Small correction: The Engineers that designed the "Fix" were not the structural engineers for the original building design. I meant to refer to the engineers of the current "fix" as the "original fix engineers"... not the original building engineers. If you are an engineer and want to perform your own calculations, additional material strengths can be found in the video description. I have emailed the SF Department of Building Inspections and Supervisor Peskin re this concern. I will update you all when I know more.
Very good explanation. Did you happen to ask these guys if they've picked this stuff up during construction? The "bearing" plate would look mighty small when compared to the giant rod on site, even if it was ungrouted. Even a non-engineer looking at it would raise questions (the steel fabricator or the site foreman). Of course, small plate or big plate, the rest of this project is a complete shambles.
Thank goodness I am not a decision maker on this project. San Francisco needs a team of very smart experienced structural engineers who are 100% independent and well paid and supported.
What I know from academic research and scientific literature is that when one performs a 'peer review' of, for example, a research paper (or in this specific case a design proposal), one is tasked with the verification of the work in its _entirety._ You *do not* get to _cherrypick_ whichever parts of the work/proposal/design you do 'include' in your peer review and which parts you don't! What I mean with this is essentially as follows: when one is 'peer reviewing' a work they're essentially verifying, checking and recalculating every single part of that work to check whether or not that which is described in the work is feasible, logically sound, safe and valid from an engineering perspective in the first place (among many other things). And if they find this to be the case, and thus 'approve' of whatever it was that was proposed/established/put forth and/or claimed within the work, then the 'peer review' is complete and the peer review process is finished (unless there are multiple simultaneous peer reviews required). With the peer review process having been successfully completed, the name of whoever performed the review is forevermore connected to the work as (one of) the peer reviewing parties that approved the work. Their name and reputation (and liability, in this case) is now connected to the project, *with absolutely no CYA (covering your behind) whatsoever being allowed.* Either the project is safe and you approved it following your peer review, thus agreeing to accept any and all liability as a result, or it is unsafe, you don't approve the project as a result of your peer review and thus the project cannot continue until they fix whatever caused it to fail the review, or until they find another peer reviewer actually crazy enough to attach their name to the project and give it their blessing. But those are just my 2 cents, but I do know for a fact that the process I described above is how these kinds of projects are usually handled in Europe.
I am a retired consulting mechanical and electrical engineer, having worked with architects for 52 years in the design of commercial and municipal buildings. I have followed your TH-cam videos and found them very interesting and informative, especially the Surfeside project. Recently I "stumbled on" a short video showing the potential failure of an apartment building for college students in Manhattan, Kansas. After viewing the video I sent an email to the city engineer, suggesting she watch that video. The apartment building was apparently fully occupied at that time. In the email I suggested that the city engineer contact Building Integrity. I did not have any reply from the city engineer. Interesting, the next day or so I saw a news report that the Manhattan fire department had condemned the building. I have not followed up, nor have there been any communications. Thanks for your good work. PN
Wow, that's incredible. Good for you for taking the time out to report your thoughts. It's unfortunate that nobody got back to you. Irritating!!! You did good. Hope you have a wonderful weekend. 🌞
I have an engineering degree in an unrelated discipline. In addition to that plate (and the associated nuts), I'm also worried about the ability to transfer that much force to the existing building. The existing foundation was designed to have force distributed widely across the base. Putting that much force on the edge strikes me as a great way to run into weird loading regimes including torque, which concrete doesn't handle too well.
Yes that wedge is kind of small, especially as it would have been easy to water jet deeper under the existing slab, and then pour in a wider thicker raft to spread that load over a larger area. Not as well bonded to the structure, but with enough steel in it, and thick enough to make the slab triple the thickness in that area, it should be able to spread the point loading out a lot. Yes cast without a form, but use a high quality hydraulic concete and superplasticiser, and just keep pouring till full, with a minimum volume of concrete to ensure good cover, and you will have a much superior foundation, then can use the forms and do the rest in a few pours per section.
True...but how is the system gonna behave if the building starts to move in the event of an earthquake, the forces on the foundation will suddenly have unharmonic spikes....i hope i don´t have flaw in my thinking process..
I also don't understand why the key is angled the way that it is. It's trying to push up on the building, so the top edge of the wedge would be where the force is applied. I know it's tied in with rebar, but wouldn't the angle on the top of the wedge tend to want to push the vault outward away from the building as more load is applied? Would there have been some other limitation with flipping that key vertically?
I have no engineering degree, but my first thought was "That is a lot of load going through the threads of 4 nuts (at the top near the jack)". And each thread is like 5-6 mm deep? Is that really enough to hold up the building?
@@playgroundchooser Hey at least the building is mostly empty condos owned by the ultra wealthy, for tax write offs, who won't feel much of a financial impact. The neighboring community is what will be hit the hardest.
@@StaYUTI420 What are the odds that they hire the same engineer to design more high rises along the path of destruction of this one? The newly available property will surely be discounted
UberEats driver here, If the threaded rods are loaded beyond their yield strength, couldn’t you end up with a cascade failure, once one of them snaps, the load is transferred to the adjacent rod, which snaps, and so on. Kind of like the Francis Scott Key bridge, but underground.
@@RockHudrock nah - the steel has a plastic range after yield. If ya Google images of stress/strain of steel it’ll show you. There is a fracture point but this would require a much higher load to happen. By that stage the load will distribute through the other bars - but remember that the load is transferred to the pile - which will settle by an amount - so ideally the system should work together . This ignores all the other components linking the concrete box connected to the existing foundation.
Nope. Checkout torque to yield fasteners - you've probably got a bunch holding the cylinder head onto your engine. And think of the threaded rods being springs evenly distributing the load between each group of four. Conversely, if the rods were made of something really stiff (carbon fibre say) one might carry all the load, snap, then you have a cascading failure. In the bigger picture a 3" rod going through a 1/2" plate does seem out of proportion. In the image of the jacking beam at 32:36 it appears to be 1" to 1.5" on the top and bottom of the I section with a 1/2" washer as well and closely supported by the stiffeners. And what's happened in the last year since this video was posted? An update would be good...
This really sounds like a holdover from the 52-piling design where the plates probably would have been fine, but then they dropped 2/3rds of them and nobody really thought to check that particular part.
You might want to consider sending this to the Insurance company providing the liability insurance. They could put the breaks on this and force the A&E and Construction company to provide the calculations. Most Insurance companies have engineers on staff.
You even considered for a min why nothing is being done to shut this building down, because everyone but the homeowners are corrupted? The US Dept of Justice needs to come in here and shut this building down and order a complete evacuation, followed by a demolition of the entire building.
Josh I think that you have identified a valid issue. As a Professional Engineer with 45 years experience, I agree that, just from observation, the size and thickness of the plate at rhe bottom of the rods appears to undersized for the magnitude of the loads proposed. This area requires careful design where you report there does not appear to be any present.
The plates are even worse than they appear at first when you consider that the weakest sections are where the threaded rods penetrate the steel plates, and this is also precisely where the concrete is also weakest owning to the holes where the rods run through them being in the same location.
Where are the city engineers who are supposed to oversee this 'fix'? Didn't they even notice that there are no calculations for the steel plate that this whole apparatus is supposed to rest upon? It is shocking that considering how flawed the design and engineering of this building is that: A. They trusted the same engineer to come up with a solution and; B. A qualified structural engineer in an approval capacity did not raise any alarm over this omission in calculations.
I live in the SF Bay area and have followed the story of the building for a long time and also commented on previous videos Josh has done on the project. Again, I think he is right on target with his comments. There is a concept called “cold eyes” which many have heard of. It is very much like independent peer review. I work on machinery and spent my career sailing in the engine rooms of commercial oil tankers. Many times we would have a perplexing problem so I would ask some of my qualified shipmates(other engineers) to take a look at the problem. Many times they were able to help-a lot. In the case of the Millennium Tower, some cold eyes would be strongly suggested. Sometimes being “too close” to a project keeps you from seeing some details that are important. Heck, my wife is not an engineer, but she can look at some job or issue and mention something that’s important. Also, maybe some alpha male issues come into the picture; as in ‘Hey, we’re the big time engineers and don’t tell us anything. We know, okay?”. The City of San Francisco should consider his advice, soon. Thanks, Josh. Perfectly stated.
@@Hyperlooper I just did a rough napkin calculation, and the punching shear failure of the plate is a little over 1.7 million pounds for the four rods. So while the concrete will likely suffer localized bearing failure around the plate interface, and the steel may wind up a mangled mess, some sort of catastrophic failure where the rods rip away and lose all support from the concrete is highly unlikely.
This tower is the exact case-study of why doing things cheaper is rarely better. If they'd done it right the first time, this wouldn't have been an issue in the first place.
Yeah, but the ultra-rich might not get the huge returns they were promised. Have you ever hsd to tell a guy he might have to get by on a 250ft yacht, when he wants the 300 ft one? It's not pretty. Best to go the cheap route, and just hope it falls down after he makes enough money to get that yacht.
@@PowerScissor The difference here being the rich guy having something for himself and deal with the issues, and a building potentially falling and killing multiple people who had nothing to do with the rich guy's choices. These are barely even comparable! Dude wants a yatch bigger than they can afford? Fuck this client, but consider selling anyway. Dude wants to build a cheaper building? OH HELL NAH, FUCK THAT!
it sounds like they found an engineerimg form willing to cut corners. Then when fix time came and thry got hufe estimates that required shitting parts of the city down forl ong periods they called them back forcthe same reason
Your passion for safety is addictive. I have no background in structural engineering but I watch your videos because they are very detailed and informative. I hope your channel grows.
@@BuildingIntegrity The next step to to write up your concerns and send them by certified mail to the Fix Engineers, The Review Panel and to the Building Department (if you haven't already).
I was an engineer for my first year of university (then switched to Physics; go figure), and really enjoyed Statics and Dynamics (basically, the topic of this video). I also taught high school science for a little while. I read a lot of these comments, and didn't see anyone (sufficiently) praise the teaching technique. It was beautiful. I was sitting with the question "so what's at the bottom of those threaded rods?" for a couple of minutes, which made me really pay attention to what could have otherwise been very dry stuff. I'll have to remember this for when I (eventually) get back in to the classroom. Well done! The only downside is that now I have to go watch all your old videos. 🙂
I'm just a simple advertising exec and I wholly agree. I was able to comprehend a great deal of the importance of each piece of the 'fix' apparatus and their purpose(s) to the whole of the project. Thanks BI!
I am not an engineer, but was a PM who got to see the 4" steel base plates for the Oviatt Library lobby columns sheared right through due to the Northridge Earthquake. Engineers put a lot of faith in steel & the earth doesn't was my takeaway
I am a UK Chartered Engineer (similar to a USA Professional Engineer). On watching your review of the drawing, I have to agree the bar/plate connection looks worryingly small. From your discussion of the calculation sheet, I understand that the bars are sleeved/greased mainly to simplify the design for "fuse" action of these bars (wherein the designer calculates a required "free length" of 160in). The bars could have been designed with a more conventional anchorage into the vault concrete (that is, a connection that can transfer load more gradually, over a longer length of bar), but then "fuse" design would become more complex as the composite behaviour of the bar and the concrete would need to be considered. By sleeving/greasing the bars, the calculation of free length for "fuse" action is greatly simplified, but by inspection all the load now has to go from the bar to the vault via the plate, just as you have explained. I am also concerned by the unchecked assumption that the jack load will be evenly distributed into all 4 bars. If there are any geometrical imperfections, some bars will take more load than others, which is very concerning since the bars are intended to yield at some point. I agree that if the bar/plate connection fails, the vaults and piles are rendered entirely useless. There would also be a sudden change in support to the Millenium Tower itself.
I don't like the idea of the tension "fuses" at all. Because of the motion and distance time scale, the dynamic load or total load on the building wouldn't be reduced. The seismic event that would stretch the rods would lift grade and effectively leave the building subgrade. Ins't that what they're trying to prevent? Like you said, additional structure anchoring the rods to the vaults would increase their effective stiffness. I don't like the idea of reducing the diameter of the rods to decrease their stiffness and make them effective "fuses" again. Bottom line is there absolutely needs to be a very detailed local stress analysis of those vault anchor plates.
I am also worried about unequal distribution of load to the 4 rods, that was the first thing that caught my attention. Then the rather smallish steel plate to transfer the load and I, too, am concerned about this design.
relative to the size of this building, these plates are like stiletto-heels? 😮 I feel like these plates ought to be footers that flare-out, like the bottom of the Eiffel Tower. 😢 I’m not an Engineer … but obviously we want to spread the load OUT, not concentrate it. 🤦♀️
I'm no engineer, but I would expect the bottom plates to be about the same size as the jacking plate. They are taking approximately the same load. Is my intuition wrong?
@@bbgun061 Various components in the system will have significantly more load carrying capacity than the amount of load carried by the system, so it is okay for the bottom plates to have less capacity than these other components. However, it is not okay for the bottom plates to have less load carrying capacity than the amount of load that they are carrying.
As mechanical engineer I would double check also the "tension fuse" calculation. I'm European, so the ASTM F1554 is not too familiar to me with all of their intricacies, not to talk about the units :) But what is perplexing to me, is the lack of taking into account the notch effect in the tension fuses. Those things, to my understanding, are all through threaded rods. The thread has a significant impact on the tension strength of the rod. There is going to also be wind affecting the building, which will cause the building to sway and that will cause the amount of tension in the fuse to alter. The thread with it's sharp crests and valleys will also act as a perfect swarm of nucleation points for cracks under fatigue load. I'd love to see how this is going to play out, but without the people inside or near the building... Do some of those ASTM or AISC things take these into account? Also your worry about the steel plate is valid, worth some triple checking.
I think for this case they would assume the minor diameter of the threaded rod for the actual calculations, however for the stress concentrations, I think there are some equations that you can kind of just take that into effect but just multiplying everything by 0.8, though I'm not too sure this is going to be much of a cyclical loading kind of thing, mainly how it's going to be under tension constantly, the only actual dynamics being that of an earthquake
Seismic and wind forces would have been applied to the building model when determining the reactions the piles need to resist. In reality the loads these piles will sustain long term would be much smaller than the loads the rods have been designed for. The danger is when SF has another major earthquake which it will eventually...
@@AlexJoneses This is correct, the inside diameter of the treads is used to calculate its area and any factors accounting for stress concentrations of the threads ect are accounted for in the yield and ultimate stresses of the materials which are part of the ASTM F1554 standard, which helps to simplify and streamline design. The ASTM standard outlines manufacturing tolerances, how smooth/consistent the threading needs to be, and then verified testing ensures that you get what you pay for so to speak. It will also have information on metal fatigue. Gr 55 rods are actually quite ductile and resistant to metal fatigue.
As a geotechnical engineer that has observed much smaller anchors with a similar design fail while testing them, I am very concerned. If that plate fails the rods could become rod shaped missles which shoot out of their holes through the overlying vault roof. Your analysis needs a response from the design engineers and city building department.
My concern is that as the plates yield, the reduction in force on the jacks will be interpreted as a positive sign that the building is no longer sinking, instead of the reality that they have experienced plastic deformation and are close to failure.
@@Hyperlooper Unlikely. Because when that happens all the plates will fail in a cascade, and the building will begin actually settling (and will be measured elsewhere). It will be obvious anyway, since a lot of really loud bangs will be heard.
@@armamentarmedarm1699 When an element is critical, but inexpensive to upscale, the best design methodology is to overbuild that element to eliminate risk. The cost of quadrupling the thickness of the plate (just stacking four of them even) is essentially nothing in the grand scheme of things.
@@fhuber7507 The steel plates are also highly likely to fail/break at the rod holes, because there is not enough supporting material around these holes. And when this happens (... to me this is just a question of 'when', not 'if' ...), there is no means of checking the state of these plates and/or the state of the rod ends, because they are firmly enclosed in concrete. From my point of view it would have absolutely been imperative to design this crucial point of potential failure in a way that would have allowed constant monitoring at any given point in time, especially with regards to the incalculable additional stress factors from seismic events in an area that is very vulnerable to earthquakes. Also, there seems to be no provision for re-greasing the piles and the rods in their respective surrounding tubes, which I would consider a serious oversight with regards to the necessity to keep these mechanisms in an uninterupted perfect working state for decades to come - especially with regards to the fact that they are situated in enclosed underground vaults which are prone to high humidity and condensation issues. Overall I think it would have been better/safer to have the piles and hydraulic lifts designed as pushing elements that work directly towards the (accordingly reinforced) ceilings of these vaults instead of using them as pulling elements working towards the floor sections of the vaults. By doing this the whole failure prone I-beam/rod/plate parts could have been eliminated.
I’m betting the plate in question might have worked with the original count of jacks they were putting in, then someone made the decision to reduce the count and they never re-visited the design of that small plate to compensate for increased loads.
How much will it cost to begin disassembling the building, from the top to bottom, and remove the entire thing from the city? Because... I think they will ultimately regret not doing this.
It's gotta be 10s of millions if they aren't allowed to use explosives and just bring it down in one go. The company who built it will prob just declare bankruptcy and peace out, forcing the city to pay for it's demo.
Had this been caught early enough it would have been cheaper to start over... Honestly it's looking like the fix may cost more than starting over given the risks of it failing
An absolute shitload. Especially when you include the potential losses of not being able to keep the building open, and loss in potential revenue. When you look at inflation that has taken place since the start of this building, it would likely cost more than the entire cost of the building, plus the cost of this 100+ million dollar fix. There is no way in hell they are going to remove this building, they will let SF crash and burn prior to ever removing this building. Most of these condos are 1-15 million a piece, and there is 419 condos in the building, at an average of 2-3 million each, that is like 840 million to 1.25 billion in real estate in that building, ignoring the rest of the building itself.
I started studying for my engineering degree in 1981. That connection reminds me of the Kansas City Hyatt walkway connection that failed that year. Also, I've discovered over the years that proportions can give a good indication of a potential problem. In this case I see a massive pile, massive reinforced steel beam, massive anchor bolts, and a little tiny plate. Right there I would have asked questions. Final comment, as an engineer we are to try to find economies in our designs. All the components in that cross section, the Pile, the beam, the excavation, the concrete etc. The least expensive item in the whole assembly that stupid steel plate!! I would have sized a simple plate large enough to distribute the load to the concrete and with adequate thickness to resist all the shear loads. Then I would have added stiffener plates and plate washer, and it still would be the least costly component in the design. Then I would go home and had a good night sleep.
The Hyatt Regency walkway collapse immediately sprung to mind for me as well! This is not my field, but I have seen a fair bit on it as a case study/cautionary tale for engineers of all kinds. It's a great example because it was both a quite subtle issue, yet easy to explain to anyone. This case though, does not seem subtle at all. It worries me that this was overlooked so easily. As a software engineer my immediate instinct is to look at all the interfaces between components and ask "What can go wrong at this point? What have we done to satisfy ourselves that this is OK?" I couldn't tell you if the plate is properly sized, but I would like to think if I was reviewing this, I'd at least be asking the question. Here you have a chain of components that are transferring a force, and nobody did a checklist to make sure they'd thought about all of them and all the connections in between?
I’ve got the feeling that some Engineer got enamoured by tensegrity and decided to design it into a critical component without understanding the failure modes of tensegrity systems. Like you push it sideways and it fails!!
Seems to me (a non-engineer) that using cables of the sort used for post-tensioning concrete would have been a better choice. Run them in a big loop inside conduit with the end points at least several feet apart. Run three or parallel in each section allowing redundancy. No buried connections, known technology, and if cable deteriorates it can be extracted and replaced with the load temporarily transferred to the redundant cables.
So far, the building has tilted about 30 inches. (Another 6 inches, the plumbing and elevators will stop working). _These are Hail Mary moves to delay that day by a few years (so that the chief engineer & city officials are retired when this happens)._
Well, to be fair when they set up the jacks, the intention is that as the building continues to settle, it will settle the other way instead, helping to level it back out. Not gonna work with the issues with this design though.
The building in danger is analogous to the local government of San Francisco which is also tilting dramatically to the left and will fail/fall completely due to not reaching solid bedrock (values) There is a tower of babble component to this story.
This situation reminds me of the Hyatt Regency walkway collapse and lack of attention on critical connections. I appreciate your approach to this and how you can make an electrical engineer understand structural engineering concepts. As opposed to most engineering designs (cars, airplanes, computers, etc.) buildings need to withstand years of minimal attention and stay within their design parameters.
I'm thinking of the concrete truss pedestrian bridge in Florida. 'Concrete' and 'truss' are words that you don't hear in conjunction very often. Similar scenario. Tensioned rods with adjusting nuts anchored in concrete. The concrete failed where the rods imparted force to the concrete.
Right on , in the St. Louis walkway collapse where the nuts pulled through holes in the beams . 200 plus people would be alive ,if they had just put big thick washers under the nuts.
The Hyatt Regency bridge collapsed because the support rod connection was changed in the shop drawing phase. The original engineering was not great, but the decision to split the rod was fatal.
In this disaster, the new design that made it easier to build, doubled the load on a set of nuts and the nuts failed at this new load plus a walkway full of people.
The original foundation was insufficient to handle the load. Remediation has proven to be insufficient as well. It’s time to admit failure and do a tear down before we lose lives.
You haven’t been paying attention. The latest report I have seen (SF Chronicle 22 June 2023) states that the progress of the leaning has been arrested. There are no lives in imminent danger.
I don't believe there are lives in jeopardy, per se (ie. a failure of this fix would lead to catasrophic loss of life), but I do wonder if it's even worth fixing at this point. We can't even be sure this "fix" is going to work, and even if it does, would anyone actually want to live there anyhow? I mean, this place now has a bad repuation. Surely the value of each unit has been greatly diminished. Is it really worth it?
@@jasonhaynes2952 The fix has worked, so far. The objective was to arrest the leaning, and that has been done. The owners have been compensated for dimished value of their property, as I understand it.
The current lean ratio is 30" to 600 ft. This is 1:240. As long as the structure is design for gravity notional loads (which it should be per codes) this is well within tolerance for the structure to handle. Throw in a seismic event...that would be a good one to check in the model (which I am sure they have!).
I think it's worth repeating that this huge problem could have been avoided had 5 million dollars more been spent on going down to bedrock during the ground work . Now half billion usd is a bandage solution . Will there be a lesson learned ? ❤ this channel
I've completed a few pull out tests on piles and grouted anchors over the years. I've seen 40mm (1 3/4 inch) steel bar fail in tension at 70% (~900kN) of its "ultimate" load (~ 1250 kN). Very similar loads to the bars in this design. I've also seen the nut on a 40mm bar pull through a 25mm (1 inch) plate at similar loads. When you are dealing with loads this extreme, things deform in ways you don't expect and sometimes attract additional loads greater than design. I would also question the concrete's ability to take the load as well as the plate. When steel fails at these loads, it's like a bomb going off!
One question well two! ........Can the threads on the bars or the pairs of nuts take the strain with out shearing off. Why is the load transfer system - rods to tiny steel plate just a big penny washer, ? Never mind the small steel plate. Think about the 8 nuts!!!!!!!
That plate is about the size of a cross beam connector on farm machinery here in Iowa. Like they hold the front and rear gangs of a large disc together. Sure wouldn't want them holding up a skyscraper in an earthquake prone area.
Sometimes I think that the basic design calculations made for large buildings like this should be available at a local court or something. Wasn’t there a building in NY that had bolts instead of welds, but after a visit from some engineering students they figured out that the bolts could snap and had to be replaced with welds?
The problem with the building in New York, was that it met code to the letter. An engineering student asked the question about what would happen with a diagonal wind. The engineer, rather than blow them off, actually look to see what, in their calculations confuse them. He then determined they were right the building wouldn’t survive in a hurricane without additional diagonal bracing. The building code is a minimum. Not a goal.
I agree 100% with your assessment, the bolt anchorage will fail long before the bolt fails. In any case to design a critical element that is suppose to stabilise a massive building to be stressed beyond its yield strength is absurd and must certainly fall outside design code requirements. These bolts are designed to fail if the load is too high defeating the whole purpose of the repair work. This is a disaster in the making. (Retired structural engineer)
I don't get why the threaded rods on the sides need to be sleeved and greased. it should be stuck and moving with the vault. the only thing that should slide is the vault and the pile.
@@ericlala They need to be greased because, as the previous comment mentioned, they are designed to go beyond their yield strength. The system is RELYING on them to extend a little (without snapping!). And in order to extend without breaking the concrete, they must not be attached to the concrete.
I was just in San Fran on vacation, and our tour operator was talking about this whole cluster F. You can visually see the tower leaning compared to the neighboring buildings at certain angles.
@@BuildingIntegrity Yes, our tour guide told us about that. He stated he had a friend that lived in the building and demonstrated that to him. It freaked him out. Being from Miami and our recent history here with Champlain Towers, it's concerning on what's going on here. Many are claiming a huge under the table money payout to building dept personnel in San Fran, as originally the building was supposed to have piles down to the bedrock.
My gut reaction (not a structural engineer) is: (1) if the plate thickness is similar to the thickness of the top of the I-beam, then if the I-beam can resist pull-through, so can the plate; (2) However, the plate does not have the rigidity of the buttressed I-beam, and it has only a small width margin around the through hole, so it will deflect. That deflection would prevent it distributing load laterally very far, including to the transverse rebar above it, so it will be more like applying a 300 kips load to the concrete over a very small area around the rod. I don't know if that has implications for inducing fracturing of the concrete over the building lifetime. (3) If one imagines that the load starts pulling the plate around the threaded rod up through the concrete, it would then put the plate in tension, supporting the transverse rebar in a cradle. That's not what you want, but perhaps one might argue it as a fallback. (4) In that fallback, how strong is that plate in tension at the widest part of the hole? That depends on the cross section area at that point, the widest part of the hole, and depending on the hole size that looks to be _less_ than the cross section of the threaded rod, the threaded rod is at 102% of yield stress, and there's a mechanical disadvantage for the tension member in a cradle. (6) It intuitively seems that this is the one place one might add a bit more meat, given that it is inaccessible/unobservable and presumably fairly cheap in the scheme of things. At least exceeding the cross section area of the the threaded rod by a comfortable margin would seem to have at least a superficial logic to a layman. But maybe they just sized it so that it could be cut off the I beam?
This video has been haunting my thoughts. Today while eating lunch, I couldn't help but think this has some spooky similarities to the Hyatt Regency walkway collapse of 1981. Insurmountable stress on threaded rods, nuts, and a steel surface far too weak for the task.
It was the first thing that came to mind and I'm just an armchair engineer bicycle mechanic and I can tell you that fix is not going to work and I hate to think what will happen it is even a minor earth tremor let alone something around the 4 to 6 scale
Yes, Hyatt Regency all over again. Only difference is these rods will push, in Hyatt the pulled through. The stresses are similar. Excellent comparison.
@@andyallen7509 the threaded rods are under a tensile load, pulling the little plates at the bottom upwards. So it's identical to the Hyatt Regency situation.
I find your videos are so transparent that this complex subject becomes so clear they make the subject an exciting discovery, not some dry treatise that doubles up as a sleeping tablet. Thank you for your work.
I’m not a numbers person at all, but I’m fascinated by the psychology/group dynamics that lead to really bad decision making. I love your channel because you explain the technical side in a way that even I can understand, and you also provide some insight into why a situation may have happened. (Too much focus on cost-cutting, assuming that someone else has done the calculations, etc.) Understanding *how* intelligent, qualified people, when put together in a group, can overlook something that seems obvious is intriguing.
Cost is a huge factor. I'm not sure about San Francisco regs, but here in NYC, you can't demo buildings of this magnitude easily. So say you go through the catastrophic process of writing it all off. Now you essentially have to erect a giant shroud around the whole thing and then work from the top down breaking it down. There is a breathtaking amount of resistance to doing something like this, for obvious reasons. The last time this happened in the US was with the Bankers Trust ( Deutsche Bank ) building right next to the world trade center. It took them several years to fully deconstruct it. You can bet, due to sunk cost, that they want to avoid having to do this by any means necessary.
Govt spends more money than they take in - effectively counterfeitting money. They take that counterfeit and reward people based off of narratives, instead of performance. Then those inept people who get all the money develop big ego's and think they're the smartest people in the world. Before you know it, incompetent people are managing multimillion dollar building projects and buildings are collapsing
As a non engineer, if I can see immediately there are problems with the planned fix, then there is a very difficult road ahead for the building, engineers & the city. Good luck. Your explanation is, as always, clear & very well illustrated. Thank you.
If I lived or worked in SF, I would make a map of the area about this building, determine the height, and draw a circle twice the height of the building (to take account for any domino effect). If I felt a significant earthquake, I would make sure I was outside that circle. Because we all know what is going to happen.
I do live and work in SF - my office is about 2000 feet from the 645-feet-hight Tower - and I have to ask: how do you expect I could “make sure” I was out of range? South of Market SF is not the easiest place to maneuver, even absent a significant earthquake...
I am seeing this video for the first time since it was posted about 3 months ago I am NOT an engineer of aney kind but it's blatantly and egregiously obvious to my high school education and common sense that this is an excellent example of what we now know as STOCKTON RUSH SYNDROME
@xyz.ijk. I'm talking about the son who was wearing the suicide vest who wanted to blow up the Titanic, but before they were above the Titanic where he was going to detonate it, he was discovered. A fight ensued and the vest went off from a pressure sensor being kicked or punched.
I am a retired electrical engineer, PE; who practiced for over for almost 50 years and I love your channel. It seems like an analysis of that plate would be integral to the functioning of that scheme. I would love to have those engineers explain to me why they chose not to do any analysis of it.
@@donaldbiden1920 what is the absolutely have no calculations on those plates if they had done them, we would’ve included them in the design information
I am a retired Chemical Engineer after 45 years so I only have a fundamental understanding of your presentation. I have been following work on the Millennium Tower for several years and finally I am happy to have found your work and found it to be an excellent report. I will continue to follow you on future videos. Thanks.
I admittedly don’t deal with buildings, nor have I done any calculations on this, but I am a naval architect and ships involve some truly mind-boggling loads. 1 1/2” plate is about what you’d expect to find as the flange thickness for the foundation for a big diesel, and just based on my eye, a connection where something like a bolt is loading a plate like that with 125 tons, I’d expect a lot more backup structure around those holes, with a lot more material on either side. I wouldn’t expect only 1 1/2 on either side of the bolt with no backup structure on something that important.
Just as an interested “ spectator “ I would think that those “ all thread “ bolts and washer and nuts should be about 12 inch diameter sizes , given the loading they are dealing with. Simpler plan is to “ prune “ the building down to 10 stories.
Perhaps they intend to use a big-assed fender washer, a lock washer, and "Blue" thread locker on the nuts at the connection point to the metal plates. You can't argue the extensive safety factor of the blue over the red.
@@frankagent7472 They will not be needed as they have put lock nuts on one end of the threaded bar. If they wanted to silence the doubters they should have put 3 or 4 locknuts on each end of the threaded bar.
I'd expect "overkill is almost enough" for the plate preventing pulling the rod out of the concrete. Something on the order of a manhole cover near the bottom of the concrete.
So, when I need to make a minor change to my two storey house I have to follow archaic codes and get approval from oppressive city officials to make sure its "safe"... yet this skyscraper's iffy foundation design was approved as-is? Ok. I understand now.
Get buildin'! Only, we'll call it like 8, more floors to add on to your existing bungalow to be able to call it a skyscraper and do whatever you want! ... Ok maybe you'll have to tell em your skyscraper is just a baby and will be much much bigger by the time its full grown. If they start nodding and saying "oohhhh" you *know* you're in business. Suckerrrrrsssss...
The phrasing of this comment could imply you're advocating for demolishing the entire city from the top down rather than just the building. Edit: Can all the angry boomers seriously asking for the city to be bulldozed kindly get the 🦆 out of my mentions, thank you ✨
I figure at minimum the top half of the building would need to be dismantled / taken down to semi-safely accomplish any significant repair. But that's just my opinion.
I've been slowly completing my civil engineering degree as an older student and videos like this really help me appreciate and put into context the importance of understanding not just what the problem/solution is but why a solution will or won't work and how that plays out in the real world. Thanks.
Here is another good one. My father was the photographer on the Fred Hartman bridge that was built to replace the Baytown tunnel, in Baytown, TX. The Bridge was built with epoxy coated rebar (yellowish green coating). For years he had a piece of the rebar that had been cut and engraved with a diagram of the bridge (it was given to all the contractors). I never did find it after he passed away, but I remember it. I think we all know what happens to epoxy coated rebar, the corrosion from pinholes in the coating is far worse than with the same uncoated rebar.
Should have gone with hit dipped galvanised there, at least that will provide a protection to the steel, and then you can epoxy coat it for improved resistance.
But is this really the end of the world if this building is collapsing? I'm pretty sure when things like that are happening, there is even more revenues that's end up being generated by all the news agencies, TV channels, TH-cam videos, etc... than the original value of the building itself. Not to mention that every time something like that is happening, the people are getting close together and it turns into something very heartwarming. And there is also all the knowledge that we can get from the investigations for the future building constructions, etc...
Because the vault only being connected on one side to the building, the rods closer to the building will experience a higher load. The whole thing will try to rotate towards the building due to non symmetrical loading.
That's what I was looking at. The typical placement of the rods is in direct alignment under the wall. Only compression forces pushing downward on the existing pylons. These compartments are side mounted to the basement. Concrete is very weak in tension loading even with rebar. The weight of the building is going to apply a moment force to the thin wall of the building foundation and crack the entire length of the side at the top line of the basement. The better option is to replace a set of existing pylons with this setup. The load needs to be directly over the pylons, not cantilevered off the side.
I thought the whole point of the side pylons was to simply slow the settlement on the faster side. This is why the rods are designed to yield right? So they do not actually hold up the building only on one side? Once the settlement rate is slowed the rest of the building will not experience any shearing since it will be more or less evenly supported. The only shear forces will be the uptake of that extra load, which should only be a small fraction of the total weight. Or am I misunderstanding how this fix is supposed to work?
@@lucusloc The building load is, currently, straight down at the wall. Suppose the wall is an 8foot long 1foot tall 3/4inch thick plywood. All interior forces are pressing down on the upper edge of this wood. If you take a dead blow hammer and tap irregularly along the edge, this will drive the 3/4inch thick wood into the ground like a knife. Live loading is like this, and the edge will descend vertically, yet evenly end to end, which is the situation as it exists today. However, in this building, one end is digging in faster. Next, attach a two chunks of 2x4 along one side at 2 different locations. Now tap with the hammer again. Notice that the board will tend to warp. That warp cannot be avoided because of uneven forces caused by rotational forces at the attachment points of each 2x4 block. No matter how lightly you tap, the board will warp as the edge buries itself deeper into the ground. Wood can take this kind of uneven force. Concrete fails under this type of loading, hence the cracks in driveways and sidewalks as the concrete settles. The basement wall of this building will crack under the warpage caused by those side loading pylon boxes (2x4s). It will crack along a horizontal line drawn between the top of the 2 pylon boxes. That is why pylons under skyscrapers have to be directly under the load, that makes them part of the compression loading. The fix pulls the support off to the side of the wall, putting tension on the inside wall of the basement at the top of the pylon boxes. This is bad.
24 year homeowner in SF. I have nothing but contempt and disdain for San Francisco Building Dept and Planning Dept over a dozen first hand interactions. I wish them the worst
You live in San Francisco. What exactly did you expect? People who willingly stay in California deserve absolutely everything crappy that happens to them...
@sfojimbo5889 Well, I don't live in Texas, so I'm not sure what you are talking about. Idiot... Liberals should stay in liberal cities and states. The sane majority of America doesn't want them around...
30:00 really sums up the video. The fact that the team (the firm, maybe not the exact people) who got it wrong in the first place.. have been entirely left to their own devices to re-do the whole fix and then be BLINDLY trusted that "Yep, this time they will get it right, for sure!". Blows my mind! Well explained as always and I hope this video, as you say, reaches the right levels somewhere to get those calculations done independently!
I should not be left to my own devices They come with prices and vices I end up in crisis. -Taylor Swift, 2022 (Anti Hero) Also, should be these engineers
@@qwerty112311 I would swallow my pride, I would choke on the rines But the lack there of would leave me empty inside. Eve6 - Heart in a blender It's like Nietzche said...some people lose their last ounce of value when they cast away the bonds that kept them in check. If someone has no values, no moral compass, no restrain at all *within themselves* ... then they can only design, build and do harmful things. Respectfully 👍✌️🎩
You are so good at explaining all this highly technical stuff to lay people like myself. I feel so good that I actually understand what you are talking about. I hope your channel grows and you have more time to do more of these videos .
Thank you. Time is my biggest constraint. I am running a full time engineering firm, raising a family, and building our dream house right now; so these videos have been VERY difficult to get out. Things should smooth out in the future though. I appreciate your comment.
@@BuildingIntegrity As a non-engineer (medical background ) I find each of your videos entirely clear and fascinating - the wait till your next is well worth it every time. (maybe show us your house when its done too?)
The force exerted on the side of the original foundation is the biggest issue I see here. It’s going to snap and when it does all the energy saved up over any length of time will release instantly.
This is why they designed the rods to yield. It limits the load transferred between the vault and foundation wall, so that the foundation wall doesn't get over loaded.
Literally EVERYTHING about this building has been "Oh no! It's doing something unexpected! But we totally got it this time!" like 7 times in a row now. That building is coming down one way or another. The only choice is whether it falls down or we bring it down. Some one has to decide to just cut their losses and write it off at this point.
I sincerely hope it can be dismantled and rebuilt elsewhere, where the ground is sturdier. It sounds like the overall design is okay - just not great, and certainly not for this location.
I've been looking for a comment along these lines. Sometimes mistakes are made and there's no getting around them. That's what this situation strikes me as. It's probable that there isn't an engineering fix here. Sometimes admitting defeat isn't bad. Time to put the building out of its misery (before it puts lots of someones out of their's.)
M.D., your statement is definitely right. Now the real life problem is: who is going to pay ($$$$) for it? Accusations will fly, lawyers will be marching in. "Ouch!! What is hurting there inside my wallet?"...
I am not an engineer but just viewing this video reminds me of the old adage. “There is never enough time to do it right, but there is always enough time to do it over.” ~John W. Bergman.
When I saw that they built this monstrous building on sand-supported pilings, I just shook my head. When they built my house, they did this same "engineering" - and guess what? I paid big bucks to do perimiter pilings to jack the joint back up. And - yes, we have foundation dishing. Go figure...
That's because it is your house. I will bet that none of the engineers, architects, developers, etc. own anything in the Millennium tower. Their only ownership is the extra proceeds from cutting corners.
Nice video. As a project manager and former structural engineer in the construction industry I found it very interesting. This kind of anchoring in concrete structures needs thorough consideration and I found it hard to believe that the responsible people did not take this detail into account. Apart from the anchor plate also the transfer of forces from the plate into the concrete and from the anchoring sideways to the existing foundation is an important detail. What I also miss but perhaps you deliberately kept it out of the video is the fact that the extra support is only placed on the outside of the foundation slab of the building while the existing piles are distributed over the entire slab. The newly placed piles will alter the distribution of forces acting on the slab. Just a thought. It's also interesting that the whole proces of development and construction is being highlighted. Very recognizable!
Hi, thanks again for a brilliant post. Back in Sept '74 Ted Heath's yacht Morning Cloud sank off Brighton, UK, with a fatality. The wreck was eventually recovered by Bellsize Boatyard. The bow was mounted onto a sheet of marine ply and presented to public gaze at the front of the yard. The yacht was of composite build, wooden hull - 6mm stainless plate chassis to which the ballast keel was bolted. The holes through which the keel bolts were fixed looked like bullet holes, they had simply pulled through. Not backed up with large washers. Sounds too simple, doesn't it. Now I come to your point about the inadequate size of the new support beams/bars in the Millennium Tower. You can calculate all the stresses and strains that take place in a more or less static building but impact loading is another factor which comes from the seat of the pants. In the case of the yacht it is wave action that has to be dealt with. In the case of the Tower it's seismic activity. In the case of the jacks and bolts, calculate the sizes THEN DOUBLE IT. My only comment is that you are too quiet for too long. I look forward to your posts. Regards Pete on the Isle of Wight. (Retired engineer)
Yeah a little alarmed at that. We use 1 1/2" plate at my work but we put no where near those level of loads on it. This really feels like a part that should have been wildly over engineered and instead we seem to have something that is maybe just barely good enough at best to do the job. I would suggest contacting the local news outlets in SF. Unless someone happens to have an in with the building department the only way to get this reviewed is to publicly humiliate them.
@ Building Integrity Yes, you are right of course. 1 The plates between the pairs of greased/sleeved 'all-thread' rods should not be mere plates. They should be I-beams more like the one spanning the jack; strong enough to resist pull through, shear, bending and big enough that the concrete crushing strength is not exceeded. 2 SFO Building Control should do more than look at the Engineer's calcs and say they have reviewed them. 3 Clearly, SFO BC and the Engineer of Record have completely overlooked this element in the load path. However, I question the whole concept of 18 small piles on one corner The last significant piles that I designed were bored between the escalator tunnel and running tunnels of the Victoria Line. It was only a 15 storey building and the piles were a lot bigger than what you show. 30MN IIRC so nearly 7million pounds force in your money. The calcs shown are neat but cursory for such a significant building. In the UK any SE consultancy would carry out computer modelling to show the stress levels in the plate and in the concrete. It would be red so it would then be resized and recalculated until it was right. They would analyse the raft and how this altered the stresses in the raft. Even if the plates are redesigned will these 18 piles have enough resistance to carry the building? I think not. Your diagram showing a piled raft with perhaps hundreds of shallow piles suggests: either the piles themselves are poor quality and creep compressing under the load more than the others or the ground at depth is simply overstressed (if not block failure, block compression) - as the ground has compressed under load X it will continue to compress under 9/10th the load at 90% of current rate ( if the 18 even take 1/10th) If 18 piles at the perimeter generate enough resistance and the redesigned plates hold and beefed up reinforcement in the concrete holds, then they will likely overstress the pile cap. The pile cap was likely designed on local shear; not to span from that corner to half-way across the building. So, has the Engineer of Record re-analysed the pile cap and proven its capacity? Hmm!
I am an aeronautical engineer and have no much familiarity with building standards - but: The effective bearing area of the steel plate is 6.5"x12"x1.1 -2x3.141*3^2/4 = 71.6in2 Compressive strength of concrete is anywhere between 4,000 and 10,000 psi - so even with the lowest value the concrete covering the plate can take 286,000 lbf, and probably quite a bit more. Cross-section of the plate is 6.5"x1.5" =9.75in2. Shear strength of grade 55 steel (assuming that the plate is grade 55) is about 50-55 ksi. So, the plate can take about 487,000 lbf in shear (from one rod). Can the lower nuts be pulled through the plate ? Without getting into the nut dimensions - a circular shear section area 3" in diameter through the thickness (around the bolt) is about 3.141x3x1.5 = 14.1in2 (more than the cross-section area of the plate based on 6.5" width). So - pulling the nuts through the plate would require about 705,000 lbf. So - I do not think that shear is a problem here. Having said that - the design operates above yield stress. Any rod which exceeds its yield stress will start shedding the load between the remaining 3 rods - which in effect will equalize the load and share it equally between all 4 rods. This is good and makes sense - but leaves no room for any safety factor -which practically does not exist. Even in aircraft design a minimum safety factor of 1.5 is required...I In short - the design makes sense, but if something goes wrong - it won't leave much headroom. I would be interested how you came to the conclusion that it may fail in shear. EDIT: The thing which would really worry me is the assumption that yield will occur along the whole length of the rod. The most obvious location for the onset of yielding would be the thread - unless the minor area of the thread is MUCH larger than the cross-section area of the rest of the rod. Once the yielding starts there - this may lead to tensile failure of the thread. The second problem may be the necking anywhere on the rod (this is how rods usually fail in tension). If yielding starts locally and necking follows - we may end up with nowhere near 5% of total elongation and a fractured rod (fracture either on the minor area, or the plain section of the rod). I sincerely hope that a test (or a series of tests) have been done on the plate and on the rod itself to confirm its behavior (that is, its ability to actually achieve 5% total elongation w/o fracture or necking). And - no safety margin would make me EXTREMELY nervous. If I am reading this design correctly - the whole concept relies on uniform yielding of the rods (along their whole length), while assuming sufficient strength of the threaded section (which may be questionable if the critical section of the rod is the minor area of the thread). While this (in theory) leads to all 4 rods sharing the load equally - the resulting margin of safety is practically non-existent. Controlled yielding IMHO is a somewhat brave concept... Not a design which would make me sleep soundly at night.
@les8489 Very good point! The plate and the nuts have to be pulled through solid reinforced concrete, something I consider unlikely in the design shown. Steel rods can very well operate in a stretched state for years, e.g. cylinder head or wheel bolts. The force they have to hold does not exceed the tension they excert on the connection, so they will not encounter dynamic stretching. But here the bolts are meant to do exactly that - they are basically used as springs.
@@sthenzel Well...a long rod can work as a spring - in elastic range. Above yield - its behavior I would consider as somewhat not quite predictable (yield at threads and possible necking). The plate itself - is rather skinny. It takes the load from 2 rods (if I understand it correctly), and the bearing area on concrete is only a bit more than 70 in2. Two plates - 140 in2, and the load is 1.3 million pounds. Which would call for a very high quality concrete with compressive strength in the order of 10 psi. I think that the design is marginal, and the OP was quite right rising the issue - although shear strength of the plates may not be the actual problem.
I was in the USAF and was an aircraft mechanic, I was tasked to do safety as I did that in a former life. I was told to sit in meetings with engineers and architects that were building a new huge hangar for our F-16's. As I was looking at the blue prints for the hangar I saw a huge mistake and brought it up during one of the meetings. I was a staff Sgt, after I told what my concern was The Colonel engineer asked me "Sgt, are you an engineer? I replied no. He told me in front of the other 14 officers that when I became an engineer I could bring things up. In the next meeting I brought the item I was going to point out and just put it on the table in front of me and didn't say anything. During the meeting I saw others and the Col. looking at it from the corner of their eyes. After awhile I was asked to explain why I brought the item to the meeting. I said because this is one of the 5 things that has to be put in the hole in the hangar floor for the aircraft power and what is on the plans even this one item will not fit. The Col. then said 'maybe we should listen to the SSGT. These engineers and others doing this sort of work should keep an open mind to others that may know enough to help with design.
That's a widespread problem with society. We don't like to listen to anyone who doesn't have recognized authority on a subject, even if they do have knowledge or insight.
Many people have died simply because somebody has an ego. In the airline industry it's called crew resource management where nobody is shamed or put down, everybody's ideas are considered. Every single human being has the ability to make mistakes. ( I'm not in the airline industry or anything , i have simply learned alot about it because it interests me. There have been quite a few aviation accidents where the other crew just assumed that the captain knew what he was doing and did not speak up, due to their lack of experience compared to the captain)
@@Radi0he4d1 in a lot of situations the fact that somebody has so much more experience than someone else can play a big part in the reason why that person could make a mistake. Your doing the same things day after day. you get comfortable. you begin to think that you could do this with your eyes closed... and before you know it you're making a mistake. Whereas the less experienced new guy is constantly double and triple checking his work to make sure he's not making a mistake. Not saying that experience doesn't matter because of course it does but it can leave you vulnerable if you're not careful
See the problem here is not with the engineers and the architects, they designed whatever they designed based on the requirements the client gave them. I know that on the design side, we always ask what is going into a specific room, what sort of dimensional clearances are required, and coordinate these items with the engineers. Then it's up to the client's team to either give us the leeway to add some breathing room for later on, or min-max the hell out of the project and potentially create engineering and code issues during construction or later on.
Thanks for your work. We have recently identified a problem with a suspended slab over garage situation at our apartment complex not dissimilar to the Surfside situation. Your videos provided a heads up on the need to address such problems before they get beyond remediation. In our case it involved negotiating with the fire department to stop them parking a 15 tonne fire truck in a prohibited parking area on the common property slab that was only stressed to take 5 tonnes of load. Unfortunately too late to prevent cracking but we are negotiating with them over repairs.
You are amazing. I started listening to your videos after Miami. Love your content and explanations. Like others have said, when you can make us non-engineers understand, it’s a great job! I hope SF listens and double checks their work! You’ve made excellent points.
My dad was a civil engineer and my mother a physics major. I am neither, and hold a completely unrelated degree, but I’m knowledgeable enough to grasp the basic concepts you lay out. You link these basic concepts to the complex ones in a way that makes it easy to connect the dots, so to speak. I love this channel - it is both interesting and highly educational!
So you’re telling me, in a place with great tectonic activity which also contains soil prone to liquefaction, they built a massive residential tower that wasn’t connected to bedrock??? As a geologist this shit baffles me
Yeah, its absolutely crazy. Could only happen in the US. Would never be approved in Japan, for example - another very seismically active country. I bet all of Japan's tall buildings have piles that go down ALL THE WAY to solid bed rock.
To find errors in existing documentation is one thing. To find what is missing is next level. Its possible they did calculate it but didn't put it in the report. Still impressive find either way.
This. To find what is missing. Like the Hyatt Regency walkway collapse and its obvious but unchecked design flaws. But the Hyatt disaster contributed many lessons and reforms to engineering ethics and safety, and to emergency management. So it seems ludicrous that they have not calculated the sheering load on the bolts, thread, plate when this type of failure is so well known now.
I'm a bricklayer, I was taught in the beginning of my career if a "footing" is failing causing a wall, pillar, etc... to lean the only way to fix it is to tear it down. Over excavate refill with engineered soil compact it in 12" lifts then start all over from square 1.
@@channelsixtynine069 But... we have laws. Why are they not being enforced? Why is everyone important just pretending like they didn't see anything or the country/state has no laws that control what may and may not be done? Is that the new way of this world? Or, is it just these particular developers and engineers who are exempt? There are people living in this thing as it slowly topples over on its side and the government says nothing.
@@no_rubbernecking - The very notion of tearing down a building that is only a few years old, into what was supposed to be say a 100 year old life span, is just too horrific for those involved to contemplate. IMHO, they are trying to delay the inevitable, it was badly engineered and there is no way out of it. There is an enormous amount of money that will be written off not only in the condemned building, but also the cost of demolition and the remediation required for the land, just to end up with nothing at the end of it. What they are doing now, is like trying to balance a broom stick on end in the palm of your hand, you are forever shifting to keep it upright, it's not going to work.
@@no_rubbernecking I have to add, I'm not an engineer, but do have a technical background in another field. I always find engineering in all its forms, fascinating.
I address those in the future that will watch this video after the Millennium Tower got worse or fell over: Yes, someone figured out the problem (21:45) beforehand and no, the management team didn't care to find out.
Watching your videos reminds me why I went into Electrical Engineering instead of Mechanical Engineering. Great analysis and kudos for finding these potential design flaws.
Very good video. I'm a retired Civil Engineer and have seen this kind of thing many times before. It will be interesting to see what happens. I'm glad that I retired and don't have to be involved with things like this anymore. Did anyone look at the steel that was originally used? About 20 years ago, I saw where some foreign steel failed at 1/6 of its design load. Good Luck, Rick
@@ljubomirculibrk4097 I don't know. The company fired me because I had warned them about chinesium. I suspected that cast-iron had been used when it was supposed to be forged steel.
Josh, I am not an engineer. I am a crane operator. I do have experience with jacking heavy structures, namely 850+ short ton cranes. This remediation plan is a total ofking disaster. They are playing with fire, and it's criminally negligent imo.
@@norml.hugh-mann Maybe English isn't your first language. I have experience in jacking heavy structures. Over 30 years. My opinion is my opinion, but it's based on experience using the type of jacks which they are using. I have an understanding of engineering, and physics. This remediation wouldn't even be considered if money wasn't the primary consideration for several entities. In other words, they are placing money ahead of safety. The building should be demolished. Of course, you're welcome to YOUR OPINION, just as I am.
@@pR1mal. English can't be their first language. They obviously don't understand the difference between YOUR and YOU'RE. F**king mouth puppets these days...
If I'm an owner of a condo at Millennium Tower watching this video I would be shaking with fear. What to do? Sell. Who would buy? Stay? Every time the building would make a strange noise I'd be grabbing my heart. Tough decision time!
Maybe watch another video with a random person saying the opposite, if you are gonna rely on random youtube videos to make real estate purchasing decisions you might as well find one that isn't as pointlessly scary
You need to familiarize yourself with ACI CODE-318 Chapter 17 for anchorage design, and calculate (among other checks) the bearing stress on the anchor plate and the concrete breakout capacity. The shear capacity on the plate that you described is meaningless for embedded concrete anchors.
I hope this isn't another case of Citigroup Center or Hyatt Regency Walkway in Kansas City. I remember in my sophomore year when the professor drew up a problem and asked "will it shear?" We worked on it for about 10 minutes and said "yeah, it'll shear" That was the Kansas city walkway where a last minute design change cut a continuous column.
Just watching this and the trust being put into a tiny steel plate that hasn't actually been thought about properly reminded me of the Hyatt Regency disaster.
I watched this video and Hyatt Regency walkway failure was the first thing I thought of. Yes, it isn't really the same thing, but damn if it doesn't seem very similar.
It seems there are five additional elements in the load path that need have detailed stress analysis. 1. The nut on the threaded rod. Both the bearing and shear stress on the threads. Include the thread torque. 2. The corresponding thread in the rod. Different materials. 3. The shear stress in the plate you identified. 4. The bearing stress in the concrete that touchs the lower plate. It must not exceed the compression strength of the concrete. 5. The shear cone strength of the load path from the lower plate back into the vault. Regarding 3. To withstand 350 kips a 36 ksi steel plate can be loaded to 0.57 * 36 or 20.5ksi. In shear (Von Moses criteria) A 350k/20.5 ksi = 17+ in^2 of shear area. At 1.25 in thick that's about 14 linear inches of load path of the plate. This seems doable, with a bigger plate and deep enough nuts and washers. But the details matter. Regarding the design basis. Are the lateral and vertical ground accelerations during the design basis earthquake being considered? In the column stability calculation and in bearing strength of the rock? Also, Do they understand the load path that this composite structure will have during earthquakes. It is not clear that which footings will be stiffer and carry most of the load. No inspector or review team should approve anything until these design details are completed and checked and signed by a registered professional structural engineer. These design basis safety calculations are then checked by independent registered professional structural engineers and then reviewed by a design review team that decides whether this solution is viable. This design should probably also be tested at some scale prior to implementation. The University of California, Berkeley produces many fine structural engineers. I hope at least a few are guiding this project.
I was just thinking what they are doing is basically a small child trying to hold up an adult. California is known for earthquakes, perhaps not as much as Japan but they may not be calculating for the eventual quake that *IS* going to hit the state.
@@sc1338 Bro , he literally explained that the part in question, which had no static or dynamic load analysis done or presented, was a 1.5" x 6.5" x 13" steel plate with a 3" hole drilled through it to support over a 1/4 Million Pounds static. I guess the whole premise of the video was missed by you, or can you enlighten me?
Also, you can't use straight threaded rods in applications where they are loaded beyond their yield strength. In this case, special tension bolts are required, which do not have a continuous thread, but a stretch area with a reduced diameter. This diameter must be significantly smaller than the core diameter of the thread. There is no way those straight threaded rods will act as reliable fuses with predictable yield behavior.
Agreed - in my mind, threaded rod is not much more than a piece of rod or bar with a huge helical stress-raiser along its length yelling FAIL HERE. These civil engineers need to take a leaf out of the automotive/aeronautical design handbook!
I think, the load is limited by the amount of prestress or tightening with the jack. Once the tension load to the bolts is removed there is no more load carring capacity.
It's 2045 and I'm watching a old documentary titled "failure of the millennium" pretty cool to find your video about this failure. If only people had listened to you they would have been able to prevent this disaster.
@@georgehoyle8797 We don't really eat food in 2045, there's only protein bars now. There are rumors that the bars are actually crushed cockroaches, but I don't believe them
This reminds me of the movie Idiocracy when Joe, suddenly realizing he’s 500 years in the future, looks out the window of the hospital and sees leaning high rise buildings trussed up with cable and a car driving off an unfinished overpass down into a pile of other cars.
I also have an engineering degree unrelated to Civil engineering. I find the connection of the rods on the lower portion , plate interesting. So very little area around the nut and hole of the plate under compression , then transferred force to the area around the pvc pipe into a column of concrete. I would be worried about stress concentration around the hole and cracking the plate causing one rod to lose tension and transferring it's load to the other three. Like my college professors use to say "Show me your calculations"
If that particular piling becomes compromised, can the other 17 pilings handle the increased load, especially when the rods are already strained to 102% of annealing strength?
@@MbeyaIsHome yeah, earthquakes are unheard of in that part of the world /sarc intentional. yeah, I'd think even a small quake would pop those rods like kindling, or strip those threads.
Fascinating! Seems like they were so happy to put this vault in place and realized later, the bottom plate design was missed and just went with it anyways.
As an electrician, one of the principals of making connections is accessibility for inspection and maintenance. The idea of placing both the "fuse," AND the connections to the "fuse," within concrete, and beyond any access, defies all common sense. Yet these folks have taken it one step farther, and placed the "fuse" within concrete that is also an important load bearing member of the structure.
The choice of the word fuse is scary. The way a fuse works is that it FAILS when there's an overload. Is he telling us that this scheme will fail when there's an overload, such as an earthquake?
I have zero experience in engineering, but your presentation was so understandable that at your first mention of the plate, my first and immediate thought was, "that isn't nearly enough." Then you went on to say that AND explain it perfectly. YOU ARE THAT GOOD!
They need to tie ratchet straps from millennium tower to the neighboring tower and crank em tight. Then use expanding foam under low side. It's literally the only way to fix this reliably
Dude. Y'all are totally highballing this budget. I could just break down some reclaimed wood pallets, use wood glue as reinforcement to slab them together, and use that as a graduating shim. Save the budget for beers after a job well done! 🍺😎
YT suggested your channel to me a few weeks ago and have found your content fascinating! I’m a contractor but not an engineer. Nevertheless, I find your method of delivery very easy to follow along with and understand. Keep up the good work👍
This just gets better and better /sarcasm. I'm not an engineer, so my opinion is worth nada, but your explanation (as always) makes perfect sense to me. That vault diagram immediately reminded me of the bolted tension rods in the Kansas City Hyatt Regency Walkway collapse. On top of which, they haven't factored in seismic stresses, the equivalent of the dancers in the Hyatt Regency collapse. [Edit: so I'm like the 500th person to make this observation, but it's probably not a good sign that even a bozo like me noticed the similarity, yet the fix engineers apparently did not, or they would have thought to check the shear stress on that plate.]
I’m an EE, so only have the basic Civil courses. It would be interesting to know if the 1981 KC Hyatt Regency walkway disaster is used as a case study in Civil Engineering courses. I’m old enough to remember the event, and like you, it immediately rang a bell of familiarity for me. Perhaps the engineers on the vault remediation are all under age 45 and don’t see an eerie similarity.
Along similar lines, 161 Maiden in NYC is leaning and has foundation problems. Would like to see your take on this one as well, something for a future video. Thanks for all the great content you're creating.
I watch your channel all the time. I’m one of those “other side of the brain” types. Even simple math makes me break out in a cold sweat but you explain things so well that I finish your videos and feel like a junior engineer. You’ve got a couple of really impressive talents, you’re not only a great engineer but you’re a fantastic teacher.
Your channel and explanation is exceptional. Its very refreshing to see a real engineer (yourself) in action. Most engineers today just want to become managers, and most aren’t even good at that. As a fellow engineer, I’d like to congratulate you on your piece. I’m now subscribed.
Speaking as a software developer who also deals with numerical analysis, I'd actually expect modern FEM software to be perfectly capable of simulating this. I also expect that the person wouldn't like the answers, because what happens when you reach the limits of simulation verifiability is that modern FEM software explicitly tells you just that. You put this into any software that was well designed and you get two answers: 1) It works. 2) Disregard 1) because the parameters of the simulation exceed the verifed range of this numerical model.
When he said that this was somehow an unprecedented sort of model, so computer models for this were unlikely or unreliable, it had me wondering what he was talking about. This is a completely normal thing to model and get reliable results for. There are no unusual materials or forces involved.
Another great instructive video. I'm not an engineer (I'm an architect) but I love this channel. Even a qualitative visual assessment of the plates in question suggests that they should have an equivalent complexity and scale to one-half of the beam sitting over the ram to compensate for the transferred loads. Keep 'em coming!
Yes, and that's the section of the plate with the most strain on it because it's not being well supported by the concrete because of the hole that the rods extend down in. Wild.
And there's horrific vertical shear forces on that concrete above that 80 square inch plate. You've got 300, 000 pounds of force coming down from the building onto that plate through concrete. That's three or four feet away. That's a huge amount of shear force that could cause the concrete to have vertical cracks. I know there's a bucket load of rebar in there but it didn't bother to show it to the diagram. Terrible
Former steel detailer, current ironworker (long story), that detail of the plate spanning between those two rods looks like it was a placeholder. I can't imagine that little thing holding the kinds of loads you were saying it needs to hold. Incompetency squared on this job, just as is the case for a lot of construction endeavors. Edit: Also, I don't know much about seismic related stuff, but couldn't this vault be pulled off the main foundation?
Since the original fix was meant to have 52 piles and that was reduced down to 18. So that means roughly 3x the force is required to be taken up by each of piles and thus the plates. Hopefully that diagram was drafted for the original plan and simply wasn’t updated when the plate was beefed up significantly. Hopes are good right?
One of the great advances in building technology is being able to design things to a standard of “strong enough”. Which is actually great. It saves materials, gets rid of that forest of columns the skyscrapers of old had, the reasons it’s great are too vast to list. However; in a situation like this, overkill should be the operating principle. Every inch of structure that that plate can cover, it should cover. And if the calculations say 1-1/2” thickness is enough then it should be 2”. A catastrophic failure of that connection severely threatens a cascading collapse.
I 100% agree. Critical components that, if increased in size/capacity, don't negatively affect the budget or physics of the projects I work on get bumped up significantly.
Absolutely. A small steel plate is so cheap in comparison to drilling the huge piles into the ground. Just make the steel plate bigger! And wider and thicker threads for the bolts.
@@stevelopez372 At least profit over safety. At this point the only reasonable way out should be to dismantle the building and start from the ground up if ever again at that location. Any decision that says "We will do whatever but take it down" is putting profit over safety.
@Ingvar Hallström Might be some arrogance involved given they don't see the need for an outside engineering firm to review the project as a whole. I hope I'm just jumping to an unfounded conclusion though.
Great commentary. I'm old enough for the process you describe here to have resonance with that which resulted in the STS-51L Challenger disaster in 1986 -- what Dr Diane Vaughan described as normalisation of deviance. Those small plates transferring the entirety of the forces in the "solution" being implemented to my mind are the equivalent of the rubber O-rings in the joints of the solid rocket boosters of the Space Shuttle system -- a criticality one failure mode: if they fail to do their job, there is no backup and the entire system is prone to destruction. I for one wouldn't want to live in a building that has such a failure scenario, especially where the engineering design appears not to have been fully calculated, or independently checked.
The entire idea of these so called fuses seems crazy. It's not a fuse if it can't be replaced! They needed to come up with a non destructive way of limiting the amount of force they apply to the building.
Those plates will act like fuses....if one goes under high stress they all are likely to fail in succession. And it would take very little time, maybe seconds.
I am definitely no engineer, but used to work construction in California. We built a wood frame 3 story dormitory building at the University of California Northridge and the earthquake "hold downs" that they used were 1" threaded rods from the first floor to the second, and then stepped down each floor. I think 3/4" and 1/2". 2-1/2" threaded rods seem to be way too small for a building that size compared with 1" on a comparatively simple 3 story building.
Small correction: The Engineers that designed the "Fix" were not the structural engineers for the original building design. I meant to refer to the engineers of the current "fix" as the "original fix engineers"... not the original building engineers. If you are an engineer and want to perform your own calculations, additional material strengths can be found in the video description. I have emailed the SF Department of Building Inspections and Supervisor Peskin re this concern. I will update you all when I know more.
and I had a whole paragraph ready, good thing I didn't press send🤐
Very good explanation. Did you happen to ask these guys if they've picked this stuff up during construction? The "bearing" plate would look mighty small when compared to the giant rod on site, even if it was ungrouted. Even a non-engineer looking at it would raise questions (the steel fabricator or the site foreman). Of course, small plate or big plate, the rest of this project is a complete shambles.
They should just hire FIGG Engineers to do the review. I hear they do great work with concrete in tension!
Thank goodness I am not a decision maker on this project. San Francisco needs a team of very smart experienced structural engineers who are 100% independent and well paid and supported.
What I know from academic research and scientific literature is that when one performs a 'peer review' of, for example, a research paper (or in this specific case a design proposal), one is tasked with the verification of the work in its _entirety._
You *do not* get to _cherrypick_ whichever parts of the work/proposal/design you do 'include' in your peer review and which parts you don't!
What I mean with this is essentially as follows: when one is 'peer reviewing' a work they're essentially verifying, checking and recalculating every single part of that work to check whether or not that which is described in the work is feasible, logically sound, safe and valid from an engineering perspective in the first place (among many other things). And if they find this to be the case, and thus 'approve' of whatever it was that was proposed/established/put forth and/or claimed within the work, then the 'peer review' is complete and the peer review process is finished (unless there are multiple simultaneous peer reviews required). With the peer review process having been successfully completed, the name of whoever performed the review is forevermore connected to the work as (one of) the peer reviewing parties that approved the work. Their name and reputation (and liability, in this case) is now connected to the project, *with absolutely no CYA (covering your behind) whatsoever being allowed.* Either the project is safe and you approved it following your peer review, thus agreeing to accept any and all liability as a result, or it is unsafe, you don't approve the project as a result of your peer review and thus the project cannot continue until they fix whatever caused it to fail the review, or until they find another peer reviewer actually crazy enough to attach their name to the project and give it their blessing.
But those are just my 2 cents, but I do know for a fact that the process I described above is how these kinds of projects are usually handled in Europe.
I am a retired consulting mechanical and electrical engineer, having worked with architects for 52 years in the design of commercial and municipal buildings. I have followed your TH-cam videos and found them very interesting and informative, especially the Surfeside project. Recently I "stumbled on" a short video showing the potential failure of an apartment building for college students in Manhattan, Kansas. After viewing the video I sent an email to the city engineer, suggesting she watch that video. The apartment building was apparently fully occupied at that time. In the email I suggested that the city engineer contact Building Integrity. I did not have any reply from the city engineer. Interesting, the next day or so I saw a news report that the Manhattan fire department had condemned the building. I have not followed up, nor have there been any communications. Thanks for your good work. PN
likely busy getting lawyered up. At least they condemned the building.
Probably the City Engineer had enough chops to recognise the problem themself, once it was brought to their attention
Wow, that's incredible.
Good for you for taking the time out to report your thoughts.
It's unfortunate that nobody got back to you.
Irritating!!!
You did good.
Hope you have a wonderful weekend. 🌞
Thank you for going the extra mile to help keep people safe.
@@Chereese0808 Attorneys won't let the do so.
I have an engineering degree in an unrelated discipline. In addition to that plate (and the associated nuts), I'm also worried about the ability to transfer that much force to the existing building. The existing foundation was designed to have force distributed widely across the base. Putting that much force on the edge strikes me as a great way to run into weird loading regimes including torque, which concrete doesn't handle too well.
Yes that wedge is kind of small, especially as it would have been easy to water jet deeper under the existing slab, and then pour in a wider thicker raft to spread that load over a larger area. Not as well bonded to the structure, but with enough steel in it, and thick enough to make the slab triple the thickness in that area, it should be able to spread the point loading out a lot. Yes cast without a form, but use a high quality hydraulic concete and superplasticiser, and just keep pouring till full, with a minimum volume of concrete to ensure good cover, and you will have a much superior foundation, then can use the forms and do the rest in a few pours per section.
agree
True...but how is the system gonna behave if the building starts to move in the event of an earthquake, the forces on the foundation will suddenly have unharmonic spikes....i hope i don´t have flaw in my thinking process..
I also don't understand why the key is angled the way that it is. It's trying to push up on the building, so the top edge of the wedge would be where the force is applied. I know it's tied in with rebar, but wouldn't the angle on the top of the wedge tend to want to push the vault outward away from the building as more load is applied? Would there have been some other limitation with flipping that key vertically?
I have no engineering degree, but my first thought was "That is a lot of load going through the threads of 4 nuts (at the top near the jack)". And each thread is like 5-6 mm deep? Is that really enough to hold up the building?
I am afraid this project is headed for a monumental NOVA / Frontline collaboration episode in a few years. Thanks for the update.
NOVA for "What Happened?" Frontline for "the legal fallout from the estates of the victims." :(
@@playgroundchooser Hey at least the building is mostly empty condos owned by the ultra wealthy, for tax write offs, who won't feel much of a financial impact. The neighboring community is what will be hit the hardest.
@@StaYUTI420 What are the odds that they hire the same engineer to design more high rises along the path of destruction of this one? The newly available property will surely be discounted
Engineering disasters.. episode 642.
No, they are aware of the problem and if it gets bad enough they will externally buttress the building while they dismantle it.
UberEats driver here, If the threaded rods are loaded beyond their yield strength, couldn’t you end up with a cascade failure, once one of them snaps, the load is transferred to the adjacent rod, which snaps, and so on. Kind of like the Francis Scott Key bridge, but underground.
Nobody here: yes
That’s what killed the twin towers. Beams buckled due to heat and caused a cascade collapse.
@@RockHudrock nah - the steel has a plastic range after yield. If ya Google images of stress/strain of steel it’ll show you. There is a fracture point but this would require a much higher load to happen. By that stage the load will distribute through the other bars - but remember that the load is transferred to the pile - which will settle by an amount - so ideally the system should work together . This ignores all the other components linking the concrete box connected to the existing foundation.
TH-cam commentor here: I found your comment interesting and i agree.
Nope. Checkout torque to yield fasteners - you've probably got a bunch holding the cylinder head onto your engine. And think of the threaded rods being springs evenly distributing the load between each group of four. Conversely, if the rods were made of something really stiff (carbon fibre say) one might carry all the load, snap, then you have a cascading failure.
In the bigger picture a 3" rod going through a 1/2" plate does seem out of proportion. In the image of the jacking beam at 32:36 it appears to be 1" to 1.5" on the top and bottom of the I section with a 1/2" washer as well and closely supported by the stiffeners.
And what's happened in the last year since this video was posted? An update would be good...
This really sounds like a holdover from the 52-piling design where the plates probably would have been fine, but then they dropped 2/3rds of them and nobody really thought to check that particular part.
@ GeneralBolas good point..
Idk if I can trust a Bolas...
I was thinking the exact same thing.
Oh... Good catch. The load would have been much lower then.
this is san francisco building department. Somebody dropped a bag of cash of to a few people and they signed off. This building should be torn down.
All parties involved need to face the hard truth that the building should be dismantled completely.
@@denniswhite3487 True. And it's greed (fast-tracking, shaving a few corners, greasing a few palms?) that likely got them here.
Won't happen until somebody gets killed.
I’d question first, “Can 1/2 of the building be taken down to lightening the load?” Not a total loss at least.
@@NealD I doubt that, they let the foundation crack making bedrock piles system useless.
make it newsomes headquarters.............
You might want to consider sending this to the Insurance company providing the liability insurance. They could put the breaks on this and force the A&E and Construction company to provide the calculations. Most Insurance companies have engineers on staff.
Please! "brakes"!
You even considered for a min why nothing is being done to shut this building down, because everyone but the homeowners are corrupted? The US Dept of Justice needs to come in here and shut this building down and order a complete evacuation, followed by a demolition of the entire building.
Yep, the insurance industry's actuaries en-masse would not touch this building without being satisfied that the fix itself is safe. Excellent call.
Nice to see someone "gets it" !@@bobbymoss6160
Good idea!
I’m a professional road sweeper and my concern is that wall might collapse if I lean my broom against it.
Ahhh...a Degree in Road Maintenance 😊
Josh I think that you have identified a valid issue. As a Professional Engineer with 45 years experience, I agree that, just from observation, the size and thickness of the plate at rhe bottom of the rods appears to undersized for the magnitude of the loads proposed. This area requires careful design where you report there does not appear to be any present.
The plates are even worse than they appear at first when you consider that the weakest sections are where the threaded rods penetrate the steel plates, and this is also precisely where the concrete is also weakest owning to the holes where the rods run through them being in the same location.
Where are the city engineers who are supposed to oversee this 'fix'? Didn't they even notice that there are no calculations for the steel plate that this whole apparatus is supposed to rest upon? It is shocking that considering how flawed the design and engineering of this building is that:
A. They trusted the same engineer to come up with a solution and;
B. A qualified structural engineer in an approval capacity did not raise any alarm over this omission in calculations.
I live in the SF Bay area and have followed the story of the building for a long time and also commented on previous videos Josh has done on the project. Again, I think he is right on target with his comments. There is a concept called “cold eyes” which many have heard of. It is very much like independent peer review. I work on machinery and spent my career sailing in the engine rooms of commercial oil tankers. Many times we would have a perplexing problem so I would ask some of my qualified shipmates(other engineers) to take a look at the problem. Many times they were able to help-a lot. In the case of the Millennium Tower, some cold eyes would be strongly suggested. Sometimes being “too close” to a project keeps you from seeing some details that are important. Heck, my wife is not an engineer, but she can look at some job or issue and mention something that’s important. Also, maybe some alpha male issues come into the picture; as in ‘Hey, we’re the big time engineers and don’t tell us anything. We know, okay?”. The City of San Francisco should consider his advice, soon. Thanks, Josh. Perfectly stated.
@@Hyperlooper I just did a rough napkin calculation, and the punching shear failure of the plate is a little over 1.7 million pounds for the four rods. So while the concrete will likely suffer localized bearing failure around the plate interface, and the steel may wind up a mangled mess, some sort of catastrophic failure where the rods rip away and lose all support from the concrete is highly unlikely.
This tower is the exact case-study of why doing things cheaper is rarely better. If they'd done it right the first time, this wouldn't have been an issue in the first place.
Yeah, but the ultra-rich might not get the huge returns they were promised.
Have you ever hsd to tell a guy he might have to get by on a 250ft yacht, when he wants the 300 ft one? It's not pretty.
Best to go the cheap route, and just hope it falls down after he makes enough money to get that yacht.
@@PowerScissor
The difference here being the rich guy having something for himself and deal with the issues, and a building potentially falling and killing multiple people who had nothing to do with the rich guy's choices.
These are barely even comparable! Dude wants a yatch bigger than they can afford? Fuck this client, but consider selling anyway. Dude wants to build a cheaper building? OH HELL NAH, FUCK THAT!
when your god is money and your holy water is alcohol
@@PowerScissor Lucky Larry Silverstein would agree
it sounds like they found an engineerimg form willing to cut corners. Then when fix time came and thry got hufe estimates that required shitting parts of the city down forl ong periods they called them back forcthe same reason
Your passion for safety is addictive. I have no background in structural engineering but I watch your videos because they are very detailed and informative.
I hope your channel grows.
Thank you for that! This comment means a lot to me.
hi
@@BuildingIntegrity Indeed. Your content is awesome!
You are a great communicator of difficult subjects.
@@BuildingIntegrity The next step to to write up your concerns and send them by certified mail to the Fix Engineers, The Review Panel and to the Building Department (if you haven't already).
I was an engineer for my first year of university (then switched to Physics; go figure), and really enjoyed Statics and Dynamics (basically, the topic of this video). I also taught high school science for a little while. I read a lot of these comments, and didn't see anyone (sufficiently) praise the teaching technique. It was beautiful. I was sitting with the question "so what's at the bottom of those threaded rods?" for a couple of minutes, which made me really pay attention to what could have otherwise been very dry stuff. I'll have to remember this for when I (eventually) get back in to the classroom. Well done! The only downside is that now I have to go watch all your old videos. 🙂
Thanks, that means more than you could know.
I'm just a simple advertising exec and I wholly agree. I was able to comprehend a great deal of the importance of each piece of the 'fix' apparatus and their purpose(s) to the whole of the project. Thanks BI!
I am not an engineer, but was a PM who got to see the 4" steel base plates for the Oviatt Library lobby columns sheared right through due to the Northridge Earthquake. Engineers put a lot of faith in steel & the earth doesn't was my takeaway
I've read about that building... There was nothing wrong with the steel, the building was just unerdesigned for that large of a quake.
You've got to underpin down to the bedrock - you have to for a building of that size that in geologically-active region.
I am a UK Chartered Engineer (similar to a USA Professional Engineer). On watching your review of the drawing, I have to agree the bar/plate connection looks worryingly small. From your discussion of the calculation sheet, I understand that the bars are sleeved/greased mainly to simplify the design for "fuse" action of these bars (wherein the designer calculates a required "free length" of 160in). The bars could have been designed with a more conventional anchorage into the vault concrete (that is, a connection that can transfer load more gradually, over a longer length of bar), but then "fuse" design would become more complex as the composite behaviour of the bar and the concrete would need to be considered. By sleeving/greasing the bars, the calculation of free length for "fuse" action is greatly simplified, but by inspection all the load now has to go from the bar to the vault via the plate, just as you have explained. I am also concerned by the unchecked assumption that the jack load will be evenly distributed into all 4 bars. If there are any geometrical imperfections, some bars will take more load than others, which is very concerning since the bars are intended to yield at some point. I agree that if the bar/plate connection fails, the vaults and piles are rendered entirely useless. There would also be a sudden change in support to the Millenium Tower itself.
I don't like the idea of the tension "fuses" at all. Because of the motion and distance time scale, the dynamic load or total load on the building wouldn't be reduced. The seismic event that would stretch the rods would lift grade and effectively leave the building subgrade. Ins't that what they're trying to prevent? Like you said, additional structure anchoring the rods to the vaults would increase their effective stiffness. I don't like the idea of reducing the diameter of the rods to decrease their stiffness and make them effective "fuses" again. Bottom line is there absolutely needs to be a very detailed local stress analysis of those vault anchor plates.
I am also worried about unequal distribution of load to the 4 rods, that was the first thing that caught my attention. Then the rather smallish steel plate to transfer the load and I, too, am concerned about this design.
relative to the size of this building, these plates are like stiletto-heels? 😮 I feel like these plates ought to be footers that flare-out, like the bottom of the Eiffel Tower. 😢
I’m not an Engineer … but obviously we want to spread the load OUT, not concentrate it. 🤦♀️
I'm no engineer, but I would expect the bottom plates to be about the same size as the jacking plate. They are taking approximately the same load. Is my intuition wrong?
@@bbgun061 Various components in the system will have significantly more load carrying capacity than the amount of load carried by the system, so it is okay for the bottom plates to have less capacity than these other components. However, it is not okay for the bottom plates to have less load carrying capacity than the amount of load that they are carrying.
As mechanical engineer I would double check also the "tension fuse" calculation. I'm European, so the ASTM F1554 is not too familiar to me with all of their intricacies, not to talk about the units :) But what is perplexing to me, is the lack of taking into account the notch effect in the tension fuses. Those things, to my understanding, are all through threaded rods. The thread has a significant impact on the tension strength of the rod. There is going to also be wind affecting the building, which will cause the building to sway and that will cause the amount of tension in the fuse to alter. The thread with it's sharp crests and valleys will also act as a perfect swarm of nucleation points for cracks under fatigue load. I'd love to see how this is going to play out, but without the people inside or near the building... Do some of those ASTM or AISC things take these into account?
Also your worry about the steel plate is valid, worth some triple checking.
I think for this case they would assume the minor diameter of the threaded rod for the actual calculations, however for the stress concentrations, I think there are some equations that you can kind of just take that into effect but just multiplying everything by 0.8, though I'm not too sure this is going to be much of a cyclical loading kind of thing, mainly how it's going to be under tension constantly, the only actual dynamics being that of an earthquake
Seismic and wind forces would have been applied to the building model when determining the reactions the piles need to resist. In reality the loads these piles will sustain long term would be much smaller than the loads the rods have been designed for. The danger is when SF has another major earthquake which it will eventually...
@@AlexJoneses This is correct, the inside diameter of the treads is used to calculate its area and any factors accounting for stress concentrations of the threads ect are accounted for in the yield and ultimate stresses of the materials which are part of the ASTM F1554 standard, which helps to simplify and streamline design. The ASTM standard outlines manufacturing tolerances, how smooth/consistent the threading needs to be, and then verified testing ensures that you get what you pay for so to speak. It will also have information on metal fatigue. Gr 55 rods are actually quite ductile and resistant to metal fatigue.
As a geotechnical engineer that has observed much smaller anchors with a similar design fail while testing them, I am very concerned. If that plate fails the rods could become rod shaped missles which shoot out of their holes through the overlying vault roof. Your analysis needs a response from the design engineers and city building department.
My concern is that as the plates yield, the reduction in force on the jacks will be interpreted as a positive sign that the building is no longer sinking, instead of the reality that they have experienced plastic deformation and are close to failure.
@@Hyperlooper Unlikely. Because when that happens all the plates will fail in a cascade, and the building will begin actually settling (and will be measured elsewhere). It will be obvious anyway, since a lot of really loud bangs will be heard.
@@armamentarmedarm1699 When an element is critical, but inexpensive to upscale, the best design methodology is to overbuild that element to eliminate risk.
The cost of quadrupling the thickness of the plate (just stacking four of them even) is essentially nothing in the grand scheme of things.
THE PLATES DON'T HAVE TO FAIL.
The weakest thing has to fail.
I suspect the plates can be pulled through the concrete by the rods.
@@fhuber7507 The steel plates are also highly likely to fail/break at the rod holes, because there is not enough supporting material around these holes.
And when this happens (... to me this is just a question of 'when', not 'if' ...), there is no means of checking the state of these plates and/or the state of the rod ends, because they are firmly enclosed in concrete. From my point of view it would have absolutely been imperative to design this crucial point of potential failure in a way that would have allowed constant monitoring at any given point in time, especially with regards to the incalculable additional stress factors from seismic events in an area that is very vulnerable to earthquakes.
Also, there seems to be no provision for re-greasing the piles and the rods in their respective surrounding tubes, which I would consider a serious oversight with regards to the necessity to keep these mechanisms in an uninterupted perfect working state for decades to come - especially with regards to the fact that they are situated in enclosed underground vaults which are prone to high humidity and condensation issues.
Overall I think it would have been better/safer to have the piles and hydraulic lifts designed as pushing elements that work directly towards the (accordingly reinforced) ceilings of these vaults instead of using them as pulling elements working towards the floor sections of the vaults. By doing this the whole failure prone I-beam/rod/plate parts could have been eliminated.
Spent 25 years as a Structural Inspector (Steel/Rebar/Concrete) on NYC High Rises and I agree with you!
@suspicionofdeceit I'm not the OP but I'd probably be inclined to say "Which day of the year?"
Good for you. Most people would be ashamed to admit they stamped AOK on the twin towers construction inspections.
@suspicionofdeceitnyc has some of the best standards in the country. It's where sky scrapers were born.
Wow. If your hard hat could talk 🤫
I’m betting the plate in question might have worked with the original count of jacks they were putting in, then someone made the decision to reduce the count and they never re-visited the design of that small plate to compensate for increased loads.
It happens in engineering more often than engineers would like to admit. We're all human after all, but for sure these things should be checked
@@garrethtinsley2435 1981 Kansas City Hyatt Regency Skywalk Collapse is a tragic example.
@@garrethtinsley2435 no one can be responsible to remember everything on things this in-depth. But as you said that’s why we have thees things checked
That's why we spent a few billions on load inferencimg software.
Diversity hires is the problem.
How much will it cost to begin disassembling the building, from the top to bottom, and remove the entire thing from the city? Because... I think they will ultimately regret not doing this.
It's gotta be 10s of millions if they aren't allowed to use explosives and just bring it down in one go. The company who built it will prob just declare bankruptcy and peace out, forcing the city to pay for it's demo.
Had this been caught early enough it would have been cheaper to start over... Honestly it's looking like the fix may cost more than starting over given the risks of it failing
An absolute shitload. Especially when you include the potential losses of not being able to keep the building open, and loss in potential revenue. When you look at inflation that has taken place since the start of this building, it would likely cost more than the entire cost of the building, plus the cost of this 100+ million dollar fix. There is no way in hell they are going to remove this building, they will let SF crash and burn prior to ever removing this building. Most of these condos are 1-15 million a piece, and there is 419 condos in the building, at an average of 2-3 million each, that is like 840 million to 1.25 billion in real estate in that building, ignoring the rest of the building itself.
It would not be dismantled. It would be explosive demo.
It's not a question of if, it's a question of when.
I started studying for my engineering degree in 1981. That connection reminds me of the Kansas City Hyatt walkway connection that failed that year. Also, I've discovered over the years that proportions can give a good indication of a potential problem. In this case I see a massive pile, massive reinforced steel beam, massive anchor bolts, and a little tiny plate. Right there I would have asked questions. Final comment, as an engineer we are to try to find economies in our designs. All the components in that cross section, the Pile, the beam, the excavation, the concrete etc. The least expensive item in the whole assembly that stupid steel plate!! I would have sized a simple plate large enough to distribute the load to the concrete and with adequate thickness to resist all the shear loads. Then I would have added stiffener plates and plate washer, and it still would be the least costly component in the design. Then I would go home and had a good night sleep.
Exactly. Those plates are so underdimensioned it doesn't even visually make sense even on the blueprints. It can be seen that far away.
The Hyatt Regency walkway collapse immediately sprung to mind for me as well! This is not my field, but I have seen a fair bit on it as a case study/cautionary tale for engineers of all kinds. It's a great example because it was both a quite subtle issue, yet easy to explain to anyone.
This case though, does not seem subtle at all. It worries me that this was overlooked so easily. As a software engineer my immediate instinct is to look at all the interfaces between components and ask "What can go wrong at this point? What have we done to satisfy ourselves that this is OK?" I couldn't tell you if the plate is properly sized, but I would like to think if I was reviewing this, I'd at least be asking the question.
Here you have a chain of components that are transferring a force, and nobody did a checklist to make sure they'd thought about all of them and all the connections in between?
I’ve got the feeling that some Engineer got enamoured by tensegrity and decided to design it into a critical component without understanding the failure modes of tensegrity systems. Like you push it sideways and it fails!!
Seems to me (a non-engineer) that using cables of the sort used for post-tensioning concrete would have been a better choice. Run them in a big loop inside conduit with the end points at least several feet apart. Run three or parallel in each section allowing redundancy. No buried connections, known technology, and if cable deteriorates it can be extracted and replaced with the load temporarily transferred to the redundant cables.
FIU Pedestrian Walkway collapse?
So far, the building has tilted about 30 inches. (Another 6 inches, the plumbing and elevators will stop working).
_These are Hail Mary moves to delay that day by a few years (so that the chief engineer & city officials are retired when this happens)._
Good point! Nobody's even considering pre-collapse failure modes... SHEEEEEESH!
Chief engineer and city officials should be ARRESTED
Well, to be fair when they set up the jacks, the intention is that as the building continues to settle, it will settle the other way instead, helping to level it back out. Not gonna work with the issues with this design though.
The building in danger is analogous to the local government of San Francisco which is also tilting dramatically to the left and will fail/fall completely due to not reaching solid bedrock (values) There is a tower of babble component to this story.
@@Jack-xy2pz damn true
This situation reminds me of the Hyatt Regency walkway collapse and lack of attention on critical connections. I appreciate your approach to this and how you can make an electrical engineer understand structural engineering concepts. As opposed to most engineering designs (cars, airplanes, computers, etc.) buildings need to withstand years of minimal attention and stay within their design parameters.
I'm thinking of the concrete truss pedestrian bridge in Florida. 'Concrete' and 'truss' are words that you don't hear in conjunction very often. Similar scenario. Tensioned rods with adjusting nuts anchored in concrete. The concrete failed where the rods imparted force to the concrete.
Right on , in the St. Louis walkway collapse where the nuts pulled through holes in the beams . 200 plus people would be alive ,if they had just put big thick washers under the nuts.
The Hyatt Regency bridge collapsed because the support rod connection was changed in the shop drawing phase. The original engineering was not great, but the decision to split the rod was fatal.
In this disaster, the new design that made it easier to build, doubled the load on a set of nuts and the nuts failed at this new load plus a walkway full of people.
As soon as i saw the threaded rod in cross secrion... i thought the same thing
The original foundation was insufficient to handle the load. Remediation has proven to be insufficient as well.
It’s time to admit failure and do a tear down before we lose lives.
You haven’t been paying attention. The latest report I have seen (SF Chronicle 22 June 2023) states that the progress of the leaning has been arrested. There are no lives in imminent danger.
I don't believe there are lives in jeopardy, per se (ie. a failure of this fix would lead to catasrophic loss of life), but I do wonder if it's even worth fixing at this point. We can't even be sure this "fix" is going to work, and even if it does, would anyone actually want to live there anyhow? I mean, this place now has a bad repuation. Surely the value of each unit has been greatly diminished. Is it really worth it?
@@jasonhaynes2952 The fix has worked, so far. The objective was to arrest the leaning, and that has been done. The owners have been compensated for dimished value of their property, as I understand it.
@@GH-oi2jf So far... This just has the smell of - It was inevitable. I don't like this at all.
The current lean ratio is 30" to 600 ft. This is 1:240. As long as the structure is design for gravity notional loads (which it should be per codes) this is well within tolerance for the structure to handle. Throw in a seismic event...that would be a good one to check in the model (which I am sure they have!).
I think it's worth repeating that this huge problem could have been avoided had 5 million dollars more been spent on going down to bedrock during the ground work .
Now half billion usd is a bandage solution . Will there be a lesson learned ?
❤ this channel
Like to know how they reach these astronomical costs to fix this
nope.
@@peter-pg5yc
Are you saying it could not be avoided for any amount of money ?
@@Forakus
Yes if the building falls.. For time being, ask the people who purchased those condos . They're living a nightmare.
@@Forakus ok i misunderstood thnx
I've completed a few pull out tests on piles and grouted anchors over the years. I've seen 40mm (1 3/4 inch) steel bar fail in tension at 70% (~900kN) of its "ultimate" load (~ 1250 kN). Very similar loads to the bars in this design. I've also seen the nut on a 40mm bar pull through a 25mm (1 inch) plate at similar loads. When you are dealing with loads this extreme, things deform in ways you don't expect and sometimes attract additional loads greater than design. I would also question the concrete's ability to take the load as well as the plate. When steel fails at these loads, it's like a bomb going off!
Clearly, the engineers need bigger nuts.
6:06 6:08
The concrete figure you cite are ultimate strength. You can only use about. 20% for design.
One question well two!
........Can the threads on the bars or the pairs of nuts take the strain with out shearing off.
Why is the load transfer system - rods to tiny steel plate just a big penny washer, ?
Never mind the small steel plate. Think about the 8 nuts!!!!!!!
That plate is about the size of a cross beam connector on farm machinery here in Iowa. Like they hold the front and rear gangs of a large disc together. Sure wouldn't want them holding up a skyscraper in an earthquake prone area.
Sometimes I think that the basic design calculations made for large buildings like this should be available at a local court or something. Wasn’t there a building in NY that had bolts instead of welds, but after a visit from some engineering students they figured out that the bolts could snap and had to be replaced with welds?
Citicorp building August 1978
The problem with the building in New York, was that it met code to the letter.
An engineering student asked the question about what would happen with a diagonal wind.
The engineer, rather than blow them off, actually look to see what, in their calculations confuse them. He then determined they were right the building wouldn’t survive in a hurricane without additional diagonal bracing.
The building code is a minimum. Not a goal.
Welders are more expensive than nut turners.
I agree 100% with your assessment, the bolt anchorage will fail long before the bolt fails. In any case to design a critical element that is suppose to stabilise a massive building to be stressed beyond its yield strength is absurd and must certainly fall outside design code requirements. These bolts are designed to fail if the load is too high defeating the whole purpose of the repair work. This is a disaster in the making. (Retired structural engineer)
I don't get why the threaded rods on the sides need to be sleeved and greased. it should be stuck and moving with the vault. the only thing that should slide is the vault and the pile.
@@ericlala They need to be greased because, as the previous comment mentioned, they are designed to go beyond their yield strength. The system is RELYING on them to extend a little (without snapping!). And in order to extend without breaking the concrete, they must not be attached to the concrete.
Humpty Dumpty sat on a wall,
Humpty Dumpty had a great fall;
All the king's horses and all the king's men
Couldn't put Humpty together again.
I was just in San Fran on vacation, and our tour operator was talking about this whole cluster F. You can visually see the tower leaning compared to the neighboring buildings at certain angles.
Yikes! Residents can observe marbles and balls rolling across their units too.
@@BuildingIntegrity Yes, our tour guide told us about that. He stated he had a friend that lived in the building and demonstrated that to him. It freaked him out. Being from Miami and our recent history here with Champlain Towers, it's concerning on what's going on here. Many are claiming a huge under the table money payout to building dept personnel in San Fran, as originally the building was supposed to have piles down to the bedrock.
My gut reaction (not a structural engineer) is: (1) if the plate thickness is similar to the thickness of the top of the I-beam, then if the I-beam can resist pull-through, so can the plate; (2) However, the plate does not have the rigidity of the buttressed I-beam, and it has only a small width margin around the through hole, so it will deflect. That deflection would prevent it distributing load laterally very far, including to the transverse rebar above it, so it will be more like applying a 300 kips load to the concrete over a very small area around the rod. I don't know if that has implications for inducing fracturing of the concrete over the building lifetime. (3) If one imagines that the load starts pulling the plate around the threaded rod up through the concrete, it would then put the plate in tension, supporting the transverse rebar in a cradle. That's not what you want, but perhaps one might argue it as a fallback. (4) In that fallback, how strong is that plate in tension at the widest part of the hole? That depends on the cross section area at that point, the widest part of the hole, and depending on the hole size that looks to be _less_ than the cross section of the threaded rod, the threaded rod is at 102% of yield stress, and there's a mechanical disadvantage for the tension member in a cradle. (6) It intuitively seems that this is the one place one might add a bit more meat, given that it is inaccessible/unobservable and presumably fairly cheap in the scheme of things. At least exceeding the cross section area of the the threaded rod by a comfortable margin would seem to have at least a superficial logic to a layman. But maybe they just sized it so that it could be cut off the I beam?
@@BuildingIntegrity Residents? You couldn't pay me to live there.
Will the inability of the elevators that can no longer operate, be the end of the live ability of this leaning tower.
This video has been haunting my thoughts. Today while eating lunch, I couldn't help but think this has some spooky similarities to the Hyatt Regency walkway collapse of 1981. Insurmountable stress on threaded rods, nuts, and a steel surface far too weak for the task.
It was the first thing that came to mind and I'm just an armchair engineer bicycle mechanic and I can tell you that fix is not going to work and I hate to think what will happen it is even a minor earth tremor let alone something around the 4 to 6 scale
Yes, Hyatt Regency all over again. Only difference is these rods will push, in Hyatt the pulled through. The stresses are similar. Excellent comparison.
@@andyallen7509 the threaded rods are under a tensile load, pulling the little plates at the bottom upwards. So it's identical to the Hyatt Regency situation.
I was just about to say the same thing! I was getting creepy Hyatt Regency Skywalk vibes about this.
This does seem like history repeating itself.
I find your videos are so transparent that this complex subject becomes so clear they make the subject an exciting discovery, not some dry treatise that doubles up as a sleeping tablet.
Thank you for your work.
I’m not a numbers person at all, but I’m fascinated by the psychology/group dynamics that lead to really bad decision making. I love your channel because you explain the technical side in a way that even I can understand, and you also provide some insight into why a situation may have happened. (Too much focus on cost-cutting, assuming that someone else has done the calculations, etc.) Understanding *how* intelligent, qualified people, when put together in a group, can overlook something that seems obvious is intriguing.
Groupthink
Two adjectives are pervasive throughout: Cheap and over-confident. What could go wrong?
Cost is a huge factor. I'm not sure about San Francisco regs, but here in NYC, you can't demo buildings of this magnitude easily. So say you go through the catastrophic process of writing it all off. Now you essentially have to erect a giant shroud around the whole thing and then work from the top down breaking it down. There is a breathtaking amount of resistance to doing something like this, for obvious reasons. The last time this happened in the US was with the Bankers Trust ( Deutsche Bank ) building right next to the world trade center. It took them several years to fully deconstruct it. You can bet, due to sunk cost, that they want to avoid having to do this by any means necessary.
@@phuturephunk It could demolish itself. Side pins with partial and imperfect connection to bedrock is not re-assuring when the next earthquake hits.
Govt spends more money than they take in - effectively counterfeitting money. They take that counterfeit and reward people based off of narratives, instead of performance. Then those inept people who get all the money develop big ego's and think they're the smartest people in the world. Before you know it, incompetent people are managing multimillion dollar building projects and buildings are collapsing
As a non engineer, if I can see immediately there are problems with the planned fix, then there is a very difficult road ahead for the building, engineers & the city. Good luck. Your explanation is, as always, clear & very well illustrated. Thank you.
If I lived or worked in SF, I would make a map of the area about this building, determine the height, and draw a circle twice the height of the building (to take account for any domino effect). If I felt a significant earthquake, I would make sure I was outside that circle. Because we all know what is going to happen.
I do live and work in SF - my office is about 2000 feet from the 645-feet-hight Tower - and I have to ask: how do you expect I could “make sure” I was out of range? South of Market SF is not the easiest place to maneuver, even absent a significant earthquake...
@@malvoliosf Keep an eye on it and don't show up to work if your gut tells you, perhaps?
Get a stethoscope and listen to the walls of that building every day before you go to work. Call in sick if it has a heartbeat.
If you feel the earthquake, it's too late to get out of the area @bwktln @malvoliosf
Insanity
I am seeing this video for the first time since it was posted about 3 months ago I am NOT an engineer of aney kind but it's blatantly and egregiously obvious to my high school education and common sense that this is an excellent example of what we now know as
STOCKTON RUSH SYNDROME
It's not Stockton Rushs fault one of his passengers was wearing a Suicide Vest Bomb.
@simon1italy there's nothing funny about the Titanic Taliban
@@steven530xwhat are you talking about?
@xyz.ijk. I'm talking about the son who was wearing the suicide vest who wanted to blow up the Titanic, but before they were above the Titanic where he was going to detonate it, he was discovered. A fight ensued and the vest went off from a pressure sensor being kicked or punched.
@@steven530x May I ask... from where are you getting this information?
I am a retired electrical engineer, PE; who practiced for over for almost 50 years and I love your channel. It seems like an analysis of that plate would be integral to the functioning of that scheme. I would love to have those engineers explain to me why they chose not to do any analysis of it.
My intuition tells me the bottom plates should be the same size as the jacking plates. They're carrying the same load, right?
Why do you imagine they didn't?
@@donaldbiden1920 Because the engineer in the video said that they didn't
@@donaldbiden1920 what is the absolutely have no calculations on those plates if they had done them, we would’ve included them in the design information
Or they did they do an analysis of it, found it wanting, and could not find a cost-effective alternative, and just failed to report their findings?
I am a retired Chemical Engineer after 45 years so I only have a fundamental understanding of your presentation. I have been following work on the Millennium Tower for several years and finally I am happy to have found your work and found it to be an excellent report. I will continue to follow you on future videos. Thanks.
I admittedly don’t deal with buildings, nor have I done any calculations on this, but I am a naval architect and ships involve some truly mind-boggling loads. 1 1/2” plate is about what you’d expect to find as the flange thickness for the foundation for a big diesel, and just based on my eye, a connection where something like a bolt is loading a plate like that with 125 tons, I’d expect a lot more backup structure around those holes, with a lot more material on either side. I wouldn’t expect only 1 1/2 on either side of the bolt with no backup structure on something that important.
Just as an interested “ spectator “ I would think that those “ all thread “ bolts and washer and nuts should be about 12 inch diameter sizes , given the loading they are dealing with.
Simpler plan is to “ prune “ the building down to 10 stories.
Appears that the surrounding concrete of those "small" 'all-thread' plates is part of the expectation of support.
Perhaps they intend to use a big-assed fender washer, a lock washer, and "Blue" thread locker on the nuts at the connection point to the metal plates. You can't argue the extensive safety factor of the blue over the red.
@@frankagent7472 They will not be needed as they have put lock nuts on one end of the threaded bar.
If they wanted to silence the doubters they should have put 3 or 4 locknuts on each end of the threaded bar.
I'd expect "overkill is almost enough" for the plate preventing pulling the rod out of the concrete. Something on the order of a manhole cover near the bottom of the concrete.
So, when I need to make a minor change to my two storey house I have to follow archaic codes and get approval from oppressive city officials to make sure its "safe"... yet this skyscraper's iffy foundation design was approved as-is? Ok. I understand now.
It's amazing what you can get away with when you have money
Laws are for the poor. Always have been.
Things like this happen in plain daylight all the time and we all ignore it lmao.
Because you don't contribute enough to the fatcats....
Get buildin'! Only, we'll call it like 8, more floors to add on to your existing bungalow to be able to call it a skyscraper and do whatever you want!
... Ok maybe you'll have to tell em your skyscraper is just a baby and will be much much bigger by the time its full grown. If they start nodding and saying "oohhhh" you *know* you're in business. Suckerrrrrsssss...
💯🎯💯
I'm not a structural engineer, yet it seems to me that top-down demolition, of the Millennium Tower, is the only safe course for San Francisco.
Much better option than waiting for the next earthquake to demolish it.
The phrasing of this comment could imply you're advocating for demolishing the entire city from the top down rather than just the building.
Edit: Can all the angry boomers seriously asking for the city to be bulldozed kindly get the 🦆 out of my mentions, thank you ✨
So start on the north side of SF? 🤣
I figure at minimum the top half of the building would need to be dismantled / taken down to semi-safely accomplish any significant repair. But that's just my opinion.
@@Soken50 amended
I've been slowly completing my civil engineering degree as an older student and videos like this really help me appreciate and put into context the importance of understanding not just what the problem/solution is but why a solution will or won't work and how that plays out in the real world. Thanks.
Here is another good one. My father was the photographer on the Fred Hartman bridge that was built to replace the Baytown tunnel, in Baytown, TX. The Bridge was built with epoxy coated rebar (yellowish green coating). For years he had a piece of the rebar that had been cut and engraved with a diagram of the bridge (it was given to all the contractors). I never did find it after he passed away, but I remember it. I think we all know what happens to epoxy coated rebar, the corrosion from pinholes in the coating is far worse than with the same uncoated rebar.
Should have gone with hit dipped galvanised there, at least that will provide a protection to the steel, and then you can epoxy coat it for improved resistance.
And this is torque to yield , before the building moves some more, ...now add rust ...is this a joke or something ?? ( insert face palm here )
@SeanBZA actually most states have banned epoxy coated rebar it would still rust faster. You can though run active cathodic protection on it
@@maxgood42 rust in marine environment? That never happens
@@bernhardjordan9200 🤣
0:20 Ronald Hamburger weighs in.
Literally scrambling to get on the comments when I saw Ronald Hamburger
At this point, a slow, careful disassembly would probably be ideal.
But is this really the end of the world if this building is collapsing?
I'm pretty sure when things like that are happening, there is even more revenues that's end up being generated by all the news agencies, TV channels, TH-cam videos, etc... than the original value of the building itself. Not to mention that every time something like that is happening, the people are getting close together and it turns into something very heartwarming. And there is also all the knowledge that we can get from the investigations for the future building constructions, etc...
Or one extremely oversize explosion that levels the whole state.
Probably more cost effective to implode it and maybe start again, or just dont build one
@@Reth_Hard Yes, it's always so heartwarming when people die under piles of rubble. The peace, the calm, the toxic dust wafting in the breeze...
@@dontask8979 FINALLY Someone is making sense.
Because the vault only being connected on one side to the building, the rods closer to the building will experience a higher load. The whole thing will try to rotate towards the building due to non symmetrical loading.
That's what I was looking at. The typical placement of the rods is in direct alignment under the wall. Only compression forces pushing downward on the existing pylons. These compartments are side mounted to the basement. Concrete is very weak in tension loading even with rebar. The weight of the building is going to apply a moment force to the thin wall of the building foundation and crack the entire length of the side at the top line of the basement. The better option is to replace a set of existing pylons with this setup. The load needs to be directly over the pylons, not cantilevered off the side.
I thought the whole point of the side pylons was to simply slow the settlement on the faster side. This is why the rods are designed to yield right? So they do not actually hold up the building only on one side? Once the settlement rate is slowed the rest of the building will not experience any shearing since it will be more or less evenly supported. The only shear forces will be the uptake of that extra load, which should only be a small fraction of the total weight.
Or am I misunderstanding how this fix is supposed to work?
@@lucusloc The building load is, currently, straight down at the wall. Suppose the wall is an 8foot long 1foot tall 3/4inch thick plywood. All interior forces are pressing down on the upper edge of this wood. If you take a dead blow hammer and tap irregularly along the edge, this will drive the 3/4inch thick wood into the ground like a knife. Live loading is like this, and the edge will descend vertically, yet evenly end to end, which is the situation as it exists today. However, in this building, one end is digging in faster.
Next, attach a two chunks of 2x4 along one side at 2 different locations. Now tap with the hammer again. Notice that the board will tend to warp. That warp cannot be avoided because of uneven forces caused by rotational forces at the attachment points of each 2x4 block. No matter how lightly you tap, the board will warp as the edge buries itself deeper into the ground. Wood can take this kind of uneven force. Concrete fails under this type of loading, hence the cracks in driveways and sidewalks as the concrete settles. The basement wall of this building will crack under the warpage caused by those side loading pylon boxes (2x4s). It will crack along a horizontal line drawn between the top of the 2 pylon boxes. That is why pylons under skyscrapers have to be directly under the load, that makes them part of the compression loading. The fix pulls the support off to the side of the wall, putting tension on the inside wall of the basement at the top of the pylon boxes. This is bad.
I’m not an engineer in any form, but when I first saw the design in this video I had a similar thought.
Man I love this story! Thanks for all the effort and analysis on the millennium tower!
My pleasure!
You wouldn’t love this story if you lived there.
24 year homeowner in SF. I have nothing but contempt and disdain for San Francisco Building Dept and Planning Dept over a dozen first hand interactions. I wish them the worst
Sadly it’s the civilizing caught in a potential collapse who will likely pay the price.
Diversity making us wrong in action.
You live in San Francisco. What exactly did you expect? People who willingly stay in California deserve absolutely everything crappy that happens to them...
@billymacktexasdetective5827 Yea, they should live in dust bowl west Texas like you.
LOL
@sfojimbo5889 Well, I don't live in Texas, so I'm not sure what you are talking about. Idiot...
Liberals should stay in liberal cities and states. The sane majority of America doesn't want them around...
As an engineer from a different discipline entirely, this is really interesting to watch. Thank you for making it so accessible!!
30:00 really sums up the video. The fact that the team (the firm, maybe not the exact people) who got it wrong in the first place.. have been entirely left to their own devices to re-do the whole fix and then be BLINDLY trusted that "Yep, this time they will get it right, for sure!". Blows my mind!
Well explained as always and I hope this video, as you say, reaches the right levels somewhere to get those calculations done independently!
" trust the experts" ™
There is *A LOT* of that going around for the last few years...😆
I should not be left to my own devices
They come with prices and vices
I end up in crisis.
-Taylor Swift, 2022 (Anti Hero)
Also, should be these engineers
It's all about favortism and politics
@@qwerty112311
I would swallow my pride,
I would choke on the rines
But the lack there of would leave me empty inside.
Eve6 - Heart in a blender
It's like Nietzche said...some people lose their last ounce of value when they cast away the bonds that kept them in check.
If someone has no values, no moral compass, no restrain at all *within themselves* ... then they can only design, build and do harmful things.
Respectfully 👍✌️🎩
Hey - no fair. What about third time lucky?
You are so good at explaining all this highly technical stuff to lay people like myself. I feel so good that I actually understand what you are talking about. I hope your channel grows and you have more time to do more of these videos .
Thank you. Time is my biggest constraint. I am running a full time engineering firm, raising a family, and building our dream house right now; so these videos have been VERY difficult to get out. Things should smooth out in the future though. I appreciate your comment.
@@BuildingIntegrity As a non-engineer (medical background ) I find each of your videos entirely clear and fascinating - the wait till your next is well worth it every time. (maybe show us your house when its done too?)
The force exerted on the side of the original foundation is the biggest issue I see here. It’s going to snap and when it does all the energy saved up over any length of time will release instantly.
I agree with you 100 percent. The key way connection isn’t anywhere close to deep enough.
Great point. Opposite side original design could be in tension now with a wind lateral force blowing in the ‘wrong’ direction.
That's exactly what will happen, and not very far in the future.The building should be demolished.
This is why they designed the rods to yield. It limits the load transferred between the vault and foundation wall, so that the foundation wall doesn't get over loaded.
Literally EVERYTHING about this building has been "Oh no! It's doing something unexpected! But we totally got it this time!" like 7 times in a row now.
That building is coming down one way or another. The only choice is whether it falls down or we bring it down. Some one has to decide to just cut their losses and write it off at this point.
I sincerely hope it can be dismantled and rebuilt elsewhere, where the ground is sturdier. It sounds like the overall design is okay - just not great, and certainly not for this location.
I've been looking for a comment along these lines. Sometimes mistakes are made and there's no getting around them. That's what this situation strikes me as. It's probable that there isn't an engineering fix here. Sometimes admitting defeat isn't bad. Time to put the building out of its misery (before it puts lots of someones out of their's.)
My thoughts exactly!
M.D., your statement is definitely right. Now the real life problem is: who is going to pay ($$$$) for it? Accusations will fly, lawyers will be marching in. "Ouch!! What is hurting there inside my wallet?"...
@@richardhack9830 It's not like SF has any shortage of money being thrown directly into incinerators. They'll be fine.
I am not an engineer but just viewing this video reminds me of the old adage. “There is never enough time to do it right, but there is always enough time to do it over.” ~John W. Bergman.
When I saw that they built this monstrous building on sand-supported pilings, I just shook my head. When they built my house, they did this same "engineering" - and guess what? I paid big bucks to do perimiter pilings to jack the joint back up. And - yes, we have foundation dishing. Go figure...
Who could have guessed an engineering method that even failed to work on a house would work flawlessly on a sky scraper lol
That's because it is your house.
I will bet that none of the engineers, architects, developers, etc. own anything in the Millennium tower.
Their only ownership is the extra proceeds from cutting corners.
Nice video. As a project manager and former structural engineer in the construction industry I found it very interesting. This kind of anchoring in concrete structures needs thorough consideration and I found it hard to believe that the responsible people did not take this detail into account. Apart from the anchor plate also the transfer of forces from the plate into the concrete and from the anchoring sideways to the existing foundation is an important detail. What I also miss but perhaps you deliberately kept it out of the video is the fact that the extra support is only placed on the outside of the foundation slab of the building while the existing piles are distributed over the entire slab. The newly placed piles will alter the distribution of forces acting on the slab. Just a thought. It's also interesting that the whole proces of development and construction is being highlighted. Very recognizable!
Hi, thanks again for a brilliant post. Back in Sept '74 Ted Heath's yacht Morning Cloud sank off Brighton, UK, with a fatality. The wreck was eventually recovered by Bellsize Boatyard. The bow was mounted onto a sheet of marine ply and presented to public gaze at the front of the yard. The yacht was of composite build, wooden hull - 6mm stainless plate chassis to which the ballast keel was bolted. The holes through which the keel bolts were fixed looked like bullet holes, they had simply pulled through. Not backed up with large washers. Sounds too simple, doesn't it. Now I come to your point about the inadequate size of the new support beams/bars in the Millennium Tower. You can calculate all the stresses and strains that take place in a more or less static building but impact loading is another factor which comes from the seat of the pants. In the case of the yacht it is wave action that has to be dealt with. In the case of the Tower it's seismic activity. In the case of the jacks and bolts, calculate the sizes THEN DOUBLE IT.
My only comment is that you are too quiet for too long. I look forward to your posts. Regards Pete on the Isle of Wight. (Retired engineer)
Yeah a little alarmed at that. We use 1 1/2" plate at my work but we put no where near those level of loads on it. This really feels like a part that should have been wildly over engineered and instead we seem to have something that is maybe just barely good enough at best to do the job.
I would suggest contacting the local news outlets in SF. Unless someone happens to have an in with the building department the only way to get this reviewed is to publicly humiliate them.
@ Building Integrity Yes, you are right of course.
1 The plates between the pairs of greased/sleeved 'all-thread' rods should not be mere plates. They should be I-beams more like the one spanning the jack; strong enough to resist pull through, shear, bending and big enough that the concrete crushing strength is not exceeded.
2 SFO Building Control should do more than look at the Engineer's calcs and say they have reviewed them.
3 Clearly, SFO BC and the Engineer of Record have completely overlooked this element in the load path. However, I question the whole concept of 18 small piles on one corner
The last significant piles that I designed were bored between the escalator tunnel and running tunnels of the Victoria Line. It was only a 15 storey building and the piles were a lot bigger than what you show. 30MN IIRC so nearly 7million pounds force in your money.
The calcs shown are neat but cursory for such a significant building. In the UK any SE consultancy would carry out computer modelling to show the stress levels in the plate and in the concrete. It would be red so it would then be resized and recalculated until it was right. They would analyse the raft and how this altered the stresses in the raft.
Even if the plates are redesigned will these 18 piles have enough resistance to carry the building? I think not.
Your diagram showing a piled raft with perhaps hundreds of shallow piles suggests:
either the piles themselves are poor quality and creep compressing under the load more than the others
or the ground at depth is simply overstressed (if not block failure, block compression) - as the ground has compressed under load X it will continue to compress under 9/10th the load at 90% of current rate ( if the 18 even take 1/10th)
If 18 piles at the perimeter generate enough resistance and the redesigned plates hold and beefed up reinforcement in the concrete holds, then they will likely overstress the pile cap. The pile cap was likely designed on local shear; not to span from that corner to half-way across the building. So, has the Engineer of Record re-analysed the pile cap and proven its capacity? Hmm!
I am a not an engineer, but this video is great. Breaks everything down into understandable concepts and terms. Well done.
I am an aeronautical engineer and have no much familiarity with building standards - but:
The effective bearing area of the steel plate is 6.5"x12"x1.1 -2x3.141*3^2/4 = 71.6in2
Compressive strength of concrete is anywhere between 4,000 and 10,000 psi - so even with the lowest value the concrete covering the plate can take 286,000 lbf, and probably quite a bit more.
Cross-section of the plate is 6.5"x1.5" =9.75in2. Shear strength of grade 55 steel (assuming that the plate is grade 55) is about 50-55 ksi. So, the plate can take about 487,000 lbf in shear (from one rod).
Can the lower nuts be pulled through the plate ? Without getting into the nut dimensions - a circular shear section area 3" in diameter through the thickness (around the bolt) is about 3.141x3x1.5 = 14.1in2 (more than the cross-section area of the plate based on 6.5" width). So - pulling the nuts through the plate would require about 705,000 lbf. So - I do not think that shear is a problem here.
Having said that - the design operates above yield stress. Any rod which exceeds its yield stress will start shedding the load between the remaining 3 rods - which in effect will equalize the load and share it equally between all 4 rods. This is good and makes sense - but leaves no room for any safety factor -which practically does not exist. Even in aircraft design a minimum safety factor of 1.5 is required...I
In short - the design makes sense, but if something goes wrong - it won't leave much headroom.
I would be interested how you came to the conclusion that it may fail in shear.
EDIT: The thing which would really worry me is the assumption that yield will occur along the whole length of the rod. The most obvious location for the onset of yielding would be the thread - unless the minor area of the thread is MUCH larger than the cross-section area of the rest of the rod. Once the yielding starts there - this may lead to tensile failure of the thread. The second problem may be the necking anywhere on the rod (this is how rods usually fail in tension). If yielding starts locally and necking follows - we may end up with nowhere near 5% of total elongation and a fractured rod (fracture either on the minor area, or the plain section of the rod).
I sincerely hope that a test (or a series of tests) have been done on the plate and on the rod itself to confirm its behavior (that is, its ability to actually achieve 5% total elongation w/o fracture or necking).
And - no safety margin would make me EXTREMELY nervous. If I am reading this design correctly - the whole concept relies on uniform yielding of the rods (along their whole length), while assuming sufficient strength of the threaded section (which may be questionable if the critical section of the rod is the minor area of the thread). While this (in theory) leads to all 4 rods sharing the load equally - the resulting margin of safety is practically non-existent. Controlled yielding IMHO is a somewhat brave concept...
Not a design which would make me sleep soundly at night.
among all 4 rods
Thanks, finally a comment with math and not with "feel like it looks small..."
@les8489
Very good point!
The plate and the nuts have to be pulled through solid reinforced concrete, something I consider unlikely in the design shown.
Steel rods can very well operate in a stretched state for years, e.g. cylinder head or wheel bolts.
The force they have to hold does not exceed the tension they excert on the connection, so they will not encounter dynamic stretching.
But here the bolts are meant to do exactly that - they are basically used as springs.
@@sthenzel Well...a long rod can work as a spring - in elastic range. Above yield - its behavior I would consider as somewhat not quite predictable (yield at threads and possible necking). The plate itself - is rather skinny. It takes the load from 2 rods (if I understand it correctly), and the bearing area on concrete is only a bit more than 70 in2. Two plates - 140 in2, and the load is 1.3 million pounds. Which would call for a very high quality concrete with compressive strength in the order of 10 psi. I think that the design is marginal, and the OP was quite right rising the issue - although shear strength of the plates may not be the actual problem.
@merzto your comment scares me. this must be rectified. before I wail.
I was in the USAF and was an aircraft mechanic, I was tasked to do safety as I did that in a former life. I was told to sit in meetings with engineers and architects that were building a new huge hangar for our F-16's. As I was looking at the blue prints for the hangar I saw a huge mistake and brought it up during one of the meetings. I was a staff Sgt, after I told what my concern was The Colonel engineer asked me "Sgt, are you an engineer? I replied no. He told me in front of the other 14 officers that when I became an engineer I could bring things up. In the next meeting I brought the item I was going to point out and just put it on the table in front of me and didn't say anything. During the meeting I saw others and the Col. looking at it from the corner of their eyes. After awhile I was asked to explain why I brought the item to the meeting. I said because this is one of the 5 things that has to be put in the hole in the hangar floor for the aircraft power and what is on the plans even this one item will not fit. The Col. then said 'maybe we should listen to the SSGT. These engineers and others doing this sort of work should keep an open mind to others that may know enough to help with design.
That's a widespread problem with society. We don't like to listen to anyone who doesn't have recognized authority on a subject, even if they do have knowledge or insight.
"I''m senior so I'm automatically right" is the most toxic, destructive, and ignorant stance someone can hold in a relationship or workplace
Many people have died simply because somebody has an ego. In the airline industry it's called crew resource management where nobody is shamed or put down, everybody's ideas are considered. Every single human being has the ability to make mistakes. ( I'm not in the airline industry or anything , i have simply learned alot about it because it interests me. There have been quite a few aviation accidents where the other crew just assumed that the captain knew what he was doing and did not speak up, due to their lack of experience compared to the captain)
@@Radi0he4d1 in a lot of situations the fact that somebody has so much more experience than someone else can play a big part in the reason why that person could make a mistake. Your doing the same things day after day. you get comfortable. you begin to think that you could do this with your eyes closed... and before you know it you're making a mistake. Whereas the less experienced new guy is constantly double and triple checking his work to make sure he's not making a mistake. Not saying that experience doesn't matter because of course it does but it can leave you vulnerable if you're not careful
See the problem here is not with the engineers and the architects, they designed whatever they designed based on the requirements the client gave them. I know that on the design side, we always ask what is going into a specific room, what sort of dimensional clearances are required, and coordinate these items with the engineers. Then it's up to the client's team to either give us the leeway to add some breathing room for later on, or min-max the hell out of the project and potentially create engineering and code issues during construction or later on.
Thanks for your work.
We have recently identified a problem with a suspended slab over garage situation at our apartment complex not dissimilar to the Surfside situation.
Your videos provided a heads up on the need to address such problems before they get beyond remediation.
In our case it involved negotiating with the fire department to stop them parking a 15 tonne fire truck in a prohibited parking area on the common property slab that was only stressed to take 5 tonnes of load.
Unfortunately too late to prevent cracking but we are negotiating with them over repairs.
Yes, you did uncover the $10,000,000 mistake, and what we need is more engineers just like you.
Much more then 10 million my guy
You are amazing. I started listening to your videos after Miami. Love your content and explanations. Like others have said, when you can make us non-engineers understand, it’s a great job! I hope SF listens and double checks their work! You’ve made excellent points.
My dad was a civil engineer and my mother a physics major. I am neither, and hold a completely unrelated degree, but I’m knowledgeable enough to grasp the basic concepts you lay out. You link these basic concepts to the complex ones in a way that makes it easy to connect the dots, so to speak. I love this channel - it is both interesting and highly educational!
So you’re telling me, in a place with great tectonic activity which also contains soil prone to liquefaction, they built a massive residential tower that wasn’t connected to bedrock??? As a geologist this shit baffles me
Yeah, its absolutely crazy. Could only happen in the US. Would never be approved in Japan, for example - another very seismically active country. I bet all of Japan's tall buildings have piles that go down ALL THE WAY to solid bed rock.
@@simontay4851*China* : Hold my Tsingtao
Corruption, not illogical.
Tech is amazing but sensitive.
This is a good example of doing right the first time.
On the other hand everyone involved need to face reality that the building needs to come down.
The problem is the company is bankrupt either way so the don’t care.
It will fall down kill thousands of people and they will walk away…..
No way I personally would live anywhere near this building 😳
@@carlmorgan8452 you sound like an investor or a gambler.
To find errors in existing documentation is one thing. To find what is missing is next level. Its possible they did calculate it but didn't put it in the report. Still impressive find either way.
This.
To find what is missing.
Like the Hyatt Regency walkway collapse and its obvious but unchecked design flaws.
But the Hyatt disaster contributed many lessons and reforms to engineering ethics and safety, and to emergency management.
So it seems ludicrous that they have not calculated the sheering load on the bolts, thread, plate when this type of failure is so well known now.
@@jonmobrien shearing load
I'm a bricklayer, I was taught in the beginning of my career if a "footing" is failing causing a wall, pillar, etc... to lean the only way to fix it is to tear it down. Over excavate refill with engineered soil compact it in 12" lifts then start all over from square 1.
Agreed, nothing is going to fix this, other than tearing it down, but no one wants to admit it.
@@channelsixtynine069 But... we have laws. Why are they not being enforced? Why is everyone important just pretending like they didn't see anything or the country/state has no laws that control what may and may not be done? Is that the new way of this world? Or, is it just these particular developers and engineers who are exempt? There are people living in this thing as it slowly topples over on its side and the government says nothing.
@@no_rubbernecking - The very notion of tearing down a building that is only a few years old, into what was supposed to be say a 100 year old life span, is just too horrific for those involved to contemplate. IMHO, they are trying to delay the inevitable, it was badly engineered and there is no way out of it. There is an enormous amount of money that will be written off not only in the condemned building, but also the cost of demolition and the remediation required for the land, just to end up with nothing at the end of it.
What they are doing now, is like trying to balance a broom stick on end in the palm of your hand, you are forever shifting to keep it upright, it's not going to work.
@@channelsixtynine069 That's an excellent metaphor. Thanks for your explanation!
@@no_rubbernecking I have to add, I'm not an engineer, but do have a technical background in another field. I always find engineering in all its forms, fascinating.
I address those in the future that will watch this video after the Millennium Tower got worse or fell over: Yes, someone figured out the problem (21:45) beforehand and no, the management team didn't care to find out.
Watching your videos reminds me why I went into Electrical Engineering instead of Mechanical Engineering. Great analysis and kudos for finding these potential design flaws.
You mean structural engineering.
Very good video. I'm a retired Civil Engineer and have seen this kind of thing many times before. It will be interesting to see what happens. I'm glad that I retired and don't have to be involved with things like this anymore. Did anyone look at the steel that was originally used? About 20 years ago, I saw where some foreign steel failed at 1/6 of its design load. Good Luck, Rick
1/6 th of the load?
How is that posible?
Britle fracture or what?
@@ljubomirculibrk4097 I don't know. The company fired me because I had warned them about chinesium. I suspected that cast-iron had been used when it was supposed to be forged steel.
Oh, damn old chinesium
@@richardross7219 nah, it was probably chitoresium, or chiurabismutoresium
@@ljubomirculibrk4097 Chinesium steel.
Josh, I am not an engineer. I am a crane operator. I do have experience with jacking heavy structures, namely 850+ short ton cranes. This remediation plan is a total ofking disaster. They are playing with fire, and it's criminally negligent imo.
Yup... and I doubt "earthquake" was an input to the calculations either...
Technically the PE’s are criminally liable, they’re playing with more than fire.
@@prjndigo An earthquake? In San Francisco? Come one, what are the chances of that happening... /s
@@norml.hugh-mann Maybe English isn't your first language. I have experience in jacking heavy structures. Over 30 years. My opinion is my opinion, but it's based on experience using the type of jacks which they are using. I have an understanding of engineering, and physics. This remediation wouldn't even be considered if money wasn't the primary consideration for several entities. In other words, they are placing money ahead of safety. The building should be demolished. Of course, you're welcome to YOUR OPINION, just as I am.
@@pR1mal. English can't be their first language. They obviously don't understand the difference between YOUR and YOU'RE. F**king mouth puppets these days...
If I'm an owner of a condo at Millennium Tower watching this video I would be shaking with fear. What to do? Sell. Who would buy? Stay? Every time the building would make a strange noise I'd be grabbing my heart. Tough decision time!
They are suing already. Look up Joe Montana's lawsuit
@@samuelsmash Uhhhh, I am not sure we watched the same video...
Sell to old people who would like to be on international news when they die? Definitely going out with a bang if this fails! 😂
Maybe watch another video with a random person saying the opposite, if you are gonna rely on random youtube videos to make real estate purchasing decisions you might as well find one that isn't as pointlessly scary
Sell. Its not worth your life. You wanna be a live test dummy if ut does collapse? I use to build stuff like this. I dont trust none of these people.
You need to familiarize yourself with ACI CODE-318 Chapter 17 for anchorage design, and calculate (among other checks) the bearing stress on the anchor plate and the concrete breakout capacity. The shear capacity on the plate that you described is meaningless for embedded concrete anchors.
I hope this isn't another case of Citigroup Center or Hyatt Regency Walkway in Kansas City. I remember in my sophomore year when the professor drew up a problem and asked "will it shear?" We worked on it for about 10 minutes and said "yeah, it'll shear" That was the Kansas city walkway where a last minute design change cut a continuous column.
It looks a lot like that hotel walkway. Nuts.
Just watching this and the trust being put into a tiny steel plate that hasn't actually been thought about properly reminded me of the Hyatt Regency disaster.
@@Teverell Yeah, a simple single long column that changed to two separate columns was all it took to bring it down.
Hyatt Regency Walkway - *that*'s what I was trying to remember. (I remembered it, just couldn't recall the name)
I watched this video and Hyatt Regency walkway failure was the first thing I thought of. Yes, it isn't really the same thing, but damn if it doesn't seem very similar.
It seems there are five additional elements in the load path that need have detailed stress analysis.
1. The nut on the threaded rod. Both the bearing and shear stress on the threads. Include the thread torque.
2. The corresponding thread in the rod. Different materials.
3. The shear stress in the plate you identified.
4. The bearing stress in the concrete that touchs the lower plate. It must not exceed the compression strength of the concrete.
5. The shear cone strength of the load path from the lower plate back into the vault.
Regarding 3. To withstand 350 kips a 36 ksi steel plate can be loaded to 0.57 * 36 or 20.5ksi. In shear (Von Moses criteria) A 350k/20.5 ksi = 17+ in^2 of shear area. At 1.25 in thick that's about 14 linear inches of load path of the plate. This seems doable, with a bigger plate and deep enough nuts and washers. But the details matter.
Regarding the design basis. Are the lateral and vertical ground accelerations during the design basis earthquake being considered? In the column stability calculation and in bearing strength of the rock? Also, Do they understand the load path that this composite structure will have during earthquakes. It is not clear that which footings will be stiffer and carry most of the load.
No inspector or review team should approve anything until these design details are completed and checked and signed by a registered professional structural engineer. These design basis safety calculations are then checked by independent registered professional structural engineers and then reviewed by a design review team that decides whether this solution is viable.
This design should probably also be tested at some scale prior to implementation.
The University of California, Berkeley produces many fine structural engineers. I hope at least a few are guiding this project.
Let's make sure they don't forget earthquakes
I was just thinking what they are doing is basically a small child trying to hold up an adult. California is known for earthquakes, perhaps not as much as Japan but they may not be calculating for the eventual quake that *IS* going to hit the state.
It’s not just the weight of the building they should be calculating in but also the seismic forces that this building will encounter.
Dynamic loads were included. Get good noob
@@sc1338 why add the snark?
Agreed. The fact that this nightmare building is in San Francisco, next door to the huge transit hub, makes the malpractice so much worse.
@@vicw9223 I was joking. Hence the “get good noob” 😂
@@sc1338 Bro , he literally explained that the part in question, which had no static or dynamic load analysis done or presented, was a 1.5" x 6.5" x 13" steel plate with a 3" hole drilled through it to support over a 1/4 Million Pounds static. I guess the whole premise of the video was missed by you, or can you enlighten me?
Also, you can't use straight threaded rods in applications where they are loaded beyond their yield strength. In this case, special tension bolts are required, which do not have a continuous thread, but a stretch area with a reduced diameter. This diameter must be significantly smaller than the core diameter of the thread. There is no way those straight threaded rods will act as reliable fuses with predictable yield behavior.
Agreed - in my mind, threaded rod is not much more than a piece of rod or bar with a huge helical stress-raiser along its length yelling FAIL HERE. These civil engineers need to take a leaf out of the automotive/aeronautical design handbook!
I think, the load is limited by the amount of prestress or tightening with the jack. Once the tension load to the bolts is removed there is no more load carring capacity.
It's 2045 and I'm watching a old documentary titled "failure of the millennium" pretty cool to find your video about this failure. If only people had listened to you they would have been able to prevent this disaster.
Bush did millennium ! !
WAKE UP SH33PL3
How’s the food in 2045?
@@georgehoyle8797 We don't really eat food in 2045, there's only protein bars now.
There are rumors that the bars are actually crushed cockroaches, but I don't believe them
@@georgehoyle8797 probably shite
@@georgehoyle8797 Awful, so much more candy and pastries are made with titanium nowadays....
This reminds me of the movie Idiocracy when Joe, suddenly realizing he’s 500 years in the future, looks out the window of the hospital and sees leaning high rise buildings trussed up with cable and a car driving off an unfinished overpass down into a pile of other cars.
I also have an engineering degree unrelated to Civil engineering. I find the connection of the rods on the lower portion , plate interesting. So very little area around the nut and hole of the plate under compression , then transferred force to the area around the pvc pipe into a column of concrete. I would be worried about stress concentration around the hole and cracking the plate causing one rod to lose tension and transferring it's load to the other three. Like my college professors use to say "Show me your calculations"
If that particular piling becomes compromised, can the other 17 pilings handle the increased load, especially when the rods are already strained to 102% of annealing strength?
250,000 lbs per rod? Or 120 car's weight?
And what about earthquakes?
@@MbeyaIsHome yeah, earthquakes are unheard of in that part of the world /sarc intentional. yeah, I'd think even a small quake would pop those rods like kindling, or strip those threads.
Lateral rebar connection of vault to foundation looks dodgy as well. This area has to withstand building's downward force and the jack's upward force.
Fascinating! Seems like they were so happy to put this vault in place and realized later, the bottom plate design was missed and just went with it anyways.
As an electrician, one of the principals of making connections is accessibility for inspection and maintenance. The idea of placing both the "fuse," AND the connections to the "fuse," within concrete, and beyond any access, defies all common sense. Yet these folks have taken it one step farther, and placed the "fuse" within concrete that is also an important load bearing member of the structure.
I agree. All of the threaded rod "fuse" should have been placed above the concrete.
We saw how well concrete encased steel worked in the Morandi Bridge.
Yeah, except when you don't attach the threaded rods to the concrete then it doesn't work at all. It has to be placed in the concrete.
The choice of the word fuse is scary. The way a fuse works is that it FAILS when there's an overload. Is he telling us that this scheme will fail when there's an overload, such as an earthquake?
@@henryD9363 right. and then what? do you demo all the vaults and start over?
I have zero experience in engineering, but your presentation was so understandable that at your first mention of the plate, my first and immediate thought was, "that isn't nearly enough." Then you went on to say that AND explain it perfectly. YOU ARE THAT GOOD!
They need to tie ratchet straps from millennium tower to the neighboring tower and crank em tight. Then use expanding foam under low side. It's literally the only way to fix this reliably
Silly........everyone knows that UFFI would require a suitable stack of wood shim reinforcement.
Just call slabjack . I would advise leaving the ratchet strap
😂😂😂
I was thinking at least a couple of 4x4’s and some instant postcrete
Dude. Y'all are totally highballing this budget. I could just break down some reclaimed wood pallets, use wood glue as reinforcement to slab them together, and use that as a graduating shim. Save the budget for beers after a job well done! 🍺😎
YT suggested your channel to me a few weeks ago and have found your content fascinating! I’m a contractor but not an engineer. Nevertheless, I find your method of delivery very easy to follow along with and understand.
Keep up the good work👍
Welcome aboard!
This just gets better and better /sarcasm. I'm not an engineer, so my opinion is worth nada, but your explanation (as always) makes perfect sense to me.
That vault diagram immediately reminded me of the bolted tension rods in the Kansas City Hyatt Regency Walkway collapse. On top of which, they haven't factored in seismic stresses, the equivalent of the dancers in the Hyatt Regency collapse.
[Edit: so I'm like the 500th person to make this observation, but it's probably not a good sign that even a bozo like me noticed the similarity, yet the fix engineers apparently did not, or they would have thought to check the shear stress on that plate.]
I’m an EE, so only have the basic Civil courses. It would be interesting to know if the 1981 KC Hyatt Regency walkway disaster is used as a case study in Civil Engineering courses. I’m old enough to remember the event, and like you, it immediately rang a bell of familiarity for me. Perhaps the engineers on the vault remediation are all under age 45 and don’t see an eerie similarity.
Along similar lines, 161 Maiden in NYC is leaning and has foundation problems. Would like to see your take on this one as well, something for a future video. Thanks for all the great content you're creating.
I watch your channel all the time. I’m one of those “other side of the brain” types. Even simple math makes me break out in a cold sweat but you explain things so well that I finish your videos and feel like a junior engineer. You’ve got a couple of really impressive talents, you’re not only a great engineer but you’re a fantastic teacher.
Don't feel bad, the best engineers are bad teachers
Your channel and explanation is exceptional. Its very refreshing to see a real engineer (yourself) in action. Most engineers today just want to become managers, and most aren’t even good at that. As a fellow engineer, I’d like to congratulate you on your piece. I’m now subscribed.
Speaking as a software developer who also deals with numerical analysis, I'd actually expect modern FEM software to be perfectly capable of simulating this. I also expect that the person wouldn't like the answers, because what happens when you reach the limits of simulation verifiability is that modern FEM software explicitly tells you just that.
You put this into any software that was well designed and you get two answers: 1) It works. 2) Disregard 1) because the parameters of the simulation exceed the verifed range of this numerical model.
When he said that this was somehow an unprecedented sort of model, so computer models for this were unlikely or unreliable, it had me wondering what he was talking about. This is a completely normal thing to model and get reliable results for. There are no unusual materials or forces involved.
Too True. Don't need to FEA the whole building, but at least run the simulation on this part.
Another great instructive video. I'm not an engineer (I'm an architect) but I love this channel. Even a qualitative visual assessment of the plates in question suggests that they should have an equivalent complexity and scale to one-half of the beam sitting over the ram to compensate for the transferred loads. Keep 'em coming!
Considering the 3 inch hole in the plate, that only leaves an inch and a half on either side. The plate is only as strong as the weakest point.
Yes, and that's the section of the plate with the most strain on it because it's not being well supported by the concrete because of the hole that the rods extend down in. Wild.
And there's horrific vertical shear forces on that concrete above that 80 square inch plate. You've got 300, 000 pounds of force coming down from the building onto that plate through concrete. That's three or four feet away. That's a huge amount of shear force that could cause the concrete to have vertical cracks. I know there's a bucket load of rebar in there but it didn't bother to show it to the diagram. Terrible
"What's your chief engineer called?"
"Ron Hamburger."
"Yeah, I'll pass, thanks."
His plan for stabilizing the building worked. Why make fun of his name?
Former steel detailer, current ironworker (long story), that detail of the plate spanning between those two rods looks like it was a placeholder. I can't imagine that little thing holding the kinds of loads you were saying it needs to hold.
Incompetency squared on this job, just as is the case for a lot of construction endeavors.
Edit: Also, I don't know much about seismic related stuff, but couldn't this vault be pulled off the main foundation?
Since the original fix was meant to have 52 piles and that was reduced down to 18. So that means roughly 3x the force is required to be taken up by each of piles and thus the plates. Hopefully that diagram was drafted for the original plan and simply wasn’t updated when the plate was beefed up significantly. Hopes are good right?
I'm picturing the vault and building separating.
One of the great advances in building technology is being able to design things to a standard of “strong enough”. Which is actually great. It saves materials, gets rid of that forest of columns the skyscrapers of old had, the reasons it’s great are too vast to list. However; in a situation like this, overkill should be the operating principle. Every inch of structure that that plate can cover, it should cover. And if the calculations say 1-1/2” thickness is enough then it should be 2”. A catastrophic failure of that connection severely threatens a cascading collapse.
I 100% agree. Critical components that, if increased in size/capacity, don't negatively affect the budget or physics of the projects I work on get bumped up significantly.
Absolutely. A small steel plate is so cheap in comparison to drilling the huge piles into the ground. Just make the steel plate bigger! And wider and thicker threads for the bolts.
Is this a case of Value Engineering gone Wrong?
@@stevelopez372 At least profit over safety. At this point the only reasonable way out should be to dismantle the building and start from the ground up if ever again at that location. Any decision that says "We will do whatever but take it down" is putting profit over safety.
@Ingvar Hallström Might be some arrogance involved given they don't see the need for an outside engineering firm to review the project as a whole.
I hope I'm just jumping to an unfounded conclusion though.
Great commentary. I'm old enough for the process you describe here to have resonance with that which resulted in the STS-51L Challenger disaster in 1986 -- what Dr Diane Vaughan described as normalisation of deviance. Those small plates transferring the entirety of the forces in the "solution" being implemented to my mind are the equivalent of the rubber O-rings in the joints of the solid rocket boosters of the Space Shuttle system -- a criticality one failure mode: if they fail to do their job, there is no backup and the entire system is prone to destruction. I for one wouldn't want to live in a building that has such a failure scenario, especially where the engineering design appears not to have been fully calculated, or independently checked.
The entire idea of these so called fuses seems crazy. It's not a fuse if it can't be replaced! They needed to come up with a non destructive way of limiting the amount of force they apply to the building.
In theory, the best thing that could happen is more tilting and sinking and then demolition.
Those plates will act like fuses....if one goes under high stress they all are likely to fail in succession. And it would take very little time, maybe seconds.
I am definitely no engineer, but used to work construction in California. We built a wood frame 3 story dormitory building at the University of California Northridge and the earthquake "hold downs" that they used were 1" threaded rods from the first floor to the second, and then stepped down each floor. I think 3/4" and 1/2". 2-1/2" threaded rods seem to be way too small for a building that size compared with 1" on a comparatively simple 3 story building.