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

 

[TugboatEng]

From a coat perspective, yes.

 

[epoxybot]

Hydraulic Flat Jacks have capacities up to 1000 tons.

 

[epoxybot]

ENR: First Load Transfer a Success at Troubled Millennium Tower in San Francisco

 

[kevinsnn]

From ENR California today looks like just coping Ronald O. Hamburger post

NEWSPROJECTSCALIFORNIACALIFORNIA CONSTRUCTION NEWSCONSTRUCTION METHODSBUILDINGS
Building Repairs
First Load Transfer a Success at Troubled Millennium Tower in San Francisco
By Nadine M. Post
If all continues as expected the saga of not just the fix, but the fix of the fix, for the troubled Millennium Tower in San Francisco may be over by the end of September. The team for the revised perimeter pile upgrade—intended to stem and recover some of the settlement and tilt of the 645-ft-tall tower—reached a milestone last week. Workers from AECOM’s Shimmick Construction successfully completed the initial stage of the transfer of loads from the residential condominium—which has been settling since its completion in 2009—to six new piles to bedrock installed along one side of the building.

“Our expectation was that this first small stage of load transfer would slow substantially, if not stop, the already recently reduced rates of settlement and tilting that has been occurring,” Ronald O. Hamburger, the consulting principal with Simpson Gumpertz & Heger (SGH) who is the engineer-of-record for the upgrade, wrote in a Jan. 29 progress report to the board of the Millennium Tower Association. “Preliminary data shows this has been successful and exceeded the engineering team’s projections.”

 

[epoxybot]

NBC Bay Area's Jaxon Van Derbeken reports on the loading of piles on Mission St. with brief commentary by Harry Poulos, PE.

 

[epoxybot]

NBC Bay Area's Jaxon Van Derbeken has a new report concerning the seismic review of the upgraded Millennium Tower. Questions remain...

 

[epoxybot]

Zurich American Insurance Co. has been allowed to exit a lawsuit brought by AIG for $25 million; as part of the Millennium Tower Settlement.

 

[epoxybot]

The Millennium Effect or The Leaning Tower of New York City

The Real Deal: Nearly all prospective buyers have backed away from a troubled development site near the South Street Seaport, where a still-unfinished condo tower leans slightly to the north.

I'm being speculative here, regarding 'The Millennium Effect' but if the foundation problems are the cause of buyers pulling out of unit reservations for Lower Manhattan's 161 Maiden Lane, it doesn't seem to bode well for current owners of units in the Millennium Tower, as to resale value and time spent on the market. Too much bad news.

Since there is very little that is known, as to the cause of the tilt, it is perhaps too early to give this an Engineering Failure & Disaster thread.

 

[spsalso]

I'm not seeing how the "boding" transfers from New York to SF.

"I was gonna buy this condo in Millennium Tower, but that one that's tipping in New York just makes me nervous."

You weren't nervous ALREADY?

spsalso

 

[gwideman]

Likely of interest:

Josh of the YouTube Building Integrity channel's recent video -- "Did I Uncover a $100,000,000 Mistake with the Millennium Tower "Fix"?" "

https://www.youtube.com/watch?v=Xezg8PxVSYA.

Josh critiques the rather small plates at the bottom of the threaded rods in the jacking assembly atop the added piles. They look likely to be considerably too small to distribute the load, or even withstand the load. Josh could not find any calculations pertinent to them. And how does the rationale for the fusibility of the "fuses" make sense?

 

[Mark R]

I'm confused by his explanation. I understand why you don't want the pile to be tied into the rebar raft but I don't understand why you don't want the Bars to be connected to the rebar raft (floor of the vault) it seemed like everyone had to be the strongest connection and actually don't see a reason for them to not be connected all the way through their threads. Am I missing something? That would certainly help overcome the problem he discussed in the video.

 

[spsalso]

Mark,

I think perhaps it's because the threaded rod is designed to stretch. If the length that is in the concrete were bonded to it, that concrete connection would likely fail. So they work around that by NOT bonding the concrete to the rod. Only the steel plate is connected to the concrete.

Yeah, the plates look awfully small. But if you made each plate twice as big, would the added "outer edges" really be transferring much load? I dunno. But I do wonder.

As Josh was talking, I was waiting for the part where he or they thought that the steel plate embedment was so important that they actually built a REAL test piece and tried it out. In concrete. It appears it wasn't done. If it HAD been done, they could just point at it and say "Yeah, it works. Look over there and check it out." Didn't do it.

Meanwhile, over on the Tilt-O-Meter, things are sure interesting. Maybe confusing, too? Maybe it's working? Maybe it's not?

Tune in next week, kids.


spsalso

 

[dik]

I'm not sure of his credentials, or the design connection capacity. For bolt tension capacity, the Canadian code capacity is determined by Ultimate Strength and not yield... I suspect the AISC is the same. I was not impressed with his discussion about fasteners being designed for yield. Maybe snakeoil.

I'm not sure how the plate was designed, but I suspect it is compact enough that it would be the bearing on the concrete that determines the load capacity based on the area of the plate, less the area of the rods, times the confined concrete compressive strength, which can double the bearing capacity. With the size of the nut underneath the plate, shear strength of the plate would not enter into it, I don't think.

I'm pretty sure that this was not overlooked. Because it's so critical, I would not design this tightly, but I would be confident of it's capacity if that approach was used. I would think that a high concrete f'c would be used, but I hope they didn't use 25MPa.

I should have added... I think the project has some serious problems... including this guy.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[spsalso]

I guess the sticky part of this threaded rod connection is: how can you limit the load to 1300 kips? The building weighs a whole lot more, at 686,000 kips. So those new piles kinda sorta maybe have to hold up half of that. 686,000 / 18 = 38,111. Which is a tad more than 1300.

So, potentially those supports will suck up that much and then fail if loaded more. I think I'll stand on the uphill side as that day approaches. Ron, on the other hand, had better be downwind!


spsalso

 

[dik]

My biggest concern about their manner of remedy is that it non-symmetrical. I've done very little seismic stuff, and none recently, but I suspect strongly that cannot be good.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[dik]

With hydraulic jacks, I think it's pretty easy to load, monitor and maintain a load of that magnitude to a reasonably accurate value. I don't think the loading is an issue...

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[spsalso]

What happens to those jacks when/if the downward pressure of the building goes over the 1300 limit? In my experience, you can't hold something up with less force than it exerts downwards.


spsalso

 

[dik]

It doesn't... with hydraulics it's easy to regulate the pressure.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[spsalso]

Thing is, if you raise the pressure in the jack to counteract the increased pressure of the building, that same increase also goes down into the piles.

If you decide to raise the pressure in the jack above the weight input of the building, it will rise and/or the pile will lower. If the pile is on bedrock, it has nowhere to go except sideways.

Anyway, it's an interesting show to watch.

What would be nice is to add the pressure readings on the jacks to the Tilt-O-Meter.


spsalso

 

[dik]

I'm missing something here... you stablilse the load at 1300K. If it's less than the actual reaction, it will tend to lift the building until the 1300 load is reached. If the required reaction is greater than 1300K... you can maintain the 1300K and the building will continue to settle less quickly.


They can be set at a constant pressure and easily maintained at that pressure... kinda boring. What would be interesting would be to see the effects of the 1300K load... either up, down, or staying the same.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik