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]

Strictly speaking, it is ALREADY unstable. And has been for years.

Perhaps:

Uninhabitable? Drains can't drain, elevators can't work, golf balls won't roll properly when putted......

Likely to fall over? Hmmmm...........



spsalso

 

[dik]

Just adds a challenge.

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

-Dik

 

[1503-44]

So then a definite no for a billard club.

A black swan to a turkey is a white swan to the butcher.

 

[dik]

another challenge?

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

-Dik

 

[AutisticBez]

How much of a lean can the building sustain before the lean compromises the structure?

Obviously it's designed to be upright, and perhaps a lean isn't calculated into the design. At what point does the structure have to be demolished and these patch fixes abandoned as pointless?

 

[spsalso]

I think it partly depends on the chance of the building continuing to lean more after it gets to this "magic moment".

It's one thing to KNOW the leaning has stopped, and you can count on it. It's another if the building goes right on by, like an RPO picking up a mail bag.

That said, there's been talk about the need to keep a minimum of 1/8" per foot slope for the plumbing drain piping, and something about the elevators.

spsalso

 

[EZBuilding]

I saw this video on the Structural Engineering subreddit and found it to be very interesting.

https://www.youtube.com/watch?v=R22WWyFpjS0

It is a building in Santos, Brazil that had a correction for a 0.5 degree tilt. The video is in Portuguese, but does a good job of capturing the majority of the engineering concepts utilized.

 

[spsalso]

I presume the Santos building had stopped leaning when they did the repair. If not, then it would have made more sense to leave the jacks in place.

Millennium has not stopped leaning.

The video is VERY interesting, and it does look like they pulled it off, though sometimes the placement of the jacks and/or shims looked a bit haphazard. To me.


spsalso

 

[AutisticBez]

The more it leans though the more pressure is being applied more to the footings on one side of the building though? Won't there be a point of no return in terms of the leaning will increase at this point and it won't be possible to stop?

 

[spsalso]

Well, we can start with the rock bottom (if only!!!!) theoretical base: the center of gravity of the building moves outside its footprint. Simplifying practically everything, when the sideways movement of the roof reaches 100 feet, over she goes. The building is at two feet now. It would undoubtedly do the tippy-dance sooner, though.

The point of "differential pressure" as it tips is certainly interesting. And I wonder how much that differential pressure will cause "stuff" to ooze out from the higher pressure side. Geo-guys and gals might likely have something to say about this sideways oozing of mud. Or whatever water filled stuff is holding this building up. Or not.

One plus about this building actually falling over is that it will take out what I consider an ugly blight on a skyline that I gaze upon regularly: The Salesforce Cucumber.

The current rate of lean increase westward is 3" per year. So we've got about 400 years before it tips over, if the rate stays the same, and if the "rock bottom" case holds. So it would thus appear that Ms. Guglielmo was correct in stating that there is "...no cause for alarm..." at this time. Perhaps later.

spsalso

 

[AutisticBez]

100 feet? No issue sooner?

 

[Mark R]

While the theoretical point of no return is 100 feet a bigger question is at what point are people not going to feel comfortable living in the building? I'm sure it's well before the 100 foot lean. I'm sure even the amount it's leaning right now would be disturbing to some people.

Also, the farther it tilts I would expect the rate of tilting to increase based on the heavier load of the footings on that side of the building. This obviously is based on simple physics.

 

[RVAmeche]

Aren't they already having issues with the lean affecting drains? I can't imagine that situation at a 100 ft lean.

 

[spsalso]

I "yelped" this building, and found some very interesting reviews.


spsalso

 

[hamjohn]

Millennium Tower Foundation is Sliding as Building Sinks and Tilts
Jaxon Van Derbeken - Yesterday 11:47 PM

https://www.msn.com/en-us/news/tech...inks-and-tilts/ar-AAUc4jt?ocid=BingNewsSearch

 

[dik]

I trust the piles are moving with this and not shearing off...

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

-Dik

 

[spsalso]

If the piles have not sheared off, then the piles and the dirt around them (and under the slab) have also moved an inch. So where did the dirt go that was in that inch?


spsalso

 

[epoxybot]

I feel validated about my observations about the the snapping curb on Fremont St. and the so-called aging sewer line. Seemingly all tower related. Even the SFDPW stated the sewer line lateral-to-sewer main, servicing Millennium Tower was at the correct elevation. Hence the City paid for a sewer replacement (Elevation Change) as a favor to the Tower.

 

[kevinsnn]

Can someone say how much the tilt in this building compare with how much the columns can be out of plum per the code allowance. From bot to top of building?

 

[FacEngrPE]

I think the safe lean angle limit might be when the CG passes the KERN distance.

https://www.sciencedirect.com/science/article/abs/pii/096599789390048X[/URL]]The region within which axial loads may be applied to a compression member without inducing tension anywhere in the cross-section, commonly called the ‘kern’.

I think having the pilings on the high side of the building undergo tension would be very undesirable, but the building plumbing is sure to stop working before that point.