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As an architect in San Francisco, I would definitely prefer to be in a modern high rise here over other buildings for safety purposes during an earthquake. I a
by gibsonf1 9y ago
As an architect in San Francisco, I would definitely prefer to be in a modern high rise here over other buildings for safety purposes during an earthquake. I am highly skeptical of this article as I have in depth knowledge of seismic engineering, the building code and the updates after every earthquake around the world to the code and engineering practices.
The leaning building across from my office, for example, has nothing to do with seismic issues but basic design/engineering/construction flaws in not extending the pile footings deep enough to solid ground as others in the area have such as the new Salesforce tower.
- progers7 9y agoAre design parameters such as pile depth part of the public record? Is there a way to lookup the design of a building?
- ggcdn 9y agoMost cities keep a set of permit drawings, but generally you need to have a proximate relationship to the building to get access to them
- ItsMe000001 9y ago> The leaning building across from my office, for example, has nothing to do with seismic issues Nowhere in the article did anybody make such a claim. It was to illustrate the general problems of building in that area even without an earth quake, which leads me to the other point, what IMO is the main issue, and I think is pretty independent of how much effort is spent on any one building: The potential for soil liquefaction. They included several maps showing that many of the tallest buildings are built pretty much exactly over ground that might suffer that fate in a big earth quake. How would any individual design help? Compared to the alternative of not building the tallest structures right over those spots. The maps also showed plenty of more solid ground, but that is where there are mostly lower buildings. I would like to hear your opinion on that issue. As for your doubts on the entire article, it seems to me they asked quite a few specialists? Are they all mistaken? Well, I certainly would like you to be right, I used to live in SF and I still love the entire greater Bay Area.
- abduhl 9y agoLiquefaction mitigation is possible (ground replacement cells, compaction grouting, etc). It costs a lot and the only place that we (my company) have done true liquefaction mitigation is on large state funded jobs. The preferred alternative for the Bay Area is to sink foundations through liquefiable soils, discounting any strength from these soils, and rely on empirical studies that have found that liquefaction does not necessary result in loss of confinement which would induce buckling failures in the piles. I share the GP's doubts on the article. The practicing specialists they talked to certainly don't think there's a gamble: they actively pursue and design sky scrapers in the City. I think their words are being misused in a way that makes them seem like they agree with the article's premise.
- pfarnsworth 9y agoIf the earthquake were large enough, could the Millenium Tower completely fall over? Or is it only destined to keep leaning?
- gibsonf1 9y agoHigh rises in general are designed to sway in an earthquake - that sway absorbs the horizontal forces being applied - similar to a tree. If an earthquake gets sufficiently large, say larger than any known measured earthquake to date, that sway differential would increase enough that buildings would either hit each other, or the building would sway beyond the ability of the structure to recover and fall over. A standard approach for tall buildings is to incorporate either a dynamic weight high in the tower to counterbalance the sway so it doesn't go critical, or incorporate dynamic elements in the foundation system. In general, if a modern high rise is falling over, all buildings without the benefit of this level of modern engineering have already fallen over.
- malnourish 9y agoWould you be able to provide an explanation of what a dynamic element in the foundation is, for example?
- whack 9y agoYour 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 agoMy 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 agoThe 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 agoEven 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).
- almost_usual 9y agoPeople are more likely to be killed by flying glass in the Financial District than skyscrapers collapsing. A good approximation of how far glass can be thrown downtown is roughly 2x building height due to the winds coming off the bay.
- Spooky23 9y agoIs that supposed to make it better? I have friends who unfortunately got to witness what happens when plate glass comes down. They can barely talk about it. It also means that the injured and trapped folks in the high rises are going to be without aid in buildings with dead mechanicals for awhile.
- komali2 9y agoI think he's saying, in an earthquake, stay inside. A lot of people think running into the street is what you wanna do. It is, in like, Mountain View maybe. Realistically you want to just jump under the nearest thing you can and hope for the best. If you're in the Financial District in the middle of the street... well your friends apparently have seen what that'll look like.
- almost_usual 9y agoRight, that was the point I was trying to make, perhaps I didn't state it well. Seek shelter immediately and try to avoid flying glass. I would also avoid UMBs (Unreinforced Masonary Buildings) these buildings WILL collapse. They aren't as common in FiDi but are all over Soma, Chinatown, and the Tenderloin.
- robocat 9y agoYeah. Lots of stuff comes from above if you are on the street. Going inside a building is a good bet. "35 deaths and many injuries from falling masonry during the 2011 Christchurch earthquake. Buildings with dangerous parapets, facades and verandahs" [1]. That was 20% of total deaths. Certainly near a skyscraper, you want to go inside, since if it pancakes, being outside won't help anyway - debris will hurtle horizontally. [1] https://www.stuff.co.nz/business/71738867/property-council-swings-in-behind-quakeprompted-masonry-changes https://www.stuff.co.nz/business/71738867/property-council-s...
- gascan 9y agoA modern high rise- but only as long as you are confident there were not basic design/engineering/construction flaws? Which, for those of us who are not structural engineers and cannot review the work to see that it is indeed well done...
- tedsuo 9y agoThis gets at my concern though - it is not that we don’t know how to build skyscrapers safely. It is that there is now positive evidence that those construction and engineering techniques are not being applied properly, at least in some cases. For me, the question is not about whether high quality projects are going to be okay. The question is: on what basis do I believe there has been sufficient oversight to guarantee the soundness of new construction? I can remember talking to SPUR members in 2001 about how problematic it was to extend downtown development into SOMA, etc, due to liquefaction and uncertainty. When the building craze hit, it felt like it brushed these concerns aside, rather than answer them. Now we have leaning buildings that don’t meet basic construction requirements. It doesn’t inspire a lot of faith.
- lutorm 9y agoThe leaning building across from my office, for example, has nothing to do with seismic issues but basic design/engineering/construction flaws You say that, and then you claim that seismic engineering is free from such flaws? That seems a bit like hubris.
- product50 9y agoSeismic is different than basic construction. That building tilt would have happened anywhere vs. in an earthquake prone zone like SF.