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Author Topic: The Leaning Tower of San Francisco & Other Cases for Hobbes  (Read 4655 times)

JLM

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #15 on: November 08, 2017, 02:29:32 am »
Not like an airplane.  The airplane balance issue has to do with keeping the center of mass forward of the center of pressure for dynanic stability. 

Here we have a structural issue.  A tilting tower will incur a bending moment that may result in loads in excess of the material capacity.  Concrete fails at a much lower load in tension than compression, increasing the risk of fracture on the high side.  On the other hand, the load increases on the low side, putting the steel sttucture at risk. 

The greatest risk is probably at the base where the piles attach to the main structure.  Most failures occur at joints and the cantilever load will be the highest there.

On the legal side, there are a few options for a cause of action.  Tort might be the most attractive from a damages perspective, but at this point the harm is purely economic.  Contract breach might be easier, but the remedies are more limited.  Best bet might be to ask for rescission.

One thing is for sure. vI wouldn't want to be anywhere near that building when the next big earthquakes hits.
 
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Hobbes

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #16 on: November 08, 2017, 09:33:32 am »
For a building that tall, the current lean isn't a factor.  There's no magic number, but if you start to measure the tilt in multiple degrees then you can know that the building is experiencing stresses it isn't designed for.  That doesn't mean it will fail: predicting structural failure of all but the simplest structures (single element structures, basically) is really beyond our current technology level: that's why it took over a year, countless people and supercomputers to even get close to understanding the one way the WTCs collapsed.  Forget trying to predict how things will fail in the future.

But the tilt this building has is really too small to be a worry about structural stability.  Though certainly the above are correct that the issue isn't tipping but forces induced in members as a result of being off center.
 
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JLM

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #17 on: November 08, 2017, 03:22:21 pm »
Agreed.  I expect that the margins are sufficient for the static
cantilevered loads.  I would be more worried about possible fatigue failure.  There may be parts of the structure that has normally purely compressive loads that may now see tensile loads during excitation environments such as high winds and earthquakes.  Brittle materials are particularly susceptible to bilateral fatigue loading. 

Even more worrisome is the risk of soil liquification during an earthquakes.  Were that to happen, the piles may not have adequate support to stay in place.  If the cg were to then to tip beyond the base, it would be timber time.
 
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Curelom

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #18 on: November 08, 2017, 09:33:09 pm »
palmetto_gal sez, “I first learned of this last night while watching ‘60 Minutes’.  I'm happy to live on the East Coast and plan to stay here.”

Imagine what it might be like to be at the top of this building in a hurricane! Or an earthquake of the magnitude of Charleston’s Big One in, was it 1868 or 1872? I hafta go look it up. As JLM sez, “One thing is for sure. I wouldn't want to be anywhere near that building when the next big earthquakes hits.” :o

JLM also sez, “Even more worrisome is the risk of soil liquification during an earthquakes.  Were that to happen, the piles may not have adequate support to stay in place.  If the cg were to then to tip beyond the base, it would be timber time.”

And when that happens, considering its height & mass of the building, & its location in one of the most densely populated daytime areas in California, & about a quarter mile from the S.F. approaches to the Bay Bridge, when it does keel over, it’s going to kill massive numbers of people, & deposit debris all over what should be one of the city’s main routes for evacuation out or emergency personnel & supplies in, & probably do actual damage to the bridge.

Liquefaction was the big issue in the 1989 Loma Prieta earthquake, particularly in S.F.’s Marina District, South of Market, & Mission District, which are on filled land. They were built over areas that were marshes, streams, or land filled with unstable material like those old Gold Rush ships & the rubble of long-ago burned buildings. That’s why it’s pretty typical for the big high-rise’s in downtown to have those piers going down 200 feet or more to bedrock. And in 1989, they almost unanimously performed well, except for a few unreinforced masonry ones built before modern building codes. Most of them didn’t even lose a lot of glass. The steel-frame buildings were able to flex the way the Golden Gate Bridge does in strong winds, & there were stories (apocryphal, but somewhat believable) of folks in the highest floors of some of them looking out the windows & worrying that their buildings might collide with others that were doing the same.

Since I’m not an engineer, architect, or geologist, I’m picking up interesting bits & pieces from people’s comments here. Thanks to everyone for chiming in – I didn’t think a topic like this would be so intriguing to so many people! :D
.
« Last Edit: September 06, 2018, 03:49:26 am by Curelom »
 
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Curelom

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #19 on: September 06, 2018, 03:52:08 am »
The Millenium Tower saga continues. A window on the 36th floor developed a crack for reasons not yet known. But if the building has been sinking & shifting, it isn't hard to figure out possible reasons.

https://www.sfgate.com/bayarea/article/Millennium-Tower-cracked-window-San-Francisco-sink-13206174.php
 
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Curelom

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #20 on: September 09, 2018, 02:49:54 am »
Here are pictures of the cracks that developed in a window on the 36th floor.

https://www.sfgate.com/bayarea/article/Millennium-Tower-s-managers-say-cracked-wind

It looks like they start near the outer edge of the window, which probably gives credence to what Hobbes said, that "the tilt this building has is really too small to be a worry about structural stability. Though certainly the above are correct that the issue isn't tipping but forces induced in members as a result of being off center."

And the more off-center the members become, the greater the stress.

I hope that's laminated or tempered glass. If those window panes pop out, with the kind of winds that can fly around among high-rise buildings, there's no telling where those razor-sharp sheets of glass could end up, & what or whom they might hit.
« Last Edit: September 14, 2021, 06:25:31 am by Curelom »
 

Curelom

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #21 on: October 01, 2018, 10:22:42 pm »
I forgot to mention it, but last week, the brand-new Transbay transit center, which has been likened to Grand Central Station, had to be closed down because cracks were found in steel beams in the top floor that support a garden roof level. This thing cost well over $2 billion to build, & just opened about a month ago. Now thousands of daily commuters are finding their buses or trains from around San Francisco, Alameda, Contra Costa, Marin, San Mateo, & Santa Clara counties rerouted to a smaller temporary terminal nearby, & downtown traffic tangled like a ball of yarn that a cat played with all day.

Sometimes I think San Francisco needs another Great Earthquake. ::)
 

Curelom

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #22 on: September 14, 2021, 08:55:11 pm »
The saga of the Leaning Tower goes on. No, it hasn't fallen down yet, but it is not doing well. The work being done to install pilings that balance the load is suspected of causing further sinking. It is now 22 inches off plumb. City building officials have put a stop to the work for now.

https://news.yahoo.com/leaning-millennium-tower-san-francisco-181023519.html

https://thehill.com/changing-america/sustainability/infrastructure/572052-officials-stop-100-million-repairs-on-americas

https://www.sfgate.com/local/article/san-francisco-millennium-tower-sinking-fix-halted-16455606.php

“The letter [from management], however, noted there’s been no material damage to the building and it is structurally safe, as emphasized by the building’s management.”

If they say it enough times, maybe they’ll come to believe it. I wonder how many occupants believe it – & how many are still staying there & actually sleeping at night after what happened in Florida, which made people in the Bay Area even more nervous. No one expected that little condo highrise (12 stories & 140 feet high, compared to 58 stories & 600 feet for the Millennium Tower) to just fail abruptly & cave in within 12 seconds in the middle of the night. 

https://www.msn.com/en-us/news/us/planned-fix-to-san-francisco-e2-80-99s-leaning-millennium-tower-getting-new-scrutiny-from-city-hall/ar-AAOh7ST?ocid=BingNewsSearch

Quote
{City Supervisor – equivalent of council member) Peskin says an independent set of eyes on the project is the best way forward. And no option should be off the table.

“There may come a day when we’ve got to make the painful decision to perhaps dismantle that building,” he said. “Whether we’re there yet or not, this panel is going to tell us.”
 

Sparky

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #23 on: September 15, 2021, 07:23:47 pm »
22 inches off plumb? I don't think I would want to stay there. I think it's past time to dismantle it!
 

Roper

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #24 on: September 15, 2021, 08:18:33 pm »
I don't think it's that big of a deal. Heck, I can turn a Lego tower completely upside down, and the minifigs inside never complain or get scared.
Education is not preparation for life; education is life itself. - John Dewey
 

Hobbes

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #25 on: September 16, 2021, 11:22:21 am »
I'm really glad I work in bridges...

It probably really is safe for normal use. But I wonder about seismic events, and it's possible the PR person is trying to make a clever distinction between "safe in normal conditions" and "can withstand an earthquake".
 

Curelom

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Re: The Leaning Tower of San Francisco & Other Cases for Hobbes
« Reply #26 on: September 24, 2021, 05:01:32 pm »
I'm really glad I work in bridges...

Well, part of the Bay Bridge's cantilever section did fall down in the 1989 earthquake, along with something like a mile of the Cypress Freeway. So did that highway bridge in Minneapolis.

More woes for the Leaning Tower. Sewer lines are reported to not be draining properly, possibly due to the lean, & causing blockages. This is not a big deal for occupants, of course, because if the building collapses, they won't need sewer lines.

https://www.sfgate.com/local/article/millennium-tower-sinking-plumbing-san-francisco-16485349.php
 

 


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