The Tacoma Narrows Bridge Collapse and How We Got It Wrong
motherboard.vice.com
motherboard.vice.com
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... [2] http://goldengatebridge.org/research/majggbimprove.php
Side question: Is there a good place to learn about major structural engineering fixes that were kept secret until the work was completed?
http://www.slate.com/blogs/the_eye/2014/04/17/the_citicorp_t...
An updated link to the New Yorker piece mentioned in the article is http://people.duke.edu/~hpgavin/cee421/citicorp1.htm
Or if you have a New Yorker subscription http://www.newyorker.com/magazine/1995/05/29/the-fifty-nine-...
I'd actually read the New Yorker article first, then read the more recent reporting.
edit: this is the same story mentioned by jonlucc in sibling comment.
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.
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.
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.
In all seriousness, this type of writing - sprawling as you call it - is important. It lets the reader come away with a sense of the nuances of the situation, instead of a bullet point abstract that leads to misunderstandings and overlooked issues. This type of writing - commonly called "the essay" - is important precisely because it does take time to read it. Its meant to teach you something, not just give you a little factoid you can regurgitate throughout the day.
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.
In general this rambling style is a complete turn-off for people who (1) aren't already familiar with the topic and (2) don't have 40 hours a week to spend reading. It boggles the mind how many supposedly tech-focused articles are pumped full of human interest fluff. For example, any article that starts with someone's physical description ("John Smith was hunched in front of his computer, his messy brown hair almost completely obscuring the screen.") is almost guaranteed to be of this ilk.
Then claim the fact that it rambles is proof of good writing.
Anyone else who has gone through the mechanics and disagrees with me on this, please let me know your thinking.
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!
The Bulge was well-known to eat cars: http://blog.seattlepi.com/bellevue-pi/2011/05/18/looking-bac...
Difference between earthquake insurance in Seattle and just over 100mi south is incredible(~1.5k/mo if I remember correctly).
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.