What Really Happened at the Millennium Tower?
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- Опубліковано 15 лис 2021
- The Millennium Tower at 301 Mission Street in San Francisco is famously tilting and sinking into the ground. How does geology affect the design of skyscraper foundations, and what is being done to fix this structure?
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Would love to see how structures like the LHC are planned. Great video!
i don't know about you, but something tells me this retrofit won't work... in retrospect, one can't help but think that the excavation at the Trans Bay Center next door exacerbated the problems, which would have most likely happened anyways; ironically, it flashed on me that possibly a steel inner skeleton construction w/steel exostructure (ala the original WTC 1 & 2) would have been possibly more suitable than concrete, a lesser load...
You're awesome, and you always do GREAT work, and I love your videos.
One thing I disagree with: The engineers should have dug down to the bedrock, and they were a bit nuts for not doing so.
I'm from Chicago. The Sears Tower's foundations go WAY WAY down to the Niagara limestone underneath RIDICULOUS amounts of clay. And that was built in the 70s! No reason they didn't do the same other than "hey let's cut corners!" .
@@janofb aka 'The Leaning Tower of Frisco'!
The Bearing Capacity of the Soft, wet clay or muddy clay is around 50kPa, so you can design a house up to that not the 5kPa you stated at the beginning of your video.
At least they didn't build it in an area prone to earthquakes and liquefaction.
imagine if it was built right near a major fault line, thank goodness that didn't happen
Nothing to see here! Nope!
**seismologists drinking in the background**
@@irenicrose You are both kidding, right? San Francisco 1906, how much closer to a fault line do you need to be?
@@jeffstanley4593 who cares? Climate change will make big parts of the US inhabitable over the next 100 years. The north will be overrun with millions of Texan, Mexican, and Californian climate refugees.
@@jeffstanley4593 That sound was the joke sailing right over your head.
Why didn't they just get the residents to put all their stuff at one side?
wouldn't have achieved anything if at all
Imposed load
@@ydid687 way to not get the joke.
😂
@@mikkopenttila7604 yea i know i was just quashing any doubt left
Because it all kept sliding downhill.
I did some geotechnical drilling in the Bay Area for a couple years and I hated that bay clay. We called it bay mud as it was super dense, very sticky, and stinky. Fun job though as it was very interesting to literally see the different layers of soil beneath you as you pull out sections of soil and rock. Bedrock coring was my favorite because we would drill and pull out a cylindrical tube of solid rock and we could see all the layering of millions of years of rock formations.
That's really neat. I work at McDonalds. Not so neat. 😂
@Brian Woodrow This just in, Brian debunks all of modern geological and physical chemistry knowledge in 1 sentence. A noble prize is sure to follow.
I agree with Brian. Million year old earth is ridiculous. But some day when you meet our creator you will to. Sadly he will say "I never knew you"
@@mattmatt6572 Matt, please be quiet unless you can provide evidence for your claim.
@@maxv9464 I have loads of evidence against the million year old earth what is your evidence for it?
This video was made 7 mos. ago and Hamburger has made more mods to his proposed repair by reducing the number of piles from as I recall, 52 down to 18. This will produce less vibration during installation but pile loading will increase. The fact that they keep tweaking and tweaking the design suggests to me that ultimately this bldg will be torn down or at minimum some number of floors will be removed. All of these measures are stop gap to forestall the inevitable.
Yup, now just the center is sinking and the lean is not correcting itself as planned.
Speaking as a geotechnical engineer, this is the best project I’m glad I never worked on.
Realistically speaking, would you even have a career left if you worked on this project? What are the legal protections you have as an engineer?
@@shippo72 the company you work for has insurance protections for their employees so you are not civilly or criminally liable unless you engage in gross negligence. Based on what I’ve heard about this project, this was not expected. You are usually only held responsible for acting in a manner that other engineers would have acted in a similar situation.
Still, what a huge headache
@@acidset oh no kidding, it would be a huge amount of stress as you’d be forced to defend your decisions over and over to a degree that would feel like a rectal exam. Like I said, great project that I’m glad I was never a part of.
@Yeah Okey Probably won’t be allowed to be involved in future skyscraper projects but because no one died, I doubt this type of failure is career killing. But I’m not personally involved and don’t know the people involved so just pure speculation on my part.
When The excavator was digging the basement for my new house we found bedrock just a few feet deeper than the original depth planned ... I paid extra to dig down to bedrock. The footings are drilled and pinned to that bedrock, and the ten foot ceilings in the basement make it a unique living space.
Lucky!
Conversely, I know of a town that has slanted layers of fracturing rock just barely subsurface through most of the town.
They have actually had to ban explosive excavations because the vibrations were causing existing homes as much as a mile away to shift, usually downhill.
When the house I live in was being built they hit solid rock. It's still there they just flipped the layout 180 degrees to make it work with the rock.
where I used to live the soil was so shallow they would have to blast the bedrock just to lay the foundations for certain houses. I mean at least if you wanted a level foundation and there is no way anyone is getting a basement unless they are stupid rich.
@@MonkeyJedi99 what town?
@@brendonhalverson5178 Oakham, MA.
As an engineer (albeit in a rather different field) I can say that one of the most demoralizing things in my life have been situations where you discover “yet another problem” that threatens to unhinge the entire project. I have no idea whether and where the mistakes may have been made, but I empathize with what the various engineers in this story must have (and are likely still) gone/going through…
It's a sad fact of life.
When the people with *brains* argue with the people with *money* , the former always hit the mat!
Engineers aren't so smart. They just have a peice of fancy paper with their name on it. Ancient Egyptians had a better understanding of engineering then those in this day n age.
@@mattmatt6572 That's kind of a ridiculous statement. And I wouldn't care of it wasn't also missing the point of what I said. I'm not talking about pieces of paper, I'm talking about smart, creative people working on extremely complex problems, and how it "sucks" to uncover unknown and/or hard to foresee issues when all that pressure and money is on the line. I'm not excusing people who make egregious mistakes, but since I have NO idea whatsoever whether or where they were made in this project, I am not commenting on that.
I'm not an engineer, but completely relate to the 'yet another potentially catastrophic problem' that may sink a complex project, lol.
I was working on the new construction as a drywall, metal stud framer. The year was winter of 2008 . The windows weren’t installed on many floors and wind would come in and take out anything that wasn’t tied down. The fog would be so thick inside that you couldn’t see but 20’ and the cold temperatures coupled with wind was a challenge. I have some great memories of this project. I was 44 at the time, now 58 and retired from local 152 Martinez Ca. 36 years of framing in the city. The company was Anning Johnson Co. and the foreman’s name Jim Hayden (Retired) and Ted both long time employees of AJ. Thank you for sharing.
Did tools and stuff roll around like that other commenter is claiming? Like if you put them down would they roll
@@halahmilksheikh no ! In 08 the tower wasn’t leaning much at the time.
There's something uniquely unsettling about such a large building tilting.
settling rather than unsettling :)
Perhaps that unsettling something is the potential to kill hundreds in a collapse?
There's something unsettling about the whole of SanFrancisco. Doesn't seem like a good place to build, geotechnically.
Especially when you drop something in your house and it starts rolling in one direction.
Can't see why, you can always turn it into a tourism point like pisa.
I've probably said this before, but I'll say it again: I'm pleasantly surprised and gratified that such technical videos appear to be so popular. I'm sure that a lot of it has to do with how well they are assembled and presented, but I think it also says a lot about people's interest in technical subjects. People are smarter than they're often given credit for, and subjects can be highly technical as long as they are also clearly explained. Thanks for what you do and how well that you do it.
Positivity +
Well said
His channel is what discovery use to be and I loved that channel.
The amount of quality STEM content on YT is high and the quality is getting higher and higher. This channel, Real Engeneering, Smarter Every Day, SciShow, Mark Robber, etc are so good.
Yes! I am fascinated by specialties outside my sphere! The world is so diverse and there are so many things which are needed to make it function and when people have a niche set of knowledge that drives them I find that so compelling! It's not information I need or probably will ever retain, but knowing that someone not only knows about it but LOVES it gives me so much joy.
The UA-cam channel "Building Integrity" had an interesting update on this a couple days ago where he predicted that the steel plates transferring the hydraulic load into the concrete are way too small.
Now I'm the wrong kind of engineer to have an opinion on this but there might be a chance for an update video if this whole rescue plan fails spectacularly 😄
So my understand was that not only was it the piles not reaching through the old bay mud to the dense bedrock, but that the structural system was also changed. Originally the plan was for the building to be constructed with steel girders and columns and thus the engineers understood that the old bay mud should be enough for the structure as it was designed. The developer however in a bid to save cost on the structure proposed with the contractor to replace the structural system with a reinforced concrete design, not taking into account the design for the sub-structure that was going into the ground. This also contributed on top of the issues outlined in this video about why the building sunk faster, but the added weight of the concrete instead of steel was also not taken into account thus exacerbated the sinking.
very interesting - a change at one level of construction can have impacts on other levels
The Developer ended up spending those “saved” $$, and more, on the litigation and payout. Karma got them in the end, and the story is not over yet.
🤣😂🤣
I kind of find that story hard to believe. Do you have a source ?
That was from a friend who is a structural engineer in San Francisco for DeSimone engineering.
“This structure is incomplete and already tilting”
“No worries, just keep building”
Every problem, big or small, that I've ever reported to an engineer gets the same answer: A pensive look with the statement "It'll probably be alright".
@@C.R.W Hi, It might have been the way you reported it to the engineer that was the problem. Unfortunately, you have to talk to engineers like an engineer. Present the facts first in the same order that you discovered them. Your opinion should come last. Statically, this should give you a better result. I hope that helped.
@@jonathanjohnson8376 It'll probably be alright.
There's a chance that they were under significant pressure to get the tower built on time since delays (such as stopping construction to devise a complicated fix for the settlement issue) often result in significant cost over runs. It could well be that the tower's owners did not appreciate the issue enough to prioritise it over the costs associated with fixing it.
@@C.R.W It might be that the issues aren't likely to cause significant issues and the engineers already knew about it. I know I've put together both analog circuits and RTL code that had some tiny issue that wouldn't cause any real problems and were more of a rare inconvenience. If someone pointed the error out I'd likely say the same thing.
Although I am not a construction engineer and I'm just an electrical engineer that will NEVER work with extremely high voltages regularly. So, any problems really will be alright in my case and don't put people at risk. (I could do high voltage systems if needed but choose not to for the safety of myself and my service dog. AT most one part of a system I'll work with will need a higher voltage that is supplied separate from the main system)
Channels like this are literally all I wanted as a kid while watching shows like modern marvels. Its so fun and the content is informative.
Jeez do I feel old.
Facts. Intelligence really is cool 💯
Dear Eota: Education critic John Taylor Gatto said that the purpose of the American Public School System is not to educate children but to "dumb them down" instead. On the other hand, this YT channel actually expects people to use their critical thinking. THAT is what makes channels like this one special. Unlike Hollywood movie and TV producers, this guy actually assumes that viewers 1) have a brain in their heads, and 2) that they actually want to use their brains while viewing mass media. As such, under the Patriot Act, this channel might soon be deemed a threat to "national security".
@@jayfitmob8645 definitely bro. Virginity is super awesome 💯✋💦
@@thedaily30 😅😅😅 not quite sure how to take your comment, but you are absolutely correct with two children it's the coolest thing I've ever thought about.
A follow up on this would be great. From what I saw in December 2023 significant issues were still ongoing
What did you see? Nothing has happened lately that I am aware of.
I can't believe I'm 2/3 the way through a video about clay consolidation and actually anxious to see the ending. This is thrilling.
I remember the master technician who came to install our new catheterization lab in our hospital. $2.2 million of new equipment. He was complaining that the new concrete ceiling was not quite parallel with the floor, so the suspended gantries for the equipment would tend to drift a bit. He asked me, the chief of the department, how this could be if the ceiling contractor had used laser levels as called for in the specs. I had not the courage to tell him that the guy had moved a stick around to measure the distance between the floor and ceiling.
Expecting poured concrete to be perfectly flat or level is nutso. Anyone with field experience knows that, so I've got to wonder whether the company who makes the gantries is competent. Everything I've ever seen installed (and that's a lot) has allowance for shimming to achieve the desired results because in the real world it's necessary.
@@P_RO_ if you can't make it precise, make it adjustable. Very common in the real world
@@P_RO_ It depends on the project. I worked on a warehouse with shelves rising more than 50 feet. The floor had to be perfectly smooth and level to accommodate forklifts and material stability on the shelves. We had a specialty construction company come in to construct the floor. After construction, it was tested and was no more than 1/100th of an inch out of level.
A decent contractor should be able to get a floor level when needed.
@@pyhead9916 Also, importantly, a good engineer/contractor will admit when they cannot deliver on the project specification, instead of just winging it and saying "Close enough."
@@pyhead9916 I've seen "superflats" get build... seems extremely tedious and more of an art form. Teams of concrete workers with flashlights and grinders, lying their faces on the ground and shining a flashlight to reveal any irregularities. There's probably way more to it then that, I was just an observer
6:41 - a comprehensive settlement... (of the legal kind) 😆
Hey Jeff nice to see you here
Is this the red shirt jeff or the sane one. 🤪
oh man I'm seeing you everywhere this morning
@@CuriousSeeker09 Depends on the type of settlement!
Bothering to time stamp a completely obvious minor joke, so you may then employ the most tired of emoticonic reaction suggests you are destined for low end mediocrity.
Jeez, this channel is addicting. I love knowing how things work and am especially interested in infrastructure stuff you can't always see. It also helps that I'm in San Antonio so I see local stuff I've wondered about.
I’m a Structural Enginner and it is always a challenge when deciding how many would borings to do. Clients never want to pay for them all and we are forced to reduce them. I often think that since people build decks in their backyard or patch their sidewalk they think that they can be a civil or structural engineer. Backyard work is not 6 years of school for a masters degree, a PE and many years of working on projects as a design engineer.
“But the estimated cost for the repair was as much as $500 million, more than the original cost of the entire building. Turns out it’s a lot easier to drill foundation piles before the building’s built than afterwards.”.
Great quote, you win this one
The insurance is lot more expensive.
"Hello, I'd like an insurance quote for driving piles under an occupied skyscraper"
(Underwriters head explodes.)
This comes under the "do it right the first time" school of thought.
If it is that expensive would it be cheaper to demolish the building and just start over?
@@alanhersch4617You also have to buy out all the leases and pay to demolish the building.
Also the weight of the building on the ground was factored in when neighboring skyscrapers were built so removing in could cause them to start leaning too.
So rebuilding isnt an option.
They have to drill new pilings under an occupied skyscraper and do it in way that doesnt affect the settling rate of buildings next door.
If anything goes wrong you could wind up causing several buildings to become unstable.
Grady played Captain Hindsight a bit here.
I happen to be intimately familiar with this story and have to say, Grady did a fantastic job of explaining the high points and presenting accurate material. Extremely well done sir!
I WILL TAKE YOUR WORD FOR IT
accurate as the bribes it took to build a foundation on wet sand, landfill, and marsh. funny how every other building in sf has piles to rock. but lets use concrete which is heavier but cheaper than steel to build and put a foundation in a garbage dump over a wetland.
@@henryhenry271 Well, thats a bit simplistic, and not every other structure goes to bedrock. But agree, so many developments are profit driven and don't necessarily consider the long term performance of the structure they're building...and the impact they could have on adjacent property owners.
@@joshuacore3457 The short term business model drives the economics towards profits. Then the building is sold before the problems show up. Now it’s someone else’s problem.
@@henryhenry271
A deep foundation is necessarily concrete in nature. Steel can't withstand the long-term exposure that concrete can. You often encase steel (rebar) in concrete to take advantage of the strength of steel and the exposure resistance of concrete. The steel also acts to confine the concrete, increasing it's compressive strength more than just plain concrete.
I happened upon this video and am I glad a did. What a serendipitous find it was. Your explanation of what is going on at Millennium Tower is, perhaps, the best comprehensive overview I have ever heard...from the beginning of this ordeal back in 2016. The manner with which you explain the engineering situation even as you allow the listener to remain interested in the topic...is outstanding. I am not an engineer but you kept my interest for the entire video. You remind me of the professors I had as an undergrad who explained things so well, you actually didn't want the class to come to an end each day. Great job!
Grady, I'd love a ~1 year update on this project as the saga continues!
I'd like to know a lot more about how the retrofit connects to the existing slab.
As would I.
By the illustration it looks as if it’s keyed- the existing foundation block having a socket hewn into it. The dust abatement must be loud, as well as the drilling for that socket. Just a guess.
Me too
Why, did you buy a condo?
Not sure about your key way design
In my town here in the UK, every building, including homes, have to be bedrock piled. Our house is on 175' piles. The town is largely built on reclaimed beach and marshland. Watching piles being installed at the new build across the street was interesting, seeing the driver hammer away, adding pile after pile, then suddenly seeing the stack drop and freefall through some underground layer was quite astounding.
As a fellow Brit, I was amazed by this - I had no idea anywhere here had this sort of building restriction. Whereabouts in the UK do you live?
@@paulhaynes8045 I'm in Southport in the North West.
That's amazing. I'd love to see a video of the freefall.
@@kruks I want to look down the free-fall hole. Maybe toss in a rock for accurate measuring lol.
I recall many years ago watching steel piles being driven on a construction site. Occasionally you would see a pile after a few thumps suddenly drop maybe 30 feet, the answer was to weld another section of pile on and continue.
After what happened in Miami, you'd have to be crazy to trust a building with a history of problems like this.
I suspect they will keep talking until the lean causes a failure and it al comes tumbling down. The building needs to be condemned and demolished.
@@Privat2840 I had similar sentiment. Tear it down and build a park. Or maybe a food court for the bus station next door.
I'd not live there while they were doing this project.
Or it could be a real estate bonanza if all becomes cool after a few years.
Or just give it to the homeless
I can’t believe they EVER let a skyscraper get built on anything BUT bedrock, a LOT of bedrock. It’s a miracle ANY of those Mud Towers are still standing at all.
This was a great explanation about something I see in the news often as a Bay Area resident. The media doesn't report the details, so putting the current pile upgrade into context was difficult. Seeing how the pile fix actually works, I can really see how incredibly challenging this fix is and why they're having some problems with it.
They're going to have to demolish the building sooner or later. This would be like if you rolled your car into the ditch, and argued with the tow truck about the damages that will happen if he uses a chain to flip it back upright.
The car is gone. It's time to call insurance, not argue about methods.
@@aluisious you are right - they are pouring good money after bad.
The "Media" is Garbage..."Fake Reporters and NEWS". NEWS was created in the 1950's to enhance advertising. It's Subjective Opinions from Uneducated Advertising Execs. A lot of people this its Legit... ITS NOT.
Great report! Nicely done! As a Structural Engineer for 4 decades, a few notes for your consideration:
1. Residential foundations are designed for a maximum 1500 PSF per the building code. The typical footing pressure is around 1000-1200 PSF, not 100PSF.
2. Friction piles rely on their skin contact with the soil. In most large scale projects, this is tested first with a test pile. It's not clear if they did this here, but should have to verify the pile solution was practical. In design process, engineers will use friction values from a "table" but should always field verify this is realistic by using test piles.
3. Dewatering is a definite cause of distress because loss of water will accelerate settlement, as you pointed out. The engineers should have considered this fact in their design. Fluctuating ground water table is also a cause of concern and in SF area is a contributing cause to settlement of structures. The original design engineers are De Simone based out of Chicago, IL, and it's unclear whether they have this local expertise.
4. The retrofit design was not from De Simone [developer's engineer] but instead from Simpson-Gumpertz, a SF based engineer. They did not predict accurately the potential settlement during construction and have resulted in recent work stoppages.
5. The seismic resistance of this building is highly questionable, in my opinion, because of all the errors made thus far and I would not advise anyone to buy a unit let alone live here.
Thanks!
Dilip Khatri, PhD, SE
1) I think that Grady was referring to the average load over the entire house footprint, not the load on the foundation footings ... although I have to agree that the load on the foundation footing seems like a more relevant number.
I concur.
I can just begin to imagine how this will pan out with even a mild earthquake- but SF would never get that, right???
Fantastic observations sir. Very interesting dilemma.
So does this building have any earthquake levelers? Like they talk about that they have inside the Tokyo Japan skyscrapers
Thanks for the extra insight Dilip, I couldn't help but find the litany of F-ups amusing especially given the scale of the project. Only time and liquefaction will tell.
The 52 piles originally planned have apparently been reduced to 18 piles. These piles will be very slender. How on earth (no pun intended) can these piles be kept from buckling (see Euler) which reduces their load carrying capacity?
If they are over drilling the holes so that "no part of the new piles can come into contact with the Old Bay Clay" and then the space filled with low strength material, what will prevent buckling of the columns under these very high loads of 800,000 pounds per pile?
Have the engineers calculated what load (based on the length of the unsupported column) each pile can handle without beginning to buckle?
The buckling of the long slender piles, or columns, is known as the 'slenderness ratio'.
Tbf, since the piles are driven through soil, they can be designed as fully restrained throughout its length
Very interesting! Always like to find out more about subjects outside my own line of business. I live close to the River Thames and saw apartment buildings being constructed directly on the southern banks, replacing wharves. They are only 10 storeys high, but when they started construction, the drills used for the foundations were as long as the buildings are now tall. On this side of the river we have the infamous London clay and building so close to the river must have been an additional challenge.
I was an ironworker on this building from footings up. The amount of rebar in the foundation is nuts, but VERY early in the project it was well-known to be built to outdated foundation specs compared to the change orders tacked on going vertical. These issues were brought to the attention of the general contractor AND the developer. They could have been corrected early on, but the developer downplayed them to minimize costs and maximize profits.
These issues were known BEFORE the structure reached street level.
I’m not saying anything, I’m just saying… *cough* scumbags *cough*.
Even before the iron stopped flying and the finish work began, the building was leaning. It was a fucking nightmare to work on if I was under someone that liked setting down (and subsequently losing) their tools and dropping them on me. It’s funny until you realize some sleever bars weigh 10lbs and have a tapered tip. This place is going ass over tea kettle during the next major earthquake.
I hope the responsible parties have to sleep on the streets by the time the problems are corrected. They acted with zero regard and responsibility to the people dumb enough to move into this building… and what is the US if it isn’t coddling the stupidest, most entitled, and greediest among us?
Negligence & greed at its worst! I would never live in a high rise, especially in a heavy earthquake zone! I’m not even comfortable staying in a high rise in Vegas! 😬 Ass over tea kettle & many deaths for sure! They should just implode it!
It will not take another Quake the whole high rise area built on that two layer mud pack will come down without any help just a matter of time.
@@sidneyeaston6927 recent news of it shifting massively pretty much ensure a looming condemnation.
@@buttsexandbananapeels Yes movement in the underlying mud has all ready started the process of liquefaction and the more it moves the more the mud will liquefy speeding up the process. if it comes down the shock wave in the ground will bring down the surrounding buildings no ifs or butts about it. The plan to put piles around it will fail it will only add weight to the side that is sinking. The mud that is having to be sucked out of the bottom of the pile holes is coming from somewhere and that means a lot more than the width of the hole is moving down there.
@Justa - Thanks for the info. This is another sad example of "greed trumping humanity".
I don't think that an engineering report stating that the building is already well out of spec, and that its condition continues to deteriorate, is quite the same thing as declaring it "perfectly safe". It's more like declaring it "not unsafe yet".
"Perfectly safe at the time of writing this, can't guarantee tomorrow"
when your windows are exploding from the building falling over. i think its time to call it not safe.
Or more like not safe yet
Ehm, yes, but every building will eventually become unsafe, so by your definition every building is "not unsafe.. yet". Therefore "perfectly safe" is the correct naming.
Sort of agree, but as others noted, no building can be declared “100% safe, forever”…that is not realistic for any building’s . The best any inspection can say is “we predict that with maintenance and repairs, it will be safe for the next xx years, and get it re-inspected at x-1 years.”
Thank you for that VERY interesting report !!! It is always fascinating to watch the videos you make on Civil Engineering - absolutely love them !!
Everything above the bedrock just sounds like really thick porridge to me. I can understand the reasoning behind their initial design with the friction piles, but failing to account for the water getting squeezed out by the enormous pressure of the building is a pretty big failure.
This reminds me of the new hospital in Muskegon. MI. They never accounted for all the sand it is built on top of. The new ER has I believe, 62 rooms. Half could not be used at first because the doors were stuck to the floor. I had a CT scan there a few years after it was built, and they had that door held open with weighted bags. A nurse told us that upstairs, they can't leave patient carts in the hallway as they roll away.
😱 . I was born but not raised there. Thanks for that information. Yikes!
@@MaloPiloto geez how young are you lol
Muskegon has LOTS of problems. I marvel that people still knowingly choose to live there.
That's wild! Where did granny go? I thought she was sitting in the hallway.
😂
Growing up we were always taught that all skyscrapers had foundations that reached down to bedrock. Thanks to this illuminating video presentation, I now see that that isn’t always true!
Thank you for this great educational program.
In Houston there really is no bedrock to speak of. Friction between deep piles and the surrounding clay and sand is what holds up the entire skyline.
I suppose this is really only possible in places where there is reasonable access to bedrock. In this sense Manhattan has kind of spoiled everyone.
@@Laotzu.Goldbug They drove resistance piles down 80 ft. The bedrocks is at 220 ft. It's now estimated that going to bedrock would have only cost an additional 4 million dollars. In retrospect, that sounds like a bargain! I worked on this building and it's massive, poured in place concrete. To this day I can't understand why they didn't realize they had to go to bedrock!
The burj Khalifa (however it's spelt) also does not go down to bedrock. It uses friction piles like this building.
First thing that came to mind was exactly what you said about the vibration is making it settle. Why not put pop out anchors similar to Wall anchors down that will open as it settles.
"The developer's engineers and the City have shown that the building is perfectly safe through detailed modelling and investigation."
Literally the ENTIRE story of this building, including the novel fix you mentioned before this point, can be summed up as "This thing isn't behaving like we expected it to." I get that media can be sensationalist and click-baity, but given what's happened with this building would YOU trust it? I wouldn't. Confidence can come when the engineers don't have to go back to the drawing board every month.
Indeed. Grady is usually fair and balanced but he dropped the ball on this one. Josh Porter from Building Integrity has a four-part series that goes in-depth on this issue.
I remember mounting TVs and other Audio Video equipment in that building years ago before they announced the lean. It was hilarious having to call my colleagues into the rooms to assist me in leveling the equipment. All of our bubble levels were so off that we had to measure from the floor & ceiling to get things plumb. 😂
Your largest display would only be off “plumb” by 3/32”. Unless you had digital levels you can’t typically achieve better than 1/16” accuracy
@@rcpmac 1/16” over what length, floor to ceiling?
@@raybod1775 Good question. I read that after the new pile driving started, the tilt increased to 22 inches. Google says Millennium is 645 feet tall. The tilt may not have been measured at the very top. So, I will randomly selec that the 22" tilt was measured at 600'. The tilt ratio is 22/(12*600) = 0.003056. Over a height of 10 feet (120 inches), the offset would be 0.367 inches (nearly 3/8", which is appreciable) Correspondingly, a 3/32" (0.0937") offset would occur in a tad over 2.5 feet.
@@gregparrott I piqued at the comment of it being imperceptible and recall living in a similarly imperceptibly titled building. the thing is, gravity doesn't lie and all of the cat toys always ended up in the same corner of the living room.
@@jaewok5G Must have had some catnip in the corner.
"Soils don't care about property lines." Succinctly put and true of Nature in general. And I think this channel Rocks!
In Germany there is a 16th century fortress that has broke apart due to nearby surface mining if brown coal. They also stabilized it and half the buildings inside (a school) stand on giant dampeners
I honestly don’t know why people would ever move into a place like that. What a nightmare.
I can't imagine living there while they are "experimenting" with different ideas, and it suddenly starts getting worse (which did happen). 😮
In a city known for earthquakes and unstable soil, it is unthinkable that ANY high rise was ever approved where there was a bedrock footing option. I heard it would only have cost $4 million more to do this. No doubt there are single units in this building that cost that much.
You obvioulsy no nothing about how earthquakes are affect buildings.
@@shrimpflea I don't either. Are earthquakes not more likely to collapse a leaning building anchored to unstable soil than a building anchored to bedrock (and thus not leaning)?
@@shrimpflea you're obviously not living on an earthquake fault.
@@shrimpflea But maybe he does KNOW
Space is needed for all the necessary labor in SF; disaster will be the only thing that ends this crazy skyward expansion.
I have designed a few 42-floor buildings with friction bored pile foundations that went down to 45m. It shocks me to learn that simple reinforced concrete-driven piles were used for the Millennium Tower and it was only driven to 24m !! The correct choice of foundation should have been large diameter cast in situ concrete bored piles installed to a depth slightly beyond the Old Bay Clay layer. Large diameter bored piles also overcome the slenderness problem of conventional driven piles which have limited load-bearing capacity.
Are you a structural engineer?
@@dm6187 Yes.
Okay, Mr. Smartypants. Maybe you should write somebody.
Maybe these guys are firm believers in the "Americans can do everything better" idea, so they had a look at the (in)famous leaning tower in Pisa Italy and thought "we can do better than those silly Italians" LOL.
Thanks for sharing. I'm an automotive manufacturing engineer, trained in EE. It's always nice to learn about a new topic in engineering. Endlessly fascinating for those that can grasp the information.
When you build up on the sand...this is why you drill to bedrock! Always always always! And instead of hammering the piles down to bedrock they should drill down to bedrock that would reduce the vibration to the surrounding buildings because you have an auger like mechanism bringing the soils you are displacing up to the surface versus just pounding them down
Great video. Much info.
I would like to know why this tower had this issue while larger towers nearby didn't suffer the same fate. You discussed that the dewatering for other projects affected this one. His did those same Fircrest affect the others or what did they design differently?
That sorta highlights how baseless a lot of the lawsuits were. Of course no one saw this coming!
The building was always intended to settle, it just settled much faster than anticipated in some areas so the settling was uneven. Mostly due to the other projects happening nearby.
The building was heavier than other buildings.
This building is concrete while most tall buildings are steel skeleton structures
@Mark Harvey
What word got changed into Fircrest by your autocorrect? 😅
Also, thanks for teaching me about a tiny town I'll never visit, lol 😆
As for your question, my best guess would either be weight (as mentioned by others) or that the water table in that area does something funky.
By that I mean that it's possible that the surrounding places had to pump out a lot more water, and that as a result the water from under this tower flowed away more than anticipated, while as much as anticipated was pumped out for the others. Which leads to this one skewing but the others staying within expectations/tolerances.
Another possibility could be that the other places just had a wider safety margin in the design (although I doubt it, since most would build as cheaply as possible while staying compliant with the building code).
Lastly, the others could've stopped construction at an earlier stage, when there was less tower and thus less weight compressing the soil (I mean, if your neighbor's house is sinking, you'll probably pause your own plans to see what happens, right?). And it's quite possible that, if all projects were only done one by one, none suffered from the others. So, in essence, timing might matter too.
If anyone is curious, the SF region in general has much if not most of its buildings sitting on this clay. Every year, buildings flex a bit when the ground dries and rehydrates. The Gently Rolling Hills of the Bay Area are thousands-feet-high clay on rock.
And we have multiple fault lines running through, just to make things interesting.
I get nervous about a big quake anytime it's been raining for a few weeks: hill leveling.
It honestly astounds me someone decided building in SF was a good idea at all. It feels like it's only a matter of time before an earthquake levels the entire city and everyone is forced to abandon it as a monument to human hubris.
Bedrock is close to the surface in some areas so things there are well-anchored.
Most tall buildings that use friction piles here are steel and thus dramatically lighter than MT. Some are old enough to have survived the 89 earthquake.
MT is reinforced concrete all the way up so it is much heavier. It should never have been allowed to use friction piles - bedrock piles should have been required. But the original building plan to which the foundation was designed was changed without re-engineering the foundation plan. The city (like most cities) relies to a large degree on engineer stamps and peer review which claimed it was all A-OK.
FWIW the city now requires piles driven to bedrock for all buildings above a certain height to avoid any future problems, no matter how the building is constructed or what fancy tricks they want to play with the foundation design.
Also FWIW they should have required mini-piles driven through the foundation mat interior to the building. There is no way a mere 18 piles will be enough to stabilize the building long-term, not to mention correction of the tilt has already ceased unlike their predictions... if it had been 100 smaller piles on the interior a jacking system along with sensors could have been used to slowly reverse the tilt over a few years. Then replace the jacks with permanent connections when finished. Also wouldn't have to worry about cupping or cracking of the foundation mat since the building wouldn't be supported primarily along the edge on that side which induces a lot more stress.
Well presented! I was drawn here from the articles and came to seek out more information!
Thank you soo much ! I love learning from your presentations !!
10:50 "The story of the Millennium Tower is a fascinating case study in geo-technical engineering".
None of the news stories I read had that as a headline. Maybe they should have.
That apt headline would be far too accurate and nowhere near salacious and misleading enough for any "news" organization to run with.
The media is too dumb for that
@@awesomusmaximus3766 More accurate to say that dumb people click clickbait. The media uses annoying clickbait headlines because sadly clickbait works.
@@DemPilafian You can't say that even though your not wrong
News is first of all a business. If they can't sell a story, they go out of business. So people who follow a civil engineer UA-cam channel click on different things than the average news consumer clicks. The focus of the story is towards what gets the most following, which is weighted toward the average news consumer.
Apparently another because of the problem is that initially the building was supposed to be a lighter all steel structure but after the foundation was completed, they decided to make it a concrete structure or a mix of concrete and steel, the new construction method being much heavier than initially planned. Rather than verifying this foundation could handle the extra weight, they just did it and got burned.
The only good solution is to hope this building never falls... or just deconstruct completely or half it's height
i was working on a bridge above a soft soil, which are 60 meters thick, and me and my team wouldn't even hesitate to used 60m bored pile down to the bed rock, as when engineers faced with this kind of problem, we don't messing around, we go to the basic, it might be expensive design, but it would be the one that make us the engineers sleep well at night.
Fantastic video!!! Great job
I think we've all had a bad case of friction piles.
Sigh...I can't disagree with you. Thumbs up.
sounds painful
Friends don't friends design friction piles.
(I just designed a 1400ft tall tower's guy anchor with (16) 50-ft deep piles.
Funnily enough there's a "Millennium Tower" in Glasgow in Scotland that also had major problems. (tallest structure capable of rotating 360 degrees)
And the "Millennium Bridge" in London was swaying wildly on its opening day, due to a design oversight, combined with the large amount of visitors: ua-cam.com/video/gQK21572oSU/v-deo.html
Which tells us to not name anything Millennium $FOO (including Millennium Falcon :D).
the Millennium bridge in London also had unforeseen design issues that required a retrofit.
I suggest to all engineers to never use the word Millennium in any project for the rest of time, since it's horribly cursed
I was expecting you to say the major problem with the tower is it’s full of Glaswegians.
This was fantastic, keep it up!
Excellent explanation! Thank you!
"Safe" it may be, but settling that far has misaligned the utilities with the ground, and horizontal plumbing lines inside the building no longer have enough slope to drain properly.
Even several years ago they were having issues internally with things like doors, windows, and kitchen cabinets not closing properly because they settling pulled the structure out of square.
Also the Home Owners Association will at some point be having to charge residents special fees to clean up some second or third order consequence of this in the future, potentially decades from now. So why buy into that uncertainty and while amusing to have ping pong balls naturally rolling to a corner of the house it is not what you want to sink a large portion of your net worth into.
That aspect reminded me of the story of the Florida condo collapse with the concrete cracking, etc.
I think we need an update. I read recently that the "mat" in the lowest basement is also unevenly sinking, suggesting even more issues. Thanks for the great videos. To compensate you, I have added my like, above.
I am sure he won't spend it all in one place
Yeah- Josh Porter mentioned that dishing in his latest YT video almost 2 weeks ago...
Nothing works I live in bay area..I read stories about it when I need a good laugh.. Or a good head shake..
excellent summary, thanks!
Great presentation
"Turns out, it's easier to build the foundations before you build the building." I think these are words to live by
"Cost of erecting is cheaper than the cost of correcting"
I am just a truck driver from Oregon but everything about this video was super fascinating. I have taken days off in San Francisco a few times, and I have walked by this building wondering what they planned on doing with it, and this video gave me all the answers I was looking for. FYI I STILL WOULD NEVER TRUST THAT BUILDING!!!
really intereesting!!! thank you!
Excellent presentation thank you!
Thanks for this! One fun detail for the folks at home is that the tilting is starting to affect the drainage of the sewer. Having dealt with an expensive sewer replacement caused by poor drainage, at some point the residents are going to get a large bill.
I can't help but think that this all could have been avoided if they had just drilled down to the bedrock !
@@dankelly5150 Nah, too pricey !
As a sf resident I have been witnessing this mess first hand. There was a firm who tried telling the city/developers the building would sink way more than expect. They were ignored. It’s relevant because now the same firm is desperately trying to get city halls attention because they think the fix will only temporarily be effective then make things worse.
That may be perfectly right, but I also am worried that it can be a case of "The Economist who predicted the recession!" syndrome. By that I mean there's ALWAYS somebody predicting doom (or success, in the opposite case), and if there's enough people involved, one of the "randos" is going to be right, some of the time, but it wasn't because they KNEW, it's because they were the lucky one. So they could be right, the one voice that really did know ahead of time but were ignored. Or they could just be right because ALL opinions existed beforehand, and time marches on.
I left the city after 38 years precisely because of the endless corruption and the endless building downtown.
That was my thought - this will make the problem worse. Heavy construction near a foundation is a terrible idea. And then once half the building is anchored to bedrock and the rest keeps sinking? Foundation cracks that will truly make the building unsafe plus tilting the other way. But this is SF and I wouldn't expect anything else.
well the fix did make it sink more. who would have thought vibrating the dirt would make dirt compact. lol nobody wants to pay why this building is not condemned.
Very well explained.
Great content !
I really enjoy your explanations sir, very entertaining indeed! 👍🏻👍🏻
"Let me know what you think"
What I think is that with my studies in engineering school (majoring in soil mechanics and structures, but got engineering jobs after graduation in 1974 in different areas of engineering), I recall designs solving the problem of erection of commercial buildings over compressible clay layers by driving piles (creosoted wood, steel cross sections, or reinforced concrete depending on the building, the clay layer etc.) down to bedrock or a at least a less-compressible stratum.
I can't say for certain, but it seems to me to expect a clay layer to support a skyscraper is really sketchy in both of the aspects of consolidation of the clay and the expected friction of the clay against the piles.
The design engineers were probably told to come up with the cheapest design they could think of. lol
The owners also may have told the general contractor to skip some of the soil exploration and testing and use test data from adjacent buildings in order to save money. Projects have failed due to that error. At least back in 1974 and earlier.
100%. I'm a mech. engineer and business owner. I believe investors don't care if collapses, as many or most of them may do in a catastrophic earthquake. As long as they can put their name on a fancy building, rent it out and insure it...who cares? They're not going to be the ones in them when they are converted to rubble. Building a 300' structure on clay and sand in the most earthquake prone city in America just sounds ludicrous. I would personally think anything over 10 stories is pressing their luck.
All of that actually happened.
@@nextari You can build a tall building that will survive earthquakes. The Transamerica building was the tallest in the West for a long time and survived the Loma Prieta earthquake, but it was also wasn't designed as a pernicious cash grab like the Millennium tower.
The toxicity of the ego and hedonism contributed much, with a lot of nepotism and corruption.
It is for the reasons you mentioned a major accident should happen. Only then these short sighted building owners will take the engineers seriously at least in the future. By the way the engineers also have to be blamed. They agreed to listen to the owners because if they don't the contract would go to another engineering company.
I live in the tower, and your analysis completely neglected the most important concern. My pool table is regularly out of level. It’s a damn nightmare
1st world issues
Not to mention, you can't fill a cocktail glass without spilling!
Be glad you dont have a pool.
How much are condos selling for?
But what a home-table advantage you enjoy vs non-residents. Doubtful ol' pals Tony and Mo can make the gravity adjusted, arc shot required to sink the 8 in the corner.
Clear and interesting! Thank you. 👏
Sweet video Grady.
Beat me to it! Wish I wasn't so busy. Good job Grady.
We're still waiting for your version. It's not a contest really.
Could we assume that the sinking was accelerated during drilling because the drilling allowed an additional outlet for any excess moisture..? Almost as if the drilling crew just installed several vertical drains? I am genuinely curious
Probably that, coupled with vibration induced fluidisation
They should have started drilling on the high side to accelerate that settling!
@@MikrySoft liquefaction doesn’t occur in that support layer
I thought the same thing. I think the issue would be predicting how much settlement would occur on the other side. They may end up causing the other side to sink more if they overdid it. However, I would hope they considered it.
@@YoungCoty Yeah, one might think it would be best case scenario, technically, to have access to all sides of the building simultaneously and drive piles selectively balancing out the whole operation in the process.
In practice, I'm not sure they would be able to block off basically all four sides and the roads and everything else associated with that.
Thank you for sharing this wonderful analysis
Love this channel and content
Always scared every time I drive by it, especially when I'm on the Bay Bridge. I'm always thinking "Not today please"
Excellent vid! I was wondering what happened with this structure a few weeks ago, glad you cleared it up.
"a comprehensive settlement, the legal kind." lol. Nice.
Great video!
Are there more videos about the millennial tower with more detail about how they actually build the structure to support how they did all the retro?
Love this video also thanks very much.
How about the tenants who live there? One of the tenants but a marble on the floor and it easily rolled across the floor.
“How do engineers predict how soil will behave under extreme loading conditions?”
Often poorly, it seems
*Occasionally* poorly, it seems
I worked on the interiors on this building. However, I've done a lot of concrete construction. When I first came in on the 4th floor, I looked around at the shell and asked: "How high are they going with this thing???" (A: 58 stories, on bay fill!).
It's massive! Saying it's built like the proverbial brick ****house would be an understatement! The concrete is so dense, that when we were drilling into it, we were breaking equipment I've never seen break before!
I understand that when the general contractor came on the project, they convinced the developers to go with a "different design", though apparently, the foundation plan was never reassessed. That may seem unbelievable, however, testimony in court has revealed that a soils engineer was NEVER retained.
The contractor specializes in poured in place concrete. I've always wondered if the original design for was a steel building, for which friction piles may have been suitable.
Surprisingly, in all of the litigation, the only company I DON'T see mentioned, is the general contractor!🤔
I'm beginning to think they're going to have to tear this thing down, which would be a massive undertaking in itself!
Yea its looking more an more like they may not have a choice. Thanks for the insight. 👍
It can be done in one day, just ask
NY since engineers there still state building 7 fainted into its own footprint but it’s been said it was brought down because it was deemed unsafe. Took them minutes to wire it up and bring it down. Never Forget 9/11
@@costafortiaThis is an engineering thread. Come back to reality... Leave Q'ville immediately!
Ha! Just take half of it down, call it the sawed off tower. Imbeciles could have drilled to rock easily in the first place.
@@carlwilliams6977 people like you are the problem
Great video and explanation. Thank you
Excellent explanation. Thanks.
In another decade, we will be hearing: The new plan is to put flying buttresses on the tower providing it with a tasteful Notre Dame look while reducing tilting.
As someone who works in a field very distant engineering or architecture, this articulation was so helpful! Really made it easy to track and understand. Thank you 🙏🏾
Well done. I do not find this video boring at all...but would love more pictures. Thanks!
Another great video Grady. Let's hope this building remains safe and standing. Maybe sometimes it's just not worth building towers of such size and weight in certain areas.
The same issue occurred with the old cantilever section of the Bay Bridge. Cheaper to not go all the way to bedrock, so thousands of fir pilings driven into the mud supported the concrete pillars. The 1989 earthquake exposed what a problem this was. It is funny that the developer doesn't have the money to do it right the first time, but they have the money to try and repair it later.
@GoCoyote - Its like the saying "If you cant find enough time to do it right the first time, you,ll find the time the second time. Reminds me of a character named Ray White I worked for in my teens in the late 70s. One of those sketchy guys who would pay cash under the table, build with materials not up to code to reduce price. This guy had a building inspector coming by and he tells us he will give us a big bonus ( In his mind) if we hurry and get the whole business sheetrocked in a few days. With a crew of 4, when realistically we needed 6, we did 12 hour days and still couldnt make the deadline Ray White starts getting nervous because the inspector is coming. It was fun watching this shyster getting a dressing down by the inspector for using 3/8 in. sheetrock instead of 1/2 in. Oops Ray! You blew it! WHOLE BUILDING had to have ALL sheetrock replaced!
@@daleleisenring4275
COL (chuckled out loud)
Yea, sort of a constant in the trades. Have heard that saying using money for time a few times also. Had to dig up and move the primary switch gear feed conduits because the superintendent’s ego was to big to have someone else double checking placement after we had already set them up correctly the first time and he had us relocate them. Cost more than 250k to cut out the concrete and dig down 6 feet underneath the building to move two 6” conduits 2 feet over. I remember being surprised as an apprentice that the best journeymen would ask us to double check their work. Later I figured out that they were both teaching us and having us double check their work.
1:58 The ease with which they are driving that beam into the ground is not reassuring.
@@daleleisenring4275 haha good on ya Ray!
As a geologist and soil tech in a materials lab, who worked with civil engineers on dams and other constructs, we always thought clay was the most difficult to work with because it shrinks and swells and/or dewaters.
True, it is the most difficult. I worked with yazoo clay in Mississippi. It can expand 200 times its original size. The best way to build on it is to dig out a 6 foot hole below and around the foundation level, replace it with compacted sand and direct all water away from the site. The Australian's utilize the best clay design technology!
Interesting. We are always told how lucky we are that London is built on clay. For instance, the London Underground was much easier and cheaper to build than the New York equivalent - no blasting through rock, just nice, easy clay. In fact the problems come when they hit patches of sand, as they are unstable and usually very waterlogged. I don't know how this affects tall building, but they've certainly built enough of them in the last 30 or 40 years!
@@pyhead9916 I have worked as a plasterer in Melbourne Australia. Lot's of cracking in the walls from house's built on stumps in clay soil. They are building on slabs mostly these days
@@paulhaynes8045 New York is probably one of the easiest places to build skyscrapers due to the close bedrock.
That's how Texas ends up with a lot of cracked home foundations.
Great informative content, two thumbs up.
in Santos Beach city in Brazil we had exactly the same problem, but for smaller and older buildings. A plenty of them have tilted over the years
I object to the "perfectly safe" bit. It's perfectly safe *now*, but the exact same reports warn about the risk of it becoming unsafe as the settlement continues. People don't buy expensive condos to leave after a year, they typically want to keep them for a long time. They definitely don't want to lose access to their home because it becomes unsafe. It's not the safety *now* that matters, it's the safety outlook for the next 30 years.
yeah! it's perfectly safe... to go get your belongings and find a new place
You should have watched 10 more seconds before commenting...
No one with $3 million to invest in a condo is going to invest it in an "unstable building."
Anyone near this during the next big earthquake is going to be objecting, too.
I think it’s pretty fair to not trust the same people who screwed up the initial design & possibly covered up the settling. “It’s totally safe” then it starts to tilt even more with the new drilling!
It's a real pleasure to get an informed and indepth look into a troublesome project like this, beyond the clickbait headlines