5 ms·

Your comment seems to echo that of another architect quoted in the article. Ron Klemencic, the chief executive of Magnusson Klemencic Associates, the company t

by whack 9y ago

Your comment seems to echo that of another architect quoted in the article. Ron Klemencic, the chief executive of Magnusson Klemencic Associates, the company that did the structural engineering for Salesforce Tower, says he agrees that water and sewage systems need higher strength requirements, but not high rises. “Buildings falling on top of other buildings — that’s not going to happen,” Mr. Klemencic said. They never explained why Klemencic's reasoning. Care to explain why "buildings falling on top of other buildings — that’s not going to happen"?

swampthinker 9y ago
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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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...
Merad 9y ago
Hollywood treats falling buildings like falling trees [1]. The building basically gets cut off at the base, then stays together as it falls to the side until it hits the ground. I'm no expert, but IRL I think any significant amount of lean would lead to massive structural failure in your average skyscraper. Once the structure starts to fail gravity is going pull the pieces straight down since nothing is pushing them to the side. It's certainly a danger to surrounding buildings (see the WTC) but vastly different from buildings falling over on their sides to crush their neighbors. 1: https://youtu.be/r0tgEYiTNd4 https://youtu.be/r0tgEYiTNd4 (0:35 and 0:45)
gibsonf1 9y ago
I don't agree with Klemencic on this - given a big enough earthquake with large enough building sway (imagine a tower being a vertical beam with the base fixed and the top swaying back and forth) the structure can fail such that the momentum of the building during maximum sway will either break the building and/or cause the building to impact other swaying buildings.
jpollock 9y ago
Simulation showing an actual building failure from the NZ Christchurch earthquake [1]. It collapsed in the Feb 2011 Christchurch earthquake, magnitude 6.2[2]. Once the building's supports fail, it drops rather than topples. [1] https://www.youtube.com/watch?v=TCJq_2-q34k https://www.youtube.com/watch?v=TCJq_2-q34k [2] https://en.wikipedia.org/wiki/2011_Christchurch_earthquake https://en.wikipedia.org/wiki/2011_Christchurch_earthquake
- berberous 9y ago
  That's a squat cube-like 5 story building. You're probably right, but that video alone doesn't convince me a skyscraper would necessarily fail in the same way.
  - jakeogh 9y ago
    It wouldn't. The are designed to withstand hurricanes. It takes extensive preweakening to bring one (or three) down.

by whack 9y ago

swampthinker 9y ago

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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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 9y 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...

Merad 9y ago

Hollywood treats falling buildings like falling trees [1]. The building basically gets cut off at the base, then stays together as it falls to the side until it hits the ground. I'm no expert, but IRL I think any significant amount of lean would lead to massive structural failure in your average skyscraper. Once the structure starts to fail gravity is going pull the pieces straight down since nothing is pushing them to the side. It's certainly a danger to surrounding buildings (see the WTC) but vastly different from buildings falling over on their sides to crush their neighbors. 1: https://youtu.be/r0tgEYiTNd4 https://youtu.be/r0tgEYiTNd4 (0:35 and 0:45)

gibsonf1 9y ago

I don't agree with Klemencic on this - given a big enough earthquake with large enough building sway (imagine a tower being a vertical beam with the base fixed and the top swaying back and forth) the structure can fail such that the momentum of the building during maximum sway will either break the building and/or cause the building to impact other swaying buildings.

jpollock 9y ago

Simulation showing an actual building failure from the NZ Christchurch earthquake [1]. It collapsed in the Feb 2011 Christchurch earthquake, magnitude 6.2[2]. Once the building's supports fail, it drops rather than topples. [1] https://www.youtube.com/watch?v=TCJq_2-q34k https://www.youtube.com/watch?v=TCJq_2-q34k [2] https://en.wikipedia.org/wiki/2011_Christchurch_earthquake https://en.wikipedia.org/wiki/2011_Christchurch_earthquake

berberous 9y ago
That's a squat cube-like 5 story building. You're probably right, but that video alone doesn't convince me a skyscraper would necessarily fail in the same way.
- jakeogh 9y ago
  It wouldn't. The are designed to withstand hurricanes. It takes extensive preweakening to bring one (or three) down.