5 ms·

The Tacoma Narrows Bridge Collapse and How We Got It Wrong

64 points by sageabilly 11y ago

sharkweek 11y ago
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 11y ago
  The sinking of the old I90 Bridge was pretty spectacular as well. https://en.wikipedia.org/wiki/Lacey_V._Murrow_Memorial_Bridge https://en.wikipedia.org/wiki/Lacey_V._Murrow_Memorial_Bridg... 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.
  - rconti 11y ago
    Yeah, I remember the sinking. That was crazy. The Bulge was well-known to eat cars: http://blog.seattlepi.com/bellevue-pi/2011/05/18/looking-back-on-the-floating-bridge/ http://blog.seattlepi.com/bellevue-pi/2011/05/18/looking-bac...
  - bebop 11y ago
    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 11y ago
      That's right! Here in Washington we like to build cool bridges and then destroy them :)
- vvanders 11y ago
  Really happy I moved out of the Seattle area. From what I understand most of Seattle-proper is built on sandstone and the fault line running through Seattle seems like a huge liability. Difference between earthquake insurance in Seattle and just over 100mi south is incredible(~1.5k/mo if I remember correctly).
- taurath 11y ago
  As a relatively recent Seattle transplant coming from California, WSDoT seems to be one of the worst transportation departments I've seen. The road quality, traffic and general propensity for disaster (in the form of Bertha, bridge collapses, deathtrap viaducts, and destroyed roadways along the mountains lately) seems much higher than I remember in California. Might just be the weather, but I'd love an explanation for why its been so bad.
  - zw123456 11y ago
    That is completely true, I have lived here my whole life and it has always been that way. It is weird, we can build airplanes, software and tons of other great things, but the whole transportation thing is just completely baffling to Seattle for some reason.
    - taurath 11y ago
      A friend of mine who's a civil engineer says its because the freeway exits are a mile apart rather than 1.5 miles, so that creates a lot of very short merges and ramps up traffic heavily. What really gets me is the travesty that is 405 between renton and bellevue, feels like it should be 5 lanes but its only 2 full-access lanes and there's a crash every 4 hours because of how much the road bends suddenly.
danso 11y ago
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 11y ago
  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.
Animats 11y ago
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=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 https://books.google.com/books?id=ug9YEcgBYs8C&pg=PA31&lpg=P... [2] http://goldengatebridge.org/research/majggbimprove.php http://goldengatebridge.org/research/majggbimprove.php
- stephengoodwin 11y ago
  > 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 11y ago
    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/
  - js2 11y ago
    Another one is the Citicorp tower in NYC: http://www.slate.com/blogs/the_eye/2014/04/17/the_citicorp_tower_design_flaw_that_could_have_wiped_out_the_skyscraper.html 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 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-story-crisis 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.
mcnamaratw 11y ago
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.

64 points by sageabilly 11y ago

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 11y ago
The sinking of the old I90 Bridge was pretty spectacular as well. https://en.wikipedia.org/wiki/Lacey_V._Murrow_Memorial_Bridge https://en.wikipedia.org/wiki/Lacey_V._Murrow_Memorial_Bridg... 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.
- rconti 11y ago
  Yeah, I remember the sinking. That was crazy. The Bulge was well-known to eat cars: http://blog.seattlepi.com/bellevue-pi/2011/05/18/looking-back-on-the-floating-bridge/ http://blog.seattlepi.com/bellevue-pi/2011/05/18/looking-bac...
- bebop 11y ago
  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 11y ago
    That's right! Here in Washington we like to build cool bridges and then destroy them :)
vvanders 11y ago
Really happy I moved out of the Seattle area. From what I understand most of Seattle-proper is built on sandstone and the fault line running through Seattle seems like a huge liability. Difference between earthquake insurance in Seattle and just over 100mi south is incredible(~1.5k/mo if I remember correctly).
taurath 11y ago
As a relatively recent Seattle transplant coming from California, WSDoT seems to be one of the worst transportation departments I've seen. The road quality, traffic and general propensity for disaster (in the form of Bertha, bridge collapses, deathtrap viaducts, and destroyed roadways along the mountains lately) seems much higher than I remember in California. Might just be the weather, but I'd love an explanation for why its been so bad.
- zw123456 11y ago
  That is completely true, I have lived here my whole life and it has always been that way. It is weird, we can build airplanes, software and tons of other great things, but the whole transportation thing is just completely baffling to Seattle for some reason.
  - taurath 11y ago
    A friend of mine who's a civil engineer says its because the freeway exits are a mile apart rather than 1.5 miles, so that creates a lot of very short merges and ramps up traffic heavily. What really gets me is the travesty that is 405 between renton and bellevue, feels like it should be 5 lanes but its only 2 full-access lanes and there's a crash every 4 hours because of how much the road bends suddenly.

danso 11y ago

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 11y ago
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.

Animats 11y ago

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=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 https://books.google.com/books?id=ug9YEcgBYs8C&pg=PA31&lpg=P... [2] http://goldengatebridge.org/research/majggbimprove.php http://goldengatebridge.org/research/majggbimprove.php

stephengoodwin 11y ago
> 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 11y ago
  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/
- js2 11y ago
  Another one is the Citicorp tower in NYC: http://www.slate.com/blogs/the_eye/2014/04/17/the_citicorp_tower_design_flaw_that_could_have_wiped_out_the_skyscraper.html 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 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-story-crisis 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.

mcnamaratw 11y ago

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.