SF Tower settlement Part III 18

[dik]

thread815-412357
thread815-470048

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

From the news?
"A ritzy San Francisco condo tower is now leaning 26 inches and is expected to tilt by a further three inches annually after work to stabilize it ended up worsening the issue.

Just months earlier, the Millennium Tower - a high-end condo tower that opened in the earthquake-prone city in 2009 and sold units for millions of dollars - was only leaning 22 inches.

However, the 58-story, 645-foot tall building is now leaning 26 inches after stabilization work to help stop the sinking was halted because the removal of earth to add stabilizing piles was worsening its slant."

https://www.dailymail.co.uk/news/ar...-Francisco-condo-tower-leaning-26-INCHES.html

At what point does this become serious?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hokie66]

Probably about 5 years ago, I think,

 

[dik]

hokie... you missed the 'happyface'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[spsalso]

"...there is no cause for alarm..."

Emily Guglielmo, former President of the Structural Engineers Association of Northern California

Though, to be fair, she may have modified her views since making this statement on September 9 of last year.



spsalso

 

[epoxybot]

NBC: Leaning San Francisco skyscraper is tilting 3 inches per year as engineers rush to implement fix

Excerpt: In a Thursday letter to the Millennium Tower Association, the San Francisco Department of Building Inspection said it had approved the new 18-pile plan, writing that it is "satisfied that the associated settlement and tilt remain within safe ranges and support [Hamburger's] proposal to continue the retrofit using the modified installation procedures."

SFDBI Permit Services - Deputy Director III, Neville Pereira, stated in the Govt Audit & Oversight Committee Hearing, that same day, that they were WEEKS from completing a review of the revised 18 pile solution. Starting at 3:17:00 in the Govt Audit & Oversight Committee Hearing video.

 

[Walnuts]

That was by some national NBC correspondent, I think, rather than Jaxon van Derbeken of NBC Bay Area. I haven't seen the letter, but I am guessing that DBI has allowed them to continue under the existing permit to install more piles. That is what was said in the meeting. I understand that hamburger is speaking at a meeting of the Homeowners' Association this evening. I wonder whether they will throw eggs at him?

 

[dik]

I just listened to the review meeting. Pike's comments were alarming, and he came across as a bit of an alarmist. This needs clarification. He may be correct and there should be a real concern and there is a real reason for being an alarmist. I cannot imagine a 600' building 'falling over'. If his concerns are real, the committee was pretty dismissive of his presentation and I would have thought that they would have delved into his comments, at least a little bit. Sounds like politics at play.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hamjohn]

Leaning San Francisco skyscraper is tilting 3 inches per year as engineers rush to implement fix
IS NOT TRUE.

LINK TO AN OFFICAL PLOT TELLS A DIFFERENT STORY.

https://sfdbi.org/sites/default/files/20211027 Monitoring Report 026.pdf

FIGURE 026-05 SHOWS:

FIVE YEARS FROM 2006 TO 2010, ZERO TILT WAS RECORDED TOWARD THE WEST, AND FOUR INCH TILT WAS RECORDED TO THE NORTH. ELEVEN YEARS LATER, NOW THE TILT IS 24 INCHES TO THE WEST AND 9 INCHES TO THE NORTH. DOES THIS MAKE SENSE?

SEVEN YEARS FROM 2011 TO 2018, THE TILT WAS 14-INCH TO THE WEST. 2013 AND 2015 WERE THE ONLY TWO YEARS THAT THE TILT WAS APPROCIMATELY THREE INCHES.

THREE YEARS FROM 2018 TO 2020, THE TILT TO THE WEST HAS BEEN REDUCED TO APPROXIMATELY TWO INCHES. IS THIS THE REASON MR. HAMBURGER CONCLUDED STRUCTURAL UPGRADE OF THE BUILDING IS NOT NEEDED?

DURING THE FIX FROM 11/2020 TO 8/2021, THE TILT TOWARD THE WEST INCREASED BY SIX INCHES.

 

[epoxybot]

It looks like NBC has updated their story to clarify that the 18 Pile ~Solution~ is scheduled for completion of SFDBI/EDRT review by February 28th.

One thing I think noteworthy of last Thursday's Govt. Audit & Oversight Committee meeting was how Stanford Prof. Gregory Deierlein danced around the 'Cracked Foundation" question. It looked to me like he checked himself, during his response. The notion that the EDRT doesn't want to bring into discussion the hinged 3 foot cantilever slab, at the south end of the tower, to members of the SF Board of Supervisors is troubling.

While he is right about cracks in the bottom of the mat being in an anaerobic environment and thus slow to develop corrosion, the current monitoring regime does not include elevation changes to the 3 foot cantilever slab. Prof. Deierlein suggesting everything looked fine back in mid-2017 doesn't really inspire confidence. The crack could literally be a hairline at the base of the southern SMRFs. Ron Hamburger danced around the cracked foundation as well. You don't find cracks by coring, not without field input.

 

[Walnuts]

epoxybot, the bottom of the mat is now likely below the groundwater but when the test micropile perforations were drilled through it, I am told that it was dry because, even though the alleged dewatering by neighbors was minor, there was some and at that point it had not recovered. Corrosion products will not be swept away like they can be from steel pilings under a bridge with a fast current flowing under it, but I wouldn't completely discount the possibility of corrosion.

 

[JStephen]

"Bring dynamite and a crane
Blow it up, start all over again."
Nashville Teens, 1964

 

[dik]

I thought he was going to step into something... but, he evaded it quite nicely. No one wants to talk about the cracks on the bottom; you cannot see them anyway. Some of the photos show, what I would consider, as significant cracking.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[FacEngrPE]

This pile fix seems to assume that the new parameter piles will take up their "share" of the load. I wounder if anyone has attempted to figure out how the loads will actually transfer?
Important considerations
[ul]
[li]Spring rate of each pile.[/li]
[li]Flexibility of the foundation mat.[/li]
[li]Load transfer (sideways) in the building support system.[/li] [/ul]
Considering the loads tend to transfer to the stiffer supports, what keeps the loads in the new perimeter piles below their design load limit?
Is there anything from preventing this load transfer from accelerating the cracking of the foundation mat?

The Leaning Tower of Soma is a mess—but everyone’s ducking responsibility
Is the cure worse than the disease? Will the building keep tilting and sinking? Can it survive an earthquake? Answers do not inspire confidence
By Tim Redmond; January 6, 2022

 

[dik]

If the building 'falls over' are the tenants (ie, condo owners) responsible for the costs of repair for damage, in addition to the loss of value for the condo units. Are the condo units a multi-million dollar liability?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Sym P. le]

I suppose the answer to that would inform current remedial actions as well as future maintenance. Right now someone is footing the bill out of fear of certain liabilities.

(That's the easiest answer I can come up with

 

[spsalso]

A recent Building Integrity video discussed who owned what in a condo. Individuals own inside their condo. The condo association owns the structure. So it would seem the condo association would be responsible if the building fell over. So it's up to them to make those damaged whole. Of course, they may well say it was actually someone else's fault the building fell. Now we get into multiple lawsuit/defendant land.

But, pretty much, if it's your "thing" and it causes damage, you get to pay:

Your house catches fire, and burns down the neighbor's house, it's YOU (or your insurance).
The brakes fail on your parked car, and it crashes into a bus, it's YOU.
An electric space heater you own or have control over destroys much of a building and perhaps kills some people, it's YOU. Again, YOU can try to transfer the blame to someone else, but first it's on YOU.

I'll just mention "act of god" here, but since the building's been tilting for years, that ain't gonna fly.


spsalso

 

[epoxybot]

Walnuts: I agree that the anaerobic conditions would not suffocate the corrosion process, just slow it down. How much is debatable. Since the TJPA characterized groundwater in the area as brackish, an electrolyte solution is present to feed the reaction.

Dik: The legal settlement pretty much puts the Homeowners at future risk, if the tower were to collapse. It would definitely damage Salesforce Tower across Fremont St. I hate to think what it would do to 350 Mission Street, with its 50 foot tall lobby.

After the 36 inch casings were drilled, were they backfilled or are they just sitting in the ground open? It looks like the drilling of the 36 inch casings was done from the surface down through the tower shoring wall. I can't help but wonder how that might contribute to the current settlement issues.

Perhaps the reason the large PG&E vault at the south end of the foundation is not part of any Environmental Impact Report is because San Francisco excludes an "Existing/Replacement" utility from CEQA. This is only suppose to apply when there aren't any Special Conditions. I would think the Seismic Security of the PG&E vault would predicate it being part of any CEQA for Millennium Tower New Build or Remedial work. This is SF Planning doing their usual dirty work.

When in 2005, Mission Street Development submitted their plans for review by the TJPA, a PG&E vault was mentioned as a concern, relative to future Train Box excavation. I fail to see how a Hinged 3 Ft. Cantilever Slab supporting the "Replacement" utility vault, escapes Environmental Review or a separate seismic safety review by the City, the Developer, the HOA, etc.

 

[Walnuts]

epoxybot, I believe the 36-inch casings have been left more or less open, filled only by the final plug and then whatever sediment has fallen out of the column of water inside the casing. That might be quite considerable. For one of the 24-inch pile installations that Ben Turner of DBA reported on, there was quite a large depth of sediment on top of the plug. I wanna say 16 feet but I would have to dig to confirm that number. I don't know what shoring might have been left in place, but I assume they are outside of that. But all the casings were inserted through holes that had been left in what I think they call the "guide beam", a new concrete box that runs all the way along both Fremont and Mission Streets that has the locations of all the planned casings pre-marked in it. I read somewhere that that was done partly to make sure that the casings went in at exactly the right locations and also to minimize downdrag on the existing basement walls. I don't know what happens to the guide beam when they dig down to construct the mat extension (should they ever get to that point).

 

[dik]

I was thinking that... and that the current owners may have a multi-million dollar liability on their hands, beyond the cost of ownership of their units.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Ahmad Uzair Arshad]

I am not an expert.

In my opinion tilt is worse than sinking. Tilt will not only increase the pressure on one side of the footing but also increases secondary moments on structural members due to P-Delta effects.

What if they just balance the tilt by increasing pressure on the opposite side or something along this line.

This may increase the sinking. They may loose a story or two in this process, but sinking will probably stop,
Once the soil beneath gets compacted enough.