Timber!
"... listing a few inches to the northwest, ..."
Gee, anybody wanna take bets as to where this will fall in the next earthquake?
San Francisco's sinking luxury Millennium Tower: Tilt spotted FROM SPACE
San Francisco's $350m leaning Millennium Tower is continuing to sink into the ground, European satellites orbiting Earth have confirmed. The 58-story landmark, at 301 Mission Street, is one of the tallest structures in the tech-playground city, overlooking the bay and the metropolis's startup land. The swanky skyscraper, an …
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Sunday 27th November 2016 09:30 GMT Anonymous Coward
Re: Timber!
Actually you have a point there. If SF gets hit by a major quake, the ground under the tower might suffer liquefaction since it is only landfill and not bedrock. At that point the concrete slab that the tower is built on will sink. If they are lucky it will sink straight down, but the odds are that one part of the slab will tilt which means the whole tower will start to lean over. At that point being somewhere else would be a very advisable strategy.
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Monday 28th November 2016 10:35 GMT jake
Re: Timber!
How about the next quake that hits the San Francisco Bay Area measuring between 6.8 and 7.2? The way I see it, anything over 7.2 is so unlikely that neither you nor I will likely be alive when (not if!) it hits, and anything 6.7 and under is barely worth getting out of bed for.
Before you answer, digest this:
http://pubs.usgs.gov/fs/2015/3009/pdf/fs2015-3009.pdf
WARNING! 6 page PDF totaling 32+ Megs! WARNING!
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Friday 25th November 2016 22:32 GMT oldtaku
Such a clusterfark - the developers were too cheap to sink the piles all the way down, and now they're saying they don't even have to fix it, they can just let it sink and it'll stop eventually.
But there's no reason to believe that 31 inches is an actual limit - that was an estimate from an engineer hired by those same shady developers. It could sink another 100 feet - which would be fine, the big problem is if it falls over. Real China Kwalitee there guys.
At least for once the victims are also rich tossers.
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Saturday 26th November 2016 00:36 GMT MNGrrrl
> At least for once the victims are also rich tossers.
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That's not a helpful attitude. The same design process that put up this skyscraper is also behind the skyscraper you go to work in, the stadium you see your football in, the train station you wait for your ride home at, and more. You may laugh now because the "rich tossers" are getting screwed, but what happens when the skyscraper you're working in falls over during an earthquake and pancakes you? Are you going to have the same happiness about *that* engineering failure?
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> the developers were too cheap to sink the piles all the way down...
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Yes, cost is a consideration in almost all engineering projects. Was it necessary to sink the piles all the way down, given the results of the site survey and proposed design? The slide rulers said no at the time. Hindsight is 20/20.
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> and now they're saying they don't even have to fix it, they can just let it sink and it'll stop eventually.
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Buildings are usually over-engineered to provide for a safety margin. Bridges, for example, may be rated to hold 100 tons, but may in fact be designed to hold 200 tons, to account for unexpected load. Subsistence is also calculated ahead of time, and a safety margin is present there as well: All buildings will sink. They build it so that it can sink farther than expected and still be safe. In fact, the Japanese built an entire airport on a man-made island that is sinking at many centimeters per year... and all of the structures there are built on jacks. It's actually quite remarkable. So if something sinks more than expected, that doesn't mean the safety margin has been exceeded. Hence, nothing needs to be done, provided this new behavior is thoroughly understood. Is it? I don't know, but it's not necessarily a wrong answer.
> But there's no reason to believe that 31 inches is an actual limit - that was an estimate from an engineer hired by those same shady developers.
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All engineering disciplines use estimates, rules of thumb, and the like. There's every reason to believe that engineer: If he's wrong, his career might be over. As to "shady developers"... you know, when something goes wrong, it's usually not due to malice but incompetence or ignorance. You can't scream "Illuminati!" whenever anything goes wrong. Car didn't start this morning? IT'S A CONSPIRACY! Or, maybe it's just been 7 years since you last replaced the battery... something you might have overlooked.
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> It could sink another 100 feet - which would be fine, the big problem is if it falls over.
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Having a building descend 100 feet into the ground at the center of a major city when it was built to sit on top of the ground is never "fine". I've watched movies where that happens, and played video games. It rarely ends well for the people living in said city. Usually there are demons, fire, aliens, or other things that tend to drive down property values to go with it.
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Saturday 26th November 2016 07:02 GMT Brian Miller
Yes, cost is a consideration in almost all engineering projects. Was it necessary to sink the piles all the way down, given the results of the site survey and proposed design? The slide rulers said no at the time. Hindsight is 20/20.
According to the San Francisco Magazine article, this type of building had been rejected before:
At around the same time Millennium Tower was moving toward approval and construction, developer Jack Myers submitted plans to erect a skyscraper at 80 Natoma, just two blocks away from the Millennium’s site. It would, like the Millennium, be a poured-concrete structure, though a daintier 52 stories instead of 58. As described by then–DBI director Frank Chiu in 2004, the proposed tower at 80 Natoma and the ground upon which it would have stood reads like a mirror image of the Millennium: It would be “thin relative to its height,” “built on soft soils that are subject to compression, and supported on short piles that wouldn’t reach the bedrock 190 feet below.” Also, it would be “an extraordinarily heavy structure.”
Sans in-house rocket scientists, Chiu called in outside experts for detailed analysis on 80 Natoma. After a full peer review of the building, its foundation, and the soil, Chiu wrote that the experts had determined that “the building could settle an alarming and unacceptable 9–11 inches.”
The maths were already done on a similar building, in similar conditions, practically next door. It was rejected, and for good reason. Somebody important in the city planning office knew that the Millennium Tower would have severe problems after it was constructed.
Just because a building is "constructed to code" doesn't mean that the finished build will be safe. The building leans, and may have to be torn down.
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Saturday 26th November 2016 07:29 GMT MNGrrrl
> The maths were already done on a similar building, in similar conditions, practically next door.
Two blocks away marks the start of landfill. It was a swamp before. All you've done is pointed out why engineers do site surveys before they build: Because the geology even "right next door" can be radically different. It's a very good thing civil engineers don't have the accumen of internet pundits, or the first wood pecker to come along would destroy civilization...
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Sunday 27th November 2016 14:57 GMT harmjschoonhoven
Re: Welcome to the club
But the Dutch know how to build on soft soil. The Royal Palace in Amsterdam was built as a town hall between 1648 and 1665 on 13659 wooden piles. It is still erect and in perfect condition standing on that same wooden piles (minus two, taken out for inspection) protected by groundwater.
Controlling groundwater levels is essential in the Netherlands, especially in the parts that are below sea level. For that they have elected councils with a tradition going back to the 13th Century.
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Sunday 27th November 2016 19:32 GMT Anonymous Coward
Re: Welcome to the club
But, and I think this is an important point, the Dutch do not have to worry about magnitude 7+ quakes hitting them. Just remember that SF is right where the San Andreas fault can clobber it - in fact that is exactly what happened to the city a little over a century ago. Also (before someone decides to mention it) the SA fault does not run through the city - it actually takes the scenic route through the bay. Major SA quake on the SA fault = tsunami right up the San Joaquin valley. Not fun!
Saying that, I remember hearing that LA was once described as "a city waiting to die".
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Monday 28th November 2016 15:05 GMT breakfast
An interesting way to destroy civilisation
This really made me smile and I absolutely don't want to make you feel like I'm saying this in a mean way because I genuinely love it, but there is a noticeable difference between a woodpecker and a wood pecker.
If you're talking about a bird, you probably mean the former...
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Sunday 27th November 2016 06:10 GMT bazza
In fact, the Japanese built an entire airport on a man-made island that is sinking at many centimeters per year... and all of the structures there are built on jacks. It's actually quite remarkable. So if something sinks more than expected, that doesn't mean the safety margin has been exceeded.
Kansai Airport has sunk far more than expected, and there is some nervousness that it won't stop before it sinks beneath the waves. The building jacks keep them level, but won't keep them dry.
The loss of Kansai airport would be hugely problematic; they're planning on closing Itami airport in nearby Osaka, leaving just Kobe's small airport as backup. Basically the whole region needs Kansai airport to stop sinking.
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Sunday 27th November 2016 19:31 GMT MNGrrrl
> Kansai Airport has sunk far more than expected, and there is some nervousness that it won't stop before it sinks beneath the waves. The building jacks keep them level, but won't keep them dry.
There isn't any nervousness. Yes, it's sinking more than expected, but there was a high degree of uncertainty in that project: Nobody has tried something like this before. They can remove the jacks and sub-flooring if needed and add bigger jacks. The airport has a sizable boundary around it so they can add more landfill in without disturbing the buildings. There are contingency options here because while the best estimates they had said it probably wouldn't be needed, there were a lot of unknowns in the model. I have no doubt the airport will still be there in 30 years. I don't know what will be needed to keep it there, but it's not like Godzilla is going to crawl out of the ocean and eat it.
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Monday 28th November 2016 04:03 GMT Pompous Git
Well, not since Atlantis, you can find the original engineer's report and planning permission buried in soft peat at the local planning office.
OTOH if you're frightened of leopards Tall building foundations: design methods and applications from Innovative Infrastructure Solutions December 2016.
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Monday 28th November 2016 22:08 GMT Pompous Git
Not forgetting all the cleaners, security guards etc who'd be in the building and are definitely not rich by any Western standard...
When The Git pointed out that they aren't "rich tossers" his post was downvoted, then deleted by the moderators. In <El Reg's</i> New World Order, they appear to be deemed "rich tossers". Not The Git's world...
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Monday 28th November 2016 06:14 GMT bombastic bob
"the developers were too cheap to sink the piles all the way down"
considering it's San Francisco, I offer these possible excuses:
a) endangered gophers/moles preventing a proper pile-drive
b) the term 'pile driver' was considered to be an epithet and summarily struck from the list o' instructions for proper building construction
c) too much dope smoked on the job
d) they wanted a NEW tourist attraction: the 'Leaning Tower of Frisco' [note S.F. area residents *HATE* it when you call it 'Frisco']
e) gummint corruption allowed improperly inspected construction
f) it was NOT built by Trump [I had to throw THAT one in there!]
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Friday 25th November 2016 23:45 GMT MNGrrrl
Not the developer's fault.
If you dig into it you'll find out that the site survey and build was done to all engineering standards; The problem is that, after the preliminary design and survey work, and construction had started, the city decided to start building a new transit station nearby. This involves dewatering -- pumping water out of the foundation so that it can be compacted more easily, and there is less settling in the foundation. The problem is, the way they are dewatering is that it removes water from everywhere nearby, not just the area directly under where the new transit center will go. As a result, the sand under the Millenium Tower is compacting at a highly accelerated rate, and it is doing so unevenly.
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Now yes, there is finger pointing over who knew what, when, and all of that, but this is not a design flaw. This is not an engineering flaw -- when the designs were approved and the survey completed, everything was done by the book up until that point. What has happened here is a external and unanticipated factor.
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As to building foundations down to bedrock -- while yes, that could have been done, there was no need. Many, if not most, of San Francisco's buildings, do not have foundations that go all the way to bedrock. In fact, in an earthquake-prone area, this is often a *bad* idea because during a quake, all of the wave action will be translated via those concrete pillars directly to the building. You have to build in extra dampeners, possibly a counter-weight / pendulum system, to absorb all of that extra mechanical force -- which isn't necessary if the foundation doesn't get nailed into the bedrock... Instead, the sand, gravel, etc., absorbs that stress and there is less mechanical force being forced into the building structure.
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So I need to be absolutely clear here: The building's design, including foundation, and the surveying done ahead of time to ensure it would be sufficient, was done to textbook. There were no flaws. The flaw here, is that something was built right next to it right after it went up -- before it had a chance to settle naturally and compact the foundation evenly. All buildings settle, even skyscrapers. There are models to predict how much and how long it will take (Typically, it takes about 20 years before it becomes insignificant).
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Now, all that said, this is a classic case of tragedy of the commons: If your property has a drainage ditch that prevents flooding for your neighbors' properties, and that drainage ditch becomes obstructed somehow, are YOU responsible for fixing it, or are the people benefiting from it (ie, your neighbors)? This is a very simplistic example, but it's fundamentally what this entire affair boils down to: Transbay dewatered the area for its own project, and in doing so, led to the problem the Millenium Tower is facing. Who knew what, when? We probably won't know for a long time. But ultimately, this is a question of who is going to pay for the foundation to be reworked. This could cost $10 million dollars, or much much more -- it varies by site and building, but a similar problem has happened in Brazil, known as the Leaning Towers of Santos, and it's over a hundred buildings all suffering from the same problem. That's about the cost for these smaller apartment blocks, per building... and so far, nobody has stepped up to pay for it; Though, when they were built, subsistence was not as well-understood as it is today.
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Saturday 26th November 2016 00:01 GMT Anonymous Coward
Re: Not the developer's fault.
"So I need to be absolutely clear here: The building's design, including foundation, and the surveying done ahead of time to ensure it would be sufficient, was done to textbook. There were no flaws. The flaw here, is that something was built right next to it right after it went up -- before it had a chance to settle naturally and compact the foundation evenly. All buildings settle, even skyscrapers. There are models to predict how much and how long it will take (Typically, it takes about 20 years before it becomes insignificant)."
Based on what?
1) If you read the articles it clearly states that there was no comprehensive design review done because the developers refused to do one and the planning department didn't think they could for the to.
2) This building is uniquely heavy given its small footprint and the decision to use concrete instead of steel (equivalent to a 150 story steel building).
3) It had sunk almost 12" before Transbay started construction, 50% more than the lifetime projected amount the developer's engineers had predicted.
4) It's tilting AWAY from the Transbay construction, the developer is attempting to argue that the de-watering is causing it to tilt in the opposite direction WTF?
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Wednesday 30th November 2016 17:11 GMT allthecoolshortnamesweretaken
Re: Not the developer's fault.
- "here is a leaning high rise, very noticeably so, in Vancouver BC. I believe they solved the problem by freezing the underground."
- "I suspect that particular solution is a lot easier to achieve in Vancouver than San Francisco."
Not at all, as long there is some water in the ground that you can freeze. The technology is availiable, tried and tested. The energy bill for keeping the refrigeration units running 24/7/365 for as long as you want to keep using the building, however...
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Saturday 26th November 2016 00:48 GMT Pompous Git
Re: Not the developer's fault.
If you read the articles it clearly states that there was no comprehensive design review done because the developers refused to do one and the planning department didn't think they could for the to.
I somehow don't think San Francisco is in the 3rd World. Developers hire accredited engineers to design buildings to comply with the Building Code. The City employs or hires Building Surveyors who certify that the design either complies with the Code, or is "Deemed to Satisfy" the aims of the Code. Only then is a Building Permit issued and building commences. During construction, Building Surveyors (often called Inspectors at this stage) visit the site to ensure that the building is being erected as per the design and including any special instructions issued with the Building Permit.Blaming the developers is a big stretch unless they suborned the Engineers and/or Building Surveyors. If the latter, then they are culpable since this is professional misconduct.
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Saturday 26th November 2016 01:23 GMT MNGrrrl
Re: Not the developer's fault.
> Blaming the developers is a big stretch unless they suborned the Engineers and/or Building Surveyors. If the latter, then they are culpable since this is professional misconduct.
First, I agree with everything else you've said. But this isn't and either/or conclusion -- the amount of oversight by the government varies considerably from one municipality to the next, and most of these agencies are criminally underfunded. These agencies provide almost no additional safety. Example follows.
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One of the worst building engineering disasters was the collapse of a pair of walkways inside a multi-story hotel: Until 9/11 it was the worst structural collapse in US history. The hotel had about 800 rooms and was maybe 20 stories tall -- The building inspection for the site took less than 15 minutes. It was eventually determined that the engineers were responsible, that this was a bona fide design flaw, but despite dozens of people being involved in the project, numerous government agencies, and other safeguards, a very obvious structural flaw was overlooked.
My point here is that the majority of the safety of buildings comes from good engineering practices within the companies doing the work. There is no real oversight or auditing beyond that, so unless there was a very obvious flaw it is unlikely inspectors would discover it. Corruption might be a problem if there was any real risk of a project being stalled out by such a problem getting discovered... but the odds of it happening, realistically, are about nil. The inspectors are overworked to the point of being ineffectual.
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Saturday 26th November 2016 01:39 GMT Pompous Git
Re: Not the developer's fault.
There is no real oversight or auditing beyond that, so unless there was a very obvious flaw it is unlikely inspectors would discover it... The inspectors are overworked to the point of being ineffectual.
Third World it is then. I am surprised, especially since Merkins are less than hesitant to describe Tasmania as "Third World". The last five years of my working life (to my everlasting shame) I worked in the civil service (Building Compliance). -
Saturday 26th November 2016 07:08 GMT Anonymous Coward
"Wave action translated by concrete pillars"
Source please? I smell bullshit from the building's developers being swallowed whole by a gullible Reg commentard.
It is well known that loose material such as soil, sand and gravel becomes HIGHLY unstable during an earthquake due to a process known as liquefaction. That could mean the difference between the building getting a big shaking and swaying (as tall buildings are designed to do) during a quake, and a building suddenly dropping dozens of feet as it and its piers act as if all that sand and gravel has been magically transformed into water. Even if it remains standing I think you can guess the result would be far worse than getting "wave action translated by concrete pillars" embedded in bedrock.
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Monday 28th November 2016 01:21 GMT Pompous Git
Re: Not the developer's fault.
a structural design change was made for aesthetics. So in that case yes you cane blame the engineers for no recalculation load strength.
Aesthetics is the province of the knarchitects*, not the engineers. If the knarchitects never passed the revised drawings to the structural engineers, why would you blame the engineers for failing to anticipate those changes? Makes more sense to blame the Building Surveyors who accepted the design change without revised engineers' drawings.* knarchitect is an engineer's term for them that make pretty pictures.
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Saturday 26th November 2016 04:31 GMT Anonymous Coward
Re: Not the developer's fault.
There seems to be a lot of ignorance here about the effects of different terrains on earthquake damage. The fact is that a thick layer of soil (or landfill) between bedrock and the buildings does not "cushion" the waves, it amplifies them.
Generally structures sitting directly on bedrock do much better than those on fill or soil. Damp soil is the worst because of liquefaction, something less likely in this case due to that dewatering thing.
I only know about this stuff because of where I was raised: Southern California. Whole lotta shakin' goin' on there...
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Saturday 26th November 2016 07:21 GMT MNGrrrl
Re: Not the developer's fault.
> There seems to be a lot of ignorance here about the effects of different terrains on earthquake damage. The fact is that a thick layer of soil (or landfill) between bedrock and the buildings does not "cushion" the waves, it amplifies them.
This is why I generally shake my head and mutter whenever someone from Southern California tries to sound edumucated. The other 47 states on the continent keep praying you guys fall into the ocean so as to rid us of your stupidity, but the geologists keep telling us it's going to take too long. Sigh. So here we go again, from the top:
*** There is no bedrock in the San Francisco bay area. ***
************** 404: GEOLOGY NOT FOUND. **************
Bedrock sounds like a really nice, reassuring word, and of course everyone wants to know why every building doesn't simply drill down to bedrock. Well, there's a simple engineering answer: It's not necessary. Foundations in a building serve only one purpose: Load spreading. And the method used for constructing the tower is a proven one: Friction piles. To understand how they work, take the wooden handle of a broom and push it into the ground. Hammer it in, if you want. You're not going to get very far down, and that's just dealing with the topsoil and clay in your backyard. Friction piles operate on the same principle: They're just a lot bigger. They will easily support the weight of many, many tons without moving, because the static friction along the sides keeps it from sinking. That's how the Millenium Tower was built, and it's solid engineering practice. And there is zero risk of liquifaction here: The foundation is irrelevant, the geology of the site isn't suseptible to it unless you have an earthquake of a magnitude that would wipe out pretty much everything except a military bunker.
I have said it before, and I will say it again: The design is solid, and the site survey was done properly and to best practices. What was *NOT* done correctly was the dewatering of the whole area, which radically changed the friction and compressibility of the soil under the tower, and that's what has caused it to sink and tilt. There is no disagreement about this amongst engineers. You can't expect the engineers to have anticipated that, after construction, the next door neighbors would fuck up the geology under the building like this: Their dewatering has dropped the water table by over 20 feet. The piles that previously were in the water table are now sitting above it. Water tables do not simply drop by 20 feet in a coastal area in the span of a few months. It's not a natural process.
So please, stop acting like you know something about engineering: You don't. And as far as the waves being amplified: Learn the difference between primary and secondary waves, because one induces compressive load and the other shear load. If you build down to bedrock, your piles need to be able to withstand both as first-order effects. If you don't, the piles only need to worry about compressive load because there won't really be any sheering... the building will move with the earth underneath it (which it wouldn't, if it were nailed to the bedrock). Though in practice, all of this simply means tweaking your concrete mixture... the design will be the same.
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Biting the hand that feeds IT
