[Cog]

According to the report it had big cracks in the concrete even before they moved it. Failure was inevitable. Bad mix or it was subject to load in some unexpected way during the pour.

[vtsnowedin]

That report doesn't draw any conclusions. It merely reports what testing has been done without spelling out any of the test results.
But yes the crack going all the way through member 11 tells the story. That piece of the truss along with slanted member 2 carried the most stress on a square inch of cross section of any part of the bridge and would have been in compression at all times. That it cracked through shows it wasn't large enough to take the load without the final cable stays being in place to share it. The bridge should never have left the drawing board much less the casting yard.

[jedrider]

Just as an aside. I have no background in engineering. However, I do like form follows function.

If a bridge does NOT look like it will stand up on it's own, I plain and simply DO NOT like it.

[Cog]

The important thing was it was designed by a female engineering team. Who cares if it failed as long as diversity was achieved?

[vtsnowedin]

I'd have to dig out forty year old statics text books to do it but one thing they will probably do is compute the stresses as it was being moved with the supports under the junction of 3&4 and under 9&10. That is a whole different result from when it was sitting on it's piers supported under 1 and 12. The weight of the section between 10, and 12 may have put diagonal member 11 into tension. Why it didn't also make member 2 crack at the same time I can't see as of yet.

[jedrider]

Another example of a bridge that doesn't look like it can support itself except under very benign conditions:

Italy bridge collapse in Genoa leaves at least 35 dead, cars trapped ...
https://weather.com/news/news/2018-08-14-genoa-italy-bridge-collapse

weather.com has the best pic on it's front page though.

For all the might of our civilization, we are obviously living on borrowed time where you can find so many examples of decaying and inadequate infrastructure for it's purpose.

[Cog]

Did the Italian bridge have yearly structural inspections? You can't simply erect a bridge and do no inspections or maintenance on it. The bridge was built in 1967 which puts it at 51 years old.

[vtsnowedin]

Bridges of that class get inspected on a very frequent basis. That it served for fifty one years indicates the design was a good one and they will be looking for deterioration (rust or fatigue cracking) that was not visible to inspectors. It could of course be some built in flaw that was just waiting to happen but if I had to bet the rent on it I would bet on hidden rust etc.

[dolanbaker]

A large number of bridges in the UK have been replaced in recent years due to "concrete cancer", caused by internal rebar rusting away, so that does sound like the most likely candidate.

There was also some work going on reinforcing the foundations, so something could have sifted enough to separate the deck, causing it to fall and drag the rest down with it, but I believe it was rust!

[jedrider]

Nice overview of Morandi Bridge disaster:

Italy bridge: Grief and anger over collapse in Genoa
https://www.bbc.com/news/world-europe-45193614

[jedrider]

A better overview which confirms my suspicions:

Italy Bridge Was Known to Be in Trouble Long Before Collapse
https://www.nytimes.com/2018/08/15/world/europe/italy-genoa-bridge-collapse.html?hp&action=click&pgtype=Homepage&clickSource=story-heading&module=first-column-region&region=top-news&WT.nav=top-news

When that bridge was built, it was the beginning of Modernism and Minimalism in Architecture. Unfortunately, that has repercussions.

I remember the New York World Trade towers going up about that time. They were beautiful buildings from a distance and quite imposing from Street Level, too, but that was about all, I mean it was nothing special on the inside. That was very clever that they could make it collapse straight down.

The Verrazano-Narrows Bridge went up at that time, too. Quite ugly, but at least they choose a good model to base it upon, i.e. the Golden Gate bridge of San Francisco.

[jedrider]

Another article that is more recent telling the selection and engineering story behind the FIU pedestrian bridge.

FIU had grand plans for 'signature' bridge. But the design had a key mistake
https://www.miamiherald.com/news/local/community/miami-dade/article212571434.html

$this->bbcode_second_pass_quote('', 'T')he unconventional placement of diagonal supports in an uneven zig-zag pattern along the bridge produced a complex structural web with a glaring weakness at a key connection point, apparently overlooked by designers at FIGG Bridge Group, say three independent structural engineers who reviewed nearly 2,000 pages of calculations for the bridge at the Miami Herald's request.

[dolanbaker]

Incredibly stupid to build a bridge that looks like a suspension bridge and not actually build a suspension bridge!

[vtsnowedin]

$this->bbcode_second_pass_quote('dolanbaker', 'I')ncredibly stupid to build a bridge that looks like a suspension bridge and not actually build a suspension bridge!

[jedrider]

Single point of failure Bridge Designs:

Genoa Bridge Collapse: Road to Trajedy
https://www.nytimes.com/interactive/2018/09/06/world/europe/genoa-italy-bridge.html?action=click&module=Top%20Stories&pgtype=Homepage

$this->bbcode_second_pass_quote('', 'B')ut Mr. Morandi also believed that the concrete coating would protect the steel cables inside from the wear and tear of the elements.

“Concrete structures seemed to be eternal,” Mr. Majowiecki said. “This was the mentality.”

In that hope, he added, Mr. Morandi was greatly mistaken.

The concrete of the day turned out to be highly vulnerable to degradation, worsened perhaps by salty air from the Mediterranean Sea and the harsh fumes from nearby factories.

Cracks in the concrete shell let water in, and the steel began corroding almost as soon as the bridge was opened for traffic in 1967. But unlike bare cables, any corrosion was hidden deep inside, making it hard to detect.

[Newfie]

And expensive to fix, or replace.

[dolanbaker]

$this->bbcode_second_pass_quote('jedrider', 'S')ingle point of failure Bridge Designs:

Genoa Bridge Collapse: Road to Trajedy
https://www.nytimes.com/interactive/2018/09/06/world/europe/genoa-italy-bridge.html?action=click&module=Top%20Stories&pgtype=Homepage

$this->bbcode_second_pass_quote('', 'B')ut Mr. Morandi also believed that the concrete coating would protect the steel cables inside from the wear and tear of the elements.

“Concrete structures seemed to be eternal,” Mr. Majowiecki said. “This was the mentality.”

In that hope, he added, Mr. Morandi was greatly mistaken.

The concrete of the day turned out to be highly vulnerable to degradation, worsened perhaps by salty air from the Mediterranean Sea and the harsh fumes from nearby factories.

Cracks in the concrete shell let water in, and the steel began corroding almost as soon as the bridge was opened for traffic in 1967. But unlike bare cables, any corrosion was hidden deep inside, making it hard to detect.

[Newfie]

That’s just insane.

[vtsnowedin]

Somebody got a prize and several promotions for designing that intersection.

[Newfie]

Yeah, really. If you look real close you can see they are all driving backwards!