
Pedestrian Bridge Collapse over SW 8th Street in Miami [pdf] - wallflower
https://www.ntsb.gov/news/events/Documents/2019-HWY18MH009-BMG-abstract.pdf
======
harshreality
What went wrong technically to cause the bridge collapse is only the second
half of the story.

The first half of the story is that the stakeholders wanted an over-the-top
bridge design, complete with fake cable stays, and out of hubris decided they
would use an all-concrete single-truss Accelerated Bridge Construction (ABC)
design because all-concrete would look better and the university's (FIU's)
engineering department sort of specialized in promoting ABC.

What could have been a much cheaper nice looking normally-designed bridge
(which would be open today) ballooned (or you could say, was hijacked) into a
$10mm+ bridge disaster that would be comedy if people hadn't been hurt and
killed. A majority of it was even paid for by federal grants.[1]

This is why we can't have nice things. They were so focused on building a nice
looking bridge — and meeting deadlines — that they didn't/couldn't allocate
sufficient resources to verify the design, verify it was built and moved into
place correctly.

[1] see page 9 of
[https://www.transportation.gov/sites/dot.gov/files/docs/brie...](https://www.transportation.gov/sites/dot.gov/files/docs/briefing-
room/306576/amendment-2-ga-tiger-v-fiu.pdf)

~~~
juliusmusseau
> stakeholders wanted an over-the-top bridge design [...]

Nothing wrong with that!

> They were so focused on building a nice looking bridge — and meeting
> deadlines

These are also good things.

To me sounds like the civil engineers started behaving more like software
engineers. The independent peer reviewer they hired was not qualified to do
the review.

> Louis Berger was not qualified by the Florida Department of Transportation
> to conduct an independent peer review and failed to perform an adequate
> review of the FIGG Bridge Engineers design plans and to recognize the
> significant under-design of the steel reinforcement within the 11/12 node,
> which was unable to resist the horizontal shear between diagonal 11 and the
> bridge deck.

This whole business of the engineers ignoring the cracks that the contractors
kept needing reassurance about is also insane.

~~~
varjag
> To me sounds like the civil engineers started behaving more like software
> engineers.

Things like these were common in construction before software engineering was
a thing. It always makes me chuckle when someone defers to "if we built
buildings like we build software" trope. We do, and worse.

Lots of constructions standing around the world are not up to the codes in
zillion different ways. They are still standing because redundant nature of
physical construction is more forgiving than execution on a Turing machine.

~~~
paganel
> Things like these were common in construction before software engineering
> was a thing

I read in an architect's memoirs that when he was a student back in the 1940s
whenever his Architecture faculty teacher and his students visited a
construction site to maybe change some small details (or at least they were
perceived as "small" by said architects) oftentimes they were met with very
angry construction site workers who would make the above architects think
again about trying to force the implementation of those small changes. A
similar story was told to me by my father (also a civil engineer) as happening
in the 1980s, though the level of implied violence coming from the
construction workers was a little more subdued. Wish that we in the software
industry would be like those construction workers from time to time.

~~~
InitialLastName
You have the metaphor wrong. You're the software engineer. Your toolset is the
angry (or not) construction worker. Build a toolset that yells at you when you
want to do something stupid/dangerous.

~~~
Accujack
Interestingly, the mindset of the people who develop software toolsets (and
operating systems like Unix) is exactly the opposite.

------
fernly
> The construction and inspection firms working on the bridge were aware of
> the cracks and reported the cracks to the design firm, asking for guidance.
> The engineer of record at the design firm repeatedly indicated that the
> cracks were of no safety concern.

Welp, that's a lawsuit laid out cold right there, setting aside even the fact
that

> the probable cause of the ... bridge collapse was the load and capacity
> calculation errors made by FIGG Bridge Engineers, Inc.

~~~
userbinator
_The engineer of record at the design firm repeatedly indicated that the
cracks were of no safety concern._

I've heard many other examples of viciously denying that anything is wrong,
all the way until something becomes very _very_ wrong, to wonder whether this
is an inherent part of human nature or a futile effort to avoid liability for
knowingly screwing it up.

~~~
hazeii
It's called 'the Normalisation of Deviancy' e.g. [0]; there's quite a lot of
recent literature about it. Basically a risk is taken and nothing goes wrong;
as a result the risk gets repeated more and more often with less and less
concern until things do actually go wrong.

[0] [https://www.flightsafetyaustralia.com/2017/05/safety-in-
mind...](https://www.flightsafetyaustralia.com/2017/05/safety-in-mind-
normalisation-of-deviance/)

~~~
hazeii
Also here's a great article with a couple of examples (think this was
discussed here a while back):-

[https://fastjetperformance.com/podcasts/how-i-almost-
destroy...](https://fastjetperformance.com/podcasts/how-i-almost-
destroyed-a-50-million-war-plane-when-display-flying-goes-wrong-and-the-
normalisation-of-deviance/)

------
cdibona
NTSB Youtube report:

[https://www.youtube.com/watch?v=hBjntrebxj8](https://www.youtube.com/watch?v=hBjntrebxj8)

The ntsb and us chemical safety board channels are amazing.

[https://www.youtube.com/user/USCSB](https://www.youtube.com/user/USCSB)

~~~
lqet
I don't get this. There were large, steadily growing cracks in supporting
elements, observed and documented over multiple days. Why on earth wasn't the
street closed down?

The bridge slowly and visibly announced its impending collapse, which - as I
understand it - is exactly what engineers want. The thing nobody wants is a
bridge like the Morandi bridge in Genua, where the signs of impending collapse
were hidden under thick layers of concrete, until the structure suddenly and
unexpectedly gave way.

~~~
jaclaz
> ... hidden under thick layers of concrete ...

... and (only for the record) behind false or falsified inspection reports.

[https://www.corriere.it/english/19_gennaio_31/reports-on-
mot...](https://www.corriere.it/english/19_gennaio_31/reports-on-motorway-
bridges-at-risk-suspected-of-being-toned-
down-c35d1c84-2574-11e9-9fef-1e7c69c121a7.shtml)

------
imglorp
Third party analysis from AvE last year. Usually NSFW language.

[https://www.youtube.com/watch?v=KtiTm2dKLgU&app=desktop](https://www.youtube.com/watch?v=KtiTm2dKLgU&app=desktop)

~~~
exabrial
Usually? ::slaps kneee:: this our beloved redneck from canuckistan. :)
Demonetized seems to be the norm

~~~
linsomniac
Top comment on the linked video: Although the content is very interesting i'm
actually here for the foul language.

------
Animats
A fake cable-stayed 175-foot span pedestrian bridge for $9 million.

For less money, they could have had a real cable-stayed bridge, like the one
over I-280 near Apple HQ.[1] That cost $14 million, but it's a 375-foot clear
span over the freeway.

[1] [https://en.wikipedia.org/wiki/Don_Burnett_Bicycle-
Pedestrian...](https://en.wikipedia.org/wiki/Don_Burnett_Bicycle-
Pedestrian_Bridge)

~~~
stevenwoo
iirc all the bids for a concrete version (ala Florida) were twice as much for
the steel design that was used, otoh California version also has to be
earthquake resistant. I gotta give credit to all the engineering firms and
Caltrans oversight. Very little downtime on 280, that would have been a
traffic nightmare for entire peninsula.

~~~
OrangeMango
$14 million for 375 feet in CA is ~$37k/ft

A 620 ft concrete suspension bridge [1] in Chicago was $23 million, or
~$37k/ft

A 1470 ft concrete and steel bridge [2] in Chicago was $33 million, or
~$22k/ft

This ugly monstrosity in Florida was $9 million for 174 feet, or ~$51k/ft

It's awfully pathetic.

[1] [https://www.exp.com/project/35th-street-pedestrian-
bridge/](https://www.exp.com/project/35th-street-pedestrian-bridge/)

[2] [https://chicagocrusader.com/new-41st-street-pedestrian-
bridg...](https://chicagocrusader.com/new-41st-street-pedestrian-bridge-in-
bronzeville-opens/)

------
dba7dba
And then there's this accidental destruction of the phone of the engineer who
stamped the plans for the bridge.

"Denney Pate, who stamped the plans for the bridge, told a judge June 12 that
his wife accidentally put his pants with the phone in the pocket into a
washing machine, inflicting damage that destroyed any call records or images."

[https://www.enr.com/articles/47108-bridge-designer-
testifies...](https://www.enr.com/articles/47108-bridge-designer-testifies-on-
evidence-one-day-after-osha-slams-figg)

~~~
solotronics
I am surprised they can't subpeona the phone company for these records.

------
baggy_trough
To FIGG Bridge Engineers, Inc.:

10\. Train your staff on the proper use of Pc (the permanent net compressive
force normal to the shear plane) when calculating nominal interface shear
resistance.

Pretty humiliating. I wonder how bad the damage is to FIGG.

~~~
slenk
I bet they change their name after the story, like the new Magnum did (from
NYT article)

~~~
pnako
They can always rebrand as FIGG Demolition.

I get that mistakes do happen but this was a bloody footbridge...

~~~
paranoidrobot
I know this is a joke, but Engineering skill is just as important in safely
deconstructing something, as it is in constructing it.

------
AmpsterMan
I lived on the corner of 7th Terrace and 109th AVE during my senior year. I
could see the bridge being built from my bedroom window; I would cross 8th
Street to go to school everyday.

The bridge collapsing was one of the most surreal experiences of my life.

------
yay_cloud2
It sometimes fascinates me (and scares the shit out of me) to wonder at all of
the little errors/assumptions like this that are baked into the millions of
spreadsheets that form the foundation of so much of what we build and do in
the world.

~~~
wging
Dead comment reply by 'FakeComments' that I am not sure deserves to be dead
(what happened there?): "I’d say the better part of engineering is knowing how
to design in the face of small errors creeping into the project."

------
js2
NYT coverage:

[https://www.nytimes.com/2019/10/22/us/bridge-collapse-
florid...](https://www.nytimes.com/2019/10/22/us/bridge-collapse-florida-
international-university-NTSB.html)

------
alexhutcheson
The Miami Herald has done some great reporting on this:
[https://www.miamiherald.com/news/local/community/miami-
dade/...](https://www.miamiherald.com/news/local/community/miami-
dade/article236250848.html)

------
jorblumesea
Is anyone going to review their other bridge designs? Wonder what else they
missed.

~~~
abduhl
FIGG is one of the premier bridge designers in the country. You can probably
get on one of their bridges within a couple hours no matter where you live.

------
userbinator
If I'm reading the report correctly, the bridge was barely sufficient to
support its own weight, which is extremely surprising since I remember reading
a _very_ long time ago that bridges and other structures are designed to be
10x stronger than they normally need to be; a vague reference in the article
[https://en.wikipedia.org/wiki/Factor_of_safety](https://en.wikipedia.org/wiki/Factor_of_safety)
supports that. It seems like this bridge was designed for minimal cost...

~~~
sitharus
This is totally hearsay, but I've heard from multiple older engineers that as
computer models have been improved over time the safety factor has been
reduced as we have more accurate simulations. If the safety factors from the
'50s had been used it's possible this bridge would never have been designed
the way it was.

~~~
dredmorbius
I've noticed from videos of recent bridge failures (FIU and the Taiwain Arch
Bridge collapse a few weeks ago) how _fast_ the failures occur. Contrast with,
say, the Tacoma Narrows bridge failure in the 1940s.

I suspect current designs are far nearer critical tolerances. Even under the
ridiculous dynamics of the Tacoma Narrows incident, ultimate failure took
hours.

~~~
userbinator
_Even under the ridiculous dynamics of the Tacoma Narrows incident, ultimate
failure took hours._

It took 4 months from construction to failure, during which time it was
already flexing far more than normal.

~~~
dredmorbius
The FIU and Taiwan's Nanfang'ao Bridge collapse
([https://en.wikipedia.org/wiki/Nanfang%27ao_Bridge](https://en.wikipedia.org/wiki/Nanfang%27ao_Bridge))
each precipitated in seconds.

Contrast Tacoma Narrows, whose final throes were long enough for crowds to
form and traffic to be cleared.

Tacoma:

[https://youtube.com/watch?v=mXTSnZgrfxM](https://youtube.com/watch?v=mXTSnZgrfxM)

FIU:

[https://youtube.com/watch?v=BSq8295GFk4](https://youtube.com/watch?v=BSq8295GFk4)

Nanfang'ao:

[https://youtube.com/watch?v=mjsZbbG5fag](https://youtube.com/watch?v=mjsZbbG5fag)

Morandi, Genoa, Italy:

[https://youtube.com/watch?v=_gEMep8xLHk](https://youtube.com/watch?v=_gEMep8xLHk)

I-35W, Minneapolis, MN:

[https://youtube.com/watch?v=74JNl5n-YdI](https://youtube.com/watch?v=74JNl5n-YdI)

------
eesmith
"This is a synopsis from the NTSB’s report" about the FIU collapse from March
15, 2018, and not a new collapse, which is what I feared.

~~~
bewaretheirs
Based on file type alone I assumed it was some sort of formal report rather
than a press release and therefore not breaking news.

------
yumario
I study at FIU... I just don't see the point this bridge. Why would you spend
10+ million dollars on a bridge to cross a street, when the same problem can
be solved by a simple crosswalk? We already have one of these bridges... and
the majority of people don't bother to use it and simple take the cross walk.
It just such a waste of money.

~~~
Mountain_Skies
The federal government was picking up most of the cost. It's much easier to be
wasteful when it comes out of someone else's budget.

~~~
baud147258
And when it also supports your claim of being at the bleeding edge of bridge
construction.

------
campfireveteran
Recent NTSB video:

[https://youtu.be/hBjntrebxj8](https://youtu.be/hBjntrebxj8)

------
scarejunba
So much for the much vaunted "Professional Engineers".

~~~
abduhl
As I’ve posted before, there’s nothing special about a guy with a PE other
than him hanging out there with liability for the lawsuit.

Someone with a PE license has met the minimum requirements from the state.
Nothing else can be garnered from someone possessing a license. The minimum
requirements have, historically, resulted in engineers who put out public
facing designs that, more often than not, do not bring harm to the public. I
can tell you first hand that sometimes the guy with a license who is actually
at “the minimum” does not always put out something that is safe.

~~~
slavik81
Indeed. You can browse through the disciplinary actions taken against
engineers by professional associations and you will find all sorts of
incompetence and malfeasance. I find the discipline tends to be on the lenient
side—lots of fines, suspensions and reexaminations with only the occasional
permanent loss of license.

Still, I'm glad professional licensure is required. That's what will prevent
these folks from quietly rebranding and designing another disasterous bridge
tomorrow.

------
natch
The engineering firm mentioned as responsible in the report hosts their web
site without using https:

[http://www.figgbridge.com](http://www.figgbridge.com)

Why am I not surprised?

~~~
ars
Why exactly should they care? Is there something secret on their site? A login
form perhaps?

~~~
natch
They should care because https is not just about protecting secrets. Thinking
that is the case is a common misconception about https. Among other things
having https also makes it harder for a bad actor to deliver false content
while intercepting requests to the site.

~~~
corebit
And pointlessly makes it harder to deliver true content in the first place.

Not everything needs to be HTTPS.

