🚧 Keep up with all my projects here: practical.engineering/email-list 👷 My engineering failures playlist: th-cam.com/play/PLTZM4MrZKfW_kLNg2HZxzCBEF-2AuR_vP.html
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!" .
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.
@@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.
@@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.
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.
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.
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.
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.
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.
@@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.
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.
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.
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".
@@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.
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.
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)
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…
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 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!
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 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_ 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
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.
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.
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.
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.
“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
@@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.
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.
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.
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.
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.
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.
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.
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.
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.
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?
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.
@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.
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".
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.”
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.
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.
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.
@@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!
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.
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.
@@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)?
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!
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.
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.
@@awesomusmaximus3766 More accurate to say that dumb people click clickbait. The media uses annoying clickbait headlines because sadly clickbait works.
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 TH-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.
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.
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: th-cam.com/video/gQK21572oSU/w-d-xo.html
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. 😂
@@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.
This video is out of date. They did go ahead with the external pile idea but they only installed 18 instead of 52. The change was required when the sinking of the building accelerated as they drilled holes for the piles. The planned fix is complete. Things haven't gone according to plan. They weren't able to raise side that had sunk has much has they had hoped, the plan was for the side that hadn't sunk to gradually sink to the level of the side supported by the new piles. Unfortunately that side isn't sinking so it looks like the building will remain out of plumb for the foreseeable future. However the 3 meter thick concrete mat is now sinking in the center. this is caused by the stress of the building being suspended on two of its sides. It would help if some of the original piles began to take up more of their share of the load. So far it seems they don't intend to cooperate.
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.
"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.
@@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.
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.
The TH-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 😄
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!!!
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 🙏🏾
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.
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.
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.
Every video you ever make is so absolutely interesting and insightful! As an engineer myself I still constantly find myself learning bits and pieces from your videos. Keep up the great work!
Yeah... I remember the fist time I heard about the Millennium Tower in our local news... they were showing residents setting down a ball on their floor and watching it roll (with some speed) towards the corner of their condo. At first I wasn't sure what I was seeing, little did I know it would turn out to be a huge problem like it did. The building also had broken windows high up, they said "wasn't caused by the settling" but if not, then that's odd, and you mentioned the trans-bay terminal, I think it had problems from settlement too, they had to close the road under the crossing, rerouting the buses and vehicle traffic, making a real headache... I think the steel support beams were cracking so for that they put jacks while they retrofitted the supports... that whole area is just a hot-mess of construction issues plaguing both of these projects. I'm glad I don't live in S.F. but the whole SF Bay Area is an earthquake disaster area waiting to happen.
I love your content you have educated me so much on general engineering thank you so much keep doing what you're doing your efforts are bountifully appreciated
I'm curious as to how the structure's settling impacts its connections to the power, water, and sewer lines. How often do these connections have to be disconnected, moved, then reconnected? Or is my understanding flawed? (Notes: I'm consistently amazed at the high level of production for Practical Engineering. I'm not an engineer, but even I can understand the issues with the straightforward presentation and absence of technical jargon. There's no way I'd live in this tower, having to trust the assurances of perfect safety juxtaposed with the previous false assurances of reliability seems obtuse.)
There are several civil engineers who have said that sewer lines are in serious jeopardy of failing due to the building no longer sitting level so the gravity fed sewer lines could drain properly...the building is doomed
@@billiamc1969 This is a small problem. At worst a sump will be constructed for the sewage and lift pumps will be installed to take the wastewater into the sewage system. The building may have been built with this design from the beginning.
You probably would not be able to afford to live in this tower. One of former condo owners is former quarterback of the San Francisco 49ers, Joe Montana.
You won’t see me living above the fifth floor or in a basement. Lessons learned from living in NYC! Five floors is all my asthma and arthritis can handle. I’m allergic to mold and have a fear of drowning.
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
Grady, you speak very well and explain things so the average person can understand. I sure hope the building will one day be 100% and all the residents can live happily ever after. Mike
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.
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
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.
"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.
I remember seeing a news story on this and the video that showed items rolling towards the windows. It was a pretty noticeable tilt for things like a table as well.
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 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.
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!
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
Reminding me of the Florida condo collapse, even if it is unrelated technically. Who wants to live in a condo where the slight chance of high future repair costs and inconvenience far outweigh the thought of having a cozy little place to live. Great presentation. Thank you.
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.
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
Scary! Funny, we (Toronto) have the total opposite problem. Our entire substrata is solid rock, that is rising, or rebounding, up to 1-3 cm per year, why? During the last Ice Age, where Toronto currently sits, was 2km of ice, it’s immense weight pushing the ground down. Since the last glacier retreated, the ground has continued to rebound to this very day. It’s great for stable foundations, hence the explosion of skyscraper construction over the last 15 years (we now have the most skyscrapers in North America, second only to NYC)….but despite all those heavy towers, the solid rock beneath our feet continues to rise, creating numerous issues that we’ve now learned to overcome. After the initial foundations are dug, and it’s walls securely in place, they install countless rods into those walls, and wait approximately 3 months. If the rods begin falling out, they must wait until the foundation has sufficiently equalized before pouring the base slab. To do so too soon, could result in the same problem the tower in this video has, but for totally different reasons. However, with hundreds of skyscrapers recently built, under construction, or awaiting approval, it seems they’ve conquered this problem…if only they’d use quality materials. Dozens of condo towers, most by the waterfront, owned by a Chinese consortium, were built with the cheapest materials possible, resulting in brand new buildings falling apart. They’ve had to replace all the windows and glass panels after a series of disasters, with huge glass slabs falling off from 40+ stories up, crashing to the ground, I’ll never understand how they received final approval before allowing tenants to move in, when these building were falling apart! Someone is getting rich from bribe money! My co-worker was unlucky enough to have bought one of these units, a 650 sq ft 1BR unit on the 45th floor. The day she moved in, none of the doors would close fully, her balcony door was frozen in place, due to installing all doors and windows, before the concrete had cured sufficiently, causing all doors and windows to be immobile. She had no water in her kitchen, the drains weren’t even connected, forcing her to use her bathroom sink for everything. Then, as winter approached, all her windows and balcony glass panels fell out, nearly killing several people on the street below! She paid $1.1 million for it, yet it was like living in a slum! All the residents hired a lawyer and sued the developer, but surprise surprise, they were in China, refused to do anything about it, and hid from our officials, after making billions off this disaster. So, all owners were on the hook to pay for all repairs! Luckily, city council knew they screwed up, as that building, along with over a dozen others, all built by the same crooked, criminal consortium from China, should NEVER have been given final inspection approval. Knowing the people would sue the city as they were unable to sue the developer, the city quietly paid for all repairs, costing we, the fax payers, well over $300 000 000!!! (The feds paid most of it). The moral of the story? BUYER BEWARE!!! ESPECIALLY IN TORONTO AND VANCOUVER ( Same Chinese developers did the same in Vancouver over 20 years ago). This is why I prefer to rent, owning is now a game of Russian roulette…if I do finally buy when I retire in a few years, it will be in a well established, older building, that was built properly.
Curious to know if any of the property values dropped in the surrounding areas that would be directly affected if this thing ever collapses. Or is all of SF still greatly overpriced no matter how risky it may be to be there?
@Jason Rackawack You can count on it. Properties are based on the "comps" of the area. When there's a shift in value of a given property, up or down, the surrounding properties shift in the same direction. SF has lost a lot of real estate value in the past two years including the rents which have dropped by more than half in a lot of districts. The city has become a sewer. Very sad, but, considering the so-called leadership, no surprise.
Or is all of SF still greatly overpriced no matter how risky it may be to be there? - YES, yes, and YES. My wife and I have been in the city 10+ years and have rent control but live an older building (as nearly all are). The buildings rent is $3200 month for a one bedroom apt. This should tell you everything you need to know. My guess is the person that replied before me, does not live here and watches too much propaganda.
@@WildWestGal I grew up in San Francisco in the 60s and have been very sad to see the way the politicians have ruined the city with their misguided policies. Some day, people of San Francisco might just wake and and start electing people that actually represent the cities best interests and not the special interests and large developers.
@@WildWestGal clearly doesn't live in San Francisco and knows nothing of it. If rents had dropped by more than half, 6 million people would be having a party on a scale that could seen from space. Our real estate values are rediculous by any other standard (and have nothing to do with "leadership" good or bad) ...but "overpriced" is subjective and the local market, silly as it may be, is remarkably consistent and, good or bad, supported by the biggest industries and companies in the modern world. It stops growing at times in spots but doesn't really drop in any serious way. It dipped a bit during the pandemic - maybe shedding the previous 2 years' rediculous growth...at most. Not half. Not near half. Most sellers just wait out these dips. Most people's complaints about the city amount to that its become too shiny too quickly, not that its become a "sewer". We do have a serious homeless problem, exacerbated by greedy absentee speculators buying in and throwing longtime local residents out on the street to double the rents. If anybody has a great easy solution to that (that doesn't involve concentration camps or heavy-handed no-outside-ownership laws like you see in some decolonized countries) we're all ears. We're spending a tremendous amount of money building affordable housing on a tiny peninsula that was full a century ago. We've nowhere to expand but up. We're building the tallest residential towers in this half of the country. What else are we sposed to do?
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?
Great video as always. Being from Boston I've always heard about how the city is built on filled land. I'd love to hear you do a video on how this was historically done and the effect that has on building up to the present
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.
Interesting video, brings another question to mind. The hydraulic pressure of the building which when fully furnished will out mass it's neighboring structures, will this have an effect on their foundations as well as the downward pressure tends to push against four opposite sides. Would this not create lift to the others or are the neighboring foundations already densely compact
I have so many more questions than the answers provided here. For instance, what keeps the new piles, that are both longer and also hitting the bedrock, from bending in the softer old bay clay layer? Will all of the layers react as one in an earthquake or can they shift against each other, generating shear forces against the piers? The fix will rely on hydraulic jacks to transfer the weight to the new piers and it seems the jacks will simply be left holding the weight. What if one fails? What if that failure, and the resulting increase in weight on the others, causes them to fail in cascade?
I get it that the new piles are expensive, but why wouldn't the solution be extended to the entire perimeter of the building? Are they using a drilling sequence like an automotive head bolt torquing sequence, or just perforating the layers along the edges that are currently compacting the fastest?
I also wonder about what adding additional force to the other side is going to do as they "press" the building upright? Seems like that would surely have some potentially unforeseen consequences for the settling behavior of the opposite side of the building. Seems like an insanely complex and difficult situation.
Hydraulic driven screw jacks using multiple planetary gears for reduction. You just scale it bigger to match the weight needed to be lifted. Mass matters. It will require several working together.
Soon enough, these tall buildings in San Francisco will be earthquake tested. Then, we will have our answers, and the engineers will have their grades. Do far, they've earned a "D".
I have a question Ive never seen addressed, when the building sunk this much, isnt the entry into the lobby much lower than the sidewalk? Did they have to change anything or add a step down into the lobby when you enter from the street?
Henceforth the lobby will be referred to as "the basement" and all additional floors will be renumbered accordingly, thanks in advance for your cooperation- the management.
The sidewalks adjacent to the building are attached via reinforcing steel into the concrete of the building itself, so as the building sinks, the sidewalks closest to the building sink along with it. This causes the sidewalk to buckle and crack, which is one of the first signs engineers noticed that the building was settling at a much faster rate than had been anticipated.
I didn't see anything that addressed what happens when/if they get the perimeter piles installed, and the building does eventually level itself. The sides that don't have perimeter piles will just keep sinking after the building goes level. I'm assuming they will have to install pilings on the other 2 sides, I just found it odd that it wasn't mentioned.
Well done with excellent graphics. But you fail to mention that the original plans were for a steel beam structure. This was then changed to concrete form, without adjusting the proposed foundation. Ostensibly (HA) to save money!
As a political science major with absolutely no experience in the construction industry, I really appreciate and enjoy the way that you are able to summarize and present complex engineering issues in a way that even I can understand them. Thanks for your effotst
I guess it boils down to two options, either push up (support) the side that's sinking, or drop the side that isn't. The leaning tower of Pisa was "corrected" by removing soil from the opposite side of the tower from the lean. I'm no expert but supporting two sides of the concrete slab with those perimeter piles could unevenly stress the slab and lead to cracking, or cause the clay on the opposite side to the lean to become more compressed and drop. Either way what a fascinating problem to have to fix. Great presentation Grady, keep it up :)
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.
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!
Beautifully explained. You are very easy to listen to and I fully understand the complexities of footings, having worked on bridge foundations during the 1960's where we had to deal with mud. Caissons were used to a depth of between 100 to 120 feet to the limestone river bed to stop the mud moving the piles that were about 30 feet in diameter. Those bridges are still standing!
I wonder if the bored construction of the new foundation piles actually makes the clay settle even more due to it acting as a conduit for water flowing out of the clay layer. Curiously in another project here facing problems with uneven settlement they're trying to drill holes under the part of the building that hasn't settled as much as the other part to make it settle evenly... could they've done that ? It was rather interesting to hear that displacement piles are the standard in SF but given the geologic condition I guess it makes sense. Here a lot of new high-rises have started to require very deep drilled foundations up to 50 or 60 metres deep (not that it guarantees one to meet a hard rock layer however).
The pile sleeves are sealed so they won't act as a conduit once installed but they have to drill to get them installed, so until the sleeves are in place, yes, it will increase the drainage.
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 fascinating thing about Geotechnical Engineering, nothing is guaranteed and the list of unknowns is endless. You have a plan but nature has its own plans
@@oldvlognewtricks No my friend, specifically geotechnical. The materials behaviour is unpredictable. Unlike other materials. Everywhere else, you sort of have an idea of what you're designing and can improve the design.
@@oldvlognewtricks Steel is very controlled. Concrete and wood, nowadays, are quite controlled (and tested regularly). The primary structural materials we work with the design beams, columns, walls and foundations are very well know, quantified materials. Soil? All soil is unique. No 2 samples will ever been exactly the same. Soil is very nonlinear, with water having a massive effect. It's all underground, unreachable, and even detailed borings can easily miss important aspects. So yes, soils do present quite a bit more unknowns than your standard engineering problem.
@@kindlin *So yes, soils do present quite a bit more unknowns than your standard engineering problem.* No, they don't. They're just unknowns that are beyond the consumer's appetite to control. Steel and wood are only so controlled because we take the trouble and resources to do so. Soil would be equally controlled if they went through similarly rigorous processing. I understand it is seen as uneconomical, just as it was to control the manufacture of steel for the overwhelming majority of human history. This is not a function of "quite a bit more unknowns", only the appetite and current ability to control for those unknowns. Before it was practical to control the manufacture of steel it was similarly unpredictable, just as geology was almost entirely predictable until we started involving pressures beyond reasonable tolerances. A problem having a practical engineering solution doesn't stop it being a problem of engineering, and it doesn't make other engineering problems fundamentally distinct. My point that "nothing is guaranteed and the list of unknowns is endless" applies to all engineering stands. Even your venerated steelmaking processes have error bars.
Yeah this is a very good point. Lots of people are talking about how dumb the planners/builders were, HOWEVER, there are many more building built the exact same way in SF and they are all fine. This is a fluke, so it makes sense that everyone was so confident about this project.
Grady, you rock. I'm an engineer by training, a helo pilot for fun, grew up in a house with a nuclear scientist, and data and math and analysis are my gotos. Your book is next to my bed. I read it when I want to learn. Sure, it's not all perfect (see e.g. service loops) but you get it right 99% of the time, which is good enough for government work. Thanks for the detailed analysis of the Leaning Tower Of SFO. I know this is years old, but the reality is this is not a new problem and it WILL happen again. Likely FLA before anywhere else in the world. Best wishes, happy new year, and you scratched my eng itch! Ehud Gavron Tucson, Arizona
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.
This is by far the best explanation of what is happing to the Millennium Tower. It cuts through all the bickering, politics and gets to the current solution. Thanks for consolidating all the confusing reports from the local media and clearly stating the challenges the tower needs to overcome.
A very well presented explanation. When I was in engineering school(1970s), there was a cartoon about how the architect had saved 600 lira by skipping the geotechnical analysis on the tower of Pizza. The problem is that quality control is often skipped now. Much engineering is cookie cutter and people are not properly exercising their brains. Those long slender piles rely on the soil around them to prevent buckling. When a big earthquake hits, the clay may liquefy and the piles could buckle. A very interesting problem. Good Luck, Rick
@@pulaski1 Correct. When I was in grad school for geotechnical engineering(we just called it "dirt" in those days) my professor summed it up that "when we fully analyze a soil sample we then know the properties of that soil plus or minus 100%". Soil is inconsistent and precise calculations are just kidding yourself. When I learned design in the 1970s, we used an overall factor of safety of about 4. It was hidden in a combination of places in the calcs(loads and allowable stresses). This was conservative and bean counters decided we could use a load factor reduction calculation to save money. I estimate that the factor of safety was lowered to 3. At the same time, chinese steel started being imported. American steel had gotten very good at being consistent. The imported was very inconsistent. I warned my employer about substituting imported steel but they did. It failed at 1/6 the required strength. I was fired for knowing too much. There have been a lot more new construction failures than there used to be. One of the big problems here is the layer of garbage and fill. You just can't know what its going to do. I live on the east coast, so I'm more familiar with problems here. In Boston, they ran piles through their fill layers to bedrock. That works well until there is an earthquake. The fill can turn to a liquid from vibrations. Without the lateral support of the piles, they can buckle and fail. There is an earthquake that hits Boston every 200 to 300 years. It last hit in 1755, centered on Cape Ann. It will be scary. Good Luck, Rick
@@richardross7219 , Two things you don't build on: sand, or clay. Clay never stops squeezing out from under the load, and water easily moves sand. I know there are methods to shore up foundations, such as the piles, but mother nature has a way of proving engineers wrong. It's never what we know that gets us; it's what we don't know, or didn't foresee that bites us. The engineers apparently didn't foresee that other buildings would be built in the area, affecting the ground under this building. Now toss in an earthquake.....yikes
Structural engineering is straight forward. We know the properties of materials, control the shape of the members... soil... that's a whole different animal. All a soils engineer can do is get a reasonable assumption of the underlying material based on limited boring and other means at the time of the soil report. At the end of the day it is a guess work based on one's experience. Could the effect of de-watering have been anticipated? Maybe, but after the design has been approved the construction goes on and the design team is basically done.
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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.
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.
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.
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.
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?
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.
😂
@@MikkoAPenttila yea i know i was just quashing any doubt left
Because it all kept sliding downhill.
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.
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 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.
People need to understand it's antisemitic to criticize semitic companies and it is antisemitic to criticize semitic industries ..!
@@operacarmenhuh? What’s a Semitic industry? Are Jews forced to work in certain industries?
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.
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.
“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)
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 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 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
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.
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.
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.
“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.
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.
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.
It was inevitable from the start. Most locals knew it within 6 months.
Any new updates?
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.
😂
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
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.
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.
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.
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.”
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.
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.
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.
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 !
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 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!
"Soils don't care about property lines." Succinctly put and true of Nature in general. And I think this channel Rocks!
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
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 TH-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.
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 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..
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: th-cam.com/video/gQK21572oSU/w-d-xo.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.
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.
This video is out of date. They did go ahead with the external pile idea but they only installed 18 instead of 52. The change was required when the sinking of the building accelerated as they drilled holes for the piles. The planned fix is complete. Things haven't gone according to plan. They weren't able to raise side that had sunk has much has they had hoped, the plan was for the side that hadn't sunk to gradually sink to the level of the side supported by the new piles. Unfortunately that side isn't sinking so it looks like the building will remain out of plumb for the foreseeable future. However the 3 meter thick concrete mat is now sinking in the center. this is caused by the stress of the building being suspended on two of its sides. It would help if some of the original piles began to take up more of their share of the load. So far it seems they don't intend to cooperate.
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.
"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.
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.
The TH-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 😄
That was a great video.
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!!!
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 🙏🏾
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.
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.
Every video you ever make is so absolutely interesting and insightful! As an engineer myself I still constantly find myself learning bits and pieces from your videos. Keep up the great work!
Yeah... I remember the fist time I heard about the Millennium Tower in our local news... they were showing residents setting down a ball on their floor and watching it roll (with some speed) towards the corner of their condo. At first I wasn't sure what I was seeing, little did I know it would turn out to be a huge problem like it did. The building also had broken windows high up, they said "wasn't caused by the settling" but if not, then that's odd, and you mentioned the trans-bay terminal, I think it had problems from settlement too, they had to close the road under the crossing, rerouting the buses and vehicle traffic, making a real headache... I think the steel support beams were cracking so for that they put jacks while they retrofitted the supports... that whole area is just a hot-mess of construction issues plaguing both of these projects. I'm glad I don't live in S.F. but the whole SF Bay Area is an earthquake disaster area waiting to happen.
I love your content you have educated me so much on general engineering thank you so much keep doing what you're doing your efforts are bountifully appreciated
Grady, I'd love a ~1 year update on this project as the saga continues!
I'm curious as to how the structure's settling impacts its connections to the power, water, and sewer lines. How often do these connections have to be disconnected, moved, then reconnected? Or is my understanding flawed? (Notes: I'm consistently amazed at the high level of production for Practical Engineering. I'm not an engineer, but even I can understand the issues with the straightforward presentation and absence of technical jargon. There's no way I'd live in this tower, having to trust the assurances of perfect safety juxtaposed with the previous false assurances of reliability seems obtuse.)
There are several civil engineers who have said that sewer lines are in serious jeopardy of failing due to the building no longer sitting level so the gravity fed sewer lines could drain properly...the building is doomed
With four feet of drop I'm wondering how they walk thru the front door...
@@billiamc1969 This is a small problem. At worst a sump will be constructed for the sewage and lift pumps will be installed to take the wastewater into the sewage system. The building may have been built with this design from the beginning.
You probably would not be able to afford to live in this tower. One of former condo owners is former quarterback of the San Francisco 49ers, Joe Montana.
You won’t see me living above the fifth floor or in a basement. Lessons learned from living in NYC! Five floors is all my asthma and arthritis can handle. I’m allergic to mold and have a fear of drowning.
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.
Grady, you speak very well and explain things so the average person can understand. I sure hope the building will one day be 100% and all the residents can live happily ever after.
Mike
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.
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.
"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 remember seeing a news story on this and the video that showed items rolling towards the windows. It was a pretty noticeable tilt for things like a table as well.
"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"
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 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!
Thank you for that VERY interesting report !!! It is always fascinating to watch the videos you make on Civil Engineering - absolutely love them !!
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
Reminding me of the Florida condo collapse, even if it is unrelated technically. Who wants to live in a condo where the slight chance of high future repair costs and inconvenience far outweigh the thought of having a cozy little place to live. Great presentation. Thank you.
In the case of a building as big as this, I wouldn't want to even live near it
That condo was demolished it wasn't a collapse. The 3rd set of charges failed initially. They rewired it in less then 24 hours.
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.
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
Scary! Funny, we (Toronto) have the total opposite problem. Our entire substrata is solid rock, that is rising, or rebounding, up to 1-3 cm per year, why? During the last Ice Age, where Toronto currently sits, was 2km of ice, it’s immense weight pushing the ground down. Since the last glacier retreated, the ground has continued to rebound to this very day. It’s great for stable foundations, hence the explosion of skyscraper construction over the last 15 years (we now have the most skyscrapers in North America, second only to NYC)….but despite all those heavy towers, the solid rock beneath our feet continues to rise, creating numerous issues that we’ve now learned to overcome. After the initial foundations are dug, and it’s walls securely in place, they install countless rods into those walls, and wait approximately 3 months. If the rods begin falling out, they must wait until the foundation has sufficiently equalized before pouring the base slab. To do so too soon, could result in the same problem the tower in this video has, but for totally different reasons. However, with hundreds of skyscrapers recently built, under construction, or awaiting approval, it seems they’ve conquered this problem…if only they’d use quality materials. Dozens of condo towers, most by the waterfront, owned by a Chinese consortium, were built with the cheapest materials possible, resulting in brand new buildings falling apart. They’ve had to replace all the windows and glass panels after a series of disasters, with huge glass slabs falling off from 40+ stories up, crashing to the ground, I’ll never understand how they received final approval before allowing tenants to move in, when these building were falling apart! Someone is getting rich from bribe money! My co-worker was unlucky enough to have bought one of these units, a 650 sq ft 1BR unit on the 45th floor. The day she moved in, none of the doors would close fully, her balcony door was frozen in place, due to installing all doors and windows, before the concrete had cured sufficiently, causing all doors and windows to be immobile. She had no water in her kitchen, the drains weren’t even connected, forcing her to use her bathroom sink for everything. Then, as winter approached, all her windows and balcony glass panels fell out, nearly killing several people on the street below! She paid $1.1 million for it, yet it was like living in a slum! All the residents hired a lawyer and sued the developer, but surprise surprise, they were in China, refused to do anything about it, and hid from our officials, after making billions off this disaster. So, all owners were on the hook to pay for all repairs! Luckily, city council knew they screwed up, as that building, along with over a dozen others, all built by the same crooked, criminal consortium from China, should NEVER have been given final inspection approval. Knowing the people would sue the city as they were unable to sue the developer, the city quietly paid for all repairs, costing we, the fax payers, well over $300 000 000!!! (The feds paid most of it). The moral of the story? BUYER BEWARE!!! ESPECIALLY IN TORONTO AND VANCOUVER ( Same Chinese developers did the same in Vancouver over 20 years ago). This is why I prefer to rent, owning is now a game of Russian roulette…if I do finally buy when I retire in a few years, it will be in a well established, older building, that was built properly.
Curious to know if any of the property values dropped in the surrounding areas that would be directly affected if this thing ever collapses. Or is all of SF still greatly overpriced no matter how risky it may be to be there?
@Jason Rackawack You can count on it. Properties are based on the "comps" of the area. When there's a shift in value of a given property, up or down, the surrounding properties shift in the same direction. SF has lost a lot of real estate value in the past two years including the rents which have dropped by more than half in a lot of districts. The city has become a sewer. Very sad, but, considering the so-called leadership, no surprise.
Or is all of SF still greatly overpriced no matter how risky it may be to be there? - YES, yes, and YES. My wife and I have been in the city 10+ years and have rent control but live an older building (as nearly all are). The buildings rent is $3200 month for a one bedroom apt. This should tell you everything you need to know. My guess is the person that replied before me, does not live here and watches too much propaganda.
@@WildWestGal I grew up in San Francisco in the 60s and have been very sad to see the way the politicians have ruined the city with their misguided policies. Some day, people of San Francisco might just wake and and start electing people that actually represent the cities best interests and not the special interests and large developers.
@@jonathanmayberrydesigns 🤯
@@WildWestGal clearly doesn't live in San Francisco and knows nothing of it.
If rents had dropped by more than half, 6 million people would be having a party on a scale that could seen from space.
Our real estate values are rediculous by any other standard (and have nothing to do with "leadership" good or bad) ...but "overpriced" is subjective and the local market, silly as it may be, is remarkably consistent and, good or bad, supported by the biggest industries and companies in the modern world. It stops growing at times in spots but doesn't really drop in any serious way. It dipped a bit during the pandemic - maybe shedding the previous 2 years' rediculous growth...at most. Not half. Not near half. Most sellers just wait out these dips.
Most people's complaints about the city amount to that its become too shiny too quickly, not that its become a "sewer". We do have a serious homeless problem, exacerbated by greedy absentee speculators buying in and throwing longtime local residents out on the street to double the rents. If anybody has a great easy solution to that (that doesn't involve concentration camps or heavy-handed no-outside-ownership laws like you see in some decolonized countries) we're all ears.
We're spending a tremendous amount of money building affordable housing on a tiny peninsula that was full a century ago. We've nowhere to expand but up. We're building the tallest residential towers in this half of the country. What else are we sposed to do?
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
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
This was a great documentary; informative, interesting, and very well-presented! Thanks so much, Grady!
Great video as always. Being from Boston I've always heard about how the city is built on filled land. I'd love to hear you do a video on how this was historically done and the effect that has on building up to the present
Always scared every time I drive by it, especially when I'm on the Bay Bridge. I'm always thinking "Not today please"
Thanks!
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.
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.
Interesting video, brings another question to mind. The hydraulic pressure of the building which when fully furnished will out mass it's neighboring structures, will this have an effect on their foundations as well as the downward pressure tends to push against four opposite sides. Would this not create lift to the others or are the neighboring foundations already densely compact
Or simply Millenium is the only one that not compacted enough. It's kind like the depth of the soil wildly varied.
Is the question based on the idea that as this building continuesto sink it is displacing a certain volume of soil and that needsto go somewhere?
@@shopshop144 It's displacing ground water out of clay soil.
@@Kieselmeister ok so this won't disrupt it's surrounding earth, compressing only under it. Yes that was my question
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 have so many more questions than the answers provided here. For instance, what keeps the new piles, that are both longer and also hitting the bedrock, from bending in the softer old bay clay layer? Will all of the layers react as one in an earthquake or can they shift against each other, generating shear forces against the piers? The fix will rely on hydraulic jacks to transfer the weight to the new piers and it seems the jacks will simply be left holding the weight. What if one fails? What if that failure, and the resulting increase in weight on the others, causes them to fail in cascade?
I get it that the new piles are expensive, but why wouldn't the solution be extended to the entire perimeter of the building? Are they using a drilling sequence like an automotive head bolt torquing sequence, or just perforating the layers along the edges that are currently compacting the fastest?
I also wonder about what adding additional force to the other side is going to do as they "press" the building upright? Seems like that would surely have some potentially unforeseen consequences for the settling behavior of the opposite side of the building. Seems like an insanely complex and difficult situation.
Something that I wasn't even thinking about. In an earthquake you hear all the time about the different layers shifting in relation to each other.
Hydraulic driven screw jacks using multiple planetary gears for reduction. You just scale it bigger to match the weight needed to be lifted. Mass matters. It will require several working together.
Soon enough, these tall buildings in San Francisco will be earthquake tested. Then, we will have our answers, and the engineers will have their grades. Do far, they've earned a "D".
I have a question Ive never seen addressed, when the building sunk this much, isnt the entry into the lobby much lower than the sidewalk? Did they have to change anything or add a step down into the lobby when you enter from the street?
Good question and no one has answered this yet, as far as I know.
Henceforth the lobby will be referred to as "the basement" and all additional floors will be renumbered accordingly, thanks in advance for your cooperation- the management.
@@buckodonnghaile4309 🤣🤣🤣
The sidewalks adjacent to the building are attached via reinforcing steel into the concrete of the building itself, so as the building sinks, the sidewalks closest to the building sink along with it. This causes the sidewalk to buckle and crack, which is one of the first signs engineers noticed that the building was settling at a much faster rate than had been anticipated.
@@buckodonnghaile4309 maybe they could just put pieces of tape over the elevator numbers and relabel accordingly.
I didn't see anything that addressed what happens when/if they get the perimeter piles installed, and the building does eventually level itself. The sides that don't have perimeter piles will just keep sinking after the building goes level.
I'm assuming they will have to install pilings on the other 2 sides, I just found it odd that it wasn't mentioned.
They should be able to open the vaults and release some of the pressure from the hydraulic leveling jacks.
Well done with excellent graphics. But you fail to mention that the original plans were for a steel beam structure. This was then changed to concrete form, without adjusting the proposed foundation. Ostensibly (HA) to save money!
As a political science major with absolutely no experience in the construction industry, I really appreciate and enjoy the way that you are able to summarize and present complex engineering issues in a way that even I can understand them. Thanks for your effotst
Socialists can't build anything right.
I guess it boils down to two options, either push up (support) the side that's sinking, or drop the side that isn't. The leaning tower of Pisa was "corrected" by removing soil from the opposite side of the tower from the lean. I'm no expert but supporting two sides of the concrete slab with those perimeter piles could unevenly stress the slab and lead to cracking, or cause the clay on the opposite side to the lean to become more compressed and drop. Either way what a fascinating problem to have to fix. Great presentation Grady, keep it up :)
Do you mean Pisa in Italy ?🤔
@@Deepthought-42 Doah! more haste less speed. Well spotted!
@@Stephen_Black ;0)
@@Deepthought-42 Considering I've actually been there, that was an epic mistake!!
@@Tom-zy6ke 👍As an engineer who has always had difficulty spelling, I shall be enjoying my pisa tonight 😉🤣
“How do engineers predict how soil will behave under extreme loading conditions?”
Often poorly, it seems
*Occasionally* poorly, it seems
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.
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!
Beautifully explained. You are very easy to listen to and I fully understand the complexities of footings, having worked on bridge foundations during the 1960's where we had to deal with mud. Caissons were used to a depth of between 100 to 120 feet to the limestone river bed to stop the mud moving the piles that were about 30 feet in diameter. Those bridges are still standing!
Interesting!
Now we see the difference between public and private works. Public works for the people and the private works just for profit.
@@RRaucina Public Works = Chernobyl.
@@francismarion6400 Public works in the USSR were private money making projects for the party leadership even then.
I wonder if the bored construction of the new foundation piles actually makes the clay settle even more due to it acting as a conduit for water flowing out of the clay layer. Curiously in another project here facing problems with uneven settlement they're trying to drill holes under the part of the building that hasn't settled as much as the other part to make it settle evenly... could they've done that ?
It was rather interesting to hear that displacement piles are the standard in SF but given the geologic condition I guess it makes sense. Here a lot of new high-rises have started to require very deep drilled foundations up to 50 or 60 metres deep (not that it guarantees one to meet a hard rock layer however).
The pile sleeves are sealed so they won't act as a conduit once installed but they have to drill to get them installed, so until the sleeves are in place, yes, it will increase the drainage.
Your point is valid, would love to see the pile detail and construction spec
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 fascinating thing about Geotechnical Engineering, nothing is guaranteed and the list of unknowns is endless. You have a plan but nature has its own plans
*fascinating thing about engineering
@@oldvlognewtricks No my friend, specifically geotechnical. The materials behaviour is unpredictable. Unlike other materials. Everywhere else, you sort of have an idea of what you're designing and can improve the design.
@@karabo933 “sort of”
@@oldvlognewtricks
Steel is very controlled. Concrete and wood, nowadays, are quite controlled (and tested regularly). The primary structural materials we work with the design beams, columns, walls and foundations are very well know, quantified materials.
Soil? All soil is unique. No 2 samples will ever been exactly the same. Soil is very nonlinear, with water having a massive effect. It's all underground, unreachable, and even detailed borings can easily miss important aspects.
So yes, soils do present quite a bit more unknowns than your standard engineering problem.
@@kindlin *So yes, soils do present quite a bit more unknowns than your standard engineering problem.*
No, they don't. They're just unknowns that are beyond the consumer's appetite to control.
Steel and wood are only so controlled because we take the trouble and resources to do so. Soil would be equally controlled if they went through similarly rigorous processing. I understand it is seen as uneconomical, just as it was to control the manufacture of steel for the overwhelming majority of human history.
This is not a function of "quite a bit more unknowns", only the appetite and current ability to control for those unknowns.
Before it was practical to control the manufacture of steel it was similarly unpredictable, just as geology was almost entirely predictable until we started involving pressures beyond reasonable tolerances.
A problem having a practical engineering solution doesn't stop it being a problem of engineering, and it doesn't make other engineering problems fundamentally distinct.
My point that "nothing is guaranteed and the list of unknowns is endless" applies to all engineering stands. Even your venerated steelmaking processes have error bars.
It’s pretty amazing that this was such a weird occurrence. A majority of massive buildings are fine to stand far after the expected lifespan.
Yeah this is a very good point. Lots of people are talking about how dumb the planners/builders were, HOWEVER, there are many more building built the exact same way in SF and they are all fine. This is a fluke, so it makes sense that everyone was so confident about this project.
ONLY when the foundations go to bedrock!
As a former resident of San Francisco, I enjoyed this.
As a person who has at one point lived in a skyscraper, I enjoyed this
Grady, you rock.
I'm an engineer by training, a helo pilot for fun, grew up in a house with a nuclear scientist, and data and math and analysis are my gotos.
Your book is next to my bed. I read it when I want to learn. Sure, it's not all perfect (see e.g. service loops) but you get it right 99% of the time, which is good enough for government work.
Thanks for the detailed analysis of the Leaning Tower Of SFO. I know this is years old, but the reality is this is not a new problem and it WILL happen again. Likely FLA before anywhere else in the world.
Best wishes, happy new year, and you scratched my eng itch!
Ehud Gavron
Tucson, Arizona
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.
This is by far the best explanation of what is happing to the Millennium Tower. It cuts through all the bickering, politics and gets to the current solution. Thanks for consolidating all the confusing reports from the local media and clearly stating the challenges the tower needs to overcome.
A very well presented explanation. When I was in engineering school(1970s), there was a cartoon about how the architect had saved 600 lira by skipping the geotechnical analysis on the tower of Pizza. The problem is that quality control is often skipped now. Much engineering is cookie cutter and people are not properly exercising their brains. Those long slender piles rely on the soil around them to prevent buckling. When a big earthquake hits, the clay may liquefy and the piles could buckle. A very interesting problem. Good Luck, Rick
Tower of pizza, lol
I believe several building will fall when the city gets it's next large earthquake!
@@pyhead9916 Very likely. Watch "Idiocracy". There's a scene that shows a city with buildings tipped.
@@pulaski1 Correct. When I was in grad school for geotechnical engineering(we just called it "dirt" in those days) my professor summed it up that "when we fully analyze a soil sample we then know the properties of that soil plus or minus 100%". Soil is inconsistent and precise calculations are just kidding yourself.
When I learned design in the 1970s, we used an overall factor of safety of about 4. It was hidden in a combination of places in the calcs(loads and allowable stresses). This was conservative and bean counters decided we could use a load factor reduction calculation to save money. I estimate that the factor of safety was lowered to 3. At the same time, chinese steel started being imported. American steel had gotten very good at being consistent. The imported was very inconsistent. I warned my employer about substituting imported steel but they did. It failed at 1/6 the required strength. I was fired for knowing too much. There have been a lot more new construction failures than there used to be.
One of the big problems here is the layer of garbage and fill. You just can't know what its going to do. I live on the east coast, so I'm more familiar with problems here. In Boston, they ran piles through their fill layers to bedrock. That works well until there is an earthquake. The fill can turn to a liquid from vibrations. Without the lateral support of the piles, they can buckle and fail. There is an earthquake that hits Boston every 200 to 300 years. It last hit in 1755, centered on Cape Ann. It will be scary. Good Luck, Rick
@@richardross7219 , Two things you don't build on: sand, or clay. Clay never stops squeezing out from under the load, and water easily moves sand. I know there are methods to shore up foundations, such as the piles, but mother nature has a way of proving engineers wrong. It's never what we know that gets us; it's what we don't know, or didn't foresee that bites us.
The engineers apparently didn't foresee that other buildings would be built in the area, affecting the ground under this building.
Now toss in an earthquake.....yikes
Structural engineering is straight forward. We know the properties of materials, control the shape of the members... soil... that's a whole different animal. All a soils engineer can do is get a reasonable assumption of the underlying material based on limited boring and other means at the time of the soil report. At the end of the day it is a guess work based on one's experience. Could the effect of de-watering have been anticipated? Maybe, but after the design has been approved the construction goes on and the design team is basically done.