
The Tacoma Narrows Bridge Collapse and How We Got It Wrong - sageabilly
http://motherboard.vice.com/read/the-myth-of-galloping-gertie
======
Animats
Despite the length of the article, the author has missed an important point -
the Golden Gate Bridge had the same problem. After the Tacoma Narrows Bridge,
the Golden Gate Bridge had the greatest length to width ratio of any
suspension bridge.

This was a major concern at the time, but wasn't publicized. It was dealt with
in 1951, by attaching huge stiffening trusses under the deck.[1][2] If you've
seen the underside of the Golden Gate Bridge, you've seen the trusses, which
are not original. Prior to that stiffening, the bridge would twist in high
winds, on one occasion enough that light poles hit the suspension cables.

[1]
[https://books.google.com/books?id=ug9YEcgBYs8C&pg=PA31&lpg=P...](https://books.google.com/books?id=ug9YEcgBYs8C&pg=PA31&lpg=PA31&dq=Golden+Gate+Bridge+oscillation+stiffening&source=bl&ots=WEu1VuT4-M&sig=0Rkgp-4CoCqkoDGO0pHrh1VDDPs&hl=en&sa=X&ved=0ahUKEwiz9_O3xtzJAhVEKGMKHT1RDx4Q6AEILDAD#v=onepage&q=Golden%20Gate%20Bridge%20oscillation%20stiffening&f=false)
[2]
[http://goldengatebridge.org/research/majggbimprove.php](http://goldengatebridge.org/research/majggbimprove.php)

~~~
stephengoodwin
> This was a major concern at the time, but wasn't publicized.

Side question: Is there a good place to learn about major structural
engineering fixes that were kept secret until the work was completed?

~~~
jonlucc
I don't have a comprehensive resource, but the other one that comes to mind is
covered in an episode of the "99% Invisible" podcast titled "Episode 110:
Structural Integrity".

[http://99percentinvisible.org/episode/structural-
integrity/](http://99percentinvisible.org/episode/structural-integrity/)

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danso
Wow, what a sprawling article. At first it seems to just focus on how the
popular physics class explanation of why the bridge collapsed was
wrong...which is mildly interesting but I was hoping from the title that we'd
get an indepth look at the engineering processes behind the bridge -- as I
remember hearing far more about the bridge in my engineering classes than in
physics. But the OP delivers some about the engineering, though I'm largely
ignorant of the details about the Tacoma Narrows Bridge (based on the film
footage, I had assumed it had happened in the 60s, because I didn't think
color footage would have been easy to take in the early 40s).

I liked this detail a third-way through:

> _To be fair to Moisseiff and his engineers, the phenomenon of aerodynamic
> instability wasn 't well understood at the time. But it wasn't completely
> unknown either. The last collapse of a suspension bridge due to its reaction
> to the wind occurred five decades earlier, when the Niagara-Clifton Bridge
> fell in 1889. (The heavyset design of the Brooklyn Bridge, which opened five
> years earlier, in 1883, was meant to withstand the sorts of forces that had
> affected suspension bridges in previous decades.)_

> _Just four months after Galloping Gertie collapsed, a professor of civil
> engineering at Columbia University, J. K. Finch, summarized suspension
> bridge failures in an article in Engineering News Record. "These long-
> forgotten difficulties with early suspension bridges, clearly show that
> while to modern engineers, the gyrations of the Tacoma bridge constituted
> something entirely new and strange, they were not new—they had simply been
> forgotten."_

The most recent example of a similar failure was 50 years earlier. No doubt
the information would propagate to some degree through engineering
libraries...but given how much we today forget about engineering failures and
case studies (in the software engineering context, some would argue that the
memory hole cycle seems to be about 6 months long) despite vastly improved
information pipelines, I've always wondered how difficult it was to learn and
maintain best practices in the engineering disciplines before the past few
decades.

~~~
CWuestefeld
_Wow, what a sprawling article. At first it seems_

Yes. I HATE reporting like this. I've got things to do with my life. I'd much
rather they just get on with the information. If they feel there's some human
interest necessary to understand the point, at least give me a summary up
front, so I can decide if it's going to be interesting and worth the
investment of time.

~~~
AnimalMuppet
There was a time when this was the way to write, to give depth to your
readers. The New Yorker is a classic example of this writing style. It's for
people who want to read, and have time to do it. Maybe 150 years ago, people
had more time than they had material to read, so this style was perfect.

But now there's so much more to read then there is time to read it in, and
this style is a royal pain. Times have changed, and (some) writers haven't
noticed. They're still writing like we have more time than we have stuff to
read.

~~~
ghaff
Yes, you're very important and don't have time to read long articles. If you
don't want to read long-form writing, then don't do so but don't complain
about it being available to people who like it. I rather like the New Yorker.

~~~
AnimalMuppet
It's not that "I'm very important". It's not even that I don't have time to
read a long article. I don't have time to read nearly as many long articles as
there are out there, though.

And to me, it feels like the shoe's on the other foot. To me, a long form
article is the _author_ deciding that he/she's so important (or the content
is) that I will find it worth the time to read the whole thing, and that it's
therefore fine to hide the main point somewhere in the length, because I'll
get the point so much better if I go through all the rest of it as well.
That's fine for those who like that kind of thing, but, well, let's just say
that it's unattractive to more and more readers as we have more and more
things that we want to read.

For it to be worth my while, this article has to be worth more than whatever I
didn't have time to read because I took the time to read this one. The longer
the article is, the higher that bar is, because the more I could have read
with the same time.

~~~
ghaff
I was unnecessarily snarky. However, this is a market-correcting thing. Yes,
there is a trend toward shorter pieces, which has pluses and minuses. If I
write long pieces that people don't read, I may shorten what I write. Or I may
not, if I feel the greater length is justified. And if some choose not to read
the longer piece, I'll probably be fine with that.

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sharkweek
Rest in peace, Tubby...

As are most Seattle natives, I'm waiting for 'the big one' to bring down our
other terrible bridge-ish thing, The Viaduct.

But this is probably all for nothing once they find Cthulu as the Bertha drill
starts moving again, only three years behind schedule on that one!

~~~
zw123456
The sinking of the old I90 Bridge was pretty spectacular as well.
[https://en.wikipedia.org/wiki/Lacey_V._Murrow_Memorial_Bridg...](https://en.wikipedia.org/wiki/Lacey_V._Murrow_Memorial_Bridge)
[https://www.youtube.com/watch?v=gm0YQ3vuyyY](https://www.youtube.com/watch?v=gm0YQ3vuyyY)
I think there was even a song written about it. All because some dummy left a
hatch open and it filled with water. Even more fascinating, I recall that when
divers went down to investigate they found a bunch of old cars at the bottom
and solved a bunch of missing persons cases. People apparently drove off of it
back when there was a turn around in the middle of it, which was later fixed
before the sinking, because so many people drove off the bridge.

~~~
bebop
Not to mention the Hood Canal bridge collapse. Washington really has had a
hard time with their bridges.
[https://en.wikipedia.org/wiki/Hood_Canal_Bridge](https://en.wikipedia.org/wiki/Hood_Canal_Bridge)

~~~
zw123456
That's right! Here in Washington we like to build cool bridges and then
destroy them :)

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mcnamaratw
Meh. Seems like a faux controversy. I looked into this a year ago when showing
off some simulation software, and read that as best anyone can tell, it was
probably flutter.*

In my reading I didn't run into anybody saying that the wind was fluctuating
at the natural frequency of the bridge! I also read that the "vortex street"
model for the failure had been proposed but discarded during the initial
investigation.

After my brief look into it, I got the idea that no serious workers have
believed those wrong ideas for many decades.

If some high school teachers somewhere say this was "resonance," that _is_
correct and probably worth teaching ... it's just not resonance at the natural
frequency of the bridge in still air.

*Flutter is pretty cool physics. Pinch one end of a a business card, then point the free end of the card into a fan. When the airspeed gets high enough, the card should oscillate like a clarinet reed. Torque from the airstream opposes the restoring torque that keeps the bridge (or business card) level. As the airspeed grows, the net restoring force drops towards zero and the resonant frequency falls. At zero you're toast, there's no net restoring force at all.

