3 ms·

Are there any estimates on when it may actually fall? Or, is that not considered within the realm of possibility?

by yumraj 5y ago

jelliclesfarm 5y ago
Not sure..but it’s not just this one tower but a lot of heavy buildings in the general area..it’s a reclaimed landfill!!it’s worse than they are letting the public know..it could be on an accelerated schedule. https://sfist.com/2021/11/24/multiple-downtown-sf-skyscrapers-are-causing/ https://sfist.com/2021/11/24/multiple-downtown-sf-skyscraper... : Multiple Downtown SF Skyscrapers Are Causing Entire Area to Slowly Sink [..] Much media attention has been lavished on the tilting and sinking Millennium Tower, a fix for which remains in the works. But the building's situation has perhaps brought attention to the fact that heavy buildings clustered in an area atop landfill and bay mud — an area of reclaimed land that was once part of San Francisco Bay — are all collectively causing the ground to compact and sink beneath them.[..]
- jelliclesfarm 5y ago
  More : [..] While Millennium Tower, with its concrete frame, is the third-heaviest building to be constructed in San Francisco — coming in at 686 million pounds — no other tall buildings in the vicinity had drilled down to bedrock before Millennium Tower was built. (One Market Plaza and 101 California are the only buildings that are heavier.*) So when an engineer recommended concrete piles that only went down to a clay layer, the developers didn't question it. Subsequent construction, including that of the lighter-weight Salesforce Tower, did go down to bedrock with their foundations.[..] [..] Interestingly, Salesforce, which is slightly taller than Millennium Tower, weighs about half as much due to the nature of its construction. YouTuber Grady Hillhouse, whose channel is called Practical Engineering, suggests that all of this is kind of an experiment — with such tall buildings still relatively new to San Francisco, and, "Our ability to predict how soils will behave under new and extreme conditions isn't perfect, especially when those soils are far below the surface."[..]
  - abracadaniel 5y ago
    Practical Engineering is a fantastic channel, but it's fascinating seeing the news citing an analysis from a youtuber instead of doing the research themselves. I wonder if they interviewed him directly, or are just quoting his video.
- jelliclesfarm 5y ago
  https://sfist.com/2021/11/17/old-bay-clay-and-foundation-piles-millennium-towers-tilting-troubles-and-fixes-finally-well-explained/ https://sfist.com/2021/11/17/old-bay-clay-and-foundation-pil... [..]
- wahern 5y ago
  > it’s a reclaimed landfill!!it’s worse than they are letting the public know Yes, it uses friction piles into soil (far below the landfill) instead of down to bed rock. But this has become a not uncommon method around the world. In fact, Japan helped pioneer it in skyscrapers beginning several decades ago, albeit none as tall as the Millennium Tower. AFAIU, the Japanese experience, including across multiple severe earthquakes with post hoc analyses and in places much like San Francisco, lent it credibility wrt earthquake resilience. Clearly there's more to understand regarding failure modes and our ability to predict them, but AFAIU the choice was not eye brow raising except, perhaps, among the most conservative engineers. From what I've gathered, some engineers said they wouldn't have made the choice themselves, but none have said that choosing to do so was negligent. That's a gloss coming almost entirely from journalists, politicians, and social media commentary. And to be more precise, the issue with the Millennium Tower isn't subsidence per se[1], but asymmetric subsidence and rotation. [1] See https://www.sfchronicle.com/opinion/openforum/article/Don-t-blame-the-high-rises-for-Bay-Area-s-16004643.php https://www.sfchronicle.com/opinion/openforum/article/Don-t-...
  - jelliclesfarm 5y ago
    Agreed. But I think one of the issues in thus camel's back was also cheap steel that was used. I remember reading about it. Let me check if I had bookmarked it.

Are there any estimates on when it may actually fall? Or, is that not considered within the realm of possibility?

by yumraj 5y ago

Are there any estimates on when it may actually fall? Or, is that not considered within the realm of possibility?

Not sure..but it’s not just this one tower but a lot of heavy buildings in the general area..it’s a reclaimed landfill!!it’s worse than they are letting the public know..it could be on an accelerated schedule. https://sfist.com/2021/11/24/multiple-downtown-sf-skyscrapers-are-causing/ https://sfist.com/2021/11/24/multiple-downtown-sf-skyscraper... : Multiple Downtown SF Skyscrapers Are Causing Entire Area to Slowly Sink [..] Much media attention has been lavished on the tilting and sinking Millennium Tower, a fix for which remains in the works. But the building's situation has perhaps brought attention to the fact that heavy buildings clustered in an area atop landfill and bay mud — an area of reclaimed land that was once part of San Francisco Bay — are all collectively causing the ground to compact and sink beneath them.[..]

jelliclesfarm 5y ago
More : [..] While Millennium Tower, with its concrete frame, is the third-heaviest building to be constructed in San Francisco — coming in at 686 million pounds — no other tall buildings in the vicinity had drilled down to bedrock before Millennium Tower was built. (One Market Plaza and 101 California are the only buildings that are heavier.*) So when an engineer recommended concrete piles that only went down to a clay layer, the developers didn't question it. Subsequent construction, including that of the lighter-weight Salesforce Tower, did go down to bedrock with their foundations.[..] [..] Interestingly, Salesforce, which is slightly taller than Millennium Tower, weighs about half as much due to the nature of its construction. YouTuber Grady Hillhouse, whose channel is called Practical Engineering, suggests that all of this is kind of an experiment — with such tall buildings still relatively new to San Francisco, and, "Our ability to predict how soils will behave under new and extreme conditions isn't perfect, especially when those soils are far below the surface."[..]
- abracadaniel 5y ago
  Practical Engineering is a fantastic channel, but it's fascinating seeing the news citing an analysis from a youtuber instead of doing the research themselves. I wonder if they interviewed him directly, or are just quoting his video.
jelliclesfarm 5y ago
https://sfist.com/2021/11/17/old-bay-clay-and-foundation-piles-millennium-towers-tilting-troubles-and-fixes-finally-well-explained/ https://sfist.com/2021/11/17/old-bay-clay-and-foundation-pil... [..]
wahern 5y ago
> it’s a reclaimed landfill!!it’s worse than they are letting the public know Yes, it uses friction piles into soil (far below the landfill) instead of down to bed rock. But this has become a not uncommon method around the world. In fact, Japan helped pioneer it in skyscrapers beginning several decades ago, albeit none as tall as the Millennium Tower. AFAIU, the Japanese experience, including across multiple severe earthquakes with post hoc analyses and in places much like San Francisco, lent it credibility wrt earthquake resilience. Clearly there's more to understand regarding failure modes and our ability to predict them, but AFAIU the choice was not eye brow raising except, perhaps, among the most conservative engineers. From what I've gathered, some engineers said they wouldn't have made the choice themselves, but none have said that choosing to do so was negligent. That's a gloss coming almost entirely from journalists, politicians, and social media commentary. And to be more precise, the issue with the Millennium Tower isn't subsidence per se[1], but asymmetric subsidence and rotation. [1] See https://www.sfchronicle.com/opinion/openforum/article/Don-t-blame-the-high-rises-for-Bay-Area-s-16004643.php https://www.sfchronicle.com/opinion/openforum/article/Don-t-...
- jelliclesfarm 5y ago
  Agreed. But I think one of the issues in thus camel's back was also cheap steel that was used. I remember reading about it. Let me check if I had bookmarked it.