Thank you for making these. I lost both my grandparents, Myriam and Arnie Notkin in the collapse, and find solace in the pursuit of answers and analysis.
As a survivor of the building collapsed, I appreciate your deep analysis and providing more insightful information for the people out there. Even today, I’m still experiencing trauma, survivor guilts, and what if’s. I seriously wish this tragic event never happened. RIP to my neighbors and everyone there. My deepest and sincere condolences
We all wish it hadn't happened but I'm glad you were lucky and made it. ♥️ I'm watching this analysis from Sweden in Europe. I've seen most of the analyses.
It’s nice to hear from a survivor. It was meant to be, friend. I haven’t stopped thinking about this collapse since it happened. Such loss you’ve experienced….I’m sure you have the guilt that survivors feel, and it’s normal. You survived while others didn’t and that’s really hard to grasp. Just keep putting one foot in front of the other and take each day as it comes.
I can’t even imagine. This was traumatic for me when I realized the scope of the collapse. The first photos made it appear that just the front of the building had sheared off. Then when I saw what had been there before the collapse, I was horrified. I’m glad you survived and that people are still looking into the cause(s).
Well, you deserve them young man. We may have missed this in your presentation, but would this have inevitably happened without the construction project next door ? And might you speculate how long it may have took?
@@theramseys5296 He does a video going more in depth on the construction of 87 Park and the impact to CTS. He doesn’t go so far as to predict a shelf life of CTS without 87 Park.
Oh absolutely!! If only this channel had been around the first year I took physics 😩🙆🏾. I'd love to see him testify as an expert witness in this or another case - to be able to explain this to (us, and) a jury in just a few minutes is such an important skill.
As one of the people up in the Northeast, freezing, covered with snow - glad you explained how the low temp of 79 deg was enough to initiate the collapse. You are a wonderful presenter, your knowledge and preparation are unmatched. Thank you for making these
@@billj5645 LMAO I'm from the north and we have plenty of buildings made of reinforced concrete despite getting temperatures as low as 0 in the winter so what you said is clearly not true nor did you pay attention to the video where his said the important thing is not the absolute temperature either way but rather the daily change in temperature.
Thank you Josh for keeping the topic alive. Too many times in this nation several months after a tragedy happens everyone forgets about it and it ends up being a missed opportunity. Thanks!!!!
Mr. Samuelson, my heart goes out to you. I will light a candle tonight for your grandparents and the other victims, and all the families of those we lost. Josh is correct in his analytic approach, as it is needed, but thank you for your reminder of the human cost as well. I pray for you all.
I read the article in the Herald and this video helps me understand that better. I've followed the CTS collapse from day 1 and have always felt that there were many contributing factors...not just one thing caused this building to fall. After first hearing of the construction of 87 Park, seeing how close machinery was, how the piledriving would shake CTS, and putting that with things I've learned here and in the Herald, I have no doubt that 87 Park contributed to and/or accelerated existing damage in CTS. If something is already designed, built, and maintained poorly, and then you have this huge excavation and removal of an entire road right next to this key wall, there is no way that could not accelerate or contribute to seen and unseen failures and issues in CTS. I noticed that gravel from the pathway too, when I first saw these pictures. The pathway is basically in the wall so they either damaged the wall itself at some point or they did indeed place and possibly slope this walkway right next to the CTS wall.
But you see, there's no way to definitively prove 87 Park accelerated damage. CTS didn't get engineer's inspections, effectively a 'Structural Bill Of Health', before, during and after construction of 87 Park. And you can't prove that the water on 87 Park's side caused the corrosion, by itself. It's more likely the piss-poor waterproofing of the CTS pool deck did it, over decades. And if you look at the walkway, made up of pavers atop gravel, it's even less likely 87 Park caused anything. The pavers are certainly sloped towards the CTS property, but once the water ran off them and into the gravel, the drainage was vertical. There wasn't a sheet of water pouring behind the retaining wall. No, in my opinion, all the water damage came from the badly-designed CTS pool deck.
I don't think they'll be able to prove it. I'm just saying that that kind of drilling and work next to the wall and foundation of an already badly designed and built structure could only make things worse, if only slightly. The time to pursue legal action for work at 87 Park has passed and should have been addressed at the time. It wasn't so now the lawsuit is grasping at straws so to speak. The suit actually contradicts itself by saying Morabito didnt warn them the building was in danger of collapse so he's partially at fault, but then later it says he did and the CTS board ignored the warnings. Most of what went wrong here is the design and construction. Next would be maintenance and repair or the lack thereof. The 87 Park work, vibrations, and other factors are minor in the shadow of those glaring faults. It managed to stay put together far longer than it should have. A failure in a wall or pool deck or planter box should have never collapsed half a building.
Your commentary has been fascinating to me as a nurse, knowing nothing about building engineering. It is such an interesting field, where you have so much knowledge and responsibility and you are a great teacher, as well. Thank you so much for sharing your knowledge with us.
From how it collapsed on video in stages from the 87 park side first it makes logical sense the slab connecting to the wall gave up first, progressed across the pool deck and then took down the building. This is one of the theories we'd expected to hear about as evidence progressed as it seemed the most likely at the time. Great job in conveying it in such a way anyone is able to understand.
No, actually the pool deck slab was resting ON TOP of the perimeter wall, so even if the rebar failed, gravity would have kept it in place. The pool deck likely failed first, through punching shear, providing the lateral movement to pull the slab off the top of the south wall.
@@johnbergstrom2931in order to allow for the punch through, would the tension have to be relieved by the shearing of the corroded rebar at the retaining wall/slab joint? Regardless, I would agree that inadequate reinforcement at the posts was a major contributing factor. I guess his argument would be that collapse was initiated as the retaining wall/slab joint.
@@cal-native I think think that overstressed part of the pool deck had such corroded rebar, stress cracks (from day one, according to the UW simulations) and spalling to the point where it just plain broke and punched through the columns. The tension theory only works if enough rebar is intact. I don't think it was.
As an engineer myself, what you focus on here makes perfect sense, in so far as the initiating factors, but this does not detract from the two fundamental flaws/points which allowed the progressive collapse of CTS to occur: 1. "Value engineering". Not built to allow for additional tolerances from corrosion of rebar, external vibration, fluctuations in temperature, excessive deflection, delamination of slabs, additional overburden etc. 2. Lack of maintenance to rectify above problems. So on the one hand, it can be argued that CTS was not built to appropriate standards, and on the other, that it was not maintained correctly. Therefore, what finally broke the camel's back can be argued, but had the building been fit for purpose to begin with, there wouldn't have been an initiating event to discuss here.
value engineering... sounds like building "Lite". No tolerances built -in, or, if there are the tolerances would be the bare minimum to comply with a building code. to my mind building codes are formed by lawyers and accountants, not civil engineers, materials engineers, trades-people, or safety engineers. I drive long-haul truck, flatdecks. 3/8" chain is the industry standard. i almost gagged at the price but i use nothing less than 1/2" chain, binders, posts, hooks. this is fairly brawny stuff. at least I know it's more likely to work the first time than what lawyers writing transportation safety laws have concocted.
Thank you for this crystal-clear, respectful explanation. Finding out what happened is vital for many reasons, not only for the bereaved families and litigants, but for planning how to deal with this country’s aging buildings and bridges.
You know it's getting real when the math comes out. One of the things I've learned from this channel is not to underestimate or downplay this sort of event happening...if I ever saw something happening to my building like the pool deck, etc. I'd get out now and ask questions later!
It is truly interesting how building assemblies are literally living & breathing entities that can be seriously affected by seemingly innocuous events. Concrete for all it's strength and utility especially is vulnerable to water damage either through a freeze/thaw cycle or a wetting and drying environment.
This is a nightmare of infrastructure here in Canada, the Gardiner expressway drops spalling concrete all the time, they had to decide whether to fix it or tear it down, they're fixing it.
On the OTHER hand, there's ancient Roman piers, made of that great volcanic-ash concrete of theirs, that have been holding up to Mediterranean saltwater for close to *2,000 years* ... and we've got the series of concrete bridge piers/pillars (originally The Flagler Over-Sea Railroad) that run all the way from Key Largo down to Key West, and NEWEST of them turn 110 years old this year!... still spall-free. It's all in the "mix" and the COVER DEPTH and the COMPETENCE of those placing (and vibrating) the "mix". ;')
It doesn't matter where we are in the world, when things like this happen it touches many of us in some way. Personally I have found your videos very important. Your explanations have made so much sense of it all and have also educated me into a subject (structural engineering) that I knew nothing about. I find your work invaluable and it has opened me up to an ongoing interest in the subject of structures and forces. Thank you.
You make me feel smart when I understand what you’re telling us! I’m mildly dyslexic & math was & is my biggest nightmare. I’m so glad you’re doing follow ups on this disaster. Please continue.
The biggest problem with the pool deck was that it was firmly attached to the building structure. There should have been an expansion gap between the pool deck and the building so that the pool deck could expand and contract as much as it liked, or even collapse, and it wouldn't affect the building itself.
I heard either this guy or someone else explain how not connecting the deck would add significant risks. Something about high speed wind bracing and/or water infiltration.
@@doomedwit1010 those risks would only be there if the builder cut corners. There are plenty of ways to make a building strong enough to handle wind, and make joints waterproof by design, so anyone saying that if you disconnected the slab you would cause problems, was not thinking about designing it that way properly. It just would have cost more, and obviously that's not what they wanted here.
@@doomedwit1010 Adding an expansion joint around the tower has its pros and its cons. It is a prime location for water to get into the underground garage. Joints like this are difficult to seal when the building is new, and much more difficult to maintain when the building gets to be 40 years old, and we see how they had maintenance problems even without this one to deal with. Buildings with basements are normally built where the street level floor is continuous all the way across the site, that way all of the basement walls are braced. You have to brace the basement walls so that dirt outside the building doesn't cave in the walls. If you try to put a big opening in the middle of the street level then it makes it more difficult to brace the basement walls. It can be done but it's more difficult and costs more. Having the tower separate from the basement walls makes it more difficult to carry wind loads down to the foundation, and they have very high wind loads at this site. Again it can be done but is more difficult and costs more money. Overall for all of these reasons, there are very few buildings with basements and outside decks where the outside floor structure is separate from the main building, maybe 1 out of a hundred. I've been doing this a very long time and I'm not sure that can remember even one.
Totally spellbound as all this highly specialist analysis unfolds...love this lecture. Credit to u Josh. Those precious souls lost will never be forgotten.♥️
When this first happened I was wondering how a concrete building could ever collapse and now with all the concepts you have explained I am wondering why more don’t collapse. My wife even gets annoyed because I notice spalling when we are out and about in town now because of your series😂. I would like to request information (or one of your awesome videos) explaining how saturated footings (in particular marine footings like bridges) don’t appear to have PH washing and huge spalling of the reinforcement or how they combat against these effects in design and practice. How do you inspect a pier that is buried in the ground to know if it is still sound?
To be consistent with cooling, I'm going to speculate that this was also a clear night. As most of the cooling effects are from black body radiation, clouds reflect some of that radiation back to earth. Black body radiation is why frost can occur around 38 degrees, as the surface cools lower than the surrounding air temperature. It also allows the air temperature to drop more, as the air is also radiating it's heat to outer space on a clear night. So, the concrete could have gotten around 6 degrees cooler than the air. It does take some time for a thermal mass like concrete to lose all of its heat, and there is likely some thermal gradients between the top of the concrete and middle and lower parts.
"As most of the cooling effects are from black body radiation" - that's incorrect. On Earth black-body radiation is not at all the main factor, it's the good old heat conduction.
@@AlexBesogonov gonna actually your actually, and say for most things on earth convection is the largest mechanism of heat transfer (even if it is just conduction with a moving fluid). That said, radiation is a still a significant factor for objects with poor thermal conductivity in still air.
I am getting along in my years and I am almost 70 years old now. I know this building CTS is almost 40 years old. I can swear to you that my shrinkage has dramatically lost expansion / gained compression over my prior recent years. And yes, I concur, especially over these exact same daily time frames. The laws of physics will prevail, you can only keep expanding and contracting this stuff for just so long without adequate support and maintenance, which leaves you to sometimes be put in a position of grabbing for straws....
I think your videos especially the ones about Champlain towers are very impactful to a lot of people, and are giving a final understanding for all those open questions. I believe that a lot of people will find closure through your series of videos. Thank you so much, even people with no idea about architecture and building integrity could watch and follow your videos easily. 👏👏👏👏👏👏👏👏👏 Really. Thank you for investing so much time and deep dive into this topic 👏👏👏👏
This is such a clear explanation of the significance of radiant heating & cooling and the resulting forces on the structure. I wish engineering school hadn't beat any enjoyment, wonder, and interest out of statics and strengths of materials for me. Thanks for helping rehabilitate the topic for me and presenting this case with such clear physical analogies.
Sometimes the forest is rendered invisible for the trees. A presentation of more complex designs in a somewhat simplified animated matter might add the interest back in to simpler engineering.
👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿 ALL COMMENTERS SHARE THIS IN COMMON: WE REALLY APPRECIATE YOUR BRILLIANT STYLE -- CONTENT AND PRESENTATION VERY CLEAR. WE ALL UNDERSTAND. THIS IS RARE, FOR EXPERTS TO EDUCATE AND INFORM AND MANAGE TO HOLD THE STUDENTS HANGING ON EVERY WORD. AWESOME.
Great work man - keep it up! I'm about a year away from buying a condo in Florida and your videos have opened my eyes as to what to look for in concrete-slab constructed buildings.
I feel like I benefit from this catastrophe every time you post a new presentation- thank you for taking the time and interest in developing this series. an amazing tutorial.
I had no idea the temp differential could be so great in an area that seems to have consistent temperatures. Buildings in the desert must face almost 100 degree swings. Thank you for the knowledge.
This should be a series on Netflix, it's so interesting and educational. I know nothing about construction/engineering, don't even speak perfect english and got hooked since day one.
Don't be concerned about your English. Half the native born population can't speak or write it nearly as well as you do here. As a for how they vote, take a wild guess.
I think these are better than a Netflix documentary... but yes I am hooked and so gratified by how great / smart just regular people can be with public information.
Thank you Josh, for making the lead-up and causes of this horrific tragedy make sense. My sincerest condolences to all those who lost loved ones in the collapse. For the survivors, live your lives and dream your dreams to the fullest extent possible. There is a light.
Remain mystified as to why I continue to find your videos so compelling given that none of this would've interested me, in the least, prior to the collapse of CTS and indulging your explanations. Really appreciate your relatable analogies. Your presentations are reminders of mgmt training sessions back in my corporate days: being given an unfamiliar subject to troubleshoot, testing skillfulness at problem solving. In small, SoCal apt bldg (circa '73) for many years and can now understand why there is loud 'snapping/cracking' sound in ceiling of bedroom (west facing, outer wall but passive morning sun from east side of adjacent bldg), limited to early morn and, fortunately, only on rare days. Still find your red 'marker' difficult to see, especially on dark areas of image.
Great explanation as to what likely occurred. As a former contractor with a great deal of experience in poured concrete structures I thoroughly enjoy your presentations.
Thank you for the best videos about Surfside collapse, explaining it in layman's terms, not making us feel like idiots! Excellent explaination about tight-rope vs wall banding it all together!
Interesting engineering analysis on this tragedy. What is so scary is how many other buildings out there are potentially in the same boat? I remember staying in a hotel in Rapid City South Dakota. It was early Fall so during the day the temps hit 80's but at night it was well below freezing. That building creaked and moaned more then any building I have ever been in late at night or early morning. Over a period of time that amount of thermal expansion and contraction must take its toll on the structure!
While I think the 87th construction might feasibly have (slightly) accelerated the process of corrosion and caused some minor damage, I also think it's obvious enough that the overall rather poor design of CTS and specifically its pool deck and supporting columns meant it was going to fail at some point soon anyway, given the lack of maintenance and the neglect. The level of corrosion needed to have rotted that rebar through didn't happen just since 87th was built.
Defendants' lawyers will find Licensed Professional Engineers who agree with you, AND... (you know how it works)... Plaintiffs' lawyers will find Licensed PEs who will paint 87 Park and their General Contractor (and their GeoTech firm, et al) as Thee Root Of All EE-vil. (Spoiler Alert: win or lose, BOTH law firms gonez ta gets PAID!)
@Z. Michael Gehlke And to add to that, we also know the planned repairs came 4 years later than they should have since the association was more concerned about fixing up the hallways than doing structural repairs. 87 will get a part of the blame, but the association is ultimately to blame.
I have a lot of sympathy for the next door developer. Given CTS's design flaws, it was always going to fail at the connection to the perimeter wall. Having the final straw being next to their work, however, has given them a tough fight to prove that they didn't do any damage in order to avoid liability.
Thank you so much for taking the time to make this video, that even I an "every-day Joe-Six-Pack," fully understands via your video's this was to use my own analogy, a slow cooking crock-pot disaster, involving many ingredients / factor's. When I first heard that they had named the adjoining property in the lawsuit, I thought they were reaching for the star's. Obviously not. Again, thank you Josh. If your someone new to Josh's video's, I encourage to watch his suggested playlist, he carefully lays out the sequence of events (ingredients necessary) that caused this event. I have no vested interest in Josh's video(s,) I'm just someone telling you your not wasting your time watching & learning from them, no matter your skill set(s.) Stay safe Josh. Again a very humble thank you.
You sir are a wonderful teacher. I look forward to all of your videos and learn each time I watch. This is already #3 for this one. Thank you for putting these out there and showing us why you think the way you do.
I’m sitting here laughing at myself because I get about half of what you are saying. My late husband was a simply brilliant engineer and he would be explaining something to me and I’d do my best to follow along. Eventually my eyes began to spin in their sockets, and that was the end of the explanation. Thanks for the lovely memories.
I know nothing about engineering, but I found this video to be fascinating. Thank you for explaining things in a way that even I could understand. Very well done!
I live in Calgary, Alberta. Weather here is crazy, sometimes we have like 20 degree Celsius change in 24 hours period. I wonder what massive stresses these buildings experience when temperature changes so drastically. Love your videos, learn a lot. Thank you
Great analysis Josh, thank you for adding yet another domino to what ultimately resulted in the catastrophic collapse of the Surfside Tower. So many contributing factors to this tragedy.
Thanks Josh, fascinating video really clearly describing the sequence of failures. I am completely hooked on this disaster and feel I have to know the cause. Already hungry for more videos!
Currently a mechanical engineering student at FIU. This is a fascinating analysis of this disaster. I don’t have any structural or civil eng experience but I’m learning a ton. Thanks.
Great throwback to the Karl Wallenda Tallulah gorge crossing. I grew up not far from there and used to hike in the area. I was always fascinated seeing the tower(s) there and wished I had been around to see his crossing. Great job on your analysis too. I'm equally fascinated with this story as well. Keep up the great work!
Another fine installment and explanation. And your analogy about the Jump Rope is excellent. But the thermal expansion/time of day is incredibly insightful. Just a simple Aerospace Engineer here with much time spent building Fighter Aircraft in Israel ... a similar clim to Florida. And back in the day, IAI (Israel Aircraft Industries) hangars had no Climate Control. I can assure you those modest changes in ambient temps have a great effect on "materials". Case in point ... we did a study in July as we were having fitment issues on our Wing Assemblies. The "Jigs" are steel but the structure being drilled/assembled is Aluminum. Keep in mind we're having to hold tolerances of +/- 0.010" and we were getting holes drilled in the relatively "cool" 6 am temps of 26C were drifting off up to 1 INCH by the heat of the day pushing 40C in the heavier sections. I bring this up because as a subset of the "Jump Rope" tension analogy, there is also different rates of expansion/contraction between differing Materials; in my case Steel vs Aluminum. Then add in the degradation of the ReBar via conservation of mass factors in a saline environment and boom ... no more adhesion between the concrete/steel. Just like bending a metal coat hanger back and forth, eventually it'll finally break. 87 Park just sped up the process ... the Builders of Champlain Towers are not without fault either ... I see no evidence of the walls having any significant coating to prevent the ingress of water/salt to prevent the ReBar corrosion ... not good IMHO.
This agrees totally with that harrowing telephone conversation recording we heard on the news. A lady on the phone was looking out of her window at that section of the pool deck whilst talking to someone on the phone, right before the phone call abruptly ended she was describing how the pool deck was collapsing right in front of her eyes. Then sadly of course the call was cut off and i presume the lady became a victim of the tragedy. The fact that she was watching the deck collapse whilst her building was still standing would suggest it failed at that wall first. But it will be interesting to see if the builders of 87 park are blamed for that, from what I have heard and seen, that pool deck had been leaking for many years, it would not surprise me if a great deal of the corrosion was already there long before the 87 park developers started digging.
That was Cassie Stratton, and she died in the collapse. As for the pool deck, there are many documents, and accounts about being badly designed, and maintained like the rest of the building. It was also fixed improperly many times. It had water intrusion from the top, and there was water intrusion from the foundations (the underground garage was 4 feet under sea level, and the building was on the beach) from the very beginning (1981). It was a disaster waiting to happen. Lawsuits are filed for people to (possibly) make money, it doesn't mean they are necessarily based on facts.
You're correct that placing blame for anything solely on 87 Park is likely not going to hold up to scrutiny, but the legal argument will likely move toward acceleration. That had they not gone about construction as they did the residents would've had time to have inspectors assess the true nature of the structure and evacuate and demolish it in a controlled way. At least that's my speculation.
This building was going to fall eventually, so it was not 87 Park's fault totally. However I don't think there is much doubt, that the work done by them, accelerated the process. They are partially responsible for the deaths. If the building had stood for even another 5 years, without the work done by them, some of the residents may have not even have lived there anymore. The lawyers are going to tear them apart in court.
Excellent clear & concise explanation of the CTS situation, Josh. Hey, have you considered investigating the fire and collapse of the gigantic QVC distribution center in Rocky Mount, NC that happened right before Christmas? Thanks for doing this CTS series, well done and highly informative! 👏
Thank you for the analysis you have provided since the collapse. It will probably save lives in the future. Your delivery is so clear and thorough. I enjoy watching your videos even though the subject matter is tragic. I want to add that during the work at 87 Park there were numerous complaints from the residents of CTS describing repercussions they heard and felt in their building. I wish I could remember exactly what I read and cite it. I believe some were emails and some were correspondence from the CTS HOA.
Awesome stuff, as always. Every video of yours is chock full of interesting information, presented in such a easy-to-understand way. I've suggested this channel to a bunch of people. 11:20 - Just for about a minute starting here, the video's framerate gets really choppy. It doesn't really hurt anything in terms of understanding the concepts, but I'm just letting you know in case there's something you may want to deal with on your end.
Thanks, Josh. Even though I am "just" an Electrical Engineer, I follow your explanations very well. My granddaughter (yes, granddaughter) is a graduate student at MIT in Mechanical Engineering but began her studies as an architect at Cornell. I can very easily see her doing this kind of work. She is a brilliant young woman. And yes, I am bragging.
Love these informative videos you’ve been putting out. I found your channel after the collapse because I always am curious about why these things occur and so far you’ve had the best presentation of the facts , especially to a lay person such as myself. Keep up the great work! 👍🏻☺️
I hadn't heard previously that anyone had driven into the garage after the beam and debris had fallen. Even had they seen it, I can't imagine anyone would have thought that the building would collapse. The tourist that filmed the debris from outside the garage-- I think she called emergency services to let them know. Thank you for trying to make sense out of this and hopefully making people aware of signs and steps to take to avoid another collapse.
I did enjoy this video, thank you. I’ve really learned a lot from watching this series. My dad was a civil engineer and he would have loved your analysis of this tragedy! Keep making these videos. Thanks!
My goodness, your analogy of keeping a jump rope taught is brilliant. Thank you. I couldn't read the Miami Herald article because it was behind a paywall, but this video more than made up for it.
Perhaps just a coincidence, but besides being about 5 hours into the post-sunset cooling/contraction cycle, this particular time (1:18AM EDT = Solar Midnight) on this particular day (Full Moon close to Summer Solstice) was a moment of *peak tidal forces,* which of course no ACI code accounts for (because it's NORMALLY too weak to be significant), but when your "camel's back" or "Swiss Cheese model" is already ON the edge, every little "straw" should be looked at... ;')
@@paulloveless4122 The short answer is the moon pulls everything on earth towards itself. This is basic gravity. The slightly longer answer is that since gravity gets smaller with the square of the distance between two objects, and the moon is very far away, the moon pulls on the hotel very, very, very faintly indeed. The amount of thermal contraction estimated in the video would be exert 100,000x to millions of times as much force on any individual part of the building than tidal forces would. Which is not to say those forces are completely negligible, just that the thermal expansion level described means that no matter what the moon was doing, these materials were always going to fail because of their net flaws under the pressure of thermal forces first.
@@paulloveless4122 I'm just saying if you have a supercomputer (and several grad students) at your disposal, you should add tidal (and seismic) activities to your model... for completeness... and to impress certain Euro-weenies who think they're the bees knees when it comes to FEA modeling. Read up on the staggering *weight of the tidal bulge* constantly formed by the sun and moon... on the order of 4x10^16 kilograms!... quite the cosmic "tug o' war"...
@@MajorCaliber It's easy to think of the tidal bulges as huge. And compared to everything humans have done put together they are. But it's also important to remember that 'huge' tidal bulge is part of the ocean which weighs 1.4 × 10^21kg. To put it another way - based on the numbers you and I have quoted, in the fluid oceans, the tides move less than 1/100,000ths of the water. That said, I'm curious where the 4x10^16 figure comes from? I could not locate any such calculation casually and back of the envelope magnitude observations suggest it is probably much too large.
I'm from Massachusetts and laughed when you called us out about how 79 isn't freezing. You read my mind. Your videos are always interesting about the condo.
Thx again Josh and Building Integrity for keeping us abreast with your new research and how this lawsuit may shake out. It makes total sense that CTS collapsed in the night. As always, you are a great storyteller. You make deciphering info easy to understand when it comes to Champlain towers. Thx
Superb analyses regarding the possible initiating sequences of the CT collapse using thermal stresses of concrete as a function of temperature v.s. a jump rope/tight wire cable analogy. Thanks for shedding a lot of light on a very complicated subject in simple layman's terms. 👍
Another big lesson...you are an awesome teacher....keep it simple and use everyday examples we all can relate to like the jumprope you noted. Looking at the pics of the wall that butts to 87 Park post collapse is a massive piece in this overall puzzle. I cant help but wonder if anyone ever took pics of that walkway area as it was being developed. Thanks for the great video as always Josh. Something tells me you have a bunch of angels above rooting for you are you piece things together.
Leaving a comment to feed the youtube algorithm. Because this is another excellent video by Josh, and hoping it gets recommended to more people to see. Great information presented in a very understandable and interesting manner. Thanks Josh.
Hey Josh! Thanks for the breakdown of the slab failure. It's really easy to see with your methods of illustration. Question: have you been following the saga around the Millennium Tower in San Francisco? I fear that might become another learning opportunity.
I've learned so much more since I left school, thanks to people like you who are so smart, that they can translate complex things, like this, into English. Thanks for educating us.
I had never considered Thermal Dynamics in my investigation into the collapse episode. The slab expansion joints (or lack there of.) Should be investigated. Also, how do they put over 18" of pavers and other paving systems on top of one another over a below ground parking garage?
The comparison with the tightrope makes sense. There are so many high rise condo buildings along that strip, I feel an urgent investigation is essential. Different construction companies, working independently of one another and chasing tight deadlines, could well lead to similar issues in many. Thankyou for your excellent explanation.
Nicely done and it is becoming clearer what happened. The security guard mentioned the 3 booms. Although you didn't say so, one imagines that the rebar made a loud noise when it snapped. There was a story that the roofers left early due to rain. And there was a full moon!
Yet another video with a great explanation and a step-by-step walkthrough of your theories and analysis. Thank you for that. I am not a structural engineer as I have stated previously, but really appreciate your thorough insight. Thinking of the analogy of the jump rope and your comments at about 23-24 mins, it seems to me that the strands of fiber in the jump rope are one by one getting weaker and maybe some are frayed or broken. All it would take is one more strand of that rope to give under the force of you (and/or thermal contraction) pulling on it. Then that rope could break completely and chaos to start. Awesome videos. Thanks. Keep up the great work.
Josh Thank you so much for trying your best to help a non-engineer understand what happened in clear precise ways. I would be honest to say if I had chosen to sit through a class in college on these engineering concepts as related to what happened to CTS my mind would have been a jumbled mess. I was advised in High School that I should have taken a class in physics. But I knew that I had struggled with parts of geometry so I felt like a physics class would have been pure torture. I am glad that we have progressed to where we are today in this process. I think most of us here no that lawsuits and assigning blame is going to be a long drawn out process. I just wonder if our attention spans will still be able to "soldier through this 5-7 years down the road.
Excellent video, thanks! I always wondered why the collapse happened at such an odd time. Now I know. Can't wait for the next one! Could you perhaps explain why residents heard clanging (or construction noises) above and below them prior to the collapse? Love your work, thank you!
what the Nirs thought was construction: was likely rebar snapping inside the concrete walls. a survivor (possibly Nir) mentioned seeing a "hand wide" crack suddenly appear running across her wall. that's when she decided to bail. and probably why she survived. suspect that the collapse was really 30-45 minutes from whatever initial point-of-no-return that BI is trying to pinpoint thru these videos, up until the last spectacular 20 seconds that showed up on neighboring buildings' security cameras.
Excellent review, and can't thank you enough for sharing the photographic evidence with the public. After your assessment here, it looks to be dependent upon metal fatigue and how long the rebar would need to be exposed to the elements, and by how MUCH. A few hairline cracks, a few good-sized chunks of concrete missing, or the length of the entire wall-which does look to be exactly what happened. I have to say-the photograph showing 87 Park gravel going UNDER the base of the wall is EXCEPTIONALLY damning. This building was NOT built to withstand heavy construction next to it-and 87 Park developers not only demolished the SMALL hotel they promised to KEEP, but they ALSO illegally altered a public right-of-way, which was designed by the city, and built AROUND-AROUND! In other words, CTS was engineered and designed AROUND having a large mass of concrete next to it (REDUCING MOISTURE IN SURROUNDING SOIL), as well as NEVER having anything constructed right NEXT to it that would involve ANY of the following: A: The use of heavy operation machinery/equipment. B: Soil distruption or removal. C: Foundation drilling and excavation. D: Increase in overall tonnage placed upon surrounding Earth. CHA-CHING! The fact that only the wall facing 87 failed is proof right there. Whomever gave developers permission to alter that public right-of-way is 100% liable for putting public safety at risk-period. Yes-city planning, engineering and code is 100% responsible for allowing it, 87 Park developers are 100% responsible for demanding it.
Excellent analysis Josh. I learned lot from you about regarding the engineering principles that caused this collapse. Unbiased and objective. Keep the clips coming.
Thank you for making these. I lost both my grandparents, Myriam and Arnie Notkin in the collapse, and find solace in the pursuit of answers and analysis.
So very sorry!
I am so sorry. May their memories be a blessing and may you find peace.
My condolences for your loss.
I am so sorry for your loss. 🙏💞
💙😧😞💙
As a survivor of the building collapsed, I appreciate your deep analysis and providing more insightful information for the people out there. Even today, I’m still experiencing trauma, survivor guilts, and what if’s. I seriously wish this tragic event never happened. RIP to my neighbors and everyone there. My deepest and sincere condolences
I feel like you and your family were meant to be saved.
So sorry this happened to you and your neighbors. What a nightmare and don’t forget for a second none of it is your fault. Hang in there -
We all wish it hadn't happened but I'm glad you were lucky and made it. ♥️ I'm watching this analysis from Sweden in Europe. I've seen most of the analyses.
It’s nice to hear from a survivor. It was meant to be, friend. I haven’t stopped thinking about this collapse since it happened. Such loss you’ve experienced….I’m sure you have the guilt that survivors feel, and it’s normal. You survived while others didn’t and that’s really hard to grasp. Just keep putting one foot in front of the other and take each day as it comes.
I can’t even imagine. This was traumatic for me when I realized the scope of the collapse. The first photos made it appear that just the front of the building had sheared off. Then when I saw what had been there before the collapse, I was horrified. I’m glad you survived and that people are still looking into the cause(s).
You'd be a welcome guest at engineering and scientific conferences. Your style is informative, concise and clear, you're a treat to listen to.
Thanks for the kind words!
Well, you deserve them young man. We may have missed this in your presentation, but would this have inevitably happened without the construction project next door ? And might you speculate how long it may have took?
Amen to all that!
@@theramseys5296 He does a video going more in depth on the construction of 87 Park and the impact to CTS. He doesn’t go so far as to predict a shelf life of CTS without 87 Park.
He's not that good
I always feel so smart when I understand what he explains so clearly ….for about 15 min. I wish my younger brain had experienced a teacher like this!
If I had experienced a teacher like this I might’ve gone into engineering instead of finance!
@@SettlingAbyss96 ha and myself the other way round now at 40 I’m getting my education in finance.
Oh absolutely!! If only this channel had been around the first year I took physics 😩🙆🏾. I'd love to see him testify as an expert witness in this or another case - to be able to explain this to (us, and) a jury in just a few minutes is such an important skill.
As one of the people up in the Northeast, freezing, covered with snow - glad you explained how the low temp of 79 deg was enough to initiate the collapse. You are a wonderful presenter, your knowledge and preparation are unmatched. Thank you for making these
Where i live in Phoenix, az .. it can be 115F in daytime and 60F at night, very big change in a 1 day
Lol low temp….. that’s funny
Agreed
That's why we never build reinforced concrete buildings anywhere that it can get below 70 degrees.
@@billj5645 LMAO I'm from the north and we have plenty of buildings made of reinforced concrete despite getting temperatures as low as 0 in the winter so what you said is clearly not true nor did you pay attention to the video where his said the important thing is not the absolute temperature either way but rather the daily change in temperature.
You explain things so clearly that even I can understand.
TY for not putting this tragedy on the shelf like it never happened.
Stay Safe!
Thank you Josh for keeping the topic alive. Too many times in this nation several months after a tragedy happens everyone forgets about it and it ends up being a missed opportunity. Thanks!!!!
@BrandiLynn thank you dear lady, this is very helpful to me.
We're conditioned to be easily distracted and have a short memory so capitalists can keep getting away with killing people.
Mr. Samuelson, my heart goes out to you. I will light a candle tonight for your grandparents and the other victims, and all the families of those we lost. Josh is correct in his analytic approach, as it is needed, but thank you for your reminder of the human cost as well. I pray for you all.
Love the clarity of your presentations
Thank you!
I read the article in the Herald and this video helps me understand that better. I've followed the CTS collapse from day 1 and have always felt that there were many contributing factors...not just one thing caused this building to fall. After first hearing of the construction of 87 Park, seeing how close machinery was, how the piledriving would shake CTS, and putting that with things I've learned here and in the Herald, I have no doubt that 87 Park contributed to and/or accelerated existing damage in CTS. If something is already designed, built, and maintained poorly, and then you have this huge excavation and removal of an entire road right next to this key wall, there is no way that could not accelerate or contribute to seen and unseen failures and issues in CTS. I noticed that gravel from the pathway too, when I first saw these pictures. The pathway is basically in the wall so they either damaged the wall itself at some point or they did indeed place and possibly slope this walkway right next to the CTS wall.
But you see, there's no way to definitively prove 87 Park accelerated damage. CTS didn't get engineer's inspections, effectively a 'Structural Bill Of Health', before, during and after construction of 87 Park. And you can't prove that the water on 87 Park's side caused the corrosion, by itself. It's more likely the piss-poor waterproofing of the CTS pool deck did it, over decades.
And if you look at the walkway, made up of pavers atop gravel, it's even less likely 87 Park caused anything. The pavers are certainly sloped towards the CTS property, but once the water ran off them and into the gravel, the drainage was vertical. There wasn't a sheet of water pouring behind the retaining wall. No, in my opinion, all the water damage came from the badly-designed CTS pool deck.
I don't think they'll be able to prove it. I'm just saying that that kind of drilling and work next to the wall and foundation of an already badly designed and built structure could only make things worse, if only slightly. The time to pursue legal action for work at 87 Park has passed and should have been addressed at the time. It wasn't so now the lawsuit is grasping at straws so to speak. The suit actually contradicts itself by saying Morabito didnt warn them the building was in danger of collapse so he's partially at fault, but then later it says he did and the CTS board ignored the warnings. Most of what went wrong here is the design and construction. Next would be maintenance and repair or the lack thereof. The 87 Park work, vibrations, and other factors are minor in the shadow of those glaring faults. It managed to stay put together far longer than it should have. A failure in a wall or pool deck or planter box should have never collapsed half a building.
Your commentary has been fascinating to me as a nurse, knowing nothing about building engineering. It is such an interesting field, where you have so much knowledge and responsibility and you are a great teacher, as well. Thank you so much for sharing your knowledge with us.
From how it collapsed on video in stages from the 87 park side first it makes logical sense the slab connecting to the wall gave up first, progressed across the pool deck and then took down the building. This is one of the theories we'd expected to hear about as evidence progressed as it seemed the most likely at the time. Great job in conveying it in such a way anyone is able to understand.
No, actually the pool deck slab was resting ON TOP of the perimeter wall, so even if the rebar failed, gravity would have kept it in place. The pool deck likely failed first, through punching shear, providing the lateral movement to pull the slab off the top of the south wall.
@@johnbergstrom2931in order to allow for the punch through, would the tension have to be relieved by the shearing of the corroded rebar at the retaining wall/slab joint? Regardless, I would agree that inadequate reinforcement at the posts was a major contributing factor. I guess his argument would be that collapse was initiated as the retaining wall/slab joint.
@@cal-native I think think that overstressed part of the pool deck had such corroded rebar, stress cracks (from day one, according to the UW simulations) and spalling to the point where it just plain broke and punched through the columns. The tension theory only works if enough rebar is intact. I don't think it was.
As an engineer myself, what you focus on here makes perfect sense, in so far as the initiating factors, but this does not detract from the two fundamental flaws/points which allowed the progressive collapse of CTS to occur:
1. "Value engineering". Not built to allow for additional tolerances from corrosion of rebar, external vibration, fluctuations in temperature, excessive deflection, delamination of slabs, additional overburden etc.
2. Lack of maintenance to rectify above problems.
So on the one hand, it can be argued that CTS was not built to appropriate standards, and on the other, that it was not maintained correctly. Therefore, what finally broke the camel's back can be argued, but had the building been fit for purpose to begin with, there wouldn't have been an initiating event to discuss here.
value engineering... sounds like building "Lite". No tolerances built -in, or, if there are the tolerances would be the bare minimum to comply with a building code.
to my mind building codes are formed by lawyers and accountants, not civil engineers, materials engineers, trades-people, or safety engineers.
I drive long-haul truck, flatdecks. 3/8" chain is the industry standard. i almost gagged at the price but i use nothing less than 1/2" chain, binders, posts, hooks. this is fairly brawny stuff. at least I know it's more likely to work the first time than what lawyers writing transportation safety laws have concocted.
Thank you for this crystal-clear, respectful explanation. Finding out what happened is vital for many reasons, not only for the bereaved families and litigants, but for planning how to deal with this country’s aging buildings and bridges.
You know it's getting real when the math comes out.
One of the things I've learned from this channel is not to underestimate or downplay this sort of event happening...if I ever saw something happening to my building like the pool deck, etc. I'd get out now and ask questions later!
It is truly interesting how building assemblies are literally living & breathing entities that can be seriously affected by seemingly innocuous events. Concrete for all it's strength and utility especially is vulnerable to water damage either through a freeze/thaw cycle or a wetting and drying environment.
This is a nightmare of infrastructure here in Canada, the Gardiner expressway drops spalling concrete all the time, they had to decide whether to fix it or tear it down, they're fixing it.
On the OTHER hand, there's ancient Roman piers, made of that great volcanic-ash concrete of theirs, that have been holding up to Mediterranean saltwater for close to *2,000 years* ... and we've got the series of concrete bridge piers/pillars (originally The Flagler Over-Sea Railroad) that run all the way from Key Largo down to Key West, and NEWEST of them turn 110 years old this year!... still spall-free. It's all in the "mix" and the COVER DEPTH and the COMPETENCE of those placing (and vibrating) the "mix". ;')
It doesn't matter where we are in the world, when things like this happen it touches many of us in some way. Personally I have found your videos very important. Your explanations have made so much sense of it all and have also educated me into a subject (structural engineering) that I knew nothing about. I find your work invaluable and it has opened me up to an ongoing interest in the subject of structures and forces. Thank you.
Thank you so much Sue.
You make me feel smart when I understand what you’re telling us! I’m mildly dyslexic & math was & is my biggest nightmare. I’m so glad you’re doing follow ups on this disaster. Please continue.
The biggest problem with the pool deck was that it was firmly attached to the building structure. There should have been an expansion gap between the pool deck and the building so that the pool deck could expand and contract as much as it liked, or even collapse, and it wouldn't affect the building itself.
It would have cost too much! Extra columns and beams around the perimeter of the deck.
I heard either this guy or someone else explain how not connecting the deck would add significant risks. Something about high speed wind bracing and/or water infiltration.
@@doomedwit1010 those risks would only be there if the builder cut corners. There are plenty of ways to make a building strong enough to handle wind, and make joints waterproof by design, so anyone saying that if you disconnected the slab you would cause problems, was not thinking about designing it that way properly.
It just would have cost more, and obviously that's not what they wanted here.
Yup. It's called "value engineering". Cutting cost along with tolerances.
@@doomedwit1010 Adding an expansion joint around the tower has its pros and its cons. It is a prime location for water to get into the underground garage. Joints like this are difficult to seal when the building is new, and much more difficult to maintain when the building gets to be 40 years old, and we see how they had maintenance problems even without this one to deal with. Buildings with basements are normally built where the street level floor is continuous all the way across the site, that way all of the basement walls are braced. You have to brace the basement walls so that dirt outside the building doesn't cave in the walls. If you try to put a big opening in the middle of the street level then it makes it more difficult to brace the basement walls. It can be done but it's more difficult and costs more. Having the tower separate from the basement walls makes it more difficult to carry wind loads down to the foundation, and they have very high wind loads at this site. Again it can be done but is more difficult and costs more money. Overall for all of these reasons, there are very few buildings with basements and outside decks where the outside floor structure is separate from the main building, maybe 1 out of a hundred. I've been doing this a very long time and I'm not sure that can remember even one.
I love how you explain tensioning and deflection. Simple and elegant.
You would make an amazing professor. Thank you again for explaining in such clear detail.
Totally spellbound as all this highly specialist analysis unfolds...love this lecture. Credit to u Josh. Those precious souls lost will never be forgotten.♥️
When this first happened I was wondering how a concrete building could ever collapse and now with all the concepts you have explained I am wondering why more don’t collapse. My wife even gets annoyed because I notice spalling when we are out and about in town now because of your series😂.
I would like to request information (or one of your awesome videos) explaining how saturated footings (in particular marine footings like bridges) don’t appear to have PH washing and huge spalling of the reinforcement or how they combat against these effects in design and practice. How do you inspect a pier that is buried in the ground to know if it is still sound?
To be consistent with cooling, I'm going to speculate that this was also a clear night. As most of the cooling effects are from black body radiation, clouds reflect some of that radiation back to earth. Black body radiation is why frost can occur around 38 degrees, as the surface cools lower than the surrounding air temperature. It also allows the air temperature to drop more, as the air is also radiating it's heat to outer space on a clear night. So, the concrete could have gotten around 6 degrees cooler than the air. It does take some time for a thermal mass like concrete to lose all of its heat, and there is likely some thermal gradients between the top of the concrete and middle and lower parts.
That also helps makes sense why my bmw beeps and flashes the temp warning around 37/38°F alerting you to the possibility of ice or slick conditions.
"As most of the cooling effects are from black body radiation" - that's incorrect. On Earth black-body radiation is not at all the main factor, it's the good old heat conduction.
@@AlexBesogonov gonna actually your actually, and say for most things on earth convection is the largest mechanism of heat transfer (even if it is just conduction with a moving fluid). That said, radiation is a still a significant factor for objects with poor thermal conductivity in still air.
Objects with poor thermal conductivity to earth or other heat sinks, such as an ice cube tray of water sitting on an insulating layer under open sky.
I am getting along in my years and I am almost 70 years old now. I know this building CTS is almost 40 years old. I can swear to you that my shrinkage has dramatically lost expansion / gained compression over my prior recent years.
And yes, I concur, especially over these exact same daily time frames.
The laws of physics will prevail, you can only keep expanding and contracting this stuff for just so long without adequate support and maintenance, which leaves you to sometimes be put in a position of grabbing for straws....
Not far behind you sir. lols.
You"re awesome. Wish you would post more forensics investigations as the subject is fascinating.
Totally is
Thank you for the obvious hard work and editing in putting these together.
I think your videos especially the ones about Champlain towers are very impactful to a lot of people, and are giving a final understanding for all those open questions. I believe that a lot of people will find closure through your series of videos. Thank you so much, even people with no idea about architecture and building integrity could watch and follow your videos easily. 👏👏👏👏👏👏👏👏👏 Really. Thank you for investing so much time and deep dive into this topic 👏👏👏👏
This is such a clear explanation of the significance of radiant heating & cooling and the resulting forces on the structure. I wish engineering school hadn't beat any enjoyment, wonder, and interest out of statics and strengths of materials for me. Thanks for helping rehabilitate the topic for me and presenting this case with such clear physical analogies.
Sometimes the forest is rendered invisible for the trees. A presentation of more complex designs in a somewhat simplified animated matter might add the interest back in to simpler engineering.
I'm a student of building and I love your presentations! Thanks.
Interesting update, Josh! Thank you for continuing to pursue this investigation.
👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿👏🏿
ALL COMMENTERS SHARE THIS IN COMMON: WE REALLY APPRECIATE YOUR BRILLIANT STYLE --
CONTENT AND PRESENTATION VERY CLEAR. WE ALL UNDERSTAND. THIS IS RARE, FOR EXPERTS TO EDUCATE AND INFORM AND MANAGE TO HOLD THE STUDENTS HANGING ON EVERY WORD.
AWESOME.
Thank you Susana!
Great work man - keep it up! I'm about a year away from buying a condo in Florida and your videos have opened my eyes as to what to look for in concrete-slab constructed buildings.
I am a retired Mechanical Engineer. This is very interesting and well explained. Two thumbs up. Thank you.
I feel like I benefit from this catastrophe every time you post a new presentation- thank you for taking the time and interest in developing this series. an amazing tutorial.
I had no idea the temp differential could be so great in an area that seems to have consistent temperatures. Buildings in the desert must face almost 100 degree swings. Thank you for the knowledge.
This should be a series on Netflix, it's so interesting and educational. I know nothing about construction/engineering, don't even speak perfect english and got hooked since day one.
Don't be concerned about your English. Half the native born population can't speak or write it nearly as well as you do here. As a for how they vote, take a wild guess.
Who needs Netflix when you have TH-cam for free?
I think these are better than a Netflix documentary... but yes I am hooked and so gratified by how great / smart just regular people can be with public information.
Thank you Josh, for making the lead-up and causes of this horrific tragedy make sense. My sincerest condolences to all those who lost loved ones in the collapse. For the survivors, live your lives and dream your dreams to the fullest extent possible. There is a light.
Remain mystified as to why I continue to find your videos so compelling given that none of this would've interested me, in the least, prior to the collapse of CTS and indulging your explanations. Really appreciate your relatable analogies. Your presentations are reminders of mgmt training sessions back in my corporate days: being given an unfamiliar subject to troubleshoot, testing skillfulness at problem solving.
In small, SoCal apt bldg (circa '73) for many years and can now understand why there is loud 'snapping/cracking' sound in ceiling of bedroom (west facing, outer wall but passive morning sun from east side of adjacent bldg), limited to early morn and, fortunately, only on rare days. Still find your red 'marker' difficult to see, especially on dark areas of image.
Great explanation as to what likely occurred. As a former contractor with a great deal of experience in poured concrete structures I thoroughly enjoy your presentations.
This was a great video !! You made it so easy to understand!!! Please continue to update us !!
Thank you for the best videos about Surfside collapse, explaining it in layman's terms, not making us feel like idiots! Excellent explaination about tight-rope vs wall banding it all together!
Interesting engineering analysis on this tragedy. What is so scary is how many other buildings out there are potentially in the same boat? I remember staying in a hotel in Rapid City South Dakota. It was early Fall so during the day the temps hit 80's but at night it was well below freezing. That building creaked and moaned more then any building I have ever been in late at night or early morning. Over a period of time that amount of thermal expansion and contraction must take its toll on the structure!
You’ve provided the best explanation of this disaster in a clear concise way.
Thanks
Love the way you drill down on the existing evidence, using your vast knowledge of engineering principles.
While I think the 87th construction might feasibly have (slightly) accelerated the process of corrosion and caused some minor damage, I also think it's obvious enough that the overall rather poor design of CTS and specifically its pool deck and supporting columns meant it was going to fail at some point soon anyway, given the lack of maintenance and the neglect. The level of corrosion needed to have rotted that rebar through didn't happen just since 87th was built.
Defendants' lawyers will find Licensed Professional Engineers who agree with you, AND... (you know how it works)... Plaintiffs' lawyers will find Licensed PEs who will paint 87 Park and their General Contractor (and their GeoTech firm, et al) as Thee Root Of All EE-vil. (Spoiler Alert: win or lose, BOTH law firms gonez ta gets PAID!)
I was thinking the same thing. The time it takes for corrosion of rebar at that scale seems to point to it corroding prior to 87 park.
@@MajorCaliber , you will know it is a cold day because the lawyers have their hands in their own pockets...
@Z. Michael Gehlke And to add to that, we also know the planned repairs came 4 years later than they should have since the association was more concerned about fixing up the hallways than doing structural repairs.
87 will get a part of the blame, but the association is ultimately to blame.
I have a lot of sympathy for the next door developer. Given CTS's design flaws, it was always going to fail at the connection to the perimeter wall. Having the final straw being next to their work, however, has given them a tough fight to prove that they didn't do any damage in order to avoid liability.
You're low key my favorite TH-camr right now. Yes, I hit the bell! Thanks for the professionalism and sharing your expertise!
Wow! Thanks so much!
JP understands his subject and his audience so well. Superb analysis and communication.
The expansion joint relieving tension along the east-west direction seems right. The pool area not collapsing supports it. 👍🏻
Thank you so much for taking the time to make this video, that even I an "every-day Joe-Six-Pack," fully understands via your video's this was to use my own analogy, a slow cooking crock-pot disaster, involving many ingredients / factor's. When I first heard that they had named the adjoining property in the lawsuit, I thought they were reaching for the star's. Obviously not. Again, thank you Josh. If your someone new to Josh's video's, I encourage to watch his suggested playlist, he carefully lays out the sequence of events (ingredients necessary) that caused this event. I have no vested interest in Josh's video(s,) I'm just someone telling you your not wasting your time watching & learning from them, no matter your skill set(s.) Stay safe Josh. Again a very humble thank you.
Wow! Thank you so much! This means a ton to me.
Incredible how well all your videos are put together that someone with no knowledge in construction can understand everything
I'd second that. lols.
Your ability to explain very complicated concepts to those of us who are not engineers is amazing. Thank you.
You sir are a wonderful teacher. I look forward to all of your videos and learn each time I watch. This is already #3 for this one. Thank you for putting these out there and showing us why you think the way you do.
I’m sitting here laughing at myself because I get about half of what you are saying. My late husband was a simply brilliant engineer and he would be explaining something to me and I’d do my best to follow along. Eventually my eyes began to spin in their sockets, and that was the end of the explanation. Thanks for the lovely memories.
Really nice explanations. I haven't considered a lot of these kinds of forces since taking statics in college. I've forgotten a lot since those days.
I know nothing about engineering, but I found this video to be fascinating. Thank you for explaining things in a way that even I could understand. Very well done!
I live in Calgary, Alberta. Weather here is crazy, sometimes we have like 20 degree Celsius change in 24 hours period. I wonder what massive stresses these buildings experience when temperature changes so drastically. Love your videos, learn a lot. Thank you
Great analysis Josh, thank you for adding yet another domino to what ultimately resulted in the catastrophic collapse of the Surfside Tower. So many contributing factors to this tragedy.
Thanks Josh, fascinating video really clearly describing the sequence of failures. I am completely hooked on this disaster and feel I have to know the cause. Already hungry for more videos!
Currently a mechanical engineering student at FIU. This is a fascinating analysis of this disaster. I don’t have any structural or civil eng experience but I’m learning a ton. Thanks.
Great throwback to the Karl Wallenda Tallulah gorge crossing. I grew up not far from there and used to hike in the area. I was always fascinated seeing the tower(s) there and wished I had been around to see his crossing. Great job on your analysis too. I'm equally fascinated with this story as well. Keep up the great work!
Another fine installment and explanation. And your analogy about the Jump Rope is excellent. But the thermal expansion/time of day is incredibly insightful. Just a simple Aerospace Engineer here with much time spent building Fighter Aircraft in Israel ... a similar clim to Florida. And back in the day, IAI (Israel Aircraft Industries) hangars had no Climate Control. I can assure you those modest changes in ambient temps have a great effect on "materials". Case in point ... we did a study in July as we were having fitment issues on our Wing Assemblies. The "Jigs" are steel but the structure being drilled/assembled is Aluminum. Keep in mind we're having to hold tolerances of +/- 0.010" and we were getting holes drilled in the relatively "cool" 6 am temps of 26C were drifting off up to 1 INCH by the heat of the day pushing 40C in the heavier sections.
I bring this up because as a subset of the "Jump Rope" tension analogy, there is also different rates of expansion/contraction between differing Materials; in my case Steel vs Aluminum. Then add in the degradation of the ReBar via conservation of mass factors in a saline environment and boom ... no more adhesion between the concrete/steel. Just like bending a metal coat hanger back and forth, eventually it'll finally break. 87 Park just sped up the process ... the Builders of Champlain Towers are not without fault either ... I see no evidence of the walls having any significant coating to prevent the ingress of water/salt to prevent the ReBar corrosion ... not good IMHO.
This agrees totally with that harrowing telephone conversation recording we heard on the news. A lady on the phone was looking out of her window at that section of the pool deck whilst talking to someone on the phone, right before the phone call abruptly ended she was describing how the pool deck was collapsing right in front of her eyes. Then sadly of course the call was cut off and i presume the lady became a victim of the tragedy. The fact that she was watching the deck collapse whilst her building was still standing would suggest it failed at that wall first.
But it will be interesting to see if the builders of 87 park are blamed for that, from what I have heard and seen, that pool deck had been leaking for many years, it would not surprise me if a great deal of the corrosion was already there long before the 87 park developers started digging.
That was Cassie Stratton, and she died in the collapse. As for the pool deck, there are many documents, and accounts about being badly designed, and maintained like the rest of the building. It was also fixed improperly many times. It had water intrusion from the top, and there was water intrusion from the foundations (the underground garage was 4 feet under sea level, and the building was on the beach) from the very beginning (1981). It was a disaster waiting to happen. Lawsuits are filed for people to (possibly) make money, it doesn't mean they are necessarily based on facts.
That rebar did not corrode through in the four years since 87 Park was built. This was a long standing issue.
You're correct that placing blame for anything solely on 87 Park is likely not going to hold up to scrutiny, but the legal argument will likely move toward acceleration. That had they not gone about construction as they did the residents would've had time to have inspectors assess the true nature of the structure and evacuate and demolish it in a controlled way. At least that's my speculation.
This building was going to fall eventually, so it was not 87 Park's fault totally. However I don't think there is much doubt, that the work done by them, accelerated the process. They are partially responsible for the deaths. If the building had stood for even another 5 years, without the work done by them, some of the residents may have not even have lived there anymore. The lawyers are going to tear them apart in court.
@@golfmaniac Other residents would have lived there. What is your point? People were still gonna die.
Great stuff as always, Josh - well-explained and for the layman it gives a visual of the forces at work. Thanks!
Excellent clear & concise explanation of the CTS situation, Josh. Hey, have you considered investigating the fire and collapse of the gigantic QVC distribution center in Rocky Mount, NC that happened right before Christmas? Thanks for doing this CTS series, well done and highly informative! 👏
Thank you for the analysis you have provided since the collapse. It will probably save lives in the future. Your delivery is so clear and thorough. I enjoy watching your videos even though the subject matter is tragic.
I want to add that during the work at 87 Park there were numerous complaints from the residents of CTS describing repercussions they heard and felt in their building. I wish I could remember exactly what I read and cite it. I believe some were emails and some were correspondence from the CTS HOA.
Awesome stuff, as always. Every video of yours is chock full of interesting information, presented in such a easy-to-understand way. I've suggested this channel to a bunch of people.
11:20 - Just for about a minute starting here, the video's framerate gets really choppy. It doesn't really hurt anything in terms of understanding the concepts, but I'm just letting you know in case there's something you may want to deal with on your end.
Thanks, Josh. Even though I am "just" an Electrical Engineer, I follow your explanations very well. My granddaughter (yes, granddaughter) is a graduate student at MIT in Mechanical Engineering but began her studies as an architect at Cornell. I can very easily see her doing this kind of work. She is a brilliant young woman. And yes, I am bragging.
Love these informative videos you’ve been putting out. I found your channel after the collapse because I always am curious about why these things occur and so far you’ve had the best presentation of the facts , especially to a lay person such as myself. Keep up the great work! 👍🏻☺️
I hadn't heard previously that anyone had driven into the garage after the beam and debris had fallen. Even had they seen it, I can't imagine anyone would have thought that the building would collapse. The tourist that filmed the debris from outside the garage-- I think she called emergency services to let them know. Thank you for trying to make sense out of this and hopefully making people aware of signs and steps to take to avoid another collapse.
They drove before.
I did enjoy this video, thank you. I’ve really learned a lot from watching this series. My dad was a civil engineer and he would have loved your analysis of this tragedy! Keep making these videos. Thanks!
My goodness, your analogy of keeping a jump rope taught is brilliant. Thank you. I couldn't read the Miami Herald article because it was behind a paywall, but this video more than made up for it.
Thank you so much for the updates. I do very much appreciate how you update and change and move with new information to study!
Thank you for making a complex tragedy understandable to those of us without engineering knowledge. May those that lost their lives Rest In Peace.
Perhaps just a coincidence, but besides being about 5 hours into the post-sunset cooling/contraction cycle, this particular time (1:18AM EDT = Solar Midnight) on this particular day (Full Moon close to Summer Solstice) was a moment of *peak tidal forces,* which of course no ACI code accounts for (because it's NORMALLY too weak to be significant), but when your "camel's back" or "Swiss Cheese model" is already ON the edge, every little "straw" should be looked at... ;')
Can someone knowledgeable comment on this please? OP: Will you explain to me how tidal forces affect the structure?
@@paulloveless4122 The short answer is the moon pulls everything on earth towards itself. This is basic gravity. The slightly longer answer is that since gravity gets smaller with the square of the distance between two objects, and the moon is very far away, the moon pulls on the hotel very, very, very faintly indeed. The amount of thermal contraction estimated in the video would be exert 100,000x to millions of times as much force on any individual part of the building than tidal forces would. Which is not to say those forces are completely negligible, just that the thermal expansion level described means that no matter what the moon was doing, these materials were always going to fail because of their net flaws under the pressure of thermal forces first.
@@paulloveless4122 I'm just saying if you have a supercomputer (and several grad students) at your disposal, you should add tidal (and seismic) activities to your model... for completeness... and to impress certain Euro-weenies who think they're the bees knees when it comes to FEA modeling. Read up on the staggering *weight of the tidal bulge* constantly formed by the sun and moon... on the order of 4x10^16 kilograms!... quite the cosmic "tug o' war"...
@@paulloveless4122 I think he's just pulling your leg with the tidal forces...
@@MajorCaliber It's easy to think of the tidal bulges as huge. And compared to everything humans have done put together they are. But it's also important to remember that 'huge' tidal bulge is part of the ocean which weighs 1.4 × 10^21kg. To put it another way - based on the numbers you and I have quoted, in the fluid oceans, the tides move less than 1/100,000ths of the water. That said, I'm curious where the 4x10^16 figure comes from? I could not locate any such calculation casually and back of the envelope magnitude observations suggest it is probably much too large.
I'm from Massachusetts and laughed when you called us out about how 79 isn't freezing. You read my mind. Your videos are always interesting about the condo.
Thx again Josh and Building Integrity for keeping us abreast with your new research and how this lawsuit may shake out. It makes total sense that CTS collapsed in the night. As always, you are a great storyteller. You make deciphering info easy to understand when it comes to Champlain towers. Thx
Your analysis of this collapse is far and away the most concise and plausible scenario I have seen here on TH-cam. Well done Sir!
You do such a great job of presenting this information.
Superb analyses regarding the possible initiating sequences of the CT collapse using thermal stresses of concrete as a function of temperature v.s. a jump rope/tight wire cable analogy. Thanks for shedding a lot of light on a very complicated subject in simple layman's terms. 👍
Another big lesson...you are an awesome teacher....keep it simple and use everyday examples we all can relate to like the jumprope you noted. Looking at the pics of the wall that butts to 87 Park post collapse is a massive piece in this overall puzzle. I cant help but wonder if anyone ever took pics of that walkway area as it was being developed.
Thanks for the great video as always Josh. Something tells me you have a bunch of angels above rooting for you are you piece things together.
Leaving a comment to feed the youtube algorithm. Because this is another excellent video by Josh, and hoping it gets recommended to more people to see. Great information presented in a very understandable and interesting manner. Thanks Josh.
Hey Josh! Thanks for the breakdown of the slab failure. It's really easy to see with your methods of illustration. Question: have you been following the saga around the Millennium Tower in San Francisco? I fear that might become another learning opportunity.
Fantastic analysis as always, thank you Josh.
You explain the process so well, wowza! Although I know that the design and structural elements are way complicated, what you say makes total sense.
Thanks Raja!
Honestly I just like listening to you explain things.
Great thanks for all of your coverage, it really makes the whole thing understandable without skimping on the engineering science!
-Matt
I've learned so much more since I left school, thanks to people like you who are so smart, that they can translate complex things, like this, into English. Thanks for educating us.
Incredible! Great job explaining to my non mathematical brain. It really makes me wonder how many under-engineered buildings are at risk?!?
Thank you. I could spew more but I hope you already understand how deeply some of us care about this issue.
I had never considered Thermal Dynamics in my investigation into the collapse episode. The slab expansion joints (or lack there of.) Should be investigated. Also, how do they put over 18" of pavers and other paving systems on top of one another over a below ground parking garage?
The comparison with the tightrope makes sense. There are so many high rise condo buildings along that strip, I feel an urgent investigation is essential. Different construction companies, working independently of one another and chasing tight deadlines, could well lead to similar issues in many. Thankyou for your excellent explanation.
Nicely done and it is becoming clearer what happened. The security guard mentioned the 3 booms. Although you didn't say so, one imagines that the rebar made a loud noise when it snapped. There was a story that the roofers left early due to rain. And there was a full moon!
Yet another video with a great explanation and a step-by-step walkthrough of your theories and analysis. Thank you for that. I am not a structural engineer as I have stated previously, but really appreciate your thorough insight.
Thinking of the analogy of the jump rope and your comments at about 23-24 mins, it seems to me that the strands of fiber in the jump rope are one by one getting weaker and maybe some are frayed or broken. All it would take is one more strand of that rope to give under the force of you (and/or thermal contraction) pulling on it. Then that rope could break completely and chaos to start.
Awesome videos. Thanks. Keep up the great work.
Fascinating. There WAS a street there with drainage, then it was gone.
Josh Thank you so much for trying your best to help a non-engineer understand what happened in clear precise ways. I would be honest to say if I had chosen to sit through a class in college on these engineering concepts as related to what happened to CTS my mind would have been a jumbled mess. I was advised in High School that I should have taken a class in physics. But I knew that I had struggled with parts of geometry so I felt like a physics class would have been pure torture.
I am glad that we have progressed to where we are today in this process. I think most of us here no that lawsuits and assigning blame is going to be a long drawn out process. I just wonder if our attention spans will still be able to "soldier through this 5-7 years down the road.
Excellent video, thanks! I always wondered why the collapse happened at such an odd time. Now I know. Can't wait for the next one! Could you perhaps explain why residents heard clanging (or construction noises) above and below them prior to the collapse? Love your work, thank you!
Exactly my question. Nir family thought there was construction above them.
what the Nirs thought was construction: was likely rebar snapping inside the concrete walls.
a survivor (possibly Nir) mentioned seeing a "hand wide" crack suddenly appear running across her wall. that's when she decided to bail. and probably why she survived.
suspect that the collapse was really 30-45 minutes from whatever initial point-of-no-return that BI is trying to pinpoint thru these videos, up until the last spectacular 20 seconds that showed up on neighboring buildings' security cameras.
You are very good explaining and illustrating the complex topic of civil engineering to a lay audience. Thank you.
Excellent review, and can't thank you enough for sharing the photographic evidence with the public. After your assessment here, it looks to be dependent upon metal fatigue and how long the rebar would need to be exposed to the elements, and by how MUCH. A few hairline cracks, a few good-sized chunks of concrete missing, or the length of the entire wall-which does look to be exactly what happened. I have to say-the photograph showing 87 Park gravel going UNDER the base of the wall is EXCEPTIONALLY damning. This building was NOT built to withstand heavy construction next to it-and 87 Park developers not only demolished the SMALL hotel they promised to KEEP, but they ALSO illegally altered a public right-of-way, which was designed by the city, and built AROUND-AROUND! In other words, CTS was engineered and designed AROUND having a large mass of concrete next to it (REDUCING MOISTURE IN SURROUNDING SOIL), as well as NEVER having anything constructed right NEXT to it that would involve ANY of the following:
A: The use of heavy operation machinery/equipment.
B: Soil distruption or removal.
C: Foundation drilling and excavation.
D: Increase in overall tonnage placed upon surrounding Earth.
CHA-CHING! The fact that only the wall facing 87 failed is proof right there. Whomever gave developers permission to alter that public right-of-way is 100% liable for putting public safety at risk-period. Yes-city planning, engineering and code is 100% responsible for allowing it, 87 Park developers are 100% responsible for demanding it.
There you go with your "100%" shit again...
Excellent analysis Josh. I learned lot from you about regarding the engineering principles that caused this collapse. Unbiased and objective. Keep the clips coming.