@53:28 Question was: "Is UHPC generally heavier than conventional concrete?" WJE materials engineer Elizabeth Nadelman gave a very enlightened answer beginning with an authoritative declaration that "the typical density of conventional concrete is 145-150 lbs per cubic YARD". I know she definitely knows what she is talking about because she then followed that up by smartly stating, "UHPC is a little bit heavier than that because of the steel fibers found in UHPC and therefore typically weighs anywhere from 155-160 lbs. per cubic YARD." WJE should be delighted to hear that Boeing Aerospace is currently in the project funding phase for development of a basalt fiber reinforced all UHPC flying luxury cruise ship that is expected (based on Ms. Nadelman's expert findings) to typically weigh less than a cubic bundle of Howard Hughes balsawood sticks.
Why arent more comments pointing out the pool deck columns were under designed since day 1? That is the smoking gun to me and should have been identified during initial construction. Someone cut corners back then or is completely incompetent.
Well done seminar . You covered the major performance and reliability issues. I hope the consumer market will see product soon. The heat lose improvement is significant.
Silica flour is crystalline since it is made by finely grinding silica sand. Silica fume is amorphous (non-crystalline) and its particles are spherical. Silica fume has extremely small (1 micrometer) while silica flour particles are larger (4 to 16 micrometer). Size differences are used in particle-packing principle.
When considering the weight difference between UHPC (155-160 pcf) and NC (145-150 pcf) you need to consider that UHPC has some of the reinforcement in it already even if the application is only shrinkage. That consideration of reinforcement amount and weight would increase the pcf weight of NC by at least a little. The fact that UHPC is about 3-4x the compressive strength of NC also might bring in add'l weight for the NC when reinforcement is used on it for increased compressive strength.
When buildings are that close to the salt water, It must be Mandated that they use STAINLESS STEEL REBAR which won't rust like steel rebar will. it doesn't cost that much more and they were getting ready to spend over 10,000,000. on concrete repairs. stainless steel rebar would have been way cheaper.
They found little chloride inclusion in the concrete as shown here and they also said rebar corrision wasn't a major contributor to the failure. It's proximity to the ocean had nothing to do with it. More over, stainless rebar was not used in common construction back when this building was built.
This is a very depressing story. This collapse was completely preventable. People should not be murdered by their home. I would be very nervous if I lived in the sister building a few blocks away.
Most interesting to me has been the still obscure history of the genesis and prescription of the “40-year Recertification" requirement. Who approved, who adopted, and who influenced (if it was) the official creation and handling of such new, broad and very important document for the present (back then) and future of the real estate market and its "health". I say this because it might have been redacted and sent to city officials as "the requirement" or something that seems to be the sole requirement between notice of completion and 40 years after, therefore possibly influencing in opposite effort or mindset to the original preventative mindset or effort with which "recertifications" should be handled by associations, public in general, attorneys, professionals, etc. (assuming this preventative mindset is aligned and is a good example of responsibility: to "advance our nation's quality of life and protect the public's health, safety and welfare". If 40 years is not enough to make sure buildings don't collapse (and it wasn't enough back then since it all came from a building that had collapsed after 40 years) then why was the policy or prevention bar set at 40 years? who benefitted from that number, and who really set 40 as THE number. Thanks!
Miami-Dade and Broward Counties followed by the State of Florida adopted 40 years based on the 1974 DEA building collapse at the age of 49 years, which was caused in great part by excessive corrosion frequently found in Florida. 40 was intended to be conservative enough to prevent a similar recurrence. They were focused on corrosion rather than improper design. The engineer who developed the recertification program was John Pistorius.
The under-designed pool deck was not waterproof. This allowed water in. The rebar rusted and the concrete slowly started to dissolve. You can see the wet areas on the deck photos. Faulty repair and faulty repair design.
I am concerned about the lack of security video evidence. To date the only video released is the one we've all seen and the only reason we see that is because the condo tower from which it came released it directly to the press. Champlain Towers' own security video should be available because the portion of the building where the office is located and more than likely the location of the recording devices, did not initially collapse and there is no reason why they would not be retrieved before the building was demolished. At the very least someone should offer an explanation of what happened to each and every video recording that captured the collapse. Did the condo tower on the other side of Champlain not have security cameras? I dont understand why no one questions the lack of video evidence and just accepts that the one we see is all there is. That doesnt make sense and it defies logic. I say this because I have worked in building security for more than 20 years and I know about security camera systems. I have worked in everything from beachside condo towers to 50 story office buildings. There is tons of video footage of this collapse. I guarantee it.
The security cams were not on the cloud…they wrote to a hard drive. At the June 2023 public meeting, NIST stated they have recovered several dozen hard drives and are examining them forensically. So far they have not identified the security cam drive. From what I have been able to learn, no one rescued the alarm system control unit before the implosion either. You have to remember that first responders were desperately trying to locate survivors before an incoming hurricane. The standing part of the building was moving every day…there were times it was so unstable that the rescuers had to leave the site for their own safety.
@@Lethgar_Smith Since we don’t have access to all the info NIST has, it’s hard to say how much of the lobby was left standing when the building collapsed. That section back beyond the mail room is probably where the DVR was kept, and I am not sure if that area fell down into the lower level or stayed up at ground level. We can’t go by Miami-Herald infographics. Security Guard Shamoka Furman was at the security desk by the valet window, making calls to residents, when the building collapsed. She was in total darkness and dense clouds of dust, so I doubt she would have been able to see what happened behind the security desk. Shamoka attempted to exit through the valet window, as the electric doors wouldn’t open. She ended up exiting the lobby to what was left of the pool deck, where she climbed down to the ruined garage and rescued several residents on her way to the street. So Shamoka never went anywhere near where the hard drive was likely to have been, and can’t tell us what was standing and what was not standing. As I said, it’s hard to know what was still on ground level.
I know this is almost immaterial to the investigation; the part that confuses me is why it failed in the middle of the night. In a progressive failure like this I tend to have a mental model of strength gradually decreasing over time, with noisy actual demanded loads, and failure occurring when actual load exceeds the strength. But because the strength decrease is slow compared to the timescales over which the actual loads are noisy, you tend to see failures near locally-high loads (in the temporal sense, not spacial.). But in this case... as you mentioned, it's the middle of the night and all is quiet. You've pretty much got your baseline load and that's it. No live load to speak of. Why did it fail at 1:10 AM and not, say, 7PM the previous evening when there presumably would have been people (and hence additional load, and worse, live load) on the pool deck? Was there rain that evening? How much of a temperature swing was there?
there was a strong rain, there was sudden additional loads imposed on roof deck (I vaguely remember hearing some equipment was being installed in the roof deck), could have also been suddenly windy (increased lateral load from a specific vulnerable direction), yes temperature difference between sunny day and wet windy night, all important factors. Also more people at night. I believe the planters got clogged and full of water, that weight caused beam under planter to fail, that created a whole in pool deck (per witness account of a whole in pool deck area), then the slabs failed and pulled the columns inward in direction of void center, then column failure at parking level and pool deck level (under that wing) cause the sudden collapse of the whole set of columns at each column location, with them the slabs.
@@DrgnTmrSirGawainThe roofers were installing new anchors for window washing. The City of Surfside building inspector was up on the roof inspecting the work that afternoon, and said that there was no abnormal loading up there. The roofers did have to pull off the job that afternoon on account of rain. Also…the sounds of failure were occurring as early as 11 PM, when Chani Nir returned home to 111 from babysitting. I have never found a witness who claims to have heard “banging sounds” prior to that time, and don’t know if Shamoka Furman could hear those sounds in the lobby. So, until NIST reveals the results of their witness interviews, we don’t actually know the earliest time when people started hearing the rebar fail, but we do know it was in the process of failing by 11 PM, and we also know Chani’s mom and brother heard it when they got home at about 12:30..
Did the pool deck slab also act as a strut, propping the top edge of the basement retaining walls? If so, once a significant portion of this slab failed in punching, struct action would have been removed and horizontal loads from lateral earth pressures on the basement wall could then act on the columns.
Здравствуйте! Испытайте пожалуйста на прочность при попадании в плиту из uhpc бетона авиационной против бункерной бомбы (gbu 28), какая толщина Вашего бетона не пропустит её насквозь???!!??? Обязательно чтобы бетон был армирован микро стальной фиброй. Благодарю. Я тоже делаю подобный бетон, но работаю один. У Вас возможностей побольше!) А вопрос сейчас актуален как никогда. Если результат будет, то этот бетон у Вас купят для укрытия богатые люди. Мира всем и добра!
Great video. Thanks for your the information. I'm more concern about the shrinking effect if compared to conventional concrete. Could you please elaborate more on this issue?
There are some incorrect statements with regards to the concentrated business use areas (33:15). Per 1004.8 you do not need the building official’s approval to increase the occupant load from 1occ/150SF to 1occ/50SF. The code language states “where approved by the building official, the occupant load for concentrated business use areas shall be the actual occupant load, but not less than one occupant per 50 SF”. Meaning you can go denser than 1occ/50SF with the building official's approval. Section 1004.5.1 increased occupant load already allows the designer (without the building official’s approval) to increase the occupant load from those in the table as long as you can accommodate the increased occupant load with the egress, restroom capacities, etc.
At 5 minutes 46 seconds, it's shown that water-cement ratio is less than 0.20. What about adequate cement hydration?....Hydration needs roughly a water-cement ratio of 0.23.
Извините,что вмешиваюсь, но 0,20-0,15 это нормально для гидратации. У меня на сам цемент приходится 0,15%+(1/3 воды на микрокремнезем, а его кладу 10%от цемента) , и получаю SCC. +160-180кг микро фибра стальная.
52 Lbs of superplasticizer pcy seems highly excessive. Most documentation I find suggests 1% superplasticizer at most of concrete weight, The UHPC mix in this video has superplasticizer around 4.5% the weight of the cement.
Действительно, 2,5% достаточно для водоцементное соотношение менее 0,20. Но для сообщения менее 0,15 надо уже 3-4%пластификатора. У меня получалось делать scc и при соотношении 0,11, но уже пластификатора 6%
The knobs of the showers and sinks are thin plastic and someone just to try to open it they just breake in your hands, thid is awful,.. the maintennce guy told me that no longer did stainless steel one were sold. Does he think i was born yesterday its just awful.
Using for years here in France for thin bridges artistic building walls and especially in exterior furniture designs This is a huge breakthrough for steel-less designed projects
The lack of information about the Carbon Dioxide emissions of this UHPC concrete is worrying, and throws any benefits out the window if we cannot decrease these emissions. As this is the current need for infrastructure at the moment.
