[...] Millennium Tower – a luxury condominium where star athletes and retired Google employees bought multimillion-dollar apartments before they realized it was sinking – is continuing to sink and tilt to the side by about 3in (7.5 cm) a year, according to the engineer responsible for fixing the troubled building. — The Guardian
At that rate, the building’s elevators and sewage systems would cease to function within a few years according to engineer Ron Hamburger’s report to the city’s municipal Board of Supervisors last week. He also told the 11-member body that the movement was inevitable, adding that, based on his observations, the degradation would continue “whether we are conducting work at the site or not.”
Hamburger did reportedly declare the building safe for use, however, stating that the placement of 18 steel piles in the bedrock of the structure would help significantly increase its stability.
The 58-story Handel Architects-designed tower became a headache for the property managers shortly after opening in 2009 to considerable fanfare. Repairs had to be halted back in August after it was discovered to be sinking at an accelerated rate just weeks after the $100 million rescue scheme had begun. The sinking process has thus far reaped a lot of unwelcome consequences, although some inventive onlookers have been more opportunistic where the opportunity arises.
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Hmm, How do we reconcile (1) and (2) ? Building is "Safe" but no elevators and sewage systems? Looks like it is safe as a monument, not for human habitation. Our Own Leaning Tower of San Francisco for tourists to come, gawk and take funny pictures.
(1) At that rate, the building’s elevators and sewage systems would cease to function within a few years according to engineer Ron Hamburger’s report to the city’s municipal Board of Supervisors last week. He also told the 11-member body that the movement was inevitable, adding that, based on his observations, the degradation would continue “whether we are conducting work at the site or not.”
(2) Hamburger did reportedly declare the building safe for use,
Do you understand how time works?
#1 is about the future. #2 is about the present. The statements are easily reconcilable when you understand that.
Currently safe, but at this rate will become unsafe. Not sure you have to be such a dick about it, EA.
Fair enough. At some future point when it is no longer currently safe, I'm sure the engineer's report would state differently. At the time the report was issued/presented (reported as last week) it would be perfectly reasonable to say that both statements are true to the best of the engineer's understanding and you've summed them up quite nicely: "Currently safe, but at this rate will become unsafe [within a few years]." No reconciliation needed because any person grasping the concepts of past, present, and future would understand that.
Right now, if they can not fix this in 6 months, it needs to be ordered condemned to be demolished/deconstructed. If it was me, the site will also have to be decontaminated of any contaminants that may exist on the site to EPA's and California's strictest environmental standard.
Without commenting on the seeming inconsistency alleged above, I see a separate (albeit related) one:
"Ron Hamburger added that the degradation would continue whether we are conducting work at the site or not."
"however, the placement of 18 steel piles in the bedrock of the structure would help significantly increase its stability."
Well, wait a minute. Is the tilting going to continue, or isn't it?
Quotes from the linked Guardian piece:
"'The building does continue to settle at a rate of about one-half inch per year and to tilt at a rate of about 3in per year,' he told supervisors last week. 'It is doing this whether we are conducting work at the site or not.'"
The building is sinking and tilting. It will continue to do that until it stabilizes. Placing the steel piles to bedrock will help it stabilize.
"Hamburger told the San Francisco board of supervisors in an update hearing last week that the building remains safe and that installing 18 steel piles to bedrock is the best way to stop the tilting and possibly reverse some of it, KNTV-TV reported."
There is potential concern that doing work on site could make the problems worse.
"Work to reinforce the building’s foundation came to a halt last summer, after engineers discovered the building had sunk an additional inch in the months since the attempted repairs[*] had begun."
Doing nothing isn't going to stop the sinking and tilting. It continues until it is stabilized. Attempting to stabilize it with the piles is apparently the engineers recommendation to stop the tilting and possibly reverse some of it.
*The attempted repairs are not the 18 piles to bedrock being currently discussed:
"In May, crews started work on the perimeter pile upgrade project to install 52 concrete, 140,000lb piles to anchor the building to bedrock 250ft below ground. Shortly after work began, however, the sinking and tilting accelerated; the building now has a tilt of 22 inches, NBC Bay Area reported." (Different Guardian article)
"The building is sinking and tilting. It will continue to do that until it stabilizes. Placing the steel piles to bedrock will help it stabilize."
Why are they not done yet? I agree, doing nothing is not an option. Personally, I would have the tower deconstructed and then have the foundations done right and then rebuild it. This is sketchy at best.
Until it has stabilized and stop sinking and tilting, it is premature to call it safe.
Aaaaand that's why they are paying the engineer for his opinion and not paying you for yours.
"The building is sinking and tilting. It will continue to do that until it stabilizes."
Or falls over.
The building is sinking and tilting. It will continue to do that until it stabilizes or falls over.
E_A, I hope it stabilizes but until it does, there is still a legitimate risk of it falling over. Is the piles going to be enough and not buckle. Even engineers get it wrong. Ever watched "Engineering Disasters" TV show?
If it fails, it'll be a future episode of that series or one of the series like it.
At some point they are going to start talking about how to demolish the building
That is technically what they should have done. At least dismantle it so not as much building material is wasted. Then they could reconstruct it or even if only at 1/3 to 1/2 the height after ground and foundation work is redone and done properly. Then the excess material used on another site or two for another building(s) that won't be excessive in weight.
You're gonna need a bigger shim...
Bet they're all secretly hoping for a big earthquake to knock it down so they can invoke the act of God clause
Oh darn. Some entitled ass hat owners of 5 million dollar condos are going to have to move within the next few years. They might even take a loss. Boo hoo. They will be fine.
You act like the rich asshats deserve this - why? Because they have money? More than you so they are entitled? This same event type occurred to friends of mine who bought a $250,000 house in the Denver suburbs a decade ago... the soil just started falling away on their sloped lot. I'm sure they deserved it too... This isn't about the tenants.
I would wager large sums of money (yeah, rich people amounts) that you won't see a payoff for your defense of the rich, Bill. You defend them for free and they think you're nothing.
On one hand, I couldn't care less about the financial impact of this on anyone involved. On the other hand, I have HSW concerns that also apply to the villainously wealthy .
I'm concerned about it falling over. If it keeps sinking without tilting, I wouldn't be as concerned but its tilting which means it's overturning and that will means it will collapse on to other structures and any person underneath.
The "villainously wealthy" are very rarely villains...much much more likely to be contributing a lot to society.
They'd likely contribute as much, or very nearly as much, with a tenth of the wealth. It doesn't scale linearly and it doesn't justify the wealth.
This is my opinion:
First off, the proper thing should have been to dismantle to building and store the building material somewhere, redo the foundation properly and put the piles in to a depth of 250 to 300 ft. down... then reconstruct. The fact it is still sinking is the problem. Trying to put piles under a building while that building is erected insitu is problematic and lucky if successfully done. They should have dismantle to building and redo the foundation. Of course, the proper thing truly would have been to have done this right the first time.
Yeah, that's how construction works... /s
Ricky, I can only think of a few buildings where this was done, but a skyscraper, never. Do you know they could probably build another structure in the time it would take to do what you suggest? Yes, I realize I'm likely to get a dissertation from you, so please, just nod your head, and agree with me.
Sure they could. If they don't dismantle it, it may very well dismantle itself at the cost of lives and damage/or destruction of property. I agree with you but also it's very rare that a skyscraper would be in this situation in the first place. There's that building in Las Vegas.... https://en.wikipedia.org/wiki/The_Harmon
I'm suggesting dismantling as an option. Outright careful demolition, maybe... but even then it might require taking it down to about 1/2 its height through a deconstruction process before imploding the rest due to it sinking and tilting.
Regardless of the intent and residents, failure of this sort weakens our sense of the overall built environment and of the world in general. I'm getting really tired of things not working out.
Experience the future now in the first ultra-luxury high-rise building in San Francisco.
Ummmmm. From the Millennium Tower website.
https://millenniumtower-sf.com
Are they ever going to find out the cause, who made what mistake? I know for a long time building up in SF wasn't considered a good idea. I also know they faulted weakening of the ground from an adjoining excavation for another project, but don't know if any credence can be put in that or why it wasn't anticipated.
Any precedents of similar in the US?
What is the moral of this story?
The architects and engineers screwed up. They didn't do a proper soil study of the soil conditions in a grid fashion across the area. The soil is not of the soil bearing capacity for a structure this tall. It's like 2-3 times the relative height/weight (weight is key here more then height but its relative to the materials used). Additionally, the soil weakens over across the site... hence why it's overturning (tilting). It's not uniformally able to support the weight of the building. Like the image you shown below, it is clear the existing concrete piles were not even close to the depth it needed to be. For a building of this weight, ALL piles should have been taken all the way to bedrock. You should not build buildings over 10 stories tall on clay soil with piles only going into clay.... let alone 58 stories. You might be able to get away with 15 stories but 58 stories is just a bit too far. In clay, the pile depth should be no less than 50% of the building's height. It's not unusual in sandy-silty-clay soil that was a former bed of a bay like the San Francisco Bay, much like the river bed of the Columbia River where piles can be as deep (or deeper) as (or than) the building is tall unless you reach solid bedrock beforehand.
Unfortunately, the Millennium Tower is not an anomaly within San Francisco. As noted by the San Francisco Chronicle, stretches of the downtown area are sinking at a startling rate of approximately three-quarters of an inch annually. Increasing sea levels are expected to further degrade the clay soils the city is built atop, and exacerbate the rate of sinking.
But for now, development in downtown San Francisco will continue unabated as a spate of projects, ranging from Henning Larsen’s Mission Rock to the HOK-designed 725 Harrison Street, come online.
pic and text from:
https://www.archpaper.com/2021...
"Buildings like S.F.’s Millennium Tower are causing the Bay Area to sink under their weight"—headline form the SF Chronicle link. I can't access the text.
The 1989 Loma Prieta earthquake was only a 6.9 magnitude. The 1906 earthquake was a 7.9 magnitude (or larger depending on what analysis you look at). All these towers are going to get absolutely mangled in the next big one. Why the fuck would the city allow these to be founded on anything other than solid bedrock?
Exactly. The piles would need to be as deep to 1.5x deeper than the building's height if there was no bedrock but all piles should have been driven into bedrock and given the height, it should have been driven at least 20% of the building's height into the rock as rock anchoring given the seismic nature of that location. Engineers might be able to math out some idea of being able to do it in less but that's minimalism that I wouldn't stand by. Foundation is the most important part. If foundation is crap, it doesn't matter what you build on top of it. I maybe a building designer but in Oregon, I can theoretically design a single-family dwelling that is a high-rise and if I was designing a house under that kind of soil and seismic environment, I would be using piles. Even for a three story house, piles maybe called for due to the soil conditions of a site location and they can potentially be deeper in depth than the height of the dwelling. I can understand a skyscraper is going to demand very deep foundations especially one that tall in that soil.
"Hamburger did reportedly declare the building safe for use"
'_________ safe for use'.... infamous last words. How is a building that is sinking and tilting safe? Safe for use.... you are quacked. If you mean, its safe for killing. You might as well evacuate everyone within 600 ft radius of this building... especially in the direction of the building is tilting along a +/- 45 degree arc along the predicted center line of that overturning structure and evacuate everyone within 300ft. in the remaining 270 degrees around the building.
I'm making a separate comment to say this so the mods can hide or nuke it separately from my other comments and other threads if they want to...
Rick (rcz1001), calm down. You're not a licensed architect nor a professional engineer. Your opinions and comments are trending more and more outlandish with each new one you offer, and it may seem to others who don't know who you are, that your opinions could carry some weight or validity. Stick to what you know so you don't mislead anyone.
I, for one, really want to see Rick design a single-family highrise in Oregon. Call it an independent thesis project.
A building that is sinking and tilting is not a good sign. It's a matter of time that it will fall over and kill people. San Andreas fault line is a strike-slipe type fault and has had earthquakes in the magnitude 7.0 and higher level and the tower is literally within mere miles from the fault and soil is subject to liquefaction.
Anyone capable of 5th grade math knows the building that is sinking and tilting is unsafe. The only reason the Tower of Pisa hasn't collapse is observable in its construction and the pace in which it was constructed facilitated with little changes just enough that they were countering the lean in the specifics of how they were building the tower. They didn't do those things on the Millenium Tower that the builders of the tower of pisa did. Therefore, the Millenium Tower is precisely at risk of literally falling over (overturning) as it is sinking.
A major seismic event of 7.0 or higher and resulting liquefaction can be all that it takes for this tower to littlerally fall over onto other buildings and causing them to collapse or have serious damages and people killed and/or injured seriously. I don't call this a building safe to be used when you start adding more weight and moving weight at that.
I am not sure the proposed fixes are adequate yet. Until it's stabilizes and stops sinking and tilting, it is not fixed yet and it is not prudent to say it is safe.
Rick (rcz1001), calm down. You're not a licensed architect nor a professional engineer. Your opinions and comments are trending more and more outlandish with each new one you offer, and it may seem to others who don't know who you are, that your opinions could carry some weight or validity. Stick to what you know so you don't mislead anyone.
I don't have to be either to know more and better than the idiots that designed & engineered this building. RULE #1 Do NOT exceed bearing capacity of soil or bedrock that will be supporting the structure in which you propose. RULE #2, ALWAYS MAKE SURE THE SOIL CONDITIONS ARE ADEQUATE FOR WHAT YOU PROPOSE. RULE #3, ADHERE TO RULES #1 & #2. Rule #4 - If you can not meet Rule #3 with what is proposed then change what is proposed into one that adheres to the requirements of Rule #3.
Rule #5, All RULES #1-4 shall be met before a single picogram of the structure (including the foundations) is built and put on site.
Rule #6, if site can be altered to meet the requirements so that Rule #2 can be met then site shall be properly altered, prepped, and verified that it adheres to Rule #2's requirements before any foundation or any other construction work takes place.
Come on, people! Don't underestimate the positives, like increased tourism opportunities (eventually).
I rather we avoid something like this:
Like this one:
https://www.youtube.com/watch?...
Something with video links not working right.
The URL should work but trying to embed the video... not working.
This YouTube shows the evolution of high-rises in SF over the last hundred years or so. Well made, about two minutes. I got curious.
Well, if Jamie Dimon can have the signature building of JP Morgan/Chase torn down on a lark after spending a gazillion dollars upgrading it to Platinum Leed then the owners of the SF train wreck can have it taken down also.
Screenshot from the YouTube video I linked above. The Millennium is among the dark blue buildings by the logo, top left. The pyramid pokes up above the box on the right. I'd be curious to see a matching soil map.
sell fast and get out of that cesspool of SF
For anyone still curious—
This YouTube gives a very basic—I need basic—and graphic overview of the decisions made, possible causes, and about 8 minutes in, a full explanation of the fix.
52 posts were to be sunk to bedrock just outside the perimeter and around the sinking corner and notched into the foundation, then the building lifted, maybe, by the jacks. But I see they have decided as few as 18 posts are needed, and I'm not clear whether this has been finalized on not. They're still in the process, I think.
He also gives a more detailed soil map:
He gives credence to the claim excavation and water drainage from the nearby project unsettled the soil and exacerbated, if not caused, the problem, but even if so, I don't know where that leaves us.
Elsewhere, concerns about the engineering firm sharing information from work that summer about what happened:
Records that experts say could shed light on what caused the Millennium Tower to sink and tilt so much last summer are missing, NBC Bay Area’s Investigative Unit has learned.
https://www.nbcbayarea.com/inv...
I've also read questions about oversight of the firm with those actually doing the refit.
Another site says there simply hasn't been much study about the cumulative effect of the weight of all the construction the last decades on SF, billions of tons.
I'm an amateur and can only hold my breath, but we're wading further out in to the unknown, maybe living on borrowed time.
I forgot the link for the YouTube: https://www.youtube.com/watch?v=ph9O9yJoeZY
I always love getting asked, "How much does your building weigh?"
To round this out, another site said that consulting engineers did recommend going down to bedrock but were not followed. It also said that another large building proposal in a nearby area was axed by peer review because of the same concerns. Millennium, however, bypassed peer review (I don't understand the process). The project may have been flawed from the start. Millennium, however, was obviously convinced their solution was adequate.
There's no way I can jump in with an opinion, though obviously mistakes were made. I just wanted to know what happened and why, and finding an answer may be as difficult as building on sandy soil. Truth has become a legal matter, where we won't get full answers.
This solution just astounds me—and I remain incredulous. They are going to lift a 60 story building at the edges—
Rescue efforts are about saving the financial interests in the building. This is not be be confused with actually saving the building but rather with getting the building to a point where the financial liability is minimized. These are not one and the same, and the public (city of SF) has already "contributed" some $100m to the rescue effort. Any real cost benefit analysis would have called for the physical demolition of the building and economic demolition of the developer.
Any sensible public health, safety, and welfare analysis would have called for demolition of the building. Financial welfare of the developer should never be a factor of consideration when it comes to government officials ruling if the building is to be demolished and order it done. Apparently, HSW isn't a concern anymore except by a small subset of licened professionals and some non-licensed professionals who gives a f--- about HSW issues.
If so, Miles, those financial efforts may be as iffy as the original construction and the attempts to repair it. More good money after bad. They have cut costs on the refit which are still expensive, though, and we don't know if it will work or not.
I have absolute confidence they didn't want to build a weak structure. The story I suspect and want to hear but can't prove is that financial interests led to questionable decisions all the way. I heard, for example, they bypassed peer review to save time, a matter of a year or two, which would have cost them money: the time was ripe to hit the market and cash in. And full support, down to bedrock, would have been very expensive.
There's a metaphor in this, of course, about our times.
The Shoreham Nuclear Power Plant was built despite widespread oppositon influenced by Three Mile Island and Chernobyl. The original budget of $65 million turned out to be just 10% of the final $6 billion cost. The plant was fraught with problems ranging from mob control of construction to design and construction failures. It was run at low power (legal without a license), contaminating the facility in an attempt to force the NRC to grant an operating license that was subsequently denied. Long Island Lighting Co. (LILCO) was taken over by a public utility that bailed out bondholders at 100% via massive rate increases.
I am pretty certain no one intentionally make decisions with the intent to have a sinking and overturning building. No one shy of a absolute lunatic would do or think such a think. It's dubious decisions like when they got a bid result for 300+ Ft. deep piles that it was more than what the developer was willing to spend so corners were cut in the vain hope that with shorter piles, that it would still work. Stupid... yes. Criminally malign intent to kill people... no. I doubt that. It's like a lot of decisions to cut corners.
The best cost cutting that would have save the mess with shorter piles is to also not have as many floors which would reduce the weight. The issue isn't total weight but concentration of weight going down piles. Deep piles like what was implemented but didn't go all the way to bedrock is based on friction. Hence, FRICTION PILES. The soil friction to the piles' surface ability to resist the sinking force (mass and force of gravity... thus weight of structure). Conventional wisdom is to spread the weight load so the weight is less than soil bearing. At this height, there is no way you would get that but you you can support more weight via friction resistance on deep enough piles than the soil's normal soil bearing capacity per square foot. Therefore, you use friction to resist sinking.
The problem is, this building's height, and weight is excessive than what the shorter piles are able to support via friction resistance. Hence, it's sinking. It's tilting probably due to inconsistency in the soil sufficient enough for the lean to occur.
Piles that goes down to bedrock works on a different principal a little bit. If you have competent bedrock like thick solid granite or basalt bedrock, it would have much heigher bearing capacity and the piles it's becomes about cumulative compressive strength of the solid rock as a footing to the piles and naturally consolidated bedrock would ultimately in its molecular structure spread the load over a larger area than the pile.
However, at this depth, the pile diameter to pile length (depth if you want to think about it) should be pretty stout. If it's too small of diameter, it might possibly buckle under a seismic event. Piles at that point would act like columns and it's the axial load. I am not sure if the "solution" is thought out well enough. It is not the number of piles that matters because a larger diameter but a little bit fewer piles maybe better but it's the cumulative capacity. Piles going to bedrock becomes more like columns and thus axial load capacity. What will be important is the piles don't buckle under a seismic event.
At say... 350 ft to anchor into bedrock to about 25-50 ft. an 18" diameter pile might be too slender for this length because you won't necessarily have lateral bracings and only have the softer clay soil to supposedly keep your pile in place.
So, we can only hope they didn't f--- up on the solution. Failure will be potentially catastrophic. It is a concern and still is for people in that area. Until it's fixed, it's still a high risk and no where close to being rationally deemed safe for its intended use. That's a premature statement that a professional should not give at this time.
The math behind how to calculate surface friction on the piles isn't something I want to go into. What I can read is the reduced number of piles would be 24" diameter piles. As it needs to fit inside the 36" steel casing. Previously, the 52-pile remedial proposal also used 24-inch piles. This raises concerns because it the idea was to use 52-piles of 24-inches to support the building, how is it reducing it to 18 piles of the same diameter going to be sufficient? If you are going to reduce number of piles, they need to be be increased in diameter to have the capacity and not buckle. Once you make contact to bedrock with the pile, the slenderness to length ratio of the pile becomes especially important and because so much of the soil is softer clay soil versus rock, the pile may literally buckle under the weight even while in the clay soil. Since we are dealing with tremedous loads, here.
I would be concerned the piles might buckle if overloaded and physics 101 principle of Newton's law is that Franscican bedrock consists of schists, serpentine, basalt, chert, limestone, etc. This is probably going to have about bearing capacity in the realm of 3000 to over 10,000 PSF or more depending on the bedrock geology makeup and competency of the bedrock material so you can more or less call it a hardpan. These type of piles bearing on or in bedrock being called "end-bearing piles".
Basically, the equal and opposite reaction rule means that the hard pan is going to transmit load back up the pile as load is transmitting down it.... and potentially the pile buckles like the principle behind column loading. In effect, you will have very long columns going from building's mat to bedrock. You might think the clay soil will keep the column from buckling. I'm not sure if it will keep the cast in place "columns" (end-bearing piles) from buckling/spawling. Therefore, I see the issue with this tower and the current proposal to be sketchy.
All that is left of 270 Wall Street, the JP Morgan/Chase headquarters. Designed by a lady architect, too, Natalie de Blois, working for SOM.
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