Well, as bad as the collapse is, it is possible we can learn something from this collapse.There are an awful lot of similar buildings in florida, as well as other seaside communities.

Perhaps there should be mandated an annual survey of building foundation movement using laser technology , with results reported to county authorities and immediately available to building residents, investors, and insurance companies. It would seem that the insurance companies would be the first to push for such legislation. Certainly any investor in buying such an aged unit would require a detailed structural analysis before such a purchase, but it is also prudent to provide the individual condo residents to have timely access to such information, thus the annual laser scans. The negative side of such an approach is that there will occur a step change decrease in the value of some units.

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

If MY life were on the line, I would prefer those window-washing anchors to have another steel plate on the BACK of the column. Probably even skip the epoxy and use a smaller hole.



spsalso

Structural guys live dangerously... without doing any calcs, the anchorage is more than adequate for the 5K load, assuming the backing material is sound.

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

-Dik

https://en.idnpos.com/latest/nist-engineers-inspec...

Not relevant, but the poster of the twin towers in this bedroom made me pause.

I've never seen failures with rebar like that... looks like it just 'unzipped'.

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

-Dik

Quote:
RickyTickyTavi (Structural)28 Jun 21 14:16
2. Roof Anchors/Fall arrest system installation. If this was a post-tensioned building and the contractor repeatedly knocked out tendons with drilling operations, I could see this being plausible. But other than localized damaged/deterioration around the anchors, they are rather non-obtrusive in the short term. One minor comment on that design, I'm sort of surprised the original engineer went with a 2 anchor design - I had assumed the 4 anchor OSHA minimum would apply to fall arrest systems.

Should not be an issue.

Quote (dik)

Thanks for starting the new thread.

Quote (Lizard7709 (Civil/Environmental)28 Jun 21 03:06)

Thanks for the URL.

SF Charlie
Eng-Tips.com Forum Policies

Quote (SteveWag (Civil/Environmental)28 Jun 21 03:30)

three area drains

reminded me of this interview...
Condo Collapse: Former Maintenance Staff Manager Was Concerned About Saltwater Intrusion

SF Charlie
Eng-Tips.com Forum Policies

"Jason Borden, a structural engineer whose firm had conducted an hour-long site survey of the building in 2020, said what he observed "was typical of a 40-year old building that had had some deferred maintenance." That means that parts of the building had reached their "expected useful life" and needed to be repaired or replaced, but added that his team did not see anything out of the ordinary, and certainly nothing potentially catastrophic."

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

-Dik

IMO, that was a little EARLY to close the opening discussion.

Please read through at least the last 20% of the original thread and all of below to get an idea of the current state of the discussion.

I have several comments to make, but I have to leave for an appointment. Here is a start:

(1) Columns were not designed for penthouse loads
(2) Deck level; water damage; waterproofing damaged -- who should have alerted condo association to the level deck problem? When? Should the 1981 building inspector have required sloping to drains?
(3) Should columns be required to be safe even after losing 1 or 2 lateral supports in buildings with more than, say, 30 bedrooms (60 people)?
(4) Real estate agents get 6% every time one of these units changes hands, and how often does the condo association pay 6% of the buildings value for a full structural review?

My heart is beating just watching these videos and reading reports! Adrenalin in action as the situation is so frightening!

Quote (TugboatEng)

They needed an earthquake to undo some of that subsidence.

The "quake" was not a natural one and was too far off shore (over 100 miles away from the hypocenter (shallow underground explosion). Both P and S waves would have lost much of their energy long before arriving at the site of the condo. M3.9 packs a good amount of energy at the hypocentral source and normally only felt in dozen miles or so around it (depending on the medium through which they travel.).

Oceanic crust in that area is likely brittle basalt which can deaden the propagation of the wave energy.

That region near the condo, at that distance from the quake is not likely to be all that impacted, if at all. I would say, the "quake" was not a factor.

Quote (IMO, that was a little EARLY to close the opening discussion.)

It went on longer than it should have... a new thread should have started after about 200 or 250 replies, not 350...

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

-Dik

Back in 2010, there was a 5.0 in Toronto. The only way I knew it was happening about 60 miles away in Buffalo, was my monitor wiggled for a few seconds. It was otherwise not perceptible to me.

Edit: This was actually much closer to Ottawa than TO, closer to a 250 miles from TO and 300 miles from Buffalo

https://en.wikipedia.org/wiki/2010_Central_Canada_...

I didn't know it was a 5, but was there and you could feel the shaking 'through your feet'.

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

-Dik

Just something to add. A sat image of the pool/spa area. In my college days I was a pool tech. Often times the pump rooms for these systems would be under the deck. I would hazard to guess that the pump room was in the same space as the underground parking garage. These systems often have leaks and poor ventilation. While it may be a small factor, chlorine vapor in a humid environment can be highly corrosive to metal. As long as the pool was staying clean and the water parameters were correct there would have been little reason to go into the pump room. So its possible chlorine vapor could have worked its way into the exposed metal and drastically sped up rate of corrosion.
Just a thought.

One guy does admit parking in garage around 1am before collapse, but then leaving with a scooter. Claims his power was out in his apartment. No evidence that his car bumped into any columns though.

https://www.wlrn.org/news/2021-06-24/i-felt-the-en...

and...
"The Champlain Towers South condo building collapse began in the bottom of the building and brought the rest of it down with it in a 'domino effect collapse', experts said on Monday as questions grew over why repairs weren't done when the damage was identified three years ago by an engineer who inspected the property and found 'significant' cracks in the concrete columns in the parking garage.

Officials won't yet comment on what exactly brought the 40-year-old tower down but experts who have viewed footage of it say it started with a problem in the bottom of the building - perhaps the parking garage - and once that crumbled, huge swathes of the building came down with it.

Some experts say it could have been the result of eroded columns collapsing under the weight the building. The cause of the erosion could have been spalling, which occurs when salt air gets into the column and rusts the steel inside.

Frank Morabito identified spalling in the columns in the Champlain Towers South parking garage in a 2018 report. He also found damage elsewhere and recommended $12million worth of repairs but nothing was done to until this year, when the condo association board planned to overhaul the property to meet its 40-year recertification requirements.

Morabito broke his silence on Monday to release a statement saying he recommended the changes three years ago to the condo association - a board of seven volunteers, five of whom were living in the building and one of whom remains missing."

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

-Dik

Here's a clear photo of a non-involved column for what it's worth.

From the building drawings, the pool equipment area is to the south of the pool (left, in the picture above). Implied in the drawing is that you gain access to that area by moving through a "hallway" that is east of the pool--from the parking area. That does seem odd.


spsalso

Thanks "spinspecdrt", I had not noticed that.
Steve

Huh, the spa was added sometime later. The drawings only show the main pool. I would really like to know when that was done.

as per the interview referenced above by SFcharlie, spalling of concrete in the basement garage was in response to corrosion and swelling of the rebar due to salt water intrusion. The maintenance mgr claims that during his tenure (1995-2000) the garage would routinely flood to 2 ft depth of saltwater, and the salt water would seep thru cracks , and also enter normal portland cement based concrete due to its inherent porosity.

Florida has had other issues with salt water corrosion of rebar- many aged Florida bridges have similar issues with rebar corrosion , and I recall there was a FDOT project to address this by applying a coating of geopolymer cement over the concrete to impede the salt water ingresss- the geoplymer concrete GPC has over 1000 times lower porosity to salt water than does portland cement based concrete. Perhaps the same concept can be applied to underground and ground level concrete structures along the coast.

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

New photos from the pool equipment room. Condition was bad. But again, the pool above didn't collapse.

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

Pool equipment room picture 36 hrs before collapse. Contractor doing the pool equipment quote “There was standing water all over the parking garage”
“He thought it was waterproofing issues,” the contractor said of the staff member. “I thought to myself, that’s not normal.” He said Jose told him they pumped the pool equipment room so frequently that the building had to replace pump motors every two years.
The deepest puddle of standing water, according to the contractor, was located around parking spot 78 — an area that building plans show is located directly under the pool deck[...]"

This exact area was detailed in the R&R plans.

No, but the pool would be sitting on the ground so it wouldn't be putting any weight on the columns, and the deck around the pool wouldn't put to much load on the supports below. Also, that looks like a salt water system that's clearly been leaking. So even when the tide wasn't inundating the garage, the support columns were probably under a steady salt assault from the leaking pool fixtures.

4500psi and 1" cover... looks like a good start for the repair and maybe raises some issues about the guy's skill level...

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

-Dik

Some useful information on the NTSB's investigatory roll. https://www.local10.com/news/local/2021/06/28/team... . These investigations take time.

'Significantly Worse'
In a April 9 2021 letter Wodnicki [president of the Champlain Towers Association] noted that “indeed the observable damage such as in the garage has gotten significantly worse” since the first [2018] inspection.
https://www.usatoday.com/story/news/2021/06/28/mia...

A concrete guy can correct me, but I have the impression that doing durable concrete foundations and structures in and near salt water can be done.

I have the impression that this building was not built with such techniques; it seems there was an assumption that salt and salt water was kept somewhere 20 miles away. And it was built accordingly.


spsalso

My only experience is in bridges. In a tidal zone (which the basement apparently was, considering reports of sea water flooding it during high tides), this would attract the most severe exposure classification (C2 in Australia). This would call for a minimum 50 MPa concrete with 65 mm of cover (as a building). A bridge would need >= 55 MPa concrete with 80 mm cover. Often stainless steel would be used.

What was used was 4000 psi (~28 MPa) with apparently the bare minimum cover, perhaps 1 inch. There was no hope that this was ever going to be a durable structure.

I doubt they would have known or expected that the basement would have seawater flowing in when it was designed.

Architect here - Thank you all for your knowledge.
The drawings show parking level at approximately elevation +2'
The high tide on the night of the collapse was at elevation +3.1" at 9:04 pm. Higher than usual
(note: times do not exactly concur)
Is it possible the hydro static pressure lifted the foundation causing added load on the ground level deck against the columns.
Leading to the ground level deck punching through the columns
If this happened then I can imagine transfer beams failed.
EDIT: just noticed low tide was an hour after collapse
Maybe the cyclical nature of the tides and hydrostatic pressure
It could make sense at the pool area as there is not the weight of a building over it

https://www.enr.com/articles/52001-engineers-piece...

"the columns were not designed for Penthouse loads: (various posters)
That may be true, but on its own, should not cause a gravity load failure unless the structure was severely under-designed from the get go.
It is likely that this building only had 20% or less of the design floor live in effect at any time. That a lot of unused demand over 12 stories.

Here's a video that I haven't seen posted yet it's got some good speculation and pictures.
https://youtu.be/dSQq2FimiXY

Quote (spsalso)

I have the impression that this building was not built with such techniques; it seems there was an assumption that salt and salt water was kept somewhere 20 miles away. And it was built accordingly.

The building was oceanfront, less than 100 yards from the ocean. I don't believe there's a place in Miami that's 20 miles away from the ocean!

Based on ACI318-89, minimum concrete strength was 4750psi and w/c of .4.

Based on the current ACI318, it is exposure class C2 and is limited to minimum 35MPa (5000psi) concrete and w/c of .4 and 20 cover for slab bars and 40 cover for everything else!

So it has not changed a lot. Most of the concrete strengths used in the building should never been accepted.

Quote (I have the impression that this building was not built with such techniques)

It would appear that way... even the repair did not appear to have taken into account the corrosive nature of salt spray... have to wait for more information.

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 have a few thoughts:

1. Its very unlikely the penthouse, even if unaccounted for (which isn’t likely, as a recent interview indicated it was accounted for), to cause a failure. I agree with XR250 that the majority of the floors were likely no where near their design loads.

2. The complete degloving of rebar is very concerning and makes me question the ductility of older reinforced concrete structures. There could be many reasons for this degloving; I don’t know how much how quickly a load is applied effects this, significant rust or millscale on the rebar, etc.

I always thought that if you develop rebar, it should yield significantly prior to pulling out (if it all). Even in the video you can see 20’ sections of columns falling down like a toppled jenga. Nothing in the video looked like a ductile failure. I looked at photographs from northridge and saw similar rebar completely devoid of concrete.

3. All the photographs of the concrete columns I saw did not show a level of visible degradation that you’d expect to cause failure. If there was severe corrosion of rebar, there’d be spalling in those locations. So theres unlikely to be any significant hidden damage.

Quote (NOLAscience)

IMO, that was a little EARLY to close the opening discussion.

I meant early in "time", not early regarding number of posts

UNVERIFIED INSPECTION REPORT
Professional engineer Frank Morabito went into 68 of the units a couple of months before October 2018 inspection (between August and September of 2018). It sounds like 68 of the owners/renters were unhappy with the board's inaction on what they thought was evidence of serious damage. They hired the engineer for an assessment, and then the board had to follow-up with a full structural inspection and report. But time was not on their side.

THE April 9 2021 WODNICKI LETTER (76 days before collapse): The board recognized that the situation was serious, but they had ultimately lost too much time with political and financial issues.

THE OTHER CHAMPLAIN TOWERS
See photo at 3Engr1888 @ 27 Jun 21 03:04
Champlain Towers North is "Temporarily closed" as per Google Maps, 11:53 am 6/28. North seems to have a similar penthouse:
https://www.miamicondoinvestments.com/champlain-to...
East, built ca 1994, seems to NOT have a penthouse, built ca 1994
https://www.miamicondoinvestments.com//champlain-t...

These residents at EAST should also evacuate until that damaged column in the basement parkcade is shored up. Not 'repaired'. I'm assuming there were no changes to the footprint at North and East like the change at South that hetgen noted @ 26 Jun 21 11:25

FOOTPRINT REVISED

Quote (adamewood)

Responding to Ingenuity's post, please correct me if I'm wrong, but it seems column I-10 was originally designed as an interior column. At some point the decision was made to not construct this extension, making column I-10 an exterior column. Depending on how late in the game this decision was made, makes me wonder if it was ever analyzed for the increased live load distribution? Or was it simply a matter of "it's carrying less trib, therefore OK" ....then add in the planters installed on the corroded plaza-level slab. Is it possible the column was overloaded?

I'd like to see a single comment with the drawings of the garage, lobby, and the first full residential floor before the footprint was revised and after. I tried scrolling up and down to compare, but I'm too tired to do that tonight. Was this one column that was supposed to be within the building envelope exposed to the elements at ground level? Can you see this column in photos?

TIDES/HIGH WATER
The high tide on Wednesday/Thursday is interesting.

WOMAN BOUGHT UNIT IN DECEMBER; ANGRY AT UNDISCLOSED STRUCTURAL PROBLEMS
Unit 611: Monteagudo, age 50s
“I ran and tried to close it [window] but I couldn’t, I imagine because it was unlevel already because of all the movement,” she recounted. “I heard a crack and when I looked, I saw a crack traveling in the wall two fingers thick. Something told me, you need to run.”
She purchased unit 611 in December; was upset when she learned of structural issues after the sale. Extra $1000 special assessment was to start in July.

VALUE OF 40 YEAR OLD HIGH RISE CONDOS
I want to say that it seems to me that the value of a high-rise condo building built near the coast after _______ goes to zero at about 40 years, and this should be reflected in its price when it is sold at, say, 30 years. But this particular building seemed to have more problems than most, so idk.

That's about enough for tonight.

Let us assume a floor to floor spacing of 10'. Let us assume that spacing suddenly changes, on the bottom most floor, to 20'. Would that be a problem for the vertical columns involved? Would it be a problem if the rebar arrangement had not accounted for a lack of horizontal support at the midpoint of this "new" column height?

Again, a timeline of this event will be very interesting.


spsalso

Quote (Jerehmy)

1. Its very unlikely the penthouse, even if unaccounted for (which isn’t likely, as a recent interview indicated it was accounted for), to cause a failure. I agree with XR250 that the majority of the floors were likely no where near their design loads.

I agree that you are making a fair point. My concern is more about safety margins being on the thin side. Stuff happens. If your safety margins are a little thin, it may make the difference between something repairable and something that isn't. However, a better question may be: Why didn't it occur to someone to shore things up? Here we go again. The FIU pedestrian bridge was failing structurally and nobody thought to shore it up.

You can't snap your fingers when making structural repairs, but surely it can't hurt (except your pocketbook a little) to do some shoring.

It's not that Florida didn't have a Building Code, it is just that, before Hurricane Andrew, Cities & Counties had a very Libertarian application of the code. All that changed following Hurricane Andrew.
All over the US, up to the 80's Cities & Counties were quite parochial in attitude towards State Mandated Building Codes. That remained so in states like Florida & Texas, as stand outs.

Present day Florida Building Code - have the requirements updated after Andrew to incorporate any rebar corrosion protection? Plain rebar in ocean side construction, with constant chloride exposure, it just seems like a bad idea.
Even in Canada with road salt, we use cathodic protection, rebar coatings in bridge decks, galvanized or epoxy. Better than nothing.

"Re-certification" every 40 years, it could be inspections every year and it would change nothing. The HOA can still sit on findings and do nothing.
It frustrates me that engineering is surrounded by non-engineers calling the shots, whether it's sneaking in a penthouse, a construction contractor doing improv to save a few bucks, or a condo board not moving on critical repairs and in 2021 deciding "let's replace the roof" as the priority.

Quote (lucky555)

"Re-certification" every 40 years, it could be inspections every year and it would change nothing. The HOA can still sit on findings and do nothing.

A better inspection regime can include enforcement. Catching the problems earlier makes them less costly (CTS was going past an average of $100k per apartment, which is a big problem for getting the owners to pay), and less urgent (they can take their time, but still have some sort of enforcement deadline). Get the code enforcers to give priority to safety issues instead of whether the sea turtles are upset by the type of lights.

Yes, stuff will probably still slip through the cracks with more frequent inspections, but finding and monitoring the problems is essential to reducing the risk. The FIU structural engineering professor that was talking about this was suggesting different tiers of inspection over time. You could have a quick annual walkaround to just note problems, 5 year basic inspections of the major stuff, 10 year inspections that get into more without being too disruptive, and 25 year inspections that involve tearing stuff out for a proper look. The thing that's certain is that 40 years is much too long for regulatory inspection.

If the HOA is faced with their property value going to zero via some sort of red tag condemnation, as the final step of enforcement, they will do what is needed to stay ahead of that.

Any comments about the Proflex membrane material depicted in this photograph? Below the failed level the ProFlex is on, the edge of another failed level can be seen.

Quote (jrs87)

Any comments about the Proflex membrane material depicted in this photograph?

A quick search suggests they do all sorts of products for different purposes, so difficult to say for certain. That is a fallen floor slab which has remained attached to the elevator shaft shear wall, hinged down on its rebar. It would have been the floor of a bedroom. It may be something quite innocuous like an underlay for flooring material.

I had what could be a great idea. Restaurants have to display a hygiene / safety rating in their window / entrance. Do the same thing for all large buildings (condos, hotels, offices, venues; anywhere that commonly has a large number of people in it); based around maintenance, safety, and code compliance. I doubt I'm the first to think of it, and it basically expands existing red tag unsafe building notices. Importantly, it could cover more than the all or nothing with red unsafe notices, making it clear when a building is gradually deteriorating, before it gets to a critical level. Just don't make it about lights upsetting sea turtles.

Label them clearly, and it will hit them in the pocket if they have a bad rating. Let people lookup the outstanding defects and violations on the town / city website. It could potentially turn the situation fully around and have the residents pressuring the HOA to keep an A rating, so their value is maintained and insurance rates kept low. It even goes beyond monetary value, by preventing people taking advantage of false prestige from a beautiful lobby that disguises a wreck of a building.

Does anyone have the original 1979 blueprints to the tower?

Quote (Mbrooke)

Does anyone have the original 1979 blueprints to the tower?

You'll find the original 1979 plans and various other things here:

https://townofsurfsidefl.gov/departments-services/...

N.B. There are multiple versions of the original plans in the big 1979 PDF, and some are for the North tower.

Since I became aware of this tragedy, last week, I have followed as closely as possible. I have numerous thoughts on the state of the industry that I use to earn a living and take care of my family.

The 40 year recertification requirement is actually more stringent than most jurisdictions. In my home jurisdiction, commercial buildings are provided with a certificate of occupancy upon the completion of construction. At this point, the local building official cedes jurisdiction to the fire chief. The subsequent inspections focus almost exclusively on fire hazards, egress paths, and fire suppression. The structural systems are never evaluated again, unless somebody sees an obvious issue.

ICC publishes the "International Existing Building Code" and the "International Property Maintenance Code". Neither of these codes have been adopted by my home state. By default, once a certificate of occupancy is awarded, there is no oversite by an government body.

The concept of Qualified Immunity for building officials needs to re-evaluated. Typically the Chief Building Official is a registered professional (but this is not a requirement, maybe it should be).

Perhaps the way we have always done things is needs to change. I think, that the public has a vastly inflated view of the capabilities and responsibilities of the building department. In my experience, with a few exceptions, they rarely provide any value in the plan review process, especially when it comes to the structural design. Maybe we need to rethink this process entirely. I have done quite a few projects were the owners insurance carrier required conformance to the design standards of FM Global. Often in these cases, the review is more robust and any comments seem justified by their design standards. Perhaps requiring a 3rd party review would reduce design errors. In addition, these buildings typically get inspected on a routine basis, as the insurer does not want to pay a claim. Maybe the people that would be financially responsible for the collapse would take a greater interest in the building than someone with qualified immunity.

Our engineering boards seem to be very slow and hesitant to act, even in cases where there is ample evidence of violations of the laws and rules. Two cases recently, the hotel collapse in New Orleans and the bridge collapse in Florida standout. The last time I checked, the engineers in both of those case are still practicing and still licensed. I am not suggesting, at this time, that this tragedy is the result of an engineering error or a judgement error by any engineer. Since our industry is self governing, oversite and discipline by the board has to occur when engineers commit a violation.

Hopefully something positive can come out of this tragedy.

Found them, thank you very much Murph 9000! :)


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

Quote (I think, that the public has a vastly inflated view of the capabilities and responsibilities of the building department.)

Agreed.

Im reading alot about the pool. How is that an issue since its not near the building? The corbel at the deck failed, causing the pool deck to collapse, and then leave the building columns un-braced, causing the building to fail?

Another question, will this failure cause you to think more about how you word an inspection report?

I'm curious about the lack of shear walls (isolated and composite) and the impact it may or may not have had on the collapse. If they had closed off the secondary stair with the red walls, would that have prevented the total collapse between Grid H - P, assuming the diaphragm were cut off from the blue shear walls if the initial collapse occurred around Grid H.

Running a few quick numbers on the East-West direction:
Building is 46m wide and 36m above ground = 1656m^2. Say 2.5 kPa basic ULS wind pressure (hurricane)
Base Shear = 1656 x 2.5 x 1.3 = 5400 kN
Base Moment = 2.5 x 1.3 x 46 x 36^2 x 0.5 = 96 900 kNm
So they have two 2.5m long by 250mm (27.5 MPa) shear walls in the EW direction with not much gravity load due to openings either side.
Tens/Comp stress at the ends of shear walls would be running at around 185 MPa
(ie over 6 times the concrete grade) (not taking into account at effective flange action with the long transverse wall)...

Column on Grid I/8 is 305mm x 610mm (incorrectly noted as Type G but actually Type L) with 41.4 MPa concrete grade. Length is around 4.2m at the lobby with a slenderness ratio Le/r of say 1.0*4200 / 0.3*305 = 46 (>25 so deemed slender)
Say design ULS loading of 10 kPa (200mm slab, 1 kPa SDL, 2 kPa LL) with roughly 50m^2 trib area over 12 floors is around 6000 kN.
ULS stress is then running at around 32.2 MPa (78% of f'c).
At that sort of slenderness I'd be expecting a max ULS stress of roughly 30% of f'c.

I might be way off with my imperial to metric conversions...

Saw a article from CNN written by an architect

Link

Surprised that he would comment on structural aspects of the building. Should engineers be speaking up?

@JStructsteel
It may not be an issue at all. Attention is being given to the pool for two reasons.
1 - The most recent pre-collapse photos of the basement garage were from the pool room. We don't know if that level of damage extended to the rest of the basement but we can't rule it out.
2 - Pool chemicals can degrade both concrete and metal, its known that there was standing water in the pool room so it would stand to reason pool water was leaking into the garage. While it would be a small
amount, its possible chemicals worked their way into the columns under the building itself accelerating the damage from salt water that we know was there in 2018.
At this point its all speculative. We may learn tomorrow that 2x4s were being duct taped over cracks which would take the conversation in an entirly new direction (i'm in no way saying this was the case, just using it as an extreme example). So why not discuss the possibility that poor pool maintenance lended itself to the collapse?

I do not know to what extent rebar corrosion may be a significant factor in the collapse, but am somewhat doubtful, unless there are areas where the deterioration is much more than the photos that I have seen to-date, although I did see one photo where the delaminatio was horrendous.
I have seen lots of rebar corrosion and resulting concrete spalling in parking garages here in Ontario, where large amounts of corrosive deicing chemicals are used on winter roads and tracked into parkig structures, including parking structures directly below high rise buildings--yet they did not fall down (except the Algo Mall)


I think all possible causes should be considered at the outset, and then whittled down by careful examinaion and consideration of the evedance, examinanation of drawings and site review reports during construction, possible design and constructin errors, deterioration, foudation problems, etc.

Geotechnical and structural engineer should be involved in the review of the case. Could this be s fundation filuer?
What type of foundation did it have? Was it proprly installed?

I would conider immediately, withou delay, evacuating and tmporarily relocating the people in the buildings similarly designed, and consructed by this developer/contractor/engineer/architect at that time.

What did Einstein say? - "The definition of insanity is doing the same thing repeatedly and epecting a different result".

If there is another buiding of the same design, by the same developer/contrator/construction manager/architect, in similat exposure conditions and similar age, then I woud expect the same result eventually- i.e. collapse.
anout

Some type of monitoring system should be installed as soon as possible without delay in the remaining budings of this design if people are to return to them.

Some of the commentary in the media (TV, etc.) is poor, but some by experienced structural engineers has been good.

I would be interested to know if the slabs were prestressed, or not, and if they were was it with unbonded tendons?


Full disclosure - I waa involved from 1983 to 1997 with preparation of the Canadian Standards Asoociatio(CSA) Stanard S413, Parking Structures which deals substantially with corrosion and how to protect against it. Type and class of concrete, protective systems, drainage, etc.

https://www.cnn.com/us/live-news/miami-florida-bui...

Watch the video under "A nearby condo complex is working to repair similar damage. Here's what it looks like inside."

With all of the talk about the need for more inspections, this building had been scrutinized for several years by a licensed structural engineer and it still fell down. If anyone should know how/why the building collapsed it is them.

What is/was their responsibility in this instance?

What should they have done that they didn’t do? (As it pertains to major defects that require immediate attention.)

Should the municipality be the structural engineering firm that completes the inspections, reports, and recertifications? How large would that staff have to be in a place like Miami Beach?

I've never thought much about this until this happened, but it's bothering me. Coming from a bridge guy, I see a huge disconnect in the near-constant engineering eyes watching over our bridges but the opposite for buildings. Bridges are inspected typically every two years, in some states every year for fracture critical members. For slower-developing problems like scour it might be five years. This is done in a systematic way in a consistent format. Some level of data is public. Problems are prioritized and fixed. The impetus for all of this was the Silver Bridge collapse in 1967 that killed 46 people (and that bridge was just shy of 40 years old I might add).

As we see from this tragedy, the life safety impact of a building structural failure can be as serious or worse than a bridge collapse. Yet the formal scrutiny of these structures ends with a certificate of occupancy at the time they are built until recertification four decades later? The in-between is left to disclosures between buyers and sellers of the properties. How does that protect public safety?

I'm hoping this opens eyes to the need for engineers to evaluate the safety of our entire built environment. We talk a lot about "crumbling infrastructure" but take for granted that buildings are safe indefinitely. Surely that can't continue after this.

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

This is from the preliminary repair drawings showing test probe results in the pool deck area:



I interpret this to mean there was a second layer of patio pavers added to the pool area at some point in time after original construction. Can anyone confirm?

I would imangine that this is because bridges are public and buildings are private. Housing payments are already high and to require building owners in this case an assoication of owners to pay for inspections ever year or two would be difficult. It appears that people in the building have known about some of the issues for at least a few years, but they couldn't come to an agreement on how to fund the repairs. How would you expect someone to react if they were told that they need to come up with a $10,000 special assesment to fix something they aren't familar with? I am guessing most would say they couldn't afford it.

@JStructsteel
The talk about the pool is mainly regarding the "pool deck". Essentially the elevated slab the covers the entire property at ground level and forms the roof of the underground parking garage. At least that's what I'm talking about. The pool itself probably has nothing to do with any of it as it is supported directly by the foundation, other than being a source of corrosion for surrounding areas perhaps.

Thanks. I have seen stories of the pool equipment area and how bad it was deteriorated, and from the plans, it seems its near the pool, not the building. Just trying to figure out why that story is being pushed to the top, perhaps just because its new info and has pictures?

Spartan5, If I condemned every building that had rebar issues or cracks, i would be out of business. Yes, the engineer did say its critical, but no engineer could predict this type of failure at the time of inspection. Who knows what happened even since April?

It would have to be a State wide agency, and then again, who is going to pay for it? $$$ matter, even in a disaster.

Quote (ash060)

Should engineers be speaking up?

I said it in the first Champlain Towers thread, and I'll say it again....yes, emphatically, yes. And we're shooting ourselves in the foot as a profession when we do not. Thankfully some are starting to speak up as I've now seen on CNN, even saw an SE assoc president on local news in Midwest US, and they have found ways to do so without speculation. Or if a speculation-type statement was issued, they've prefaced it as such. I'll spare my first draft rant which got longer than I intended, as I do not wish to hijack this thread. It's good to see engineers starting to share their thoughts now, but I do think we should be among the first out there when such events occur...with careful statements.

The photos of the spalling around the pool equipment from the Miami Herald article linked above are now making the rounds on local and national TV news. I'm skeptical, however, that spalling on the "skimmer" part of the pool shell in an isolated corner of the property would be a factor in the building's collapse. That spalling is most likely caused by 40 years of moisture from the pool itself and not the failed waterproofing on the deck. Furthermore, the deck around the pool and spa is one of the few places where it didn't collapse.

Now, as has been pointed out above, if this spalling was the current state of the structure throughout the entire garage area, then that's something to be concerned about.

The more interesting aspect of the Herald article is the report from this pool maintenance personnel that 36 hours before the collapse, the garage, 21 years later after the last reported sighting, was still having issues with significant standing water at the base of the parking ramp. It is suspicious the location of the water is at ground zero where the deck collapsed and close to where the building collapse started.

Quote (JStructsteel)

"It would have to be a State wide agency, and then again, who is going to pay for it? $$$ matter, even in a disaster."

Another statewide agency with individuals immune from civil liability is not the answer. The main driving factors in these decisions are economic. Remove liability caps from the insurance companies and have the inspections done by people with a lot to lose. Perhaps the building codes could be adopted to provide guidance to engineers on what level of damage is acceptable. Just spit balling, but a statement saying that any damaged element with less than 85% of original capacity must be monitored on some timeframe. Anything less than 75% of original capacity must be replaced immediately. If any element is found to have a 50% reduction in capacity, the entire structure must be vacated until repairs are made.

There is going to be costs associated with any program, but based upon what I see in my day to day work, events like this will continue to happen.

Quote (Zroge)

Huh, the spa was added sometime later. The drawings only show the main pool. I would really like to know when that was done.

The current pool and spa design and layout are in some 1980 revisions of the original plans on pages 204 and 264. It appears when the 13th floor penthouse was shoehorned in, the finalized pool area design was ready.

Quote (OHIOMatt)

I think, that the public has a vastly inflated view of the capabilities and responsibilities of the building department.

I think most building departments have a vastly inflated view of their own capabilities and responsibilities.

One of the most common sense things I have seen regarding the maintenance of this building is a suggestion that instead of 40 year recertification it would be evaluations at something like a 5-year interval (5, 10, 15) with each inspection becoming progressively more in-depth.

You could have the most generous inspection plan for structures and still miss design flaws like the I35W bridge (or hire the De Soto bridge inspector). And, unless someone in a building department is going to take personal responsibility for an aged existing building, giving local building departments more power will ultimately just ensure that turtles can sleep on the beaches at night (do any of you talk to your local building inspectors?). At this point, I'm thinking about the pocket change Morabito got for the inspections, and being thankful that I'm not him. I've seen an entire top layer of rebar rusting and delaminating through a supported floor. Concrete chipping off the corner of columns - no big deal. Condemning a structure is a lose-lose (hidden win if you're right) proposition.

Pin pointing the failure is key (hint - not the D-rings on the roof). Maybe this failure has already been corrected by current building codes? Until we know the problem, we can't fix it. The deal as professionals, is that we hold our profession accountable (ah-hem New Orleans). In return, we should work to hold off the lynch mob who think plaster spalls are a sign of impending collapse.

Quote (spsalso)

Would it be a problem if the rebar arrangement had not accounted for a lack of horizontal support at the midpoint of this "new" column height?

YES Several posts have said so, but, perhaps in technical jargon.

SF Charlie
Eng-Tips.com Forum Policies

StrucDesignPE, I think the big issue is we can require all the inspections we want but someone has to have the authority to make sure the repairs are made. Right now there is literally no one with skin in the game (aka liability) that can force changes. Even us as engineers include statements (for good reason) that attempt to limit our exposure with inspections.

I'm guessing this Morabito firm will be included in litigation. A fair question is should they have done more in 2018? By all accounts they gave the report to the condo board which likely consisted of a bunch of people with no real knowledge of how critical these issues were except for a few sentences in a report. They see the cost to fix those and it's pretty easy to just kick the can down the road.

So when a condo sells in this complex does the seller have an obligation to disclose any correspondence about the repairs recommended in 2018?

Quote (Trenno)

I'm curious about the lack of shear walls (isolated and composite) and the impact it may or may not have had on the collapse. If they had closed off the secondary stair with the red walls, would that have prevented the total collapse between Grid H - P, assuming the diaphragm were cut off from the blue shear walls if the initial collapse occurred around Grid H.

I'm pretty sure the collapse progression was initially halted by the eastern stairwell and increased column density in the N,O,P columns. That section might have remained standing if the stairwell had provided shear walls to resist its westward movement.

Under the general consensus that the failure of the upper levels started with I,K,L,M in row 9.1/10, it's not unreasonable to think that additional stability in that stairwell might have saved apartments in the north side of the collapse, potentially limiting it to the two pool-side stacks between the elevators and parking ramp.

"Remove liability caps from the insurance companies "- let me know what your new infinite-liability auto insurance costs. I'd be curious who is qualified to underwrite it as well.

JSTephen, removing or drastically increasing the liability caps for the insurance carriers would force them to reduce their exposure in other ways. Primarily this could be done by periodic inspections and more stringent design requirements. FM Global takes this approach. We often joke in our office, that if you design to FM Globals standards, they will never have to pay a claim. This is done for manufacturing and warehousing, so why not take a similar approach to buildings with hundreds of occupants?

We must find a different approach to building safety. I have personally found that the building departments are ill equipped to handle any project of greater scale than a house. Look no further than New Orleans. An incomplete set of documents was approved by the building department. Any novice structural engineer and most contractors would have been able to see that, yet the city issued a permit.

As Rabbit12 stated, there's a grey area between engineering recommendation and downstream stakeholder action.

Should Morabito have used stronger, more definitive language regarding concerns over impending structural failure? And if they had, is there anything preventing another engineer (and another, and another) from coming in and offering a second, more owner-palatable opinion to the contrary?

As we sit today, the engineering community can't really mandate another party's activity, nor the timeframe in which the activity is carried out. All they can do is present information as clearly (and educationally) as possible, with due consideration for "strong warning" when conditions warrant, and bring as many relevant stakeholders into the correspondence loop as possible (AHJ included). In the end, though, even if ten engineers opine that immediate repairs are critically important, they have no power to enforce.

I read the Morabito report. Only they can speak to observations made and the manner in which they present their resulting judgments and recommendations in a written summary. I personally didn't get the sense that a time sensitivity of remediation was expressed in the written word, nor was there any language regarding interim temporary measures that might be leveraged as a precautionary step prior to the start of a full repair. Again, though, that's one person's interpretation, and an interpretation made without the benefit of being privy to other supporting conversation and correspondence that accompanied the report.

It's a flawed system, as it relies heavily on the decisions and choices of flawed humans. You just have to hope that all stakeholders behave responsibly.

I think inspections with open and transparent results would be a good start. Then the owners would be strongly incentivized to maintain their own common property to preserve their individual unit property values. Bridge inspections can be boiled down to a 0 to 100% "sufficiency rating". If high-occupancy buildings had a structural inspection say, 15 years after opening and every 5 years following and a standardized inspection score made public, the free market would put a lot of pressure on owners to keep up with routine maintenance before it turns into a $15 million or 150+ fatality problem.

Real estate sites like Zillow or vacation rental sites like VRBO have all kinds of high level "scores": walkability scores, energy efficiency scores, solar energy potential, neighborhood livability, you name it. People love to rank, sort, and eliminate.

So, how hard and expensive would it be - given the stakes - to develop a "Structure and Systems Health Score" that is standardized and disclosed to potential buyers in a market. The issue of cost neutralizes quickly when comparable units in the building next door are selling for $100k more due to a 20 point better score.

Buildings will deteriorate eventually. We've all taken thermodynamics here; entropy marches on whether we acknowledge it or not. For most buildings, this means that someday the land will be worth more than the building, which will be torn down to build something new. In this case, the building didn't wait for the HOA to decide its fate. The end result was rare but tragic.

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

In my opinion, corrosion was not a significant cause of collapse.
Also lack of floor slope was not a significant cause of collapse.
If water containing corrosive chlorides runs over the floor over many years, and the floor has no membrane protection, the concrete will absorb the chlorides. Guaranteed, even if loped.

Among worst rebar corrosion I ever saw was top bars in steeply slope truck ramp.

I have seen very bad corrosion and spalling, including on bridges, but no collapse, and no indication of structural distress.
This does not mean it is not serious; it should always be reapired a quickly as possible. I always add "withoutd delay". Owner must not wait till management includes it in some far off budget.

Retired P.Eng.
Ontario, Canada

Twenty-four Miami apartment buildings, including two county-owned structures, listed unsafe after audit
https://news.yahoo.com/twenty-four-miami-apartment...

To be clear, ajk1, corrosion of the rebar is structural distress.

Your top bar deterioration example may have been in a location of low negative moment or you were observing temperature steel. Rebar corrosion of flexural steel and/or shear steel will result in a reduced cross sectional area of steel, the farther it deteriorates the more likely the remaining steel will yield and finally break. Like many things, rebar corrosion largely depends on which bars are corroding, how fast and where. For example, if the shear reinforcement on the transfer beam on the plan-east side of the building were corroding --- that could certainly lead to structural failure.

Thank you, SF Charlie.


spsalso

I heard that the collapse started with the pool deck. Some woman, in the condo, was on the phone with her husband (not in the condo) and stated that a sink hole opened up below the pool as it had sank down. The call was then cut off.

Quote (ajk1)

In my opinion, corrosion was not a significant cause of collapse.
Also lack of floor slope was not a significant cause of collapse.
If water containing corrosive chlorides runs over the floor over many years, and the floor has no membrane protection, the concrete will absorb the chlorides. Guaranteed, even if loped.

Among worst rebar corrosion I ever saw was top bars in steeply slope truck ramp.

I have seen very bad corrosion and spalling, including on bridges, but no collapse, and no indication of structural distress.
This does not mean it is not serious; it should always be reapired a quickly as possible. I always add "withoutd delay". Owner must not wait till management includes it in some far off budget.

Retired P.Eng.
Ontario, Canada

+1

I repair deteriorated concrete structures for a living (also in Ontario). I walk into underground parking garages on a daily basis (with no immediate plans for repair) that indicate significantly more distress than what the pictures we have been seeing seem to show. Hell, go take a drive under the Gardiner expressway in Toronto to see one above you! Some of those bents, my oh my.

I'm not saying that is "okay" but I when one has seen 100s if not 1000s of deteriorated concrete structures, all of which stand up even when you look at them and go "...how??" I find it very hard to attribute this failure predominantly due to deterioration (surely played a part but I cannot fathom a large one). Caveat: based on the pictures we have seen. Perhaps something was so deteriorated that it was the prime culprit, but we havent seen it yet.

The fact that this thing was constantly flooded is much more suspect to me. How can an UPG be flooded all of the time and you not have soil issues? I would be looking there.

Engineers carry all the responsibility and yet have none of the authority.
Expecting us to speak up and be whistleblowers is proven to not work, and what a terrible process that is.
People need a job and paycheque, they have a family and bills to pay. Whistleblowing ends that potentially your career, and can you personally finance that lawsuit against you now?

I think after the design and construction phases, these "inspectors" are a plague. The people aren't fully qualified, they seem to be easily bought, and play into politics.
Afterwards, there is no mandate to get the repairs done or follow up to see if they were. I can understand a multimillion dollar special assessment taking time to collect funds but it seems to take many years to begin to get repair work moving forward.

"Miami-Dade inspectors have more than 1,000 active cases before the board for overdue recertifications"
Two apartments of 24 on the latest 24 Enforcement Recertification Cases are dated 2008, what they are waiting for?

ajk1:
We are not saying that rebar corrosion meant that there was loss of cross-section of the rebar; what we are saying is that the expanding rust pushed away the concrete that then fell away. That concrete was needed in the cross-section of the column. You say, "although I did see one photo where the delaminatio[n] was horrendous". Isn't that enough to evacuate the building?

"Some type of monitoring system should be installed as soon as possible without delay in the remaining budings of this design if people are to return to them." I think you are placing too much faith in a high tech solution. What are you going to monitor? The lateral deflection of a column? EVERY column? Which ones? Let's say the monitor shows 1/2" movement. Do you evacuate the building immediately? Is there enough time for everyone to get out before the column and the building collapse?

Spartan5:
The professional engineer (his stamp does not indicate his specialty; may have been 'grandfathered' in the 60s; he looks to be almost 80 years old) may have recognized that there was a problem. He gave the board his recommendations. I'm sure he expected that they would repair within a year or two. My only complaint with his report is that he did not recommend temporary shoring of the columns and slabs. That could have been done immediately, for less than $100,000, and we would not be studying this building because it would not have collapsed.

2bradw1128:
It took many failures for your branch of the industry to recognize the need for the inspections you describe.

StrucDesignPE:
Right -- the inspections could probably start at 15 years, and then be repeated every 5 years. Each inspection should have the power to call for a more in-depth inspection if certain categories of problems are noted. The inspections should have the proviso that the building's occupancy permit will be rescinded unless there is a contract in place for the repairs or mitigation within one year of the date of the report.

"So when a condo sells in this complex does the seller have an obligation to disclose any correspondence about the repairs recommended in 2018?"
I cannot see any reason why a buyer would NOT have an obligation to disclose, but one woman bought her condo in December 2020 with no info on the report or the problems. Disgraceful.

OHIOMatt:
"We must find a different approach to building safety. I have personally found that the building departments are ill equipped to handle any project of greater scale than a house. Look no further than New Orleans....yet the city issued a permit."
The city of New Orleans does not train its inspectors to inspect high-rise construction. There just aren't enough projects to make that feasible. Inspection is intended to protect the general public from poor design or bad contractors. Large projects are expected to have on hand building inspectors and experts who can insure the construction is done to specs.

Quote (JStructuralsteel)

Spartan5, If I condemned every building that had rebar issues or cracks, i would be out of business. Yes, the engineer did say its critical, but no engineer could predict this type of failure at the time of inspection. Who knows what happened even since April?

It would have to be a State wide agency, and then again, who is going to pay for it? $$$ matter, even in a disaster.

Your first statement illustrates the point I was drawing at to some extent.

“but no engineer could predict this type of failure at the time of inspection”

Then what is it a state agency solves?

If the inspection wasn’t sufficient, is something even more comprehensive required?

Quote (MINIMUM INSPECTION PROCEDURAL GUIDELINES FOR BUILDING STRUCTURAL RECERTIFICATION)

Cast in place reinforced concrete slabs and/or beams and joists may often show problem due to corroding rebars resulting from cracks or merely inadequate protecting cover of concrete. Patching procedures will usually suffice where such damage has not been extensive. Where corrosion and spalling has been extensive in structurally critical areas, competent analysis with respect to remaining structural capacity, relative to actual supported loads, will be necessary. Type and extent or repair will be dependent upon the results of such investigation.

http://www.miamidade.gov/permits/library/structura...

Quote (2018 report)

Abundant cracking and spalling of varying degrees was observed in the concrete columns, beams, and walls. Several sizable spalls were noted in both the topside of the entrance drive ramp and underside of the poot/entrance drive/planter slabs, which included instances with exposed, deteriorating rebar. Though some of this damage is minor, most of the concrete deterioration needs to be repaired in a timely fashion. All cracking and spalling located in the parking garage shall be repaired in accordance with the recommendations of ICRt.

That was in 2018. In June of 2020 the same consultant was hired to prepare and had been working on a "40-year Building and Repair and Restoration" plan. Would that not require additional extensive inspection and analysis to prepare a comprehensive design?

Quote (NOLAscience (Structural)29 Jun 21 19:39)

"So when a condo sells in this complex does the seller have an obligation to disclose any correspondence about the repairs recommended in 2018?"

(maybe I'm quoting a quote?)
In California, The Realtor is legally required to disclose this. Also, if there is a lending bank, they require lots of documentation from the condo association about pending lawsuits and deferred maintenance. Realtors do get sued for failing to disclose (almost anything) here.

SF Charlie
Eng-Tips.com Forum Policies

Quote (NOLAscience)

The professional engineer (his stamp does not indicate his specialty; may have been 'grandfathered' in the 60s; he looks to be almost 80 years old) may have recognized that there was a problem. He gave the board his recommendations. I'm sure he expected that they would repair within a year or two. My only complaint with his report is that he did not recommend temporary shoring of the columns and slabs. That could have been done immediately, for less than $100,000, and we would not be studying this building because it would not have collapsed.

The same consultant was retained in June of 2020 to complete the design of all of the repairs. They produced this 84 sheet set of drawings to that effect. Is it silly to think there would have been additional inspection and analysis that went into all of that? I can’t believe they completed their entire design on the basis of that brief 2018 report.

Assuming the pool deck did collapse first, as seems apparent due to eye witness reports, the collapse force would have been not only vertical, but it would have had a horizontal component. Enough to pull a 12 storey building over, one with not much shear wall capacity? Perhaps. Brings up the age old question of structural separation. Should the pool deck have been a separate structure? Probably.

Hokie66
I asked that above. If it failed, and collapsed leaving the lowest column un-braced, then I can see that. Progressive collapse. There were some reports of cracks opening up hours before the collapse.

I see a lawsuit saying the additional roof weight for the roof work caused it. I would assume the building (or that column line) was not at 100% live load and DL. again, not sure on the deterioration at that location. But the lawyers know.

Quote (In my opinion, corrosion was not a significant cause of collapse.
Also lack of floor slope was not a significant cause of collapse.)

I suspect stongly that it and the lack of maintenance was at this point... I'm still waiting for other info, though.

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

-Dik

The pool didn't collapse, so this discussion about the pool is not relevant to the building collapse.

The roof work needs to be reviewed more thoroughly, it was occurring directly over where the collapse started. A few questions:
- Did the roof workers use any heavy equipment requiring shoring?
- Was the standing water near Space #78 there because the roof workers had taken the roof waterproofing off to replace it and water infiltrated the building (adding weight)?
- Did they use a tarp that may have collected water increasing the weight at the roof level and subsequent column loading?
- Were they drilling into the columns to install roof anchors, could this vibration have caused a failure at a lower level in an already compromised column?
- Did the bootleg penthouse addition contribute by overloading the columns?

-W

Typical Floor Plan (Floors 9-12 shown, 1-8 similar):


Surveillance Video Capture:


Garage Plan:


Roof/Penthouse Plan:


View of Roof After Collapse:

Sorry about the paywall. I can't find another source that's not. I think the headline is misleading in that I don't believe he had "signed off" on anything yet, just made comments at a meeting. Still, I thought this would be of interest to the group:

Surfside Official Who Signed Off on Collapsed Condo’s Condition Is Placed on Leave

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

Quote (hokie66)

Enough to pull a 12 storey building over, one with not much shear wall capacity?

Don't forget the already compromised columns. The I,K,L,M columns in row 9.1/10 were sitting in standing water where they met the basement slab, and under planters with a drainage problem at patio level. You might have both column and slab damage / degradation at both ends of those basement columns. Patio slab fails in the middle of the outdoors, pulls on the top, kicks the bottom; or pulls on the top and hangs on until that fails. It only has to pull and kick those columns a little bit off vertical, to setup the next step of the progressive collapse. It doesn't have to instantly pull those columns out, and the progression may have paused for a short while there. Just a little damage to 3 or 4 adjacent columns that already had some significant rebar corrosion and spalling.

The video from inside apartment 711 has the building severely compromised for something like 15 seconds before it falls, the woman in 611 saw walls cracking with sufficient time to escape, and Gabe saw the patio slab drop from apartment 111 with enough delay to escape.

warrenslo - the collapsed pool deck:

Quote (warrenslo)

The pool didn't collapse, so this discussion about the pool is not relevant to the building collapse.

I disagree, and it's down to language use. People are saying "pool" and "pool slab" when they mean the patio / plaza slab between the pool and the building. They mentally consider the "pool" to include the upper slab surrounding it. To them, the slab collapsing is (part of) the pool collapsing. Remember that their description is colored by adrenalin, panic, and trauma; also they are laypeople who don't describe things accurately.

A large portion of the pool/amenity deck underwent some measure of collapse, and according to a couple different eyewitnesses this preceded the superstructure collapse.

I would be surprised if the investigation ends up showing that an issue on the roof ended being the primary, driving factor in this collapse. A contributing issue? Sure. Perhaps even the straw that broke the camel's back. But structure at the amenity level is what to me warrants a tremendous amount of initial attention. A bit of extra load on the roof or not, the amenity level presents as if it were a bit of a ticking time bomb.

Quote (Spartan5 :)

warrenslo - the collapsed pool deck:

The pool equipment room where the pool contractor took the photos (highlighted in yellow below) did not collapse, it is still standing today.

We do not know if the pool deck collapsed first or if the building collapsing on it brought it down (more likely the latter in my opinion based on the damage pattern and 111's testimony.)

111 seems to have escaped via the pool deck as he said he went outside to go investigate and he had direct access - if the pool deck had collapsed 1-story into the basement at this time then this wouldn't be possible.

From 412's vantage point she wouldn't have seen the first collapse, her guest bedroom is in the way, only floors 9-12 in the x12 stack have a balcony viewing the initial collapse. Its likely she was seeing pool deck dropping due to the initial collapsed portion of building falling on it. This is evident by her phone cutting out seconds (not minutes) after which is when the second portion of the main collapse occured.



-W

The initial failure was under Unit 111. Gabriel Nir, Unit 111's testimony:

When part of a beachfront condominium building collapsed in Surfside, Gabriel Nir and his family escaped what would have been certain death.
"The first collapse happened, and me and my mom and sister went out," Nir told NBC 6 just hours after Champlain Towers South partially collapsed Thursday morning. "We see the collapse happening on the poolside and I saw a bunch of cars going inside the car garage, so I panicked, my mom panicked, everyone panicked."
Nir's first-floor apartment, unit #111, was above a planter and underground garage entrance ramp that engineers years earlier singled out as the most serious flaw in the building.
Proximity to that apparent failure point likely saved his and others’ lives.
"It was at that moment I saw the ground shaking. I felt something was happening," Nir said. "At that time, I had to run out. I told my mom, my sister, 'everyone, start running,' and so that happened. Everything started, out of nowhere, like cement, dust, sand coming out."
The first signs of collapse minutes later, appearing right at this unit. Nir estimates perhaps two minutes after he reacted to the thunderclap of a beam or column likely falling beneath his unit.
While that may sound like a delayed collapse to a layman, engineer Jason Borden says it’s an instant in engineering terms.
"It sounded like an immediate or spontaneous failure, which is unusual in a modern structure which is built with ductility, durability and redundancy in mind," Borden said. "So the fact that it failed as abruptly, as immediately as it did leads us to believe there had to be more than one thing going on there."
The time for warning and escape are built into designs, but there wasn’t much warning here.
"A freak accident, if you will, once in a lifetime for sure. I think possibly it was a collective of things, deterioration in the structure," said Yaniv Levi of Coast to Coast General Contractors. "It's very unfortunate and this is the first time I’ve ever seen this in my industry, ever."

Quote (warrenslo)

111 seems to have escaped via the pool deck as he said he went outside to go investigate and he had direct access - if the pool deck had collapsed 1-story into the basement at this time then this wouldn't be possible.

Quote (111 who witnessed the progressive collapse of the pool deck)

”The first collapse happened, and me and my mom and sister went out," Nir told NBC 6 just hours after Champlain Towers South partially collapsed Thursday morning. "We see the collapse happening on the poolside and I saw a bunch of cars going inside the car garage, so I panicked, my mom panicked, everyone panicked."

“We see the collapse happening on the poolside and I saw a bunch of cars going inside the car garage…” seems pretty cut and dry to me. When they escaped, the failing deck had yet cut off their escape route. The failure then progressed towards the building and unit 111 until it compromised the critical columns holding the bulk of the building up.

If I’m not mistaken, there was a 911 call about a collapse in the garage with emergency units already in route when the whole building came down several minutes later.

Nir's statement is not "testimony".

It's his recollection, and perhaps not worded clearly.


spsalso

Should an entire building collapse if just one (1) column fails, either by corrosion of cross section, vehicle impact, subsidence, etc.?? This is of course a rhetorical question, because the answer should be no.

So the next question is, Is this building special in that it may have taken just one column failure to bring down a building? Is there one critical column, or could it have been any?

If one column failure is not enough to cause building collapse then how many columns must fail to bring down a building of this type? Two? Three? Or are we back to this building being deficient in ways other buildings are not? I like the Jenga analogy someone else mentioned earlier, and the complete lack of ductility.

And even if all three exterior columns (I-K-L 10) failed, should a building of this type be able to maintain its overall integrity, or was complete collapse inevitable?

Of course all this assumes column failure is the culprit.

Quote (warrenslo)

From 412's vantage point she wouldn't have seen the first collapse, her guest bedroom is in the way, only floors 9-12 in the x12 stack have a balcony viewing the initial collapse.

412 had a wrap around balcony that directly overlooked the pool. Same view as 111, only higher.

warrenslo is advocating that the first collapse was under Nir's apartment. If so, Stratton would indeed have had trouble seeing it.

But it appears what she DID see was the collapse (or the aftermath thereof) of the pool deck, while still standing in her uncollapsed apartment.


spsalso

I thought the Nir family from apartment 111 escaped though the apartment door by going down hallway into the part that didn't collapse.

It seems pretty certain that the collapse occurred in the pool deck and garage first. Before progressing towards and into the columns supporting the building.

Another account from the mother of Gabe Nir, both of whom were in unit 111. She states that she heard loud noises like “construction knocks” loud enough to warrant making a noise complaint, starting at 12:30 am. It was while she was in the lobby talking to the security guard that she saw the ground level of the parking garage collapse. Which she reported to the security guard. That would explain the first call to 911. She ran back, collected her family, and they all ran to the street, moments before the whole thing came down.

Quote (COLlive)

She returned to her home on Collins Avenue at around 12:30 AM. “I was sitting in the office, going through emails and the like, and I started hearing noises,” she told the COL news website.

Nir described the noises as sounding like “construction knocks” and was disturbed that they were being made at such a late hour, with her son and daughter fast asleep in nearby rooms.

“I thought someone had decided to renovate their apartment in the middle of the night,” she said. “At first, I ignored it. But a few minutes later I became upset about it and left the apartment.”

Nir says she went to the lobby of the building where she met the security guard sitting at the entrance. She reported about the noise and asked him to call the police to make a complaint.

What kind of failure are we looking at where the deck of the garage and pool has sheared more or less cleanly away from the columns?

“As I was standing in the lobby, I saw the parking lot of the building collapsing, like an abyss that has opened up beneath it,” she recalled. “I was in shock. My thought was that these (noises) are not renovations. This is an earthquake!”

She once again turned to the security guard and ask to call the police, this time reporting an earthquake. “There was a very loud noise,” she told him.

Nir then quickly returned to her condo and woke her 15-year-old and 25-year-old children (her husband and other children were out of town). She urged them to leave the house as fast as they could.

“We left the building Within a minute and started running down the street, as far as we could,” she said.

“I heard a huge noise behind me, but I didn’t want to turn around,” she added. “A huge cloud of dust flooded the space. I thought the end of the world had come.”

Ms. Nir was in the lobby when she saw the parking deck collapse. The lobby has a view of same, and photos show at least a part of that deck collapsed (and, of course, the pool deck).

For the timeline, the time of the 911 call is known.

I wonder if the pool deck had already collapsed. I think it would have made a lot more noise than she heard, so probably not. I wonder what she heard earlier, when she was in her apartment. And it took so long, too: "At first, I ignored it. But a few minutes later I became upset about it..."

Uh, wow.


spsalso

I am also of the opinion that the collapse occurred in the pool deck and garage first, then progressed toward the building removing lateral support from the column and/or pulling them over. Whatever the final explanation ends up being, building inspection programs should explicitly consider potential failure modes (PFMs) the way we do with dams. This starts with identifying the possible PFMs during the design process and through periodic review. If PFMs cannot be engineered away in design or subsequent retrofitting, they need to inform the inspection process. Knowing the PFMs and fully understanding how they would play out and the signs they might be occurring provides a framework for action. Action isn't always repairs. It could also be more frequent monitoring or shoring. The "exterior structural slab pulls down building" PFM seems like it could apply to a lot of buildings with exterior plazas and underground parking.

I just found something interesting:
Column I-8 appears to be mislabeled as a column type G on the structural framing plan, it appears it was supposed to be a column type L.
It is clearly longer and skinnier than the remaining G columns in both the architectural and structural drawings.
The roof replacement (Roof #2) is directly above this column.

I think we're all having a little trouble connecting the collapse of the pool deck to failure of the building columns. There must have been some sort of horizontal propagation of slab failure, leading to punching shear failure at the building columns due to unbalanced moments. This then doubles the unbraced length, leading failure of the column in compression.

Not the traditional form of progressive collapse, but plausible.

I do wonder how this building would have faired in a major hurricane.

Sara Nir's interview, they ran out of the apartment with construction noises, there was dust coming at them in the hallway. She was talking to security in the lobby fronting Collins. The garage collapsed with the first large boom (her, her son and her daughter were together at this point) she saw this from the lobby (you cannot see the first part of the collapse from this vantage point.) Then the second boom happened as they were running across Collins. This tells me the garage collapsed with the first main collapse which they would not have seen from the lobby.

Link (Go to 14:00.)

Could it be from all the corrosion to the rebar that the total structure was at the point of collapse?

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)

On S1 (pile cap plan) it is labeled "L"

Warrenslo:
I took her interview as she was in the southern portion of the lobby when the first major event occurred which would allow her to see the cars falling (she said she saw cars getting swallowed up in another interview) in the guest parking lot just outside the lobby; the guest parking area is adjacent to the pool deck separated by a gate and planter/fence. To me it sounds like the pool deck/guest parking area collapsed first then she went and got her kids and got them out through the front lobby. When they got across the street the building went down.

My bet is this is where it started ('cars sinking into basement'). Punching failure and progressive collapse towards main tower and overloading columns I10 & K10. Load transferred on the demising walls on grid K (cracks seen rapidly opening in wall by resident on 6th floor), she got out in time. I8 or K8 (or thereabouts) then failed.

w-streng:
That column with the parking spots 72/73 has intrigued me since I saw it. I’m wondering if one can infer what side failed first based on the left side having the angled slab outside while the right is angled within the column. Also looks like a bit of discoloration of concrete on the side that protrudes.

Quote (bradw1128 (Civil/Environmental)29 Jun 21 20:56)

Sorry about the paywall.

... found this on NPR ...
Official Who Said Champlain Towers Was Sound Is On A Leave Of Absence
Hope this helps ...

SF Charlie
Eng-Tips.com Forum Policies

Every spot in that parking area was occupied. Any better images of the load on that pickup?

This would have been within view of Gabe Nir while she was in the lobby having security call 911.

This fits her account of the "parking lot of the building collapsing, like an abyss that has opened up beneath it,”. She wouldn't have referred to the patio as a parking lot.

I have read 90% posts on these threads and have several observations

1.) The drawings detail 3/4" cover on the slab bottom bars.
2.) I am an engineer for a demo company and our workers spend weeks knocking concrete off rebar so the clean rebar can be sold for scrap,
3.) For the slab bottom rebars to unzip clean from the still standing slabs means either the concrete was mush or there was little cover or the bars were already corroded and popping the concrete.
4.) The collapse of the pool deck considering the main building did not fall on it means the concrete and or rebar deterioration was so bad that not even 1 level at night with no live load could be supported.
5.) Another poster explained that the drapping of this slab during failure would cause tension on the adjacent building and may have caused an outer building column at a planter to fail. I will also add that the pool deck slab that failed may have been a brace which was needed to resist lateral earth and water pressure on the far side of the building.
6.) A 11 foot unbalanced earth pressure would exert about 1k/ft at the top of foundation wall. This may have rolled the columns.

Quote (warrenslo)

Sara Nir's interview, they ran out of the apartment with construction noises, there was dust coming at them in the hallway. She was talking to security in the lobby fronting Collins. The garage collapsed with the first large boom (her, her son and her daughter were together at this point) she saw this from the lobby (you cannot see the first part of the collapse from this vantage point.) Then the second boom happened as they were running across Collins. This tells me the garage collapsed with the first main collapse which they would not have seen from the lobby.

Link (Go to 14:00.)

I appreciate you sharing the link. But your transcription/interpretation leaves a lot to be desired.

She describes hearing progressively load knocking sounds around 1:10 am before a very loud “smash/collapse” noise. (15:00)

She goes to report this to the security guard because it is too late at night for such noises. (15:20)

She asks him if he hears the noises, he says he does. She asks what he’s going to do about it when she hears a very loud “big boom” noise so she runs to see where the noise is going from and she sees “all the garage is collapse.” (16:00)

So she runs back to apartment to get her family, finds them standing next the door “at entrance the her apartment.” (16:14)

She yells at the security guard to call the police as she collects her family and start to flee. (16:43)

As they approach the exit of the building, they yell at security again to call the police. Security says he does not know address. And asks them to write it for him. So her son stops and writes the address for security before exiting building. (17:00)

They flee, getting all the way across Collins before the before the big boom and her first mention of “white clouds of smoke” and not being able to see anything. (17:20).

The daughter mentions hearing “construction noises” while showering and looking out of the apartment to see “white particles” (18:54)

In your telling of this event you want us to believe that she viewed the collapse of the garage concurrent with the total destruction of 1/3 of the building. And then in 8 seconds, 1. collect her family from some portion that didn’t collapse.
2. run to the security guard, having her son stop to write down the address of the building.
3. exit the building and get all the way across Collins St. (I’m not even going to waste time measuring that.)

In 8 seconds. All of that? No.

https://vm.tiktok.com/ZMdasA62E/

This is interesting. Video of deck failure visible through the north parking entrance. All prior to the full on building collapse.

If the building was 120 feet tall a 30 psf wind would exert about 3,6 kips per foot shear. I doubt there were enough piles to take that and the original designer used the 1st floor diaphragm to transfer passive soil resistance from the foundation walls. Once the pool deck slab diaphragm failed there was unbalanced earth pressure on the remaining building.

Quote:

https://vm.tiktok.com/ZMdasA62E/

This is interesting. Video of deck failure visible through the north parking entrance. All prior to the full on building collapse.

Are we sure that shows the collapse of anything and not just a view down the ramp into the parking garage?

Quote (Mark R)

Are we sure that shows the collapse of anything and not just a view down the ramp into the parking garage?

Appears to be debris on the ground and a water pipe broken. Also helps explain the water in the garage.

Hi long time lurker here.

Just wanting to chime in.

Since the very beginning of the thread, the most telling imagary was the punching shear failure of the pool deck, and specifically IMO how it extended all the way into the small guest parking area under the uncollapsed section..

secondly, how perfectly the slab punched through, leaving so little damage, or remaining slab tied to the coluums. Not even much rebar on show. No drop panels in sight either.

So no matter where in this area the failure initiated first, the fact is a single column or joint failure somewhere either beneath the pool deck or the guest carpark has been able to rapidly spread across the whole area and someway under the collapsed section of the building. with punching shear failures at every column on the patio deck by the looks. That's surely got to be a clue that the slab-column joint's are a universal issue

and just as I type this, i noticed Latest tiktok video and eyewitness accounts confirm without a doubt this was the sequence of events. Looks like partial slab failure into the carpark under collapsed section.. Debris is visable inline with the first column after the ramp (M8 or L8?)

I'm an Architect involved in the design of a number of fairly complex buildings.
I'm of the opinion This building collapsed for at least three reasons
Beyond this: I've worked with some seriously great PE's and some seriously terrible PE's
What I find truly amazing in this thread are the posts in defense of a profession instead of finding the problem.
The failure of this building is an engineering problem - pure and simple.
I suggest you cats get your house in order
This will forever change the construction industry.

In the $15M building repair and restoration, I don't see a lot of dollars going to structural repairs. Tree plan pg. 71 mentions Garage elevation -0.28' is that correct? I wondered how low can you go to keep the building's height within restrictions, or maybe low enough to add on a penthouse.

If the pool deck and the parking area outside the lobby were the first failure, which seems very likely, why did they fail?

We're talking about a "diaphragm" held up by an assortment of posts. I don't see much of a load on those joints. WHY would a big slab of concrete just drop?

Another interesting question is what was making the sounds that irritated Ms. Nir for several minutes? It appears nothing BAD had happened yet.


spsalso

I see JimmyP80 was entering a very similar viewpoint while I was writing mine.

@SocklessJ: A portion of pool deck/upper parking that is collapsing due to punch-through of its supporting column(s) could easily give a firm yank to to any remaining supports, potentially destabilizing them and allowing the collapse to spread progressively. The pool deck slab terminates at the columns on the boundary with the collapsed portion of the building with a 2'6" step up to the interior floor slab (see the posting by @dold in the first thread). Thus it has the potential to provide a force at a location where the column is unrestrained by the interior floor slab.

As the span of the deck gets wider because it has lost support during the progressive collapse, the slab starts behaving less like a beam and more like a heavy rope (because it is relatively slender and significantly more compliant in bending with the longer span). The slab will have significant inertia as it falls, and if it is caught by more distant supports (rather than the ground/cars/etc. underneath), it will transmit (depending on the condition of its originally-rigid joint to the supporting column) either a huge bending moment F*d, a huge tensile force F/sin(theta) (if the bottom side of the slab-column joint fails in compression before the rebar fails in tension), or both. Either way it could do significant damage to those columns or trigger buckling.

A few more shear walls would have made this structure significantly more resilient.

In aerostructures we have this concept of "widespread fatigue damage" where widely distributed damage smaller than the nominal critical flaw can nevertheless cause catastrophic failure. Perhaps what we are seeing here is a similar concept but applied in reinforced concrete where widespread corrosion and spallation allows damage to propagate in ways it wouldn't in a new structure.

Mark, you can see the concrete debris on the ground. The water main break resulting from this collapse explains the water seen in the Miami-Dade video.

The person who filmed this was staying in the hotel next door. She posted this 5 days ago. Her video history checks out. https://www.tiktok.com/@adrianitacastillero

There was another guest interviewed at this hotel https://www.youtube.com/watch?v=BvkRmtmB-Fw
This seems to be a different party but same view. Both shouted at the 8777 tenants to get down.

spinspecdrt noted on the previous thread @ 27 Jun 21 02:59,
"I agree with columns on 9.1 line. Particularly @ I and K line. Both are exposed to planter box at lobby level."

Are there any recent photos of this column in the planter? Or that column in the parking garage?

Where did the pool contractor make his comments about the standing water in Parking Space 78? I would like to hear the exact wording.

The Sara Nir (unit 111) interview on Anderson Cooper. go to 14:00 A progression of deck slab collapses is becoming clearer now. Question is where it began.

https://omny.fm/shows/anderson-cooper-360/12-dead-...

Quote (spsalso)

Another interesting question is what was making the sounds that irritated Ms. Nir for several minutes? It appears nothing BAD had happened yet.

Slow (relative) progressive failure of deck/slab working it’s way towards 111?

Quote (The failure of this building is an engineering problem - pure and simple.)

Could be... that, however, might be an oversimplification... could be caused by a faulty design, could be caused by not recognising corrosion of reinforcing steel... Would a clever Architect have noticed that? Might be a negligent/criminal lack of maintenance and repair... maintenance and repair not undertaken because the AHJ may have said that there was no problem... could be the fault of the authorities not following up with statutory requirements... Could be something else.

dunno enough yet... jury's still out...

Your architect 'over simplification' does not further this discussion. The dialogue here simply tries to come to a reasonable conclusion based on the information on hand at the time... We all know that something 'bad' happened, and steps should be taken to prevent this in future... just don't know what these steps are at this time...



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

-Dik

Quote (NOLAscience)

Where did the pool contractor make his comments about the standing water in Parking Space 78? I would like to hear the exact wording.

It’s paraphrased, here:

Quote (Miami Herald)

The deepest puddle of standing water, according to the contractor, was located around parking spot 78 — an area that building plans show is located directly under the pool deck where in a 2018 inspection report, engineer Frank Morabito had flagged a “major error” in the original design that was allowing water intrusion and causing serious damage to the structural concrete slabs below.

He did not photograph that standing water because he was there to examine the pool and what was underneath it.

It looks like the pool deck and guest parking area failed first.

WHY?

I see really minimal loads on those column joints. Weight from some concrete and maybe a car (but not on the pool deck). WHY?

I am looking at, in photos, the rebar at the top of the columns. I am not impressed. Imagine if there had been some horizontal pieces 12' long running through that joint. Would it then have failed?

I am reminded of the Nimitz freeway collapse in the Loma Prieta earthquake. I saw what I took to be a shocking lack of overlap in re-bar in the joints between the columns and the horizontal. Hey, guess what? It pancaked. Surprise!


spsalso

Quote (I don't see a lot of dollars going to structural repairs.)

Having been involved in a bit of repair work... I'm surprised the structural repair is so low. From the condition, I would have thought it would have been several times that. I noted earlier in my posting of June 28 that the repair cover and concrete strength were inadequate for this type of work... and questioned the engineers credentials...

Quote (It appears nothing BAD had happened yet.)

may have just been the precursor...

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

-Dik

Quote (JimmyP80)

Debris is visable inline with the first column after the ramp (M8 or L8?)

The lower end of the ramp is at M8–L8. The full height wall on the left of the ramp is the eastern stairwell shear wall. The column visible beyond the ramp is M9.1 / M10 (same column, but some pages don't show the 9.1 label). That is the exterior column row on the far side of the building.

The Nir family saw the southern edge of the patio/parking/plaza/pool slab fall in advance of the building. This video shows that it had failed all the way across to the 9,1/10 columns and southern wall of the north wing of the building. Then a pause, at least 15 seconds, but possibly several minutes, before those columns failed and brought that section of the building down.

If that pickup truck is heavily loaded, it's potentially a smoking gun, starting the collapse at I14.1. That's total speculation, but there's quite significant load from the vehicles parked around the I columns at rows 12.1,14,14.1 (the three columns under the eastern wall of the surviving southern wing of the building). I wonder if any vehicles associated with the construction work have been using that area? The entrance wouldn't let you get a big construction truck in, but you could certainly get some vehicles that are much heavier than cars in there.

Quote (spsalso)

No, there are three forces in a column, slenderness, punching, and axial. In a moment frame, you also have a fourth load: lateral. Moment frames in concrete are difficult to pull off in a seismic zone due to lack of ductility (or deformation without failure.)

The pool deck collapse relies on a theory that the pool deck collapsed and the columns adjacent were exposed and failed, they fail to recognize the pool slab stepped 2-4 feet at these columns and the slabs were not continuous.

The tick tock video clearly shows something over the garage ramp.

Dust from above in Unit 711 would not have been caused by a pool slab collapse - the short-sightedness of the posters here re: pool deck is concerning. I'm an architect with extensive structural experience on many $100+ million jobs. Obviously, the slabs were thin and the floor slabs would be PT today, but the podium slab most likely wouldn't be and at that thickness was clearly not overloaded. The damage to the columns that held on the existing building clearly shows the pool deck collapsed due to the main collapse due to the angled concrete on the south side.

There was a post above about the podium slab having additional pavers, but the photos show tiles, so I'm not sure what this is about.

There was clear deflection in unit 1010 prior to collapse, the mislabeled column I found (see post above) is between the coat closet and laundry in the photos below - this deflection is more than normal in concrete (in steel is this is more normal in a long span.)

The lobby where she stood watching the cars fall looks like this and she was at approximately the red X. The hallway in the rear goes to her unit, it is likely she saw her daughter there, it does not sound like she ran back into her unit. She could not see the first collapse from this vantage point at all!

Quote (the pool slab stepped 2-4 feet at these columns and the slabs were not continuous.)

With proper design, continuity can be maintained...

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

-Dik

Letter from the occupants...

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

-Dik

• https://files.engineering.com/getfile.aspx?folder=2afa5e4e-2694-413f-be1b-5

I found it concerning how easily the garage/pool area slabs detached from the perimeter wall, given that the notes call for #5 hook bars @12” oc (I don’t see any in the photos). I also have not found any section/details for how that perimeter wall is reinforced.

As previous posters stated, this slab was acting as a diaphragm to transfer lateral loads for the building and I would expect the connections to the exterior wall to be important to properly transfer those forces.

Quote (warrenslo)

No, there are three forces in a column, slenderness, punching, and axial.

Slenderness is not a force, and punching (shear) is in the slab, not the column.

Quote (warrenslo)

There was clear deflection in unit 1010 prior to collapse

To me, those photos do not indicate clear deflection.

Sorry I meant three forces and slenderness... Typing fast. And, I've always been taught to calculate punching as part of a column. Otherwise why are column caps centered around columns? Seems like you are being protectively picky.

Quote (DB27)

As previous posters stated, this slab was acting as a diaphragm to transfer lateral loads for the building and I would expect the connections to the exterior wall to be important to properly transfer those forces.

While this is possible, I think the roof work + additional stone/tile/marble within units + HVAC equipment + aging of the building contributed. To date there is nothing I see conclusively stating the parking/pool deck collapsed FIRST. Every witness didn't have a clear view. The damage pattern (look at Vegas implosion patterns) is clearly due to the rest of the building falling on it, otherwise the pool would have fell slightly as well. It didn't it's solid. Beginning to think there are shills on this forum...

I think it's pretty clear at this point that multiple bays of the lobby level (as it is called on the structural drawings ca. 1979) failed first. AtomixPro's video looking down the garage ramp at the debris/waterline, and the eyewitness accounts as described/recounted above tells us that at SOME point, perhaps minutes prior to the superstructure collapse, portions of the lobby level slab had collapsed. One south of the garage ramp ('tiktok video'), and one in the guest parking area (eyewitness account, see above).

I think we have also established that the first part of the superstructure to fail was either column I/9.1 or K/9.1. (or generally the column area, or tributary, or perhaps the influence zone). That said, it's still not entirely clear if the columns interior of grid 9.1 (grid 8/7) failed even before that, which would be closer to the ramp area slab failure (per the 'tiktok' video). But, video of the collapse appears to show the column(s) at grid (I or K)/8 still supporting the roof just after the collapse begins.



Regarding the columns that may have been in contact with soil in the planters: I have found a particularly interesting item. See clips below. Both of these columns were not only located at/in/part of the planter, but the planters were irrigated (I never considered that plants need water). Clips from pages A2C-1.0 and LR-1 of the renovation drawings.

Quote (warrenslo)

The pool deck collapse relies on a theory that the pool deck collapsed and the columns adjacent were exposed and failed, they fail to recognize the pool slab stepped 2-4 feet at these columns and the slabs were not continuous.

I think there's some merit to this idea.

see [Jun 21 00:49]

Quote (dold )

'...
Looking at the video it appears that the column on grid I/9.1 was the first to go, although I can't see the interior columns to the north.
...
1) this looks like a low point (+10'-10" only open to the pool area to the east) where the slab would seem to be at higher risk of corrosion. ;
2) there is a 2'-6" step in the slab at this column joint.
2.a) this leaves a decent offset between a potential lateral load implied by a failed slab panel (possibly yellow area?), and the restraint at the primary deck at +13'-4".
...
Next, perhaps since all the columns along grid 9.1 are tied together with a beam at the slab step, if column I/9.1 (i.e. "the suspect column") collapsed first, that could potentially mobilize a force on grid 9.1 columns acting to the west, with load path bonus from the steel in the perimeter beam.

This seems to be reflected to some extent in the collapse video - the columns along grid 9.1 are among the first to go, starting at the suspect column and propagating east.

Quote (warrenslo)

otherwise the pool would have fell slightly as well.

The pool is supported by walls that extend to the foundation. Look at the drawings.

Quote (warrenslo)

To date there is nothing I see conclusively stating the parking/pool deck collapsed FIRST. Every witness didn't have a clear view.

There is a clear video posted above that shows a collapsed lobby level slab just south of the garage entrance ramp. Before the main collapse.

Quote (warrenslo)

And, I've always been taught to calculate punching as part of a column. Otherwise why are column caps centered around columns? Seems like you are being protectively picky...

Beginning to think there are shills on this forum...

...Because the structural engineers that you are calling "shills" don't agree that the three forces in a column are "slenderness, punching, and axial", etc.? We're trying to have a discussion about this building collapse. We're not having a contest. We're trying to keep the discussion informed with sound technical information, not 'things you learned somewhere once'.

I don’t understand the objection to the bars unzipping? Why would this require defective concrete or other defects? A bar is much stronger in shear than concrete at that edge distance, so why can’t a bar simply rip out? If a column collapsed and a mid span went into negative bending and formed a hinge, then ripping out of bars as the hinge opened is what you’d expect. Like when you snap a piece of celery and the threads tear thru the fresh.

Quote (warrenslo)

There was clear deflection in unit 1010 prior to collapse, the mislabeled column I found (see post above) is between the coat closet and laundry in the photos below - this deflection is more than normal in concrete (in steel is this is more normal in a long span.)

I would be surprised if you didn't know that interior shots are often taken with a wide angle lens which introduce distortion to the image. Unless you know what lens was used you can not rely on these images for analysis.

Also, please don't leap to accuse people of being shills because they disagree with you.

Quote (Tomfh (Structural)30 Jun 21 09:18)

Unzip objections

Tomfh, you are correct and I believe most would agree with you. Objections are probably just short-cuts taken in reasoning. So unzipping itself is not necessarily a sign of defect.

This discussion is very interesting to a lot of people and is one of the great pluses for this site I feel.

Question here - Could it be possible for column L10 to have failed first, but the initial impact seen was on the adjacent pool deck?

I still find it difficult to believe that failure of a single column can bring down a building, but if that one column failed and then that led to the pool area slab pulling away from the external wall and then rippling the failure across the deck area as witnessed by a number of people then that effect went into other columns?

The failure may have started at the pool deck area, but I think a lot of people are trying to work out why and not seeing a good reason.

The column in question looks on this plan view from a post above to be the most vulnerable to anyone entering down the ramp and running into it. Coupled with apparent surface water ponding over the years maybe it simply failed first?

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

If left you kids alone for half a day, and you posted like crazy and had shill battles... (edited because I hit Submit instead of Preview, wish this site would implement recalling an accidental post)

The objective of all engineers is to not make something fail-proof, but rather, fail-safe.

It is impossible to avoid failure. Fail-safe does not mean something will not fail. It means when it does fail eventfully, it will still be safe (meaning not costing human life).

We will never be able to convince society something is going to fail until it does. In college I was trained people respond to deflection, even if such deflection is within specs. I I remember freaking out as a kid my first time flying on a jetliner after seeing the wings deflect in flight. So critical designs should show warnings. A radical idea would be to add non-structural elements to a building that shatter and collapse as a warning.

The real culprit is not that the building was too weak - it was too strong and did not show real concrete signs of distress so people would self evacuate. (Or the column design could have been totally and completely wrong) In this condo, those that got warning, got out alive. We are must learn, the police, government inspectors, will not protect us. Firefighters will, but they are always after the fact.

Quote (warrenslo (Structural)30 Jun 21 07:33)

...roof work + additional stone/tile/marble within units + HVAC equipment + aging of the building contributed.

This would be a good idea to pursue. The additional loading of the heavy flooring and countertops can be estimated easily. In the 80's it was all shag and Formica. Many of the balconies had tile added which to me is not ever a good idea.

Do we know what the actual design loads were and how they compare with modern-day assumptions? For example, going to the tables of ASCE 7 the assumptions for LL are baked into the intended use of the space. Dead loads are calculated and include some level of finishes, cladding, and permanent equipment. But where did they draw the line between DL and LL in 1981 and how exactly was DL calculated? Were countertops and flooring considered DL? Were they plugged in from some table in some predecessor standard? If so did that standard assume all shag and Formica? This is something about the history of our profession that I'm admittedly uninformed about.

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

jrs as structural engineers we generally don't design for fail safe. The exception would be requirements for progressive collapse design for critical federal buildings. Even those requirements are relatively new and were the result of the OKC bombing. There isn't an engineer on the planet that would typically look at load transfer if a column was removed for example.

In most buildings there are members that if they fail completely the consequences would not be good. The saving grace for us as structural engineers is the fact we generally try to design so we have ductile failure mechanisms and for brittle failures (like punching shear) there is a higher factor of safety applied since the failure is generally without warning.

One thing with buildings, even when there is a failure of a critical element most of the time you see localized failures only and the building finds a different load path that wasn't intended but was there. The buildings are much smarter than we are.....

I suggest posters suggesting that all damage to the pool deck/parking area is solely a result of the main building collapse should review the collapse footage again

https://www.youtube.com/watch?v=KR29pLccutY

There are mere seconds between the 2 sections of the building collapses.

Obviously eyewitness testimonies aren't completely reliable, but here we have many testimonies (and video) testifying some sort of obvious collapse in the pool / parking area, a significant time before the main building collapse. Enough time to make a phone call and describe what has been happening before being caught in the main collapse. Enough time to go to security, escape the building, etc.

Watch the video of the collapse, look at the first portion of the building collapsing, then imagining trying to make a phone call, go recover your family, etc etc in the mere seconds before the second portion collapsing.... there is simply not enough time.

@tab101:
The eyewitness testimony refers to the pool deck collapsing, which is a couple minutes before the start of the security footage.

@structuralex yes agreed. There are suggestions here that the damage was caused during the building collapse, not prior. And that (for example) the woman who spoke on the phone to her husband and told him about the pool area collapsing before being (presumably) killed in the building collapse had made that phone call and had that conversation in the mere seconds between the first part of the building collapsing and the remaining part as seen in the security footage. I am pointing out that the theory that there was no obvious damage to the pool deck / parking area at least minutes before the building collapse is inconsistent with the multiple eyewitness testimonies, the security camera footage and other evidence available.

Engineers inspecting for damage to South Florida condominiums in the wake of the Surfside Towers South collapse should be aware that the only engineers allowed to inspect threshold buildings (Threshold building means any building which is greater than three stories or 50 feet in height, or which has an assembly occupancy classification as defined in the Florida Building Code which exceeds 5,000 square feet in area and an occupant content of greater than 500 persons) or to do 40 year certifications for them must be licensed as Special Inspectors (S.I.), by the Florida Board of Professional Engineers.

Older buildings built before the Threshold Building definitions came into effect are included if they meet the current definition above.

While local Building departments are apparently not aware of this requirement, as demonstrated by their Special Inspection Forms and 40 year Recertification Forms which do not require an S.I., anyone not licensed as an S.I. who does the work may be subject to disciplinary action by the Florida Board of Professional Engineers.

Any engineer who does this kind of work should become aware of the requirements of the Florida Statutes, including F.S. 471, F.S. 455, F.S. 553.71 and the 61G-35 Florida Administrative required by the Florida Board.

It seems these 2 events are somehow connected even though they happened on opposite ends of the building:
- The pool deck collapsed a few minutes before the main building collapse, as per many eyewitness accounts.
- Apparent rubble and burst water pipe a few minutes before main building collapse, as per video by neighbour.

DB27 might have something here.

The original 87th terrace was a car park / access to the beach



Then they cleared the previous building in about 2015 and then it looks to me like they sheet piled the perimeter, much closer to the existing wall / boundary.
Did this affect the possibly weak join between the slab and the wall?



So if the slab to wall joint failed then you have a slab with several metres of cantilever with point loads on those columns.

Can someone better than me find the details of the slab to wall joint?

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

Quote (trenno)

Post of 29 Jun 21 14:21

Not that this caused the failure, but fully agree about the lateral stability in the East-West, it seems hopelessly insufficient. Laterally, the building is obviously relying on frame action and some bracing from internal walls and possibly a bit of ‘outrigger’ help from the slabs built into the core.

I also did a calc and find that columns on I8, K8, L8, M8 are far from meeting ULS requirements. If you strip all the load and material factors out (to understand why the building stood for so long), the concrete was loaded to about 50% of its specified strength. Possibly cube results showed higher strengths to assist. So, on paper, almost no redundancy. PS, Trenno, I used 13 suspended slabs and then 14 from K to P where the penthouse was built on the roof. So my check was for the basement columns and have similar concerns.

I find that columns on grid 10 are closer to satisfying ULS. But having said that, the 460mm fold in the slab (step beam) along grid 10, together with the planter beams all coming into a column which already had 5.5% area of steel, mixed with pour/construction joints and probably a mixture of concrete strengths (slab vs column) and possible concrete compaction challenges makes this a very vulnerable area. I wonder too if the external podium slab wasn’t cast off the critical path resulting in cold joints, compromised continuity etc.

So may things to consider that a visual inspection won’t always pick up. All the evidence from witnesses supports an initial collapse at the upper visitors parking, or at least in that vicinity. If I were on the team I’d prop the podium of the sister tower and carry out some column head inspections to rule out punching shear shortfalls, whether a result of corroded rebar or poor rebar placement or whatever. I wonder if that gazebo structure on the podium was approved. I’d also carefully inspect the underside of gridline 10 for any distress and take a serious look at the column design on grids I.

Here's a section detail of the perimeter basement retaining wall. The ground floor plan calls up #5@12.

An interesting exercise. Step through the first ten seconds of the last posting of the video. Click on the video to stop it and then use the comma to step backwards and the period to step forwards.
There may be four or five steps per frame, but it is not consistent. At times a frame will jump to the next frame in only one step.
At the start of the video, the building collapse appears to have started. There are 5 or 6 lights showing.
A few steps later all but two of the lights are out.
Then a light goes out in the surviving building as well as the two lower lights.
One frame before the one second mark, a light comes on lower down in the collapsing section of the building. It is there for about 4 steps.
It is interesting that some lights stayed on even as the building was falling.
Ten steps into the first second, the second section of the building (behind the first section and a part to the right) starts to collapse.
Nine or ten steps before the ten second mark, the third and final section of the building starts to collapse.

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

I just went through some of the documentation, and one thing that immediately stood out was the highly technical details relative to what a construction worker would be expected to understand.

Refer to the 2 details below as an example. I was taught to notate the drawings clearly enough that a layperson would understand.

However these would be something you'd typically find in Concrete Standards. It's the engineers job to 'translate' it without risk of misunderstandings.

I'd say it's plausible that this was a contributing factor to the collapse.

Quote (structuralex)

I just went through some of the documentation, and one thing that immediately stood out was the highly technical details relative to what a construction worker would be expected to understand.

Refer to the 2 details below as an example. I was taught to notate the drawings clearly enough that a layperson would understand.

However these would be something you'd typically find in Concrete Standards. It's the engineers job to 'translate' it without risk of misunderstandings.

I'd say it's plausible that this was a contributing factor to the collapse.

In my experience, the details you show are pretty common and are intended more for the detailer who is producing the rebar shop drawings.

I once saw a unique reaction to a similar lack of detail.
It was for a fire water supply line, The routing had a number of corners that were not square and would require specially fabricated fittings.
On the bidders walk around tour, the estimaters pointed out to each other all of the problem spots so that know one would have a low bid as a result of overlooking an expensive detail.
One bidder, Stan, ignored the problem areas in his bid. He got the job.
For each problem area he designed and had fabricated the needed parts.
Then, under the heading of "Not Detailed on Bid drawings" he sent the invoice including engineering and drafting time to the engineer as an extra charge.
The engineer allowed the invoices as extras.

Same job:
There was a hard, nonnegotiable deadline set by the fire marshal. If fire water was not available by the deadline the fire marshal would close a vital terminal in a new public transit link.
The bidders were all contemplating work around the clock and massive overtime expenses.
Stan made a proposal to the Fire marshal.
I will supply a temporary fire water service within a few days., if you will accept that as meeting your deadline, and allow time for the permanent work to proceed in an economical fashion.
The Fire Marshal was most concerned with protection of the public as soon as possible and agreed to the plan.
Career wise, he was able to send the signal that he had negotiated an arrangement whereby the public safety was assured sooner and at much less cost than originally expected.
Stan made a lot of money on that job.
It was fun working for Stan. I miss him. (RIP)

Bill
--------------------
Ohm's law
Not just a good idea;
It's the LAW!

Quote (structuralex (Structural)30 Jun 21 14:34

I just went through some of the documentation, and one thing that immediately stood out was the highly technical details relative to what a construction worker would be expected to understand

)

These seem typical to me. Typically shop or placing drawings would break it down further for installation.

The yellow column in the Tik Tok video is on grid 10 (the south side of the building). The refuse in the background looks like the failed plaza slab. The failed water line is probably the line that fed the pool.

Quote (Why would this require defective concrete or other defects?)

More likely that the reinforcing had corroded and the expansion products had compromised the concrete. There could also be insufficient cover.

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

-Dik

Here is a download of the TikTok video for posterity sake. Stuff gets deleted from that site all the time.
https://files.engineering.com/getfile.aspx?folder=...

Quote (So unzipping itself is not necessarily a sign of defect.)

See my comment above... I would suggest it was a defect; normally placed reinforcing does not 'unzip', it stays in place to support concrete.

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

-Dik

The drawings seem to show the swimming pool ending at either Column Lines M or N, depending on which version of drawing you look at. It's unclear how the pool steps and the jacuzzi are accounted for. Could either of those have affected the continuity or development of the two-way reinforcing in that area enough to make a difference? I know that in non-typical areas of a two-way slab steel placement can require quite a bit of judgement. And the slab failure does seem to hit right at the corner of the jacuzzi.

Quote (Teguci )

The yellow column in the Tik Tok video is on grid 10 (the south side of the building). The refuse in the background looks like the failed plaza slab. The failed water line is probably the line that fed the pool.

It’s M8. The debris visible in that video is where M9.1 should be. The pipe is a sanitary line.

Quote (Santos81)

It’s M8. The debris visible in that video is where M9.1 should be. The pipe is a sanitary line.

No, it's M9.1 (or M10 on sheets that don't have a 9.1 row labelled). M8 is the lower end of the ramp, where the half wall ends. The full height wall on the left is the eastern stairwell shear wall (which would be M2–M4, approximately).

Quote (NOLAscience)

Where did the pool contractor make his comments about the standing water in Parking Space 78? I would like to hear the exact wording.

Based on the basement storm water drain plan, this should not be overlooked. Someone posted a Miami Beach tide chart above, but that is not the appropriate reporting station relative to the site. The times and heights for Surfside Beach differ.

I’d take a seriously hard look at the foundation plan change in pile types revision.

I'm confused by the TikTok video as well. It's hard to tell if it's column M8 or M9.1. Either way, the debris would be from the recreation room and restrooms above so the water is likely coming from there or fire sprinklers on basement lid.

Quote (Santos81)

It’s M8. The debris visible in that video is where M9.1 should be. The pipe is a sanitary line.

I see the shearwall (grids 3 to 4), then the half height ramp wall with a column at the end (M/8) then the yellow column (M/10). Looking at the soffit I see the entrance, then 2 step downs before the end of the shear wall, then something that looks like a beam at grid 8 (there is no documented beam at grid 8 - maybe a sign?).

I only point it out because, on first glance, I thought it was showing damage under the main building (M8 as you say). With the damage being from the south of the building, the pool plaza area, it corroborates other testimonies. Now the questions become:
- Did failure begin at the planters or west of the pool and why? Testimony from 111 - there was popping noise, load bang, then witnessed pool plaza collapsed from lobby. Maybe that collapse progressed from the planter area collapse?
- How did progressive collapse of the plaza eventually fail the building columns?
- What is Beam A? Called out on the drawings but not detailed on the beam schedule. To be provided at runtime?

Per the details provided by Structrualex- Was the plaza slab CIP beams or flat slab? If flat slab- how was punching shear accommodated at the slab to column interface?

Flat slab. Or, more accurately, flat plate.

Penthouse Update. The following has been posted by the Town of Surfside recently.

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

Dec 2, 1980 letter:

Quote (You are informed that Permit #18033 and Permit #18034 for penthouses located at 8777 Collins Avenue and 8877 Collins Avenue are revoked and cancelled. You are instructed to immediately cease any further construction on any penthouses at 8877 Collins Avenue and 8877 Collins Avenue. We were instructed by the Town Attorney that in his opinion this is a violation of the Code of the Town of Surfside, and that you were so advised prior to the issuance of the permits.)

Dec 11, 1980 letter:

Quote (On Tuesday, December 9, 1980, the Town Council adopted an ordinance granting the Champlain Towers an Exception to build two penthouses located at 8777 Collins Avenue and 8877 Collins Avenue. Therefore, I hereby withdraw my letter of December 2, 1980, to cease any further construction on the penthouses. You may now proceed with the construction of the penthouses effective immediately.)

I see a lot of ideas swirling around here, but suggest some of you read up on plaza drainage systems. I see so many plaza drainage system failures due to poor architectural design and/or implementation. This leads to a lot of concrete damage that works it way from the concealed surfaces outward to the visible surfaces.

In my view, you've got a plaza drainage system on an old-school reinforced flat slab system with large planters right next to the point the collapse initiated. This all points to a corrosion induced punching shear failure that took out several perimeter columns and initiated a progressive collapse.

I think PE's should instead be watching what way the lawyers/officials go with our "duty to warn". I was disappointed by Batista's response on national television last night when it was questioned why PE's aren't required to notify the building dept when deteriorating concrete is observed. If PE's will be required to notify the building official for any type of concrete deterioration, it will set up an interesting situation where PE's then get sued for unreasonably causing large buildings to shut down.

Quote (spinspecdrt)

I'm confused by the TikTok video as well. It's hard to tell if it's column M8 or M9.1. Either way, the debris would be from the recreation room and restrooms above so the water is likely coming from there or fire sprinklers on basement lid.

If the water was coming from a broken fire sprinkler line the fire alarms would've sounded which according to all the information we've seen didn't happen. Or at least didn't happen prior to the major collapse. It probably would've helped if it had sounded really on in the series of events since I probably would have helped evacuate a few additional people.

I 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.

While not technically not a sinkhole, it is something very similar.

One of those remarkable stories of survival is of Champlain Towers South resident Iliana Monteagudo of Unit 611, who woke up that horrific night to the sound of cracking.

“Something inside of me said, ‘Run, because this building will collapse,’” she explained.

Monteagudo says she was sleeping in her sixth floor unit at around 1:30 a.m., early Thursday morning, when she suddenly woke up and found a crack growing along her living room wall.

https://www.local10.com/news/local/2021/06/30/rema...

Quote (What is Beam A? Called out on the drawings but not detailed on the beam schedule. To be provided at runtime?)

Beam A is detailed on the top left of Lobby Level Framing Plan

Quote (The pipe is a sanitary line.)

Oh, sh*t...

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

-Dik

Four more bodies have been removed from the rubble. It's obvious that the rescue effort has now become recovery.

Four More Bodies Found In Collapsed Florida Condo Rubble; At Least 16 Dead

Severe weather in coming days could further test the search and rescue effort.

https://www.huffpost.com/entry/florida-condo-colla...

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

"Engineer brought in by Surfside says Champain Towers’ North, East condos are safe"

https://www.youtube.com/watch?v=8WqraSrYTs8

A peek into the current state of the North tower, which is in relatively good shape to my untrained eyes. It seems the eventual report will be just as much a tale of two condo associations as it is a report on the structural issues in the South building.

How many of you have access to a Schmidt Hammer and take it with you on Repair consultation walks?

I have... usually kept it in my vehicle... along with my other bag of 'goodies'.

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)

There was a post above about the podium slab having additional pavers, but the photos show tiles, so I'm not sure what this is about.

I did post a snip of the Morabito prelim repair drawings (29 Jun 21 15:08), that indicated multiple layers of tile/pavers were found to exist on the pool/plaza deck area. This suggested to me that perhaps the pool/plaza deck had been tiled over at some point, possibly adding an additional 10 to 20 psf load to the slab. It's hard to say for sure because the original drawings are a mess, but it looks like the original spec was for a single layer of "keystone" pavers.

Is the only technology for a building's concrete and rebar inspections - the human eye?
You can patch and paint over cracks, cosmetically all looks wonderful, an inspector could be fooled.
Especially for a 40 year interval, why isn't there more than a look-see, use something penetrating like x-ray?

edit: I see the press is already asking this, as well as the "40 year" number should be based on environment, not the Miami DEA office building collapse in 1974. Link

Lol, run GPR on this building? I've gotten quotes over 40 grand just for the GPR and they couldn't decipher anything useful. Its not all that its cracked up to be.

Here is a high-res (9 MB) image of the pool deck failure which shows detail of the tops of the columns and the layers of the deck.

[edit]the image was being noticeably compressed so I made it a PDF.[/edit]

The clearer PDF is available here:

https://files.engineering.com/getfile.aspx?folder=...

• https://files.engineering.com/getfile.aspx?folder=3f116671-4742-4f3a-8921-1

Quote (Spartan5)

It’s paraphrased, here:

I'm looking for the original statements, not the paraphrase, which I had already read.

Was the slab around the corner of the jacuzzi in positive or negative bending? Hard to say, isn't it? That's my point...especially since I can't see the opening accounted for on any of the structural drawings. (Landscape drawings, yes, but not the structural ones.) I'm not saying that that caused the collapse but it probably gave the fracture a good path to propagate.

Discussed above and agreed not relavant to collapse but just curious:

Were they really counting on moment frame action between column & floor plate system?

The shear walls do seem inadequate in the east west direction.

Quote (AtomixPro)

This is interesting. Video of deck failure visible through the north parking entrance. All prior to the full on building collapse.

I don't use TikTok. Ask him/her when this video was taken and if there is any other video.

I am wondering about the source for the dripping water, among other things.

https://www.dailymail.co.uk/news/article-9741049/E...

I disagree that the unzipped rebars do not indicate a defect. While it is normal for rebar to pull out of concrete with enough down force, what is not normal is that there is no concrete adheared to the rebars. I base this on engineering for a demo company for 20 years. Either the concrete was soft or the rebars corroded to the point there was no bond with the concrete.

Quote (JimmyP80)

the slab-column joint's are a universal issue

Definitely. Also,

(1) Water and salt and lack of slope of the pool deck may have contributed to that failure.
(2) Adding load to the the column by building a penthouse whose loads may not have been included in the calculations could not have helped.
(3) Standing water in the basement did not help with (1).
(4) Rebar ripping clean implies the potential that concrete in the parking and lobby slabs that did not meet specs. This did not help.
(5) Column "" was in a planter for 40 years, with irrigation and rain and soil.

Let's add to this list. Who has a contribution to be "(6)"?

I agree, GPR guys charge way too much, either due to equipment costs or profit but it's not detailed enough of an image. But this is it, the eyeball is all we have?

Early press mentioned a crane had been on site the day of the collapse, for starting the roof work. I found it strange the guy left site, with no evidence of unloading materials.
Just wondered where you'd park it on the lot, if this was a factor.

TikTok frame enhancement and perspective:







The parallax shifts made these overlays difficult, that is to say that they were a good start but I didn't do a good enough job. Please see my later posts for better alignment where it really matters.

The firms they brought in, Musser Rutledge and KCE are impressive. I have worked with Alan Kilshimer, whom is principle of KCE, and he can take control of a heated meeting like nobody else. Back in 2014 the talk was he billed $600/hr for this type of work.

Sym P. Ie, don't those numbers painted on the columns indicate parking stalls? Number visible looks like 27 (or 77?). Which would place damage further in, or to the west, at time of shot.

Quote (NOLAScience)

I don't use TikTok. Ask him/her when this video was taken and if there is any other video.

I am wondering about the source for the dripping water, among other things.

The TikTok video was taken by Adriana Castillero, who was staying in the hotel next door. They were by the pool. You can see on google the hotel pool has a direct view of the North face of the collapsed wing and garage.
Her husband Roberto Castillero was interviewed by the local media. You can see the interview here. He describes seeing a collapse in the garage.

https://www.youtube.com/watch?v=BvkRmtmB-Fw

Multiple enlightening interviews of the unit 111 tenant, Sara Nir, have just been released (we've heard from the son the morning of the collapse, but the mom was the one who saw the upper parking deck collapse in real time from the lobby. It's odd how she describes how the noises were coming from above. It seems unlikely given all the known details so far, but who knows.

Highly recommended: https://www.youtube.com/watch?v=1gie0XVOFl0

From the drawings, the debris seen in the tiktok video would be either immediately below her unit or just outside her unit in the patio/pool deck. Others here have been trying to sort this out by counting columns but it seems inconclusive thus far? There was no mention of her floor collapsing, which I imagine her son and daughter who stayed behind for a bit would have commented on.

One of the problematic planters and the first failed columns were all near unit 111.

Ironically the other escapee, Maria Monteagudo, was from Unit 611. Above 111. Their proximity to the failure saved them.

Quote (NOLAscience)

The sun shade pavilion installed without top steel or enhancement to the pool slab added uplift forces to the already compromised slab-column connections.

Quote (TheGreenLama (Structural) 30 Jun 21 20:12)

don't those numbers painted on the columns indicate parking stalls?

Yes they do and I was perhaps a little hasty in not better identifying the column. A crop of the parkade map from the posted documentation may be more helpful. The frame view is clearly of the northwest corner/column of stall 27.



A closer look beyond this column may be the first indication of structural collapse.



EDIT: Image deleted and replaced with a more accurate overlay in my next post

Quote (warrenslo)

I think the roof work + additional stone/tile/marble within units + HVAC equipment + aging of the building contributed.

Quote (jrs87)

The additional loading of the heavy flooring and countertops can be estimated easily. In the 80's it was all shag and Formica. Many of the balconies had tile added which to me is not ever a good idea.

Quote (bradw1128)

Do we know what the actual design loads were and how they compare with modern-day assumptions?

All - Good points about the weight of materials in 2021 vs 1982 and the uniform live loads, but I don't think it will play out as a significant factor. Even 3 cm granite only weighs 18 psf, and there are large open areas in a kitchen, say, with only tile (typ max 7 psf) flooring and not much else.

One typical code used in 1981 was very similar to the 1982 Uniform Building Code. I used a similar code when I began as an EI in the late 80s, and 40 psf sounds like what we used for residential units.
https://digitalassets.lib.berkeley.edu/ubc/UBC_198...
The Uniform Live Load from Table A23-1 of that code is 40 psf for Residential use,
using these definitions:
"DEAD LOAD is the vertical load due to the weight of all permanent structural
and nonstructural components of a building, such as walls, floors, roofs and fixed
service equipment."
"LIVE LOAD is the load superimposed by the use and occupancy of the
building not including the wind load, earthquake load or dead load."

I would consider flooring (tile), cabinets and countertops, and furniture to all be live loads, then and now, because all can be removed with simple hand tools.

There was a provision for having only dead load in one span and full uniform live load in the two adjacent spans, because this can be a critical loading condition. Live load would be everything other than the structure itself (concrete columns and slabs), in my opinion. I'd even consider plumbing and electrical to be live loads, because they could be removed from one span while being present in the adjacent spans, which could be fully loaded to 40 psf with those items plus flooring, cabinets, countertops, furniture, and people.

The live load reduction was allowed to be:

R=r(A-150) .................... (6-1)
The reduction shall not exceed 40 percent for members receiving load from one
level only, 60 percent for other members, nor R as determined by the following
formula:
R = 23.1 (1 + DIL) ................... (6-2)
127
2306-2308 UNIFORM BUILDING CODE
WHERE:
R = Reduction in percent.
r = Rate of reduction equal to .08 percent for floors. See Table No. 23-C for
roofs.
A Area of floor or roof supported by the member.
D = Dead load per square foot of area supported by the member.
L = Unit live load per square foot of area supported by the member.
For storage live loads exceeding l 00 pounds per square foot, no reduction shall
be made, except that design live loads on columns may be reduced 20 percent.
The live load reduction shall not exceed 40 percent in garages for the storage of
private pleasure cars having a capacity of not more than nine passengers per
vehicle.

Many of the building beams would qualify for taking a LL reduction, but I have not calculated it. You can do the calculations, but (1) we don't know what furniture or other movable items were in each unit last Thursday, and (2) I don't think heavier materials on counters and floors will turn out to exceed the 1980 design loads, even with the applicable LL reductions. One exception would be in rooms used as offices or studies, which might have storage of paper files.

Please reply with your thoughts.

Quote (smaarch)

the posts in defense of a profession instead of finding the problem

Please be more specific. I see that the vast majority of posts here are directed to studying the problem through evidence such as drawings, photos, and eyewitness testimony. Most contributors are willing to stand corrected when early evidence is refuted by later evidence. I see contributors changing their opinion as they take in new information. For the posts that seem to just jump in, make a statement, and leave -- I mostly ignore them, unless they say something profound by shear luck.

So, again, please point to the contributions that you say are defending the profession instead of finding the problem.

RE: The upcoming 40 year recertification

Could the anticipated 40 year recertification have CONTRIBUTED to the board's inaction in 2018? I can see board members saying, "We don't need to do this now. Let's wait until 2021, when we will be re-certified. Otherwise, we will end up paying for TWO engineering reports and some repairs done in 2018 and 2019 may not be sufficient to the 2021 reviewer.

Hmmmm... makes you wonder. To me, this is another argument for 10-, 20-, and 30-year inspections which are in sufficient depth and detail to catch and remediate developing structural problems.

To me, the inspections do not absolve the board of responsibility for allowing standing water in the garage without getting to the root cause of that in the very early years. You don't need an inspector to tell you that standing water that only leaves by evaporation is going to cause all sorts of problems.

Quote (Sym P. le (Mechanical)30 Jun 21 20:41)

Broken column

I don't see any floating dust in video. My subconscious says the item is a washing machine. The running water is worrisome and should have prompted a call to the fire department by the tiktoker.

Quote (spsalso)

I am looking at, in photos, the rebar at the top of the columns. I am not impressed. Imagine if there had been some horizontal pieces 12' long running through that joint. Would it then have failed?

I seem to recall one or more posters on the original thread noting that today's code would require much more at slab to column connections. See, in particular, Seppe (Structural) @ 26 Jun 21 14:39:
"Slabs seem awfully thin, at least by today's standards for mild-reinforced flat plate construction. And no drop caps?..."

Quote (NOLAscience)

To me, the inspections do not absolve the board of responsibility for allowing standing water in the garage without getting to the root cause of that in the very early years. You don't need an inspector to tell you that standing water that only leaves by evaporation is going to cause all sorts of problems.

I wonder how many people really think this is a case? Boards for associations like this in many cases are purely politically motivated, the people who are elected have very little if any knowledge of construction, codes, etc. Especially with the building being this close to the ocean I'm sure many people were not concerned seeing water in the garage, it might have only concern them because they were getting their $500 shoes wet.

Don't forget, they were told by a representative of the local government agency that "they didn't have any major problems". Based on receiving information like that I can see why they were not overly concerned.

"Majority of Florida condo board quit in 2019 as squabbling residents dragged out plans for repairs."

"Despite increasingly dire warnings from the board, many condo owners balked at paying for the extensive improvements, which ballooned in price from about $9 million to more than $15 million over the past three years as the building continued to deteriorate, records show." From Washington Post article Link

Since no one has posted it yet, actual tides vs predicted tides from charts can be approximated from NOAA tide stations "South Port Everglades", FL "Virginia Key, Biscayne Bay, FL". Sunnyside is halfway between these.
June 24 1:30 a.m (I think this is the approximate time of the collapse.)
At both tide gauges the tide was falling, and not that far from low tide.
This is another data point, that might have some impact on the stresses in the building as close to the shore water pressure in the ground changes with tide? I am not going to guess if the change of support from tidal action has any impact on the event.


I plotted these using local Miami time, and NAVD88 elevations. The drawings precede NAVD88, so they likely use a different elevation datum.

Reference Station Home Pages, look for Available Products>Water levels
https://tidesandcurrents.noaa.gov/stationhome.html...
https://tidesandcurrents.noaa.gov/stationhome.html...

I believe it is posted above but you really have to read the Surfside Building Inspector's letter to Guillermo Olmedillo, Town Manager.
He describes the meeting as successful. The tenor of the letter, seems to be that he alleviated their fears regarding the Structural Engineer's report.
There is something wrong with a city's building department when the individual that reads a Structural Engineers report and then offers 'interpretation' that downplays what the report contains; is not an engineer. Rosendo Prieto, the building inspector at that time was qualified for 'Plan Review' but that is for Code, not actual structural plan review. Both the city and Prieto are in deep water. Link

Quote (Mark R Regarding Fire sprinklers)

That is a great point about the fire sprinklers setting of the alarm. Any idea if there were fire sprinklers in the basement? If there were, why didn't the alarm go off? If there were no sprinklers, should there have been?

>>>Both the city and Prieto are in deep water.

In the US municipal engineers are statutorily absolved of liability, so I'm led to understand.

I have to agree with TheGreenLama, most homeowners are going to bulk when they are told they have to come up with 100k to do repairs. It is just not easy for folks to do. I lived in a south Florida community for several years that had HOA dues, and part of the dues went to pay for water to the units which was a majority of the cost of the dues. Our yearly meeting would bring several residents who would complain about the HOA dues and demand that the plumbing be upgraded so that water would be removed from the HOA dues. The board would say the same thing every time, we looked into and it would require a $3000 assessment per unit, as soon they said that everyone would bulk and say to leave the plumbing the way it is, and that was just 3k I can't imangine what residents would say to 30 times that.

It isn't an easy situation.

Quote (Spinspecdrt)

That is a great point about the fire sprinklers setting of the alarm. Any idea if there were fire sprinklers in the basement? If there were, why didn't the alarm go off? If there were no sprinklers, should there have been?

I'm not sure what Florida codes were at that time. In many areas sprinklers in the park area would not have been required in the timeframe that the building was built.

Has anyone actually seen the 2020 Morabito Consultant report referenced in the letter the head of the condo board sent out to the residents in April of this year? I’ve seen the original 2018 report posted in this thread, but several news stories keep referencing the newer report. NPR has some more recent pictures of the concrete damage from 2020 as well; I’d like to read it if anyone can find it!

https://www.npr.org/sections/live-updates-miami-ar...

Quote (Mark R)

I'm not sure what Florida codes were at that time. In many areas sprinklers in the park area would not have been required in the timeframe that the building was built.

Drawing from ROLL 1-0005 details this sprinkler layout in the basement parking.

Quote (Kestrel42 (Bioengineer) 30 Jun 21 22:40 Has anyone actually seen the 2020 Morabito Consultant report referenced in the letter the head of the condo board sent out to the residents in April of this year?)

Posted by the Town of Surfside not long ago: (EDIT: Looks like mostly balconies, but there is a lot structural work.)

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

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

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

I've reconsidered the Google Earth overlays posted earlier since the parallax was more problematic than anticipated. I'm posting a GIMP file of several layers that superimposes three layouts (Garage, Lobby, Typical Floor) from the city documents over a Google Earth layer skewed to match the property lines of the drawings (I still have to identify the unit numbers with better certainty, thus they aren't labelled).

The following image is what falls out. It identifies the potentially broken column as one that supports a planter outside of the building footprint.



From earlier:



It's not clear whether these planters were original or a refit.



This does not suggest an alternate initiation opposed to the work that warrenslo did earlier, rather it just explores what the TikTok video reveals. I believe it supports the theory that the pool deck collapsed several minutes prior to the main event and shows the extent of this precipitating event. As others have stated, the deck collapse likely triggered fire alarms, and would explain the quick arrival of the fire department.

I believe there WERE sprinklers in the garage, and that they show in a photo posted by Engr1888 at 3:04 on June 27 in the now-closed first part of this topic.

I suggested some time earlier that the alarm that should have been transmitted to the fire department would have a time stamp. This would then indicate the time for the pool deck collapse.


spsalso

Quote (epoxybot)

I believe it is posted above but you really have to read the Surfside Building Inspector's letter to Guillermo Olmedillo, Town Manager.
He describes the meeting as successful. The tenor of the letter, seems to be that he alleviated their fears regarding the Structural Engineer's report.
There is something wrong with a city's building department when the individual that reads a Structural Engineers report and then offers 'interpretation' that downplays what the report contains; is not an engineer. Rosendo Prieto, the building inspector at that time was qualified for 'Plan Review' but that is for Code, not actual structural plan review. Both the city and Prieto are in deep water.

The email follows below. It doesn’t say anything about alleviating anyone’s fears, offering an interpretation, or downplaying anything.

I’m not looking to point fingers because we still don’t know what happened. But as downplaying things go, the structural issues were given a paragraph or two on page 7 of 9 of the report. Subsequent to that, the Structural Engineer completed extensive design work over the course of 14 month. I’ve yet to see where any sort of alarm was raised about a building that was primed to collapse.

Perhaps there was a geologic failure or some element of the construction that was not per plans/spec. But other than that…

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

Quote (The email from the inspector)

ABO Pena and myself were invited and attended the Condo Board/Unit Owner meeting at the Champlain Tower South last night and it went very well. The response was very positive from everyone in the room. All main concerns over their forty year recertification process were addressed. This particular building is not due to begin their forty year until 2021 but they have decided to start the process early which I wholeheartedly endorse and wish that this trend would catch on with other properties. If you have any questions please let me know. Thank you.

I have a hard time hanging this on the building inspector.

Quote (Sym P. le)

It's not clear whether these planters were original or a refit.

Reviewing the aerials, previously, the planters had palm trees in them since at least 1999. That was until 2018 when the trees were removed.

Link for Miami-Dade Aerial History

I'm moving further away from sinkhole or vibrations from a seismic event (submarine quake).
Further away from blame being cast on building contractors.
Neither of those are factors here.

If the planters had drainage issues, it's possible that they rotted the columns upon which the sat. OUCH!

Replying to spsalso:

Miami Dade County alarms records are managed by Captain Nelson Enriquez, Deputy Fire Marshall, 305-416-1692

Using an aerial from 2005, the proximity of columns K10 and L10 (identified by warrenslo earlier) to "column 27" visible in the TikTok video is telling. Planters sit atop most of the columns along grid 11.1 and this arrangement has been in effect for some time.



Parking stall 78, which is adjacent K10, was reported to have standing water issues.

So here's my latest story/hypothesis:
The slab and beams on the building side of the planter columns failed in shear due to hidden deterioration. Concrete beams on either side of the planters, framed into/near the building columns started putting more moment on the building columns causing cracking and noise that was experienced by rooms 111 and 611. In addition, the loss of back span put more moment on the adjacent plaza slab span which yielded in moment until suddenly failing the slab to column connection in shear. This sudden failure then quickly overloaded the columns adjacent to the 29 ft span next to the pool. Then somehow this failure causes the failure of the building columns maybe a minute after the plaza slab failure.

More news...

https://www.cnn.com/2021/06/30/politics/nist-feder...

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

-Dik

Quote (Forensic74)

I see a lot of ideas swirling around here, but suggest some of you read up on plaza drainage systems. I see so many plaza drainage system failures due to poor architectural design and/or implementation. This leads to a lot of concrete damage that works it way from the concealed surfaces outward to the visible surfaces.

In my view, you've got a plaza drainage system on an old-school reinforced flat slab system with large planters right next to the point the collapse initiated. This all points to a corrosion induced punching shear failure that took out several perimeter columns and initiated a progressive collapse.

This article from WBDG agrees:
Link

"Harsh exposure conditions from exposure, moisture, thermal effects, weathering, and traffic often reduce these systems serviceability at a rate even surpassing that of parking and bridge deck slabs"

I also found a paper showing reduction in punching shear capacity from corrosion
Link
"The test results show that the corrosion of reinforcement rebar around the column stub in flat slab causes a significant loss in punching shear capacity and affects the structural integrity by increasing crack widths."

Miami-Dade Pictometery,

https://gisweb.miamidade.gov/MDCPictometryIPA/pict...

another county aerial photo site, not the same as DB27 cited. This one has views from top and N, E, S, W oblique views back to 2007. Place marker initially shows on building to the south because it is in the way of North facing view. Top view location OK.

Quote (Torai)

Miami-Dade Pictometery

If you look at the Dec 2012–April 2013 slice, you can see the pool tile being renovated.

Hello. I'm not a structural/mechanical engineer, but I've been following this thread closely since it started.

I noticed something that may be somewhat of a clue, on one of the real estate listings on Apartments.com from a few months ago. Link

Specifically, there are some pictures taken of the pool deck area. (See pictures 18 & 19 from the top on the above link). Right next to one of the planters, near/above parking spot 78, I see a temporary barricade (see below). What kind of damage was that barricade covering? The watermark on these pictures seems to imply that they were taken around November 2020.

Quote (spsalso)

I suggested some time earlier that the alarm that should have been transmitted to the fire department would have a time stamp. This would then indicate the time for the pool deck collapse.

No survivors have mentioned hearing a fire alarm, have they? Edit 29 of the long Reddit post mentions that there were no flow sensors for the garage level in the plans.

Also on the topic of the water pipe, the plans show that the generator room / fire pump / domestic water pumps were located directly above that entrance. There also is some mention on the upcoming renovation plans of a generator replacement and there is mention of foundation work to be done (but I didn't see any details) to be done to support the new generator. (presumably not started yet?)

replying to nononononono:

Thank you for the contact information.

I am not in a position to build the timeline that I describe. That will be for the government officials who have/need subpoena power.

I was merely pointing out that a timeline of this event will be most interesting. This because there does seem to be a time lag between the collapse of the pool deck and the collapse of the building.

It is natural to think of a structural collapse as being a smooth continuous event that occurs over a short time.

Yet here we see comments suggesting "several minutes" between the first failure and some succeeding failures.

A timeline could describe these delays of failure. And I assure you the reasons for those delays, if they DID happen, will be very interesting.


spsalso

Quote (Roga50)

Checking the aerials around that date, it looks like there may actually be a hole in the slab at that location.

re: pellucidar's post

buhzillions of dollars to put in a sprinkler system, and no flow sensors to send a fire alarm.

I have indeed led a sheltered life.


spsalso

Added 2-Jul: image source is Miami Dade Pictometry top view:
https://gisweb.miamidade.gov/MDCPictometryIPA/pict...
Original:
Ref the temporary barricade cited by Roga50 1-Jul-21 3:45; a square feature, a black feature and changes (damage?) to the planter border appears adjacent to one of the planters in image of 16-Jan-21

vs no such features appear in the earlier image taken 7-Jan-20 below

My parents had a small fire in a lot not far from them. The fire department pulled the water main pressure down and triggers the alarms on adjacent buildings.

If the drawings are correct. That looks like the location of the test probe.

The “curb” like feature between the planter boxes looks chewed up in the Jan-21 picture, it looked fine in Jan-20.

I found this photo of the North Tower pool area. The pavers appear to be the original “keystone” pavers specified on the original finish schedule. Note the lower elevation of the pavers relative to the edge of the pool, then compare to the present day South Tower pavers which were flush with the pool edge. Combined with the test probe callout, I think it may be that the South Tower slab had perhaps double the superimposed dead load that the North Tower has.

North:


South:


The other aspect that jumped out at me is that the waterproofing layer in the test probe was found ABOVE the original paver layer. That suggests waterproofing was added decades after construction, as part of the new paver renovation.

In regards to the columns in or adjacent to the planters, does anyone know how the corrosive nature of fertilizers compares to that of salt water? I know both are bad, but I don't know which is worse.

It seems likely that fertilizers would have been used in the planters to some extent over the years, and it could have accelerated the degradation of the steel and concrete in the columns.

"Looked at south/west planter with manager. Planter has structure crack and would need extensive repair manager wants to patch at this time".

permit -02 pg36/178, 09-12-02 (from IEGeezer's links)

This is during major repairs, no change to scope by the Board. Yup, engineers have none of the authority yet all of the responsibility.

Revised theory after reading this ENR article. The cantilever of roof 2 where roof work was taking place failed and fell into the pool deck slab. Debris also hit the northwest side of the large column in the portion of the building remaining closest to the pool - this column being hit by something (drunk driver thought in the article) is noted in the link below. This in turn caused the pool deck slab to fall (seen in the TikTok.) Then this failure caused the two columns at x611 to fail.

Rolls of roofing paper are still on the remaining building roof. The roof and parapet from roof 2 appear to be near the bottom of the pile under tho column.

The only part I'm not sure of is why the crack in 611 would be starting from the ceiling.

Link

Regarding the sprinkler/alarm questions that others have raised: one escapee (presumably from the portion of the building that remained standing) did report hearing alarms, but only after the rest of the building had collapsed.

https://www.washingtonpost.com/nation/2021/06/26/c...

Quote (Washington Post)

Inside the tower, on the fifth floor, Esther Gorfinkel heard something and felt the shaking. Bad weather, she thought. In storm-prone South Florida, shaking didn’t necessarily mean crisis. Then Gorfinkel — at 88, an original resident of Champlain Towers — heard an announcement on the building intercom, first in English, then in Spanish: Evacuate now.

The type of alarm system installed in this building would have used loudspeakers and a pre-recorded evacuation message rather than horns, so this does seem to indicate that the alarm system activated at some point during the collapse, although I have not found any other evidence besides this article. As for why it didn't activate during what appears to be the "initial" collapse (the parking area in the TikTok video), my first thoughts would be that perhaps initiating-circuit wiring between a waterflow sensor and the control panel was damaged during the parking area collapse, or that there was a significant delay in response time from the apparent distance to the nearest waterflow sensor combined with the standard up-to-90-second delay built into the sensor to avoid false alarms from pressure fluctuations.

Quote (smaarch)

The failure of this building is an engineering problem - pure and simple.

Found this earlier up in the thread.

I wonder how much money has been paid to realtors in the last 40 years to initially sell, and the resell, units in this building, versus how much money was paid for design, inspection, and maintenance - and how much money was paid to the people who had to place the rebar and pour the concrete.

I think we all know where the money is and if you think failures like this are solely a problem of engineering then I think that's a joke.

South Florida has a LOT of work to do...

Link

As for the fire alarms, some of the video shortly after the collapse showed fire alarm strobes going off throughout the remaining standing building. (for instance, there was one in the penthouse passageway that I noticed). No idea if that started before or after the collapse though.

I keep being struck by the collapse of the above ground parking area.

The slab at that point changes from being attached to the main building columns to the parking garage columns, which are at a wider spacing than the building columns.

ON top of that you have some big heavy planters. This looks like a good place for the initial collapse to start as there is a gap in the planters for access.

Does anyone have an original plan for the top parking area for that surface parking? That's where your bigger heavier vehicles comes into play as well.

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

Quote (LittleInch)

Does anyone have an original plan for the top parking area for that surface parking? That's where your bigger heavier vehicles comes into play as well.

In the big 1979 plans PDF, page 3 shows the spaces on the site plan, or page 15 on the landscaping plan. The basement and lobby/first framing plans give the structural details, I think. It's the same 8 spaces on the collapsed area. Planters are pretty much the same, from a quick glance. The south side is mostly constrained by columns being at 2 car widths, so spacing can't really have changed over the years.

It's certainly something to look at, if the structural design for it was for up to 4000 lb cars, and someone has been driving a 10000 lb construction / service truck on it (for example). It has limited height, but it's still a plausible scenario to look at with the construction activities that were ongoing.

https://www.dropbox.com/s/ljbto9uihe4nfk2/corrosio...

I'm curious if/how the insurance company for the building is going to try to get out of paying..
I imagine since is it is a condo there should be a global policy for all the units and a separate policy that covers the homeowners association's actions.
I can see one suing the other for negligence.

relevant video to the landscaping/planter discussion?

NEW: An attorney representing one of the #SurfsideCollapse survivors says she took this video in August of 2018, showing leaks by her car in the building’s underground garage.
https://twitter.com/BojorquezCBS/status/1410327434...

Link

https://www.dailymail.co.uk/news/article-9743079/V...

Clear version of tiktok video. Rubble can be seen. Another video shows immediate aftermath.

OK, those plans make interesting reading.

The bit that I'm looking at is the change in column spacing and size from the columns under the building to the pool area.

The spacing changes from 23 feet in a NS direction to 29 feet and smaller columns. The rest of the patio deck is 19 feet spacing and all you have on top is scattered people, not 2-3 tonnes of motor vehicle.

At the same time the EW spacing changes from 20 ft to 23 feet.

Then critically and only in this location, the pool deck is being used as a car park with added planters located over them.
So below the car park spaces on the ground level are in red and the planters are in green.

So is this enough to make this (the blue bit) the most highly stressed bit of pool deck and hence most likely to fail first?
There i one drawing showing a beam which looks to be in that location but no evidence in the collapse photos.

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

From reports coming out it sounds like this building in particular had a dysfunctional set of homeowners. A couple of questions for Florida residents:

1) Are there any safeguards (i.e. laws) in place to prevent some condo owners from stonewalling paying for repairs to the common building until after they sell/flip their individual units? If not I can imagine it would be quite a common practice. Simply sell, move to another building, wait until large maintenance assessments are projected, sell and start the process again. There was mention earlier of a recent buyer of a unit in this building who knew nothing of the 2018 report. Did this buyer also know nothing of the impending maintenance assessment, or is this more of a buyer not doing the proper homework?

2) FL has something called Homestead Laws. I'll probably butcher this, but from what I gather these laws shield the property an individual owns and calls home from creditors. Do these laws also apply to condos? If condos do fall into this category, could these laws inadvertently create a culture of impunity w.r.t. individual owners not wanting to contribute to the common good of the building? I really don't know how condo assoc. and condo boards work in this state or any other, so this question could be way off base.

@Retiredat46

I don't have a clear comparison on saltwater vs fertilizer corrosion but here are some thoughts... Corrosion is an electrochemical process that needs the presence of an electrolyte for ions to flow and the corrosion process to continue. Unfortunately, saltwater is an excellent electrolyte. Chlorides also will limit the protection to the reinforcing steel provided by the alkaline environment of the concrete.

As for fertilizers, they are possibly introducing chlorides as well. But some fertilizers lower the pH of the soil as do some types of mulch. A more acidic environment that is constantly moist would seemingly be more aggressive for rebar corrosion than just salt spray alone.

I wonder if these planters were lined?

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

Looking at the photos from Littleinch post of 1 Jul 21 08:39 there may be a design shortcoming in the apron ground floor slab.

Outside it is where the swimming pool is located. Nearer to the building it is the parking area just outside the building at the ground floor. The pool side section had almost no load except swimmers using the pool. The parking section has to take the vehicular load.

The majority of this ground floor apron slab seems to have fallen bodily onto the first floor below ground. That may be due to the debris of the collapsed building forcing the whole slab to sink as a consequential effect as the pool section had no reason to deflect on its own with little or no live load.

The alarming feature is the slab failed at almost every column position by punching shear as though there was no structural connection between the columns and the slab. This is certainly the impression I got from the larger columns that are still supporting the building. The pool portion of the slab might have the connection structurally broken off at the top. Thus the slab was relatively strong in design but its connections with the columns appearto be structurally substandard to fail in this manner.

Here is a comparison between before and after the collapse. "Before" is from the current Google Map. The white paint on the columns I believe signifies the lower level.

Planters are often lined (here in houston, tx) and fail like every 1-2 decades or so- which then facilitates replacement or removal of the planters. At least in renovation/repair projects Ive been involved in.

Can't help but wonder if the future deck slab renovation contractors dodged a bullet here. Would they have realized how precarious a state this structure was in and shored up the structure sufficiently?

Although it seems likely the jolt and bending forces added to the main columns as the slabs collapsed was what precipitated their failure, isn't it possible this entire deck superstructure was providing stability, framing to the critical columns?

The search-and-rescue efforts have been suspended as of 2 am due to concerns that the remaining structure is unstable and may collapse.

LittleInch (Petroleum),

An earlier photo in the Part I of this thread


Shows the pool area slab has partly sunk relatively to the pool which appears to be relatively stable with water still inside. Thus the weight of the pool triggering the collapse will need new evidence able to explain the above photo. Remember the same slab outside the pool has sunk more but it has virtually no live load.

RE: Column in Planter and Planters above Reinforced Concrete, in General

Quote (Retiredat46)

In regards to the columns in or adjacent to the planters, does anyone know how the corrosive nature of fertilizers compares to that of salt water? I know both are bad, but I don't know which is worse.

It seems likely that fertilizers would have been used in the planters to some extent over the years, and it could have accelerated the degradation of the steel and concrete in the columns.

Adding to bradw1128's comment about corrosion and fertilizers that lower pH, you can expect that the landscape maintenance company would apply the type of fertilizer that will provide optimum pH for growing palm trees. (The planters had palm trees from at least 2005 to 2018, when the plant scheme underwent a major revision.) I found this, "Palm trees grow best in a moderately acid to slightly alkaline soil ranging between 5.5 to 7.5 on the pH scale. Most average garden soils fall between a pH range of 6.0 to 7.0."

@TheGreenLama

(Disclaimer: I'm not a lawyer, just relaying related experience)

1) I'm in KY not FL, but a few years ago here several HOA's banded together to buy the golf course in their neighborhood after it went bankrupt. They used a special assessment spread over several years. I'm fuzzy on the details, but in that case, there were questions about if the assessment was legally enforceable on all the homeowners and the answer given was that yes it was.

I read somewhere that this building's maintenance bill was being funded upfront with a line of credit that the HOA has acquired. The homeowners would then pay down the line of credit over time with the assessment. It wasn't a case where everyone was going to write a check for $100k on day one. Surely at some point that becomes a legal obligation to the owner, current or future. Whether that actually gets disclosed to buyers before the assessment is official is a fair concern.

Units in the building were selling in the $500-700k range. IMO, $100k proportional to property value is not out of line for what you might spend on a major renovation of any property this age. For example, for a typical $200k house, a proportional amount is $30-40k which is a lot but not obscene for renovating a 40-year-old house with some deferred maintenance.

2) From what I remember based on a few friends who have homes in Florida, yes condos qualify for the homestead exemption. There are limits to value (edit: wrong, I Googled it) and you have to live there a certain amount of time (~3 years) and use it as your primary residence. Vacation homes and rental properties don't count. How this plays out in HOA politics, I could only guess.

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

Quote (saikee119)

Shows the pool area slab has partly sunk relatively to the pool which appears to be relatively stable with water still inside. Thus the weight of the pool triggering the collapse will need new evidence able to explain the above photo. Remember the same slab outside the pool has sunk more but it has virtually no live load.

The pool is actually supported by 21 piles and has full height exterior concrete walls. It was not adding any weight to the nearby structure, but contrarily, it was providing support to the column-slab connections in close proximity.

Quote (saikee119)

I don't believe anyone here has theorized that the weight of the swimming pool itself had anything to do with anything. The pool reached the foundation so that it's standing is not a surprise. Perhaps you meant the deck?

I wonder how this tragedy will influence engineers and engineering firms who are asked to evaluate buildings for the 40 year recertification process? I also wonder how this will affect the residents of current condos in south Florida? I imagine there are a lot of very worried people right now.

More on the concerns that led to the halt of searching overnight:

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

Miami-Dade Fire Chief Alan Cominsky said engineers raised several concerns with structural issues of the building. Mainly, they documented 6 to 12 inches of movement in a large column that may damage a super column in the garage. There has also been “slight movement” in a concrete slab on the south side of the building that “could cause additional failure of the building.”

He said there has also been movement in the debris pile.

Florida Gov. Ron DeSantis, speaking at Thursday’s briefing, said “obviously last night there were issues with the remaining structure” of the Champlain Towers South Condo, but added that state engineers were helping Miami-Dade Fire Rescue get “different options on how to handle this.”

“Obviously we believe that continuing searching is something that’s very important,” DeSantis said.

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

"Possible Failure Point Emerges in Miami-Area Building Collapse" https://www-nytimes-com.cdn.ampproject.org/v/s/www...

NY Times article agrees with the discussion here. Has some good graphics.

"The National Institute of Standards and Technology, a federal agency, was sending scientists and engineers to do a preliminary review, hoping to identify and preserve materials that might help understand the collapse. Officials said they expected a number of local, state and federal agencies also to be involved in the inquiry, though it was not clear which agency would lead the effort"

I hope that becomes clear very soon.

And to make matters worse a tropical storm is expected in the area by Tues.

Quote (LittleInch (Petroleum)1 Jul 21 14:02

The bit that I'm looking at is the change in column spacing and size from the columns under the building to the pool area)

I like this theory. There is also a 1' step in the slab in this area.

Quote:

1) Are there any safeguards (i.e. laws) in place to prevent some condo owners from stonewalling paying for repairs to the common building until after they sell/flip their individual units? If not I can imagine it would be quite a common practice. Simply sell, move to another building, wait until large maintenance assessments are projected, sell and start the process again. There was mention earlier of a recent buyer of a unit in this building who knew nothing of the 2018 report. Did this buyer also know nothing of the impending maintenance assessment, or is this more of a buyer not doing the proper homework?

In the WSVN "Help me Howard" link I posted above, he does kind of talk about that. If the homeowner refuses to pay, the condo board can foreclose on their unit. But that probably does take considerable time. And then, of course, the unit would have to be sold to someone else willing to pay the assessment.

(for those not from Florida, "Howard" in the video was the head of the Broward County public defender office for many years. Broward County is just north of the location of the collapse.

What are the chances the Florida officials will decide to bring down the standing portion of the building with a controlled demolition rather than take a chance that it will come down on its own during the approaching tropical storm? It's undoubtedly compromised, and reducing the risk of damage to nearby buildings may outweigh other considerations.

I doubt there's enough time to shore up the building, but there may be time to arrange a controlled demolition. It's going to be a tough call to cancel the paused search and rescue effort, though.

Quote (Retiredat46)

It's going to be a tough call to cancel the paused search and rescue effort, though.

Maybe someone who has worked on an urban search and rescue task force could speak to this? From what I can gather, these teams are equipped to be deployed for around 10 days. At some point, the operation ceases to be rescue-focused and becomes recovery-focused. That's got to be a hard call for someone to make but it will happen eventually. When it does, the calculus changes a lot in exposing anyone on site to the risk of further collapse.

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

My reasoning is simply to try and put together the eye witness stories who all talk about the pool areas seeming to subside with what other evidence we have.

Now maybe part of the building went first and then the pool deck area and then the building or maybe the other way around. But I just thought it is at least worth considering as it seems to be a weak point and could be the start point of the whole collapse. There is also talk about the impact of the building work on the condo to the south and the effect on the whole thing of that sheet pile wall which went in a few years ago only 5m or so the south of the exterior wall.

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

If they do decide to bring the building down soon, I hope and expect them to gather evidence first. If necessary, one of those robot thingys that are all the rage could get sent in. Well, not maybe into the debris pile, but into parts of the garage that aren't fully collapsed.

On a slightly different note, it's been a week since this happened, and I haven't noticed the name of the company that built this. Did I miss it?


spsalso

Quote (Retiredat46)

What are the chances the Florida officials will decide to bring down the standing portion of the building with a controlled demolition .

No idea, but I wonder if they would consider bringing the building down to the west and into the street, so as to preserve the working area to the east? The only thing to the west is Collins ave and a park/tennis courts.

Here's the info from: https://en.wikipedia.org/wiki/Surfside_condominium...

"William M. Friedman & Associates Architects, Inc., was the architect for the project's 1979 contract drawings.[27][28] Breiterman Jurado & Associates, consulting engineers, were responsible for engineering aspects and the 1979 contract drawings, with Brieterman and associates covering structural items and Jurado and associates covering electrical and mechanical.[27][28] Nattel Construction, Inc., of Miami Beach was the general contractor for the construction of all three buildings.[7]"

According to: https://www.corporationwiki.com/Florida/Miami-Beac...

"Nattel Construction, Inc. filed as a Domestic for Profit Corporation in the State of Florida and is NO LONGER ACTIVE. This corporate entity was filed approximately forty-two years ago on Tuesday, June 19, 1979 , according to public records filed with Florida Department of State."


Bringing the building down in the street might seriously damage some critical underground infrastructure.

Here is an excellent video of the collapse area. You can see the punch thru of the columns .It looks the Patio/slab garage roof hit the building columns.
https://www.foxnews.com/us/miami-condo-collapse-su...
Those buildings survived Hurricane Andrew. But couldn't survive foundation and torsion problems. Soft Story.

Many of us agree that the "surveillance video" starts after the collapse was initiated.
I hope that the grand jury will subpoena the original video.
Also, I hope they will subpoena any video from all surrounding buildings.
The literature from Champlain Tower South state that they have video surveillance, this should have survived (I hope.)

SF Charlie
Eng-Tips.com Forum Policies

I think the rubble at the end of the ramp to the underground parking area may be critical in determining the trigger event. It's probably going to be stay pretty much where it is now regardless of how the standing part comes down, and it may be possible to determine where it came from.

I have found with 30 years of inspection experience that the ACI minimum concrete cover is severely deficient. And on top of the space requirement there is a tolerance to that dimension allowed.In field tolerance on any thing are lucky to be 3/4" especially since concrete is not smooth and some aggregates are at the surface not perfectly flat like a crystal.

Extensive 4K aerial drone footage from various angles. Set the player settings to 4K. You can zoom in quite well to areas of interest.

https://www.youtube.com/watch?v=GyrvMi-4QE4&t=...

From the drone footage I linked, you can see a large part of the 111 planters still fairly intact.

It's interesting how large parts of the deck structure remained elevated despite the collapse. It almost seems as though the west pool deck and upper level parking area collapsed further than the deck directly beneath the collapsed building.

We know that Sara Nir saw the upper level south parking collapse prior to the full collapse. The Stratton account as described by her husband was of the "pool caving in". Clearly she didn't mean the pool itself, but this area west of the pool is more suited to the description. She had a good view of the pool and upper parking, not so much the 111 planters.

For higher resolution views and different perspective, see the video itself.

It's become "relatively" clear--based on witness testimony--that the portion of the patio slab, which also served as parking and was visible from the lobby, collapsed prior to the main building collapse. It's still unclear if this area came down prior to other sections of the patio deck, or was brought down by adjacent spans collapsing. But again, it wasn't brought down by the building.

Elsewhere in the thread it has been suggested that the unzipping of the bottom rebar seen here is not unimaginable in high impact collapse events. But here, for this section of slab, we do not have a high impact collapse event--unless you consider a span in the the adjacent bay failing and falling 10 ft. To me this suggests that something is seriously wrong with the ability of the bottom reinforcement to develop (causes have been discussed elsewhere). I would posit that there may exist these rebar development deficiencies building-wide, as similar unzipping instances can be seen in other photos.

Re video from security cameras on the property: the plans show that the security office seems to be next to the mail room, next to the elevators in the part of the building that is still standing. So even if all video recording is on-prem, the servers would most likely be in that room and have survived. There also seems to be slight mention [I could be wrong--forget where I saw it in the plans] of a "telemetry computer" in the office between the trash/electrical room and the front desk (also in an area still standing)? Of course, that was back in the 80's so no idea what that really was or what it would capture. At a previous employer of mine down here, I worked in a building from the same era and our telemetry computer was mostly related to the HVAC system and smoke fans/vents/fire alarm system.

Hopefully someone with jurisdiction has the foresight to check for the CCTV system before they demolish or further disturb the still standing building.

Roga50, I watched that video interview and from that it sounded fairly clear cut in that the board had absolute authority. But in the Washington Post article I posted earlier it sounded like condo owners had tremendous ability to foot drag and play politics. So I'm still a bit confused.
https://www.washingtonpost.com/investigations/majo...

Maybe the real cause... deteriorated until it broke...

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

-Dik

Seismograph readings from buildings under construction in the area might help in understanding the sequence of events.

Quote:

Roga50, I watched that video interview and from that it sounded fairly clear cut in that the board had absolute authority. But in the Washington Post article I posted earlier it sounded like condo owners had tremendous ability to foot drag and play politics. So I'm still a bit confused.

There's a reason why we call them "condo commandos" down here :)

A few thoughts after reading through the threads:

1. It would seem "eyeball" inspections are not enough to determine whether or not a building is in grave structural danger especially since all components are not visible, including the foundation elements. Even if an inspector or engineer felt collapse was immanent, they would still face the reality of condemning a building that is considered prime real estate in the middle of its useful life. That is far different than condemning an abandoned building. The backlash of peers, officials, owners, agents, and politicians could cost you your career. We are always told "buildings don't just fall down in America". So who wants to be the first to say "Well this one is about too!"

A solution, which is already being used on site, could be to monitor buildings using modern day surveying equipment. Every new building could be surveyed upon completion and every 10 years afterward. The deflections and loading conditions could be recorded and cataloged for comparison throughout the structures life. Old buildings could be evaluated the same way only the task would be more difficult with no starting point to compare too, however still useful. This would provide scientific evidence if there were a problem and would protect inspectors and engineers from having to make judgement calls. Given the 3D laser technology today, this is more achievable than ever.

2. A building made of thin two-way flate plate floors on columns using frame action and minimal shear walls to resist shear is not a redundant or robust structure. They are used for cost savings, speed of construction, and floor height. The design is governed by punching shear and when one goes where does it stop. Whether the slab punches first (dropping onto the floor below and doubling the unbraced length of the column) or a column buckles or is damaged (doubling the span of the slab and pulling on all of the adjacent columns), it seems progressive failure is inherent in this type of construction until it runs into a wall or change in framing that provides support.

3. The design load requirements by ASCE should be examined thoroughly after this for condos or commercial space over parking garages. As of now the loads are 40 psf for residential spaces, 100 psf for lobbies, corridors, and egress paths, and 40 psf for parking garages? I understand that parking garages have been value engineered to nothing and that 40 psf is pretty close to actual loading and that no residence is ever likely to see anywhere near 40 psf...even if they have tile over tile over tile floors, but the end result is the basement and first floor levels being pushed to their limits on a routine basis (not including dynamic loading and vibration, which are ignored) while the upper floors hardly ever see 20psf. Then try explaining to someone how the pool deck and lobbies should be the most robust slabs designed for 100psf when they are empty most of the time and yet cars are packed into the garage like sardines in the same picture...

A solution could be to increase the loading requirements for parking garages to 100psf located under residential/commercial spaces, especially towers (with no LL reduction). This would result in thicker slabs, more reinforcement, bigger columnns, and more foundation elements such as pilings. In addition more concrete cover could be specified to protect against damage from vehicles (Murphy's Law?)

4. Structures located in corrosive environments should be designed for corrosive environments.

5. That D-ring detail is scary as hell! Some poor crew is supposed to dangle themselves off the side of this building hanging by horizontally epoxied bolts into a 40 year old column made of questionable concrete? Count me out. Haven't there been studies showing this is done improperly 9 out of 10 times? Aren't horizontal and overhead applications only supposed to be done by a certified technician? Why not clamp a steel bracket around the column? Something that can be inspected for safety.

TheGreenLama (Structural),

Your middle photo, with rescuer and dogs standing outside, brings a chill down my spine.

You called the rebar unzipped. To me the whole span' every reinforcment has debonded from the span. I have been wondering why the roof has so many irregular lines which are now proved to be the grooves in the concrete when the reinforcement was originally forcibly removed from the slab.

The rescuer and the two dogs were standing on the same ground floor slab which has since dropped on a lower floor like a pancake. The dropped and severed section has concrete and rebar which is hidden but in the next span, with ceiling and water, the rebar that was forcibly pulled out from the slab can be seen without any concrete attached above a pond of water. There is a serious construction defect here suggesting the concrete and rebar were not bonded structurally to resist load but separated in a clean cut manner. It is a miracle the span of this two-way slab that didn't drop, still hanging with grooves on its underside, now has all rebar in one direction removed, at least on its bottom side.

Whoever is doing investigation has to cut cores from the remaining concrete to verify its commpressive strength, cement content, chloride contend, density, ultra-sonic speed and water absorption at least. That concrete quality is highly suspicious to me.

I'm very impressed by the effort and thought many have put into their comments here.
I was a bit shocked by the clean rebar at first, but I think it may be a red herring. In every floor or wall there will be one direction of bars which are not contained within the reinforced mass. The clean bars only had chairs and cover concrete under them. As the adjacent floor pulls downward on the bars it will tend to "unzip" them from the concrete. In slow motion this would cause a bit of cover to break off, the exposed portion of bar would bend dramatically, and then the next bit of cover would break off. I think the fast but sequential bending of short lengths of rebar may pop all of the adhered concrete off. The clean bars have a pronounced curve - even those not draped over other items. I'm not sure where the top bars are in all this though. Seems they should have prevented the behavior I'm describing.

Quote (retiredat46)

What are the chances the Florida officials will decide to bring down the standing portion of the building with a controlled demolition rather than take a chance that it will come down on its own during the approaching tropical storm?

and bradw1128,
The city can evacuate the area and close Collins Ave if the tropical storm will bring > 30 mph winds. The building should be brought down, and it should be brought down onto the plaza and pool area. The area is mostly open and available and is already damaged (understatement). Don't damage Collins Ave and the infrastructure underneath. But first the city has to end Search and Rescue and begin Recovery.

Quote (sfcharlie)

Many of us agree that the "surveillance video" starts after the collapse was initiated.
I hope that the grand jury will subpoena the original video.

The surveillance video from the next door Blue and Green building was probably started on the motion from the first slab falling. There may not be anything more on "the original video".

Quote (chiefinspectorJ)

I have found with 30 years of inspection experience that the ACI minimum concrete cover is severely deficient.

I'm interested in your thoughts. What would you propose for rebar concrete cover when poured against forms and when poured against existing earth? Should the "against earth" requirements differ for different types of soil?

Quote (LittleInch )

So is this enough to make this (the blue bit) the most highly stressed bit of pool deck and hence most likely to fail first?
There i one drawing showing a beam which looks to be in that location but no evidence in the collapse photos.

I don't think it is a coincidence that the beam was removed on S5 Rev.1 Dated 1-17-80. **Corrected below, this was not the most current S5.**

It's also interesting that many of the columns remain, but I don't see evidence that K/14.1 is still standing (edit: visible in photos, but I would be interested is a closeup). If the beam at the slab drop (K/12.1 to K/16) failed at mid-span due to the missing beam, it would create a sudden eccentric load to column K/14.1, possibly causing it's collapse.

One sign that the beam at the slab drop was failing is that there was visible ponding at the location of the added slab drain on the pool deck.

Quote (Awestruc)

3. The design load requirements by ASCE should be examined thoroughly after this for condos or commercial space over parking garages.

Good post. First off, "tile over tile over tile floors" should not be allowed by the rules of the building, and, believe me, the occupants know when work is going on and they will tell the board if you are having renovations done without permission of the building's management. Remove tile before installing new tile; simple as that.

With only one layer of flooring, I think 40 psf is quite adequate for residential buildings. I would estimate that my 36 ft x 22 ft living room contains furntiture that produces less than 5 psf of loading. Add 10 psf for tile and grout. Maybe a solution is to further limit the Live Load Reductions allowed (which would have same effect as increasing the 40 psf loading) for buildings over 5 floors.

Codes have been revised since 1981 to provide better slab to column connections. This was mentioned briefly on the original thread.

I'm sure some masters thesis could investigate parking garages in actual use vs design loads; this may have already been done. Maybe someone will do a search.

The enhanced TikTok video (from the user above) appears to show the bushes from the 111 planter among the initial debris in the parking garage:

As a professional engineer across the pond it is my experience that the site concrete seldom holds up well against the design standard.

The Morabito Consultant report identified a defective pool deck above the garage due to the waterproofing no longer effective. Its recommendation, quoted "extremely expensive", was to remove the top paving, bedding sand layer, the mortar screed (which the author of the opinion it had been laid flat and didn't drain to cause the waterproofing layer failure) and the waterproofing to expose the reinforced concrete ceiling slab of the underground garage. His method was to redo everything on top of the garage roof celing. While this appears peritent as the existing structure was known to leak water my problem is that the pool deck was the only part of the building structure that didn't collapse! as indicated by the site photo.


When concrete is constructed soundly it is reasonably impervious to water penetration. Anyone who has laid or used standard size, say 3' by 2' or 2' by 2', paving precast slab can testify it is not easy to pass water through its 2" thickness. A precast paving slab is made from cement mortar in a factory with adequate or superior compaction. I am not here to argue if the concrete is bad or good in the collapsed structure but it must be an interest to everyone here if we can cut some cores from the remaining structure or even select undamaged parts from the debris, to find out its density, water sbsorption, ultra sound speed and ultimately it as-cast compressive strength. In my experience a poor concrete will have to be lighter or less dense, with higher water absorption, low ultra sound speed (steel is about 6km/s, good concrete is about 4.5 to 4km/s) and insitu strength significantly lower than the specified strength. ACI 318 even allows a generous margin below strength before an engineer can condemn the concrete structurally inadequate.

In fact in every concrete report I delivered in my career I wouldn't address its structural inegrity unless I could verify its as-cast compressive strength. When rebar has been corroded I always insist on chemical tests on concrete to establish its chloride content. Thus I never put my personal opinion in my reports because everything has to be based on facts and test results which are verifiable by a third party.

The three other submissions to the local government agency for repairs have been mainly for the balcony structures which are not issues in this collpase. Many repairs, like resin injections on cracks and cosmetic repairs have been executed on this building according to Marabito report but many have failed or deteriorated. Thus the root cause of the deterioration has not been identified or the structure has been assume to deteriorate like a normal RC structure that does not warrant an in-depth investigation.

We still lack key evidence to know the root cause of this collapse.

Nattel Construction, Inc. filed as a Domestic for Profit Corporation in the State of Florida and is NO LONGER ACTIVE. This corporate entity was filed approximately forty-two years ago on Tuesday, June 19, 1979 , according to public records filed with Florida Department of State.

I don't know if this was a rebith of an experienced bankrupt builder, an inexperienced start up that somehow landed 3 new 12 story buildings, or a mafia shell company.

Quote (aggualaqisaaq (Nuclear) 1 Jul 21 21:57)

... appears to show the bushes from the 111 planter among the initial debris in the parking garage

I believe you're right! Adding a divide layer using the bluish colour of the white "column 27" reveals the greenery (and also further brightens up the scene).

ChiefInspectorJ (Specifier/Regulator)1 Jul 21 17:36
I have found with 30 years of inspection experience that the ACI minimum concrete cover is severely deficient. And on top of the space requirement there is a tolerance to that dimension allowed.In field tolerance on any thing are lucky to be 3/4" especially since concrete is not smooth and some aggregates are at the surface not perfectly flat like a crysta

I sure hope that 3/4" was at the corner lapped section of a minor column and not above the lap in the midsection of a 8" shear wall. I'am not being critical just trying to put into context what the allowable tolerances for field construction are. Double and triple mat transfer beams are the worst thing I personally had the displeasure of keeping the concreate in tolerance.

In my experience an Architect calls out the basic structure, and sets his interior layout on those dimensions, which results in the SE guys feeling constrained to make everything fit.

Nattel Construction, Inc. appears to have been formed by the developer of the project (Nathan Reiber) for the purpose of building it.


spsalso

It seems to me that the pool level patio deck failed first. From that point on, the deck is no longer restraining the columns which in turn become excessively slender and buckle resulting in the catastrophic and total failure we have seen.

Why the deck collapsed initially - looks like corrosion of rebar as many others above have alluded to already.

In the event of such a deck failure, I don’t think even the current disproportionate collapse requirements are sufficient.

New article today from the Miami Herald on Nathan Reiber, the beginnings of this project and all the various entities, people involved. Open in Incognito to get around paywall.

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

Not sure if it's been clarified already, but there was some discussion about how Cassie Stratton, the resident who was on the phone with her husband when the building collapsed, was quoted as saying she saw the "pool" collapse.

According to this article, she referred to the "pool deck" collapsing.

Quote:

Cassie told him that the building was shaking and the pool deck had collapsed.

There is no direct quote attributable to anyone, but I'd guess it's either based on an interview with the 911 dispatcher who spoke to the husband, or from the husband himself. I suppose it could also be editorial choice by the author.

Rebar clearance ACI 318
I would double the allowable clearance without the tolerances. That is because the plans you draw are NEVER done exactly or sometimes close to the drawing. Lets call it a factor of safety that is calced in almost every other structural component.
And special cover required for special uses such as possible damage.
Also when you spec: 8" oc the field guys start at 8" not zero!!
Especially on nailing patterns.

In the field alot of these measurements are not taken from the outside of the bar.
Bars are not always straight. And neither is the structure.
CMU rebar clearances are also worrisome.
For standard C-90 plain vanilla CMU, let's see...

11.625" - face shell(1.5") - d(8.5") - 1/2 #6(0.375) - 530.1 tolerance(1") = 0.25" clear

or 11.625" - face shell(1.5") - d(8") - 1/2 #6(0.375) - 530.1 tolerance(0.5") = 1.25" clear

DB27 (Structural),

On you marked up drawing of 1 Jul 21 21:43 post you indicated a column adjacent to and outside the un-collapsed building not visible and could have possibly collapsed.


There are evidence that this column had punched through the pool deck slab just like the rest of the other adjacent 6 columns nearby. In the Morabito drawing this column lies at the border fence of the bush area.


It is shown up in this shot. You can see its top just next to the parked car.

Another photo shows it is covered by the displaced fence but at 20' c/c distance with the other two columns you can make out it is there in this photo.

Quote (DB27)

It's also interesting that many of the columns remain, but I don't see evidence that K/14.1 is still standing. If the beam at the slab drop (K/12.1 to K/16) failed at mid-span due to the missing beam, it would create a sudden eccentric load to column K/14.1, possibly causing it's collapse.

Column K-14.1 is still standing (visible between the fence and gray car):


All three of the following accounts depict initial debris coming from above:
1. Mr. Nir, Unit 111: Noises above her unit, knocking grew louder before she heard a "smash," as if a wall had collapsed in the unit above hers. She went to the lobby after hearing these noises. While with the building's security guard in the lobby, and as she complained about the noise, she said, they heard a boom. She ran toward the sound and witnessed the building's underground garage collapse. It was like something out of a movie, she said. Link
2. Ms. Monteagudo, Unit 611: She heard a strange noise and it felt like the building was moving, tried to close the sliding door to the balcony, and it wouldn't close. She then heard a crack, a line in the wall coming down from the ceiling "about two fingers wide" then it started getting wider and wider as she watched.
3. Rosie Santana’s camera, Unit 711: White, hail-like debris coming from above and heard pelting her living room, before the camera abruptly goes dark after 13 seconds. Link

Roof work was actively occurring, the building's new roof anchors were inspected by a city inspector, Jim McGuinness, on June 23, 2021.

Well look here... The roof anchor permit was issued by the city on June 23, 2021 to Concrete Protection and Restoration, LLC. Link The building collapsed on June 24, 2021, at approximately 1:30AM (less than 24 hours later.) It's possible the initial work was unpermitted, I doubt they could have installed all of these roof anchors in one day. The town has not posted any other roof anchor permits I can find.

Roof anchors visible on collapsed penthouse roof:


Work was not complete as rolls of roofing paper are visible on the roof of the remaining portion of building directly adjacent to the collapse (left circle below) and improperly installed roof anchor (right circle below further discussion below):


Close up of roofing paper from drone video - note the green plastic looks similar to that seen in the garage in the tiktok video:




The penthouse roof anchors are to be on or between the columns, not on the cantilever portion of the slab (the two anchors circled are the two columns which failed first in the surveillance video):


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




Roof anchor drawings note required repairs of concrete and a slab thickness of 8" - to be verified (how exactly is a roofing contractor supposed to verify a slab thickness?):


Post roof anchor detail notes 6" slab, states anchors should not be installed on damaged concrete, slab to be xrayed, and notes 25% of anchors need to be proof load tested to 5,000 lbs.


I believe the roof anchors over the penthouse were installed incorrectly, the first bangs of construction Ms. Nir heard was pieces of the roof falling off onto the pool deck. This caused the pool deck to fail either by hitting a column in the parking area as the ENR article suggests or by overloading the slab.

Please poke holes in this...

-W

Devils advocate here. Is this the pickup truck/vehicle that struck the column and knocked down the tower?



Motive, perhaps a disgruntled unit owner angry about the special assessments they are about to face?

All of the other deck area columns punched through the slab whereas this one appears to have snapped as though taking a lateral load.


Truck to same scale as plan

I totally apologize but I really don't see any "mechanical roof anchors". To me the term infers a mechanical connection between the base-ply and the underlying substrate, and not the connection for A/C stands, flashings or caps. The term mechanically fastened roof makes me think of anchors on a foam or thin lightweight concrete over a metal deck and not a pored a RC deck.

MIStructE_IRE (Structural),

Your theory that the pool deck was the first one to fail that led to the collapse of the building may be hard to explain the following:-

(1) The external section of the pool deck, that has no building above, has dropped from ground level to the basement level. In so doing it shear-punched through at least 6 columns size of 16"x12". How could the pool deck punch through the 6 columns with such a huge vertical load when it had zero live load in the middle of the night when no one swam outside?

(2) The pool and its surrounding deck did not fall onto the basement floor. If leaking was to blame for weakening the pool deck then the leakage path would be very long for water to travel from the pool to the deck currently covered up with debris. I have assumed the entire +11'-0" level as the pool deck (in William M Friedman & Associates drawings) which is called Level 1 in Morabital drawings.

(3) The collapse was in two stages. First stage was by the inner section followed shortly by the outer section on the North end. The failure of the pool deck level had to be in a sequence or manner to reflect this two-stage movement.

Quote (Keith_1)

I totally apologize but I really don't see any "mechanical roof anchors". To me the term infers a mechanical connection between the base-ply and the underlying substrate, and not the connection for A/C stands, flashings or caps. The term mechanically fastened roof makes me think of anchors on a foam or thin lightweight concrete over a metal deck and not a pored a RC deck.

The roof anchors I'm referring to are OSHA fall-protection roof anchors.

The length of Part 02(in lines of text)is too long for me to scroll through with my browser.
Can someone start Part 3 Please.
Thanks

SF Charlie
Eng-Tips.com Forum Policies

It just gets more interesting... It's a shame that lives were lost.

"A Florida building inspector who assured residents of the collapsed tower that it was in good shape a month after being warned otherwise is having all of his previous work reviewed after being suspended from his new job.

Meanwhile, it has also been disclosed that the entire building department for the town of Surfside was under review at the time of the collapse.

Rosendo Prieto was chief building official of Surfside until November 2020. On Tuesday, he was placed on leave from his job as interim building official for C.A.P. Government Inc.

Now, city officials in Doral are planning on reviewing his previous work to make sure he didn't clear other buildings that may be dangerous."

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

-Dik

If the engineers performing the assessment weren't able to identify a need to urgently evacuate building clearly the building official wouldn't have been able to either.

His assessment of other buildings from a structural safety perspective is probably not relevant.

Quote (ChiefInspectorJ)

For some reason I can't respond directly to the poster. Only to the thread. What am I doing wrong?

(1) Click in the Edit Post box that you have been using
(2) Copy the text you want to quote
(3) Click on the little icon with the cartoon speech bubble and blue shirt
(4) Enter the user's name
(5) Click paste and the quoted text will be pasted between the two sets of brackets
(6) Click below this block of characters to write your comments

My experience is in industrial structures and mostly steel. I have seen a few failures due to corrosion but in all cases the corrosion was extensive. I keep thinking there must have been a triggering event.

What about a fire in a battery electric vehicle? Lithium Ion batteries burn at 2,000 C / 3,362 F, what if one was parked under a key transfer beam and caught fire? News reports from Saturday report a fire deep in the debris pile.

Quote (Sym P. le)

Devils advocate here. Is this the pickup truck/vehicle that struck the column and knocked down the tower?

Residents of two units were in the basement garage within the 15min preceding the collapse of the plaza level.

Two were in the elevator which recalled to the lobby upon activation of the fire alarm due to the deck collapse. They exited the building with the Nir family. The other had been moving things to a hotel for over an hour and left via different transportation than the vehicle parked a short time earlier in the basement.

Quote (saikee119)

Many repairs, like resin injections on cracks and cosmetic repairs have been executed on this building according to Marabito report but many have failed or deteriorated.

I have not read if this was permitted or not, but this is a great example why it is critical that HOAs take structural repairs seriously. They should be inspected by engineers, repair work performed by licensed contractors, and respective permits pulled. Not only will there be better records for future reference, but liability can be determined if any problems do occur.

Had the HOA inquired an engineer to examine the original damages, maybe the building could have been salvaged or monitored better before things turned out the way they did.

Quote (Keith_1)

There are absolutely no OSHA deck anchors in this structure.

Scroll up to warrenslo's post at [2 Jul 21 00:27]. warrenslo is talking about the anchors that had just been/were being installed on the roof. I believe they are window washing anchors/davits, but the 5000lb ultimate load spec'd on the detail might lead one to believe it is a fall arrest anchor. I don't know the difference between the two though (load rating of a window washing davit vs fall arrest). Never designed one.

Quote (warrenslo)

I believe the roof anchors over the penthouse were installed incorrectly, the first bangs of construction Ms. Nir heard was pieces of the roof falling off onto the pool deck. This caused the pool deck to fail either by hitting a column in the parking area as the ENR article suggests or by overloading the slab.

That is interesting. I still have a hard time believing that hammerdrilling 4 ~3/4" diameter holes in the roof slab would cause the balcony/roof slab to collapse. Which balcony's roof are you proposing fell first? Also, I doubt a falling chunk of slab would be able to bump sideways into a column hard enough to buckle it. If the piece was large enough, and it landed directly above one of the columns under the pool deck, perhaps it could cause some manner of crushing? I think it's far more likely (if a piece of the roof fell off and landed on the pool deck slab (+11'-10")) that it would have caused a punching failure as opposed to damaging the column somehow. Part of the slab collapses > triggers domino effect as the falling slab drags down the adjacent slab (slow or fast, who knows) > etc

Quote (dold)

window washing anchors

I was wondering why there were so many "window washing anchors" when most windows can be accessed from balconies, then I went back to the original thread and followed the link to the anchor drawings and found out that they anchors will be used for window washing AND balcony repair. Made a little more sense after I saw that. The anchors will support a platform and some materials and tools, as well as the worker(s).

NOLAscience:
My comment regarding 3 layers of tile was tongue in cheek.
I do think that 40 psf is more than adequate for residential floors in most cases. But with that being said, how can a parking garage have the same design load? Try explaining that to a normal person.
The point that I was trying to make is that the design service loads are disproportionate in their difference to the real day to day loads, as evidenced by the pictures. For instance, the Lobby and pool deck would be designed for 100psf but empty most of the time, residences would be designed for 40psf but in reality just couches, TVs, beds and typical 5psf stuff, plus a few layers of tile .The Parking garage would be designed for 40psf and actually loaded to almost 40 psf daily for 40 years.
That’s almost 15000 load cycles on a part of the structure that is in distress from corrosion, flooding, lack of maintenance, and no waterproofing membrane.
I’m not saying the building or garage floors were overloaded. I honestly think corrosion of steel and deterioration of concrete combined with flat plate construction with little to no shear walls are some of the main reasons it fell apart the way it did. I do think that garages should be designed for corrosion in corrosive environments. I also think the columns should be designed for impact from a vehicle, especially when playing condo Jenga for 12 floors above. Seems like that could be achieved with better concrete and more cover at the least. It will be interesting to see what they discover at the bottom of the pile and foundations.

Quote (Keith_1)

There are absolutely no OSHA deck anchors in this structure. I don't know what scares me the most is that you have absolutely no clue when such things are employed, or how they are employed.
This is a simple midrise, there are absolutely no geometric point that OSHA would require an anchor point for a complex geometry, nor is it tall enough to require a secondary anchorage.

I certainly do have a clue, I have designed many multifamily apartment/mixed use roofs with anchorage systems. They are required on buildings of approximately 5-stories or more in height now. CA is especially strict after Jerry Brown cracked down on the law not being enforced.

There weren't OSHA anchors on this structure until an unknown period shortly before collapse. They were in the process of being installed to facilitate the painting and repair of the decks and concrete walls. The permit pulled the day of the collapse was specifically for OSHA fall-protection anchors. Please see my post above for the permit info, etc.

https://www.osha.gov/sites/default/files/publications/OSHA3146.pdf

Quote (If the engineers performing the assessment weren't able to identify a need to urgently evacuate building clearly the building official wouldn't have been able to either.)

If the collapse were due to neglect over an extended period of time, that is where it gets really ugly.

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

-Dik

Quote (you have absolutely no clue when such things are employed)

Let's play nice...

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

-Dik

the problem was systemic... those little bandaids would not help, and if anything like the proposed repair were 'doomed' to failure. Putting lipstick on a pig comes to mind...

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

-Dik

Surveillance video seems to confirm top 4 floors over x11 stack fell first - this was where roof anchors were being installed above the penthouse. This roof area is under structural columns in the debris pile closest to the guest parking.

Quote (Try explaining that to a normal person.)

It's the grand piano in the corner of the living room...

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)

There weren't OSHA anchors on this structure until an unknown period shortly before collapse. They were in the process of being installed to facilitate the painting and repair of the decks and concrete walls. The permit pulled the day of the collapse was specifically for OSHA fall-protection anchors. Please see my post above for the permit info, etc.

Which anchors were replaced? They’re noted as existing in the re-cert plans, with replacement as needed after field check and necessary condition repairs to the slab performed.

Look who works for the roof anchor company. They also have an office in MD not too far from Morabito's office.

Quote (warrenslo)

Surveillance video seems to confirm top 4 floors over x11 stack fell first - this was where roof anchors were being installed above the penthouse. This roof area is under structural columns in the debris pile closest to the guest parking.

If you’re looking at the footage that’s had the beginning trimmed (the uncut version starts with a no signal white screen), key frames showing the bottom of the x11 stack between L and M falling initially are missed.

The flashes visible are the Fire Alarm Strobes illuminating.

Quote (Santos81)

Which anchors were replaced? They’re noted as existing in the re-cert plans, with replacement as needed after field check and necessary condition repairs to the slab performed.

See the 2018 Morabito Report:

Quote (awestruc)

Lobby and pool deck would be designed for 100psf but empty most of the time

I don't care much about "most of the time". The pool deck could be filled with people when the building has a fire, could have high loads when building materials are staged there; the lobby could certainly have loads of 100 psf, at least in one span. You just never know.

I still think the calculation of the actual beach condo parking garage loads would be instructive, if not for this case, maybe for the next code revisions. Garages do not get the live load reductions that residential live load gets. That probably makes the actual/design ratios closer to the same.

Quote (geotechguy1 (Civil/Environmental)1 Jul 21 07:15

I wonder how much money has been paid to realtors in the last 40 years to initially sell, and the resell, units in this building, versus how much money was paid for design, inspection, and maintenance - and how much money was paid to the people who had to place the rebar and pour the concrete.)

In my experience the Structural gets a fee of maybe 1% to 1.5% of construction cost. You can guess at the responsibility and liability.
The realtor who sells it gets 6% each time it sells. He takes pictures and writes a glamourous description then turns it over to a title company.
What the heck was I doing in engineering?

Quote (Santos81)

If you’re looking at the footage that’s had the beginning trimmed (the uncut version starts with a no signal white screen), key frames showing the bottom of the x11 stack between L and M falling initially are missed.

Here's a slightly earlier screen cap, The top 2 floors (possibly 3) are clearly missing over the x11 stack. I think they slowly fell in pieces over several minutes prior to the main collapse causing the damage in the Tik Tok video. The Penthouse and Floor 12 had large catilever balconies across the entire unit on the x11 stack. The two white flashes are either the HVAC or electrical flashes. The prior image I shared was milliseconds later and the floors with lights on hadn't moved yet however the 10th floor light goes out by then.

Quote (Warrenslo)

See the 2018 Morabito Report

Face mount, not post. The permit for the roof post replacement wasn’t processed until the afternoon of the 23rd after inspection. I doubt any were done in those few hours.

Quote (warrenslo)

Look who works for the roof anchor company.

That's the problem with having an unusual last name. If the engineer were Frank H Baker, we would not be sure if Harrison Baker at the anchor company was his son or not. But it was still probably a good idea for the anchors to be installed, as they are an OSHA requirement for the upcoming work.

What exactly is your theory, again, of how the installation of the anchors precipitated the building failure?

Forgive me if I drop out of this thread until Tuesday. I have fish to catch (weather permitting).

There seems to be a dearth of cameras with suitable optics.

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

-Dik

The anchors did not exist in this Google Maps image dated 2021.

Quote (Santos81)

The other had been moving things to a hotel for over an hour

So a resident of the building was moving a significant number of items to a hotel, just before the collapse. Why? Was the person aware of a problem?

Quote (NOLAscience)

What exactly is your theory, again, of how the installation of the anchors precipitated the building failure?

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

Quote (MarkR)

I'm sure many people were not concerned seeing water in the garage, it might have only concern them because they were getting their $500 shoes wet.

I've been meaning to get back to this comment with my own story.

I was working in a 50yo office park in a rather uninhabited area from 2011-2014. At some point in that time, the state resurfaced a highway and slightly improved its intersection with another highway. Based on the 1100 employees in our building and other large buildings nearby, I'd say at least 1000 cars a day used this intersection. Almost immediately after the new road surface was finished, I noticed that water was up to the level of the asphalt -- or even over the asphalt -- every day when I chose to take that route. It bugged me and bugged me, especially over the weeks when we had no rain at all. I finally emailed the local action news reporter and said, basically, "The state just spent our money to repair this road and it is not going to last very long with standing water up to the surface, even with no rain." He looked into it, and contacted someone. Driving to work a few weeks later, I saw crews cleaning out the drains. Water never pooled there again.

Why was I the only person out of 1000 per day that saw this as a problem? Most people have no clue about the damage that water causes when it is not expected.

Quote (warrenslo)

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

But there was no load on the anchors last Thursday. Are you saying that the installation damaged the cantilever portion of the roof? Do we even know for sure where the anchors were installed? That would be a pretty big error on part of the anchor company, as they had drawings to guide them. Did the city building inspector note any problem with the location?

Happy Independence Day, All!

Quote (Santos81)

Face mount, not post. The permit for the roof post replacement wasn’t processed until the afternoon of the 23rd after inspection. I doubt any were done in those few hours.

I'm not sure exactly what the permit was for, as there were clearly new anchor point 'posts' installed prior to the collapse. But I can tell you with certainty that plenty of work gets done without a permit. Maybe this most recent permit was an extension of a permit issued prior, or something to that effect?

Also, the 2018 report indicates there were no under-mount/face-mount suspension hooks (sketchy) installed under the roof level balcony covers. See my red highlights below from warrenslo's posts above. Yet they indicate (second pic) that existing under-mounted anchors be removed and the anchorbolts ground out 1.5 inches above the soffit. I'm confused.



\\\\\\\\

Quote (NOLAscience)

So a resident of the building was moving a significant number of items to a hotel, just before the collapse. Why? Was the person aware of a problem?

Claimed:

No power in unit on arrival at approx 10:30p - decided to go to a nearby hotel - departed approx 11:30p. Unpacked, returned to CTS at approx 12:30a to leave car, stayed for additional 20-30 min, left by scooter. Returned to site after collapse and stated “my car is in there; now it’s totaled.” Left immediately after.

Plausible, yes. Convincing, not entirely. Timeline and the claimed power outage raises red flags.

Quote (warrenslo)

All three of the following accounts depict initial debris coming from above:
1. Mr. Nir, Unit 111: Noises above her unit, knocking grew louder before she heard a "smash," as if a wall had collapsed in the unit above hers. She went to the lobby after hearing these noises. While with the building's security guard in the lobby, and as she complained about the noise, she said, they heard a boom. She ran toward the sound and witnessed the building's underground garage collapse. It was like something out of a movie, she said. Link
2. Ms. Monteagudo, Unit 611: She heard a strange noise and it felt like the building was moving, tried to close the sliding door to the balcony, and it wouldn't close. She then heard a crack, a line in the wall coming down from the ceiling "about two fingers wide" then it started getting wider and wider as she watched.
3. Rosie Santana’s camera, Unit 711: White, hail-like debris coming from above and heard pelting her living room, before the camera abruptly goes dark after 13 seconds. Link

I’m starting to wonder what your game is. You fail to show how any of these three things are indicative of or relate to debris coming off the roof.

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.
2. What does a crack in a wall on the inside of the building in a unit located in the middle of the vertical stack have to with anything falling off the roof?
3. The White, hail-like debris coming from above and heard pelting her living room, was a result of the whole building starting to collapse. You can see the huge jolt as the column starts to give 13 seconds before the whole thing comes down. That’s what woke the camera up. What does that debris from the interior wall and ceiling have anything to do with the roof?

Workers discovered extensive concrete damage and suspended a repair effort last fall at collapsed Florida condo
https://www.msn.com/en-us/news/us/workers-discover...

I apologize to the board for my inflammatory speech, in regards to the "mechanical roof anchors", and OSHA. In my personal experience I have never seen a cast tied in place "eye" for OSHA fall protection. In practice I'am more concerned about (1) the integrity of the parapet, (2) the counterweighting (3) OSHA mandated wear markers, (those colored nylon threads in a ropes for example) (4) making sure that everyone is (a) properly fitted in a harness, and (b)tied off properly. There is a point where you actually have to get on a swing stage to responsibly inspect structures such as this.

Quote (warrenslo)

Here's a slightly earlier screen cap, The top 2 floors (possibly 3) are clearly missing over the x11 stack.

Or maybe the entire visible stack of the central structure is in the process of dropping relative to the structure to the left and to the right.

To state with certainty that the top levels are "clearly missing", there needs to be a simultaneous "clear" visual indication that the levels below are still aligned with the levels to the left and to the right. But the video resolution simply isn't high enough to show that.

It would be great if that footage started ten seconds earlier than it does. The fact that it seems to start during the first moments of collapse prevents us from seeing the critical, telling moments that lead up to collapse.

You've vigorously presented your position/theory that work at the roof level precipitated the collapse in the form of large sections of the roof falling down and essentially undercutting the structure at the pool deck level, at which point there is a wholesale collapse. Duly noted. Speaking for myself, I disagree with this theory.

I dont understand the fascination with the fall arrest system(s) being installed, even if they were incorrectly installed. There are much bigger problems if a 4 bolt/2 bolt connection into a concrete structure propagates a building failure. These fall arrest systems were not loaded during the collapse. No one was attached to them. No swing stages were currently present. I really think they are a non-factor in this failure.

Here's possibly the earliest currently available public video frames of the collapse, on CBS46's channel. It's the same video of a video, but starts with the playback on a blank "No video" screen.

https://youtu.be/K6ea90YGGBg

If you watch it in slow motion, the south west quadrant of the penthouse and the penthouse corridor were clearly there, and had not fallen significantly prior to the facade. MAYBE the cantilever section of roof and parapets over the penthouse & 1211 balconies was gone (and the balconies themselves), but it's difficult to be certain, and not in any way conclusive that they fell prior to the facade and main building collapse.

I'm positive the top two levels were mostly still there at the start and fell together with the levels below them. It looks like the floor slabs initially hinged downwards along the row 4 columns and spine corridor. The penthouse corridor holds on for a second or 2, giving a relatively sharp straight line across the top for reference. I'm quite convinced that the main collapse started at IKLM9.1 at patio or basement level. It is possible that the parapet and cantilever roof section fell down onto the patio as an initiating factor, but far from conclusive that they were the smoking gun that started the entire sequence.

The main collapse has already started by the first frame. It's about as frustrating as it could be in terms of evidence for the critical moment.

Where did the video of the actual collapses come from?

Strange, that it's the only existing one to date that has been released to the public. It's clearly a cut from the original video file.

And it's been cropped right at the start of the collapse - who did that and why? Where did the video come from? private party? another building? Who provided it? etc...

Well, there is a silver lining in most stormy clouds. So far, at least, this is one tragedy that is not yet being blamed on climate change/ donald trump/Boeing QC / the deep state.


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

There is a difference between the failure of this structure and the FIU pedestrian bridge, or the Hardrock failure. In the case of the FIU pedestrian bridge failure, discrete analysis is appropriate because it was a novel and extremely complex design, in the case of the Hardrock failure it was pure ineptitude.

If you look at the present structure of discussion, in terms of pressure loads over its lifetime, it was extremely well designed and constructed. The building envelope has survived several major hurricanes. In a major Hurricane the differential wind loads are extreme, the pressure gradients in quadrants can conservable be measured at a moment of being at least +/- 100psi per quadrant.

These structures even absent a major wind loaded event are still constantly subjected to blown salt water, so yes corrosion is going to happen no matter how a structure is constructed.

So once again this is entirely a maintence issue, and once again we are a self-regulated industry, the participants in this forum are pretty diverse, and well versed in their individual specialties, and I have read through every post, and find the discourse about how to self-regulate this problem extremely encouraging.

Quote (davefitz (Mechanical)2 Jul 21 14:41)

...climate change, Trump...

Sorry sir, you are wrong.
https://www.greenmatters.com/p/miami-condo-collaps...

I don't think is was climate change that caused collapse. It was Voodoo for sure.

https://www.dailymail.co.uk/news/article-9738871/E...

Quote (jrs87)

Sorry sir, you are wrong.
https://www.greenmatters.com/p/miami-condo-collaps...

You beat me to it.

Quote (There are much bigger problems if a 4 bolt/2 bolt)

You said it... mentioned earlier that this was a 'red herring'...

My earlier post:

"Other than indicating the condition of the structure, or giving you an opportunity to do remedial work, I think the roof anchors are a bit of a 'red herring'... I cannot imagine that the addition of some 5K anchors would have any overall impact on the integrity of the structure. If that sort of load is going to cause problems, then you have a more serious problem at hand. If this had any impact on the collapse, then it was just a matter of time."

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

-Dik

Quote (that is not yet being blamed on climate change)

There is one group of scientists that have alluded to this as being a consequence... detracts from the real climate change.

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

-Dik

Quote (Kreemerz)

Where did the video of the actual collapses come from?

It appears to be from a CCTV security camera covering the back yard pool area of the new "87 Park" condo at 8701 Collins Ave. That's just me interpreting the location from the video. Beyond that, I can't say.

The Tiktok one from the north was a hotel guest woken / alerted by the crash of the pre-collapse collapse. Their name is out there somewhere.

Quote (davefitz)

Well, there is a silver lining in most stormy clouds. So far, at least, this is one tragedy that is not yet being blamed on climate change/ donald trump/Boeing QC / the deep state.

This guy sure knows how to stir the pot... by the time I'm done typing I bet there will have been 25 replies ahead of me

I recently designed some critical infrastructure buildings in Miami that were designed for sea level + storm surge in the year 2075. We are talking several feet of projected rise compared to current day. In fact the level was revised a couple times during the design process due to the accelerating nature of the rate of rise! Given the fact that below grade water intrusion was a major chronic problem at the Champlain South building, it's not unreasonable to question if sea level rise + subsidence played a role. I doubt that it did, but it's still a reasonable aspect to consider.

Since Trump's name was invoked, just drive up Collins Ave a few blocks and there is a Trump branded condo high rise, which has it's own structural issues that have been band-aided over: Link. Also similar to Champlain in that it was developed by a corrupt tax evader.

Quote (NOLAscience)

there was no load on the anchors last Thursday.

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.

Please allow me to move the discussion to Miami Beach, Champlain Towers South apartment building collapse, Part 03 , Thank-you.

SF Charlie
Eng-Tips.com Forum Policies

Quote (dik (Structural)(OP)28 Jun 21 14:54)

Miami Beach, Champlain Towers South apartment building collapse, Part 02

Please close this post to new postings.
Thanks

SF Charlie
Eng-Tips.com Forum Policies

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.

Seppe (Structural),

I note your disagreement with warrenslo who suggested the top few floors might have collapsed first while your argued the whole stack of flats could sink bodily downward.

I believe Warrenslo had mentioned some lights at the lower flats were still on (think I could make out at least 4 windows with light on). If that photo depicts the building when the collpase had commenced your suggested the whole stack going down bodily will not be credible. This is because when a flat shears a couple of levels downwards all the electrics would have been severed.

I believe warrenslo's theory has merit if a significant amount of the roof dropped onto the next level overloading it to fail sequentially. This was the exact failure mechanism of the two World Towers in 9/11. Every enigineer who has designed a building would know we never design one floor to carry the dead load of two floors in a normal building.

Warrenslo's evidence has not fully convinced me yet but I think it is entirely possible workmen doing work on the roof could have inadventently weakened some parts of this old structure, like intercepting a few rebar while installing attachments and fixings, to trigger a failure. To me it is more important to establish if it was indeed the collapse was initiated from the falling of the top two of three floors.

We engineers may be smart and thoughtful but our designs are always executed by the workmen who are not trained to think or to be careful like ourselves. Remember not long ago we have workmen initiated the collapse of the FIU footbridge not far away. The workmen was applying post-tensioning work as instructed by the engineer. Some of them died with the falling bridge.

Kreemerz (Computer),

I have two problems with the animation and theory.

(1) The pool deck was empty in the middle of the night but there was a huge unknown force acting downward and big enough to cause punching failure of a 9.5" thick slab by at least 6 columns. Where did this huge downward force come from?

(2) The deterioration of concrete is by water leaking into the surrounding concrete. The photos and reports showed the deterioration surounding the the pool wall at the garage level. It is high unlikely the water could drain upward to damage the pool slab elsewhere when it is is the ceiling of the garage. There is also no photo and reports citing pool deck damaged at connection of the pool deck with the columns where punching shear occurs. The columns did suffer damage by ponding of water at the garage base level though but that doesn't fit in with the animation/theory.

(3) Despite being reported corroded and damaged the pool deck surrounding the pool did not collapse but is still upright and not in distress.

Running with the post by Warrenslo that the top 3 levels collapsed first, along with the fact that there was an on site crane lifting roofing materials onto the roof the day before, there is a good chance the roofer overloaded a section of roof with materials. Also, on concrete slab roofs it is common to use a small track bobcat to remove existing roofing and save on labor. A Bobcat MT85 is commonly used and weighs about 3200 lbs empty. Also, it seems common amongst demolition workers, that they like to stockpile waste removed materials in large piles weighing several 1000 lbs.

According to the original drawings, lower strength concrete was specified in the columns of the top few floors.

There are cameras on that pool deck. Multiple cameras.

Wonder who has that video... I imagine some or all of the video is stored in the cloud?

• https://files.engineering.com/getfile.aspx?folder=fc9fb65f-f6db-49e2-bf82-9

Miami Beach, Champlain Towers South apartment building collapse, Part 03 , Thank-you.

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