What's REALLY Causing Millennium Tower to Sink and Tilt - Is the Developer at Fault?

Understanding the real reason why the Tower is sinking into the San Franciscan soil is fundamental to further investigation on this case.
If you haven't watched the first video on this series, see it here: • San Francisco's Most E...
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The 𝘾𝙝𝙖𝙢𝙥𝙡𝙖𝙞𝙣 𝙏𝙤𝙬𝙚𝙧𝙨 𝙎𝙤𝙪𝙩𝙝 𝙥𝙡𝙖𝙮𝙡𝙞𝙨𝙩 showcases Josh Porter’s expert analysis of the tragic Surfside condominium collapse. Josh’s ability to explain complicated material in a way understandable to anyone has created a high demand for his instruction. You can get it right here for free, at your leisure.
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#BuildingIntegrity #Millenniumtower #Leaningtowerofsanfrancisco
Disclaimer: Nothing contained within this video should be construed as legal advice. Building Integrity makes no claims of its own regarding the guilt or innocence or liability otherwise of any legal entities mentioned in any of their videos. These videos are made for news/informational and educational purposes only.

[@JoeyCarb]

A structural engineer explained it to me like if you have one hose in your hand, and you try to pull it out, your hand grips the entire circumference of the hose. If you put 3 or four in your hand and try to pull them out, there's part of each individual hose that has no friction acting on it.

[@martentrudeau6948]

That's good explaining, thanks Joe.

[@Yrouel86]

This analogy works really well with spaghetti, you can easily pick individual spaghetti from the center of a bundle in your hand no matter how much you squeeze it

[@kevinireland8020]

@@Yrouel86 IT is not pulling. There is a HUGE difference between tensile and compressive strength of materials. And neither of these properties is the actual problem. Even I, at 200 lbs., sink in wet clay!

[@grizzlygrizzle]

The way I was conceiving the problem is that when you get the pilings too close together, the dirt in between them is "dragged down" with the pilings' friction pulling on them downward. If you have a narrow column of dirt between 3 or 4 pilings, then the dirt acts as an extension of the pilings, being pulled down as a sort of unitary bundle of pilings and dirt. (Consider the case where the pilings are adjacent-- the dirt in between them becomes an extremely skinny column of dirt with very little bearing capacity, and in terms of the pilings sinking, that very skinny dirt-column's resistance is reduced to the area of it's base in between the columns. If the pilings are far apart, then each piling acts more like a single piling, and the dirt adjacent to it behaves more like undisturbed soil, and exerts friction on the pilings. Of course, the friction exerted ultimately depends on the bearing capacity of the dirt, but the friction between piling and dirt spreads out or dissipates the downward force of the piling along its length, instead of concentrating it in the area of the bottom of the piling. -- A solitary piling, exerting friction against the dirt, will not ONLY affect the dirt immediately adjacent to it, but that downward force will be dissipated outward, like the way a pile of sand can form a cone with an angle of about 45 degrees. Given the granular and interlocking texture of dirt, a downward force in one place will spread out, so friction around a piling will dissipate outward and take advantage of the bearing capacity of a wider area of dirt. But if that nearby dirt is full of pilings that are also being pulled down by gravity, it nullifies the upward bearing capacity of those regions of dirt. -- And of course, clay makes things a lot more slippery and complicated with its plasticity. -- I'm not an engineer, but this is how I make sense of what is being presented here.

[@dr.ryttmastarecctm6595]

Considering the risk of liquefaction during an earthquake, I wouldn’t live anywhere near that tower let alone in it!

[@bpnoithasnt]

Completely agree.

[@davidb6576]

That's part of why I'm incredulous that the design was allowed. Someone(s), somewhere got a bunch money to look the other way...

[@shape5685]

Considering the political environment at play in that area, I wouldn't live anywhere near San Francisco or California for that matter

[@iv2sab512]

@Lurking Grue It's a beautiful to place to live, no doubt. I just wouldn't want to live near that building.

[@imoldgreggboosh3467]

@@shape5685 Good.

[@JasonFlorida]

As someone who has worked as a designer in the construction industry for many years, I can really see how you came to this conclusion. I really like how you analyze and speak so clearly and concise. I absolutely can see that scenario play out between the developers, architects, and engineers. I have seen first hand developers/builders pressure engineering firms to sign off on the least expensive options just in the name of profit! Sad, really.

[@martentrudeau6948]

I have worked in architects and engineers offices for decades and have seen the same pressures on the consulting engineers.

[@davehall44]

@@martentrudeau6948 Screw ups can be caused by one strong member leaving the team leading to an uncertain outcome. An earthquake can show up the result.

[@chemech]

And every now and again, you find an engineer who is willing to shave into the safety margins in a design, relying on the code's safety factors to too great of an extent. The financial pressures on an A&E firm are tremendous, but if you are the PE in Responsible Charge of a design, it's your own personal fundament on the line, and you had best cover it well...

[@lindap.p.1337]

Follow the dollar, as usual.

[@jeffreynelson2660]

@@chemech I have seen recently that engineers in advanced age are willing to stamp questionable projects as they are not likely to be around when a problem occurs and need the money to supplement their SS.

[@thechumpsbeendumped.7797]

It’s hard to believe that all this could have been caused by trying to save $4 million on a project of this size. By the time this is all cleared up and the building is demolished it’s gonna cost billions.

[@kencarp57]

I agree. I just wonder how long they’ll dick around in court before it becomes too obvious to ignore that the building is going to have to be demolished before the whole thing falls over. What a nightmare!

[@bobbycrosby9765]

About 1% of the cost of the building. It also comes to $10k per unit. For condos that start at a million bucks.

[@werewolfnar]

Never underestimate how penny pinching corporations of any sort get. At some point the board and investors are detached from the end result and only care about getting $.05 more return per share. Penny wise and pound foolish.

[@Nic7320]

Hindsight is always 20/20.

[@leviathan68w78]

This kind of thing happens all the time in construction. People do everything they can to save money upfront fully knowing that it may cost them more later on. Gambling basically. Human beings do this in every walk of life; taking large risks because it might payoff. They can definitely retrofit this foundation though. I don't think they are going to tear it down.

[@lorismith9105]

I never in my entire life thought I would find this interesting. The way you explain these engineering facts have this nurse absolutely fascinated. Wow. Great job. Seriously amazing

[@BuildingIntegrity]

Thanks!

[@shAnn0n1]

Great explanation of the friction pilings acting in a group...the picture of the pilings was crazy looking, but I could totally understand what you were saying about pilings. I looked up all the news pertaining to the Millennium building and you're right...everyone could explain the symptoms and the sinking, but no one introduced a way to fix it. A lot of lip service. 💋. As always Josh, you are a great storyteller and you make it easy for us to understand and easy for us to get excited about learning something new. And who knew about old bay clay...so interesting 🤔.

[@solarnaut]

what *shAnnOn* said ! B-)

[@artsmith103]

Each piling is kind of dragging soil down. 1 piling with suitable friction cannot move soil. A collection of pilings dragging on the soil from multiple directions and closer spacing can drag the soil

[@gorillaau]

950 pilings? I'd love to know how far apart they were sunk.

[@CatCube2]

For the engineer to try to blame the developer for picking the "wrong" option is infuriating. YOU PUT THIS DESIGN ON YOUR F@#$ING DRAWINGS AND STAMPED THEM. IF YOU DIDN'T BELIEVE IN IT YOU SHOULDN'T HAVE DONE THAT. If you are a licensed professional, you're sometimes going to have to reach down, grab your n*ts, and say this isn't going to work and I'm not going to do it. The buck stops with you. That responsibility for safety can ultimately be pinned to a specific named person is the only reason to have licensure in engineering. If you can't handle that, work under another PE instead of getting your own stamp. If we aren't willing to enforce that on our members, then licensure is just a racket and we are a self-licking ice cream cone as a profession.

[@min3063]

I looked at acquiring this site with my old company in the mid 2000's. Our head of construction ran a calculation and concluded that we would need to friction pile to the bedrock or pile 150ft as a floating island to build it safely (this diligence took him 1 minute). This was the developers choice to save money on the friction pile plain and simple.

[@davefoc]

@Analog Human Is there something about a friction pile that makes it not work if the end hits bedrock?

[@uzlonewolf]

@@davefoc It's no longer a friction pile if it's resting on bedrock.

[@spejic1]

@@uzlonewolf It's resting on the bedrock, but the bedrock is not supporting the whole of the weight, just part of it. The weight is also being supported by all the friction along the whole length of the pile.

[@davefoc]

This is sort of like the bolt/screw distinction. Screw it in to a tapped hole and it's a screw. Screw it in to a nut and it's a bolt. I never liked that. A thing is the same thing regardless of how it is used. But there are a lot of things I don't like in this world and this is pretty low on that list.

[@davefoc]

This is interesting and it supports the main point of this video. If the engineering calculations are as obviously wrong as you suggest the only party that is responsible for this mess is the engineering company. Most of the time I have been aware of this problem I had an idea that the engineers were unlucky. Nobody can predict exactly the load bearing capacity of a particular location. But this sounds much more like the engineers made horrendous mistakes and failed to consider routine issues associated with this kind of foundation.

[@odess4sd4d]

This is a very plausible, even likely explanation. Foundation designers always think they are communicating risk to owners but all the owners hear is cost. It has played out a million times.

[@DanielCarpenterLightMan]

You are the most intelligent, well spoken and to the point person on KZbin. On any subject.

[@brianbender7438]

Perfect explanation. I live in the SF Bay Area and have followed this story for months and this is the clearest, most concise piece on the situation. Local TV news just rambles along for 90 seconds or more with hype-nothing of real substance. I come here to learn the real story. Thanks, Josh. I hope you will do another segment on the proposed fix, which is costing way more than the $4M they would have spent drilling to bedrock in the first place. Wow.

[@francismarion6400]

I would contact Elon to attach some rockets to one side and pull it back over. Or tow it to Mars. LOL

[@scofab]

Ya... four million is gonna look like a pee in the ocean once this debacle is settled. Hard not to laugh, hard not to cry. Great job, thanks as always.

[@emmabovary1228]

What your describing reminds me of being on the beach and trying to push several same sized pegs into the sand close together. By the time you get to the 3rd or 4th peg, they are leaning or being pushed back up by the force of the 5th one. Thank you Josh. Your work is fascinating to me and I appreciate all your time in making these videos.

[@markr.devereux3385]

Interesting example❤️

[@kaiserpuppydog7174]

It's very troubling that I understood your explanation perfectly, even though I know very little about engineering...yet all these professionals involved could not see the problem? How could this have happened?

[@geoffh4861]

It's a combination of blatant corruption by the original engineer and architect with the complexity of resolving these things in court. Another aspect that hasn't been covered (which I hope will be in a future video), is that the soil dewatering from the nearby development would only accelerate the sinking, but not actually affect the magnitude of the sinking. This building was going to sink this bad even if the Transbay Terminal project never started.

[@JanBruunAndersen]

As a wise man(?) once said, it is hard to get someone to see the truth when his or her salary depends on being wrong.

[@frederikqu7717]

I assume that either the engineer was absolutely incompetent or ruthless, or bribed or blackmailed. This is a problem that an electrical (!) engineer in the midth of his studies should have seen. So seeing this should be a no brainer for any experienced construction engineer

[@WindTurbineSyndrome]

Money, greed, and lack of concern pass the buck down the road mentality

[@GoCoyote]

@@geoffh4861 Someone once told me to be careful not to attribute to malice that which can be attributed to ignorance and stupidity. Engineers make mistakes, and some engineers have big egos that make it difficult for them to admit their mistakes. The "Murphy's Law" "If anything can go wrong, it will" was not meant to be fatalistic, but a design tool to help rein in the hubris of engineers, and help them to use the assumption that any design CAN FAIL. Therefore they should look for and try and minimize those failure points, instead of assuming their plans will work just because they believe that they will. I watched the drilling for the piles on the millennium tower every morning and evening on my way to work and back, and you could tell when they hit the Old Bay Clay, as it is the gooiest stickiest stuff you ever messed with.

[@greybeard1233]

Interesting explanation! But what I am really appreciative of is the amount of searching and reading you had to do to come up with this. Searching the time during planning and permitting and discovering why the foundation was built this way. Great job, bet it took a lot longer than explaining what you found.

[@ehsnils]

Many years of education and experience is what you pay an expensive consultant for. It may take them 10 minutes to put the comma in the right place but knowing where to put it is what you really pay for.

[@lwilton]

As you were talking I was sitting here wondering if fewer friction piles might have actually been slightly better than the nearly solid pack they seem to have used, but in the end I decided the difference would probably have been moot. You still have essentially a plug of pilings and sand pushing down on the clay. Maybe you would get some increased friction on the outside row of piles, but likely only for the top few feet where it doesn't really matter much. I'm also inclined to wonder if it mattered what pattern they used to set the piles. Each pile is going to displace the sand as the pile is driven, and that will displace largely to the sides. If you drive two piles close together, the first will displace equally in all directions (given homogenous material conditions), but the second will have some increased displacement resistance in the direction of the first pile. If you have a wall of close spaced piles and drive more piles next to it, you now have a condition where the soil on the side of the pile wall is effectively denser than on the open side. So I'd expect more soil to displace to the open side than thru the pile hedge. So if you drive all of the piles from one side of the foundation to the other side, what effect does this have on the relative soil density in and around the final pile pack? And what effect does this density variation have on pile friction resistance? Is the building tilting toward the side where they started driving the first piles?

[@Gregorius421]

Might be this the reason for the uneven sinking?

[@BlahBleeBlahBlah]

Great question, hopefully Josh will see it and give his point of view.

[@RealButcher]

Very good question.

[@tissuepaper9962]

AFAIK they don't go straight down the line, but start by driving every other pile, and then drive the remaining piles in between.

[@bilbobaggins3336]

Great explanation. I have no prior knowledge of engineering concepts but you explain everything in layman's terms that I understand. Looking forward to the next video.

[@truckerallikatuk]

If those piles are that close to each other, won't they just hold a stationary lump of soil between them? There won't be enough room for the soil to move to create friction,

[@d00dEEE]

That's correct, the coupling between the pilings is a function of the distance between them. An easy thought experiment is to simply imagine square piles increasing in size until they touch, with no intervening soil. When the distance reaches zero, they are still distinct columns, yet the skin friction has dropped to zero (except for the outermost piles in the group).

[@Sashazur]

@Jim Jones this whole video is about how more piles is NOT better, if they are too close together.

[@postie48]

@3402 Why not - that was the way we thought about it when I was helping in the design the foundations of what woul have been the biggest cooling tower in Europe (not built!)

[@michaelrexrode3759]

That seems likely to me!

[@brnmcc01]

@@Sashazur That's correct, because if you put in a million more piles, now you have to start also calculating the weight of all those extra piles, which then requires more piles, and then.... you get the idea, building design starts to run away, and becomes heavier and heavier and becomes impossible to support itself. Then what happens when people move in, and start installing all the granite countertops, furniture, live loads etc etc. Throw it all away and start over. That's a big reason engineers try so hard to keep a building as light as possible, and cut out any dead weight, that does not contribute efficiently to supporting the building. Anyone can design a building that will last 'forever' by designing 8 foot thick solid reinforced concrete outer walls, but good luck building a foundation on clay that will support the million or so extra tons of weight.

[@innagottadavida8538]

Another fine lesson, Professor Porter. If you don't teach, you should. You have a talent for taking dry material and making it far more interesting and understandable. It also helps that you're able to build these lessons around real world examples. Other KZbin creators have built up their viewership by making videos about the CTS tragedy but you might be one of the few who retains those viewers as you cover other subjects of equal interest with your extensive knowledge of engineering and diligent research efforts. I look forward to your next video. Maybe you could do future videos about some of those many engineering mistakes you mentioned in this video.

[@Rx7man]

Yep, I came for the CTS tower but I'll stick around a while... I'm a farmer with an engineer brain and I like these analyses

[@francismarion6400]

He could but why would he want to teach? He is killing it in the business world.

[@innagottadavida8538]

@@francismarion6400 He seems like the sort who enjoys imparting knowledge. If not, why bother with these videos?

[@francismarion6400]

@@innagottadavida8538 My number one guess would be to promote his business. I doubt he needs the income from YT vids.

[@innagottadavida8538]

@@francismarion6400 If it was about money, he'd probably make more videos. I think he just finds engineering interesting and wants to share that interest with others. Have you ever noticed that he never mentions the name and location of his business? I don't think he's here to plug but instead to inform. Some people enjoy sharing their knowledge with others.

[@Ten21Inc]

I am not an engineer but enjoy very much your program. You explain things well for layman Well done!!

[@ntopits]

Can I subscribe twice to this channel? What an awesome job Josh does presenting comprehensive and detailed dives into these topics. So compelling and informative!

[@martentrudeau6948]

Fascinating analysis, it sounds correct. -- I can't imagine anyone wanting to live there, it will soon be a non-livable building when the plumbing stops working, because of excessive sloping. Maybe the San Francisco Building Dept. will condemn it? Who knows how to fix it? And If it can't be fixed, then it must be torn down! Wow, what a mess. Thanks Josh.

[@Larpy1933]

Nice! Thanks. You’re getting right into the nitty gritty in a hurry. Your on-screen presentation is clear and I enjoy your careful way of speaking and using language. No muss, no fuss. Totally excellent.

[@vegasbabyy]

I’ve learned more from Josh’s channel then all the other YT channels put together that I watch. He’s so good at making everything understandable. Another great video! 👏🏽 👏🏽

[@corydalus981]

It's unsettling that people who have spent years studying engineering and passing exams so difficult that they are incomprehensible to me, can get so wrong a concept so basic that you were able to make me understand it in a minute or two. The non-engineering forces at work on these people must be brutal.

[@alm5693]

This sounds like a case of the tail wagging the dog who then proceeded to catch the car. Once you framed it as "let's see if we can get THAT deal from the Trans-bay Authority", it makes so much more sense that it happened as it did.

[@garywheeler7039]

Yes, a bluff for money that did not work out.

[@jameskeefe1761]

I've really been looking forward to this video to hear your analysis of this. Brilliant video. Its amazing this all got past the design phase. Definitely much more informative to hear an engineers analysis of this than news reports. It looks like its going to be quite an expensive mistake.

[@artistjoh]

Only 4 million dollars extra to go down to bedrock? That seems like it a drop in the ocean on the cost of erecting that building. Developers usually prefer to spend the money on the decorations that buyers can see, but it is much more important to spend the money on the things that cannot be seen. Just looking at the size of that foundation compared to building height it looks obvious to me that even if friction piles, they should have gone down a lot deeper. OTOH I am the beneficiary of living in a 1980 apartment tower that was so over-engineered that the builder went broke, and a second construction company had to finish the building. I love the lack of problems we have because it is so well built, but I bet that builder wishes he had cut some corners somewhere.

[@mangos2888]

Your apt building story sounds pretty interesting!

[@Cheeseatingjunglista]

@@mangos2888 And hopefully, by the sound of it, pretty quake proof too!!

[@RobMancusoJr]

Thanks for the great content Josh

[@BuildingIntegrity]

Thanks for watching!

[@joespittle1]

Can you make a video on what it would take for the building to fall/collapse? I feel though if we get another big earthquake any time soon that thing's coming down

[@rubyoro0]

Well…they say the big one will come between now and 2030.

[@garywheeler7039]

There is a great book called I think, "Why Buildings Fall Down"! It is interesting.

[@jennyjumpjump]

It's unbelievable to me that the designers only considered friction on the pilings. This seems like such a rookie mistake. If you can't afford to do the proper foundation for the building you want to do, then you can't afford to build that building

[@comment6864]

rookie frookie... more like crookie

[@MajorCaliber]

If you don't stop putting Human Safety ahead of Profit$, we're going to blacklist you over at The Chamber of Commerce, AND cutoff your bribe-income, err, I mean "political donations"... /sarc/

[@gilde915]

tbh ..to risk such an investment on the basis of saving of aprox 4 to 10 mil dollar...100% sure no investor will do such a thing

[@mikes4163]

Even as a non-civil engineer I can see the flaws in this design. I think the bible says something about foundations, but in the US profit seems to Trump everything these days.

[@seriouscat2231]

@@mikes4163, as an European, I think Trump is a Rorschach ink blot. Everyone sees in him a different thing. And I think this is because he is an actor. Not a real politician who would or could represent or understand something.

[@drew10981]

As soon as you said the pylons stopped above the Old Bay Clay, I called out "oh good god, this is hands down the result of a design flaw". And low & behold, that's what you seem to indicate here. Wow. Just, wow. The lawsuits back to the engineering firm who signed off on this design is going to be sued into oblivion in a handful of years after the building is condemned and has to be torn down.

[@tomtom6319]

Great insight on this . This is down the street from me and it’s unbelievable the different stories you hear about this debacle!

[@jamesplotkin4674]

Your production quality is awesome, Josh. The lighting, microphone and background... all top notch. Thanks for your expertise, as well. I have to wonder if half (random number) the quantity of friction piles would have worked much better by giving each pile it's place/space to function as planned.

[@Cheeseatingjunglista]

The original total frictional component of the support requirement for the building would need to be replicated, if you halve the number, those that remain need to double in length - could possibly be mitigated by making each pile of a wider gauge, limited by the existing soil structure problems - what seperation between piles would allow the clay to maintain its structural strength? Might as well of just head for the bedroock from the off

[@davidaxe7635]

Hi Josh, thanks for another wonderful video. You speak with such clarity and authority. Your channel is by far the most fascinating and informative I’ve seen on KZbin. Thanks so much.

[@BuildingIntegrity]

Wow! That means a lot. Thanks David.

[@LJ542]

Interesting and easy enough to follow! Thanks for posting. I look forward to the rest of your videos on this matter.

[@cal-native]

I have to admit I did a double take when the $4 million number came up. I couldn't believe all of this could have been avoided for a relative pittance. Yes, backward vision is always perfect, but as a lifelong California resident familiar with our clay soils, earthquakes, and potential liquefaction, it certainly seems like it would have been cheap insurance against this possibility.

[@islandbirdw]

You sir are a gifted teacher. Thank You 🙂

[@Mrch33ky]

11:48 I work in the legal field and I see attorneys make basic mistakes all too often. Many plaintiffs attorneys seem to think that you can sue for first amendment rights with a private entity and win but your first amendment rights only exist between you, the individual, and the government. The Bill of Rights is only a limitation on the government and nothing else. So the government can't muzzle your free speech but private companies most certainly can because they are under no obligation to respect those rights.

[@Jacks_Suffocating_Nihilism]

With a take like this, I can only assume that you intern with the ACLU.

[@tonydugal5275]

I’ve enjoyed your videos since Surfside. I’m not involved in the building trades, but the KZbin algorithm knew I had an interest in engineering and scientific topics, and steered me to you. I’ve learned a great deal. Thank you, Josh.

[@richardjones5255]

I remember the story of a bridge. Piling was to start and a 'very important person', was going to drive the first pile. The pile driver operator set up the important pile and gave it a gentle tap, it disappeared from view, they then stacked three piles on top of one another, the rush was now on before the VIP arrived. Soil variations between adjacent checks were highly variable and this 'affected' the pile plans.

[@vas4739]

You and these videos are amazing & full of detail!

[@SteamCrane]

As a mechanical engineer, your simple clear diagrams made immediate sense. Looking forward to the next video.

[@thatclintguy]

Videos like this make me really appreciate the fact that the internet/KZbin exist. A+ content, subscribed!!!

[@jameskeefe1761]

One of the things i've wondered about is if the dishing of the mat will cause increased stresses deformation, even cracking, on the structure above. What is it doing to the structure above. Could the columns in the middle might be under much more stress causing more stress on the joints with the horizontal beams further up the building? In an earthquake, it would be interesting to see what would happen to this building. I wouldnt want to live or work within a mile of this thing.

[@tuvelat7302]

The proposed 'fix' of jacking up the low side of the building relies on the integrity of the foundation mat. I don't foresee that going very well if they ever get a chance to try it.

[@brnmcc01]

@@tuvelat7302 Absolutely. The only thing I ever see in the future of this building, is Mark and Stacy Loizeaux installing explosive charges on the next episode of "CDI - The 'Art' of Demolition" :)

[@asc_missions3080]

The dishing will gradually redirect the gravitational force from vertical to an overall lean inward toward the low point,creating lateral pressures on the vertical components that they were not designed to handle. Best case scenario if it does not stop in time, the building collapse into its own center line, but without all the cutting and mass removal that goes into an intentional demolition, it will compress and then twist over or shred and peel up. A really smart computer demolition sim with all these factors implemented would probably give you an elegantly ugly projection of the probable dynamic and its damage footprint.

[@francismarion6400]

Doesn't the finished building structure act as somewhat of a truss?

[@asc_missions3080]

@@francismarion6400 Truss integrity depends on an even distribution of weight according to its design. And a solid unchanging foundation. Gravity resistance is the entire purpose of a truss. All solids are fluid, some just extremely slow-moving. Over time a deformed foundation results in a deformed structure, and that happens most rapidly closer to the foundation and increases as a function of increasing weight from above. Torquing that weight in any direction adds another dimension of gravitational flow. Eventually the deformation reaches a tipping point, which is where the structure has lost integrity and fails.

[@auntielaura5]

As someone with no engineering knowledge, who lived in San Francisco and the Bay Area for more than 20 years, I am astonished that they weren’t required to go down to bedrock. Even individual homes, if they are built on a grade, go to bedrock because earthquakes are *going* to happen. I can’t imagine why the building code allows anything less - particularly for the tallest building in the city.

[@heyyy4783]

The bedrock is what's shaking in an earthquake. If you're in an earthquake prone region, the _last_ thing you want is to go down to bedrock. A layer of soil below your building will cushion the shock waves.

[@Cheeseatingjunglista]

@@heyyy4783 That depends on the nature of the soils below you :- what materials compose these soils, how many distinct layers there are, the physical and consequent structural characteristics of each soil type, how the layers interact, and finally, how deep is the total until the bedrock?

[@auntielaura5]

@@heyyy4783 Fascinating. Thanks for that.

[@MondoMiami]

Love your illustrations. Accompanied with your excellent commentary, they really make this easier for non-engineers to understand.

[@NJ-Cathie]

You do an amazing job on these videos. Anyone looking to go into civil engineering should watch these videos.

[@GeorgeMcNally]

I really enjoy your videos.......I'm not an engineer, but you make difficult issues easy to understand.

[@jonka1]

Your diagram of the curved forces under the piles looks a lot like a ball and socket joint in the way the clay is stressed. I'm thinking that as the building leans it's going to reach a point where it rotates around the compaction line like a shear plane and drops like a stone.

[@debl9957]

Always enjoy watching Josh's discussions. I don't work in the field but find it interesting and he clearly explains each topic.

[@anna-lisagirling7424]

I think, once again Josh, you nailed it. Your clarity always excites me as I learn so much from your videos.

[@kevinbarry71]

I love your explanations. And, unsurprisingly, developers of a luxury high rise were trying to get public money to help build it.

[@mt-nv4jd]

I think a few big wigs were protecting their bonuses.

[@mmatejka01]

Thank you again Josh... ! The way you break these down between the engineering and the politics is awesome...!

[@saidonfax]

Man, this is beyond awesome. Very easy to understand even for people without engineering / architecture knowledge. Thank you very much. It's kinda sad and frightenning that this still happens in modern days. We normal citizens usually have a lot of respect in and faith for engineers as we trust them with our lives. I'm so eager to see the final outcome of this.

[@michaelrexrode3759]

You are the ONLY engineer I have heard raise this issue. As a nonengineer your argument makes a lot of sense to me. It doesn't take a degree to recognize the disastrous placement of all those piles so close together!

[@blueboats7530]

Seeing that photo of the top ends of the friction piles, it's chilling how close they are. How many have the lower portions snuggling against each other, and that nullifies the friction effect by what, maybe 20% ?

[@user-sm3xq5ob5d]

The concept is to look at the piles as one piece. It doesn't matter how they are distributed over the foundation area. One that touches another on one side of its tip leaves more room on the opposite side. But all taken together need something to support their load. And that is to be calculated at the perimeter of the piling block. One could have as well cast the cap at the bottom where the piles touch the clay and go from there to calculate its bearing capacity.

[@garywheeler7039]

@@user-sm3xq5ob5d : and it still would have failed due to the clay.

[@user-sm3xq5ob5d]

@@garywheeler7039 Not to forget that the clay needs to go somewhere. It is not compressable.

[@phoneguy7589]

If I needed an Engineer I know who would be on the top of my list !!!

[@CosmicFox808]

Great video! You explain things so well, even a layperson like me can follow along. Thank you!!

[@thetowndrunk988]

I know very little about civil/structural engineering, but man this channel is awesome. You’ve really drawn me in since I found you a week ago

[@cayrick]

Thanks for this video Josh. You brought up many aspects that I never heard before. Notwithstanding your clear explanation, why would engineers not take into consideration that this is an earthquake zone which is subject to liquefaction. In my mind that would cinch the decision to go to bedrock. Mechanical not a structural eng.

[@BuildingIntegrity]

Thank you for watching!

[@randommcranderson5155]

You're not wrong - the tower is in a liquifaction hazard zone. But for the clay under this thing to go anywhere large chunks of san franscisco would fall into the sea anyways. Those are deep piles and if the clay around them liquifies, large chunks of san franscisco will disappear.

[@michaelsullivan3581]

Which is exactly what will happen eventually!

[@edmessina8392]

@@randommcranderson5155 so like throwing the baby out with the bathwater.

[@chuckuni5366]

@@randommcranderson5155 But if the clay is already yielding, does it really need to fully liquify to have an effect?

[@russellhltn1396]

Ok, so an engineer signed off on that. Does the permitting authority have any responsibility to double-check that? Why else do they exist?

[@francesconicoletti2547]

To make sure a credentialed engineer signed the document. Do you really want city officials redesigning private buildings ?

[@francismarion6400]

Permitting authorities have less responsibility than Pharma companies when things go wrong.

[@markrenton1093]

Great job on explaining the problem, you take a complex situation and break it down in the simplest of terms.

[@kramsdrawde8159]

WHEN THE CHEAP BECOMES EXPENSIVE !!! Another good explanation of this situation. Great job !!!

[@1d10talert]

when you put up the picture of the actual piles, it blew my mind. with your explanation, i easily understood why they were basically worthless as designed.

[@boowiebear]

$4M never looked like such a bargain for bedrock pilings.

[@doblove]

I'm not even an engineer or have any relationship with the that field, but I find this videos so interesting and educative. Very clear explanations. Nice channel.

[@chrishayhurst5549]

Can watch your videos all day brother , you do great work, super interesting...I'm running out of videos to watch on your channel haha , love it man , keep it up 👍

[@paulcoffey359]

Ah, Saturday lunchtime engineering. Today I'm having a ploughmans lunch with a side of mathematical reality.

[@GenoSalvati]

Didn't this start out as a steel building in early design phases? Were the foundation requirements reviewed when the decision was made to use concrete? Also, I can't wait to see your analysis of the Hamburger "solution" that has caused more sinking.

[@kevinireland8020]

the foundation and the building are two different things. and one is called the foundation and the other is called the building.

[@wbharris1031]

@@kevinireland8020 Keen observation there Kevin, but a concrete building is much heavier than a steel building.

[@MFcitrous]

Yes this was a major source of the problem afaik I remember they were talking about removing the top third of the building at one point.

[@youtbe999]

Well done! I learned a lot. It makes sense why this system is sinking and tilting.

[@jordansiqueido2101]

Hey brotha. Thanks so much for the in depth coverage. I'm a truck driver who came across local news story, watching TV in an SF hotel room, a few years ago. Been hooked on this thing ever since! In the middle of watching your four part. I'm picking up what you are putting down. Just hopefully not 9n the demo site.. Buy stock in Orville's pop-corn! Can't believe what is goin down, up there!

[@kineahora8736]

Hi Josh, this sounds like a basic error to consider a dense pile grouping as individual friction piles rather than a single group that will require more end-bearing functionality-in my business (medicine) we have something everyone has heard of called “malpractice”. Why isn’t this engineering malpractice?!

[@ReneSchickbauer]

That's for the judge to decide, after all facts have been laid bare. It might have just been a mistake in the calculations (i doubt it, but it's possible).

[@postie48]

I am not knocking Josh's video in any way - but it was a simplification of some pretty complex engineering stuff. Soil mechanics makes nuclear engineering look simple - well maybe!

[@francismarion6400]

Engineers have to carry liability insurance just like everyone else. His rates will be going up if they can prove it was his design error that caused the problem. Or he may be uninsurable after this.

[@patrickmorrissey2271]

Great job on this one.... I think you very delicately, did raise, the key issues here, that happened.... And basically, most parties involved, kind of painted themselves into a corner, with that gambit.... which now is, a disaster... We're just waiting for it to happen..... Also, I am greatly enjoying your videos on Instagram. I live right by you... I'm very intrigued, by how, I take a lot of photos, in the same area, but what catches my eye, is very different than what you get.... I am from somewhere else, so it's all new to me... So it's always interesting to me, what is out there, and what people photograph.... this is really a great area for photography....

[@BuildingIntegrity]

Thanks Patrick! Hoping to take a lot more architectural photos in the future and incorporate them into the channel as well.

[@WhittyPics]

John you explain this stuff better than anybody on KZbin

[@buttbirder253]

I've recently discovered your channel and have enjoyed your videos. From this retired teacher, I have to say that YOU are a great teacher!

[@BuildingIntegrity]

Wow! Thank you so much!

[@ShakespeareCafe]

the building is excessively heavy to rest solely on a 10 foot concrete slab and friction pylons. Just think of all the drywall in each unit and floors of travertine marble, granite countertops, all the owners' possessions not to mention the entire building is constructed of heavy concrete. Going down to bedrock was the only option and the only way to support a behemoth building.

[@elizabethgrogan8553]

Developers will often choose the cheapest option, because profit is their master. I don't believe they should have options. Long term safety needs to be the prime target in sinking piles. Having worked in Cape Town and Amsterdam, both of which have large areas of reclaimed land, there are strict rules governing subsoil building. In Amsterdam, concrete and steel piles are driven deep into the ground and are overseen by specialists from the local government.

[@martentrudeau6948]

I think the Dutch are the best engineers in a marine and wet environment, because the land in the Netherlands requires it.

[@gordonrichardson2972]

Yes, the Cape Town Foreshore is reclaimed land, just like SF Bay.

[@catocall7323]

SF has oversight too, it's just that they hire on the basis of political favor instead of merit.

[@LTVoyager]

Developers should choose the cheapest option. That is just good business. As the video says, the fault is with the engineers for proposing a option that carried very high risk and not making that apparent to the developers. In fact, they likely should not have proposed this foundation option to begin with. Every option provided to a developer should first and foremost be an option that “works” from the perspective of integrity and safety. The differences should be in other areas and the developer than then choose what things they are willing to give up to save money, but basic building integrity should never be on the block to be traded against cost.

[@martentrudeau6948]

@@LTVoyager ~ The foundation is the most important part of a building. "a wise man built his house upon a rock" And "a foolish man, built his house upon the sand." Matthew 7:24-27

[@peterwallace8441]

An interesting analysis. My thesis was on pile group analysis (1981). A closely spaced group like this will shed load from interior piles to the outer piles, and especially the corners. The highest loads will be at the corner piles and this will explain the excess settlement. This aspect of pile group behavior has been known for nearly a century! Any variation in the piles or clay layer will lead to differential settlement and hence the tilt. The additional piles to bedrock may just transfer the problem to another part of the pile mat.

[@toothlessseer3153]

Amazing videos (as always). Keep up the good work 👍👍

[@lagautmd]

I have a hard time believing the engineers tried to play poker with the transit authority by bluffing their inadequate design was good enough (so you, transit authority, can pay to make it better). My guess is the developer in an unverifiable conversation hatched a scheme with the engineering firm's boss to play poker with the transit authority. For the developer, it's win-win. But, for the engineer, it's a big risk. It seems likely that the transit authority's engineers looked at the newly designed tower pilings and recognized that they needed to go to bedrock in any case, and called the bluff.

[@kevin3434343434]

Which begs the question did someone CYA and get this down in writing.

[@andrewtaylor940]

I have a hard time believing it didn’t happen

[@odess4sd4d]

I have a hard time believing the engineering firm that did the Geotechnical design had any upside to play poker with. Normally they get paid by the hour to take on huge risks. They have E&O insurance they think will cover the potential loss but if something really goes wrong they will get sued out of existence. They give the owner a design. Owner: "can't you come up with something cheaper? Firm X could design something cheaper. I'll pay you by the hour to amend your report." Geotech: "OK, here, but I wouldn't recommend this option, it's risky" Owner: "Thanks, see you at the inspection."

[@sw7366]

Josh may live on the other side of the country, but he is putting his finger basically on the problem with San Francisco one Party politics and how things get done in San Francisco

[@francismarion6400]

Or the transit designers engineer was also in on it.

[@henryD9363]

This is an excellent and very informative description and explanation of what the heck is going on down there in the ground, unfortunately way above the bedrock. Most of the downward force is carried by the center piles. This reduces its ability to prevent the whole darn thing from tipping sideways once it starts. It's like balancing a heavy vertical column on a bowling ball -- in the sand! The upward force is very low along the perimeter. Just the opposite of what you need. Tippy, tippy, tippy! Amazing! Very important description and beautiful diagrams. I watch all your videos.

[@jimmousseau2765]

Another great video. Thanks. You’re looking exceptionally dapper tonight. 😂😂😂😂

[@vitaligent]

Love your channel. Keep up the good work.

[@BuildingIntegrity]

Thanks!

[@Nic7320]

But San Francisco always leans to the left...

[@Leopold3131]

This was an excellent explanation. I understand there was another competing proposal to fix the tower that focused on driving pilings down through the middle instead of the perimeter, and a third engineer said that’s the plan they should have gone with. And now your explanation tells us why.

[@townesblues8877]

Great videos Josh. Thank you. Very educational. One question you might consider addressing is if the slab is cupping, why the lean to one side?

[@funhavin5394]

I enjoy reliving Soils and Strengths classes watching these videos!

[@jimewing5097]

Great video as always. Next engineering task will be for the engineers / construction folks / owners to engineer a solution whereby the public pays for this.

[@tonyblaylock1309]

The four million dollar question is: will the building remain safe as its sinking and leaning ?

[@terry94131]

From what I've read, at 40 inches out of plumb, the drains back up and the elevators won't work. They are currently about 26 inches out of plumb. I think before it becomes unsafe, it will be uninhabitable.

[@tonyblaylock1309]

@@terry94131 26 is less than a 2:1 factor 🤯

[@francismarion6400]

Yes. If you are a gecko.

[@creepycrawlything]

Once again. Clarity of explanation and clarity in communication.

[@blackbear92201]

Another awesome video. thanks for posting! :D

[@chuckuni5366]

If the foundation mat is already dishing down in the center, with potentially unknown stresses/damage along it's bottom side, wouldn't adding outside piles for support only accelerate this dishing? And did the repair plan calculate the capacity of the mat to be supported at it's perimeter even though the original design was for relatively even support across the entire base? Even if it did calculate those stresses, I am sure those calculations get really fun in the event of an earthquake with one side more or less rigid to bedrock and the rest floating on sand/clay/etc.

[@adisario]

Developer tells engineer they need to come up with a way to sell this to TransBay Authority to get them to pay or they're fired. Fake plan is created. TBA says "nope". Developer moves forward with fake plan.

[@mattlauer3323]

love watching this channel always walk away like I learned something great explaination

[@jimarcher5255]

Excellent use of graphics to explain friction piles and their limitations.

[@Riogrande1964]

Based on your analysis, it seems likely that driving pilings to bedrock around the perimeter of the building is not only a failed solution, but may actually make the problem worse … and this seems to be happening…

[@davefoc]

I deleted my previous comment after I thought about your post some more. It seems like for the added peripheral piles to work the ten foot slab of concrete and steal will need to be able to transfer the load from the center of the building to the new piles . That seems plausible to me. A structure consisting of ten feet of concrete and steal seems like it might be strong enough to me (a non structural engineer.). It sounds like if that doesn't happened fixing this building this way is not going to work.

[@SteamCrane]

@@davefoc The 10' slab is already failing. Look at the shear wall photos in the previous video. The building is already past saving.

[@Riogrande1964]

To clarify my comment, I am suggesting that the slab dishing is consistent with reduced friction in the middle pilings, as opposed to the more rigid resistance around the perimeter. Driving new pilings to bedrock around the perimeter will only reinforce the asymmetric forces privileging the perimeter. At what point does a 10’ thick slab fail?

[@Riogrande1964]

@@SteamCrane thanks for grasping my point - I should have been more explicit

[@davefoc]

@@Riogrande1964 If this is directed at me I think I understood what you meant and I thought your were right (at least after I had thought about it for a while). It is an interesting mess. The "friction" piles are not providing the resistance anticipated so the load is partially being supported by the end of piles but the end of the piles are not baring as much load as seems to have been anticipated either. The mud around the building is slowly squishing out from under the mat of piles If the fix works the side without the extra piles is supposed to settle and that will theoretically allow more pressure to build up under the original piles which should help a bit and reduce the stress on the concrete pad. But if the mud just keeps squishing out on the side without the added piles eventually that side might subside too far and the load supported by the central piles will decrease.

[@zoktoberfest]

With respect to the Millennium Tower, could you address the worst case scenario, assuming the tilt can't be halted. What is the point of no return? When will the conversation shift from counteraction to collapse, preferably controlled ? How would this be accomplished in such a tightly constructed city? How much collateral damage could be expected and how might the demolition disturb the foundations of the surrounding buildings?

[@joedavenport2477]

It's been done before in NYC. Instead of imploding it they had to take it down floor be floor.

[@garywheeler7039]

@@joedavenport2477 If they take down 1/2 or 3/4 of the floors, the effect is minimal. Had to consider that once.

[@ReptilesGeniales]

This was very interesting thanks for sharing your knowledge.

[@night_owl365]

I would love to hear you talk about other projects in the past that had a flaw that was overlooked. It would be very interesting. I love how you explain things. Very easy to understand. Thank you. 👍