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Millennium Tower is tilting, sinking

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Re: Millennium Tower is tilting, sinking

#131

Post by PhasmaFelis »

jordanlev wrote: post #110

> While the Millennium Tower’s sinkage into the earth is reportedly not a safety issue for residents, it does pose a problem for investors. This is confusing to me -- if it's not a safety issue, then why is it a problem?

The Leaning Tower of Pisa, for example, has stood without toppling for many centuries, but it's not a place you'd want to live in.

I also suspect that people with the kind of money they're looking for are not going to accept "don't worry, we checked and it's definitely 100% safe!"

Re: Millennium Tower is tilting, sinking

#132

Post by flukus »

rtpg wrote: post #60
WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

I really hope the SF rules for building giant buildings are similar to recent Japan ones. What I've heard is that after the Kobe earthquake, Japanese earthquake rules have been made so good that anything built after '95 has never fallen over, even in 2011-sized earthquakes (at least until the tsunami came).

Has there been a comparable earthquake yet?

Re: Millennium Tower is tilting, sinking

#133

Post by batbomb »

wahern wrote: post #29
WalterBright wrote: post #7

My house is on a steep hill, and Seattle has a reputation for hills sliding away under heavy rain. Before building it, I hired 3 separate geologists to evaluate the site. After digging holes, they said the site was sitting on "glacial till", which is clay that was compacted by about a mile of ice, and said there was nothing to worry about. Paying them was worth it for the peace of mind. (Turns out the till was so har…

I live in the Outer Richmond district of San Francisco, which was built on sand dunes. Most houses in my neighborhood were built in the 1920s and 1930s, +/- a decade. I was told by a contractor that it's extremely common for houses to have shifted considerably, sometimes by several feet. Mine certainly has, though not nearly that bad. Most of the houses are built on concrete foundation walls that go about 3 feet into…

Hi neighbor, I'm at 28th and Geary!

Re: Millennium Tower is tilting, sinking

#134

Post by wallflower »

Animats wrote: post #19

From the article: "To cut costs, Millennium did not drill piles to bedrock." I'm amazed that a building of that height would be built on a slab with friction piles in the mudflat fill zone of the SF bay. How did they get a building permit for that? 16 inches of sinkage in 8 years is huge. Building sinkage isn't all that unusual, but not for skyscrapers. There was a time when skyscrapers were only built on competent r…

It is important to note that one of the chief advantages of building a skyscraper in NYC is that bedrock is within 40 feet of the surface in the downtown district. In other areas of NYC, it is 160 feet to 200 feet below the surface.

Re: Millennium Tower is tilting, sinking

#135

Post by wallflower »

In contrast, the Salesforce tower under construction at 415 Mission Street is built on piles that connect to bedrock.

> In a big earthquake, the ground is actually trying to slip sideways underneath the building. “You need something to keep you from changing addresses,” says Joseph. Those somethings are called piles, in essence underground stilts connecting the building with the bedrock. In the lowlands of San Francisco’s Financial District, bedrock is 300 below street level. “We have 42 piles that go all the way down and are socketed 15 to 25 foot deep into the rock,” says Tymoff.

http://www.wired.com/2015/11/it-took-18-hours-to-pour-san-fr...

And this was part of the proposal from the very beginning.

> The Transit Tower would have a concrete slab foundation supported by driven piles anticipated to be founded on bedrock more than 200 feet below grade. The tower’s structural system is anticipated to employ the concept of “megacolumns,” which are very large structural columns several feet in width. The concentrated load supported by these megacolumns would be sustained by large diameter piles approximately 10 feet in diameter, with additional piles driven to support the building’s foundation slab.

http://sfrecpark.org/wp-content/uploads/00_FEIR_Draft-1_12-0...

Re: Millennium Tower is tilting, sinking

#136

Post by fennecfoxen »

omegaworks wrote: post #93
JosephHatfield wrote: post #61

Earlier quoted context omitted.

The city is currently requiring many owners of soft story buildings in the Outer Richmond district to pay for seismic refitting.

...And allowing them to pass on 100% of the cost to their renters.

The fact that they're not able to pass 100% of the cost of whatever capital improvements they feel like on to their renters is part of a massive wealth transfer from landlords to long-established tenants.

In other circumstances I'd accuse that of deterring investment and being a contributor to the terrible housing situation in the Bay Area in general, but honestly, the zoning / planning-permit situation is the first limiting factor.

Re: Millennium Tower is tilting, sinking

#138

Post by mikekchar »

flukus wrote: post #132
rtpg wrote: post #60

Earlier quoted context omitted.

I really hope the SF rules for building giant buildings are similar to recent Japan ones. What I've heard is that after the Kobe earthquake, Japanese earthquake rules have been made so good that anything built after '95 has never fallen over, even in 2011-sized earthquakes (at least until the tsunami came).

Has there been a comparable earthquake yet?

Here's a list of large earthquakes in Japan: https://en.wikipedia.org/wiki/List_of_earthquakes_in_Japan

There have been several large M7+ earthquakes in populated areas since the Hanshin (Kobe) earthquake. Tohoku was obviously the biggest. Several of the Tohoku aftershocks were over M7. This spring there was a M7 earthquake in Kumamoto, which I think is the largest earthquake in a very populated area since 2011.

Japan get several very large earthquakes every year, but they are usually in less populated areas. It's quite common to get M6+ earthquakes in populated areas, though. As the GP notes, damage is usually amazingly limited. I experienced one and was very surprised that nothing was damaged in my house.

http://www.jma.go.jp/en/quake/ is super interesting to look at because you get a real sense of just how often Japan is hit with earthquakes (several a day!).

Re: Millennium Tower is tilting, sinking

#139

Post by ternbot »

Maybe the buildings are not shifting but the world is shifting and the buildings are actually well built and staying in the same place? People, especially environmentalists, are quick to blame millennial developers. Mother Earth can take the blame here!

Re: Millennium Tower is tilting, sinking

#140

Post by ternbot »

Maybe the buildings are not shifting but the world is shifting and the buildings are actually well built and staying in the same place? People, especially environmentalists, are quick to blame millennial developers. Mother Earth can take the blame here!
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