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

 

[spsalso]

link to the tip-o-meter:


Link



spsalso

 

[dik]

Thanks spsalso...

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

-Dik

 

[spsalso]

With the latest results from the tip-o-meter, the slope seems to be curving downwards, and so I will have to change my prediction of absolute tip to 300 years, from 400 years.



spsalso


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

 

[epoxybot]

The City of San Francisco has a Document Request Portal that has the latest SGH/Slate 18-Pile submittal. There are two versions, a 316 page "engineering" submittal and a 1374 page version prepared for Supervisor Aaron Peskin. It includes the engineering submittal, data regarding the installation of piles subsequent to the August halt in piling operations, due to settlement (see page 1067/1374). The document also contains, at the front, a mountain of emails between SFDBI, SGH, the EDRT and Dr. Pyke. You can go snow blind scrolling through the emails, which are provided repeatedly, 3 to 4 times! I think they do this on purpose.

316 Page Document

1374 Page Document

 

[dik]

I just thought of a neat April Fools joke... get a bunch of demolition contractor to meet on the QT at the site to discuss upcoming demolition plans for the site...

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

-Dik

 

With the latest results from the tip-o-meter, the slope seems to be curving downwards, and so I will have to change my prediction of absolute tip to 300 years, from 400 years.

That's good news, still well beyond the acceptance criterion of latest retirement date of implicated persons.

"Everyone is entitled to their own opinions, but they are not entitled to their own facts."

 

[spsalso]

"Absolute tip", of course, is the "worst" case. It seems likely the building will actually tip earlier. I dearly hope I'm still alive to see it take out the Sales Force Tower--I'd hate to miss THAT!

It can be noted that the Most Implicated persons involved in Champlain Towers have all long retired. In perhaps ALL senses of the word. Lucky lads. Sorta.


This morning, I drove by the building going west on the freeway coming off of the Bay Bridge. I tried to see if I could visually detect it leaning. I thought I did, but I had to also pay attention to driving, and so was distracted a bit from this important task.


spsalso

 

[epoxybot]

I was looking at some photos of an SGH inspection of the tower & podium last week and came across this gem. It is the southeast sloping SMRF. The main crack seems odd because it is open in the middle and closed on both ends. Is it a torsion crack? The image is taken looking to the south. This SMRF is about 4 feet from the edge of the hinged 3 ft. cantilever mat.

 

[Mark R]

That's certainly an interesting crack pattern and something it seems that the structural people would be very concerned about. Not sure what the cause of being but it sounds like your idea of being torsion is quite logical. It will begin to see if this is brought up again and is a subject of any further study.

 

[spsalso]

The crack(s) seem to be in a surface application of "somethin'", about a half inch thick, smeared over the concrete. Look towards the bottom of the beam, in the lower of the two photos. That SURELY isn't what's left after the forms are removed.

So maybe it's a shrinkage crack in the "somethin'". Or maybe there's an even bigger crack in the actual concrete hidden underneath.

Or there's nothing to see here--move along, please.



spsalso

 

[Ingenuity]

The crack(s) seem to be in a surface application of "somethin'", about a half inch thick, smeared over the concrete. Look towards the bottom of the beam, in the lower of the two photos. That SURELY isn't what's left after the forms are removed.

No, that is off-form concrete finish. The 'dags' you see at the bottom are where concrete slurry leaked behind the chamfer strip and was not removed after the forms were taken off.

 

[dik]

I would have thought the SMRFs would be located on the same plane, not slightly offset. Is there a reason for that? ductility?

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

-Dik

 

[spsalso]

"...off-form concrete finish."

Why would they smear this stuff? It can't be structural, can it? And, if not, what's the point?


spsalso

 

[Ingenuity]

Why would they smear this stuff? It can't be structural, can it? And, if not, what's the point?

Is it NOT a coating or a 'smearing' of cementitious layer.

A 1" x 1" (or 3/4" x 3/4") wood chamfer strip is added to the corner of the beam/column forms, and when concrete is been placed and consolidated the chamfer strip often moves slightly (if the chamfer is not nailed securely) and concrete slurry then gets between the chamfer and the face of the formply and then the concrete and slurry sets. Upon stripping the forms the 'dags' remain. Hence, an off-form finsh, no coating.

 

[dik]

Could it be a flexural crack from moment caused by vertical translation?

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]

Crack inclination signals a Shear crack. Flexural cracking would be more vertical at Top & Bottom extremes.

 

[spsalso]

Got it about the leakage behind the chamfer strip. Thanks.




spsalso

 

[dik]

Sorry Ahmed, the cracks are nearly vertical, and there are 2 or 3 of them, similar to a flexural crack in a high moment area... it was just a thought.

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

-Dik

 

[Walnuts]

Can any of you structural guys explain to me how the Baugrid connects at a joint like this? I checked their website and it looks cute in a beam or a column, but what do they do at connections?

 

[epoxybot]

I would have thought the SMRFs would be located on the same plane, not slightly offset.

The slope of the most southeast & most southwest SMRF are the result of needing 'driving' space for vehicle in the porte-cochère.

During peer review it was an element to which Hardip Pannu of Middlebrooke-Louie, noted a concern for the large elements behaving like shear walls. There isn't any information as to how his concern was resolved.

EOR, Derrick Roorda at that time with DeSimone Consulting Engineers, wrote in his paper for the SEAONC 2007 conference proceedings; "Design of Tallest Reinforced Concrete Structure in California – 58 Story Residential Tower in San Francisco" as so: