Another engineer says that there was an elevation change in the garage and they didn't reinforce anywhere after that change . I've been learning about these structures from BUILDING INTEGRITY, and I agree that I've been so compelled to learn about building construction since the tragedy in Surfside. Thank you for being one of the channels that are trying to explain what may have been the factors for Champlain towers collapse.

@ED-es2qv

3 жыл бұрын

We haven’t seen any photos of un-reinforced concrete, just not as much reinforcement as we might expect. Even photos that some had said showed a lack of rebar, evidence can be seen that it was there and pulled out.

@otiswilson4713

3 жыл бұрын

There was a photo showing where the rebar was sheared before the building collapsed if those photos were from that building.

@johnjack6682

2 жыл бұрын

I disagree

Calculating the tributary area of that random mess of columns in the garage is no easy task. They are missing so many beams, reinforcing, columns, need larger columns, higher psi concrete, thicker slab , heavier reinforcing, and so many other issues. So many issues it’s mind boggling. Great video! Great job!

@inlikearefugee5194

3 жыл бұрын

And they were saying, 'how could this happened in the 1st world?' LOL! Like it's supposed to happen in upper Burma or Papua New Guinea.

@PaulJersey

3 жыл бұрын

@@inlikearefugee5194 I remember the Mayor saying that. Strange statement to make.

@designstudio8013

3 жыл бұрын

It is simple.

Cheers to you too! Finally I can visualize the forces of concrete’s tension and compression! Thank you! And yes, the on Building Integrity channel is another excellent source of information.

Thanks. I always enjoy these and have learnt quite a bit. I'm one that has no experience at all about the topic, it wasn't my profession. But since this building collapse I find all this interesting.

Great analysis! The lack of robustness or resiliency in the original structural design is certainly a major contributor to this cataclysmic collapse. The building structure was initially unable to resist a partial collapse.

@punker4Real

3 жыл бұрын

Everyone is an expert now in the surfside collapse

@seedplanter7173

3 жыл бұрын

Define robustness? Still waiting for the side by side comparison of 1st and 2nd collapse/ demo? What's the hold up?

@charlescrawford7039

3 жыл бұрын

@@seedplanter7173 From NIST " Structural robustness is the ability of a structure to withstand local failures without disproportionate collapse. Redundancy, integrity, and ductility are key factors that influence the robustness of the structure. The assessment of structural robustness requires simulation of structural behavior under various local failure scenarios." It was evident in the video of the building’s demise, the main structure collapsed as a result of a localized failure. Regardless, whether or not the overall building structure was deficient in rigidity, this issue will be part of the impending criminal and civil cases presented to the courts. The investigators will note in their report why the remaining portion of the did not collapse. One could reason that the shear wall and its location prevented the full collapse of the building. Also the location of the initial collapse in relation to the remaining part of building.

@Katoshi_Takagumi

3 жыл бұрын

@@charlescrawford7039 And that's something we would have wanted to see at Champlain South.

Saw a video the other day where someone went in to old real estate adds and showed how much marble and granite has been added to the condos. Also, the inexpensive cabinets for the kitchens and bathrooms were replaced with a much better (heavier) grade. The pool deck had been upgraded, a layer of sand and pavers were added. The person brought up how much water the sand would add, also a water barrier had not been put in place to protect the concrete. Plus you had large flower pots and trees at one time. Heavier AC units had been added to the roof. After the report comes out in a few years bet there will be many areas at contributed to the failure.

In recent years building codes and standards have been improved significantly, as has our ability to inspect and simulate old buildings to pre-empt future issues. The biggest problem we face right now is engineers who DO know better seeing old structures with clear design flaws compounded by construction errors, environmental degradation, misuse and poor maintenance who then fall victim to the fallacy of "oh but someone older and more experienced than me signed this off so its fine" or "well it hasn't fallen down yet so it's not going to fall down now" and kicking the can down the road.

Concrete is NOT WATERPROOF IN ANY WAY SHAPE OR FORM...this is why concrete relies on sealers and coatings to resist water penetration.

@Vallanda

3 жыл бұрын

Sounds like a typical desk engineer. Lol... "concrete is inherently waterproof" whuuut?

@EverydayDazz

3 жыл бұрын

Good quality concrete is inherently waterproof. The reason you put additives in concrete or add a membrane is to add a second layer of protection for the reinforcement. Just because I say concrete is inherently waterproof does not mean that I would design a waterproof basement structure without specifying a membrane or concrete additives.

@MassEffectGER

3 жыл бұрын

@@EverydayDazz How can a porous material like concrete be *inherently* waterproof? It can't.

Excellent video. I saw Building Integrity's video on the delimitation of the top mat. He showed the core samples that were taken before the collapse that clearly show delimitation. Thanks for running the calls and further confirming the cause. I'm going to nerd out on my girlfriend tonight and tell give her my final analysis. 🤣

Fascinating. Super impressive

From another analysis I gathered some of following facts and formulated a hypothesis: There was a waterproofing membrane added to the pool deck. Then a layer of sand was added and topped with pavers. The drain was extended to be level with the new paver surface. This allowed water to collect below the pavers in the sand. 1 cubic foot of wet sand weighs 120 pounds. Add the weight of the pavers and the large palm planters and now the pool deck is likely overloaded. Given the weakened rebar due to water penetration, the rebar eventually fails and the pool deck concrete slab sags and cracks as a result. In the video looking down the ramp prior to the collapse, water can be seen pouring into the garage from the ceiling. A theory expressed by another engineer is that a pipe had broken during the structural failure. I hypothesize that the water is pouring out of the reservoir created by the added pool deck membrane which had torn as the pool deck sagged. When the deck finally failed, it caused the resisting tension to fail. There is a very high probability that the slab broke the support column at the front wall of the building. The damage to the column and the loss of the resisting force of the pool deck slab caused a moment force on said column causing it to fail completely. After that, a catastrophic cascading failure occurred and the building fell.

Very nicely explained Darren. Well done. I think this one is the best video in the series. There were theories explaining that the slabs were hollow core slabs in the building and since Hollow core slabs(HCS) are not monolithically connected to the beams or columns that also contributed to this collapse. The screed on top of HCS was not sufficient as some videos claimed. As you said, slabs were not designed for ultimate load. I thing even the columns at base level were not strong enough to take the load of the entire storey. Would love to see another video on that. And a separate compilation video of all that. 😀

@86gautamp

3 жыл бұрын

kzread.info/dash/bejne/eoSrrJKDprfJl5s.html just a simulation video found on youtube

Everything you say makes perfect sense. Only problem is when you look at pictures of still standing columns, LONG lengths of rebar remain sticking out of the columns where the decks have collapsed. Most of what is seen is not noticeably corroded and the lengths of rebar seen would tend to indicate not much "shear" took place. Instead, it looks like the steel was sparse, at best, and way too close to the tops of the decks. What these images appear to show is that the concrete was sufficiently weak around the rebar to the point where the concrete failed releasing the remaining deck from the rebar. "Shear" activity would have left short "stubs" of rebar at the column/deck intersections. Look at those images that show standing columns where the ground level deck collapsed.

Thank You very much for the excellent job you did on this. PLEASE KEEP IT COMING.

Good job. Appreciate the time you took putting this into an easy to understand perspective. Sure makes sense.

Crystal Clear as always.

Learned something today: why there is tension on the upper surface of a slab near the columns.

Thanks you sharing your knowledge

the cracking at the negative area moments will result in additional deflection in the middle. when I inspect I check for delection using instruments. My understanding of ACI is that flexural members will deflect substantially to provide adequate warning against collapse in the code. Column heads were designed using concrete thickness. Shear head reinforcement is a later addition.

Great video/discussion

Would you be able to do a video on the calculations you mention in the video? It would be very interesting and informative.

@bewell4743

3 жыл бұрын

I agree. 👍🏻

I’m glad we can agree to this preliminary report. Builder Nathan Reiber failed to use good decking and limited amount of reinforcements from rebar.

@roycem4945

3 жыл бұрын

and a terrible design -- I wonder if there are regulations to stop designs where the pool deck can take down columns/attached to the building supports - unless there are redundant supports for the building

@Dilberto88

3 жыл бұрын

@@roycem4945 - This was a design flaw, by not making the pool deck completely independent of the main building structure. The catenary action of columns failing created the chain reaction building collapse.

@roycem4945

3 жыл бұрын

@@Dilberto88 I wonder if the insurance companies will demand structural upgrades in the Champlain North tower / East --- (especially the North since the design is identical to the South) - BTW: Did you read / watch the story on the Dolphin Tower Sarasota? They had structure / deck issues - back in 2010 and had to do two year structural upgrade --- The story compares it to the Champlain collapse. In the Dolphin, they first brought in bracing to the underground garage. -- Same company who reviewed Champlain in 2018 --- flagged the Dolphin's structure -- kzread.info/dash/bejne/n4dnwZugY920qrA.html ---- and kzread.info/dash/bejne/n4dnwZugY920qrA.html

Good graphics and good explanation.

There was a collapse of a parking structure in I believe Quebec City, that was caused primarily by deterioration of the reinforcing steel. When the slab was rebuilt, fiberglass rebar was used to replace steel. I wonder if more engineers will take another look at non rusting alternatives to steel, like basalt or fiberglass rebar?

Is this easy to test to ascertain the integrity of existing structures with immediate focus on non code compliant and aged buildings ?

I think that another factor might be the change in the dead weight of this building over the years. In the early eighties, condos and apts. had formica counter tops, ceramic tile floors and tub surrounds, carpeted rooms. If you look at the real estate listings of these condos recently, they have all been remodeled with marble and granite floors, walls, and counters everywhere. If there was only the bare minimum accounted for in the original calculations, the remodeling over the years put added stress on the building.

@yodaiam1000

3 жыл бұрын

As long as the structure was properly designed, there is a live load allowance in the design that takes care of those sorts of things. It would not have affected the deck collapse. But extra topping on the deck would be a contributing factor.

One of your diagrams shows what I assume is relative load distribution on the slab structure in shades of blue and seems to show very high loading around the area of the three critical pool facing columns which failed first as the building started to fall. Could you talk a bit about why static loads at that location would be so high ?

@designstudio8013

3 жыл бұрын

They weren't compared to the building's columns.

I know stainless steel rebar is extremely expensive, but wouldn't it be practical and economical to use it at the very lowest levels and pool decks where spalling can compromise the building?

@edg8535

3 жыл бұрын

From what I have read is the stainless steel is not as strong.

@Iconoclasher

3 жыл бұрын

@@edg8535 I know it isn't. I'm more of a mechanical engineer than structural so my guess is they could use maybe 20% more rebar to compensate. At some point during the corrosion process, SS rebar will surpass the strength of the weakened steel bar. Even is SS rebar is 10x more expensive than steel rebar if it's only used on the lower floors, it's still a tiny fraction of the cost of construction.

@yodaiam1000

3 жыл бұрын

@@edg8535 Its' yield is lower but ultimate strength is much higher than typical rebar.

@yodaiam1000

3 жыл бұрын

It is used on some bridges and was used in renovations in historically important buildings. It is very expensive but there are studies that do show it is overall less expensive for the long term care of bridges. However, I suspect the price will shot up if it was used more commonly.

Hi there were a lot of modifications to the units such as granite walls countertops floors up graded hurricane rated glass windows new pool deck look at the picture posted of the foundation 2 days ago it has a lot of sea water in it

Public photos show that drop panels were not part of the design? Would drop panels altered the outcome?

Punching shear is based on concrete strength in the ACI code supplemental steel reimbursement can be added but requires special details so you said something that in this country anyways is incorrect. Column failure is the most likely culprit for the collapse but weak slabs do not provide very good lateral bracing. Also a thing to note is punching shear leaves behind a truncated pyramid these slabs appear to have failed vertically as opposed to on a 45 degree slope I think this indicates a material problem that it couldn’t fully develop it’s shear capacity. Concrete is porous not waterproof that’s why we plaster a pool.. keep up you efforts though I enjoyed watching.

@Katoshi_Takagumi

3 жыл бұрын

Are you saying it isn't punching shear unless you get that 45 degree failure?

@randholtham8493

3 жыл бұрын

@@Katoshi_Takagumi I think the fact that the concrete broke straight up and down that there was a material failure of some kind that created some weakness that didn’t allow the expected shear strength to develop . Everyone says oh yeah that’s punching shear all right but I say take a closer look…. Even in everyday dazz’s video the ACI 318 snip it shows the calculation being based on this 45 degree failure plane.

Could or would using epoxy coated rebar on this building prevent the collapse from happening? I know coated rebar didn't come along until 7 or 8 years after this building was built.

@barrywilliams991

3 жыл бұрын

Because the epoxy coating gets damaged by mechanical forces such as necessary bending for engineering requirements or mishandling when installed, it has been discovered that the coating does little to nothing to prevent water intrusion caused oxidation and expansion. So, I'd think no. It may have delayed the degradation but it would have eventually happened due to the design of the slab that formed the floor of the interior and the pool deck. The big problem is the slab of the first floor and the pool deck is continuous. When the slab failed, the resisting force was removed and caused a moment force to develop in the column(s) supporting the front wall of the building.

Attention to anyone buying a high rise condo apartment! Either contact a housing inspector or local building code department in inquire about any deficiencies or code violations of the building where the condo is located. If you find any such violations, etc., don't buy the apartment!

Could they have reinforced the outer walls of the building so the collapse of the pool deck wouldn't have pulled the entire building down?

You focused on punching shear capacity, you didn't say anything about flexural design. My contention is that the flexural design was also marginal which allowed the slab to crack more than it should have, leading to degradation of reinforcing steel. If the negative moment zones are insufficiently reinforced and crack more than normal, that can affect the punching shear strength. If there were punching shear failures, or even some hinging due to flexure failure, the unbalanced moments at columns would increase punching shear stress on part of the punching shear perimeter and lead to punching shear failures. Josh alluded to this unbalance at the extreme failure condition but he didn't explain how it applies in the calculations prior to the collapse starting.

Hes saying the punching shear could be the reason for the collapse however I believe the foundation was sinking over time leading to a structural element failure. I think other channels explain better e.g structural engineer calcs!

@postie48

3 жыл бұрын

Yes there could have been a differential settlement but in my view rebar corrosion could have weakened slab causing deflection and/or concrete spalling to columns corners thus affecting both the ability to support to vertical loads in the columns (due to loss of cross section causing overload) and loss of restraint casuing column buckling - and failure of the columns. I am not sure if, or how many of the columns exhibited this second failure mode. They have not all been seen on the photographs. What is very clear is that there was a shear failure at the column/slab interfaces as seen on the photographs. It is less clear if this was due to rebar corrosion, design faults (code or calculation), lack of designed rebar, or the complexities of the column/slab joints and changing concrete strengths led to shear planes in those joints.

@MassEffectGER

3 жыл бұрын

Photos of the site after clean-up didn't show any sinkhole.

@postie48

3 жыл бұрын

Differential settlement doesn't require a sink hole. Also note the foundations (pilecaps/piles) have not yet been exposed. Excavation has been to top of garage floor.

@Katoshi_Takagumi

3 жыл бұрын

@@postie48 Differential settlement would show up as problems with doors and windows, though.

Nice video. You made a comment that the structure was not built per code. Do you mean current code or code at the time of design or permitting.

@yodaiam1000

3 жыл бұрын

Yes to both.

How would a column be replaced in such a building? They can't support the building by jacking the slab on top of the column around the column because the column on top would punch through the slab. Do they have to cut through the slab to tie into the sides of the column above the one they are replacing? It seems that you would need to support the stack of columns all the way from the bottom to the top of the building.

@designstudio8013

3 жыл бұрын

Add steel columns

still nothing on foundation, which was built on pilings set 2-4 feet below grade, into water table/sea level, which has gone up and down over the years. Only Building Integrity touched on this and mentions differential subsidence. Everyone looks at what can be seen, above the ground, but no one really looking below the surface....

This building failure is a PERFECT symbol of American infrastructure...poorly built doing the bare minimum...remember, most of our buildings have a general useful lifespan of 50 years at best.

@heathwirt8919

3 жыл бұрын

Most American infrastructure is more than 100 years old and for the most part still functioning. There are many steel frame buildings some considered skyscrapers built early in the 20th century that are still standing and fully functional. Don't automatically assume this one example represents all America infrastructure, it does not and to say so is propagating misinformation.

@rhianimal19

3 жыл бұрын

It's also a reflection of the inherent corruption within that system that allowed this kind of weak design, without adequate redundancy to be built, especially WHERE it was built. And that is partially political and partially #crapitalist, because in the US, DEVELOPERS run the show and own the local political hierarchy. Within their line of reasoning, losing a bunch of inhabitants of that structure after they built it and moved on is an acceptable consequence of bidnezz in AmeriKKKa. Further, these were not POOR people living in that structure, these were LUXURY condos with an oceanfront view. Their squabbling over the cost of repairs prolly cost them their lives in the short term, as acting sooner may have delayed the collapse into the future. Bidnezz in the US is strictly caveat emptor.

@designstudio8013

3 жыл бұрын

Dude in many parts of the world the lifespan is 3 years!!

@rhianimal19

3 жыл бұрын

@@designstudio8013 Is that your aim, to make the US like them?

Question about the robustness. How to or is it even necessary to account for robustness in a six-storey apartment building made out of timber when using EC if no information is given to take it into account?

@EverydayDazz

3 жыл бұрын

I’m not super experienced in medium rise timber structures. But you definitely need to consider robustness like any other building. Determine the disproportion collapse class of the building and follow the EC rules in the timber code on how to design for tie forces, key elements etc.

@LvPatriot1

3 жыл бұрын

@@EverydayDazz Thanks for advice. ;)

Concrete is porous - it's not "waterproof". Concrete reaches maximum hardness after a few years - it doesn't get measurably harder "forever", regardless of the graph slope. Otherwise good information.

@Katoshi_Takagumi

3 жыл бұрын

Which is why the waterproofing issue is so critical.

as an architect with a BA in architectural structures, I would like to see an engineering analysis based on 1980-84 ACI code versus current. also would like to see any old local amendments to structural codes and if they had any influence on the structural design.

@windwardpro

3 жыл бұрын

I had heard that it's actually based on 1975 code.

@Katoshi_Takagumi

3 жыл бұрын

@@windwardpro The building code, I believe, is the 1976 Florida building code. As I understand it, ACI refers to the standard not the local building code.

@windwardpro

3 жыл бұрын

@@Katoshi_Takagumi OK- sorry, I didn't notice that he said ACI. But what would the engineer/builder have used, the 1980 ACI as mentioned above? Also, how much does the local building code come into play- is there overlap? Thank you very much for this very technical analysis you have done. I have not seen any better.

@Katoshi_Takagumi

3 жыл бұрын

@@windwardpro A very good queston, you'd really need an answer from an engineer on that. I assume that the public code is the minimum that the contractor needs to comply with.

Should the other remaining structures be a concern?

@EverydayDazz

3 жыл бұрын

From a design perspective, I’d say probably not. I’d hope they have inspected it recently and checked that it has been properly maintained as I think the ultimate cause for the collapse was the lack of repairs to what was clearly damaged structure.

@designstudio8013

3 жыл бұрын

All the buildings in the world coming from an inspector with 20 years experience.

Excuse my ignorance, what is BMA??

A bit strong to say the design was not code compliant without any caveats....like it doesn't comply to Eurocode 2 etc.. Was your analysis done to ACI 318 or its 1979 equivalent or to the current Eurocode 2?

@EverydayDazz

3 жыл бұрын

Yeah probably is a bit strong but I did check to both codes. But either way, the building under normal conditions should have been fine.

@billj5645

3 жыл бұрын

I work under ACI codes and I'll back up what he says with respect to ACI 318.

@designstudio8013

3 жыл бұрын

@@EverydayDazz @ way still underdesigned as a beam was missing.

@yodaiam1000

3 жыл бұрын

Other engineers that have done an analysis have come to the same conclusion. I am a structural engineer but I haven't done an analysis of it but just from experience, the reinforcing looks really light and there are no drop panels. Any reasonable code from the first world counties would come to the same conclusions. Bending and punching shear stresses in concrete haven't changed much since the 1970s.

@Katoshi_Takagumi

3 жыл бұрын

@@EverydayDazz The actual code you should have a look at, is the 1976 Florida building code, I think. I have no idea if there is a requirement to retrofit older buildings to bring them up to code unless the buildings are located in seismic areas.

I get mad when see people trying to push maintenance factor as main reason. Try to put in your model additional centimeters of sand and tiles. Then add the heavy garden pots that had palms in it. Then consider that they had cars and forklift driving over there. From the rubble you can spot missing or incorrect placement of rebars. We don't have the concrete expertise yet but from an interview of the team who drilled the building for demolishing they said that it didn't seem to have the strengthness they expected to have. I think only on the last place you can add the cracks from poor maintenance. We have a video of the basement a year before, it didn't look good but it didn't look very concerning either. Especially because water was under the pool deck,in garage, not under the building. Under no circumstances a building should collapse suddenly. It should give many warnings that people can't ignore. And even if the pool deck collapsed that should be the reason for a total building collapse. I'm sure the building is barely standing and that the clone building is in big danger. A small earthquake or strong hurricane could collapse it if they won't reinforce it.

@Katoshi_Takagumi

3 жыл бұрын

There's no record of a forklift being there AFAIK.

@markmd9

3 жыл бұрын

@@Katoshi_Takagumi you are a cat what can you know :)

@Katoshi_Takagumi

3 жыл бұрын

@@markmd9 I'm not a cat.

What about the other theory regarding a slab height change? The original plans indicated a 12" drop from the building slab to the pool deck slab, with a huge BMA under it. The changed plans indicate a now flat slab with no drop from the building to the pool deck, and now no BMA under it. Revised plans now have the pool deck and building slab connected to each other, instead of the pool deck being a separate slab from the building slab. Combined with water leaks, rebar rusting, cracking, this appears to be the main issue that brought the building down?? Thoughts?

@designstudio8013

3 жыл бұрын

Beam A is the beam type. Not what that idiot from the other channel mixed up with a MBA.

@designstudio8013

3 жыл бұрын

Nope. the massive shear wall took the eccentric loads

@yodaiam1000

3 жыл бұрын

BMA=beam type A. The slab was tied together regardless. It is normal for the ground floor slab from the exterior and interior to be tied together. There are usually steps just to deal with all the geometry issues with the architecture. Don't listen to the the nut bar on the other channel. He is just a realtor and small time contractor with a really big ego and no knowledge.

@designstudio8013

3 жыл бұрын

@@yodaiam1000 you mean to cocky one with the cats?

@yodaiam1000

3 жыл бұрын

@@designstudio8013 that’s the one. The realtor with all of his “conclusive files” and the “amygdala” that keeps on firing off. The “engineer” that doesn’t believe in gravity. It was kind of a joke of a character but now he flames other people and then blocks them so they can’t respond. He is a text book Dunning Kruger effect. It is hard to believe people fall for that stuff.

Why the inaccuracies in the model, though?

@EverydayDazz

3 жыл бұрын

If you’re referring to me not modelling then walls. I only used the model to look at punching shear in the middle of the building so the basement walls don’t really have an impact. If I was to reviewing moments then yes I would model the walls.

@Katoshi_Takagumi

3 жыл бұрын

@@EverydayDazz Understood, if you really just want to use it for punching shear. It's just that some people may interpret it as a forensic analysis, not a demonstration of a single mode of failure. I'm what you could call an 'interested layman' and, by way of a tip, I actually prefer your videos to BI... and I also like it how you can make the basics easily understandable.

@EverydayDazz

3 жыл бұрын

Thanks. I probably should have put a disclaimer or noted my intended purpose for the model.

Torrisional rotation of slab diaphragm ended the building. Lack of SWS

ACI allows 3/4" coverage with a tolerance of 1/8" which is not enough.

@postie48

3 жыл бұрын

From my memory of rebar deign 50 years ago (in uk) cover determination was based on exposure conditions and rebar diameter. 20mm or 3/4" would not be enough in a external marine environment (especially with a saturated slab)

@designstudio8013

3 жыл бұрын

@@postie48 Yes but that is not classified as marine. 1.5" exposed to weather. Still horrible inadequate as most construction is out of square.

Ok want to clear this up: Probably a poor choice of words saying "concrete is inherently waterproof" what I am trying to say is that a good quality poured concrete can be fairly water resistant by itself. I understand that it is still porous but it takes a lot of standing water to penetrate through. Nonetheless, a water retaining structure designed to keep water out like in a basement should have a minimum of 2 layers of protection. Normally that comes in the form of a waterproof membrane and additional additives into the concrete to make it waterproof. I've never once said that I would solely rely on bare concrete to repel water nor have I once said that I design structures that do not crack.... The problem as I've highlighted in this video, is that concrete cracking needs to be controlled by adequately placed reinforcement.

3:19 shows a different design. Columns have capitals and slabs are supported by beams in addition to the columns. Champlain has neither, only flat plate. There is no evidence of crack propagation in the interior away from the garage. But all those interior columns can be seen laying on top of the slabs. That can only mean that all of the slabs slid down all of the columns just like the pool deck. Inherently unstable design. Danger for those living in similar structures. 60% of Mexico City collapse were that same design. The sister building are not safe.

@Vallanda

3 жыл бұрын

His drawing is missing a bunch of beams and slab height changes. A result of his thorough review of the drawings I am sure. Which makes his opinion worthless since he didn't even attempt to analyze the correct structure.

Concrete hydrates for its life time as the strength increases.

They must have used a super special concrete on the west wing that didn't colapse

@roycem4945

3 жыл бұрын

It didn't collapse because it was a rectangle shear stairwell - going from the ground all the way to the roof. IF they only had another one - instead of just one shear wall --- it would have saved the other half of the collapsed section --- Thus this building design was a death trap -- terrible design.

@alidycepaisley3829

3 жыл бұрын

The section that didn't collapse was also of a more robust design than the section that did since it contained a greater number of transfer beams in addition to the columns in the lower storeys of the building - at least it did in the preliminary plans. Assuming those were in the actual structure as it was built, that probably helped it holds its composure during the stress of the collapse instead of actualizing a cascading failure the way the other part of the building did. After all, the shear wall in the Eastern section of building actually stood for a short time as the surrounding slab network punch sheared around it. The section that collapsed was only slab and column with far fewer beams, almost none really, save for a few in the parking level ceiling close to the lower end of the car entrance ramp.

The design would be considered non standard, in bridge terms. Non standard means it was designed to a code no longer in use. In most cases non standard does not mean unsafe. This design likely limited the stress in members while only considering service loads.

@yodaiam1000

3 жыл бұрын

It was and is a fairly common structural concept. It was just that the rebar and slab thicknesses were under designed (even for the era). This concept can be designed to current and old codes. If properly designed, he slab design would not change too much between the codes.

@m.5051

3 жыл бұрын

@@yodaiam1000 I honestly have no idea what you're trying to say. There's definitely a difference between members designed to ASD, LFD and LRFD.

@yodaiam1000

3 жыл бұрын

@@m.5051 Either way you design it, the end design is very similar. You might get 15M at 12” with LFRD or 15M at 11.8” with Allowable. There is not much difference. LFRD is slightly less conservative than Allowable. If you can’t make a design work in LFRD, it won’t work in Allowable.

@m.5051

3 жыл бұрын

@@yodaiam1000 I do not believe that to be true. What is your experience with the different design methodologies?

@yodaiam1000

3 жыл бұрын

@@m.5051 I was going through my undergrad during the transition. Statistically heavy DL buildings have a lower overall effective FS with LFRD. That is the whole idea. DL is more predictable so it has a lower factor.

The clown on the other channel said a beam was missing transverse at staggered column area

If you have cracks showing up in concrete you have a problem.

Rebar under stress will break concrete .

Is it we can't reproduce Roman concrete or we don't want to. The Roman buildings have stood for thousands of years we want the modern building to stand for only fifty years. This story reminds me of a story where a man designed a drill for a company they loved it. Then the last thing they ask how long will it last he said 10 years. They said we don't want it to last past three years. They will build a new building in it place to last for fifty years they hope.

Do you understand concrete does bend it breaks.

Hi, did you know your channel is being ripped apart and criticised by some guy in the states that has been going on about this collapse for yonks!

@EverydayDazz

3 жыл бұрын

Yeah I think I know who and I’m choosing to ignore it.

Unfortunately these guys commenting on the collapse have been mussled by the fool on another channel threatening lawsuits.

@EverydayDazz

3 жыл бұрын

I’m aware of that channel and I pay no attention to it. Would only make me annoyed.

The building was build around 1980-1984. Limit states (LFRD) were implemented in the 1990s in the USA, so your calculation isn't correct. Good job on explaining engineering stuff to "normal" people!

@EverydayDazz

3 жыл бұрын

I did check it to both ACI and eurocode codes. Just didn’t make it abundantly clear 😅

@stefanstoichev8108

3 жыл бұрын

@@EverydayDazz No no no. ACI and Eurocode use Limit States design method. Before Limit states, engineers used Allowable Stresses Method. In ASM you dont have coefficients for the loads, just the materials and some of the equations are different.

@designstudio8013

3 жыл бұрын

@@stefanstoichev8108 I would like to see some calc on the deck collapse causing moment at columns...

@yodaiam1000

3 жыл бұрын

The end design would be very similar. It is still reasonable accurate to compare allowable to LFRD. I don’t know about the US, but we brought LFRD in the early 80s. We used to call it LSD. Limit States Design. For some reason they changed the acronym.

@Katoshi_Takagumi

3 жыл бұрын

@@yodaiam1000 Can't possibly see why....

I don’t think it’s meaningful to say concrete keeps getting stronger with water exposure. Structures are always more complex than a lump of solid concrete, and structures don’t get stronger over time with neglect. There’s never a structure that was barely strong enough the day it was finished, but got ten percent stronger over the next fifty years because it got rained on. They always get weaker. Once the building collapses, you can walk up and point at a ball of concrete, and say “look, that concrete is stronger than the day it was built”. And I’ll say, that’s a deceptive use of the term stronger, since it’s balled up on top of the building occupants.

@EverydayDazz

3 жыл бұрын

I think you misinterpreted. I’m saying concrete keeps getting stronger very slowly due to the hydration process from the water that was used in the original mix. Not suggesting that you can submerge cured concrete in water to make it stronger.

Someone explain why no ones cares about who was in charge of "Building code" with? Someone said this place was safe . Wake up numnuts!

@windwardpro

3 жыл бұрын

As he said in the video- even with the poor design, it shouldn't have collapsed. The blatant lack of maintenance and repairs over time was the reason.

Structures are made with steel and cement. The cement breaks off and the steel is left to rust. Stop trying to bull sh t people