In this video we learn about non-uniform distribution of shear forces and both how they spared the West wing of Champlain Towers South and how they contributed to the progressive collapse of the East wing.
Engineering is not my field, but your explanations are easy to grasp. If you’re not a teacher-trade school, college, job training-you should be. You’re a natural. Thanks for helping us understand.
This is a prime motivation for me. I know I may not create meaningful change in the current fields of construction and engineering in my lifetime, but if I can help the next generation, I will die happy.
@@BuildingIntegrity There were times when collapse was not an option. These are times of Egyptian pyramids construction. They are still with us 3500-4000 years later. The rest of humans history is buildings construction optimization for cost. Sometimes this optimization cause collapse. Optimization level of Structural Engineering shall either do step back or find that particular construction/materials error that violated optimization rules of Structural Engineering. IMHO this building had to have more concrete walls between columns, so that they prevent swing of the building part that contains only columns and slabs. Buyers want more open space without walls. But this weakens the building structure against swing (due to wind load in Florida) and consequent cracks where load became excessive for materials. In the collapse video collapsed part 3 was swinging like jelly. This caused its collapse due to exponentially increasing number of cracks appeared those several seconds through all joints between columns and slabs. Such building shall either be built with steel columns or shall be built with lot of concrete walls inside.
As a retired elementary teacher, I’ve studied and practiced teaching methodologies my entire adult life. You, sir, are a gifted teacher. You’ve taught me more than I thought I ever wanted to know about big building structures.
His ability to effectively and efficiently communicate is masterful. This could be called "Basic Engineering for Dummies," because even I can understand what he's talking about. This is very well-done.
You are absolutely correct! I’m a current elementary special-education teacher, and his ability to teach these engineering concepts is exceptional. I always comment on every single video of his that he should be a professor in a college of civil engineering. The college would be so lucky to have him!
@@jamieleightee *A simple exercise:* For _each_ 100 pounds of _horizontal_ component of wind force directed against a north wall, each of the east and west outside walls that are at right angles to it takes up 50 pounds of force. If a third interior wall is added parallel to the east and west walls then each wall will take up 33.3 pounds of force. The floors that also transmit this horizontal component of force to the outside walls prevent concave deflection of the north wall. Horizontal force transmitted by the floors that is taken up by the footings of the columns and rear wall may be ignored for this analysis. Is a third interior wall of solid concrete required? (Referred to in some discussions as a shear wall). After calculating the force that the east and west walls must accommodate it is a matter of design choice. It is likely that the minimum thickness and strength of the east and west walls already greatly exceeds the horizontal force that these must hold back. Thus, for each 50 pounds exerted horizontally, the walls as a result of their strength to function as a wall supporting the vertical downward load from weight, are already capable of sustaining a horizontal component several times that amount, which is why the contribution of the footings was ignored. An interior wall of solid concrete that is not connected by rebar to the adjacent part of the building is in effect an _exterior_ wall to which an abutting structure has been added that encloses it making the whole thing appear to be a single building. Pre-construction-sales enabled raising capital for a much larger structure. The reason behind this two-phase design is _finance,_ not engineering.
Josh - from the bottom of my heart, thank you so much for taking time to do these videos. Many people purport to do what you're doing, but you're one of the very few who is more concerned with delivering truthful information than he is about gaming the RU-vid algorithm. It's really amazing to me what you do.
No, he isn't. Engineering involves a lot of math and physics, not entertainment videos. They're nice to watch and get the general idea, but you're still light years away from being an engineer after watching it
Where I live they are in the process of a 400 apartment high rise. When I drive by it I am looking at it more closely. I am thinking how are they building it. Are they pouring concrete on one floor before moving to the next. I look at the rebar sticking up to see how it is woven together. I never would have been interested in this before watching your videos on the condo collapse in FL. You explain things so easily to those of us who don't have an engineering background. I find this totally fascinating. THANK YOU for taking time out of your day to explain various aspects of the collapse in your videos.
I don't like rebar at this point. I'm going to lean towards the old I beam stuff that's still standing. The Empire state got smacked twice by military planes in the 40s. Still standing and the repairs are still holding 70 years later. I beams it is.
Honestly, my eyes have been opened, aware of details. Just walking inside a 4 story parking garage has me noticing column widths. I’m just a little old retired lady.
@@windsofmarchjourneyperrytr2823 Steel-skeleton (I-beam) structures are great for OFFICE buildings, but NOT for residential units, because... they SWAY in the wind! Peeps can handle that when working, but when relaxing or SLEEPING?... nay way. (That said, when you're *right on the beach,* you still have to maintain/coat your I-beams... ;')
Thank you for resisting the urge to rush to judgement and providing a step by step example of how the final forensic analysis will likely come together.
Dude you are killing it with easy to grasp explanations. I have retired a couple years ago from 41 years of construction. Mostly single family homes, but for a year or two high rise construction and condo buildings. I do not have any extensive engineering knowledge, man you lay it all out for anyone to grasp very complex building science. You are a born teacher. Thank you.
What a pleasure to listen to well-reasoned, organized, grammatically correct, and educational information presented in a way that listeners at any level are enriched in the process. It's nice to know there are professionals of this caliber doing this work. If RU-vid University had an awards ceremony, you'd be my nominee..
*A simple exercise:* For _each_ 100 pounds of _horizontal_ component of wind force directed against a north wall, each of the east and west outside walls that are at right angles to it takes up 50 pounds of force. If a third interior wall is added parallel to the east and west walls then each wall will take up 33.3 pounds of force. The floors that also transmit this horizontal component of force to the outside walls prevent concave deflection of the north wall. Is a third interior wall required? (Referred to in some discussions as a shear wall). After calculating the force that the east and west walls must meet it is a matter of design choice. It is likely that the minimum thickness of the east and west walls already greatly exceeds the force against which it must hold up to horizontally. Thus, for each 50 pounds exerted horizontally, the walls as a result of their thickness to function as a wall bearing up the vertical downward force from weight, are already capable of sustaining a horizontal component several times that amount. An interior wall of solid concrete that is not connected by rebar to the adjacent part of the building is in effect an _exterior_ wall to which an abutting building has been added that encloses it making it appear to be a single building. The reason behind this is _finance,_ not engineering.
I watch many RU-vid videos and I’m not exaggerating when I say that you deserve an Emmy Award for your videos on this incident. Your channel deserves to have several million subscribers (and hopefully one day will). I look forward to these videos like someone waiting for the next season of a hit TV show. You are truly a gem and I thank you for putting these incredible videos out. Your integrity shines through. I would feel very comfortable living in a building you designed.
I agree 100% with your comment. The few times I have clicked on other videos, I would get so mad. I went to comments and in the kindest way told them to come and watch this channel.
@@BuildingIntegrity I love your channel and have watched many of your videos twice to grasp the concept. Your explanations are very detailed and yet make the topic easily understood. THANK YOU for doing this for us! I know your time is precious with a family and a business to run. You are very much appreciated! Wish I could have you oversee anything I should live in! Your integrity has gained my 100% trust! Well done!
*A simple exercise:* For _each_ 100 pounds of _horizontal_ component of wind force directed against a north wall, each of the east and west outside walls that are at right angles to it takes up 50 pounds of force. If a third interior wall is added parallel to the east and west walls then each wall will take up 33.3 pounds of force. The floors that also transmit this horizontal component of force to the outside walls prevent concave deflection of the north wall. Horizontal force transmitted by the floors that is taken up by the footings of the columns and rear wall may be ignored for this analysis. Is a third interior wall of solid concrete required? (Referred to in some discussions as a shear wall). After calculating the force that the east and west walls must accommodate it is a matter of design choice. It is likely that the minimum thickness and strength of the east and west walls already greatly exceeds the horizontal force that these must hold back. Thus, for each 50 pounds exerted horizontally, the walls as a result of their strength to function as a wall supporting the vertical downward load from weight, are already capable of sustaining a horizontal component several times that amount, which is why the contribution of the footings was ignored. A building is designed so that the entire structure remains standing. That a collapse is only partial appeals to emotions, not logic. An interior wall of solid concrete that is not connected by rebar to the adjacent part of the building is in effect an _exterior_ wall to which an abutting structure has been added that encloses it making the whole thing appear to be a single building. Pre-construction-sales enabled raising capital for a much larger structure. The reason behind this two-phase approach is _finance,_ not engineering.
Another great video 27 minutes felt like five and I didn't want it to end I appreciate the time and effort it takes for you to do this you're a great teacher
Excellent explanation and teaching! It is like a zipper… the leading edge starts the “unzipping” aka punch through of the slab. Thank you for sharing your knowledge and putting together these high quality videos to help explain and learn from this tragic event. Take care.
I’m a black woman with zero interest in buildings and concrete 🤣 yet I watch almost every video you upland about the Champlain building collapse. I find myself looking around parking garages and buildings now. I had no idea about the structural engineering field. You are a wonderful teacher!
Take a look at highway bridges when you drive under them too. You can clearly see damaged concrete and rusted steel rebar from salt being used to melt snow and ice. It's just a matter of time before they fail also. Stay safe my friend.
@@justinhaase8825 the structural engineering field is predominately men. Hence look at most of the comments and a Google search. That is why I said what I said and stand by it. My experience and perspective as a black woman won't be dictated by a man or anyone else who is non-Black. I was simply pointing out this channel brings people from diverse backgrounds to a white male-dominated field. I also don't hold myself back. I'm a business owner and doing well in my life.
I have watched “postmortems” of the FIU pedestrian bridge collapse and the Morandi bridge collapse in Genoa Italy. Neither were talked about as clearly as you have in this series of videos. Thank you for making this make some sense.
I''ve never added a comment on any video before but you make it difficult for me to ignore your knowledge and presenting/drawing skill. Your explanation of difficult topics is amazing. Thank you for all you do and please don't stop. A
I have been watching your videos from the beginning of this awful incident and I have to say I appreciate you describing everything in layman terms for the Layman cuz I do understand a lot more than I ever did about engineering since I've been watching you
After these series of vids, we are never going to look the same way to a building, instead now we are going to look through walls and into the structure as a whole.
Crazy to see that headboard still attached to the sheer wall where someones bedroom used to be. Thanks for making these videos, as a concrete guy its really interesting to learn more about the science of why we do what we do.
Not just the headboard but also the hinged wood flooring in one of the x09 units but also the closet organizer in the closet to the right of bedroom and artwork on bathroom wall to right of that.
I think I know what you're talking about! I was looking at it and wondering "what the heck is that?" As soon as I read "headboard," that question was answered - but I'm still going to go back and look. I'm gonna look for the wood flooring, closet organizer, and artwork, too...
I've seen even crazier after a tornado. Whole house destroyed, cars thrown all over the place, and 2x4s speared through concrete curbs, and yet where a house once stood you might find a cabinet with all the china still inside it without even a crack on it.
At the beginning of the video Josh says the parking garage is covered in salt water again. This building had water intrusion issues not long after being constructed and obviously was the catalyst in it's overall demise. Josh explains things very well and does a good job in trying to make sense of it all.
I always wanted to be an architect but I don’t have the mathematical skills. Watching your videos gives me insight into the field that I appreciate. Thank you.
Architects don't use much math other than adding up what to charge for your bill. Structural Engineers live and breathe math and it's integral to their work. One is a more of an artist, the other is a serious profession. Don't conflate the two.
This is similar to Stairwell B in the North twin trade centers where 15 or 16 people survived... Just goes to show living next to stairs/elevator is not only fast to exit, but safer overall... sort of like living on a hill in a flood zone
In my building all 8 apartments on each level abut either the fire-stairs (as mine does) or the elevator shafts. I am very pleased that our building is particularly strong as a result. However, those who abut the elevator core experience noise from the elevators with those on the top two levels getting the worst noise due to proximity to the elevator motor room above them. So there can be downsides to living by the elevator shafts. But being by the stairs is brilliant. My building has two separate fire-stairs that entwine like DNA meaning that there is always a second stair with separate exit in case there is fire in one of the stairwells. This double-stair design made of 12 inch thick concrete is particularly strong, and with 10 inch thick floor slabs and 8 inch thick concrete walls I get the feeling that this building would survive a nuclear attack. It is unfortunate that not all buildings are built to this same standard. The building is over 40 years old and unlikely to be demolished any time in the next century, but when it does need to come down one day, I feel sorry for any demolition company that would have to tackle it. When looking at footage of Champlain Tower it amazes me that people paid top dollar to buy into a building that even if it was well waterproofed and well maintained, still looked like it had a very flimsy structure. They might think it makes the place look “light and airy” to have such small columns and wide slabs, but I prefer the stronger, more rigid construction of my building. I also prefer the way my building is built directly on sandstone bedrock and no soil-retaining walls in the basement levels, just solid rock walls. It helps me sleep at night.
nowhere is going to be 100% safe. Being on a hill will expose you to structures trying to slide down the hill, with all the potential for differential shifting of the structure. If your structure is significantly reinforced, it’s possible the original design was meant to allow for a less than fully rigid foundation. (saying this as I look out the window from the third floor of a condo on a hill/mountain). I approach it as a case of seeking moderation in all things, and also realizing that the world has been and continues to be a dynamic thing. We may try to freeze parts of it, or pretend that parts of it won’t ever change, but there are limits to what man can achieve. It’s important to recognize those limits where they occur, and either push back against them, or accept them as they are, and in all cases, respect them.
@@artistjoh WHERE exactly are you located, that the Engineers won out over the Accountants, and built to that high standard? Also, how many storeys high is your building?
@@Relkond ...OH, well, I really didnt mean it was safest in all... I should have said, home in clouds close to heaven with God overlooking with Pearly gates on the driveway
@@MajorCaliber 18 stories high, and in the Sydney CBD. Of course there is a twist - construction standards were so expensive that the builder went broke before construction was complete and another builder completed the job. It was built in 1980. It helps that the entire Sydney CBD is a sandstone ridge with little soil overlay. It means all building foundations are excavated into bedrock. The downside is all underground rail and tunnels are expensive due to rock excavation. It also helps that earthquake risk is as low as it gets.
I might've been horrible at drafting and I've always struggled with complex math, but those things don't preclude me from always having an insatiable hunger to learn about how and why our universe works (and doesn't work) in the ways that it does. Thank you very much for taking the time and effort to explain/edit these various concepts for laypersons such as myself. It is very much appreciated.
Short answer: thicker columns and rigidity of elevator shaft, stairwell and twelve stories of integrated storage rooms stood the second building up. Great details, Josh!
The other building did have larger columns from level 2 on down due to the column offsets at level 2 to clear parking layout in the basement. Those columns were larger than necessary for the load which is a bit odd considering that nothing else in the building seems to be that much larger than it needed to be. That would definitely give the west part of the building more resistance to lateral loads.
Wonderful. Your explanation and teaching method is superb. Just like the best of professors who have pearls of knowledge spilling from their mouths as they speak! Thanks.
Young architect here just getting started: your videos on this awful catastrophe have been an absolute joy to watch. I wish my structural courses had been this interesting and insightful!
Why I'm still awake at 2am watching a video about structural engineering is a mystery. The collapse of that building, not so much thanks to this very cogent, articulate explanation. I don't math, so I appreciate you leaving that part out of it, sooo much! I have much more respect & admiration for my cousin's structural engineering degree now. Thank you for an excellent lesson - now I've subscribed to check out the ones I've apparently missed.
I just wanted to say how much I appreciate these analyses you're putting out here. For a long time, I've been staying away from non-news channels for some insight into what could possibly have led to the collapse. The last thing I wanted to watch was some rando with dubious qualifications spinning a lot of premature conclusions, or worse, harebrained conspiracy theories. So, when I saw your channel pop up, I knew you were just the guys to trust. I recommended your analyses to all my friends who, like me, wanted most to find some good commentary on a truly staggering catastrophe from a solid, methodical engineering perspective. Thank you for your dedication, your passion for the material, and the accessibility you bring to complex concepts.
Thank you from someone who crossed the Silver bridge a week before it fell. My last work at the highway dept. was quality control on bridge construction. Wish I'd had you back then to explain things to me.
One thing that astonishes me about how clean the slabs tore at the shear wall, is how you don't see strings of rebar hanging down. It tore right through.
Yeah, I don't understand that either. I asked that question above. The engineer replied that he thinks they simply "snapped cleanly". I'm finding that hard to swallow, but he is an engineer!
Crazy isn’t it? My guess for not having rebar sticking through the shear walls is that it just so happened to tear in between 2 bedroom walls. Maybe they weren’t load bearing walls and therefore only had wood and no rebar in it but that’s just my guess. I am not an engineer
I'd want to see photos taken close to the shear wall, to see if the rebar sheared off more cleanly there, as opposed to the tangles we see from where the slab tore on a more diagonal path. What does appear to have been the case is that a combination of factors overwhelmed the building structure, pointing out that the building codes in effect in 1981 did not provide adequate margins, especially when potentially substandard construction and excessively deferred maintenance came into play.
I second all the comments about your teaching style. I work at a large Midwestern architecture firm. We have in- house structural engineers, and your explanations are much more interesting than anything they've ever said. Your videos are like a structural engineering lunch and learn (that's actually interesting). And thank you for helping me level up in my structures knowledge!
Love your videos… I don’t work in engineering or construction yet work with these teams to help business owners with their businesses as part of a management firm. Your explanations, clarity in defining terms, etc. have immensely helped me in my work and even my coworkers notice a change in how collaborative I am in their meetings. A tragedy brought me to your channel, but your content has kept me coming back. Thanks for all you do and your subscriber growth. Ciao from Italy!
Most tall buildings use traction elevators that go up and down with higher speeds, and they use guide rails fastened to the shaft walls, and uses counterweights along with the cables and the elevator hoisting machinery in that room where the ladder once was They do need extra strength to allow for the live loads. Great video...
John ... while the steel in the elevator offers some strength, it's the concrete box like structure around the elevator / stairs that gives the most strength. If you think about it, this giant box beam is basically 4 support columns that are interconnected and spreading the load in an area that's around 10 x 20 ft and that's more support than any of the other columns because of the solid walls all the way to the roof. If you watch any construction you will notice this part is first in the process and they are free standing before the rest goes into place. It's the strongest part of the building.
They interviewed a building manager of that building from the 90’s, he said that building’s garage had bad salt water intrusion even back then and the owners ignored his complaints and they just kept installing sump pumps instead of fixing the problem, he also said the part that didn’t collapse never had intrusion issues.
If I’d have you as a teacher, I totally could have been an engineer! I’ve followed all your videos on the Florida collapse and I completely understand everything you’re talking about. You should consider teaching. Thank you for explaining!👏👏👏
Also want to add my kudos to Josh for his incredible presentations in a clear, non-biased way. He is professional and instills confidence with his manner. Perfect! Total opposite of some other YT channels who seem to be interested only in the sensationalist angle. Thanks.
Oh YAY!! My favorite Structural Engineer is here. Time for class. Seriously though I can't wait for your next videos to come out. I have learned so much about engineering than I thought my brain could ever comprehend. I sure hope these videos continue after this mess has been sorted out. Maybe some historical failures of buildings or bridges or damns. Hey I would love to go on field trips to your jobs
Not sure about anyone else but I'm pretty much a structural engineer at this point, thanks to these videos. 😉 But sincerely, thank you for the amazing analysis and concept explanation. I am a physical therapist and believe it or not these concepts apply to our bodies - tissue and bone as opposed to wood, concrete and steel. All subject to the same forces.
I work in this industry-Inspection and your interpretation of what happened is really interesting, your on to more than most, appreciate the intricate details you provide, looking forward to your next one👌👈🏼🇺🇸🪙
Everything you present is so logical and the images support your theories and despite that, I still think no one ever imagined that building would ever fall.
14:00 The vertical fall of all that energy is taring along the path of Most Resistance, the shear wall, and then Least Resistance until it comes to a new line of Most Resistance, the next column line over. The first column line that collapsed, fell with a certain amount of weight and energy. The connecting slabs pulled at the next column line which was still strong creating a braking or deceleration action for all that falling energy. That's why the rear section didn't fall immediately with the first. With all that debris crashing into the basement, that energy was deflected horizontally into the rear and side columns which must have been knocked over which then expedited the rest of the collapse of the rear and right side. Basically kicking the legs out from under the structure.
I am an educator and I must say that you did a great job on scaffolding this information. Loved the models and explanations! You should teach you would be awesome!
Excellent video as always. Just an explanation of the paper tearing behavior from someone who has worked in the printing business for a long time: Paper is usually made from fibers that are aligned in one direction. It bends and tears more easily along the fibers, which is why most paper intended for printers has fibers oriented along the short edge so it more easily bends around the rollers in a printing mechanism. Conversely, paper intended for brochures and books has its fibers aligned with the long edge (for portrait oriented) so the pages can turn more easily and any changes in humidity cause the pages to grow or shrink away or towards the spine rather than causing terrible wrinkles and making the pages stiff. In the demonstration with the black paper, you can see that the tear proceeds quickly towards the left edge of the sheet, which points to the fibers being aligned with the short edge of the sheet. Otherwise, you would not have seen such a sharp, almost 90 degree turn.
A good point. I find that handmade paper made in a frame by the sheet doesn't show the same directional alignment as Fourdrinier or similarly roll-made paper, so that might be an option if a similar experiment was to be done again some other time.
@@alisonwilson9749 An equally good point! In our printshop, we used to process Tyvek paper that was untearable. It was made of plastic fibers, but these were also randomly aligned as to prevent any easy tear propagation if a tear should ever occur.
You do a great job of explaining this to us not educated in engineering, thank you, and like someone else commented you could inspire a young person into your field.
Your coverage has been fascinating; this was one of the most interesting. Ripping the paper and the red lines on the upper floors to show the elevation were great illustrations, even a jury could follow that. J/K... sort of. Nice job.
You are a genius. Your videos on Champlain South Tower are incredibly thorough, detailed to a T, informative and exciting to watch. I've learned so much from you. Thanks Josh Porter! ❤
Another great video! I understand your explanations and your reasoning. I love you videos! Your firm is definitely a few levels up. I would sleep well in a building that you engineered, Thank you.
No one has also mentioned that when this building was in construction there was a crane collapse sitting out front of the building. The crane fell while it was working on the patio.
Now, I finally know what a shearing wall is and how it works. Great presentation! I think it would be a great idea if you teach engineering tutorials online!
Built parking garages in LA with 4 story wood frame apartments on top circa 1980's... Always used a 12" slab with 3/4" rebar top and bottom at 12" centers each way. That's a lot of steel.
The building I worked out for the bulk of my career was only two story with all columns and beams being steel, with steel decking, wire mesh and concrete poured over it to form the second floor slabs. There were shear walls placed at specific locations throughout the structure. Periodically we would do space renovations to accommodate customer design desires. Occasionally these designs required the removal of a shear wall. In every instance structural engineers were brought in to evaluate the affect, not just on one specific area of the building, but on the entire structure itself. Shear walls removed were always replaced with much larger and thus stronger shear walls to compensate for changes in the original building design. I was in operations, but my education was in the field of business and economics. I learned a lot about shear walls and the need for them. The Surfside building collapse just reinforced what I had learned about how valuable shear walls are in any building construction.
I still say this building was designed poorly, built on the cheap and by cutting corners. What happened to the idea of designing/building a structure with a safety factor of 2? I don't see it in these plans and in the pictures used for analysis. It didn't help that the end users added poorly thought out extra features not in the original design, and then maintained the building poorly, too.
You're bucking a lot of closely-held Flori-duh traditions there... like how even the most expensive single-family residences in FL do NOT have a basement (due to the water table), while virtually every high-rise condo--even right on the ocean--have one, and sometimes TWO sub-basements devoted to parking... cuz poofty awkitects say cars be "yucky", and must be hidden away... _smh_
Awesome explainations of engineering and forces which led to calamity. It is a shame to me that more shear walls were not in the design ,but ,now it just is sadly what it is. Glad the shear wall did save some of the people sleeping in their condo. The structural continuity of that strong shear wall can be seen in the photo. CAN'T WAIT TIL NEXT VIDEO, KEEP'EM COMING.
I'm impressed that the remaining, bottom-most slab-on-grade is completely intact, despite the hammering it took during the collapse... OTOH, I suppose all the parked vehicles served, literally, as *shock aborbers* eh wot?
