San Francisco high-rise sinking, tilting

CSTH

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^ Yeah, thanks for that clarity. I've been thinking more about this and I think it really comes down to: if there is a major earthquake, this building is toast.
 

bakgwailo

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^ Yeah, thanks for that clarity. I've been thinking more about this and I think it really comes down to: if there is a major earthquake, this building is toast.
If it is and does come down, it will probably damage quite a few buildings around it, too.
 

TheRifleman

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Even if the city deemed the Building has a very dangerous hazard I bet the developer could auction off the condos for the right price --I bet people would still buy those condos just to live in San Fran. Hazard or not they would risk their life.
 

bigpicture7

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Even if the city deemed the Building has a very dangerous hazard I bet the developer could auction off the condos for the right price --I bet people would still buy those condos just to live in San Fran. Hazard or not they would risk their life.
Maybe they would, but the hazard of a building that size collapsing is not limited to those who choose to live inside it:

If it is and does come down, it will probably damage quite a few buildings around it, too.
 

datadyne007

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Maybe they would, but the hazard of a building that size collapsing is not limited to those who choose to live inside it:
Right, the building really should be vacated and imploded in a controlled manner before it comes down on its own, though I don't know how feasible it is with TransBay next door. Money is money, it comes and goes, but people are gone forever when they are killed.

This building was a colossal mistake, but let's not make it a deadly mistake.
 
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TheRifleman

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Right, the building really should be vacated and imploded in a controlled manner before it comes down on its own, though I don't know how feasible it is with TransBay next door. Money is money, it comes and goes, but people are gone forever when they are killed.

This building was a colossal mistake, but let's not make it a deadly mistake.
How is the city Inspectors at this point not recommending this?
The city, taxpayers, insurance company, developers, consultants better start digging deep into their pockets at this point.

It’s doesnt take a building structural engineer to say this building is toast

Is there any possible way to salvage the foundation and connect it to bedrock as is?
 

odurandina

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i think it's less likely to totally fail anytime soon.

the tower is probably closer to a leaning tombstone (for now).
 

datadyne007

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It’s doesnt take a building structural engineer to say this building is toast
Well, yes, it does. We can't make that definitive "toast" assessment on our own, only offer conjecture. Buildings/structures are surprisingly resilient and are designed with redundancies to account for miscalculations, oversight or failure of members. A structural engineer can assess exactly what members are weakened and to what degree, then offer a verdict.

Is there any possible way to salvage the foundation and connect it to bedrock as is?
Yes, as has been discussed here, there is a method to underpin it, but it will pretty much cost as much as building a new tower and doesn't undo damage that may not be apparent yet (like to the curtain wall assembly).
 

stellarfun

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On Saturday, a drone being used to inspect the building lost its signal and crashed onto the street below. On Monday, someone will rappel down the side of the building and tape the crack. I'm thinking, with the lean, the carriages typically used for window-washing may not work.
 

stellarfun

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Here is a link to the video of the drone crashing.

https://sanfrancisco.cbslocal.com/2018/09/08/drone-crashes-cracked-window-sinking-millennium-tower/

The window washing system is apparently broken, thus the rappeling.

The reporter is in error. The leans is 14 inches, not two.

According to CurbedSF, the tilting of the building in the first half of 2017 was at a rate of 2.5 inches over that six month period. That brought the tilt to 14 inches, the numbers seem not to have been updated since. One can reasonably assume that if it had stopped sinking and tilting, it would be headline news in the San Francisco Chronicle.

The plaintiff's lawyers claimed in the summer of 2017 that the building could tilt an additional 8-10 inches over the next two years (from June 2017).
https://sf.curbed.com/2017/8/10/16127356/millennium-tower-lean-earthquake-sf-sinking
 

statler

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Boston often gets chastised for being behind the times and slow to pick up new trends but sometimes that works in our favor, I think.
 

bigpicture7

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^ scary/unreal/unreasonable....but....these issues with the TransBay Terminal are a separate issue from the neighboring Millennium tower (even if they somehow both relate to the garbage swamp these buildings were built on with inadequate foundations)...

Probably best not to mix issues in one thread, as it implies some sort of coupled causality that may be misleading

Maybe we can create a separate "structural issues with buildings" general thread for this stuff.

(Though I do think the sinking/leaning SF MT is such a high profile issue it deserves its own thread)
 

odurandina

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Do they know for sure what went wrong? i've heard bits and pieces, added to some exposure to gold mining near Mazatlan helps me form my baseless ad hoc theory....

The topography of the low elevations of the SF Bay Area is an 'alluvial plain,' resulting from weathering of the Sierra Madre over millions of years. The plain is comprised of loosely formed sediment extending to considerable depths before giving way to harder, shale layers. Fluidity of groundwater and soils also extend to great depths–which, in turn brings (as we are witnessing) significant risk of 'shrinkage' of the volume beneath skyscrapers. Along a ravine where the Golden Gate Straight opens into San Francisco Bay & San Pablo Bay, loose soils extend down thousands of feet to well-formed rock found at shallower layers nearby.

Over such topography deemed impractical for piles to be laid upon bedrock, they are pushed back by 'friction' at lower depths against gravels and soft stone to loads deemed sufficient. Despite the necessity of even 'more cautious' methodology, (2) consulting entities failed to foresee problems in the foundation for the 645' tower. i find this to be somewhat shocking.

Was Millennium guided improperly to use an insufficient number piles at too shallow depth? One can only assume. Could unforeseen water drainage at the deep (phreatic) zones caused by nearby construction cause the 'shrinkage' below the Tower's foundation? Did such a condition cause the 'side loading' on the piles be reduced and the building to sink?

Is it farfeched to consider it possible that other towers in SF, including Salesforce Tower could, over time, suffer similar fate? Has anyone entertained this possibility?
 

TheRifleman

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“To cut costs millennium decided not to drill to the bedrock”

How is that even an option in earthquake state like Cali? Especially the city of San Fran.
 
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bigpicture7

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Seems like they may have reached a breakthrough:
https://www.sfchronicle.com/bayarea/article/Millennium-Tower-homeowners-propose-100-million-13440479.php

In an application to be filed with the city’s Department of Building Inspection, the Millennium Tower Association laid out plans for a “perimeter pile upgrade,” 52 steel and concrete piles that would shift a portion of the building’s weight from its existing foundation system to bedrock about 250 feet below.

While the application outlines about $30 million worth of work, the entire pile upgrade would cost nearly $100 million and take 18 months. The contractor would drill 22 new piles along Mission Street and 30 along Fremont Street. Each pile is 24 inches in diameter and weighs 140,000 pounds and would take three or four days to drill into place. A reinforced concrete “inner pile” would be installed within each steel shaft.
And, importantly:
Mission Street Development LLC, the tower’s original developer, agreed to perform and warrant the retrofit, which would eventually be paid for by a settlement reached in ongoing, confidential mediation....
The developer, an affiliate of Millennium Partners, has been working with the homeowners for months to reach agreement on an appropriate plan to address harm caused to the residential tower by its settlement as well as tilting associated with surrounding construction activities by the Transbay Joint Powers Authority, which built the Transbay Terminal, and the developer of Salesforce Tower.
...so, a $100,000,000 mistake.
 

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