San Francisco high-rise sinking, tilting

The tower is now leaning 14 inches at the roofline, an increase of two+ inches in six months. Overall sinking is now 17 inches, and continuing with no letup.

Consulting engineers, including DeSimone the original structural engineer, are proposing a fix by drilling piles to bedrock. Perhaps up to a 100 piles. Cost of $100-150 million.

http://www.sfchronicle.com/bayarea/...r-keeps-on-sinking-but-there-may-11297935.php

Supposedly, the new piles would correct the tilt, but how this would occur is not explained.
 
stellarfun said:
The tower is now leaning 14 inches at the roofline, an increase of two+ inches in six months. Overall sinking is now 17 inches, and continuing with no letup.

Consulting engineers, including DeSimone the original structural engineer, are proposing a fix by drilling piles to bedrock. Perhaps up to a 100 piles. Cost of $100-150 million.

http://www.sfchronicle.com/bayarea/...r-keeps-on-sinking-but-there-may-11297935.php

Supposedly, the new piles would correct the tilt, but how this would occur is not explained.
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^Ok, I was off by $25+ Million ; )

bigpicture7 said:
I am willing to bet that they are going to spend the $75million it would take to underpin this. I almost guarantee it. Because if they don't, they'll spend at least as much on drawn out legal expenses/etc.
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But c'mon, can I have a little bit of credit that they might be considering an approach such as this in the roughly $100 mil ballpark?

bigpicture7 said:
... This sort of scheme (below) with tension/compression pile pairs, both anchored to bedrock, with cantilevered needle beams might work. (obv. this picture doesn't exactly reflect this reality...SF MT is on a big mat slab IIRC...but the concept is the same).

cantilever2websitefinal.jpg
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If they use a pile scheme such as this around the periphery of the building, they can literally jack it back up into place (albeit very, very slowly...imperceptibly slowly).
 
17 inches seems like a lot but I guess not that dangerous. At what tilt would the building considered to be in a dangerous situation?
 
Blackdog said:
17 inches seems like a lot but I guess not that dangerous. At what tilt would the building considered to be in a dangerous situation?
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It’s the tower’s leaning, according to experts, that could spell disaster for the luxury high rise.

“If they get too far off center,” former San Francisco assistant fire chief Frank Blackburn warned, “the elevators won’t work or they’ll jam.”

Blackburn, formerly director of the city’s earthquake preparedness effort, that could mean “people couldn’t get out – it’s a serious problem in my opinion.”
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Source: Tilting Millennium Tower Could Cost Taxpayers Millions | NBC Bay Area http://www.nbcbayarea.com/news/loca...xpayers-Millions-390248251.html#ixzz4nPOwccP3
 
TheRifleman said:
Sounds like being in a deathtrap if an earthquake happens.

Why doesn't most developments of this magnitude require the developer to hit bedrock for the foundations?
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Code didn't require it, but apparently San Francisco's code is being changed. And Millennium is going to bedrock on a new building some blocks away. Lesson learned. (Plus buyers might not buy without an assurance the building goes to bedrock.)

Supposedly, this particular building would not have sunk to anywhere near this extent if it had been steel-framed. Because its concrete, and significantly heavier, its the added weight of the concrete that is causing the sinking and tilting.

There was / is no code requirement in Boston that required MT to go to bedrock; MT Boston used the same structural engineer and very similar foundation for a concrete tall.
 
stellarfun said:
There was / is no code requirement in Boston that required MT to go to bedrock; MT Boston used the same structural engineer and very similar foundation for a concrete tall.
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I am confused - everything I have read has said MT Boston did go to bedrock.
 
Also, the relevant engineering firms involved were not the same. What is most relevant in MT Boston's case is the geotechnical firm, not the firm who designed the tower's vertical structure...and in that case, MT Boston's was Haley-Aldrich...based here and considered one of the local experts.
 
Yesterday, the city released a report by several consulting engineers on the ability of the building to withstand a major earthquake. The conclusion is that the building, at this time, will withstand such a quake,

However, as settlement continues, the building needs to be monitored, and the engineers recommend future re-assessments. The settlement continues at a rate of about one inch per year; at that rate by 2025, it will be about two feet. The mat is also 'tilting', currently about six inches.

In a quick glance, I did not find a referenced point, in the model simulations, when the degree of tilt and settlement would compromise the integrity of the building in a major earthquake. There is a hint that the building did not fare as well when measured (modeled) against the newest seismic standards.

http://sfgsa.org/sites/default/files/Document/MillenniumTowerSafetyReviewReport.pdf

This short, well-written report is the best description I've read of the foundation design, and the ensuing settlement and tilt.

(San-Francisco based Treadwell & Rollo, who did the original geotech, was acquired by Langan in 2010.)
 
Anyone want to do the trigonometry? If the mat is down six inches, what's the lateral displacement at the top of the building?
 
CSTH said:
Anyone want to do the trigonometry? If the mat is down six inches, what's the lateral displacement at the top of the building?
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IIRC, the article said the building is leaning 14" off center.

Edit: From the report:

Current measurements show an out-of-plumbness at the top of facade of about 14 inches to the west and 6 inches to the north. This is twice what would be considered an acceptable construction tolerance for out-of-plumb.
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Thanks. Decided to read the report - 14'' west and 6'' north
 
datadyne007 said:
IIRC, the article said the building is leaning 14" off center.

Edit: From the report:
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14 inches out of plumb at the northwest corner.

If I read the report correctly, the mat's 'tilt' increased from five to six inches in the past year. One might assume that if the mat's tilt goes from six to seven inches over the next 12 months, the 14 inches will increase to 17 inches.
 
Key takeaways IMHO:

1) This report is entirely focused on near-term earthquake safety, and repeatedly hedges against drawing any long-term conclusions about what to do...
Because of the unexpected and excessive settlement and building tilt, and the lack of stabilization of the settlements, the building warrants in-depth investigation.
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>>> Translation: "please do not cite us at a future date implying we did an extensive analysis and said everything was OK"

And,

2) They seriously don't know at what point in the future this will stop sinking at 1"/year, and thus do not know what the stable-state condition of the building will be with respect to the need to do an extensive renovation/stabilization...
...because the structure is still settling, continued monitoring and further study of the cause of the settlements is recommended to allow a better understanding of maximum future settlements. Once it has been confirmed that the settlement rate will reduce and estimates of maximum long-term settlement and lean are available, reevaluation of the acceptability of the structural performance of the building is recommended.
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>>> Translation: "a gazillion dollars may need to be spent on this...but do not accuse us of either saying it needs to be spent / or not needs to be spent in this report"

I am not disrespecting these experts...clearly their assigned scope was limited near-term earthquake safety. But, with that in mind, we really can't ascertain any more about Millennium's/their insurers' financial risks.
 
I agree with bigpicture's assessment. The city paid for these experts to do a seismic analysis of the near-term vulnerability of the building to a big earthquake.

The saving grace of the design is that the piles were driven all the way through the liquefaction zone. As the report noted, the adjoining sidewalks and streets might experience significant subsidence because of liquefaction, but the building, with the present settlement and tilt, should hold.
 
This is very bad---This tower needs to be deemed unsafe.

Not sure what millennium partners or the city was thinking concerning not drilling into the Bedrock the Millennium partners might want to settle this now before something catastrophic happens and we get a lot of dead people.


I think they need to knock this down.
 
Here is the question for all you lawyer gurus.

If this building collapses and kills a 100 innocent pedestrians who is at fault?
A. The developer (complied with all city regulations)
B. The city (they never take accountability
C. The condo association (own the building are liable for the maintaince and upkeep of the buildings needs)
 
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