Speaking of bridges... check this out.

[DudleyGarrett]

I’m sure many of you know about and have seen this before, but for those of you haven’t… Check out this YouTube link. It’s the Tacoma Narrows bridge disaster of 1940. Someone here mentioned it here yesterday, and I remember seeing this footage when I was a kid on some documentary, but didn’t put them together until earlier today. Once the physics are explained, it makes a bit of sense, but it still looks freaky.

[DudleyGarrett]

Doh, wrong forum. Mods, can you please move this to MPSIMS? Thanks!

[DJ_Motorbike]

If one good thing comes out of this I hope that more people become aware of the Tacoma Narrows bridge disaster. It’s one of my favorite jokes when I do something stupid. For instance, breaking dishes while stacking them after drying - smooth it over by saying, “Now for my next project - the Tacoma Narrows bridge.” Nobody ever gets it.

[NinetyWt]

Dudley, my dad used to use this as an example of harmonic resonance in one of his Structures classes. I remember there being a question about it on one of the exams (reason I remember it is, I got it wrong ).

[Duke_of_Rat]

There was a dog in the car on the bridge. Somebody ran out to try to save it, but it bit at them and they left it there. It went down with the car.

[Troy_McClure_SF]

@DJ Motorbike

“Now for my next project - the Tacoma Narrows bridge.” Nobody ever gets it.

I’d probably howl at that, FWIW.

[DudleyGarrett]

@NinetyWt

Dudley, my dad used to use this as an example of harmonic resonance in one of his Structures classes. I remember there being a question about it on one of the exams (reason I remember it is, I got it wrong ).

What were the engineers thinking? It seems like such a massive blunder… of course, I say that with the huge advantage of hindsight.

[Czarcasm]

Moving thread from IMHO to MPSIMS.

[cochrane]

I saw a commercial for a car stereo (I think it was Pioneer) a few years ago. It showed the Tacoma Narrows bridge swaying while heavy metal music played. Then the music cuts off and a guy, presumably the stereo’s owner, is saying, “Sorry.”

I guess after 60 years any situation can become humorous.

[NinetyWt]

@DudleyGarrett

What were the engineers thinking? It seems like such a massive blunder… of course, I say that with the huge advantage of hindsight.

The cause of the failure is a bit complicated. From Wiki:

The event can only be understood while considering the coupled aerodynamic and structural system which requires rigorous mathematical analysis to reveal all the degrees of freedom of the particular structure and the set of design loads imposed.

With the earlier designs any wind would simply pass through the truss, but in the new design the wind would be diverted above and below the structure. Shortly after construction finished at the end of June (opened to traffic on July 1, 1940), it was discovered that the bridge would sway and buckle dangerously in relatively mild windy conditions for the area. This resonance was longitudinal, meaning the bridge buckled along its length, with the roadbed alternately raised and depressed in certain locations – one half of the central span would rise while the other lowered

.

This gave the bridge the nickname of Galloping Gertie.

The failure of the bridge occurred when a never-before-seen twisting mode occurred, from winds at a mild 40MPH. This is called a torsional, rather than longitudinal, mode (see also torque) whereby when the left side of the roadway went down, the right side would rise, and vice-versa, with the centerline of the road remaining still.

.

Much more in the article.

[GIGObuster]

Weird true story:

http://www.wsdot.wa.gov/TNBhistory/weirdfacts.htm#6

The effects of Galloping Gertie’s fall lasted long after the catastrophe. Clark Eldridge, who accepted some of the blame for the bridge’s failure, learned this first-hand. In late 1941 Eldridge was working for the U. S. Navy on Guam when World War II began. Soon, the Japanese captured Eldridge. He spent the remainder of the war (three years and nine months) in a prisoner of war camp in Japan. To his amazement, one day a Japanese officer, who had once been a student in America, recognized the bridge engineer. He walked up to Eldridge and said bluntly, “Tacoma Bridge!”

I think the Karma gods pushed too hard on this guy.