game going on.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

Maybe someone should start a Pinto thread. I'd tell stories about my sister's Vega.

You refer to the Chevy Vega-matic and it's twin, the Pontiac Dis-Astra?

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

Also, the Pinto being a light front wheel drive vehicle, a car striking from the rear could more easily lift the rear of the Pinto and contact the gas tank.

The Pinto was rear-wheel drive. It was constructed on the large car model shrunk down: body bolted on a weighty frame. Very heavy.
An I am surprised to hear you reached 70mph in any finite amount of time. My 1973 Capri with the same 2.3L engine was completely gutless (though it got lots of looks).

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[Brad805]

More Pinto talk... time for a diff thread for those who are interested.