Does anyone know what columns were slated to be reinforced with new Drop Panels?
(Note #10 on Drwg S2C-1.0) calls for new Drop Panels.
(picture of pool deck columns just added for info)

https://www.townofsurfsidefl.gov/docs/default-sour...

98% of the posters todate seem to be structural engineers and perhaps that is how it should be but I think most people here would agree that there has not yet been a "smoking gun" identified. I cant help but feel that an earlier post might be closer to identifying the smoking gun.

am not a structural engineer. I can only say that in South Florida there is a lot of limestone embedded in the soil. Regular flow of water in and out of the area around limestone will cause said limestone to dissolve. There have been also reports that the ground around the build had been sinking slightly each year. The water from the pool deck would also contribute to these processes. What I am think is a sudden subsistence of the ground under the building starting in the pool area. This would cause the building structure to fall a short distance with a sudden stop or impact. This impact cause a chain reaction cause the floors to collapse from the bottom up.

Has a local geotechnical engineer been invited to investigate this possibility?? Are there other buildings in the locality that demonstrate similiar effects??

Quote (Spartan5)

1. If debris from the roof were hitting the ground outside of 111 it wouldn’t sound like it were coming from the unit above. And after falling 12 stories it would have to sound a lot louder than annoying construction noises. It would have sounded like it was coming from outside. And they would have rushed to their windows to see what it was.

I think the more likely culprit of the sounds described by the Nir’s as coming from above/in the wall are the remains of the fractured cast-iron sanitary risers that pass through their unit rebounding around. The daughter was in the shower at the time and her statement about expecting to see the wood floor all around when she came out of the bathroom adds some additional support to that. She would have been standing directly over one.

Quote (GPR_Tech)

In the NW portion of the building. In areas that didn't collapse.

Quote (warrenslo)

Structural drawings state 25% are to be load tested after installation (5000 lbs)

We do not know if they were load tested for inspection.

5000 lbs on one of those cantilevers, especially the penthouse patio with long spans could have damaged the concrete causing it to fail later.

Load testing adhesive/epoxy anchors in this sense does not mean pulling on the post/davit. Anchor load tests are performed with a special rig (hydraulic jack with center holes) that fits around the individual anchor bolts and the bolts are stressed until they reach their proof load. Elongation is also measured and limited to the amount specified in the detail. I have a hard time seeing how this would cause an entire 8" section of roof-balcony to collapse. At worst, there would be a concrete breakout failure in the area (probably 8"x8") immediately around the anchor bolt.

Quote (warrenslo)

Structural drawings state 25% are to be load tested after installation (5000 lbs)

We do not know if they were load tested for inspection.

5000 lbs on one of those cantilevers, especially the penthouse patio with long spans could have damaged the concrete causing it to fail later.

Someone at a press conference needs to ask the city if the roof anchors were load tested at inspection and if so specifically which locations.

As someone who has designed and observed post installed fall arrest systems on buildings as old as 120 years old and a observed the load test. No. Typically the load test is performed by testing, by tying two anchors together, then jacking them with a load meter until yes, 25 percent of the load is met. The 5000 lbs is an ultimate load, they are test loaded until 1250 lbs. 1250 lbs is not going to bring down a building. This Dik indicated earlier, the anchors a red-herring and not relevant to the overall collapse. Ive attached what the load test of a new fall arrest system into a 1940's era building looks like for reference. If a 1/2" cable can bring down a building: You have bigger problems.



Edit: Just going to add, that the wind pressures from uplift and down forces on those cantilevered sections are probably more than 1250 lbs for wind speeds well below code level events. The fall arrest system is highly unlikely to be a contributing factor.

Another thought on the possibility of a vehicle collision with a parking garage column instigating the initial failure:

Many (most?) newer car models have a black box (Event Data Recorder) that records - among other things - the speed directly before a crash event. That would be a way once they get to the bottom of the debris pile to see if any of the vehicles in the garage might have hit something and how hard.

I also wonder if any of the onboard assistance services (OnStar, etc) got a notification of an accident in the vicinity in the time before the collapse. These services are cell network and GPS dependent, so they may not work reliably in an underground garage, but it might be worth checking out.

Bradley Wilder, P.E.
Construction P.E. (KY), MBA
Bridge Rehab, Coatings, Structural Repair

As far as litigation goes or 'take away lessons', would a car hitting a column or a weakened roof/balcony element falling change anything? Neither should cause a building to collapse.

Relevant article discussing this, please read before dismissing this hypothesis. Link

Quote (Marc Lebel, CEO at Pro-Bel Enterprises Limited)

In the preamble of the new general industry standard OSHA refers many times to the 1910.66 permanent power platform standard recognizing that the regulated equipment is the same or similar . This standard tells us that all related equipment including roof anchors require functional testing not load testing.

In accordance with (1910.66(g)(1) osha required that all completed building maintenance equipment installations shall be inspected and tested in the field before being placed into initial service to determine that all parts of the installation conform are functioning as required. Federal osha further explains in section 1910.66(g)(2)(ii) that; All parts of the equipment shall be inspected, and where necessary, tested to determine that they are in safe operating condition. Mandatory testing of any part subject to wear is specified in section 1910.66 (g)(4)(1) which also includes governors and safety brakes .

IWCA -I14 industry standards effecting window cleaning equipment is more specific . They require all roof anchors to be lab tested to 2500 lbs half of its ultimate load . This test is a design tool or as a comparison model. Where by, the factory load testing of 2500lbs or half the ultimate load of 5000lbs is necessary in order to prove the anchor design against its theoretical calculations.

On site testing is not given extensive or specific treatment in the codes and regulations, so interpretation and sound engineering judgement are necessary to determine appropriate loads and testing method.

Load testing programs can have the following benefits :

Load testing may be necessary in determining structural capability of installations with out prior certification.
Load testing of adhesive roof anchor installations is universally required by all manufacturers.
Load testing is almost always required in determining failure if an anchor is used In the event of a fall or any type of equipment failure .
Load testing of anchors may be required to yield the necessary documentation in order to producing engineered drawing.
Load testing may be the only feasible option in determining if the existing installation is structurally sound.
The following information can be used to develop an effective test program to yield meaningful results. A proper program requires a test prescription to be developed by a professional engineer. Once this is done a carefully selected test load will need to be prescribed to address the specific components. The engineer must have first hand experience in the design and testing of this type of equipment because roof anchors and rigging equipment are designed with various components and sub-system that have variable working load and safety factors.

To ensure the structure is not damaged the engineer must review the building drawings to identify if the building structures can handle the concentrated loads necessary to test certain components.

Any load test program even if it is similar to past projects, will need to be somewhat customized in order to test within the allowable stress of material and not to damage the base structure.

Despite the engineers best effort, risks remain during load test operations. These risks include a possibility of building collateral damage including damage to the structure , roofing or anchor . In most cases the benefits of testing outweighs the risks, but those risks must always be kept in mind when pursuing a load testing program.

1. Roof anchor testing can cause catastrophic failure of an already damaged building - we have had them fail before on wood structures.
2. The anchors being installed at the time of the collapse were on the bootleg penthouse which has large unbraced spans across the large decks.
3. The structural drawings for roof anchors listed two concrete slab depths 6" vs. 8" - which was used for the calculations.

So the question remains, were the roof anchors field-tested less than 24 hours before collapse, and if so, which anchors were tested?

Concurrent with the removal of debris, they towed at least two damaged vehicles away from the site. FWIW. Can’t say for certain they came from inside the garage.



And

https://twitter.com/trentkellywplg/status/14101741...

That he is using 3/4" cover makes me a little suspicious of what his credentials are. I'd also have removed 1-1/2" of conc from around the columns to provide some direct bearing. Missed it...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Quote (bradw1128)

Another thought on the possibility of a vehicle collision with a parking garage column instigating the initial failure:

Many (most?) newer car models have a black box (Event Data Recorder) that records - among other things - the speed directly before a crash event. That would be a way once they get to the bottom of the debris pile to see if any of the vehicles in the garage might have hit something and how hard.

I also wonder if any of the onboard assistance services (OnStar, etc) got a notification of an accident in the vicinity in the time before the collapse. These services are cell network and GPS dependent, so they may not work reliably in an underground garage, but it might be worth checking out

It’s unlikely a collision significant enough to trigger the EDR Data Save occurred. Same goes for eCall Telematic response. You either have to trigger airbag deployment or experience a very significant rapid vertical load reversal rate. What may be of assistance are the time stamps for Alarm Event Data. There’s no shortage of vehicles visible at the site that have this as standard.

From the condition of the building, he could have hit the column with his car door when he opened it...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Quote (warrenslo)

1. Roof anchor testing can cause catastrophic failure of an already damaged building - we have had them fail before on wood structures.
2. The anchors being installed at the time of the collapse were on the bootleg penthouse which has large unbraced spans across the large decks.
3. The structural drawings for roof anchors listed two concrete slab depths 6" vs. 8" - which was used for the calculations.

So the question remains, were the roof anchors field-tested less than 24 hours before collapse, and if so, which anchors were tested?

1. The anchors, if tested, did not cause a catastrophic failure of the building collapse while being tested. The catastrophic failure would have happened hours, days, weeks after the test.
2. The anchors were installed well before the collapse. Not at the time it happened.
3. Not that it matters, but how do we know what was used for the calculations? Is there a comprehensive design report that went along with the plans? By what mechanism would this miscalculation cause the failure?

Maybe they were installing the anchors and conducting the test in secret at night under the cover of darkness because they knew they were not in compliance with the plans and that the slab was too thin. When they loaded up one of the anchors a large piece of roof fell off. Fortunately they were all on the side that remained. So they hightailed it down and were able to escape before the whole building came down. Just a theory.

Quote (warrenslo)

Relevant article discussing this, please read before dismissing this hypothesis

I have read it, and subsequently reaffirmed my dismissal of your hypothesis, as have numerous others with long histories of relevant and insightful comments and input on hundreds of threads. You have a right to your opinion, as we have the right to dismiss it.

Quote (warrenslo)

1. Roof anchor testing can cause catastrophic failure of an already damaged building - we have had them fail before on wood structures.
2. The anchors being installed at the time of the collapse were on the bootleg penthouse which has large unbraced spans across the large decks.
3. The structural drawings for roof anchors listed two concrete slab depths 6" vs. 8" - which was used for the calculations.

Emphasis mine. This is point were trying to make. 1250 lb load test from an anchor is not a lot of load/weight.

To add to this, the 1250 load test loads are typically performed in a manner that cancels out or creates the reactions locally. Insufficient to create catastrophic failures unless something more serious was occuring. They dont load test these things by dropping weights off the side of the building all at the same time. Thats not how the load test works. They also dont bring 1250 lbs and sit on the anchor. Also not how it works. Even with a 6" vs 8" slab, or the large unbraced spans, the 1250 lb point load is so inconsequently low, relative to the building loads that it would not surprise me if the same portion of the structure incurred a wind load from an afternoon thunderstorm several magnitudes larger than the forces were talking abou there.

From another article:

Quote:

In recent years, the American Concrete Institute and the Concrete Reinforcing Steel Institute (ACI and CRSI) developed an Adhesive Anchor Installer (AAI) certification program for horizontal and overhead installation of
adhesive anchors that are subjected to sustained loads. This program was developed to address many deficiencies related to installation of adhesive anchors into concrete substrates that could drastically reduce their load-carrying capacity. Although the adhesive anchors for the described condition are typically installed vertically downward, the authors recommend they be installed by a certified ACI/CRSI AAI to ensure quality workmanship.

Link

@RickyTickyTavi - even though the anchor testing you indicate is what YOU are experienced with, does not mean that was the testing performed on these roof anchors at this building. The drawings clearly call for load testing to 5000 lbs on individual anchors. Who knows what was actually done? Perhaps they misunderstood or ignored the drawings and tensioned a cable to 5000 lbs between anchor points in a setup similar to your photo. What if they did that same test all along the cantilevered portion of the roof? I can see that cracking the slab along it's length by inadvertantly pulling the tip of the cantilever up with the tension cable. Maybe they also ignored the GPR instructions and drilled/cored through a bunch of the cantilever rebar? If the roof cantilever did fail first, it would have dominoed all the balconies on each floor below, which would have been plenty of weight dropping to destroy the plaza slab.

Although I think warrenslo is incorrect on some of the details, I don't think their theory should be dismissed out of hand.

It's scary how many plausible explanations there are for this collapse. The "swiss cheese" risk model is already down to 10% cheese, and we've only just skimmed the surface of the investigation.

Quote (Spartan5)

Concurrent with the removal of debris, they towed at least two damaged vehicles away from the site. FWIW. Can’t say for certain they came from inside the garage.

I understand they are towing the damaged vehicles on the street to the north of the site in preparation for demolishing the remaining structure.

Quote (bones206)

If the roof cantilever did fail first, it would have dominoed all the balconies on each floor below, which would have been plenty of weight dropping to destroy the plaza slab.

And with nary a single 911 call from anyone about any of this.

Given all that was observed by the people who escaped while the progressive failure occurred from the bottom up over the course of several minutes, it would be a major anomaly for there to be no reports from the units above during the progressive failures of the balconies that would have preceded all of it.

Pancaking of the balconies starting at 1:10 or so when the first noises were heard on the ground just seems like a real stretch to me. More people would have gotten out or made calls if that was the case.

Quote (RickyTickyTavi)

Typically the load test is performed by testing, by tying two anchors together, then jacking them with a load meter until yes, 25 percent of the load is met. The 5000 lbs is an ultimate load, they are test loaded until 1250 lbs.

What is the point of load testing to 25% of the load you are rating it for? What does that prove? In my opinion all that test proves is that the anchorage is rated for exactly 1250 lbs with a safety factor of 1.0000. You can't just waive your hand and say that since it didn't fail at 1250 lbs, it must be good for 5000 lbs. What am I missing?

I find it intriguing if not improbable that a random TikTok video would reveal such dastardly evidence from the shadows, however buildings don't just fall down by themselves and a vehicle collision with a column has always been considered as a potential precipitating event. This vehicle would now be under considerable rubble given that the tower fell slightly to the south. It's not likely that an Einstein determined which column would take down the building but accidents do happen and disgruntled folk do exist. The story of the couple that moved into a motel and left their vehicle behind has me scratching my head.

Thanks for your responses.

Quote (AtomixPro)

As far as litigation goes or 'take away lessons', would a car hitting a column or a weakened roof/balcony element falling change anything? Neither should cause a building to collapse.

As far as litigation, who knows? My experience in much, much simpler cases is that everyone who possibly had anything to do with the loss gets sued. Then that gets narrowed down during litigation until they find the few parties most at fault with the biggest pockets.

As for 'take away lessons' I think it's our job as engineers to think of the unthinkable. If that thing has some reasonable chance of happening and making our designs fail, then we need to keep working. I agree that this building seemingly had huge latent problems of its own. A vehicle collision in a parking garage or improper drilling in a roof slab shouldn't collapse a building, but that fact that we're talking about it implies that it's plausible.

I don't think it's inevitable that huge problems have to turn into huge, catastrophic failures. Simple fixes might add a little bit of cheese to the swiss cheese and keep this from happening again: a little more impact protection to the garage, a little more care in placing roof anchors, a little more slope to the pool deck, a little more this, a little more that...

I think non-engineer decision-makers have a lot to learn too. Maybe it's time to rethink building high rises 50 feet from the beach. Maybe city zoning ordinances need to relax minimum parking requirements so we don't sacrifice shear walls for a few extra parking spaces. Maybe this was just a fluke and nothing needs to change. It's going to take a while to understand the implications of all this.

We don't know all the causes of this, but I think most of us agree it was a combination of many factors, some of which might actually be pretty cheap and easy to fix the next time around.

Bradley Wilder, P.E.
Construction P.E. (KY), MBA
Bridge Rehab, Coatings, Structural Repair

Quote (Spartan5)

Pancaking of the balconies starting at 1:10 or so when the first noises were heard on the ground just seems like a real stretch to me. More people would have gotten out or made calls if that was the case.

Maybe my logic is flawed. The upper cantilevers are longer than the lower balconies, so it's possible a portion could have collapsed that wasn't directly over the column of balconies. Not likely, but possible. It's hard to ignore the timing of the anchor installation if it was in fact installed and tested within 24 hours of the collapse. Just trying to keep an open mind.

Quote (bones206)

What is the point of load testing to 25% of the load you are rating it for? What does that prove? In my opinion all that test proves is that the anchorage is rated for exactly 1250 lbs with a safety factor of 1.0000. You can't just waive your hand and say that since it didn't fail at 1250 lbs, it must be good for 5000 lbs. What am I missing?

This a distinction between ultimate load and service load in the concrete and steel codes. I didnt make the rules, but the thought process for fall arrest systems are that they are only used once: When someone has an uncontrolled fall off of the building and their harness system catches them. The 'real' falling load is about 1250 lbs, but to account for different falling conditions, faulty construction, heavier set workers, possible factors unforeseen a 4x factor is applied and that is the design basis of the engineer. In sum, They are designed for 5000 lbs ultimate load and a 1250 lb service load. Basically the load factor is designed. Its similar nomenclature to how people have been talking about how the live load rating of the structure is 40 psf, or 100 psf (depending on the location) but those are service loads. When you apply the load factor, depending on the load combination, the actual design load can be 64 psf or 160 psf, respectively. Ultimate, vs service.

Quote (Sym P. le)

It's not likely that an Einstein determined which column would take down the building but accidents do happen and disgruntled folk do exist.

I would assume an accident. People drive drunk. Elderly drivers get confused and hit the wrong pedal. People get their foot stuck. In the middle of the night in the dark especially, none of those things alone would be surprising. Someone took out the stone planter and fountain at the entrance of my neighborhood this spring when they understeered the turn from the intersection. So yeah, accidents do happen.

Quote (Sym P. le)

The story of the couple that moved into a motel and left their vehicle behind has me scratching my head.

That sounded odd to me too, but I figured the hotel was close by and maybe only had paid or valet parking that they didn't want to pay for.

Bradley Wilder, P.E.
Construction P.E. (KY), MBA
Bridge Rehab, Coatings, Structural Repair

With respect to a collision in the garage bringing down the building. With each passing day in which we do not have a public statement addressing this issue the likelihood goes down. Right now, 8 days after the event, I'd say it's near zero. The first thing police are going to do is interview everyone in the area and pull all CCTV footage, much of which we've never seen, to determine if a crime was committed. And if there was any hint of individual(s) intentionally or unintentionally bringing down this building they would immediately hold a press conference to announce this news.

A few additional things I have noticed:

1. The "anchor" (fastener) detail for the "roof anchors" (fall protection) is mislabeled, it specifies carbon steel with a Hilti model number for stainless steel. Stainless steel is to be used in corrosive environments.

2. Roof structural drawings note 8" floor & roof slabs but cantilever detail at parapet show cantilever as only 6" slab (most likely to reduce weight.) Therefore, if the roof anchors were installed on the cantilever the slab would be 2" thinner.




3. The inspection documents uploaded by the city this morning end in 2019 (the end of the document is in the 1990s.) An HVAC unit appears to have been replaced in December 2019 and is the last record in the document provided.

RE: The "Swiss Cheese" model or, more accurately, slices of Swiss Cheese.

I don't think there will be any single factor that led to this collapse. I think it will ultimately be a series of factors all coming together at the worst moment.

In my view:

1. The first hole in a slice of Swiss Cheese is the Penthouse. Perhaps a contributing factor as it ate into safety margins but likely didn't, by itself, cause the collapse.

2. Second hole in a second slice: Corrosion/Lack of Maintenance/Improper Structural Repair. Again, unlikely to be the sole cause, but likely a contributing factor.

3. Third hole in a third slice: Overloading of upper parking area near the lobby. Not confirmed. Years ago I had experience with a parking structure on the beachfront in the Miami area that was showing signs of failure. The condo association contracted with an engineer that added steel supports at the top of the columns on the lower level to reinforce the slab against punching shear. Eventually someone recommended removing layers that had been added over the years when resurfacing the upper (exposed) parking deck. I figured that the structure had thousands of metric tons of extra weight on it. When resurfacing the upper parking deck, the condo association hadn't scraped the old layer off before simply adding new layers on top. Again, not likely to be the sole cause, but, if confirmed, may be a contributing factor.

Current hypothesis -
Top steel deterioration creates a hinge along Grid 11.1 near grids L to M (south edge of the planters).

- To the north, the plaza moment and some load redistributes to the building columns on grid 9.1. Because of the stepped slab to the building (the 30" tall beam would fail in shear at other locations), this moment into the building columns can be as high as 230 ft-k. The 8-#11 bars in the 16"x16" columns (excluding any consideration for concrete and compression) are good for 250 ft-k. I think it's reasonable to think that this extra moment could be what caused the structural cracking and popping noises experienced by witnesses. I figure the column would form a sine wave in the N-S direction.

- On the south side of grid 11.1 (the aforementioned hinge), load is redistributing onto columns at grid 13.1 with the slab close to yielding (I get 90 in-k/ft for allowable slab moment).

With top reinforcement deteriorated (I'd suspect the bars near the column to not be as deteriorated - high point but who knows), the 2 way shear capacity at grid 13.1 is reduced and punching shear occurs at these plaza columns which progresses suddenly to the majority of the pool plaza area failing those columns in punching shear and putting a shock load as well as significant slab moment (now unsupported due to failures at columns)on the column at grids K/9.1 (which has a small beam framing into it). This moment eventually fails that building column. And then the building.

Quote (The first hole in a slice of Swiss Cheese is the Penthouse.)

I would suggest the first hole, in the Swiss cheese, was the general deterioration of the concrete and reinforcing due to corrosion and criminal neglect.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

From a historical perspective, if we look at the L'Ambiance Plaza collapse in Brideport, Connecticut in 1987 (failure during construction using Lift Slab, with 28 deaths) there were no less than 6 (published) separate theories on cause of the collapse. The National Bureau of Standards (now NIST) was also involved with authoring a report on this collapse.

I think the correct interpretation of the specification is that 25% (that is 1 out of every 4) of the Hilti adhesive anchor bolts will be load tested to 5000 pounds. It talks about measuring the elongation in the anchor bolt during the test, which is something I don't think you could do if you were pulling on the post.



The anchor post itself isn't tested, but it's designed to withstand a 5000 pound pull in any direction assuming the individual bolts are installed correctly. The working load is only 1250 pounds, though.

To paraphrase LittleInch, More good evidence = better answers.
How can we get more surveillance views?

Has anyone heard how they are going to get the pets out (of the un-collapsed part), before demolition?

Thanks

SF Charlie
Eng-Tips.com Forum Policies

It looks like column I/12.1 was not built to be 24"x60" below 1st floor to carry the offset beam.

S4


S5

This is the typical adhesive anchor field tension test setup for individual anchors:

Thanks for that, Ingenuity (Structural)

October 2020 9-page Morabito report obtained by the Miami Herald, concrete testing “yielded some curious results”. But no mention of what it was or numbers etc. “exploratory demolition” in five locations. "Experts said they were struck by what wasn’t said."
source: Miami Herald

Well, as we suspected, there's my barricade I mentioned in the previous page of the thread...

Quote (DB27)

Good eye. I wonder if the beam was even there? Per the typical beam detail the top bars (2 #6) should have 180° hooks. I would think there would be major damage to both columns if those pulled out....

I'd be curious to see as built conditions at lobby level <K/14.1. The way the 14.1 beam connects to the column west of the 1' step at K.

Quote (SFCharlie)

Has anyone heard how they are going to get the pets out (of the un-collapsed part), before demolition?

Sadly, I fear the answer is they aren't, and the optics for that decision are going to be pretty bad - to say nothing of the optics of dropping the rest of the building on the undiscovered remains of the residents that didn't make it out. I hope I'm wrong though and something can be done.

The fire department has been feeding and watering any pets from balconies that have their doors open using their ladders:

https://youtu.be/G57mhnZWF_w

But because no sweeps are being done anymore there's no way to know which pets are still there and are still alive. It must be awful being in a building with no AC where the temps are 80-90 degrees every day.

Regarding pets: Link

Document received on June 29, 2021:

REPORT PREPARED BY THE HISTORIC PRESERVATION COMMUNITY

https://www.townofsurfsidefl.gov/docs/default-sour...

On page 8 there is a little different take on how the collapse occurred.

• https://files.engineering.com/getfile.aspx?folder=fe089f7d-7fd3-4b86-bc96-7

It's being reported on CNN that the mayor has signed an order for the remaining part of the building to be demolished. There's no time frame for that to happen yet, and the search and rescue effort will continue.

Yes, we all agree the structural plans are a mess, but I think the roof anchor plans are a mess too. This work was occurring the day of the collapse. So I continue to start there as the initial cause. Remember the Kansas City collapse was down to a simple bolt detail.

The reading of this note appears incorrect:


The 5,000 lbs. testing number doesn't make sense with the Hilti adhesive anchors.
HAS-V-36 et all is carbon steel and HAS-R is stainless steel and both have very different capacities at 5/8" dia.
Stainless steel should have been used due to being near the water but "carbon steel" was specifically stated in the note on the plans.
And, neither of them divide to any reasonable multiple of 5,000 lbs. for testing, but the OSHA rule does for the entire assembly including 4 x adhesive anchors do see below.


The OSHA Rope Descent System (RDS) Anchorage (not a fastener) needs to withstand 5,000 lbs. ultimate load in any direction.
In Florida rope decent systems are allowed in buildings less than 300 feet and above 300 feet if it is the only feasible method of access.
Rope Descent System (RDS) Anchorages must be tested before first use and at regular intervals.
IWCA/ANSI I-14.1-2001 Section 8.1.3 requires testing of twice the 1,250 lbs. design load in each primary direction or 2,500 lbs.

OSHA 2019 Testing Interpretation

January 25, 2019

Mr. Reg Ranahan
GSS Corporation
80 Hudson Road, Ste. 100
Canton, Massachusetts 02021

Dear Mr. Ranahan:

Thank you for your letter to the Occupational Safety and Health Administration (OSHA)[. Your letter has been referred to the Directorate of Enforcement Programs for an answer to your specific question] regarding 29 CFR 1910.27(b)(1)(i). [This letter constitutes OSHA's interpretation only of the requirements herein, and may not be applicable to any question not delineated within your original correspondence.] Your letter requests clarification of the requirements for rope descent system anchorages under 29 CFR 1910.27(b)(1)(i). Your paraphrased question and OSHA's response are below.

Question: International Window Cleaning Association/American National Standards Institute (IWCA/ANSI) I-14.1-2001 Section 8.1.3 requires that anchorages "be tested by applying a minimum static load of twice the design load in each (primary) direction that a load may be applied. For example, an anchorage with an ultimate capacity of 5000 pounds (2268 kg) has a four to one safety factor. Therefore the anchor's design load is 1,250 pounds (567 kg) and it shall be tested at 2500 pounds (1134 kg)." Under 29 CFR 1910.27(b)(1)(i), must anchorages be tested at 5,000 pounds, or is it permissible to test them at 2,500 pounds, as described in IWCA/ANSI I-14.1-2001?

Response: 29 CFR 1910.27(b)(1)(i) requires that building owners inform employers, in writing, that the building owner has identified, tested, certified, and maintained each anchorage so that it is capable of supporting at least 5,000 pounds, in any direction, for each worker attached. Certification of each anchorage must be performed by a qualified person. Because the OSHA standard does not specify criteria for testing anchorages, the qualified person may utilize any scientifically-valid testing criteria to determine whether an anchorage is capable of supporting at least 5,000 pounds (2,268 kg) per attached worker. In general, this means using criteria that would be accepted by an industry consensus group, or that are certified by a registered professional engineer. OSHA would consider the testing criteria described in your letter – wherein an anchorage with a 5,000-pound ultimate capacity/strength and a four to one safety factor with a design load of 1,250 pounds is tested at 2,500 pounds – to be acceptable under 29 CFR 1910.27(b)(1)(i).

Thank you for your interest in occupational safety and health. We hope you find this information helpful. OSHA's requirements are set by statute, standards, and regulations. Our letters of interpretation do not create new or additional requirements but rather explain these requirements and how they apply to particular circumstances. This letter constitutes OSHA's interpretation of the requirements discussed. From time to time, letters are affected when the Agency updates a standard, a legal decision impacts a standard, or changes in technology affect the interpretation. To assure that you are using the correct information and guidance, please consult OSHA's website at http://www.osha.gov. If you have further questions, please feel free to contact the Directorate of Enforcement Programs at (202) 693-2100.

Sincerely,

Patrick J. Kapust, Acting Director
Directorate of Enforcement Programs

[Corrected 4/17/2019]

My hypothesis continues to be:
The roof anchors were installed on the cantilevered sections of the roof (not per the plans, this is evidenced by actual installation on the remaining portion of the building.)
Then the fall protection anchors (either the entire assembly or only the adhesive anchor fasteners) were tested at much too high of a force (note on plans is unclear.)
This improper placement and testing then damaged the concrete roof slab above the penthouse over the x11 unit.
This concrete slowly failed through the evening, completely failing that night around 1 am causing the cantilevered portion and parapet to crash onto the pool deck and into the backside of column I/12.1
I/12.1 is the column with the unverified report of a possibly missing beam, and the column with impact damage to the backside according to the ENR report I posted a link to in a previous post.
I/12.1 shifted due to the impact that caused the guest parking and pool deck to fail.
The pool deck failed due to additional load and column damage causing the columns under x11 stack to fail.

Another note:
Morabito is the structural engineer and someone with that name works for the roof anchorage contractor - they are located within 20 miles of each other near Baltimore, MD and they both also have offices in South Florida.
I'm pretty sure they have a relationship.
The roof anchorage contractor appears to have been doing unpermitted work, they pulled their permit the day of the collapse.
With that said, I don't think we should rely on Morabito's statements at the current time.
I believe it's likely Morabito emailed the report to the city (they received it after the collapse) in an attempt to divert attention and cover up a roof anchorage mistake.

From a recent HOA letter:

Quote (Roga50)

Well, as we suspected, there's my barricade I mentioned in the previous page of the thread

I looked at https://gisweb.miamidade.gov/MDCPictometryIPA/pict...
(Switch to top view)
where you pointed out the barricade is on the West side of the square planter box sitting on M11. In the image it is the square planter on the right. The barricade was where I drew the rightmost red circle. DB27 pointed it out too. Left square planter is on L11.



Can anybody identify the three circled features, they were not there a year before.

I think the photo of lucky555 is from another place. The sun angle does not make sense. It’s morning or late afternoon, then eliminate when the building would cast a shadow. Also the pavers/tile and layout is different.

Quote (warrenslo)

The 5,000 lbs. testing number doesn't make sense with the Hilti adhesive anchors.
HAS-V-36 et all is carbon steel and HAS-R is stainless steel and both have very different capacities at 5/8" dia.
Stainless steel should have been used due to being near the water but "carbon steel" was specifically stated in the note on the plans.
And, neither of them divide to any reasonable multiple of 5,000 lbs. for testing, but the OSHA rule does for the entire assembly including 4 x adhesive anchors do see below.

Even though the note states "carbon steel", the HAS-R is stainless as you noted. If you specify HAS-R, they will (should) install HAS-R. If not, and an inspector catches it, they would be made to replace and relocate the anchors.

The Hilti design tables you are referencing (above) are only for the steel strength of the anchor. Steel strength rarely controls. Generally, pull tests (tension only tests) are used to test the anchor/adhesive bond strength, and the base material's (concrete) in-situ strength. 5000lb is roughly 90% of the design strength of this particular anchor in 3000psi concrete (roof slab), and the controlling limit state is concrete breakout. Steel strength utilization is about 40%. I suspect the 5000lb proof load for the anchor is not necessarily related to the 5000lb rating for the actual davit/anchorpost assembly itself.

I see what you're getting after, but I still find it very unlikely that anything dealing with these davits/anchorposts/whatever, had anything to do with the collapse.

Interesting. The picture in the Miami Herald article which shows the core samples seems to make it look like the feature on the right would be the core sample hole (neatly-cut, removed tiles in a square pattern). So that returns us to the question of what is the feature in the middle?



Yes, I realize that is a different hole, but one would assume they were all done the same way--not haphazardly like that damage/hole in the middle.

Now that they are paying attention, it has begun: evacuations of another condo deemed unsafe: Link

I wonder how they got 13" cores out of a 9" slab.

From what I understand (pretty much entirely from watching climbing bolt break testing) concrete won't start to crack until well over 35kN if properly set. A 5000lbf (22.2kN) test shouldn't do a damn thing to it. Of course if the concrete is already heavily corroded it could fail sooner, but I wouldn't call a 22kN test load "much too high a force" since that's the normal MBS (Minimum Breaking Strength) range for the less-strong parts of a (non-trad) climbing fall protection system (carabiners, slings, etc). Bolts are usually 40kN+ MBS.

NBC6 (one of our local stations here) just did an investigative segment where they were showing new documents indicating that the planters had severe drainage issues and drainage pipes (related to the planters) were replaced (I think last year) and it was also stated that the planters had no waterproofing at all.

I tried to find the video online, but so far it's only on local TV down here.

Isn't the Generator Room above the garage entrance, it was going to be replaced and the slab reinforced. Over the collapsed section in tiktok video? I wonder if the weight was accounted for in the original design.

What's the weight of the new roofing materials? I see one pallet still there on the remaining portion. Tarco is 72lbs/roll, 28 rolls/pallet for 2,016lbs, good for 3,024 sq. ft. plus barrels of bitumen or adhesive etc.
Were the roof anchors used that day when getting the roofing materials up there?

Generator: yes. It was located behind the louvers in the entranceway video with the broken pipe. (Fire pump and domestic water pumps in the same room per the plans) Leading me to believe that the broken pipe was the water main, which would have been in that vicinity.

I did see info on the replacement and apparently it was going to be replaced with a Kohler of a specific model, but no docs on what the original one was, so no info on weight comparisons. The plans did note upgrading the slab under the generator room to handle the new weight but did not detail what exactly would be done. I *ASSUME* that work had not begun because of no permits issued...

Here is a link to a news story regarding the Maison Grande Condominium.

Records show there have been five inspections that determined the building is an “unsafe structure.” The building envelope is among the list of concerns. There were also warnings that the two-story parking garage and pool deck “have reached the end of their useful life and require repair, replacement,” or “a combination thereof.”

Apparently building has been deemed "unsafe" due to structural deterioration 5 times. The building has a red placard that says "Unsafe Structure" placed there by the code enforcement department and a spokeswoman for the city says this:

“We use a red placard when a building violation is posted, which provides the language ‘unsafe structure’ per the County Code. This does not necessarily mean the building is unsafe or in imminent danger,” Melissa Berthier, a spokeswoman for the city, wrote in an e-mail on Tuesday. -

https://www.local10.com/news/local/2021/06/29/resi...

Sounds like a cover-up as to why an evacuation was not immediately ordered. I was always under the impression that an "Unsafe Structure" notice down here basically suspended your Certificate of Occupancy and the building must immediately be closed down for normal use. I was really surprised a when I saw that story about Maison Grande a few day ago. I wonder how many more there are? As I posted above, as we speak the city ordered the evacuation of YET ANOTHER complex due to them revisiting an inspection report and deciding it was unsafe. Wonder if it was red-tagged before today?

I'm getting the feeling it's gonna be really hard to find hotel rooms in Dade county for a while with all the condo's that are gonna be closed down...

Quote (Kreemerz (Computer)2 Jul 21 21:49

Just sharing this theory in animated presentation.

https://www.youtube.com/watch?v=hynHiWE818c

This engineer is going with the idea that the pool/patio deck collapsed pulling the beams toward the deck causing the main sections of the condo to come down.

Looks plausible but not exactly sure what caused the deck to collapse first)

This was posted in old thread after part 3 was started. Posting here in case anybody missed it.

250kW diesel generator estimate 6,000-7,000lbs plus fuel tank size. A heavy load and I see the slab and columns are ordinary. The collapsed beam looked under that room.
I wonder if the diesel was the stubborn fire. Generator uses about 64 gal/hr. and not sure of spec on how long they need to run.

I thought I read they were pulling out the underground tanks and replacing with natural gas...

Here's the video on the planter piping and waterproofing: Link

Quote (Torai)

Can anybody identify the three circled features, they were not there a year before

L-R

Towel

Woman stretching

Patch covering Test Probe A

I think the pool contractor on site days before would have noticed a gaping hole in the slab.

Another apartment complex in Florida has been ordered evacuated as a precaution after city officials became concerned over a recent report about the buildings:

North Miami Beach building deemed unsafe, evacuations ordered

A Jan. 11 report on the Crestview Towers condominium complex said it "was structurally and electrically unsafe."

https://www.nbcnews.com/news/us-news/north-miami-b...

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

The comments about the tests on the roof being 25% of each anchor at 5,000 lbs instead of all anchors at 25% of 5,000 lbs is very interesting.

At some point, doesn’t the slab act like a bow and arrow, so that it could be cracked if the two anchors are pulled together hard enough? What amount of force would it take to crack a 6” slab from two points 20 feet apart? Are we talking orders of magnitude more than 5,000 lbs?

It would be very interesting to know if and when this test was carried out.

...

I also think it’s premature to dismiss the broken roof theory simply because it wasn’t reported by any witnesses. It really wouldn’t have to be obvious to them.

How large an object would have to fall off the roof to cave in the pool slab? That’s the real question.

If you say the slab could have collapsed entirely on its own under its own weight, then any falling object whatsoever could have broken it. Could a single CMU do the job? A few hundred pounds? And a falling object wouldn’t necessarily need to hit every balcony on the way down. The roof cantilever is big enough that an object could easily clear every balcony.

At the starting time of the only video we have of the collapse, the rear penthouse parapet is unaccounted for. It can be theorized to simply have already started falling vertical, but as of right now, the video is not sufficiently clear to be able to say that. When that roof eventually comes back into view, as its folding over the collapsing stack, we can see what looks like a brand new coat - pure black, with no ballast on it yet.

A collapse of the rear penthouse, being recently worked on, and throwing a modest chunk of parapet wall off the edge, could have easily caved in the pool deck near unit 111.

Bystanders who ran out when the deck collapsed would not have seen a falling chunk of wall, nor would anybody on the ground have visibly noticed a collapse of a portion of the penthouse. Whether the floor of the penthouse could have survived the collapse of the roof, I can’t say. But nothing appears to disprove a rooftop event preceding the collapse.

FWIW...

https://www.dailymail.co.uk/news/article-9750461/V...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Quote (I wonder how they got 13" cores out of a 9" slab.)

easy... coring on an angle...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

If I’m not mistaken, the person who they were in verbal communication with was from unit 204, and would have been next to the generator and above the fuel tank. They could not save her because of the fire. The theory that the fire came from the generator and/or fuel tank sounds plausible.

Quote (Santos81)

Towel
Woman stretching
Patch covering Test Probe A

Plausible, looks like some other people walking around. Unfortunately the foliage in the planter hides the shadow which can reveal height/vertical profile.

For example, you can see which pool loungers are reclined up and which are flat.

Quote (Js5180 How large an object would have to fall off the roof to cave in the pool slab? That’s the real question.)

If a 500 lb (~250kg) HVAC unit were to free fall to the lobby level, it would hit with a force of 828,100 Newtons which would be about 186,164 lbs-f. I used this calculator: http://hyperphysics.phy-astr.gsu.edu/hbase/flobi.h....

I assumed a falling distance of 111 feet, which is 125 ft for the penthouse level minus 14 feet for lobby level or so. I assumed a stopping distance of 0.1 meter to maximize resultant force. Question: would the HVAC unit go right through the slab, or would it collapse it?

I don't know that there is any evidence that anything free fell onto the lobby level slab from the penthouse. Just figuring.

Just saw the new drop panel proposal shown by GPR_Tech post on 2nd July.

Not sure what benefit the remedial designers thought they were going to get from that!

There was very roughly 400 gallons of gasoline in the collapsed part of the garage, plus a fair bit of flammables in the debris.


spsalso

Quote (IEGeezer)

Question: would the HVAC unit go right through the slab, or would it collapse it?

I don't know that there is any evidence that anything free fell onto the lobby level slab from the penthouse. Just figuring.

If you're talking about a scenario of the big HVAC somehow falling off the edge of the building onto the pool slab (prior to the major collapse of the building), that's impossible. The big HVAC was on a support frame sitting on columns E2,H2,E4,H4. That is to the north of the elevator shaft and penthouse corridor. The penthouse corridor can be clearly seen in the collapse video as being mostly intact in its original location at the start of the collapse. It provides a solid barrier between the HVAC unit and pool slab, in addition to the implausibly large distance from the south parapet. The big HVAC unit falling probably could have triggered a collapse of the slab, but there's just no way that happened. It also would not have ended up on top of the rubble, roughly where columns I2 & I4 were.

A more viable theory involving falling objects would be the parapet from the roof of the south west quadrant of the penthouse. The disposition of that parapet is uncertain in the collapse video. It may be up at the top of the facade before the major collapse, or it's possible that it may have fallen down onto the pool/patio/plaza slab. The timeline for any possible fall is equally uncertain. If it did fall, it might have been mere seconds before the facade and major collapse, or it could have fallen minutes earlier and be responsible for collapsing the slab. We need the 15+ minutes prior to the major collapse from that CCTV camera, if it exists. There's no conclusive evidence right now around the parapet (or the cantilever section of roof).

Quote (Torai)

Plausible, looks like some other people walking around. Unfortunately the foliage in the planter hides the shadow which can reveal height/vertical profile.

In all seriousness, without better resolution images of the area, identification of the west and center areas of intrigue with certainty is difficult. The east anomaly is the patch/temp cover for the Windsor Probe Test. Thinking back on some previous experiences in the area with some of the same characters in this story, the center is probably a black cleanup bag stuffed in the bore hole and spread out with sandbags around the perimeter. There may or may not be a plug fitted, but it wouldn’t really make any difference. To the west, additional sandbags as that planter wall is really just a step.

I may have missed it in the earlier threads, but has anyone caught on to the fact that planters in the pool area have been significantly enlarged at some point in time?

Those punch test result images in the planter areas are, well, curious.

Quote (Js5180)

The roof cantilever is big enough that an object could easily clear every balcony.

THe Penthouse and 12th floor roof extend over the two windows where the collapse appeared to start.

Quote (Js5180)

When that roof eventually comes back into view, as its folding over the collapsing stack, we can see what looks like a brand new coat - pure black, with no ballast on it yet.

The roof over the penthouse is brand new roof paper in photos post-collapse.

{quote IEGeezer]If a 500 lb (~250kg) HVAC unit were to free fall to the lobby level[/quote]
The large HVAC unit moved to be over the remaining building in 2019 flipped over due to supports of its steel frame failing and was on the top of the pile upside down several floors up.

The residents were complaining about the structural engineer who seems to be related to the roof anchor contractor 3 days prior to collapse in this email:


My concern is Morabito Consultants would recommend demolishing the remaining building to eliminate any evidence. Due to the transfer slab on the second floor, I believe most of this building is stable with enough shoring. It was stable enough to resist progressive collapse. Most of the shear seems to be in the remaining building. In my opinion, they should have shored the accessible parts of this building on day one.

As the inspection records the city has posted only go to 2019, I have sent this to the city. If the anchors installed that day were over x11 stack we have a very solid hypothesis.

Sorey asked for an audit and review of all high-rise condo buildings above five stories to determine if they were in compliance with the county and city 40-year recertification process and certified as safe for occupancy on June 29.

After department files showed Crestview was not in compliance, an inspector went to the building on Friday to follow up.

That same day, the Crestview Towers building manager brought a recertification report dated Jan. 11, 2021, to the North Miami Beach Buildings Department, where the association’s engineer deemed the property unsafe.

Wait, what? Am I reading this correctly? The association's engineer deemed the Crestview building unsafe in January?

https://www.nbcmiami.com/news/local/north-miami-be...

Mayor authorizes demolition of remaining units at Surfside condo collapse site as death toll grows to 22

Quote:

Wait, what? Am I reading this correctly? The association's engineer deemed the Crestview building unsafe in January?

Is there a mechanism (or better, REQUIREMENT) that when an engineer sees conducts an inspection and identifies a building that is unsafe, they can immediately go to the city and get the building red-tagged and closed? (if not, there should be IMHO...) From the things we're seeing down here, it seems like the answer is either No, or it's not being enforced (or the inspectors are being ignored)

Quote (warrenslo)

My concern is Morabito Consultants would recommend demolishing the remaining building to eliminate any evidence.

Morabito has no say in the matter. It’s still an active search and recovery mission with multiple Federal, State, and County Investigations in the early stages. Until it’s forensically cleared and evidence taken to the secure location, the site must be viewed no different than any other mass casualty crime scene. This includes FOIA requests. Until they’re deemed no risk to any investigation, they won’t release them.

Quote (hokie66)

I wonder how they got 13" cores out of a 9" slab.

Drilling took place up to a foot down in order to determine the structure of the concrete below. The work 'yielded some curious results as it pertained to the structural slab's depth' - but the reason as to why the results were 'curious' was not explained

https://www.dailymail.co.uk/news/article-9750461/V...

Warrenslo - definitely looking more at the parapet(s) although it’s hard to rule out an HVAC unit as the round object in the garage debris.

The parapets have the mass, they are likely to be minimally reinforced CMU, and they’d come off easily enough. Looking at the ones on the ground and they are generally broken into fairly small parts, far removed from their roof slab which stayed mostly intact. And you are right - the only balconies under them were the 12 and PH.

Also, at the time of the collapse, the upper x11s are the only units with lights on. That could be a coincidence, or not.

Still, I’d like to better understand what kind of force on the roof it would take to break a 6” slab, either with dead load or an anchor test.

Finally, as far as the covering the evidence, I suspect there are a lot of parties who’s litigation chances improve if the building is demolished. I’d expect the plaintiffs’ lawyers to seek an injunction delaying the demolition, provided the building survives the next storm.

Quote (GPR_Tech (Civil/Environmental)2 Jul 21 16:16
Does anyone know what columns were slated to be reinforced with new Drop Panels?
(Note #10 on Drwg S2C-1.0) calls for new Drop Panels.)

Regarding the new column caps to be installed/constructed under he existing pool deck slab - -
Does anyone else have a problem with backing up an overstressed 9.5 inch slab with 4 inches of new (fresh) unstressed concrete?
Seems to me the action from here out will be an increase in stresses in the existing questionable slab and the initial buildup of stresses in the added 1 FOUR inch slab beginning at zero.
Then there is the possible difference in the elasticity of the old concrete and and that of the new fresh concrete. So for a while most of the loads will go into the existing slab - and little will go into the new concrete. Splitting hairs there, it seems.
Consider also what drilling under the slab at the first column which failed last week could have caused. Not a good place to be.
Was shoring of the slab required during the installation of the new 4 inch concrete cap? Would that be gunite concrete on the overhead? Bore a hole and feed thru from above?

I dunnoo - - - 'bout this idea.
I see rapt (Structural) caught it.
https://www.townofsurfsidefl.gov/docs/default-sour...

On the demolition and stability of the remaining structure, there are some serious signs that the structure is unstable. On the south end, those columns that lost the lobby/parking slab are a problem. There are also 3 or 4 floor slabs low down at the north end that are visibly sagging down and probably detached from column E2. The elevator tower will help a lot, if there's no hidden damage to it, and the slabs are still firmly attached to it.

I would not be confident about its performance in a storm. At a minimum, I think they need to tidy up the ragged north east section, removing the remaining big bits of dangling material.

Here's a layman's view of the list of "improvements" that the condo they just red-tagged are supposedly undergoing... Link

Other than the generator (ie, elevators not having backup power), I don't see them mentioning anything too serious (so what are they ignoring?) Doubt they'd red-tag the building just for that rather than just close the elevators (which has happened several times down here with older condo's in the past).

Quote (Js5180)

although it’s hard to rule out an HVAC unit as the round object in the garage debris.

One of the round objects is the marquee on the vehicle gate. The other roundish object down in the debris field is possibly the patio furniture from 111. It’s hard to see but the pedestrian gate for the terrace of 111 appears to be just inside the right arc.

My working hypothesis (for now) is that the precipitating event occurred at or near the 111 planter (the bushes seem to be visible in the TikTok video). Either the slab beneath the planter gave out from the combined effects of corrosion and neglect (perhaps related to that hole/damage visible in the overhead pic) or the column beneath it collapsed somehow. The collapse then spread to the rest of the pool deck, I would imagine similar to this:

https://m.youtube.com/watch?v=6ssbowQjH4A

I wonder how consistent this failure pattern is. Would this mean that the more distant pillars will usually have columns puncturing the slab, but the slab nearest the failed pillar would break across its entire width? That would suggest that the upper parking deck failure happened first, as that’s the only part we know of where the slab “hinged” rather than punctured.

Edit: scratch that. It looks hinged because it’s resting on cars.

Quote (Santos81)

the center is probably a black cleanup bag stuffed in the bore hole and spread out with sandbags around the perimeter

Actually probably is a person as you first suggested. The picture was probably taken at 10:39 when the sun azimuth was 149° (By rotating image and looking at angle) and at 37° elev. Object height will be 0.60 * shadow length.
https://gml.noaa.gov/grad/solcalc/azel.html

This is slightly Northeast on one of the paths near the beach. Two people. Another nearby (not this image) probably walking a dog. The white band around the dark person is probably an image compression artifact.


Gets more fun with radar images; you can sometimes see metal inside structures from far far away.

It does sound like punching shear was a factor, as there were plans to add to the slab thickness at some columns. Whether that scheme would have overcome the punching shear susceptibility is questionable at best. One thing I would look at with the pieces of columns remaining is evidence of effective slab depth at the columns. A favorite builder's trick is to pour columns a bit high to simplify floor formwork, and that can drastically reduce punching shear capacity.

One has to wonder - with so many columns punching through, was it really a column failure at K/L-9.1/10? This would suggest that only three columns were seriously degraded, but the slab everywhere else was.

Quote (OSUCivlEng)

Drilling took place up to a foot down in order to determine the structure of the concrete below. The work 'yielded some curious results as it pertained to the structural slab's depth' - but the reason as to why the results were 'curious' was not explained

People have been joking about the slab depth but it was as follows:
1-1/4” Pavers on sand waterproofing
1-3/8” Tile & Mortar
2-1/8” Concrete Topping
9-1/2” Structural Slab

I’m dumbfounded that an engineer would leave a cliffhanger inside one of their reports… unless they are leading the way of engineers using the subscription model???

Quote (bradw1128 (Civil/Environmental) 2 Jul 21 18:10)

I would assume an accident. People drive drunk. Elderly drivers get confused and hit the wrong pedal. People get their foot stuck. In the middle of the night in the dark especially, none of those things alone would be surprising.

Agreed.

Quote (TheGreenLama (Structural) 2 Jul 21 18:19)

You have more faith in the system than I do but I hope they haven't overlooked anything.

Quote (aggualaqisaaq (Nuclear) 3 Jul 21 03:26)

One of the round objects is the marquee on the vehicle gate. The other roundish object down in the debris field is possibly the patio furniture from 111. It’s hard to see but the pedestrian gate for the terrace of 111 appears to be just inside the right arc.

The roundish object is likely an object in front of the vehicle. The reason I suspect a pickup truck is the square box that abuts the "broken column" (if that's what it is). The roundish object could be the wheel well or not.

What is missing in the frame grab is the column at the back of stall 27 which is why I pose the hypothesis that the two concrete peices bent over the back of the vehicle are the remains of that column.

Additionally, if the slab dropped into the parkade, I would expect a notable depth of debris on the parkade floor but I don't see that.

Fair game on calling whether the vehicle is parked sqaure in the stall or not. At any rate, I hope it is useful to post my suggestion as to what the image shows and its positioning beneath the pool slab/building footprint. I didn't expect to get that much out of this little project. I only did one frame and perhaps other frames can lend more clarity but of the ten frames that I glanced at, this one seemed to offer the most clarity.

Quote (aggualaqisaaq (Nuclear) 3 Jul 21 03:26)

https://m.youtube.com/watch?v=6ssbowQjH4A

A chilling animation of what likely happened, and worse. The animation is likely predicated on sound (but marginal) column caps. From the images of the actual collapse, the column caps or what was left of them (after corrosion) were minimally provisioned and gave up without a fight, ergo, after the first column or grid line gave out, the remaining slab came down as one piece.

Alright.

Need some help. I'm working on...something...

I am soliciting everyone's best guess at the dead loads on the: pool deck, lobby, parking (lobby level), typical residential, and roof. Kindly note, I'm looking for dead loads as described by ASCE 7 / IBC. Not subjective live loads (such as "I consider tile = live load). I will be using live loads as required by ASCE 7-16 for now.

Here is the inspection report for the Crestview Towers condo that was red-tagged and evacuated tonight: Link

Further evidence of the initial collapse in the garage. On the left entrance wall of the garage, there is a reflection of flashing vehicle emergency lights.

I have attached the “enhanced” clip below:

https://res.cloudinary.com/engineering-com/video/upload/v1625292979/tips/trim.369046FC-DCF4-4D56-9ABC-FA2B578C3978_tm2dmw.mov

Quote (Mayor authorizes demolition of remaining units at Surfside condo collapse site as death toll grows to 22)

Is this a crime scene? and are they destroying evidence?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

NIST Will Conduct Technical Investigation Into the Collapse of the Champlain Towers South Condominium, The investigation could take years, lead to recommendations for building code improvements. NIST News, June 30, 2021

Quote (https://www.nist.gov/news-events/news/2021/06/nist...)

The team found that the collapse met necessary criteria to invoke the act: It was a “major building failure at significantly less than its design basis, during construction, or while in active use.” In addition, NIST determined that “a fact-finding investigation of the building performance and emergency response and evacuation procedures will likely result in significant and new knowledge or building code revision recommendations needed to reduce or mitigate public risk and economic losses from future building failures.”

I think that NIST's initial finding of the collapse meeting the criteria for an investigation by the National Construction Safety Team Advisory Committee is well established. This should alleviate some of the concerns related to preserving evidence.

Quote (https://www.nist.gov/disaster-failure-studies/cham...)

On June 25, NIST began deploying a team of six scientists and engineers to collect firsthand information on the collapse. Since then, NIST experts have been working with federal, state and local authorities to identify and preserve materials and information that might be helpful in understanding why the collapse occurred.

Link to the NIST Disaster & failure studies page for the National Construction Safety Team Advisory Committee.

NIST Disaster & failure studies Champlain Towers South Collapse

Quote (Sym P. le)

The roundish object is likely an object in front of the vehicle. The reason I suspect a pickup truck is the square box that abuts the "broken column" (if that's what it is). The roundish object could be the wheel well or not.

What is missing in the frame grab is the column at the back of stall 27 which is why I pose the hypothesis that the two concrete peices bent over the back of the vehicle are the remains of that column.

The site seems to not like me. I’ve twice composed an extremely thorough reply and hypotheses but find myself logged out automatically by the time I get to submit.

In the mean time to be brief:

The vehicle in bay 27 is a SUV (possibly a Ford Explorer) positioned head in. The square box is a planter from outside 111, but I’m not convinced it’s the one in cluster positioned directly above the column that is no longer visible. I think it may be the one to the west.

I don’t see a failure of the pool deck occurring first; rather a slow column shear failure below the pool deck that is made unusual due to the already deteriorating structure and pendulum behavior of the planter as it separates from the slab. This generates a non-linear alternate load path that spreads out in an almost circular motion. Of the elevated pool/plaza deck, the parking area seems to be last portion to fail but the load is still continuing back through the superstructure at the lobby level until it too cannot carry more.

I’ll elaborate after some rest. In the meantime, short of DoD Shock Tests, or an intentional demolition, it would be shortsided as professionals to look at this as anything resembling typical or simply explained. That method did not bode well for those at the start of this tale.

To sign off with a moment of levity

Quote (Hokie66)

I wonder how they got 13" cores out of a 9" slab.

Definitely used a Men’s Tape Measure. Women’s would have been an inch short.

Has the more recent (2020?) Morabito report that the media has referred too been made publicly available yet?

There is a significant amount of debris missing where the first collapse section appeared to drop straight down. It should be piled up three or four stories deep like the rest of the pile.



Also,some interesting items atop the debris pile. The northeast stairwell wall (I believe a section of five of the uppermost floors) landed about 100 feet from its origin.

Strings of column sections (a total of ten make that nine, in one string) all detached from the slabs and apparently falling over as a single item.

Quote (Sym P. Ie)

There is a significant amount of debris missing where the first collapse section appeared to drop straight down. It should be piled up three or four stories deep like the rest of the pile.

I believe a significant portion of the south side may have collapsed slightly northwards. If you study the collapse video closely, the southwest quadrant of the penthouse and access corridor appear to hinge downwards on roughly the 4 line of columns (the north side of the corridor on all floors). If that was representative of most floors, the slab hinging on the 4 columns, the debris pile would be moved a little to the north.

North Miami just ordered evacuation of 50 yo Crestview Condos 7 miles north of this one. https://www.miamiherald.com/news/local/community/m...

I have looked in detail at the original plans and it looks like they changed the foundation from precast concrete piles (50tons each)at 3ft spacing to “PIF” at 150 tons with a much greater spacing but it does not appear that they added more reinforcement to the pile caps to account for the additional bending and shear introduced by this change. It seems odd to me that no one is discussing the foundation pile cap design and this change which is an obvious red flag. The significant lack of ductility/redundancy as evidenced by the extent of the collapse strongly suggests the root cause is a flaw in the initial design.

Quote (JohnRBaker)

Another apartment complex in Florida has been ordered evacuated as a precaution after city officials became concerned over a recent report about the buildings:

North Miami Beach building deemed unsafe, evacuations ordered

A Jan. 11 report on the Crestview Towers condominium complex said it "was structurally and electrically unsafe."

https://www.nbcnews.com/news/us-news/north-miami-b...

Quote (Phil1934)

North Miami just ordered evacuation of 50 yo Crestview Condos 7 miles north of this one. https://www.miamiherald.com/news/local/community/m...

Likely all PR moves to show the public that we're listening & we care too. Puts customers at ease, or so it's intended to.

Quote (Js5180)

One has to wonder - with so many columns punching through, was it really a column failure at K/L-9.1/10? This would suggest that only three columns were seriously degraded, but the slab everywhere else was.

Yeah indicates that the soil they sit in was not as unstable as I first thought. This is why I'm leaning away from any sinkhole possibility.

Quote (Hokie)

I wonder how they got 13" cores out of a 9" slab.

That’s why we factor up the dead load.

Quote (warrenslo)

The roof anchors were improperly installed on the cantilever portion of the rooftop slab in the portion of the building that did not collapse

Quote (warrenslo)

They installed nearly all the perimeter anchors on the cantilevered portion of the roof slab - not per the structural drawings.

Looks as though most of the perimeter anchors were supposed to be mounted on the cantilevered portion....per the structural drawing.

I found this article that was interesting. It gives some insight on why the construction timeline of the sister buildings is what it is. It also talks briefly about the penthouse an explains why it was added and removed.

In South Florida, developers often demand exceptions to rules. Champlain Towers got several

https://www.miamiherald.com/news/local/community/m...

Quote (Lizard7709)

I found this article that was interesting. It gives some insight on why the construction timeline of the sister buildings is what it is. It also talks briefly about the penthouse an explains why it was added and removed.

In South Florida, developers often demand exceptions to rules. Champlain Towers got several

https://www.miamiherald.com/news/local/community/m...

Interesting angle to be taken by Miami Herald, but I guess I'm not surprised to see that from them... South Florida, developers often demand exceptions to rules... this is a relative statement that's nothing more than a newspaper opining on this tragedy.

They come off sounding like they have something against developers from South Florida. Strange article.

Controlled Demolition is planning to drop the building Sunday if finished with preparation by then in advance of potential storm.

Quote (MOJOJOHN (Structural))

Controlled Demolition is planning to drop the building Sunday if finished with preparation by then in advance of potential storm.

Wow!! Yesterday they were saying it would take weeks, but now it may be tomorrow. It must be in much worse shape that they thought earlier. This is the best of the terrible options, though. Too bad that we may never learn the real cause of the collapse.

It will be interesting how they do it, and how it comes down. Hope there is some good high resolution raw video, with good sample rate and without compression and other artifacts.

For the engineer's report on the Crestview Towers Condo that the city just closed for safety, it's weird that the report is dated as 1/11/21 and yet it is stamped received by the city yesterday, 7/2/21. Looks like they are scrambling to cover their butts. Wonder how many more may get shut down?

Quote (This should alleviate some of the concerns related to preserving evidence.)

You have more confidence in government agencies than I do, I guess... even the FAA was flakey.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Fire Official: Demolition to Collapsed Condo to Start Sunday

https://www.nbcmiami.com/news/local/demolition-to-...

Quote (They come off sounding like they have something against developers from South Florida. Strange article.)

There's a sleazy ugliness there...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Recent on-site drone video of the cleanup process.

https://youtu.be/srvWVvM1YPA

Quote (kreemerz)

Just sharing this theory in animated presentation.

https://www.youtube.com/watch?v=hynHiWE818c

This is an interesting animation and take on collapse mechanism. Earlier in thread people were suggesting (at least this was my interpretation) that pool slab may have failed along exterior building column line, dropped, and pushed horizontally on column. This animation offers an alternate hypothesis. That most of the deck slab failed successively in punching shear, with the slab remaining intact and still connected to the exterior column line. Then, through catenary action, the slab dead load pulled on that column line causing failure.

Back when this building was built was "integrity reinforcement" (bottom rebar to resist punching shear) required in parking garage slabs?

Not that I'm aware of... For narrow rectangular columns, I always added a couple of 25M (#8) bars bottom in the narrow direction... just my practice back then.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

For the roof loads, I estimate qty. 150 of 3-ton A/C units (in groups of a dozen) plus a couple cell repeaters and electrical panels. That looks like 33,000lbs of add-ons distributed across the roof. Then there's the penthouse. I did not look at the main rooftop unit weight for cooling the common areas. Half the units fell in the collapse.

I think it's obvious the building's height was a developer's and thus engineering issue, the reason for not sloping the decks and possibly having a low parkage floor, and other compromises.

Rebar insufficiency may be the root cause of collapse.

https://www.nytimes.com/2021/07/03/us/florida-condo-collapse-steel-rebar.html

I'm pretty sure the first image behind the paywall shows this view, which was posted in the first part of this thread:

Quote (Retiredat46)

I'm pretty sure the first image behind the paywall shows this view

Actually, you can view a limited number of articles behind the paywall without having to pay so most readers can go read the article.

As suspected, the city is rushing like hell to have the demolition done. I hope those lawyers file an injunction. Corruption down here at it's best... Now trying to destroy the evidence, as some have stated above...

Quote (lucky555)

For the roof loads, I estimate qty. 150 of 3-ton A/C units (in groups of a dozen) plus a couple cell repeaters and electrical panels. That looks like 33,000lbs of add-ons distributed across the roof.

The A/C condensers were there on the original 1979 plans, so hopefully would have been included in the original load engineering. Similarly for the big HVAC unit, although it did change from spanning 4 D–E columns to spanning 4 E–H columns in a revision during the original build. The modern replacement for the big HVAC just consolidated two separate units into a combined unit on the same frame, spanning the same columns.

Quote:

Wow!! Yesterday they were saying it would take weeks, but now it may be tomorrow. It must be in much worse shape that they thought earlier. This is the best of the terrible options, though. Too bad that we may never learn the real cause of the collapse.

What's in "worse shape" is several city officials' chances of staying out of prison if that building remains standing. It's the South Florida way.

That storm will do very little... We've seen many storms like this before, of similar strength and similar storm track, where we don't even get rain or a light breeze. The storm is an EXCUSE. I hope the news media starts asking questions. If they want to make these decisions, they need to be stepping aside and let a third party not related to the situation call the shots. And NOT DeSantis (who is the most corrupt governor in Florida history).

Quote (dold)

A couple comments on your model:
- Adjust all balconies for the curve.
- Adjust level 12 and Penthouse balconies they are different.
- At x12 the balconies are different starting at floor 9.
- You are missing the step in the slab between the building and pool deck.

Quote:

Actually, you can view a limited number of articles behind the paywall without having to pay so most readers can go read the article.

Depending on the site (Miami Herald is one of them), you can just delete the site's cookies if the paywall starts asking you to log in, and then close your browser and hit the site again.

Quote (Roga50)

That storm will do very little... We've seen many storms like this before, of similar strength and similar storm track, where we don't even get rain or a light breeze. The storm is an EXCUSE. I hope the news media starts asking questions. If they want to make these decisions, they need to be stepping aside and let a third party not related to the situation call the shots. And NOT DeSantis (who is the most corrupt governor in Florida history).

I agree, looks like a cover-up. Why no more info on the roof inspection less than 24 hours prior?

The remaining building is solid - it's still standing - with debris removed and the one column with major damage to the backside shored and braced. Most of the remaining columns from floor 2 to the ground are oversized with transfer beams.

As a subscriber, I'm allowed to share 10 articles a month, here's #1
Condo Wreckage Hints at First Signs of Possible Construction Flaw
Go for it...

SF Charlie
Eng-Tips.com Forum Policies

Quote (TheGreenLama)

Back when this building was built was "integrity reinforcement" (bottom rebar to resist punching shear) required in parking garage slabs?

Only #4@12" bottom steel each-way is provided except for the end span; for the end span addition #4@12" are added (see clip below).

Quote (TheGreenLama)

That most of the deck slab failed successively in punching shear, with the slab remaining intact and still connected to the exterior column line. Then, through catenary action, the slab dead load pulled on that column line causing failure.

There are substantial shear walls holding the upper ground floor slab against the catenary action and all the tower columns are tied to the ground floor slab, but looking at the drawings in detail, I think the catenary action may have caused the failure of the exterior tower columns without engaging the shear walls.

See the second clip below, the slab step beam will be subjected to massive torsion when the podium slab fails and the torsion will be transferred as excessive flexure on the exterior columns.

Quote (dragon6172)

Looks as though most of the perimeter anchors were supposed to be mounted on the cantilevered portion....per the structural drawing.

This is very very interesting, because they weren't supposed to be on the penthouse.


Penthouse anchors had just been installed, look at that fresh roofing paper.


Closest to the guest parking and damaged column, the 12th floor or penthouse roof is near the bottom of the pile, not top.

Quote (OSUCivlEng (Civil/Environmental)3 Jul 21 15:25)

Fire Official: Demolition to Collapsed Condo to Start Sunday

So they waited until it was too late to get a court injunction, and moved it up to tomorrow.
I hope some people will have the courage to get the pets out, let alone their passports wallets purses...

Who could blame them if they occupied the building site.

SF Charlie
Eng-Tips.com Forum Policies

Governments NEVER move this quickly on any decision unless it is to protect themselves from prison time...

Quote (warrenslo)

This is very very interesting, because they weren't supposed to be on the penthouse.

Those anchor points labeled P15, P16 and P17 are all on the cantilevered portion of the penthouse roof.

Quote (Roga50)

As suspected, the city is rushing like hell to have the demolition done. I hope those lawyers file an injunction. Corruption down here at it's best... Now trying to destroy the evidence, as some have stated above..

Governments NEVER move this quickly on any decision unless it is to protect themselves from prison time..

The biggest priority here is the safety of the USAR teams and others in the area despite what you and many others think. These people are working under extreme conditions trying to find the remains of victims for their families. They are risking their lives trying to do this. Having an unstable structure next to them has to be on their minds constantly. Dropping that remaining section of the building will do nothing to protect public officials or others who are responsible for this problem.

CNN just showed some video of work going on in the parking garage. Two columns each had at least a dozen large shoring devices in place around them. Also shown were two workers with what looked like surveying equipment.

Quote:

The biggest priority here is the safety of the USAR teams and others in the area despite what you and many others think. These people are working under extreme conditions trying to find the remains of victims for their families. They are risking their lives trying to do this. Having an unstable structure next to them has to be on their minds constantly. Dropping that remaining section of the building will do nothing to protect public officials or others who are responsible for this problem.

Then all they need to do is declare the "rescue" over and turn to "recovery" which we all know is the truth. Then let the REAL work start, such as preserving evidence. There is no rush in that...

As some have stated here, that building probably can be shored-up. What we have here are politicians trying to shore-up their futures (we see this a lot in Florida, and Dade County leads the way with the most corruption in the state).

For instance, have any CCTV videos been recovered from inside the building? The security office is in the uncollapsed section. Afterwards, they will state that they must've been damaged during the demolition--so sorry...

What about other records kept onsite in the offices in that building (again, mostly in the uncollapsed sections near the elevators).

Our officials here NEVER move this quickly... That in itself is highly suspicious.

Has anyone here addressed how it could be that there are no car alarms sounding in the tiktok video of the supposed collapsed garage deck??

Do you have any actual evidence that this demolition is part of a “cover up”? If so, please do share. I’m all ears…

But keep in mind that things like suspicions, hunches, conceivability, feelings, “I’m just asking questions,” “…but shady things happen all the time in _____,” etc. do not count as evidence for anything—-aside from overactive imaginations.

It's simple. Get those who have a conflict of interest out of making decisions on this demolition. From what we are seeing, all of those calling the shots stand to wind up in a court room as a defendant (or being a friend of those who are). Let uninvolved engineering parties call the shots. There is no harm in that. Why is this not being done.

Anyone who lives down here knows just how corrupt these government groups in Dade county are.

In a murder trial, you do not ask the defendant what evidence should be preserved.

Government officials are in a downright PANIC regarding this thing down here (unless you are here you may not see it). We also have tons of experience with storms like Elsa--it looks worse on the media than it actually is. Closing a building for inspection results from 7 months ago should be all the evidence you need... How many more are there? Was Champlain Towers one of them?

Quote:

CNN just showed some video of work going on in the parking garage. Two columns each had at least a dozen large shoring devices in place around them. Also shown were two workers with what looked like surveying equipment.

See this is the problem, they need to weaken the columns from west to east to have the implosion take the building west. But the weakest damaged columns are on the eest. So once you take out the columns on the west all that's left is the middle of the building. At that point it's a real lottery if the building falls towards the west (preferred) or East. Furthermore taking the building west like they want will damage sewer and water lines within Collins. And finally, the asbestos cloud is an issue, are they going to wrap the building?!?

Quote (bones206)

Those anchor points labeled P15, P16 and P17 are all on the cantilevered portion of the penthouse roof

P16 is on top of a column. P15 and P17 are between columns. See the column anchor on the left side of the penthouse (that anchor also could have been the failure point.)

Correction, P15 & P17 are also shown on top of columns, typically these are installed between columns, so this is odd.

“In a murder trial, you do not ask the defendant what evidence should be preserved.”

Right, but how do you know what has or hasn’t been preserved thus far?

It’s impossible to say one way or another because not every detail of an investigation like this immediately gets released into the public domain, especially if criminal charges may be involved down the line.

“Closing a building for inspection results from 7 months ago should be all the evidence you need”

This is certainly evidence of incompetence, bureaucratic dysfunction, negligence and possibly even a sign of corruption or undue influence of private interests on local government…but not necessarily of any kind of “cover up.”

The root cause analysis study could have major implications on many ( most?) seaside condos in the US, and that implies there could be major economic / political pressure to place the blame on the isolated roof repairs, so as to limit the financial exposure of the many existing condos. It is constructive that NIST is now involved, and that may provide more credibility to the resulting report, as it implies that the only political adjustments to the report would be thru the specific reps and senators that oversee NIST.

It is hoped that one result of the tragedy would be to move the responsibility for large building inspections away from the local town and to the county. Local mayors and councilmen are a bit too responsive to the entreaties of the developer.

As of this time, the main surprise is how well the different govt agencies have responded in a complimentary manner- the system seems to work well when a polarizing political issue is not involved.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

The chance of them receiving 50 Knot winds is less than 10%, 34 knots less than 20%, and How is the danger to the heroic rescuers (Yes they are heroic!) any more from a 34 knot wind than a demolition (demolitions never go wrong).
(and if people can go in to set charges, why can't they bring living pets out?)

SF Charlie
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BBC is reporting that an occupant on the 11th floor witnessed such a violent boom that the walls and chandelier were quaking, and a sound like a freight train rushing by:

https://www.bbc.com/news/world-us-canada-57690165

They said they looked LEFT down the hallway and saw the roof slanted in.

The only unit that someone leaving could look left at the damaged section would be unit 1104. The living room of 1104 appears to be intact.

The timing of when they left their unit isn’t clear, but the initial boom they describe sounds a lot more extreme than a slab falling in the garage, especially since they are on the opposite side of the building.

Their account is not inconsistent with a roof event as the initial boom.

This building was 40 years old which is 14,600 days, but this collapse happened the day after a crane was loading roofing materials on the roof and the day after fall protection anchors were installed. The parapet detail Warrenslo posted has a 5'-6" cantilever, but when analyzed the moment hinge point should be center of support which is about 5'-10". The slab is only 6" thick and the reinf only #4@13" oc. Using structure dead loads plus 10 psf for roofing material and 30 psf for live load, the factored moment is 4.08 k-ft/ft and the factored capacity is only 3.99 k-ft, so assuming perfect conditions, this was a design error. Add rebar corrosion, which is likely under the hot wet roof, possible damage by the installation and testing of the epoxy bolts, and possible live load overload from roof materials or removed debris stockpiles, and it is highly possible that this cantilever slab failed first. The impact of falling concrete is the weight times the fall distance/deceleration distance. If the height is 120 feet = 1440 inches and the deceleration is 2", a 50 lbs piece of concrete imparts 50lbs x 720 = 36,000 lbs. 500 lbs = 360,000 lbs. Negating wind friction, for a 120' fall, the debris would be traveling 60 mph at impact.

If they are declaring it is a recovery rather than rescue (which is what they really are saying, without saying), then they can pull the rescuers out, cordon off the area (just like it is now) and that building can sit there for MONTHS while a proper investigation takes place, with no real danger.

As for the surrounding condos, they should be evacuated, too, until we find out what went wrong. So no need to worry about danger there, either.

The real danger is they are afraid of what they'll find, I believe...

I'd rather see the NIST engineers get up there and say that THEY approve of the demolition. NOT Dade county and even Florida politicians.

BlakeStr - how do we know there was a crane loading the roof? It isn’t present in the early pictures post-collapse.

Also - if the cantilever collapsed and most of it landed on the 12th floor roof - that’s a drop of 10 feet or so. How likely would the building initially survive that?

Quote (Roga50)

As for the surrounding condos, they should be evacuated, too, until we find out what went wrong. So no need to worry about danger there, either.

Since you live in Florida I'm sure you'd be more than willing to pay the taxes to pay for the residence of all the other condominium complexes to stay in 1st class hotels for another year or 2 while the investigation is completed!

The next of kin and the health department would want those bodies removed before decomposition. Properly imploding the still standing building will preserve the collapse site vs if the building is left to stand it is like;y to collapse onto the existing debris. The two engineers brought in, Musser Rutledge and KCE may already know the details and sequence of the collapse as they are privy to information that is not shared with the public.

Quote (BlakeStr)

the slab is only 6" thick and the reinf only #4@13" oc. Using structure dead loads plus 10 psf for roofing material and 30 psf for live load, the factored moment is 4.08 k-ft/ft and the factored capacity is only 3.99 k-ft, so assuming perfect conditions, this was a design error. Add rebar corrosion, which is likely under the hot wet roof, possible damage by the installation and testing of the epoxy bolts, and possible live load overload from roof materials or removed debris stockpiles, and it is highly possible that this cantilever slab failed first.

Minor clarification of the drawings might be needed, the steel was called out as #4@13. But the notes state that bars shown on the framing plan are top bars, in addition, unless noted otherwise. The top steel, which would be more pertinent to the bending moment for the cantilever was typically much higher is shown on the penthouse framing plan. The bars called out are top bars and would be in addition to the #4@13 call out. I think the steel for the cantilever is much a decent amount higher than #4@13

JS5180, I read on this thread page 1 I believe, that a crane had been on site the day before the collapse. The question raised in that post was where had the crane sat? I apologize if in error, but based on the fall protection plan drawings, it looks like the roof is mostly encircled with cantilever slabs. Some of these slabs have balconies below, but the balconies are not continuous.

Ricky - what about the PH roof?

A poster on Reddit has correct my account of the 11th floor occupants. They were in 1106. Which puts even more wall between them and the pool slab.

Quote:

Since you live in Florida I'm sure you'd be more than willing to pay the taxes to pay for the residence of all the other condominium complexes to stay in 1st class hotels for another year or 2 while the investigation is completed!

1st class hotels? Lol. They are housing the evacuees at the county fairgrounds... Probably in a tent city (not sure on the tent city, though, but I don't believe there are buildings at the fairgrounds).

BlakeStr that would be a pretty big crane to reach over the cantilever sections, since surely they wouldn’t park it on the slab in front of x10/x11 (the only place without a cantilever).

I’m not disputing it - just trying to figure out where it would have been, and whether it’s still there. The roof does not appear to have any wheeled carts, so it’s a really interesting question - how the hell did everything get up there and to different spots?

The notes posted by Warrenslo say 8" slab floors and roof, but the parapet detail shows a 6" slab. This may be why Morabito said to verify the slab thickness. Note 6 says for reinf at cantilever #4@13". If this was additional it should say additional.

Quote (Roga50)

Quote:
Since you live in Florida I'm sure you'd be more than willing to pay the taxes to pay for the residence of all the other condominium complexes to stay in 1st class hotels for another year or 2 while the investigation is completed!

1st class hotels? Lol. They are housing the evacuees at the county fairgrounds... Probably in a tent city (not sure on the tent city, though, but I don't believe there are buildings at the fairgrounds).

That's one thing for a temporary relocation of the residence of the building that collapsed however it certainly something that would not be acceptable for residents of other buildings if you start effectuating all of them. I'm sure he wouldn't move from me million-dollar condominium to a tent because the government told you to.

Note number 3 says reinf shown is top bar.

This article says a crane was at the building. https://www.usatoday.com/in-depth/graphics/2021/06...

The posted plan explained to be top bars shows #4 cantilever bars and based on the quantities shown they appear to be about a 13" spacing.

Quote (warrenslo)

P16 is on top of a column. P15 and P17 are between columns. See the column anchor on the left side of the penthouse (that anchor also could have been the failure point.)

Correction, P15 & P17 are also shown on top of columns, typically these are installed between columns, so this is odd.

You appear to be correct. I misinterpreted the dashed line calling out "EXISTING WALL BELOW" as the support line for the cantilever. Not sure why the parapet section shows a bearing wall as the support if there is no wall. Also, the section calls out 5'-6" cantilever, which doesn't seem to match the 7'-0" cantilever shown in the penthouse plan.

As a side note, the anchorage of the parapet wall is very weak IMO. (4) #5 dowels (hooked? no hooks?) going into a 6" slab at tie columns spaced @ 20'-0". That's very little anchorage for a roof parapet in a hurricane region.

Could the round object in the ramp video be a jet fan for ventilation?

Quote:

I'm sure he wouldn't move from me million-dollar condominium to a tent because the government told you to.

People in million dollar condos down here have other alternatives that won't affect their bottom line at all.

Around here, a million dollars buys you a closet with a solar panel on top--livin' the good life!


spsalso

Can anyone identify:

1. The cardboard box in this picture, ending in “ECK”
2. The blue wrap
3. The approximately 4” layer of material above the slab at the far right of this picture?

(Credit Miami Herald)

These all appear to be on the roof, just outside the penthouse corridor.

Quote (Js5180)

Can anyone identify:

1. The cardboard box in this picture, ending in “ECK”
2. The blue wrap
3. The approximately 4” layer of material above the slab at the far right of this picture?

1) Looks like the Greenheck logo. Probably the box for an exhaust fan. From the photo below, the exhaust fans looks relatively shiny/new.
2) Possibly wrap from the factory for the exhaust fans.

Wow. I am impressed. That answers the question.

Quote (DroppedBits)

What you also see in this picture is the roof anchors were not needed - they can access the building from the ground level with a cherry picker.

We need to reevaluate requiring them on older structures that may not be able to withstand the installation or testing requirements. This is a sort of grey area where OSHA requires the anchors and the building code generally doesn't really provide any guidance.

Quote (Js5180)

Also - if the cantilever collapsed and most of it landed on the 12th floor roof - that’s a drop of 10 feet or so. How likely would the building initially survive that?

Above the bedrooms of x11 only the 12th floor and penthouse had cantilevers, the remaining was the two strips of bedroom windows below. If the cantilever broke off it would have fallen into the pool deck where the column was damaged. In the surveillance footage this area seems to already be missing. I'd imagine there is more to the video they haven't shared yet unless the video was on a motion sensor and triggered when the main collapse started.

Quote (BlakeStr)

This building was 40 years old which is 14,600 days, but this collapse happened the day after a crane was loading roofing materials on the roof and the day after fall protection anchors were installed. The parapet detail Warrenslo posted has a 5'-6" cantilever, but when analyzed the moment hinge point should be center of support which is about 5'-10". The slab is only 6" thick and the reinf only #4@13" oc. Using structure dead loads plus 10 psf for roofing material and 30 psf for live load, the factored moment is 4.08 k-ft/ft and the factored capacity is only 3.99 k-ft, so assuming perfect conditions, this was a design error. Add rebar corrosion, which is likely under the hot wet roof, possible damage by the installation and testing of the epoxy bolts, and possible live load overload from roof materials or removed debris stockpiles, and it is highly possible that this cantilever slab failed first. The impact of falling concrete is the weight times the fall distance/deceleration distance. If the height is 120 feet = 1440 inches and the deceleration is 2", a 50 lbs piece of concrete imparts 50lbs x 720 = 36,000 lbs. 500 lbs = 360,000 lbs. Negating wind friction, for a 120' fall, the debris would be traveling 60 mph at impact.

Could the pool slab handle this impact?

Saw this article early this morning:
Link

Quote ((article quote))

Allyn Kilsheimer, who was hired by the city to examine the incident, confirmed to The New York Times that there are signs less steel reinforcement was used during construction than called for in the original 1979 design to connect concrete slabs below a parking deck to the building's vertical columns.

FWIW, here's a picture of one of the post anchors snipped from https://www.miamiherald.com/latest-news/jdzgc4/pic... in post in first part by bradw1128 (Civil/Environmental)24 Jun 21 20:46


In this video of early rescue you can hear what sounds like a car alarm. https://www.miamiherald.com/news/local/community/m... It's surprising you don't hear more, but how long the security alarm sounds varies between models.

Quote (StrucDesignPE (Structural))

Quote ((article quote))
Allyn Kilsheimer, who was hired by the city to examine the incident, confirmed to The New York Times that there are signs less steel reinforcement was used during construction than called for in the original 1979 design to connect concrete slabs below a parking deck to the building's vertical columns.

Those deficiencies were noticed early in the first part.

Not sure is this item has already been posted or not, but if it has, sorry for the redundant post:

Surfside Condo Wreckage Hints at First Signs of Possible Construction Flaw

https://www.msn.com/en-us/news/us/surfside-condo-w...

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

Yep, I should have looked more carefully

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

The slab steel does look light but it's hard to say definitively.

Is the implication that there aren't enough bars left going through the column? Bottom steel is missing? Something else?

Even if the slab steel is light, I still struggle with why the failure occurred now and not in the first 40 years.

Let’s assume that the surveillance camera was motion triggered. It’s a professional camera mounted on a pole just east of the 8701 building.

In my experience, motion triggers are software based - if enough of the pixels change, it’s triggered. However, the point of the motion trigger is to reduce the amount of unnecessary storage, and the camera is always powered on. There is a look-back period built in, usually 30 seconds or so. The recording system saves the video from 30 seconds before the event.

So even if the surveillance camera was motion triggered, it should most likely still have video for some interval prior to the motion.

Quote (799931)

Even if the slab steel is light, I still struggle with why the failure occurred now and not in the first 40 years.

It could be a latent defect that forms one of the holes in the Swiss cheese. For example, just a hypothetical for discussion, weak connections on a few columns, combined with stress and vibration from the adjacent construction at 87 Park, combined with someone reversing a 14,000 lb F-350 truck up to the planters to unload construction equipment, combined with cumulative structural damage. I invented the heavy pickup truck, just as a straw to break the camel's back.

Search and rescue suspended pending demolition. Also, a cat has supposedly been spotted on one of the lower balconies. They're setting a trap to try to catch it.

Quite frankly, if my dogs were trapped in there, one way or another I'm getting into that building to bring them out.

Officials pause operations at Surfside collapse site to focus on demolition ahead of Tropical Storm Elsa

Quote (799931 (Structural)4 Jul 21 14:39 The slab steel does look light but it's hard to say definitively.)

The reinforcement, I believe they were referring to was the fact that the top bars at each column was to have 25% of the bars going through the column so we should have seen at least 4-5 top bars hanging off to columns not 2-3. (Out each of the 4 sides) This of course could be because some were sheared off or some bars were placed just at the edge of the column and stayed in the slab below. Depending on the specification Tolerances this may or may not have been an acceptable construction practices…

Quote (DroppedBits (Electrical))

Quite frankly, if my dogs were trapped in there, one way or another I'm getting into that building to bring them out.

I understand how attached people get to their pets. Last Sunday evening I rescued a neighbor's cat from forty feet up in a pine tree. It was my first animal rescue climb, but I've made over two hundred climbs over seventy feet in the past two years as a recreational climber.

https://res.cloudinary.com/engineering-com/image/upload/v1625415155/tips/ColumnAnchor_yvltfa.pdf

Here is a theory based upon diagonal concrete tear in Stair Wall. A column anchor was to be mounted on column at what appears to be beginning of tear in stair wall. What if they were testing that anchor to 5000 lbs proof load and damaged wall in process but it did not fall till later?

https://res.cloudinary.com/engineering-com/image/upload/v1625415341/tips/Roof_Column_Anchors_40-year-re-certification_xwlgva.pdf

https://res.cloudinary.com/engineering-com/image/upload/v1625415375/tips/Sheet_3_of_1979-plans_fivplb.pdf

Cantilever roof only extends in the area below this anchor for Penthouse and Floor 12, and a large chunk of stair wall would seem to be enough to drop both those cantilevers and perhaps explain the lady seeing the patio deck collapsed from the lobby, but being able to escape her room. Then maybe step 2 was the 14000 F350 Dually Truck backing into garage column?

Just curious, are there any of the Structurals here think they could of safely shored the remaining portion of the building instead of the expedited demolition? I realize it would be costly but it might save them from losing evidence and buy rescuers some time to get pets out.

That would have been my approach, but not on site... also it helps with destroying any evidence. This is likely less costly, also... all in the Florida governments best interests. I'm surprised the other government agencies haven't stepped forward.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Sure looks like a square or rectangular plate pull out at being of wall diagonal tear.

What was the original pool deck designed for? Its a slab with sand and then pavers over it. Was the pool ever rehabbed and built up where they added this layer of sand?

Quote (Thermopile)

F350 Dually Truck backing into garage column?

This theory takes a lot of speculation because there is no evidence that any vehicle was moving in the garage at the time of the collapse.

The F350 Dually comment is based on other comments concerning the tik tok video of garage ramp before collapse. Even without that part 2 of theory, part 1 may have been enough to be the straw on the camel's back for a poor maintained structure with lots of water under that roof area that was being replaced.

Coupled with the water damage to the main column line that others have mentioned at building wall and planter areas

Quote (Jstructsteel)

Was the pool ever rehabbed and built up where they added this layer of sand?

I posted a pic of a rehab circa early 2013 upthread.

If an F350 Dualie was involved, it would be in the Tik Tok video - stuck in the outer garage opening because it wouldn’t fit in a garage with 6’5” clearance. Nor would it make any of the turns.

I’m thinking the round object is a ventilation fan, which the plans show as being in that general area.

I am not wanting to further expand the F350 Dual Axle Tik Tok, but a 1994 Ford F350 2 wheel drive has an overall height from Ford of 6 feet and 2 inches, which is less than 6'5" Entrance height limit.

You ventilation fan being the round object is very plausible

FWIW
The company hired to take down the damaged Surfside building is known for the Seattle Kingdome implosion.
(please complain to me if this is behind a firewall. Thanks)

SF Charlie
Eng-Tips.com Forum Policies

Quote (Js5180 (Computer)4 Jul 21 18:19)

I’m thinking the round object is a ventilation fan

Good sleuthing, I was wondering was a washing machine could be doing there, but your fan, as pictured, is much more plausible.

SF Charlie
Eng-Tips.com Forum Policies

For anyone not familiar with them, the Loizeaux family / CDI are pretty much the best in the business at precise demolition with explosives. If anyone can drop it neatly into its own footprint and the available western plaza deck, it's them. Loads of their past projects here:

https://youtube.com/user/TheLoizeauxGroupLLC

The heavy F-350 thing was just my invented unusual hole as part of a hypothetical example of how the Swiss cheese model can make a 40 year old latent defect suddenly be significant in a failure. In my example, it was a way of quietly doing damage to the surface parking area, that reduced the remaining structural margin and explained the failure over there. I have no evidence to say something like that happened, but the ongoing construction work makes the scenario of a heavy vehicle up there a possibility.

I don't think the officials will give much info on when the demolition is going to take place. They don't want a crowd, and it's certainly not appropriate to make an event out of it. When they're ready, the police will block the streets, make sure the area is clear, and it'll all be over in an hour or less.

Hi, be gentle with me - first posting !

I've been reading postings on the forum for a while - found this on You Tube ...

https://www.youtube.com/watch?v=hynHiWE818c

Apologies if this has been posted before ...

"If you want to go get your pet, read and sign this release form. The two people next to you will also sign it, affirming you read it. Don't dawdle, as there's others waiting to go up. And don't slam any doors. Good luck."


spsalso

Lukeuk99,

I was new a few days ago, and the folks here are pretty nice, though if you're wrong, they're likely to tell you so.

A thing that I saw in that video was concerning to me. It has the patio slab tied mid-height to the columns under the building. Why'n holy hell did they not just put up another adjacent post? Then when the slab fell, it wouldn't have pulled the building column down. One reason is that they didn't think of it. I didn't until I saw the video.


spsalso

Welcome both of you and any other new guys... we'll generally correct you in a friendly fashion...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Lukeuk99,
Welcome to the site. That video illustrates very well one of the main theories as to how the collapse occurred, discussed here but not with graphics like that. And spasalso's idea of a joint between the pool deck and the building proper has also been discussed here and supported. That gets into the area of concept design, in which the structural, architectural, and financial considerations often clash.

Dropping currently scheduled At 7 PM tonight.

Official: Drilling done, demolition of collapsed condo set

Quote (AP)

the remaining structure was scheduled to come down between 10 p.m. Sunday and 3 a.m. Monday, barring any last-minute glitch such as someone entering the restricted zone around the building

SF Charlie
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Quote (MOJOJOHN (Structural)4 Jul 21 22:14)

Dropping currently scheduled At 7 PM tonight.

Timezone? Source?

SF Charlie
Eng-Tips.com Forum Policies

I'm sure that will be local time, GMT-4.00

Demolition live stream. Is live now 7pm EST

https://youtu.be/epNqN8kSmqU

First off, this demolition is extraordinary on so many levels, but Kilsheimer's analysis is equally as dire in that the structure only has a windloaded capacity of 45mph sustained, 60 mph gust @ a safety factor of 1.

It appears that this is not going to be an implosion where the structure drops or "pancakes" in place, but is designed for lack of a better word "hinged" to fall (slide) forward (To the west on top of Collins St) basically intact

From an structural standpoint, it will be interesting to see how the sheer walls that constitute the cores(stairwells, elevator shafts) fall, or don't fall.

Press briefing just now from the mayor confirms 10pm-3am ET window for demolition.

Quote (Keith_1)

it will be interesting to see how the sheer walls that constitute the cores(stairwells, elevator shafts) fall, or don't fall.

With such little shear walls in the E-W direction:

Just in: plans for the controlled demo of the remaining portion of the #Surfside condo

SF Charlie
Eng-Tips.com Forum Policies

Shoring the building is not an option. No HUSAR team would risk lives to shore an empty building for the sake of evidence of unknown value. And who would survey the building and what engineer would approve the plan when no-one is sure yet what the cause of collapse was? And what engineer would allow crews to work in a building that has been declared unsafe? It would be weeks and dollars and risk of more lives lost.

Apparently as of May 26, 2021, there was a crane on 88th (north side of building) with outriggers sitting on the garage structure carrying roofing supplies and "tar" to the roof. Maria Notkin of Apt. 302 made the initial complaint - she appears to be the same unit who called their relatives from their landline multiple times after collapse. They were asking for the crane to be moved from 88th to Collins, the association said they needed the crane on 88th to reach the entire roof. See page 40 of email communication documents uploaded by the city. Link

Also, the way the parapet ripped away from the remaining shear wall over the x10 units is intriguing - while most of the building ripped from the shear wall cleanly due to high force, the roof parapet did not. There was a column roof anchor into this wall. If the parapet and balcony fell onto the pool deck it would have fallen into the column that was damaged per the ENR article at about 60 mph per another post above. Per an on-site engineer, again in the ENR article, the backside of this column had impact damage clearly not from a vehicle, the transfer beam also had damage. This column damage appears to have been what caused the pool deck to collapse due to the damage pattern.

A roof anchor location hypothetically causing the roof and 12th-floor balcony to collapse is in red below. The damaged column causing pool deck collapse (per ENR report) is in blue below.

Quote (Ingenuity)

With such little shear walls in the E-W direction:

Hopefully, they are able to collapse it all the way due to the transfer beams.
The same company made this mistake in 1996 due to a similar transfer beam issue.

Ingenuity,

S5-14 Elevators and Stairwells.

https://www.townofsurfsidefl.gov/docs/default-source/default-document-library/town-clerk-documents/champlain-towers-south-public-records/8777-collins-ave---structural-pages.pdf?sfvrsn=18191194_3

interesting collection of picture, not implying agreement with conclusion https://www.youtube.com/watch?v=PEPyE2h6P4k

Quote (Sym P. le )

In the photos you posted of the entrance to the garage what is the square object to the upper right? A beam?? It's a sign.

Quote (b)

oo1]interesting collection of picture, not implying agreement with conclusion https://www.youtube.com/watch?v=PEPyE2h6P4k

I found that thread previously but I'm really not sure how knowledgeable the creator of it is. He obviously has not been on the site and by walking the video it looks like he's just trying to connect himself with name people such as CNN commentators etc. I'm not sure any of the information in that video is usable to draw conclusions from.

Alright, which one of you guys did it: source
"Crestview Towers’ condominium association in North Miami Beach has a report from an engineer saying the building is safe for occupancy and it will be submitted to North Miami Beach officials by Noon on Tuesday according to Mariel Tollinchi, the association’s attorney. A Jan. 11 “unsafe” warning to the board from an engineer prompted the North Miami Beach building and zoning department officials to condemn the Crestview Towers Condominium Friday afternoon. Tollinchi said the report was very vague.
“A subsequent inspection was had of the building recently and an unofficial report was released by that engineer saying that the building is actually safe for occupancy and that the repairs on the structure and electrical can be done with the residents there,” Tollinchi said."


MOJOJOHN mentioned 40 year certifications must be done by those licensed as Special Inspectors (S.I.) and I don't see that on the Jan. 11 B&A Inspection Report.
What a massive turd, Miami can't even figure out who has authority and who is qualified etc. meanwhile people are getting booted out/in their apartments.
Mayor, City Manager, Building Department, Inspector, Condo Association, Lawyers, Unsafe Structures, engineer's flip flopping. Unbelievable.

Quote (ChiefInspectorJ)

https://www.youtube.com/watch?v=PEPyE2h6P4k Speculates that the image is the end of a broken beam.

Who is going to break it to him that what he describes as a broken beam in the tiktok video is just a TOW AWAY SIGN?

You can see the sign in the google street view.

Link

Quote (ChiefInspectorJ (Specifier/Regulator) 5 Jul 21 00:44)

In the photos you posted of the entrance to the garage what is the square object to the upper right? A beam??

Tow away zone sign.

Does this appear to be a detached balcony railing?

What drives me absolutely crazy is that a building actually got to the point, where (1) the structural issues that could have been easily repaired 15 years ago, got so bad to lead us to this point (2) that the switchgear was not properly maintained and needed to be replaced (3) the domestic pump and double detector were not maintained and needed replacement (4) the fire pump was not maintained needed to be replaced (5) The generator was not maintained and needed to be replaced, and (6) every other system basically needed major repairs, or replacement.

Finite analysis or any math in the world in regards to a moment, seismic activity, or am eccentric point load is simply not appropriate, when every other system has failed.

I will say once again that some failures such as the FIU or Hardrock are entirely appropriate to subject to finite or discreet analyses, but in both instances, the point of analysis started during construction and not 40 years after. In both case of the FIU and the Hardrock failures there was a structural failure that can be learned from; However I simply don't see want can be learned from the failure of a 40 year old structure that has been highly loaded on multiple occasions, yet collapsed under it's own weight.


Like I have said we are a self-regulating industry, we write the codes, I think there is a need for us to do so.

As long as you have condominium ownership and management structures the way they are currently set up across North America (Florida is hardly alone in having this problem), you are going to get people that don't have the necessary qualifications making the decisions to not spend the money that needs to be spent.

The rest of the building is down...

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

Quote (Alright, which one of you guys did it: source)

Sure glad it wasn't me... that they would get a report stipulating that is also a concern. As we used to say when things didn't make any sense... "No dots on dice".

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

I just want to comment regarding inspections. The only way to attempt to avoid massive corruption is to have the insurance companies do the inspections since they have the liability.They also will be free of local politics.
I can't tell you the hundreds of times I had been overruled on crucial inspection decisions by my Building Official bosses. They were controlled by the boss hogs of the town/County and by the contractors.
Now here in Florida private inspectors are paid guns for the contractors that hired them. So you have a massive problem.

Quote (The rest of the building is down...)

by itself? or did it need help?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Warrenslo,

What is the ENR report? Can you (re)post a link please?

Also, isn’t that triangular hole in a CMU wall? It looks to me like the slab along that whole area has been pulled out, leaving a horizontal hole and taking a chunk of CMU wall with it over the staircase. Or is that your point? The slab was pulled out, rather than snapped like the rest of them?

Zebraso - I think that’s a staircase, from the east stair tower. Here’s a different angle, showing a prefab steel staircase nearby, and there’s a few of these scattered around in various pics but all in that general area:



The other possibility may be the fence between the upper garage and the pool deck. The black object directly behind the car’s driver side appears to be a window frame.

Quote (dik)

by itself? or did it need help?

It was taken down with explosive charges by CDI.

I was watching the live feed link posted by nononononono at 23:04.

I read that the demolition wasn't going to happen until after 10:00pm EDT, so that when I started to watch. Several times you could see what looked like drones in the air, apparently waiting for the moment that they set off the charges, which was about 10:31pm EDT. About five minutes before that occurred, you could hear sirens going off, which I assumed was the final on-site warning. There appears to have been some fire based on the appearance of a bright yellow glow for the first couple of minutes after the building came down.


John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

The Triangular shear wall missing from the stair tower adjacent to elevator shaft appears to have been damaged at upper right corner as the beginning of the tear that ran diagonal down. The lower part of triangle looks like it peeled away as it fell. My theory is that the roof column anchor that was designed to go at the top edge of that diagonal tear was load tested that day and weakened the stair sheer wall, which fell later than night/early morning. Thus this might be the trigger that started it all. The stairs in the picture just posted is of the North stairs.

WOW, to do that in 24hrs, without any prep, I'am simply speechless. I didn't think that they were only doing were doing any placement of charges above the 1st elevated floor, but I was clearly wrong. I have no Idea how this was mobilized, or performed in such a quick manner, but WOW.

but the marble in the entrance was very pretty....

Quote (dik (Structural)5 Jul 21 02:35)

by itself? or did it need help?

It got excellent help.
WATCH LIVE: Surfside tower demolition

SF Charlie
Eng-Tips.com Forum Policies

Notice in the demolition video, looking south - the parapet over the x04 living room came free completely and yet remained intact. As if it wasn’t attached at all.

Reviewed a little history of the use of modern admixtures in concrete to reduce its permeability to chloride ions, and it seems that the modern use of super plasticizer was not common in the USA circa 1980 when this condo was built. Reducing the water/cement ratio to below 0.4 and adding fine pozzalans is used today to reduce the diffusion rate of chloride ions to the rebar, and the plasticizer aids in reducing the water to cement ratio. If the workability was not enhanced by using plasticizer, is it possible they added calcium chloride to improve workability but compromised rebar life?

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick

I figured the w/c would be between 0.4 and 0.45. With RJC and the parking garage experience they had, we were typically using 4.5 to 5.0 ksi stuff back then for parkade slabs and 1-1/2" min cover for slabs and 2-1/2" for columns as well as 4" slump was common... substantially higher than most consultants at the time. This was not for a marine salt environment... put typical de-icer salts.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

More news... looks like the condminium corp was more interested in putting 'lipstick of the pig' than fixing real problems...

"Following a Miami Herald report that it took more than a month for the town to respond to plans submitted by the building's board in May, town manager Andrew Hyatt released a statement saying the issues under discussion were preliminary plans unrelated to structural work and not permits to begin repairs the building needed to pass a 40-year recertification.

“It would appear that the Champlain Towers South Condominium Association sought to address a number of issues outside the scope of any proposed 40-year re-certification work,” such as new natural gas lines and added parking, Hyatt's statement said. “There was no indication during any communications between the Town and the association by telephone or electronic mail that this submission required emergency action by the Town of Surfside.”

Emails first obtained by the Herald show the condo building manager growing impatient at the lack of response from the town to plans for a temporary parking plan needed to move forward on repair of a concrete slab under building's pool and on damaged columns in its garage."

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Just some Links showing the remaining structure coming down ... differing angles.

https://www.nbcmiami.com/news/local/demolition-tea...

https://wsvn.com

https://www.local10.com/news/local/2021/07/04/watc...

The initial collapse was far more elegant...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Quote (dik)

"Following a Miami Herald report that it took more than a month for the town to respond to plans submitted by the building's board in May, town manager Andrew Hyatt released a statement saying the issues under discussion were preliminary plans unrelated to structural work and not permits to begin repairs the building needed to pass a 40-year recertification.

This is not true, based on the emails, 87 Park (to the south) removed 22 on-street parking spaces, the building wanted to add temporary parking spaces along 88th and additional spaces on the oceanside to allow for structural work in the garage. The emails about this are in the link sent earlier today, and discussions were ongoing up to days of the collapse. The town is seriously trying to cover this up.

Quote (Js5180)

Notice in the demolition video, looking south - the parapet over the x04 living room came free completely and yet remained intact. As if it wasn’t attached at all.

Definitely an interesting development...

Quote (Keith_1)

WOW, to do that in 24hrs, without any prep, I'am simply speechless. I didn't think that they were only doing were doing any placement of charges above the 1st elevated floor, but I was clearly wrong. I have no Idea how this was mobilized, or performed in such a quick manner, but WOW.

That's the Loizeaux family for you. From what I read, it was basically small sequenced charges in the columns at basement and ground level, nothing in the tower. Gravity and relatively weak slab-column connections did the rest.

Quote (Js5180)

Warrenslo,

What is the ENR report? Can you (re)post a link please?

Also, isn’t that triangular hole in a CMU wall? It looks to me like the slab along that whole area has been pulled out, leaving a horizontal hole and taking a chunk of CMU wall with it over the staircase. Or is that your point? The slab was pulled out, rather than snapped like the rest of them?

ENR article (paywall but there's a few free articles prior to required payment):

Surface Parking Zone of Interest
An area of interest is the surface parking zone near the lobby entry drive that goes partly under the remaining wing. That slab for the parking, which is next to the grade-level pool deck, is the roof of a one-level basement garage that fills the site's entire footprint.

According to Kilsheimer, it appears, from the position of the cars that dropped a level—one car’s nose ended up pointing to the pool area—that the lobby slab columns moved sideways toward the pool deck, causing the pool deck to drop, which then pulled on the tower columns, causing them to fail. “This will not prove where it started,” he says. "That is not something we can determine in a hurry."

However, Kilsheimer has all but ruled out an overload from the parked cars as the trigger. “It could be that a drunk driver hit a column,” he says. “We don’t know yet.”

KCE and Mueser Rutledge will soon be joined at the site by another investigating team. Also at the press conference, the National Institute of Standards and Technology of the U.S. Dept. of Commerce announced it will soon be launching a technical investigation into the causes of the failure under the authority it was given by the 2002 National Construction Safety Team Act.

Yes, that is my point, the upper parapet over x10 seems to have fallen in a different direction and more slowly than the rest of the building.

Quote (ChiefInspectorJ)

I just want to comment regarding inspections. The only way to attempt to avoid massive corruption is to have the insurance companies do the inspections since they have the liability.

Agreed, there are many development companies, including my own, who partner with insurance companies who require third-party review. With that said the Harmon Hotel in Las Vegas' third party inspector missed the shear wall error requiring the building's demo.

Quote (dik (Structural)5 Jul 21 05:34
More news... looks like the condminium corp was more interested in putting 'lipstick of the pig' than fixing real problems...
Emails first obtained by the Herald show the condo building manager growing impatient at the lack of response from the town to plans for a temporary parking plan needed to move forward on repair of a concrete slab under building's pool and on damaged columns in its garage.")

The part about repairs to slabs and columns in the pool area sounds quite important to me, particularly when viewed from the events of the last 10 days or so, and should have deserved serious attention by the "town" in my opinion.
As stated, it appears the focus was on temporary parking when it should have been on structural repairs.
Even that may have been only "lipstick" for the pig.
I imagine next time the manager will not wait for approvals.

Quote (Keith_1)

Like I have said we are a self-regulating industry, we write the codes, I think there is a need for us to do so.

Annual or bi-annual Type A inspection (fire, electrical, easy to spot things) and 10-year Type B inspection (structural, more detailed etc.) I think is the solution. With that said, if OSHA roof anchor testing caused this, then that needs to be addressed - now. If these old buildings weren't designed for anchors, and they clearly could be accessed from a cherry picker, why are they being pushed by a structural engineer before structurally repairing/shoring up the building?

The roof anchors are a grey area as the IBC doesn't address them and the roof anchor contractors are my second least trusted sub after the window guy (why can't they ever get the right window in the right spot.)

Quote (dik (Structural)5 Jul 21 04:56
I figured the w/c would be between 0.4 and 0.45. With RJC and the parking garage experience they had, we were typically using 4.5 to 5.0 ksi stuff back then for parkade slabs and 1-1/2" min cover for slabs and 2-1/2" for columns as well as 4" slump was common... substantially higher than most consultants at the time. This was not for a marine salt environment... put typical de-icer salts.)

VERY good points - more attention to protecting the reinforcing. I was thinking about the difference in bridges and overpasses in the Miami environment - more concrete cover, more dense concrete - and much longer life expectancy. The Construction details of this building appear to be those of a building with complete protection from the environment.
I am curious - how far from the coastline do the salt conditions extend? At what point can they be dismissed? The slab over the parking near the pool certainly looks like a concern in this regard.

https://res.cloudinary.com/engineering-com/image/upload/v1625470464/tips/penthouse_24_ROOF_ppcrfe.pdf

I have circled what appears to be roof anchors that may have been the initiating "boom" that caused the sequence of events.

The picture was taken from a prior thread focusing on the pool deck but looking at it now seems to give more details.

I'm behind the conversation by a few days, but when discussing the role of 'state wide agencies' in mandating building safety, there are some parallels with the Grenfell tower fire disaster in the UK.

Although the inquiry is still ongoing, a few years after a renovation (including external insulation/cladding) a huge fire engulfed the building due to inappropriate cladding systems being used, killing 72 people.

The long term solution to prevent this from happening is to introduce the 'Building Safety Regulator' who will specifically be responsible for the safety of construction of high rise (18m+) buildings.

The legislation has just been presented to Parliament so a lot of details are yet to be determined, but it will be interesting to see whether they begin a routine inspection of existing building, as has been suggested earlier in these thread(s) (many other tall buildings have found inadequate fire protection measures, fire doors + fire stops etc in the post-Grenfell inspections).

GeorgeTheCivilEngineer - "there are some parallels with the Grenfell tower fire disaster in the UK"

Sadly the loss of life at both Grenfell Tower in the UK, and at Champlain Towers is similar / has parallels - the (apparent causes) differ.

At Grenfell, the cause was flammable cladding, that was ironically approved by UK building regulations for use. It turns out it's the regulation related to it's method of install was at fault at Grenfell, but it was legally installed and a permitted method of installation at the time. The foam/polyurethane sandwiched in foil panels, and used for insulation, were installed with no protection of the edges, up the side of the building, on a metal framework, so hence when the fire heated up the first panels on the 4th floor, it melted/set fire to the first, the fire just continued, jumping from panel to panel, with the metal frame creating an unfortunate breathing gap for the fire, with no barrier or protection to stop it moving to the next !

In the UK, the Grenfell structure remains standing in West London (I get to drive past it occasionally), it's shrouded in scaffolding and plastic sheeting. I'm not sure what the longer term plans are !

The common issues from both Grenfell and Champlain that need to be addressed are numerous eg. "better/stronger regulation regarding checks and ensuring current/known building issues are either adhered to, or corrected (where possible)". Also both buildings appear to have had problems with their respective management/resident companies, who either had a lax approach to building issues, or just delayed/bickered/ignored - causing delay and on occasion compounding issues.

Quote (Lukeuk99)

In the UK, the Grenfell structure remains standing in West London (I get to drive past it occasionally), it's shrouded in scaffolding and plastic sheeting. I'm not sure what the longer term plans are !

It has been propped up but will have to be demolished soon.
"Engineers are warning that the Grenfell Tower must be carefully dismantled before May 2022 because of continued deterioration of exposed concrete structures."
There are some locals and survivors who wan the structure restored and planted as a vertical garden memorial.

Quote (alr1970)

It has been propped up but will have to be demolished soon.
"Engineers are warning that the Grenfell Tower must be carefully dismantled before May 2022 because of continued deterioration of exposed concrete structures."
There are some locals and survivors who wan the structure restored and planted as a vertical garden memorial.[\quote]

Good to know something is being done. The heat alone from the fire - must have seriously degraded the structure (as suggested in the articles). It stood for months like a huge black burnt-out tomb stone to those who lost their lives - before the plastic sheeting went up.

Quote (Thermopile (Aerospace))

My theory is that the roof column anchor that was designed to go at the top edge of that diagonal tear was load tested that day and weakened the stair sheer wall, which fell later than night/early morning. Thus this might be the trigger that started it all.

I think the bolts that hold the anchor are tested with a device that applies the load to a very small area before the anchor itself is installed. See this post above: Ingenuity (Structural) 2 Jul 21 19:42 It's very unlikely this sort of test could have done enough damage to result in a large section of the wall falling spontaneously hours later. The bolt itself would come out because of adhesive failure, or a small section or concrete around the bolt/epoxy would have come out, both immediately obvious and of limited consequence.

Questions:
Do we know what the anchor for that location looks like? It doesn't seem like it would be the same as the post anchors.
Why are the post anchoes so tall? If the load on the anchor is usually in the horizontal direction, the height provides more unnecessary leverage and load on the anchor bolts on the opposite side.

As a recreational climber, I'm very interested in tie-in points. I think I'd be more likely to put my rope around the base of the anchor post than use the ring.

Quote (Js5180)

Notice in the demolition video, looking south - the parapet over the x04 living room came free completely and yet remained intact. As if it wasn’t attached at all.

I believe this photo shows a parapet laying on edge on top of the cantilevered portion of the roof. The canine rescuer is standing on one of the tie columns, which provide the only attachment for the parapet. Drawings indicate the tie columns are spaced at 20 ft. It looks like the edge of the roof slab popped off when the tie columns rotated and the dowels pried out. Not implying this was a collapse instigator, just good photo evidence of that particular structural connection.

Testing of anchor bolts during assembly is a prudent measure, I always specify that with glue anchors (critical anchors get 100% pull testing, non critical anchors can get skip lot testing).

However in the case of window washing anchors, it appears that anchor bolt testing may not satisfy the OSHA testing requirements. I completely agree with the discussion above that placing a 2500 lb load between two anchor stands could create a loading condition on the roof that is outside of the loads considered for design.

OSHA Interpretation of International Window Cleaning Association/American National Standards Institute (IWCA/ANSI) I-14.1-2001 Section 8.1.3 testing requirements

This is my first post on this forum. I have lurked for years and used links to some of these discussions as talking points. Other than the conspiracy theorists that take away from discussions like this, this particular thread, all 3 of them, has been enlightening, informative and helpful. I have particular interest in this thread because I am the Building Official for a south Florida beach town with 23 high/mid-rises on the beach front, many built around the same time. There are another 20+ high/mid-rises across the street but not directly on the beach, they front the intracoastal waterway.

At any one point, we always seem to have 1-2 or more condos undergoing concrete restoration. Many times it involves mostly waterproofing and balcony work, but often it becomes more involved. One particular thing that we have noticed is that during restoration the NE corners of the buildings that are on the beach are significantly more deteriorated than other parts of the structure. We see this because often those on or near the NE corner must replace their sliders and windows that had to be removed due to the restoration. It is also not uncommon for an entire balcony to be removed and poured fresh. Wrap around balconies in the older condos end up looking like swiss cheese. See example below.

Building Official, FL & PA
The Building Code Forum

What is a "trigger" and what is the "cause" of the collapse?

I propose that they may be two different things like the straw (trigger) that broke the camel's back (broken back is the collapse.)

I also feel that it is likely that the ground floor columns were degraded due to salt water exposure when the parking garage was frequently flooded as reported by residents.

The trigger may have been the loading of the roof with material, a car hitting a column, the collapse if the pool deck patio with its own trigger and many other possible triggers.

Based on my over 50 years of high-rise design (up to 40 stories high), high-rise inspection and concrete remediation in South Florida, It is my my opinion based on review of photos, plan,
our ETABS calculations and reports, that the building would not have collapsed due to any of these triggers if the columns had been in original condition. (Yes, we did observe under design in wind and gravity loading of the original
structure. We also concluded that a failure of the remaining structure after the first collapse was not safe under 35 mph sustained winds with the accompanying higher wind gusts, based on a rough assumption of lower column conditions.)

Based on all of the above, though it now appears that the Tropical Storm will mostly miss us here, I agree with the decision to implode the building to control its direction of fall and protect the rescue teams.

Yes, evidence was likely lost due to the implosion, but life safety of rescue personnel must always take precedence over property matters.

What is the solution to minimize future failures? There are many to be considered:

1. Enforce the current requirements by the Florida Board of Professional Engineers that work on Threshold Building (See my previous post for definition)be done by qualified engineers.
The 2018 inspection of this building was done by properly licensed P.E.,S.I. engineer, but the 2021 inspection of Crestview Towers, now evacuated as not. (I look forward to seeing the report tomorrow from another engineer that says Crestview Towers is OK.)

2. Educate Building Department on who may do 40 year inspection of threshold buildings, inspection and remediation work on Threshold Buildings with serious structural damage.

3. Change the Florida Building Code to clearly define 2 above and to revise Substantial Structural Damage to include serious damage to any one or more structural members that cause a collapse if lost.

4. Shorten the inspection cycle for building exposed to seawater flooding.

5. Consider ACI and other changes that would require ground floor columns exposed to potential salt water degradation to stand up even if the 2nd floor is lost.


That's it for now, but it is not nearly enough. The world of structural engineers is going to change. It is up to all of us to participate in the discussions to make sure the changes are going in the right way.

Regards,

MojoJohn P.E., S.I. , Former Urban Search and Rescue team member.

Quote (FacEngrPE (Mechanical))

I completely agree with the discussion above that placing a 2500 lb load between two anchor stands could create a loading condition on the roof that is outside of the loads considered for design.

Thanks. If that's what was actually done, Thermopile's theory becomes much more plausible.

As far as OSHA required testing of fall protection column and roof anchors, testing the individual bolts proves the bolt and concrete hold, but only testing of the completed assembly from the fall protection eyelet proves that the whole mounted assembly meets subsystem requirements in that location. The design drawings are a mess on load testing procedures and if OSHA not specifying method of test, it is unclear how each contractor chooses to conduct the test. A stain gauge between two completely installed roof/column anchors would test 2 connections at a time and be the easiest and fastest way to proof test anchors, and should be witnessed by the city inspector, who was on site that day for this apparent reason.

Quote (MOJOJOHN)

4. Shorten the inspection cycle for building exposed to seawater flooding.

It's not just flooding. It depends on the specific beach and the way the ocean hits it, but you should look at what a strong wind and high spring tide can do on a leeward shore. About gale force 7 or higher winds are likely to carry salt spray a significant distance past the high water mark, and possibly high above the ground. I've known high spring tides and a good gale/storm to cause waves breaking against a sea wall to go clear over the roof of beach bungalows (and the wall facing the beach has a constant stream of salt water running down it). Even without waves breaking hard against the shore, gale force winds pick salt spray off the surface and carry it with them. Each beach is unique, some will be worse than others, some will need quite specific winds to really get going with spray.

I have not checked the original design drawings for steel reinforcing requirements in stair shear wall, but from pictures and way it tore diagonally, it does not appear that was not much if any steel grid in that shear wall, or rebar corner ties to connect failed panel to the perpendicular panel joint. Without steel or adequate steel grid, the potential horizontal loading of the wall anchor in a direction outside the normal load path could causes the usual tearing vector, if rebar grid is absent. Diagonal tearing does not seem likely from connector assembly test, if wall had been reinforced and tied to surrounding pours.

I would add to MOJOJOHN's list that inspection reports should be required to more fully describe failure scenarios that could occur based on the building design, and then postulate a sequence of events where the observed deficiencies eventually lead to failure.

Please let me say, my theory is based upon reading all posts in this forum for the past week, and diving into available public information. My theory is a systems theory, and requires all the great input provided in this forum by subject matter experts to piece together this theory. pieces of this theory have been touched on many different ways in this forum, and all I did was piece together the clues that seemed to align into a system theory answer. We still have no idea what was exactly going on that day on the roof, or all events leading up to this failure. But it sure seems odd that day after first load tests, you have collapse of perhaps under nourished building structure, with 40 years of neglect and cosmetic patching to hide some of the underlying damage and defects.

Quote (The part about repairs to slabs and columns in the pool area sounds quite important to me, particularly when viewed from the events of the last 10 days or so, and should have deserved serious attention by the "town" in my opinion.)

Recriminations are easy... this was brought to their attention 3 years ago.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

Quote (The roof anchors are a grey area as the IBC doesn't address them and the roof anchor contractors are my second least trusted sub after the window guy (why can't they ever get the right window in the right spot.))

A main tenet of Engineering Associations is to look after the well being of the public; we have failed, and perhaps 150 people died because of that failure.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

I have chosen to view the controlled demolition as an experiment on the structure (yes, evidence was lost).
Watch the Surfside demolition from four different angles
Surfside condo building: before, during and after the demolition
These contain some slow motion and close-up views including the columns punching through the roof.

The British Sun still has the live feed they started for the demo up on YouTube watch the rescue.
Collapsed Surfside condo to be demolished before Storm Elsa hits Florida

SF Charlie
Eng-Tips.com Forum Policies

Lukeuk99 (Computer),

Don't see parallel between UK's Glenfell Tower with Florida Champlain Condo. There heaven and earth differences.

(1) Glenfell is a public housing owned by the local government for housing the poor. Its largest 4-bed flat has under 1,000 sqft accomodation and has no resident parking facilities. Champlain condo is for the very rich as even a one-bed flat has 1,200 sqft accommodation and the minimum car park width is 10' with 113 parking spaces.

(2) Champlain Condo has collapsed structurally. Glenfell Tower is still standing and not collapsed despite suffering a huge fire that burn for 60 hours.

(3) Glenfell Tower as a public housing with no profit/commercial consideration is robust in design. It has a solid shear core with outside perimeter columns each about 42"x42" (metric size 1050mm x 1050mm). Champlain Condo is a private development. It has open shear walls and the biggest columns are 24"x24" (at the basement level). The columns in the collapsed section at the basement level are significantly smaller. It appears the section remained standing after the collapse were supported by the 34"x24" columns.

(4) Don't know the reason why Champlain Condo collapsed yet. The fire in Glenfell Tower was self-inflicted by the owner as the building was original a naked concrete structure that cannot be burnt or catch fire. The local government owner tried to beatify its appearance by approving a combustible cladding on the outside that was not made air-tight. When a fire broke out in one unit the heat cracked the window pane and the fire could migrate behind the cladding, using it as the wind tunnel like the chimney effect, to reach to other levels "externally from the ouside". When the fire got close to a corner the glass panels cracked on both legs of the corner (90 degree apart) and the fire was drawn into the flat due to pressure differences. It was quick rare to see fire could travel from the outside into the inside to spread floor by floor until the building was engulfed for 60 hours. Thus Glenfell tower is just a fire problem which is wholly within the architect department. but Champlain is likely structurally related so the structural engineer and the Condo management people may have some sleepless nights.

saikee119

Some corrections to your post ...

- Grenfell tower was actually owned/managed by a residents management company, it was NOT owned by the Council (Kensington & Chelsea Council), although they had seats on the board, they did NOT control/manage it, they just used it (when space were free in the allocated accomodation, for people in their area seeking homes). The residents company had some well documented concerns about electrical issues in the tower, and general decision making processes when it came to improvements etc (which is common to Champlain). The effective inaction by the board of the residents association/company appeared to ignore these issues. Although these electrical issues were not the cause of the building being destroyed - they blighted residents.

- The building was not for housing "the Poor" (as you suggest), it was a mixed use property, some housing association and a considerable number of privately owned and sold dwellings, some I understand sold for as much as £400,000 (at the time), because of their premium location, and views. It's worth noting in the UK many builds have to contain "mix of affordable, low rent housing", as a condition of their being granted planning permission, and to increase available housing stock.

- It's relevant to note that in Kensington and Chelsea (if you've ever visited) and most of central London, Parking spaces are like "gold dust", space is at a premium and sold separately. In many parts of London, including new premium builds very few have parking, it's something you purchase separately, if you need it. Virtually all properties in the area of Grenfell rely upon on-street parking (I know because I visit the area frequently for work), or municipal high-rise parking garages - it's just the way things work in much of London (especially West London).

Other points concerning construction / yes - agree...

I think that the result of findings will determine the inaction by the residents association at Champlain over many decades - will be marked as being a significant reason for the known decay, and the structure being compromised sadly leading to the structural failure, which we're all discussing here.

One factor that does surprise me with Champlain - is how properties were bought and sold in the buildings, without there being any (apparent) legal obligation to advise a new purchaser of a "proposed" share of building improvement cost. (it's been reported, a new owner was surprised to find out a week after owning that they were going to be asked to pay their £80,000 share of improvements, with no prior knowledge).

What were these two trunnion-like fixtures (one open, one closed) atop the columns used for?

At 1:26 in https://www.youtube.com/watch?v=ElMjRSgMsiM&t=...

I did a cursory look through the plans, but didn't see anything like that.
https://www.townofsurfsidefl.gov/docs/default-sour...

Quote (SFCharlie)

These contain some slow motion and close-up views including the columns punching through the roof.

That, and Retiredat46's close-up of those columns once again leaves me disquieted in regards to the column-deck connections in this building. And it wasn't even just the roof deck - it appears several upper floors cleaved away cleanly from an entire row of the columns during the demolition.

If the articles stating this building's deck connections were not done to spec are accurate, then the folks in the North and East towers should insist on getting some X-Rays done on a random sampling of column-deck connections to make sure they don't have the same problem - despite both buildings appearing to be in OK shape.

https://res.cloudinary.com/engineering-com/image/upload/v1625506454/tips/S14A_of_14_elevator_section_penthouse_1979-plans_offrn3.pdf

Interesting Structural Elevator Elevation Revision for Penthouse Addition. Sheet 14A of 14 Structural, buried in the out of order PDF documents released by Surfside. Shows where C8 Anchor was attached to tie beam sitting on block infill for elevator shaft extension for penthouse. Shear wall stops at original roof level deck. So diagonal tear out appears to be CMU infill wall...

https://res.cloudinary.com/engineering-com/image/upload/v1625507044/tips/S12_of_14_before_penthouse_additionstructural-pages_hbeqyv.pdf

Original Elevator Shaft before Penthouse addition

Quote (Retiredat46)

What were these two trunnion-like fixtures (one open, one closed) atop the columns used for?

I believe those are columns E2 & E4, and the western mounts for the large red HVAC support frame.

So if anchor test broke what little bond there was between concrete mid wall cap beam, then elevator vibration for the rest of the day/evening, after test could have triggered the CMU in fill wall to fall. And folks were coming and going to their condos lated at night, so elevator would have been operating.

Also what are the chances that once roof sheer wall was built they added penthouse, such that midspan elevator wall beam, spanned the whole way in one pour across the joined stair tower. A mid span lateral or diagonal pull on that beam would seem to cause deflection laterally in that beam in between block infill walls.

The black horizontal band which I originally thought was open space, is actually roof tar. The roof over the 12th floor was attached directly below it. Also visible in the picture are the broken cores of the CMU blocks in the triangular hole.

Js5180's picture also shows the broken column near tar line that anchor would have been mounted too....

Looks broken at bottom and up higher where horizontal beam would have been. You can see in the cracked stucco the lines for the elevator horizontal beam as well as the stair well horizontal beam, all connected at column anchor area

Quote (Retiredat46)

I think the bolts that hold the anchor are tested with a device that applies the load to a very small area before the anchor itself is installed. See this post above: Ingenuity (Structural) 2 Jul 21 19:42 It's very unlikely this sort of test could have done enough damage to result in a large section of the wall falling spontaneously hours later. The bolt itself would come out because of adhesive failure, or a small section or concrete around the bolt/epoxy would have come out, both immediately obvious and of limited consequence.

Each fall-protection roof anchor assembly (post, plate, anchor bolts, etc.) must be tested before initial use and annually I believe per OSHA rules (see post above.) OSHA is unclear on the exact method of testing. The ultimate load is 5,000 lbs, design load is 1,250 lbs, so the industry standard is 2,500 lbs on each axis (X, Y, Z.) I personally believe this is a flaw in the OSHA rules, how can you place an arbitrary force on an existing structure which may or may not have been designed for such loads.

This testing is in addition to any epoxy anchor bolt testing required by the structural engineer.

The plans noting 5,000 lbs. testing of the epoxy anchor bolts is concerning to me as it seems each bolt would need to carry much less force than that.

Quote (https://www.eng-tips.com/userinfo.cfm?member=jar54...)

Welcome from a fellow Inspector .Retired and tired. lets touch base.Please review some of my post.
Jeff

Another apartment complex in Florida has been ordered evacuated as a precaution after city officials became concerned over a recent report about the buildings:

North Miami Beach building deemed unsafe, evacuations ordered

A Jan. 11 report on the Crestview Towers condominium complex said it "was structurally and electrically unsafe."
Politics as usual.

https://www.eng-tips.com/userinfo.cfm?member=Roga5...
Coverup is how many of these places operate.

Quote (ChiefinspectorJ)

Another apartment complex in Florida has been ordered evacuated as a precaution after city officials became concerned over a recent report about the buildings:

North Miami Beach building deemed unsafe, evacuations ordered

This 1 is getting more confusing because I read another report earlier today that they have another engineer's review of the building which states that the building is safe. There is some work needed but nothing if life-threatening nor require evacuation of the building. Supposedly the engineer who did the 1st report was not a certified SI.

Engineering as a profession has to stop blaming itself.
It started with the Iron Ring to keep us humble but that is being used against us now. We are surrounded by corruption and ineptitude all the while trying to build something safe.
We are given all the responsibility and yet have none of the authority to make it safe and keep it safe.

Developers cutting costs, adding features, moving around stuff, rush push hurry - all crank up the chances of a bad design, that the non-engineer developer is not responsible for. We're the fall guy, literally.
Construction missing rebar or using substandard concrete, failing to read drawings and instructions, cost cutting - all crank up the chances for bad construction.

Of course, as humans engineers make mistakes. But us having no balls to stop the non-engineers, such as Building Departments, Inspectors, Unsafe Structures, Condo Boards etc. from failing to properly maintain the structure needs to change. Even the "40 year" number came from a politician, not science.

If a building is not properly maintained, it doesn't seem to matter as engineers can still do NOTHING. Write a report and oh well. A building should never be literally run into the ground.

Although, it is best for Champlain that some engineering flaw is to blame, that does absolve everyone and place the liability off the town, condo board etc.

Hilti provides some guidance for Special Inspection testing of epoxy anchors, here is the portion on proof loads. My opinion is that when installing any anchor into degraded concrete, that becomes a limiting factor on the allowable test load. A good summary of the considerations driving the selection of a proof load is included.

Quote (https://ask.hilti.com/article/special-inspections-...)

Proof loads – The establishment of proof loads should recognize the primary objective of proof loading as stated above, i.e., sufficiently high to provide assurance of correct installation but not so high as to result in damage. Given this objective, it should be clear that proof loads are set as a percentage of the tested tension capacity of the anchor, not the anchor design tension load. Historically, proof loads have been set at twice the allowable tension load. Given that the global safety factor used for anchor tension strength in allowable stress design has historically been set at 4.0 (inspected construction), the proof load represents approximately 50% of the mean ultimate anchor tension strength uninfluenced by edges, member thickness, etc. Note that, depending on the embedment to diameter ratio and the steel grade, this load might or might not subject the anchor to yield level stresses. For most mechanical anchor types using high-strength steels and typical embedment to diameter ratios (7 to 9), this is not a problem. Where lower yield steels are used, it should be verified that the proof loads do not exceed 80% of the nominal yield stress of the steel anchor components. Since the purpose of proof load is to verify proper installation, proof loading equipment may have load reactions close to the anchor but with sufficient clearance so any movement would be visible.

Quote:

Coverup is how many of these places operate.

Yeah. I'm not normally a "conspiracy theorist" but the way this thing was handled (the demolition) and the lies being told by the politicians begs one to ask what they are hiding. One doesn't blatantly lie like that without a reason. I mean, this "storm" they are so worried about--and STILL using as justification--I've lived through many of these. We'll lucky if we even see rain-the storm track is a LONG way from Surfside. The daily storms we get down here this time of year are about all we will see (and we saw them last week during the initial rescue attempts). It hasn't really been tracked for South Florida since even before the demo plans were made. And the lies about the pet searches (many have blown holes getting the politicians to contradict themselves). And the lies about the "rescue" vs "recovery."

The ONLY good decision they've made in this is they chose CDI, who I agree are the best in the business--if anyone could do this properly it would have been them.

As for this storm, anyone who knows me knows how seriously I take storms. I have a boat (which takes a day + for storm prep work) and a few other responsibilities for storms (my house, parents house, work). As such I have often been accused of being TOO careful for storms... This weekend I was replacing a fuel pump on the boat and running a few errands--no storm prep at all.

I have a simple rule: Don't lie to me. Don't tell me what I want to hear. Tell me the truth. I may not LIKE the truth, but I will respect you if you tell it. I don't shoot the messenger... (and the words "I made a mistake" gains even MORE respect from me). Lie to me (especially when you are a terrible liar) and I will NEVER respect you or believe one word out of your mouth again. After that, if you tell me the sky is blue, I will require peer reviewed studies before I believe you.

I don’t think anyone has mentioned the “plumbing” repairs done in 2017 to address leaking pipes in the garage, at least some of which had been invaded by roots from the entirely unwaterproofed planters (NBC Miami). This may coincide with the disappearance of the palm trees and the failed crack repairs.

People don't like hearing that their loved ones aren't worth recovering. Using the storm as an excuse to complete the demolition is merely for optics. Remember the Hard Rock in New Orleans. It wasn't safe for body recovery so the remains of two individuals remained in the building, apparently visible to the public. Even my mother, some 2000 miles away with absolutely zero connection to the incident was deeply troubled for some irrational reason. She wanted a living person to risk their life to recover an obviously dead body which she never knew.

Quote (ChiefInspectorJ (Specifier/Regulator)5 Jul 21 19:19
Ok Take a look at this!)

TWO PEOPLE SITTING ON THE BALCONY???

YES!! I have studied it for 4 hours.

Here's the best available view of that balcony that I've been able to locate:

Quote (KingBobo)

Here's the best available view of that balcony that I've been able to locate:

Well there goes another theory into the crapper.

“ Here's the best available view of that balcony that I've been able to locate:”

Ah, so that’s why they call it a “poop deck”

I was checking out photos of the place on
https://www.condoblackbook.com/surfside/champlain-... . I wasn’t sure if this was something or not. To me it look like the driveway might have a ridge. I wasn’t sure if this lined up with a beam.

The pic I have was taken last night around 10:pm ish as the building was collapsing.
They are flower pots but that's not what is in my pic. Look at it closely if you dare. I have investigators looking into it. We are skirting the realms of metaphysical engineering. I know Engineers don't like irrationality..

Quote (ChiefInspectorJ)

The pic I have was taken last night around 10:pm ish as the building was collapsing.
They are flower pots but that's not what is in my pic. Look at it closely if you dare. I have investigators looking into it. We are skirting the realms of metaphysical engineering. I know Engineers don't like irrationality..

What KingBobo posted in his picture is in the exact same location is the "people" you are seeing. I think you may need to get a new set of glasses! ;)

The f*** does metaphysical mean?

Because Google can't provide a meaningful definition. I've heard the word used here and there but never could figure out what it means.

This is the closest to what I've always understood it to mean:

https://www.merriam-webster.com/dictionary/metaphy...

https://www.merriam-webster.com/dictionary/metaphy...

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
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The secret of life is not finding someone to live with
It's finding someone you can't live without

Probably because metaphysical has some irrational definitions

I like this one

Quote (https://www.yourdictionary.com/metaphysical)

Designating or of the school of early 17th-cent. English poets, including esp. John Donne, George Herbert, Richard Crashaw, and Abraham Cowley, whose verse is characterized by very subtle, highly intellectualized imagery, sometimes deliberately fantastic and far-fetched.

This one I like less, but it is probably closer to current usage

Quote (https://en.wikipedia.org/wiki/Metaphysics)

Topics of metaphysical investigation include existence, objects and their properties, space and time, cause and effect, and possibility. Metaphysics is considered one of the four main branches of philosophy, along with epistemology, logic, and ethics.

I prefer physics - the study of things I can lay my hands on.

I think a better word might be Pareidolia - the tendency to perceive a specific, often meaningful image in a random or ambiguous visual pattern (Webster’s)

A main branch of philosophy and it can't even be defined? Dang it all, I'm here to expand my knowledge, not have my assumptions reaffirmed.

Js5189, so you're saying metaphysics is a symptom of schizophrenia?

Quote (TugboatEng (Marine/Ocean)5 Jul 21 23:53

Js5189, so you're saying metaphysics is a symptom of schizophrenia?)

The universities call it Political Science.

Quote (FacEngrPE)

I prefer physics - the study of things I can lay my hands on.

That's chemistry. Or perhaps sexology.


spsalso

I can see your porn folder.

I know i'm beating a dead hourse...

Quote (Oxford Languages)

met·a·phys·ics
/ˌmedəˈfiziks/
noun
the branch of philosophy that deals with the first principles of things, including abstract concepts such as being, knowing, substance, cause, identity, time, and space.
"they would regard the question of the initial conditions for the universe as belonging to the realm of metaphysics or religion"
abstract theory with no basis in reality.
"the very subject of milk pricing involves one in a wonderland of accounting practice and a metaphysics all its own"

SF Charlie
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Metaphysics (noun): Nonsense, woo-woo, bamboozlement, bunco, chicanery, malarky, flimflam, flummery, humbuggery, mountebankery, pettifoggery, skullduggery, legerdemain, lunacy, dupery, junk science, pseudoscience, fiddle-faddle, claptrap, tomfoolery, twaddle, hogwash, hokum, and hooey

I wish I had posted while it was still on my screen... (paraphrasing)

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Eat this before going to bed and melt belly and arm fat

SF Charlie
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Up there someone posted this article from the historic preservation society and I was wondering if someone could explain the coastal construction line as it applies to structures on beach exposed property… is this calculated by a flood study? And what impact would it have to the current catastrophe? They seem to think it’s critical in the explanation of interference from the neighboring construction.

https://www.townofsurfsidefl.gov/docs/default-sour...


Apologies for asking something that may be obvious, I make a different kind of universe at work and also pretty freaking far from ocean

The pic of the balcony looks like 2 concrete planters, one of which has a lame and crooked palm tree

Quote (illustr8r)

Up there someone posted this article from the historic preservation society and I was wondering if someone could explain the coastal construction line as it applies to structures on beach exposed property… is this calculated by a flood study? And what impact would it have to the current catastrophe? They seem to think it’s critical in the explanation of interference from the neighboring construction.

Construction eastward of the CCCL requires approval from the city and FDEP. There is construction east of the CCCL up and down the coast on a regular basis. FDEP hands out approvals relatively easily. This is also a VE flood zone which further complicates modern construction by utilizing frangible (breakaway) walls that are parallel to the ocean.

The Coastal Construction Control Line (CCCL) Program regulates structures and activities which can cause beach erosion, destabilize dunes, damage upland properties, or interfere with public access. CCCL permits also protect sea turtles and dune plants.

Building Official, FL & PA
The Building Code Forum

Ok, why is it so hard to find aerial photos of the new pile? There were hundreds available before the demolition but maybe one or two post-demolition, and all from street level.

We keep hearing that the demolition went perfectly, which it appears that it did, but how the west half came down, and where the rebar was and wasn’t is of significant public interest as well.

This event has obviously raised concerns elsewhere. Here's a video from the parking garage of a condo complex in Key Biscayne that was built in 1971.
Key Biscayne

Quote (js5180)

Ok, why is it so hard to find aerial photos of the new pile?

My experience is that the rescue team will be getting daily updates to aerial photography through Pictometry. It may be flown privately or by a commercial source but access to this new imagery may be limited during the declared emergency.

Speaking of photography and videography, it would have been cool if they had placed some sacrificial cameras in critical locations inside the building and broadcast video while it was collapsing.
It was an opportunity to see just how this building collapses, by viewing an actual part of the original building as it failed and fell.

Who says they didn't?

John R. Baker, P.E. (ret)
EX-'Product Evangelist'
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

Quote (JohnRBaker (Mechanical)6 Jul 21 03:48)

Who says they didn't?

Yes!

demolition companies often document their "shots"

SF Charlie
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Quote (Warrenslo)

warrenslo (Structural)4 Jul 21 23:56
Apparently as of May 26, 2021, there was a crane on 88th (north side of building) with outriggers sitting on the garage structure carrying roofing supplies and "tar" to the roof. Maria Notkin of Apt. 302 made the initial complaint - she appears to be the same unit who called their relatives from their landline multiple times after collapse. They were asking for the crane to be moved from 88th to Collins, the association said they needed the crane on 88th to reach the entire roof. See page 40 of email communication documents uploaded by the city. Link

Reading through this I’m wondering if they could of overloaded the garage ceiling with the tar kettle. I’m having a hard time finding what the weight of a tar kettle is full. The weights I’m finding is up to 5000 lbs but I’m not clear on if that’s full. The way Maria describes the location of the kettle I’m guessing it to be on the red in the graphic. She describes the kettle being under the condo units. I’m assuming that to mean under the balcony or close to the building.



I’m guessing based on her living in a 2 bedroom 2 bath and the fact she is on the north side that her condo is located in the yellow.


I wish there was a diagram showing how it all went together. I did a bit of guessing so take this with a grain of salt.

I agree, Mr. Wiley.

NIST has been there a week. They have had enough time to act on ideas such as yours. As true professionals from the Federal government, I have no doubt they have done those very things. And we will eventually, in a year or five, see them

Too much? Yeah. I couldn't help myself!


spsalso

controlled-demolition.com/media
CDI doesn't seem to have this up on their site yet, but how can they resist posting such a text book example of what they can do?

SF Charlie
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How the Surfside tower was imploded in just days: Hours of drilling, 128 lbs of dynamite
(nice ground level shot of the "new" pile)

SF Charlie
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Watch Live: Champlain Towers South Aftermath
YouTube channel BecauseSurfside has a live feed looking down on the recovery effort

SF Charlie
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Lizard - there were two tar kettles on the roof at the time of the collapse. They aren’t heavy. They are under the DOT limit for trailers requiring their own brakes - this includes tar kettles, air compressors, small household trailers, etc.

Link to 12 years of CDI Demolition Videos
The Art of Demolition, a compilation, 10 minutes of clips of jobs back onto the 1980's, and perhaps older. One of these is from my employers site.

Quote (Js5180)

Lizard - there were two tar kettles on the roof at the time of the collapse. They aren’t heavy. They are under the DOT limit for trailers requiring their own brakes - this includes tar kettles, air compressors, small household trailers, etc

Those are tar buggies and are just used to transport the tar that has already been heated. The one in question is the larger type that have all the heating equipment built into them etc. I've never seen them place on the roof they are usually placed on the ground in the heated product is either piped to the roof or dumped into buggies like are shown on the roof and lifted to the roof or other place they are being used. They are much larger and heavier.

I can understand that many people here are searching for a trigger event, but I think we're all missing the point here.

What ever scenario anyone is coming up with - column being hit by a truck, something falling off the roof, sea level etc, unless there was a fairly large scale subterranean collapse / sink hole, this building should not have collapsed.

It is only because there were multiple failings and damage from corrosion to the structure, almost certainly starting somewhere on the pool deck slab, combined with some spectacularly weedy reinforcement / punching effect that as someone posted early on that this building had simply reached a level of terminal overall fabric damage and hence some minor event, or simply final failure of a highly corroded reinforcement triggered progressive collapse of the parking roof structure and finally pulled over two or three of the columns or they failed in buckling due to lack of support.

The building nearly survived lets not forget looking at the tik tok video apparently showing at least one column collapsed, but the building just started to find alternative load paths which then failed due to the overall poor design and maintenance of the structure.

This then is the conundrum for many structures - outwardly they seem perfectly serviceable with no one doing a design check to todays standards for the basic design, damage that can't be seen or required destructive investigation to a living building and a very slow gradual deterioration and reduction in the factor of safety until it gets to less than 1. I don't find it difficult to believe that the owners didn't really want to or couldn't find the additional capital required to essentially half re-build the structure. I can imagine mortgage companies are suddenly thinking to themselves how can we lend money to buy something which may fall down or may become essentially worthless if you then need to spend 30-50% of the "value" of the property after 30-40 years to stop it falling down.

So yes, in the fullness of time someone might find the smoking piece of straw that broke this camel, but that shouldn't obscure anyone from thinking we can just fix that issue and it will be alright. It won't as some other straw could have easily brought this building down.

I don't know enough about design of buildings like this to know if what appears to be a major factor - the pool deck and first floor being designed and built as one monolithic slab - is common place or not. If it is then lots of buildings are in trouble down there, but if this is a bit of an oddball design then it might be ok.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

https://www.enr.com/articles/52048-implosion-enabl...

Article where CDI mentions soft concrete and as built not matching 1979 plans in basement area

Quote: "Concrete testing at the Champlain Towers South condo last year “yielded some curious results,” engineering company Morabito Consultants wrote in an October 2020 report obtained by The Miami Herald."

Could curious have something to do with CDI's Soft Concrete Comment?

A comment was made earlier that people are spending too much time looking for the straw that broke the camels back and I agree. We need to focus more on the original design and mistakes there that made the building so vulnerable to collapse. There are many indications in the original plans that the design was inadequate including punching shear of the pile caps and floor slabs and generally weak connections at the columns.
One thing that you can see in the news right now are statements from structural engineers that the north building is safe because “we did an inspection blah blah blah...”. It is not appropriate for engineers to make a statement like this about the north tower being safe without definitively knowing the cause of the south tower collapse. Remember that despite the media’s interpretation that poor maintenance caused the collapse there really is no documented evidence from morabito that shows spalling and rebar corrosion of such severity that collapse would occur in three years. This is a very strong indication that the underlying cause was a design flaw which by logic is in both the south and north towers.

I think it's useful to identify as many potential triggers as possible. Some may be relatively easy to eliminate or mitigate in the future. Understanding the collapse from beginning to end is how we learn to prevent it in future. We shouldn't put all the focus on the trigger, as there are other very important contributing factors, but it's wrong to ignore it.

In the Swiss cheese model, every hole you plug stops the disaster if they align. The trigger is one of the holes.

Quote (timwaits1)

We need to focus more on the original design and mistakes there that made the building so vulnerable to collapse. There are many indications in the original plans that the design was inadequate including punching shear of the pile caps and floor slabs and generally weak connections at the columns.

The building code has changed significantly since this building was built - methods used then aren't allowed today. With that said, if those methods were inadequate, it would have collapsed during or shortly after construction when loaded. The discussion I put forth in prior posts is why is a modern roof anchor loading test being performed on an older structure which may not be able to withstand such test. These inspections (which typically consist of tests) were done 14 hours prior to collapse per the city.

Quote (timwaits1)

One thing that you can see in the news right now are statements from structural engineers that the north building is safe because “we did an inspection blah blah blah...”. It is not appropriate for engineers to make a statement like this about the north tower being safe without definitively knowing the cause of the south tower collapse. Remember that despite the media’s interpretation that poor maintenance caused the collapse there really is no documented evidence from morabito that shows spalling and rebar corrosion of such severity that collapse would occur in three years. This is a very strong indication that the underlying cause was a design flaw which by logic is in both the south and north towers.

It is perfectly ok for a licensed engineer in their best judgment to state a building is safe for occupancy. Otherwise, many older buildings in this country would not be allowed occupancy. Safe for occupancy doesn't mean compliant with all current codes, it's not feasible to upgrade every older building to today's codes, that's why generally only the most important buildings are constantly upgraded (i.e. hospitals, 911 call centers, etc.) The remaining are upgraded for important elements (i.e. sprinklers, fire protection, electrical, backup power, etc.) This building had extensive concrete repairs less than 10 years ago per drawings uploaded by the city - it was not in as bad of shape as everyone makes it out to be.

Quote (timwaits1)

Remember that despite the media’s interpretation that poor maintenance caused the collapse there really is no documented evidence from morabito that shows spalling and rebar corrosion of such severity that collapse would occur in three years. This is a very strong indication that the underlying cause was a design flaw which by logic is in both the south and north towers.

The media's interpretation is because Morabito immediately hired a PR firm (their name is in all their statements) after the collapse. The media typically just reports these press releases verbatim - they are pretty lazy. The north tower is in much better shape according to those who have inspected it and had a different design (studio vs. 2br at x10 unit) at/near the point of collapse. The north building does not appear to have any fall protection installed (none really is needed, the building can be accessed from a cherry picker as we saw after collapse) and the east building appears to have a different type of fall protection system from aerial photos.

Quote (Thermopile)

https://www.enr.com/articles/52048-implosion-enabl...

Article where CDI mentions soft concrete and as built not matching 1979 plans in basement area

In one area, for example, the columns measured 24 in. in diameter, while the plans showed them to be 16 in. in diameter. On the other hand, Loizeaux reported, columns in one section of the building should have been constructed with 6,000-psi concrete, according to the plans. Instead, he estimated—without verifying via testing—the concrete’s actual strength was “not even close” and “much softer” than 6,000 psi.

Loizeaux did not observe much corrosion in the reinforcing steel. “I didn’t see any poor construction methods," he adds. "I didn’t see anything like that.”

Interesting larger columns, softer concrete, and rebar in good shape.

Quote (la belle vie)

I would add to MOJOJOHN's list that inspection reports should be required to more fully describe failure scenarios that could occur based on the building design, and then postulate a sequence of events where the observed deficiencies eventually lead to failure.

For our Dam Safety Inspection & Hazard Analysis Reports we include a Potential Failure Mode Analysis(PFMA), a.k.a. Failure Mode & Effects Analysis (FMEA). Part of developing the PFMA usually includes a round table discussion involving a representative from the various applicable involved parties such as different federal & state regulators, owner, operator, emergency management, first responders, the consulting engineer, etc.

Triggers aside, the most troubling aspect is how little warning there was that the building was in imminent danger of collapsing.

What was it? Perhaps at most 10 minutes between the calamity in the garage level and the rest of the collapse? Even the FIU bridge was waving its figurative arms shouting, "DON'T INSTALL ME!" as soon as the concrete forms were removed - days before it fell. Is it not possible for a 40-year old concrete structure to give clear warning signs at least 24 hours in advance that everyone needs to gather their belongings and evacuate?

The owners at Champlain North should consider retrofits that make it impossible for the pool deck slab to pull down the building.

Unless someone instrumented the building, it's not clear that there would have necessarily been any human observable "signs."

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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It would seem to require monitoring strain gages placed at all critical points. Once destructive motions initiate, its obviously too late for warnings.

I'm an outsider asking a question 'cause I do not know. (I'm not being rhetorical).
Bridges are supposed to be "redundant" (Yes, I know the FIU bridge claimed redundancy).
How can a condo building be redundant and economic? Should the cross beams be strong enough to withstand a column failure? Like I said, I don't have an answer.
By the way, I don't see crossbeams in the wreckage. What takes their place (carrying the tension and compression of the truss that is the building)?

SF Charlie
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Looking ahead - a link to a ceiling in garage of a Biscayne condo -
I would suggest a yardstick be used to monitor this cracking. The condo assoc manager is aware of the video - - - - watch for the display of urgency - -
https://www.youtube.com/watch?v=y33JbmcUnUI

If he is taking action where is the shoring?

I believe that huge "crack" has been identified as an expansion gap between the garage and tower.

Quote (SFCharlie)

How can a condo building be redundant and economic? Should the cross beams be strong enough to withstand a column failure? Like I said, I don't have an answer.
By the way, I don't see crossbeams in the wreckage. What takes their place (carrying the tension and compression of the truss that is the building)?

The function of cross beams (resisting sideways movement) is performed by shear walls. They will be found around the elevators and stairwells (where they also provide fire protection) and some other places throughout the building. Just Google shear walls to find out more. There was some discussion in the first thread on this topic about the shear walls in this building being barely adequate for the oceanfront location and environment, primarily wind loads.

I'm sure someone else who is more familiar with the construction of buildings like this will be able to answer your first question.

Quote (SFCharlie)

By the way, I don't see crossbeams in the wreckage. What takes their place (carrying the tension and compression of the truss that is the building)?

This building, and most like it, are not trusses; they're more like simple orthogonal frames. What little shear is developed by wind loads and the occasional seismic jolt is reacted by some few shear walls usually located near the core. It is common for elevator shafts to be reinforced to react the shear. It gives me the heebie-jeebies, but it seems to work where it works.

Here in the SF Bay Area this building would probably not have lasted through the 1980s. Our codes demand massive shear braces on relatively close spacing. In many buildings from the 1970s you can see retrofitted X and V steel shear braces just inside the windows installed after the Loma Prieta quake.

Quote (SFCharlie)

How can a condo building be redundant and economic? Should the cross beams be strong enough to withstand a column failure? Like I said, I don't have an answer.

Codes, I think. If they all have to be redundant, then redundance is sufficient instead of inefficient. Code enforcement should keep insufficient from being an option.

Hi, Charlie. You are right on target. Redundancy costs money. Redundancy reduces risk. Redundancy can extend the life of a structure which may experience slow degradation from the elements or from wear. How do we decide the tradeoff?
Mostly thru the building codes which are intended to provide "overhead" in the form of extra capacity if needed, account for small design flaws, and allow for construction tolerances. In this case, the use of higher strength concrete would have increased capacity and provided better protection of the reinforcing (reducing the rusting), more concrete cover to protect the reinforcing, and thickened sections of the floor slabs at the top of columns, to name a few. All of which cost money.
You asked "Should the cross beams be strong enough to withstand a column failure?"
I think you are referring to the flat slab of constant thickness each floor - that is a weak spot in this design. The cross beams I am aware of were in the parking ceiling where building columns did not align with parking area columns. And there is the real likelihood that had there been beams formed in the slab and connecting the columns in a grid, effectively forming a frame, this structure would have been much stronger. On the other hand, it served safely for 40 years, and would have served longer if not for the deterioration of many elements.
Engineering learns as we go, and this was an acceptable method of construction 40 years ago. Hopefully it is not used a lot today.
Good designs and good construction can create a better investment in the long term, but that can all be lost if not maintained along the way. Kinda like changing the oil in your car.

Quote (Murph 9000 (Computer)6 Jul 21 18:34
I believe that huge "crack" has been identified as an expansion gap between the garage and tower.)

Murph - we have learned here that such a joint would be a good thing, I think. But that is a really random and unintended looking joint as I see it. Is the slab holding level across the 'joint'?

Some items that have changed in our building codes that may mitigate against this kind of failure:
- Concrete durability specifications, especially for coastal and snow areas, have become more significant. W/C ratios and concrete strength requirements to prevent chloride intrusion have been adapted.
- Lateral loading for building designs have been significantly increased. Seismic design requirements have been added and wind loading has been adjusted up.
- Flexural driven punching shear for thicker slabs has been addressed in the 2019 update.
- Ties and stirrups are now required to be closed with 135 deg bends in many circumstances due to seismic concerns and torsion.

This is premature since we still don't know what went wrong. However, for those of you in the "We must do something" crowd, rest assured that if a building containing an engineering office fails, it might be because our design manuals and building codes now weigh 3 to 4 times as much as when this building was designed.

Quote (Teguci (Structural)6 Jul 21 19:54)

it might be because our design manuals and building codes now weigh 3 to 4 times as much as when this building was designed.

Yes! When the regs become unusable, they become useless.
Also, Having the regs on line in a searchable data base, not only saves weight, but the engineers time looking stuff up.
Also, if we are making drawings on computer, Some smartypants computer systems team can make software to read and analyze, and even add rebar etc. as per the code. (we do this to design computer chip of multi-millions of elements now, and have been building this software since the late '60s)

SF Charlie
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There is middle ground between a fully redundant structure and a structure having details prone to completely unzipping if one thing goes wrong. Even if the investigation concludes that the problem did not come from progressive punching shear of the pool deck, it seems like a bad practice to design something that will progressively fail in a brittle manner. At least detail for ductile failure as is done in seismic zones.

Quote (Vance Wiley)

Looking ahead - a link to a ceiling in garage of a Biscayne condo -
I would suggest a yardstick be used to monitor this cracking. The condo assoc manager is aware of the video - - - - watch for the display of urgency - -
https://www.youtube.com/watch?v=y33JbmcUnUI

I posted a long video of that same damage earlier today at 02:52 it had some follow-up about the damage also. Instead of a TicTac video it was a new story that ran about 3 minutes.

The vision of that Key Biscayne building does look like a joint, either a construction joint or a movement joint. In either case, it is ugly, and needs to be investigated and repaired.

SFCharlie, Unfortunately while they are convenient, searchable codes are a two-edged sword. I find many engineers avoid reading the full code and hence miss understanding the interactions of the various sections when it is so convenient to simply search up some detail they need at any given moment, copy/paste and move on.

Redundancy in my experience is not practical in run of the line commercial structures or even offshore platforms. It is not something that is designed into a structure, but something that results indirectly from the normal design process, such as designing a building to separately resist both N-S and E-W wind, but knowing that winds never blow from the both the north AND east at the same time. Or the low probability of having all floors with full live load applied. I've personally never designed any structure to be capable of standing if, for example a floor beam let go and fell onto the lower one, or for some armored car leaving the street at 60mph, crashing into and taking out a first floor column. If an offshore platform loses one of 4 or even 6 legs, its probably going to go totally under, but might survive because the current only flows one direction at a time. While waves could theoretically strike from multiple directions, that was never a design condition. I have designed various control buildings in refineries for blast shock requirements, but that has been the limit of my designed-in redundancy, which isn't really considered to be redundancy if it is a realistic design scenario.

Quote (Teguci (Structural)6 Jul 21 19:54)"...it might be because our design manuals and building codes now weigh 3 to 4 times as much as when this building was designed.''''

One thing I've noticed over the years is a trend towards "digitizing" engineering judgement. And that is one reason codes and design standards are growing in size.

Example: We compute live load reductions based on influence area. In the past engineers had to know what the influence area is, and how to compute it manually. About 20 years ago ASCE 7 provided a new variable, KLL ("Live Load Element Factor"), and a table listing the values for KLL. This factor allows computer programmers the ability to digitize the computation of reduced live loads, and it allows engineers to not have a clue as to how to compute reduced live loads manually.

In fact, the codes seem to be moving to reducing redundancy if anything. Or is that just my impression?

Quote (1503-44)

In fact, the codes seem to be moving to reducing redundancy if anything. Or is that just my impression?

It's definitely not just your impression. They are using the term "Value Engineering" to reduce the redundancy and strength of designs. As long as it stands or states together until it's paid for that's good enough is the prevailing attitude these days in many disciplines.

Back in the day, we'd design for lateral using X brace and moment frame. If we had a "shear wall" we would not consider that it actually resisted anything. It was an entirely redundant element.
Now it seems to be the only thing keeping the rest of the things upright.

It used to be that design techniques were built assuming our knowledge of material properties and physical behavior were limited, this caused engineers to use large safety factors in design codes. Prior to design codes many things were marginally designed, with the result that boiler explosions were frequent, and bridges made with less well understood materials fell down. After looking at the bridge list I think there is some work to do here, most of the recent bridge failures seem to include some sort of human factors problem. The dramatic reduction in boiler explosions coincides nicely with the creation of the ASME Boiler code.

In any case as we have better design techniques, there has been a temptation to "optimize" the designs to remove "un needed" material. IE design margins have been reduced. Much of this reduction of design margin is valid, but in some cases reducing safety factors also create a requirement to add material (or perhaps a design property) where previously we did not know it was required, the design margin took care of it.

The discussion of the need for designing for ductile failure of reinforced concrete may be one of the cases that now more important, as the design margin no longer provides as much extra meat to the structure.

Quote (1503-44 (Petroleum)6 Jul 21 21:57)

Thanks for your reply

SF Charlie
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Its interesting to see that the columns punched through the slab and what is left of them look like half sharpened pencils. Punching shear theory assumes that the crack will form at the face of the column and radiate at a 45deg angle up and out, leaving an upside down cone shaped piece of slab atop the column. This did not appear to happen as it looks like the slab took some of the column concrete with it on the way down instead.

Quote (Mark R (Mechanical)6 Jul 21 21:32
Quote (Vance Wiley))

Mark - it was your post that prompted mine - and I did look for your source but it was farther back than I thought so I grabbed the youtube address. {was it a tiktok?} The comments by the condo manager are quite interesting.
I apologize for not crediting you. From your post : https://www.youtube.com/watch?v=uGYZIEQxf1I
What is your opinion about the condition addressed in that video?
It has since been described as an expansion joint. It probably acts as one today, but is it intentionally random and ugly? Without exploring and investigating it I would call it very serious until proved otherwise.

Quote (Awestruc (Structural)6 Jul 21 23:56
Its interesting to see that the columns punched through the slab)

and it looks like the slab took some of the column concrete with it on the way down

I would suspect weak concrete, demonstrating a failure in compression rather than diagonal tension.
Or perhaps simply crumbling.
I hope they investigate the quality of concrete in the slab and columns and compare the findings in the pool deck/courtyard with that in the building areas.

Awestruc, details of some of the column tops:

The middle part of the building's history is not considered. Major 2002-2003 work by A.T. Designs had a bunch of structural repairs, mostly balconies. Then again they were doing more repairs 2009. Column spall repair pg.172 chipping out concrete at columns was part of it and who knows if they did more bad than good. I'm not sure what stacks 01,02,03,04,12,14 and poolside 09,10,11 mean but they worked on those as well. pg. 17/218 many observations.
Link permit-09
Link permit-02
Can't find third permit link.

If a building is improperly maintained, there is water and saltwater ingress - at what point are the engineer's no longer responsible?
I'm reminded of people who don't maintain their vehicles, nothing left for brake pads and they refuse to pay for that repair and the mechanic lets them roll out of the shop.

Quote (lucky555)

nothing left for brake pads and they refuse to pay for that repair and the mechanic lets them roll out of the shop.

True in Florida where there is no state inspection requirement for sure. But it's not true everywhere.

Here is a video tour of the north tower, which I found by accident:

https://m.youtube.com/watch?v=arUOCTDRnCc

I have been thinking about this collapse for a bit now; I think there are several items that we (the construction community and the building structural engineering community) have to look at and potentially address. My observation is that these items can be broken down into four areas: 1) the initiating event for the collapse, 2) the progressive/disproportionate collapse, 3) design review/construction inspection, and 4) Post-CO inspection.

1. Initiating Event:
   To my mind, the initiating event for this is really only of primary interest if it wasn't extraordinary. Once the reports are written and that initial domino is determined, it may well be appropriate to modify the design codes to account for some type of additional "loading" or some type of additional member resiliency.
2. Progressive/disproportionate collapse:
   The progressive/disproportionate collapse is the scariest part of this unfortunate event. As a community, we have come a long way in addressing progressive collapse, but it has been accrued through tragic events like this collapse (Ronan Point, Oklahoma City, WTC). Most in the SE community would use the prescriptive requirements for continuity spattered throughout the various design codes for buildings like this. The more direct and robust design solutions are time-consuming and computationally intensive, not to mention they require substantial knowledge of the reinforcing and connections in the members.
   I was gobsmacked by the reinforcing of the columns where the parking slab punched. As best as I can tell, there was a minimal amount of top reinforcing over the columns and any bottom reinforcing over the columns was not sufficiently developed or lapped to form the catenary action that would enable the structure to "span over" localized column failures. I have not taken the time to scrutinize the construction documents, but I expect this bottom reinforcing condition would be typical for the building. I would be interested to see how a building with the same concrete strength and the same reinforcing ratios as the condo tower, but with the reinforcing detailing we currently use, would perform for a loss of column scenario. To return to the first point, if the initiating event was a vehicle striking a column in the garage area, perhaps we should explicitly design the structure above for a loss of column scenario or mandating the columns in these areas be robustly reinforced to handle a vehicle strike.
   Overall I think the UFC design approach for progressive collapse is a good approach, but I would like to see it developed into more of a standalone document that doesn't rely on ASCE 41 as much. Eventually, I would like to see ASCE produce a standard for progressive collapse that offers the use of the 4 analysis procedures listed in the UFC and mandates under what conditions the more rigorous procedures are used.
3. Design Review/Construction Inspection:
   Design Review in a lot of jurisdictions is depressing. I have dealt with major jurisdictions where code reviewers have requested information that is patently obvious on my design documents. To the point, my colleagues and I have questioned the ability of the reviewer to truly digest any important structural information. In many places, design review is merely a proforma check of loading parameters mandated by the Code. I know there are many jurisdictions that mandate some form of peer review, and by and large, I think that is a good thing, although these reviews can sometimes devolve into petty and esoteric comments. We need real review that validates the structure loading and identifies complete and robust load paths, both gravity and lateral. This also means we need building officials with a structural knowledge base and meaningful experience in design.
   In my first few years of practice, I attended a SEA meeting that looked at the renovation of the Georgia Dome. One thing from that case study that stuck with me was that the main tension ring in the structure was built with half the shear stirrups called for in the construction documents. This was a major marquee, public project, and the inspection scheme missed critical reinforcing on a primary design element. The more experience I have gained, the more troubling I found this incident. I think special inspections as implemented by the IBC have gone a long way toward making the actual structure reflect the design documents. That being said, it wasn't until the mid-2000's that a lot of jurisdictions got on board with the special inspection process. I have had limited experience with the Florida Threshold inspection process, and to be quite frank, I still cannot tell you specific items required by threshold inspections. A few years ago, I attempted to compare the Threshold Inspections with the standard IBC inspections, but I hit a brick wall and didn't find real answers. All this being said above, there is still a real disconnect between structures constructed before the implementation of a rigorous inspection process and those constructed after. I also think that all buildings constructed should have a repository of all the final construction documents and submittals, along with documents related to post-construction renovation/modification.
4. Post-CO Inspections:
   While a properly designed, constructed, and inspected structure is a good way to ensure a resilient structure with a reasonable lifespan, maintenance has a significant impact on structural performance over the long run. I know many of you in the SE community have run across your share of structures that did not have the upkeep to keep them performing as intended, just like this structure appears to have suffered from. I was not aware of Miami/Dade's post-CO inspection requirements. I think that is a good start, but I agree with some other posters that 40 years is likely too long a period to wait, given that most designs are geared toward a 50-year lifespan. I also like some other's comments that there should be some type of tiered inspection. I jumped into thinking about the ASCE 41 tiered evaluation. Perhaps we should be using an increasing level of scrutiny on a 20, 30, 40-year schedule. I think this is also important for more substantial structures that were likely designed and constructed in accordance with the state of practice at the time of construction but do not include considerations for phenomena (like progressive collapse) that have become increasingly important. For some structures, it seems unreasonable to wait for some potential future event (like a significant renovation) to trigger a review of the design and constructed condition

This was a little longer than I intended, and it may have rambled on, but I think it needs to be considered by the community, and it looks to the future for issues we can already identify and begin addressing.

Robert Hale, PE, SE

Quote (zebraso)

Quote (lucky555)
nothing left for brake pads and they refuse to pay for that repair and the mechanic lets them roll out of the shop.

True in Florida where there is no state inspection requirement for sure. But it's not true everywhere.

Actually these days there are more states that do not require vehicle inspections than states that do. Even in a number of states requiring pollution control inspections is diminishing.

Quote (Js5180)

Here is a video tour of the north tower, which I found by accident:

https://m.youtube.com/watch?v=arUOCTDRnCc

Great Find, I wish it was an online translator for the audio portion! Has anybody seen any place how much the North building have spent on repairs vs. the South building?

Thanks for the close ups Spartan5.
The brownish slab concrete definitely looks badly deteriorated compared to the Grey column concrete.

Quote (Mark R)

Actually these days there are more states that do not require vehicle inspections than states that do. Even in a number of states requiring pollution control inspections is diminishing.

My understanding is that in Florida even when they had vehicle inspection you could sit in your car while they did it. I don't know how they inspect the brakes without pulling the tires. Where I am the car must be put on a lift. Which begs the question of how superficial are the requirements. Without inspections you don't have to have bumpers or working headlights. Well ok. No brakes is another story. I think this is on topic and the subject has been covered, but it's just another illustration of how these things are neglected. I never saw as many cars on fire by the side of the road as I did in Florida (small sample size).

Quote (Mark R (Mechanical)7 Jul 21 02:47)

I wish it was an online translator for the audio portion!

If the video is captioned(it is), YouTube should allow you to turn a transcript on(3 dots under the right edge of the video, "open transcript". you can then copy and paste the transcript into google translate

A twin building that collapsed in Miami, an X-ray from the inside
[Music] [Music]
we are in the metro building but here one arrives with ice cream is entering by collins heading north and had than leave the car here look how good it looks it seems very safe very well maintained now we're climbing the ladder These are the entrance doors to the departments that work in this part which is the door entered your Department this department, I think there would be cut in the middle of the building and I think this department is like the rooms in this apartment the shear wall so yes we were in the other department to starting from this line taking a step further towards the area not only the sea I'd be moving the mountain of rubble so were the balconies of the collapsed building because it is the same architectural design the same company the same style for you to see when you see this progressive collapse how the balconies were stacked one above the other there is no one thesis there will be very few people takes account of 80% television went into exile this would be the first part of collapse because the one on the pool deck and down the pool the arms whatever the parking sector how many are we talking to here square a block say 100 160 meters approximately ah in the collapsed building is all this is what's missing [Music] the people who except play against skin soul sides and delivered to carrió is the pool already they say that he also lost a lot of water seemed to give better maintained than they showed the truth from the other building [Music]
Ah! I love google translate, it seems particularly bad at Spanish (specially weird since google is in silicon valley, which is full of fluent Spanish speakers).

SF Charlie
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This simulated view of the vantage point of the TikTok video comes from the Miami Herald. They also have a 3D rendering thing there too:



https://amp.miamiherald.com/news/local/community/m...

Looking at the column photos, the pool deck patio slab looks to have failed in negative moment bending.

Quote (Awestruc (Structural)7 Jul 21 02:49
Thanks for the close ups Spartan5.
The brownish slab concrete definitely looks badly deteriorated compared to the Grey column concrete.)

I recall the deck area was a concrete slab, waterproofing, sand, mortar bed, and the paver tiles.

This was posted by bones206

https://res.cloudinary.com/engineering-com/image/u...

One thing I noticed in the video of the North Tower is the condition of the ceiling in the garage. One part looks moldy and discolored while the other part is nice and clean. I assume the clean part is under the building itself, and the other is under the pool deck and patio area where water is getting through the concrete from above. Is there any other plausible explanation?

Quote (1503-44)

Back in the day, we'd design for lateral using X brace and moment frame. If we had a "shear wall" we would not consider that it actually resisted anything. It was an entirely redundant element.
Now it seems to be the only thing keeping the rest of the things upright.

Not to discredit your experience, but this is not at all the case with concrete frames.

In steel structures (building frame systems), the lateral systems are ~95% braced frames / moment frames as you mention. In concrete structures, it is EITHER concrete shearwalls or concrete moment frames (with a few exceptions - not relevant to this discussion).

In the case of this building, it would be entirely appropriate to use concrete shearwalls as the lateral system. Granted, the 'amount' of shearwall provided in the east-west direction in this building is woefully inadequate. Any practicing/retired structural engineer can see this without doing any calculations whatsoever. Literally two 8ft, 10" thick shearwalls for a 12/13 story building... There is no explanation for this in my opinion. 175mph wind, exposure D in this direction, youre looking at ~1500kip ultimate base shear. Considering half of that goes to each wall, shear stresses are nearly 800psi. Design strength of these shearwalls (10", 3000psi, #4 at 12" o.c. e.w. e.f.) is about 150kip. There are tons of (seemingly) non-participating masonry walls that certainly contributed to the lateral strength of this building. Otherwise, there is no way this building could withstand hurricane force winds.

The higher dark ceiling is under the living space and is coated with additional material. The pool deck level is 1'-6" lower and uncoated. The exterior parking and entrance drive is a third intermediate level.

I wouldn’t assume that any detail of the north building is identical, nor that one is an improvement over the other.

My sense, though, is that the north building plans are actually older, and they were expanded for the south building based on additional lot area.

I say this because in my lay opinion:

1. The shear walls are reasonable for the north tower but arguably insufficient for the long east wing of the south tower.
2. The aesthetics of the north tower balconies are better than the south tower’s, on the inside corner.
3. Subsequent engineering projects are usually focused on maximizing value, not improving aesthetics beyond the original. See: DC-9 and every Boeing that was ever stretched after the initial release. See also: the Great Pyramid. See also: One and Two Liberty Place in Philadelphia. In almost all cases, the later structure is an uglier, more economized version of the original.

Dold - I am equally floored by the weak structure here. I am a layperson that built a two-story house that I live in and I was required to build basement walls that were 14” thick and with #4 8” OC. At the time it was maybe a few yards of extra concrete and a few more wire ties, and yes, sure, it was 3500 mix. I also had a lot of #5 bar in critical areas.

But to hear that a 12 story shear wall was only #4 12” OC - wow. I had always assumed that you’d never even find #4 in anything like a column or a shear wall or anything commercial other than a plain old slab.

Quote (Sym P. le (Mechanical))

The higher dark ceiling is under the living space and is coated with additional material. The pool deck level is 1'-6" lower and uncoated. The exterior parking and entrance drive is a third intermediate level.

So I got it backwards. What we see is the deterioration of the added coating on the underside of the slab under the living spaces. That makes sense, and it's not as alarming as I thought. Thanks for the correction!!

Quote (SFCharlie (Computer) (OP) 7 Jul 21 03:21 Quote (Mark R (Mechanical)7 Jul 21 02:47) I wish it was an online translator for the audio portion!)

https://www.youtube.com/watch?app=desktop&v=ar...

The subtitles in the video are more accurate than the auto generated ones. This is a quick and dirty as many who don't understand Spanish may find the video more interesting with a better translation.

00:21 Estamos en el edificio gemelo, pero aquí

[We are in the twin building, but here]

00:24 uno llega con el auto ingresando por

[one would arrive by car entering from]

00:25 Collins en rumbo hacia el norte y tenía

[Collins going north and you had to]

00:29 que dejar el auto aquí.

[leave the car here.]

00:31 Miren qué bien que se ve. Parece muy

[Look how good it looks. It seems very]

00:34 seguro, muy bien mantenido.

[safe, very well maintained.]

00:38 Ahora estamos subiendo por la escalera que (se) colapsó.

[Now we are going up the staircase that collapsed.]

00:41 Esta es la parte que dá a la playa.

[This is the door that leads to the beach.]

(Music)

00:50 Estas son las puertas de ingreso a los

[These are the entry doors to the]

00:54 departamentos que (se) colapsaron.

[apartments that collapsed.]

00:58 Esta parte que es la puerta de ingreso a tu

[This part which is the entry door to your]

01:00 departamento, ¿Hubiera quedado en pié?

[apartment, would it have stayed upright?]

01:02 Sí, esta parte sí. este departamento, este creo que se hubiese

[Yes, this part yes. This apartment, this one I think would have]

01:05 cortado por la mitad.

[been cut in half.]

01:09 ¿Víste que se vé entre los balcones,

[Can you see that you can see between the balconies]

01:11 cómo que la parte del edificio se vé abierta?

[how that part of the building looks open?]

01:12 Yo creo que es este departamento,

[I think it is this apartment,]

01:13 las habitaciones de este departamento

[the rooms of this apartment]

01:15 Creo que acá el techo te da un poco la idea de done se corta la...

[I think here the roof gives you a little bit the idea of where the..]

01:17 El muro de corte. O sea que si

[The plane of the cut. In other words, if]

01:21 estuviéramos en el otro departamento, a

[we were in the other apartment, from]

01:22 partir de esta línea, dando un paso más

[this line on, taking one more step]

01:25 hacia allá, ya no habría nada, sólo el mar.

[over there, there would be nothing, only the ocean.]

01:29 Estaríamos viendo la montaña de escombros.

[We would be looking at the mountain of rubble.]

01:33 (Music)

01:38 Así eran los balcones

[This is what the balconies were like]

01:40 del edificio colapsado porque es el

[of the collapsed building because it is]

01:43 mismo diseño arquitectónico, la misma

[the same architectural design, the same]

01:45 empresa, el mismo estilo.

[builder, the same style.]

01:49 Para que vean ustedes, cuando ven ese

[So you can see, when you see that]

01:53 colapso progresivo

[progressive collapse]

01:55 cómo los balcones se fueron apilando, uno

[how the balconies stacked themselves, one]

01:59 arriba del otro.

[on top of the other.]

02:01 ¿No hay nadie en el edificio ahora?

[Is there anybody in the building now?]

02:03 Hay muy poca gente. Cómo te habrás

[There are very few people. As you may have]

02:04 dado cuenta, el 80% del edificio

[noticed, 80% of the building]

02:09 se exilió por voluntad propia.

[left on their own.]

02:10 (Sound cuts out so no transcript)

02:19 Las personas que decidieron tomar esta vía

[The people that decided to take this route]

02:23 y llegar hasta esta puerta de emergencia

[and got to this emergency door]

02:25 que estamos mostrando ahora,

[that we are showing now,]

02:27 son las que pudieron salvarse,

[are those that were able to save themselves.]

02:31 son las que pudieron ser rescatadas.

[are those that were able to be rescued.]

02:41 Si estuvieramos en el edificio que (se) colapsó,

[If we were in the building that collapsed,]

02:42 esta sería la primera parte que (se) colapsó,

[this would be the first part that collapsed.]

02:44 (Sound begins again.)

02:45 porque es la (parte) de la plataforma de la piscina

[because it is the part of the pool deck]

02:47 y abajo de la piscina está(n), los, los gara...

[and beneath the pool are, the, the gara...]

02:49 el, el, ...

[the, the]

02:52 lo que sería el sector de estacionamiento.

[what would be the parking area.]

02:54 (Music)

[]

02:56 ¿A cuánto estamos Alan aquí?

[How far away are we here, Alan?]

02:58 A una cuadra. (can't understand)

[One block away]

02:59 Un bloque digamos: 160 metros

[A block let's say: 160 meters]

03:02 aproximadamente.

[approximately.]

03:05 (Music)

03:07 En el edificio colapsado es todo esto es

[In the collapsed building all this is]

03:10 lo que falta.

[what is missing.]

03:11 [Música]

03:19 La gente que se salvó, pudo haberse encontrado

[The people that save themselves, could have been]

03:23 más de aquel lado.

[more towards that side.]

03:25 Acá arriba está la pileta está la pileta.

[Up above here is the hot tub(?).]

03:28 Y acá dicen que también perdía mucha agua.

[And here they say that it also would leak a lot.]

03:30 Pero este edificio parecería estar

[But this building would seem to be]

03:31 mejor mantenido de lo que

[better maintained that what]

03:33 mostraron en el otro edificio.

[what was shown of the other building.]

03:35 La verdad, pero bueno, es similar.

[The truth, for what it's worth, it's similar.]

Quote (Js5180)

I wouldn’t assume that any detail of the north building is identical, nor that one is an improvement over the other.

My sense, though, is that the north building plans are actually older, and they were expanded for the south building based on additional lot area.

I say this because in my lay opinion:

1. The shear walls are reasonable for the north tower but arguably insufficient for the long east wing of the south tower.
2. The aesthetics of the north tower balconies are better than the south tower’s, on the inside corner.
3. Subsequent engineering projects are usually focused on maximizing value, not improving aesthetics beyond the original. See: DC-9 and every Boeing that was ever stretched after the initial release. See also: the Great Pyramid. See also: One and Two Liberty Place in Philadelphia. In almost all cases, the later structure is an uglier, more economized version of the original.

Yes, the north building is only different near the assumed point of collapse (x10 unit is studio vs. 2br) and across the hall similar. The north building also didn't have the column dimension error on the x10 unit. Finally, the north building also seems to have been better maintained. Now the south building seems to have been complaining they couldn't access much of their building during the construction of the nearby building to the south. The south building also had roof anchors installed and most likely tested less than 24 hours before collapse. The north building didn't have this issue. Until proven otherwise this is an OSHA code issue and needs to be fixed!

This forum today was alot of BS so here is today's press conference link:
Link

Statement from a previous post...I also think that all buildings constructed should have a repository of all the final construction documents and submittals, along with documents related to post-construction renovation/modification.

Looking through the original plans You can see many red flags but one obvious thing is that the plans are not even close to being “As-Builts”. They are not stamped as such and contain a number of inconsistencies and missing details. Unfortunately this is very typical, even with buildings recently constructed. This is one thing that should change as we go forward. If you do not provide a proper set of as-built plans you will not occupy the building.

Alan knows it was the roof anchors but cant prove it yet, boom:
Link

Quote (Zebraso)

My understanding is that in Florida even when they had vehicle inspection you could sit in your car while they did it.

Yes this is today's OSHA roof anchor testing because there is no standard but it's "always required."

Quote (tmwaits1)

Statement from a previous post...I also think that all buildings constructed should have a repository of all the final construction documents and submittals, along with documents related to post-construction renovation/modification.

You're a structural engineer? Good luck!

Dold, No worries. Lots of ways to skin a cat and refinery structures are typically very conservatively designed. 4 function calculators were the only thing on the desktop besides dialup phone, pencil, sharpener, eraser and a pad of paper. Punch cards were for the PDP 11 pipe stress runs we did down in the basement.

I was also a bit horrified by the liberal use of what seems to be nothing more than a few #4 bars in many locations. We only used #4 for stirrups and pavement bars. As for punching shear, that was usually handled by concrete thickness alone. We'd use more concrete thickness rather than throw more steel in it.

Quote (warrenslo)

Alan knows it was the roof anchors but cant prove it yet, boom:

??? He didn't say anything about roof anchors in that interview.

this is probably the best simulation I have seen of the collapse sequence. Punching shear failure with the slab area between the pool and the building which induced lateral load on the line of building columns that failed first. This seems to follow both what is seen in the video and with what is seen in the debris pile.

Link

Please help an electrical to understand here. Do I understand the deck, which appears to be no thicker where it meets the columns, is reinforced by 12 X 12 pieces of steel that don't seem to be much bigger than the columns they sit on?

Quote (IEGeezer (Industrial)7 Jul 21 06:30)

...may find the video more interesting with a better translation.

Muchas muchas gracias

alma de piel (soul of skin) seems to be a brand of ice cream or a dance studio. Is this an Idiom?

SF Charlie
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Any thoughts on the NYT article?
See related DWG's that I could find for the SOUTH [not north] Towers

S.6 Second Floor Framing Plan (Pg.28 of 336) & (Pg.110 of 336)
Typical Notes
#5 at least 25% of all column strip reinf. shall be centered over the column as explained in typ. flat plate det. - see sheet S.11

S.11 Flat plate Sections and Details (Pg.38 of 336) & (Pg. 237 of 336)

S.5 Lobby Level Framing Plan
(Pg.31 of 336) & (Pg. 162 of 336) & (Pg. 210 of 336) & (Pg. 234 of 336)


https://www.nytimes.com/2021/07/03/us/florida-cond...

https://www.townofsurfsidefl.gov/docs/default-sour...

Please allow me to move the discussion to Miami Beach, Champlain Towers South apartment building collapse, Part 04, Thank-you.

SF Charlie
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Quote (dik)

Please close this post to new postings.

SF Charlie
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Quote (GPR_Tech (Civil/Environmental) 7 Jul 21 15:22 Any thoughts on the NYT article? See related DWG's that I could find for the SOUTH [not north)

Towers S.6 Second Floor Framing Plan (Pg.28 of 336) & (Pg.110 of 336) Typical Notes #5 at least 25% of all column strip reinf. shall be centered over the column as explained in typ. flat plate det. - see sheet S.11 S.11 Flat plate Sections and Details (Pg.38 of 336) & (Pg. 237 of 336) S.5 Lobby Level Framing Plan (Pg.31 of 336) & (Pg. 162 of 336) & (Pg. 210 of 336) & (Pg. 234 of 336)]

What I would say about this is that the original plans are so sloppy that its impossible to be certain of the slab reinforcement that was required at each of the columns. 25% of the "column strip reinforcement" is a very poor way to call this out in the plans and highly prone to an incorrect interpretation by the contractor. I'm sure someone will comment that this is common practice, however it is not best practice.

More likely a reference to a love song by Tito Rodriguez.
From where your inner feelings come.
A specific context would help.

Quote (1503-44 (Petroleum)7 Jul 21 15:48)

A specific context would help.

In the transcript:
00:24
uno llega con helado está ingresando por
00:24
one arrives with ice cream is entering by

03:19
la gente que salvo jugarse en contra
03:23
alma de piel lados
03:25
y entregado a carrió está la pileta ya
03:28
que dicen que también perdía mucha agua
03:19
the people who except play against
03:23
skin soul sides
03:25
and delivered to carrió is the pool already

Quote (SFCharlie (Computer)(OP)7 Jul 21 03:21)

SF Charlie
Eng-Tips.com Forum Policies

Before I saw Geezer's translation of the video, I made my own. After finishing that I noticed Geezer's translation, so I did not post my own, basically because Geezer's translation was absolutely perfect. There was no need to post an identical translation.

Geezer's Spanish text posted above exactly matches the video. At 00:24 the video reads

00:24 "uno llega con el auto ingresando por"
00:25 "Collins en rumbo hacia el norte y tenía"

one arrives by car entering from Collins [Ave.] towards the north and you have to leave [the car] there.

Nothing about "helado" ice cream, (gelado means cold, or freezing, as in "Estoy gelado. Or Estoy congelado", an "h" is silent, "g" nearly so, depending on regional dialects, and I dont see that or "Alma de piel" anywhere in the transcript. Neither do I see
"03:19
the people who except play against
03:23
skin soul sides"

"Is there some other transcript, not Geezer's, that you refer to?

Quote (1503-44)

capable of standing if, for example a floor beam let go and fell onto the lower one

The ACI (American Concrete Institute) code limits the maximum reinforcement in a concrete beam so that it fail in ductile tension (gradual and noticeable) rather than a shear failure (no warning) for just this reason. If the failure is slow and obvious, there is time to evacuate or shore up the beam, column, etc.

Yes, thats exactly what should happen, but it apparently did not, or the action was too fast between fatal crack initiation and failure, such as to allow evacuation. Max tension steel is not exactly a dynamic calculation either, so how long it should be in the ductile failure mode to allow safe discovery and still permit adequate response time? That is not exactly a specified amount of time. So did it take 3 years in an unrecognizable dire state of alarm? That's not a warning, if nobody gets alarmed. Was it cracking for 24h in a ductile condition, yet nobody heard or saw alarming cracks? Or was it dectile for only 10m after a smack by a drunk driver? It would appear that the potential for a rapid dynamics of failure mode needs to be addressed. It would appear that survivors had at best 10m. Thats bearly enough time to get out of a two story building in broad daylight, if I remember my earthquake experiences; I've had quite a few, at night, I could only get under the pillow.

Quote (SFCharlie)

Please allow me to move the discussion to Miami Beach, Champlain Towers South apartment building collapse, Part 04, Thank-you.

Quote (SFCharlie)

Please close this post to new postings.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!