SF Tower settlement Part II 18

[1503-44]

"Appreciation has dropped to 2%"
Well that's less than inflation, but more than interest rates.

Although as I said, probably nobody bought in for either of those reasons.

“What I told you was true ... from a certain point of view.” - Obi-Wan Kenobi, "Return of the Jedi"

 

[dik]

not permanent... only temporarily until the 'fix' can be done. I'm not sure what the fix is... but for seismic reasons, I would think it would have to be symmetric with the structure.

We've had instances where water can be contained in clay at -40C in a supercooled state because the clay is so tight the ice crystals cannot form.

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

-Dik

 

[dik]

Maybe an upcoming Terzaghi can do a study similar to the Transcona grain elevators...

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

-Dik

 

[epoxybot]

On November 19, 2020 Ron Hamburger gave a presentation titled Understanding San Francisco’s Millennium Tower Investigation and Retrofit. It used to be on SEAONC's website but no more.

Under Emily Guglielmo, SEAONC gave their 1st Virtual Convention from Dec. 2nd-4th.
This was the teaser...

...SEAOC's first-ever virtual convention will take place December 2, 3, and 4, 2020. Making the transition to a fully virtual convention is no small task, and the convention committee and presenters have worked hard to make the sessions engaging and accessible. The dual-track technical program is filled with over 30 compelling presentations, opening with a session by Professor Greg Deierlein of Stanford University about the work of SimCenter, and closing with a presentation by Ron Hamburger on the Millenium Tower Perimeter Pile Upgrade. PDH credits will be available for sessions that are watched live. [End]

The "Proceedings" include a paper by SG&H, which is shamelessly loaded with blame for all the surrounding properties and very little to say about the poor foundation.

Whoops! Here is a link to the video. (Scroll Down)

Okay, the video is definitely worth a watch.

 

[hamjohn]

SEAOC 2021 CONVENTION, September 22-25, Technical Presentations do not include Millennium Tower.

https://seaocconvention.org/technical/

 

[AusG]

SEAONC

I was just watching the Ron Hamburger talk when my city felt the largest earthquake ever recorded here. 5.9 but only very minor damage as the epicenter was miles away. No serious seismicity from that area ever before.

 

[hokie66]

FYI, AusG is talking about Melbourne, Australia.

 

[hamjohn]

Tilting Millennium Tower in San Francisco Faces New Plumbing Problem

https://www.msn.com/en-us/travel/ne...umbing-problem/ar-AAOL6xK?ocid=BingNewsSearch

 

[dik]

Not even as a 'what not to do'?

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

-Dik

 

[epoxybot]

So the 2020 Virtual Convention video takes forever to load. At about 26 minutes into the video, Ron Hamburger describes the 3 foot thick section of the mat. I have transcribed, this portion for posterity.

Ron Hamburger:
...What’s important to understand here, as to why the building is tilting; I talked before about the 3 foot thick portion of the mat, at the south end of the structure that is soil supported.

As part of the construction of the Transbay Terminal to the south, the team that developed the Transbay Terminal, constructed a deep buttress wall immediately to the south of the Millennium tower site and the intent of that buttress wall was to protect the Millennium tower against soil movement beneath it; as the excavation for the train box, beneath the Transbay Terminal, occurred.

We believe that the southern end of this 3 foot thick mat is hung up, on this buttress wall, which was constructed adjacent to the Transbay Terminal.

Which is why it is not settling much.

Whereas the rest of the building is settling quite a bit.

And this explains a bit, why the building is tilting as much as it is, to the north & to the west.

When we looked at the behavior of the mat under dead & live loads and opposed settlement, using this refined non-linear model, we found the building was behaving very well indeed and there was almost no non-linearity that was visible, except at the juncture between the 3 foot thick mat & the 10 foot thick mat, at the south end of the structure.

There we see that a plastic hinge has formed, in the mat, as a result of those steep contours that are occurring at the south end.

Basically, what has happened is that the bottom layer of reinforcement in the 3 foot thick mat, which extends into the thicker 10 foot mat, HAS YIELDED, allowing the 3 foot thick mat and the PG&E vault to rotate, relative to the building.

We’re not seeing cracking in the mat in that area because the cracking is on the underside, of the mat.
The plastic rotation is very small, on the order of .4%, which is why we are not seeing any crushing or spalling. [END]

I can't believe he said these things to a group of engineers. To begin with, the buttress wall is behind a shoring wall built by the TJPA's Buttress-Shoring & Excavation Contracted builder, Balfour-Beatty Infrastructure. That didn't take place until mid 2011.

The 103 crack gauges, were installed in the tower & podium/garage BEFORE the Certificate of Completion (Aug 09) was issued. Years BEFORE the TJPA's shoring wall & buttress wall even existed. To my mind, the cracks in the basement east & west basement walls near the south end of the foundation are the result of the same forces acting on the mat. Ron Hamburger's statements and John Egan's Mat Grillage sound and look dodgy. But equitable.

It just doesn't fit with Gregory Deierlein's assertion that all the deformation in the mat took place BEFORE the tower was open to occupancy.

 

[Walnuts]

Thanks epoxybot! I think when Hamburger says "hung up" he just means that the vault is close enough to the shoring wall that it has to overcome some traction on the wall in order to settle. But that is not very likely. Maybe for a very quick settlement, but over time it would creep down if it wanted to go down. There are two much more likely explanations for the differential settlement: (1) the intermediate sand layer is not a single uniform layer. It is a layer of mixed deposition and variable thicknesses. Also the "crust" of the Old Bay Clay is likely of variable thickness having been eroded non-uniformly before the sands were deposited on top of it. This is all "known". (2) The second possible reason is more speculative but if the enhanced rate of settlement during the perimeter pile installation is due to the OBC oozing into the casing, as seems to be suggested by Dr Vahdani, doesn’t this suggest, along with the overall pattern of continuing settlement, that a creep bearing capacity failure is occurring in the OBC? This might explain why settlement continued for at least two weeks after the pile installation was put on hold – at that point I think the 36-inch casings were all tipped in OBC – and why the extensometers show continuing “settlement” in the OBC? Again, this is a bit speculative but the tendency for a creep bearing capacity failure (you push down on a soft clay and it bulges around the outside of the loaded area - classic soil mechanics), would be resisted much more on the south side (the bus station) and the east side (the podium building with a garage underneath it). It would be interesting to know if the intersection of Fremont and Mission has come up at all.

 

[Enable]

Is anyone else wondering why anyone involved (AHJ, principal engineers, etc) are talking publicly about the project? I mean, it's a complete clusterfuck and everyone is going to be sued. Part of a condition of our insurance is generally not to impair our insurance company's ability to defend once we know of or should have reasonably foreseen that a suit would be forthcoming. Don't you think statements about causes/failure/whatever even if well intentioned, may potentially void insurance coverage if they turn out to be wrong (and most will be just by the nature of this thing)?

I appreciate people willing to talk from a general interest perspective. But I really think the hole they are digging themselves is quite deep and tilted (pun intended)

CWB (W47.1) Div 1 Fabricator
Temporary Works Design

https://www.enable-inc.com/

 

[epoxybot]

I get the impression they knew about the 3 foot thick portion of the mat cracking before the 2017 City of San Francisco - SG&H Report. Why wasn't it in the 2017 report?

 

[dik]

ROTFLMAO comes to mind... it's kinda rude though... but, other engineers would understand and would appreciate it.

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

-Dik

 

[dik]

At which point does the hamburger lose all credibilty?

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

-Dik

 

[spsalso]

At which point does the hamburger lose all credibilty?

Glad you asked. I think here:

"The required construction is neither complex nor unusual." Ronald O. Hamburger

So, then, the job was a piece of cake; and if it failed, the designer was a total incompetent and shouldn't be trusted to tie his/her own shoes. Or so it seems implied.

spsalso

 

[apper.42]

.... but the tendency for a creep bearing capacity failure (you push down on a soft clay and it bulges around the outside of the loaded area - classic soil mechanics),

This is why I suggested earlier to restore the overburden pressure and counteract this bulging into the casing and causing it to bulge out and under the pile group and counteract the sinking. You did not think that this would work; I think that the overburden removed for the 3' casings is the main reason for the increased settlement.

 

[apper.42]

At which point does the hamburger lose all credibilty?

I'm not sure but his career is probably "fried" or possibly BBQ'd

 

[spsalso]

Hamburger seems to have proposed that the tilt of the building is caused by the "flap" on one side being held up by a retaining wall--hence it rotates about that point.

So how's about we build a retaining wall on the OTHER side, scab on a bunch of concrete, and lift like hell with the hydraulics? Or perhaps a whole lotta prybars being used by the homeless being paid the new minimum wage. Just a thought.

Proof of concept has already been demonstrated by the first "flap". According to Mr. Hamburger.



spsalso

 

[spsalso]

Tilting Millennium Tower in San Francisco Faces New Plumbing Problem

https://www.msn.com/en-us/travel/news/tilting-mill...

As someone who has spent a few hours in proximity to drain pipes, I will speculate that the Engineers who designed the drain system did not leave any "slop" for correcting these problems.

What you want: "Don't worry. We'll just cut this section out and fit a new one with some more slope. Two hours, tops! Who's buyin'?"
What you don't want: "Ya know, if they'd only left a little room here and some space there......."

I look forward to being corrected.


spsalso

 

[Walnuts]

apper.42, I thought you were suggesting filling the 36-inch casings with heavy material. That might help reverse the extra settlement caused by the faulty installation of the perimeter piles, or might not, we don't have enough information so we are speculating on what happened, but if the "creep bearing capacity failure" is correct, you would have to surcharge Fremont and Mission Streets. I doubt that that is practical. But I agree with you that the hamburger is more than overdone at this point.