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Obligatory bridge collapse fact: there have been a few historical bridge collapses resulting from walking/stepping/marching which causes vibrations in the bridg

Obligatory bridge collapse fact: there have been a few historical bridge collapses resulting from walking/stepping/marching which causes vibrations in the bridge that create a feed back loop further syncing the stepping intensifying the vibrations ultimately leading to the failure. Soldiers are supposed to break stride when crossing bridges to prevent collapse. Some people have a fear of the heights of these bridges, I have an irrational fear of vibrational collapse.

pyuser583 5y ago
Back in the 80s the city of SF encouraged people to walk in the GG Bridge to celebrate its 50th anniversary. Almost destroyed the bridge and killed everyone on it.
- throwaway_kufu 5y ago
  I feel like I remember that, but might be confusing it with another bridge incident. I remember there being elephants in the celebration, significant “waves” in the bridge and some pretty serious injuries...but again I may be confusing it with another incident. Edit: watched video, GG flattened out. Not sure what I am remembering and maybe mixing up a few bridge “disasters” and collapses into one.
- brabel 5y ago
  I looked it up and it seems that's not what happened. _While there were some injuries, there were no fatalities and the bridge was not damaged._ _The weight of the 300,000 people flattened the normally arched roadbed, although bridge engineers later said there was never any real danger._ Source: https://www.sfgate.com/local-donotuse/article/Golden-Gate-bridge-walk-1987-anniversary-disaster-13896571.php#taboola-7 https://www.sfgate.com/local-donotuse/article/Golden-Gate-br...
  - redis_mlc 5y ago
    > The weight of the 300,000 people I live down the street from the GG ... Why would you risk the lives of 300,000 people on a single ancient bridge near salt water? That's insane.
kens 5y ago
I read the same claim on Usenet about 30 years ago and researched it. My conclusion was that soldiers break stride to avoid nasty oscillations, but I couldn't find any actual collapses. There was one bridge that was claimed as a collapse from people marching on it, but it was actually very high winds that caused the collapse.
- LeoPanthera 5y ago
  Well, London's Millennium Bridge did not collapse, but it did sway alarmingly when crowds of people walking on it were forced into resonance, resulting in the immediate closure of the bridge before it could be fixed. https://en.wikipedia.org/wiki/Millennium_Bridge,_London#Resonance https://en.wikipedia.org/wiki/Millennium_Bridge,_London#Reso...
  - cameronh90 5y ago
    And even now people still call it the “wobbly bridge”.
- deleted 5y ago
  [deleted]
- juhatl 5y ago
  Apparently an incident took place in 1831 where a bridge collapsed under soldiers marching, but the Wikipedia article [1] notes that "The conclusion of the investigation was that the vibration caused by the marching precipitated the bolt's failure, but it would have failed eventually anyway". There's more interesting information on synchronization and bridges on Veritasium's video, The Secret of Synchronization [2]. [1] https://en.wikipedia.org/wiki/Broughton_Suspension_Bridge https://en.wikipedia.org/wiki/Broughton_Suspension_Bridge [2] https://www.youtube.com/watch?v=t-_VPRCtiUg https://www.youtube.com/watch?v=t-_VPRCtiUg
  - pomian 5y ago
    That video link about synchronisation is very interesting. Thankyou. Synchronization of bridges, hearts, lightning bugs, metronomes, sailing clocks. Cool

pyuser583 5y ago

Back in the 80s the city of SF encouraged people to walk in the GG Bridge to celebrate its 50th anniversary. Almost destroyed the bridge and killed everyone on it.

throwaway_kufu 5y ago
I feel like I remember that, but might be confusing it with another bridge incident. I remember there being elephants in the celebration, significant “waves” in the bridge and some pretty serious injuries...but again I may be confusing it with another incident. Edit: watched video, GG flattened out. Not sure what I am remembering and maybe mixing up a few bridge “disasters” and collapses into one.
brabel 5y ago
I looked it up and it seems that's not what happened. _While there were some injuries, there were no fatalities and the bridge was not damaged._ _The weight of the 300,000 people flattened the normally arched roadbed, although bridge engineers later said there was never any real danger._ Source: https://www.sfgate.com/local-donotuse/article/Golden-Gate-bridge-walk-1987-anniversary-disaster-13896571.php#taboola-7 https://www.sfgate.com/local-donotuse/article/Golden-Gate-br...
- redis_mlc 5y ago
  > The weight of the 300,000 people I live down the street from the GG ... Why would you risk the lives of 300,000 people on a single ancient bridge near salt water? That's insane.

kens 5y ago

I read the same claim on Usenet about 30 years ago and researched it. My conclusion was that soldiers break stride to avoid nasty oscillations, but I couldn't find any actual collapses. There was one bridge that was claimed as a collapse from people marching on it, but it was actually very high winds that caused the collapse.

LeoPanthera 5y ago
Well, London's Millennium Bridge did not collapse, but it did sway alarmingly when crowds of people walking on it were forced into resonance, resulting in the immediate closure of the bridge before it could be fixed. https://en.wikipedia.org/wiki/Millennium_Bridge,_London#Resonance https://en.wikipedia.org/wiki/Millennium_Bridge,_London#Reso...
- cameronh90 5y ago
  And even now people still call it the “wobbly bridge”.
deleted 5y ago
[deleted]
juhatl 5y ago
Apparently an incident took place in 1831 where a bridge collapsed under soldiers marching, but the Wikipedia article [1] notes that "The conclusion of the investigation was that the vibration caused by the marching precipitated the bolt's failure, but it would have failed eventually anyway". There's more interesting information on synchronization and bridges on Veritasium's video, The Secret of Synchronization [2]. [1] https://en.wikipedia.org/wiki/Broughton_Suspension_Bridge https://en.wikipedia.org/wiki/Broughton_Suspension_Bridge [2] https://www.youtube.com/watch?v=t-_VPRCtiUg https://www.youtube.com/watch?v=t-_VPRCtiUg
- pomian 5y ago
  That video link about synchronisation is very interesting. Thankyou. Synchronization of bridges, hearts, lightning bugs, metronomes, sailing clocks. Cool