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"

 

[hpaircraft]

...It would make the building actually visually interesting.

Oh, yeah! Just think of what they would do for the units they pass through on the way to the concrete core. Huge interior decoration potential!

 

[spsalso]

Oh, yeah! Just think of what they would do for the units they pass through on the way to the concrete core. Huge interior decoration potential!

I think the better route would be to make those newly subdivided units into Affordable Housing. Yes, there'd be less income for the property, but the points gained for Social Justice would offset that, I think.

spsalso


Herb Tarlek: "Do you know what we in sales call problems? Opportunities."

 

[apper.42]

Is this forum going to wind up becoming the laughing stock of eng-tips with never ending non serious ideas. Could we try and keep it relevant here.

 

[epoxybot]

In the first week of June 2007, Webcor Builders reported to Treadwell & Rollo that the tower appeared to be moving to the east. This was while the east face of the tower's foundation was tied to tower/podium shoring wall and the tower was around 20 floors up.

The production pile reinforcing was given in SG&H's 2017 Seismic Safety Report. SG&H butchered their description of the tops of the piles on page 5 of the report. There are so many mistakes, in their description of the piles that it borders on suspicious. Since it was one of the key aspects that the Peer Review asked to be examined, it is amazing that no one bothered to compare what SG&H wrote, with the figures at the end of the report.

LB Karp already suspects that there are failed piles under the tower.

One news report stated there is a SF Gov. hearing scheduled for next month.

 

[Walnuts]

Not only Larry Karp but also the LERA team. I don't know if that's where Larry and Josh learned of their concern about the tops of the piles or if they developed that independently. But the LERA team believed that one of the advantages of their "internal" fix is that the micropiles would be driven (actually pushed, not driven)through stout casings inserted through the mat and that these casings would restore some of the moment capacity that has been lost. I am not sure how critical this really is since the structures is embedded 25-35 feet, but even a small amount of dishing and tilting must have caused some damage to the tops of the piles.

 

[Walnuts]

Not me. I am just a simple dirt engineer.

 

[apper.42]

I think that the situation is so serious that Hamburgers group must be exposed for saying that the building is completely safe and nothing has failed. We have 950 prestressed piles that have an imposed rotation applied of approximately 0.003 in/in in bending which is the definition of the strain limit for ultimate strength of concrete. However the axial load in these piles due to prestress is 967 psi or 0.97 KSI which for an E = 4.8 x 10^3 KSI (7000 psi concrete) results in an initial axial strain of = 0.97/(4.8x10^3)= 0.0002 i/in The permanent vertical load per pile including is 229700 K /950 = 241 k/pile = 241/(194.9+(1.22x6)) = 1.19 KSI which gives a total strain in compression of 0.0002 + .0003 in/in = 0.0005 in axial and plus 0.003 in/in bending = 0.0035 in/in total strain. These figures are based on each pile carrying equal load and an equal fall east to west of 0.30% ie 22.5 in or 1.875 ft in about 640 ft = 0.00293 in/in.

Without any wind or earthquake the concrete piles at the slab are already strained well beyond the traditional 0.003 to 0.0035 strain limit for concrete in ultimate strength design and it should be incorrect to argue that nothing is overstressed. I agree 100% with Karp and the LERA team that probably a number of piles have failed.

Hopefully someone could verify my calculations and hopefully find some error or the building is not in a great situation. Walnuts & dik it might be time for you step up and prove me wrong. Since I deleted and revised this post Walnuts has already indicated he is not interested. Can someone else check.

 

[spsalso]

If the piles are disconnecting from the slab, as I think apper.42 is suggesting, then what is happening? The piles are still there to take the compressive load, so the slab shouldn't suddenly "smoosh into the mud" (a technical term).

The piles will still have an IMPERFECT connection to the slab.

So it would seem unlikely to have a catastrophic smoosh. More likely a drastically increasing tilt (sound familiar?).

But I'm just an irrelevant gadfly; what do I know?


spsalso

 

[apper.42]

If the piles are disconnecting from the slab, as I think paper.42 is suggesting,....

The fact that the concrete has technically failed in compression does not "disconnect" the piles from the 10' thick slab, reinforcing steel and friction in the concrete should maintain the connection but bending resistance is reduced or nullified and shear resistance is quite possibly reduced. Shear resistance is essential to transfer lateral loads from wind or earthquake to the piles. The tops of at least some of the piles have probably been physically damaged. It is very simple to check the slope on the base slab at any point across the 10' thick pad to assess the induced rotation of various piles in the group and the resulting strain. No catastrophic smoosh but, in my opinion, not good either. A slope of 0.3 feet across the 105' of 10' thick slab gives a slope of 0.003 ft/ft or .003 in/in which is the accepted limit for the strain in the concrete piles at ultimate capacity. Shoot a laser across and measure anywhere, simple.

 

[hamjohn]

Millennium Email Notes ‘Concern' About New Geotechnical Review

https://www.nbcbayarea.com/investig...oncern-about-new-geotechnical-review/2681355/

 

[hamjohn]

Engineers test new plan to prevent Millennium Tower from sinking

https://abc7news.com/millennium-tower-repair-sinking-fix-leaning-san-francisco/11123302/

 

[hamjohn]

Key Millennium Fix Test Starts

https://www.nbcbayarea.com/investigations/key-millennium-fix-test-starts/2680243/

 

[epoxybot]

I came across this news item from 2016 yesterday.
Global Construction Review: "Residents’ alarm as heavy luxury tower in San Francisco sinks and tilts"
In describing the Millennium Tower project on its website, DeSimone says that by using performance-based design as well as code-based design, it was able to "optimize the design of the perimeter frames and reduced their sizes more than what would typically be allowed by code".

DeSimone, as like Webcor, no longer lists Millennium Tower San Francisco on their project page.

 

[hokie66]

"Performance-based design" is fine when it performs, but when it doesn't...

The building is too heavy for the site. When the decision was made not to found it on rock, it was doomed.

 

[dik]

I suspect you're correct... and in an seismic area, to boot.

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

-Dik

 

[spsalso]

When they take it down, they should sell 4" cubes of it as memorabilia. Perhaps giving them free to the various people involved in the project.

I'd pay five bucks! Maybe $7 if it's got rebar.

No, this is not meant as a joke.



spsalso

 

[dik]

It would cost more than that to 'cube' it... As condo owners, are they responsible for the cost of demolition?

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

-Dik

 

[apper.42]

Not sure if you guys have "iron rings" in the US but here in Canada the iron ring which used to be steel and are now stainless steel were supposedly made from the casting that broke when part of the second Quebec Bridge fell into the St. Lawrence River. The first one collapsed during construction because buckling was not well understood in those days and the latticing on the compression chords was not correctly designed. The idea of course is to remind all graduate engineers of their grave responsibility to the public and to themselves.

Rebar from the Millennium Tower could serve the same purpose for graduates in the US and there would undoubtedly would be a huge supply if the tower either collapses or is demolished. Unfortunately either way these rings would probably be the most expensive in history.

 

[dik]

Sad... and I hope it doesn't come about. For other reasons, I don't wear the iron ring... to me and for reasons other than the bridge, it an symbol of engineering gone wrong.

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

-Dik

 

[spsalso]

People make mistakes.

Hubris is thinking it's always OTHER people.


spsalso