SF Millennium Tower Tilts Quarter Inch In Four Days (nbcbayarea.com) 62
Newly released monitoring data shows that San Francisco's Millennium Tower tilted a quarter inch during the four days it took to install the first test pile to bedrock last month. From a local report: The monitoring data tracks settlement, tilting and water pressure levels underneath the sinking and leaning structure since work began on a fix for the troubled tower in May. Since work began to shore the sinking structure up on the north and west sides, the building has settled nearly 2 inches at the northwest corner and is now tilting more than two feet at that edge. The latest data -- including the four days that the test pile was installed from Nov. 15 to Nov. 19 -- shows a quarter inch of new tilt, as well as a tenth of an inch of settlement at the time the test installation occurred. At the same time, there was marked fluctuation of water pressure below the foundation on the Mission Street side of the structure.
[...]
Still, Ron Hamburger, the fix designer, recently assured city officials that the settlement that has occurred during testing of new methods designed to limit sinking is within expected levels. Hamburger now has city permission to install two more test piles. Hamburger told city officials the additional testing is needed to help determine just how many piles will ultimately be used to shore up the structure.
[...]
Still, Ron Hamburger, the fix designer, recently assured city officials that the settlement that has occurred during testing of new methods designed to limit sinking is within expected levels. Hamburger now has city permission to install two more test piles. Hamburger told city officials the additional testing is needed to help determine just how many piles will ultimately be used to shore up the structure.
I'll bet $1.00 (Score:2)
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Be back here on April 9, 2022.
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A decent size earthquak
Expanda Foam! (Score:4, Interesting)
This building will fail at some point.
I'd suspect they will invest significant money into preventing that.
In Australia a technique has been developed to correct buildings that have tilted from mine subsidence.
What happens is instead of the large piles that you see being drilled here, they drill small piles about 100mm diameter diagonally *under* the building. Next a cavity is created at the end of the bore. Then a capsule of an industrial grade "Expanda Foam" is injected into the cavity and the bore is sealed.
As the foam slowly expands over a period of weeks the building rights itself to some extent.
The process is then repeated as many times as required to gradually correct the tilt of the building. I watched them do this to a building over a period of 6 months, not as big as this tower so it will be interesting to see if it can be applied to a structure of this size.
The will have to close the road in front of the building where the tilt is occurring to do the drilling - which they could probably do at night.
Re: Expanda Foam! (Score:2)
Re: Expanda Foam! (Score:4, Insightful)
The problem is the pilings don't go down to bedrock, as I understand it. There is a layer of Bay Clay on top of the bedrock that is between the bedrock and the pilings beneath the tower. The pilings they showed in the illustration I saw only went about halfway through the Bay Clay, and that's why it's settling and tilting. If they had put in deeper pilings to begin with, all the way down to the bedrock, then this wouldn't have been a problem.
However, many buildings can't be anchored all the way down to bedrock, sometimes it's just too deep (expensive) and/or the supporting soil or clay layers are strong enough to support the building's weight, after a bit of calculated settling.
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You imagine this expanda foam is better than bedrock, sand and bentonite. It isn't.
No, however it's better than demolishing a building you want to keep.
Modern construction is modern.
Apparently note modern enough to get the foundations right.
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I would strongly prefer not drilling at night
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A few years I lived north of seattle in a city called Shoreline.
They started drilling a tunnel for light rail from seattle to northgate, northgate was 6 miles south of me.
This means the drilling was more than 6 miles south, you following this?
The weird rumble/vibration made normal sleep impossible.
It seemed like a huge diesel ship engine was running near by.
This nightmare lasted nearly a year, I sold and moved far away.
Like KillAll said, they claimed we wouldn't hear anything, because it was underground.
We
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A decent size earthquake occurs in the area every weekor so. This building will fail at some point.
Given that its leaning, it is now partially supported laterally. That support can disappear for a period of time starting the instant of an earthquake, causing it to lean even further as the structure attempts to freefall towards a new equilibrium. Even if it survives an earthquake or two, it still just gets progressively worse.
Re: I'll bet $1.00 (Score:3)
Re: I'll bet $1.00 (Score:5, Informative)
It's hard to tell, but the piles are into a layer of compacted sand on top of the old bay clay layer. The current understanding is that the old bay clay well beneath the bottom of the foundations is settling much faster and much more than expected. The piles go all the way through that down to the Franciscan Complex bedrock.
The piles are there to move weight from the bay clay. Basically once the pikes are sunk they intend to literally jack the building up with hydraulic jacks.
Re: I'll bet $1.00 (Score:4, Informative)
Practical Engineering recently did a video about it: https://youtu.be/ph9O9yJoeZY [youtu.be]
The issue is that the ground is being compacted more than expected. I'm not sure filling will help.
The current plan is to insert steel pins that reach all the way down to the clay layer that doesn't compress much, to supplement the existing foundations. They will use hydraulics to transfer the weight of the building onto them. There will be some filling, but the weight will be taken by the clay layer.
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Just commenting because Practical Engineering is a GREAT YouTube channel. I found it a few months back and have watched many of his videos. Very interesting. I'm kind of obsessed with culverts now.
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He has a great presentation style, and I never thought I'd be so interested in soil. I like how now when I see random things like embankments I understand why they are built that way and how they work.
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Came here to say the same. It's an excellent piece of work.
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Re:I'll bet $1.00 you are right Pisa & Pizza! (Score:1)
It'll be demolished within four months.
Ron Hamburger is in an engineering pickle barrel as the plan convince the owners a mirage of stability is possible.
Well the demolition is far more likely as final result with casualty including the people in charge of reversing that tilt.
Tommy the pinball wizard needs to shake it!
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Extra pickles, hold the lettuce.
Special orders won't upset us.
Re: I'll bet $1.00 (Score:3)
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In four months that $1 will only be worth $0.75. #bidenflation
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There is a city in Germany called Hamburg and the name was probably innocent enough until sometime in the 1st half of the 20th Century. The writer Erle Stanley Gardner created a very popular series of novels around lawyer Perry Mason (also TV series), and Perry's nemesis in court was Hamilton Burger. I reckon Gardner may have done that on purpose to show disdain for his character.
There's also a German city called Frankfurt so there may be some Frankfurters out there as well.
I consider it a very uncool thi
Re: Ron Hamburger? (Score:2)
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True, and that's what a lot of people do. It's certainly what I would do. But it can be a big hassle. Sometimes there is pressure not to do so from family, and for some there's a stubborn I shouldn't have to do this mindset, a mindset that I am somewhat sympathetic to.
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There is a city in Germany called Hamburg and the name was probably innocent enough until sometime in the 1st half of the 20th Century. The writer Erle Stanley Gardner created a very popular series of novels around lawyer Perry Mason (also TV series), and Perry's nemesis in court was Hamilton Burger. I reckon Gardner may have done that on purpose to show disdain for his character.
There's also a German city called Frankfurt so there may be some Frankfurters out there as well.
As an Austrian I'm still shocked that our capital is named Wien...
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It's not as unfortunate as that Democrat Senator named Weiner who kept sending pics of his "wiener" to people he knew.
TIMBER!! (Score:1)
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The building is 645 feet tall. A quarter inch is about one part in 30 thousand. Seems to be about 2 thousandths of a degree tilt from this event. (I'm making some assumptions here because the reporter didn't bother to include any details about what these numbers actually mean. In his(?) defense, he probably had no idea what any of the details could have meant.)
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When I'm cutting down very tall trees, a quarter inch at the base raise is sufficient.
This is a quarter inch at the top. Still problematic, but they are hoping it can be stabilized.
If it fell, it would be the biggest disaster in San Francisco since 1989.
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By the way, I like to remind people that that earthquake was only a 6.9. As these things go, that's not all that large-- in 2013, Japan was slammed with a 9.0.
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Bear in mind these buildings have immense wind loading and deflect a lot at the top already.
Mr Hamburger. (Score:2, Funny)
I'll have a fries and large coke to go!
Sell it as an NFT (Score:2)
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If they sell an NFT of the building, maybe they could raise enough money to straighten out the real one.
But who would want an NFT of a now straight building? The 'value' would crash. They'd be shooting themselves in the foot.
I hope this gift stops giving (Score:2)
This story has been "the gift that keeps on giving", but I really hope it stops because if it doesn't, the best case scenario is that a huge area of valuable commercial space needs to be evacuated for a costly demolition.
The worst case scenario, well you can imagine--that their theory about gradual, predictable tilt is somehow wrong and/or this fiasco meets up with a strong enough quake to bring it all down catastrophically while occupied. You probably don't even need "the big one". What would a 6.0 on th
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What would a 6.0 on the San Andreas right by the city or on the Hayward Fault do to this mess?
It better be able to handle that, because it's coming sooner rather than later.
Investment value? (Score:2)
Maybe the horse has already left the barn here.
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An old skyscraper with famous structural problems solved is probably safer than a new, unknown one.
I remember a TV story about a long thin skyscraper that had too much liberty of freedom at the top (it swayed in the wind) - the architecture/construction company that did the work also found (and solved) a possible issue related to oscillation along the length of the building.
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I like this bit:
LeMessurier was lauded for covering their butts quickly once an undergrad kicked them i
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LeMessurier was lauded for covering their butts quickly
He did nothing of the kind. Not only did he NOT hide anything, he spent $2 million of his own funds to retrofit the building.
Sensationalism. (Score:4, Interesting)
Still, Ron Hamburger, the fix designer, recently assured city officials that the settlement that has occurred during testing of new methods designed to limit sinking is within expected levels.
This actually isn't that much.
By the end of August, when construction on the fix was put on, hold the building was tilting nine inches to the north and 23 inches to the west. As of Thursday, the Millennium Tower is tilting 9.5 inches north and 23.5 inches west.
But Hamburger says the numbers are not as dramatic as they sound. He says they have new data that suggests the building can tolerate a lot more.
“We just recently completed an update of that evaluation, where we looked at the building tilting as much as almost 3 feet to the north and almost 80 inches to the west,” said Hamburger.
Modern building can do a lot of leaning in movement. The engineering of these structures is impressive but to the ignorant, they are scary things that are likely to fall.
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This isn't a noticeable lean. The only reason we know about it is because engineers are taking very precise measurements. That said, if the trend continues, this will be a big problem.
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Yeah, but the slope goes the opposite way on the other side. How about telling us the current torque at the base.
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I'm curious how much of that tolerance uses up any earthquake dampening tolerances...
Explanation of the Leaning Tower of SF (Score:5, Informative)
Practical Engineering did a video on the SF Millennium building a couple of weeks ago, explaining what's happening, why it's tilting and what's being done to fix it. It's an excellent video on the topic
https://www.youtube.com/watch?... [youtube.com]
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Practical Engineering did a video on the SF Millennium building a couple of weeks ago, explaining what's happening, why it's tilting and what's being done to fix it. It's an excellent video on the topic
https://www.youtube.com/watch?... [youtube.com]
I came to post that link, you beat me to it :-)
a simpler explanation, and warning (Score:2)
Really, all you need to do to avoid this is to not hire the Pisa Engineering & Architecture firm . . . :)
hawk
The city that can't (Score:2)
Is there anything that SF can do right?
How many human lives is the Tofu-Dreg worth? (Score:2)
I know Ron Hamburger! (Score:1)