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My understanding is that the way buildings collapse in Hollywood is not how they collapse in reality. If the base of the structure begins to fail, it doesn't fa

My understanding is that the way buildings collapse in Hollywood is not how they collapse in reality. If the base of the structure begins to fail, it doesn't fall over as a tower, but crumbles into itself.

komali2 8y ago
The Twin Towers took out the blocks surrounding them. Literally they fell on top of other buildings, even though they "collapsed into themselves." I am very skeptical of anybody, no matter how experienced, that gets on the news and says "that'll never happen," regardless of what the "that" is. Has he considered a skilled terrorist cell lacing only the east side of Salesforce Tower with explosives?
- toss1 8y ago
  Even blowing out only one side of a tall tower, would not cause it to fall like timber. Instead, one of two things will happen. If there is low lateral strength (unlikely), the east side of the floors above will shear and collapse off, straight down into a pile on the east side. If there's good lateral strength, The forces formerly supported by the now blown east structures will largely fall on the adjacent structures around the building, overloading them, causing failure, and rapidly continuing around the supports in a zipper-failure, whereupon the above structures now unsupported again fall straight down with gravity's vector. Either way there's probably a bigger pile on the east side, but it's not like the top floor of a 1000' building will land 1000' laterally from the base. 100' would be a long way (tho there's be lots of flying debris for a good distance).
  - nerfhammer 8y ago
    Skyscrapers have a tremendous amount of mass and are engineered to resist the force of gravity. That's hard, so they only bother to engineer it so that it resists that force in one direction relative to the building. As soon as you might start to turn the building onto its side it falls apart like a sand castle. Were this not to happen the building would have to be engineered such that it could withstand being turned on its side like that without collapsing. But they don't design them as such.
- d0lph 8y ago
  Wouldn't there be bigger concerns, terrorist attacks really don't happen that often. It'd be like constantly worrying about protecting yourself from lightning.
  - komali2 8y ago
    You're right, but over the course of a building's lifespan, the "chance" is greater, right? So the chance of a terrorist attack against salesforce tower this year is less than the chance it might happen sometime in the next 30 years. I'm not good at statistics, though. Anyway, this is why we have a lot of earthquake preparedness, though the chance is 5% in the next 30 years. It's not a "constant worry," so much as a plan. There's non-negligible chance of terrorist attack, so they architect in such a way to prevent it being catastrophic. There's a non-negligible chance of your office catching fire, so they put green exit signs at the door. That sort of thing.
    - czep 8y ago
      > though the chance is 5% in the next 30 years. Not even close. USGS estimates over the next 30 years are: 72% probability of a M6.7 or higher 51% probability of a M7.0 or higher 20% probability of a M7.5 or higher Source: https://pubs.usgs.gov/fs/2016/3020/fs20163020.pdf https://pubs.usgs.gov/fs/2016/3020/fs20163020.pdf
      - tenken 8y ago
        And?? California building codes have improved alot since the 1980s or so. I remember the 1989 LA earthquake as I drove through the aftermath to visit my grandma about 2 weeks after, I live on the Central coast. All in all not since 1933 has CA lost more than 100 lives in an earthquake: https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_California https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_Calif... That tells me our building codes are pretty damn good. I work at ucsb and the catilina islands recently had a 5.2 about 2 weeks ago and the building shook abit. But all in all unless we suffer an 8.0+ I'm not terribly worried (knock on wood). To put that another way, realistically for any moderate sized earthquake CA is generally well prepared in terms of architecture, unless the big one hits ... In which case just kiss your butt goodbye. I do wish, even for the big one, that CA invested in an early warning system like Japan has ... Imagine a 5-50 seconds warning of an earthquake, that would save lives, not stricter building codes: https://youtu.be/OXXZouxPT7U https://youtu.be/OXXZouxPT7U Here is a better, live example of the early warning: https://youtu.be/n-FMpNBfna8 https://youtu.be/n-FMpNBfna8
- nostrademons 8y ago
  With the Twin Towers, the issue wasn't so much that they fell on top of other buildings (they didn't - you can see that on footage of them coming down), it's that when they hit the ground, the debris cloud billows out at high velocity and consists of projectiles that can structurally damage neighboring buildings. All that gravitational potential energy of the structure gets converted to kinetic energy as it collapses, and that kinetic energy is basically like a bomb going off at ground zero. When a bomb goes off near a building, the building is gonna have a bad time, even if it doesn't directly hit it.
  - jakeogh 8y ago
    http://s3.amazonaws.com/nasathermalimages/public/images/4158.jpg http://s3.amazonaws.com/nasathermalimages/public/images/4158... http://s3.amazonaws.com/nasathermalimages/public/images/fema_debris_distribution.jpg http://s3.amazonaws.com/nasathermalimages/public/images/fema... http://s3.amazonaws.com/nasathermalimages/public/images/5489.jpg http://s3.amazonaws.com/nasathermalimages/public/images/5489... http://s3.amazonaws.com/nasathermalimages/public/images/core3.jpg http://s3.amazonaws.com/nasathermalimages/public/images/core... http://s3.amazonaws.com/nasathermalimages/public/video/Relics_in_the_Rubble_Bent_Hbeam.wmv http://s3.amazonaws.com/nasathermalimages/public/video/Relic... http://nate.flach.s3.amazonaws.com/Abolhassan_Astaneh.avi http://nate.flach.s3.amazonaws.com/Abolhassan_Astaneh.avi
    - nostrademons 8y ago
      Like I said, it's like a bomb going off at ground zero. The pictures you link support that: notice how the damage is mostly near street level (from projectiles moving outwards from the crash site) rather than at the top of the building (from projectiles falling on the building).
      - jakeogh 8y ago
        I agree. https://web.archive.org/web/20021004010033/http://www.chiefengineer.org/article.cfm?seqnum1=1029 https://web.archive.org/web/20021004010033/http://www.chiefe... http://s3.amazonaws.com/nasathermalimages/public/images/Impact_1_and2.png http://s3.amazonaws.com/nasathermalimages/public/images/Impa...

komali2 8y ago

The Twin Towers took out the blocks surrounding them. Literally they fell on top of other buildings, even though they "collapsed into themselves." I am very skeptical of anybody, no matter how experienced, that gets on the news and says "that'll never happen," regardless of what the "that" is. Has he considered a skilled terrorist cell lacing only the east side of Salesforce Tower with explosives?

toss1 8y ago
Even blowing out only one side of a tall tower, would not cause it to fall like timber. Instead, one of two things will happen. If there is low lateral strength (unlikely), the east side of the floors above will shear and collapse off, straight down into a pile on the east side. If there's good lateral strength, The forces formerly supported by the now blown east structures will largely fall on the adjacent structures around the building, overloading them, causing failure, and rapidly continuing around the supports in a zipper-failure, whereupon the above structures now unsupported again fall straight down with gravity's vector. Either way there's probably a bigger pile on the east side, but it's not like the top floor of a 1000' building will land 1000' laterally from the base. 100' would be a long way (tho there's be lots of flying debris for a good distance).
- nerfhammer 8y ago
  Skyscrapers have a tremendous amount of mass and are engineered to resist the force of gravity. That's hard, so they only bother to engineer it so that it resists that force in one direction relative to the building. As soon as you might start to turn the building onto its side it falls apart like a sand castle. Were this not to happen the building would have to be engineered such that it could withstand being turned on its side like that without collapsing. But they don't design them as such.
d0lph 8y ago
Wouldn't there be bigger concerns, terrorist attacks really don't happen that often. It'd be like constantly worrying about protecting yourself from lightning.
- komali2 8y ago
  You're right, but over the course of a building's lifespan, the "chance" is greater, right? So the chance of a terrorist attack against salesforce tower this year is less than the chance it might happen sometime in the next 30 years. I'm not good at statistics, though. Anyway, this is why we have a lot of earthquake preparedness, though the chance is 5% in the next 30 years. It's not a "constant worry," so much as a plan. There's non-negligible chance of terrorist attack, so they architect in such a way to prevent it being catastrophic. There's a non-negligible chance of your office catching fire, so they put green exit signs at the door. That sort of thing.
  - czep 8y ago
    > though the chance is 5% in the next 30 years. Not even close. USGS estimates over the next 30 years are: 72% probability of a M6.7 or higher 51% probability of a M7.0 or higher 20% probability of a M7.5 or higher Source: https://pubs.usgs.gov/fs/2016/3020/fs20163020.pdf https://pubs.usgs.gov/fs/2016/3020/fs20163020.pdf
    - tenken 8y ago
      And?? California building codes have improved alot since the 1980s or so. I remember the 1989 LA earthquake as I drove through the aftermath to visit my grandma about 2 weeks after, I live on the Central coast. All in all not since 1933 has CA lost more than 100 lives in an earthquake: https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_California https://en.m.wikipedia.org/wiki/List_of_earthquakes_in_Calif... That tells me our building codes are pretty damn good. I work at ucsb and the catilina islands recently had a 5.2 about 2 weeks ago and the building shook abit. But all in all unless we suffer an 8.0+ I'm not terribly worried (knock on wood). To put that another way, realistically for any moderate sized earthquake CA is generally well prepared in terms of architecture, unless the big one hits ... In which case just kiss your butt goodbye. I do wish, even for the big one, that CA invested in an early warning system like Japan has ... Imagine a 5-50 seconds warning of an earthquake, that would save lives, not stricter building codes: https://youtu.be/OXXZouxPT7U https://youtu.be/OXXZouxPT7U Here is a better, live example of the early warning: https://youtu.be/n-FMpNBfna8 https://youtu.be/n-FMpNBfna8
nostrademons 8y ago
With the Twin Towers, the issue wasn't so much that they fell on top of other buildings (they didn't - you can see that on footage of them coming down), it's that when they hit the ground, the debris cloud billows out at high velocity and consists of projectiles that can structurally damage neighboring buildings. All that gravitational potential energy of the structure gets converted to kinetic energy as it collapses, and that kinetic energy is basically like a bomb going off at ground zero. When a bomb goes off near a building, the building is gonna have a bad time, even if it doesn't directly hit it.
- jakeogh 8y ago
  http://s3.amazonaws.com/nasathermalimages/public/images/4158.jpg http://s3.amazonaws.com/nasathermalimages/public/images/4158... http://s3.amazonaws.com/nasathermalimages/public/images/fema_debris_distribution.jpg http://s3.amazonaws.com/nasathermalimages/public/images/fema... http://s3.amazonaws.com/nasathermalimages/public/images/5489.jpg http://s3.amazonaws.com/nasathermalimages/public/images/5489... http://s3.amazonaws.com/nasathermalimages/public/images/core3.jpg http://s3.amazonaws.com/nasathermalimages/public/images/core... http://s3.amazonaws.com/nasathermalimages/public/video/Relics_in_the_Rubble_Bent_Hbeam.wmv http://s3.amazonaws.com/nasathermalimages/public/video/Relic... http://nate.flach.s3.amazonaws.com/Abolhassan_Astaneh.avi http://nate.flach.s3.amazonaws.com/Abolhassan_Astaneh.avi
  - nostrademons 8y ago
    Like I said, it's like a bomb going off at ground zero. The pictures you link support that: notice how the damage is mostly near street level (from projectiles moving outwards from the crash site) rather than at the top of the building (from projectiles falling on the building).
    - jakeogh 8y ago
      I agree. https://web.archive.org/web/20021004010033/http://www.chiefengineer.org/article.cfm?seqnum1=1029 https://web.archive.org/web/20021004010033/http://www.chiefe... http://s3.amazonaws.com/nasathermalimages/public/images/Impact_1_and2.png http://s3.amazonaws.com/nasathermalimages/public/images/Impa...