Ugh. Looks like a bomb site

Interestingly there was a Magnitude 3.9 ‘earthquake’ off the coast of Florida in the last week caused by Navy bombing exercises.

It seems like a stretch to relate the two, but could it be ruled out as a cause?

Can someone with local knowledge give an idea of the seismicity of that area and whether a M3.9 earthquake would be significant compared to what it would (should) have been designed for in 1981?

There is a underground parking garage under the portion of the building that collapsed.

Gusmurr, when this building was constructed, Miami did not require seismic design. It would have been designed for significant winds though.

I can’t see the military exercise being the culprit. If I were doing the investigation, I would think corrosion first. We will have to see as it plays out.

Prayers to anyone trapped in the rubble or injured in this.

That's total and complete system collapse. You couldn't get it to pancake like that if you tried to demolish it.

Looks like panel construction - echoes of ronan point maybe?

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

Approximate area of collapse.

Cool_Controls, we’re did you get the information that there is underground parking? With the buildings proximity to the Atlantic, that would be a very complex design and construction.

Wow! And tragic to put it in a single word. My thoughts and prayers are with everyone effected.

Does anyone if this building was concrete or steal framed? Or know any specifics?

"Complete collapse of a part of the building" is a better description than "partial collapse."

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. - http://xkcd.com/319/

This might be important:

Quote (Article)

Authorities have not yet determined what caused the building to collapse but confirmed that renovations had been underway on the roof

Overloading leading to progressive collapse?

I cannot tell from the photos. Does it look like post tensioned construction or conventional rebar? Is 1981 construction too early for post-tensioning?

Current Google imagery shows construction in the adjacent lot:

Local news now has a video:
https://twitter.com/wsvn/status/140805404680880537...

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

April 13, 2021 Image from Nearmaps

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

Here is a view of the garage entrance that was mentioned above.

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

It looks like a pseudo pan joist system formed with insulation. I am not familiar with that technique. It looks cast-in-place. I cannot tell if the reinforcing is PT or conventional.

Video of Bradw1128's screengrabs.

https://twitter.com/wsvn/status/1408054046808805379

Very odd for a 40 year old building to fail in a catastrophic way like that. Be interesting to see what the cause may be.

I can't see a re-roof causing this. From the video it looks like failure initiated at the base. It would take an awful lot of materials to add enough load to a column to fail it.

Being so close to the Atlantic it could be some sort of long term corrosion.

Or something nefarious in the parking garage.

Quite an incredible collapse for an RC building (if this is what it is). This couldn't have been a single column failing but the whole ground floor somehow. Very strange.

Going frame-by-frame in the video it looks like the failure initiated at the base and over a large area. My guess is a sink hole.

Some more perspectives of the adjacent construction. Looks like that building has been completed based on the image posted by JoelTXCive.

you can see the entrance to the parking garage on Google street view.

If you are the City. what do you tell the occupants of Champlain Towers North & East, of probably the same construction?

Q. from an interested layman with no specific engineering background but some science training:

How do the Search and Rescue crews evaluate safety during operations? Are there steps they can take to rate risk in entering and searching partially collapsed structures, and what would those be?

There appears to be subsiding in the area adjacent the collapse. Look at the cars in the parking area. The depression extends out towards the pool.

I noticed that there appear to be exhaust fans mounted at ground level along the western edge of the parcel are these for an underground parking? (must be a pretty big garage if that is the case)

@rscrane

Not me, but my boss volunteered someyears back to be an on-call volunteer structural engineer for fire departments. He would train with them occasionally for building collapses, partial or full, etc. and basically he'd be directed to inform them if they could demolish this wall, or this steel section etc. Where to put up temporary shoring if needed, etc. The risk assessment portion however is valid, and he explained some law (this is hearsay, so im not sure how true this is) that carves out an exception for structural engineering consulting during ongoing rescue operations.

@rscrane Urban search & rescue teams often have a structures specialist on the team who will evaluate low/medium/high risk, lowest risk entrances to the structure, if/what shoring is needed, etc.

This is probably far more info than you ever wanted, but here is one of the manuals for this role: http://www.disasterengineer.org/LinkClick.aspx?fil...

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

Anecdotal thoughts:

A few years back I worked on a mid-rise condo of the same era and roughly the same height. It had a very scary punching shear failure that was slow enough for residents to notice, report it that day, and for contractors to show up and install shoring posts immediately. Long story short, after a lot of investigation the columns of the condo portion didnt line up with the parking garage below so the original designers put transfer beams between the parking garage portion and the condo portion. The contractor did not put the specified shear reinforcement(and the concrete material breaks were quite low)at the transfer beams and it took 30+ years for a load case for the failure to show.

This is a complete speculation on my part, but it looks like theres a below grade parking garage here and I wonder if the column layout matches the framing above. You can see in the images the columns of the garage have clearly punched through what appears to be the 1st floor slab.

Re: rescue training, etc - there is a facility in Georgia, US built specifically for the rescue training operations. Perhaps not so much structural assessment, but they definitely practice placing shoring and demolition, etc.

I may or may not have been involved in the construction... .

guardiancenters.com/

Good post Ricky. If it was some sort of punching shear failure I'd sure think it would cause a progressive failure like we see in the video.

Tragic, sickening to say the least.

Shooting from the hip -

If I had to guess I'd say this was a foundation failure due to subsurface karst topography. Stormwater management in Miami Dade SFWMD is usually done (or at least as of the mid 2000s) with infiltration pipes and baffles into the sandy subsurface aquifer. If the pH of the runoff is low enough, and that dropped the overall pH of the aquifer, it could have dissolved a layer of subsurface limestone and created an underground cave. When karst fails it's a dramatic thing that happens quickly, and that's about all I can think of for this one. The karst theory would fit spinspecdrt's photos too.

Typically SFWMD and the other water management districts prohibit water quality treatment through infiltration in known karst areas, and I don't know if Miami is a highly karst zone or not. I only did one project there, and we did infiltration in our storm sewer network out in the parking lot for it. It was relatively straight forward and we never did any investigations about karst.

I've done a project recently in Nashville where they required us to do infiltration measures for stormwater management even though we vociferously fought them on it because we knew we were on karst. I fear some failures similar to this may be in Nashville's future, whether this one was karst related or not.

edit: Ricky's post above is a great guess too.

edit2: some great rebuttals to this idea are below and I agree it doesn't seem like a karst related thing based on further info in the thread. Disregard, but I'm leaving it up for posterity.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com

beej67, karst related sinkhole was my original thought but as Rimitikitavi pointed out, the columns are still in place and have punched through the deck.

Sinkhole was one of my first theories having seen some dramatic ones from Central Florida in years past. But from this map that looks unlikely for this part of Florida.

http://fcit.usf.edu/florida/maps/pages/11100/f1116...

I'm wondering about possible impact damage from a vehicle hitting a column in the parking garage.

I also remember staying at a similar condo complex in the Florida panhandle a couple of years ago. There were enclosed storage rooms inside the ground level parking garage where people could stash their beach chairs and pool toys. Inside those rooms was not climate controlled so they were incredibly damp. Anything left in there rusted quickly along with the doors, door frames, and anything else metal. So maybe there could be accelerated corrosion issues in exposed but mostly hidden areas of the parking garage?

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

I think the punching shear failure seen in the photo could also have been caused by the impact of the collapsing building landing on garage roof slab.

Just got off the phone with my geologist buddy who is a sinkhole expert, worked with him as a structural engineer for over 8 years all around Florida. South FL geology is very different from Central and N FL geology, so a sinkhole as most know them is very unlikely. We are thinking on the beach there that would be a pile foundation to competent limestone probably 60 feet or more. It is possible that over 40 years some dissolution of that limestone could occur, but the rate is so slow that one would anticipate any settlement of the piles would be very slow and distress in the building would be apparent. The video of the collapse is also not what one would anticipate from a pile foundation failure. (I reserve the right to be completely wrong and surprised.)

The reports are coming in on the roof being worked on and there was a material lift for two weeks on that side of the building. I have evaluated at least two residential roof collapses because of improper staging of roof materials, albeit wood-framed residential, not a multi-story concrete building. But if 40 years of corrosion had affected the reinforcing, then you stage materials on top of that compromised roof slab, this type of failure is entirely possible. The roof repairs could have been to address an unmitigated roof leak, further exacerbating the situation.

I can not tell from the pictures if it is a flat slab with traditional reinforcement or post-tensioned, but we know that PT is vulnerable to catastrophic failure. Corrosion may have affected the ends at multiple floors and balconies. Once the roof slab started to fail it would pull inward on the walls, and the weight and dynamic force of that collapsing onto the upper floor could have caused a chain reaction failure, not that different than the World Trade Center collapses.

Like with most collapses, there are often multiple causes, and this could be one of those.

But the video does not seem to show a top-down pancaking

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert! https://www.youtube.com/watch?v=BKorP55Aqvg
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I saw a picture of cars sitting on a slab that was detached from its supporting columns. If you lose a slab in the parking garage due to punching shear, the column slenderness immediately increases with a commensurate loss of axial capacity. If that capacity is less than demand, gravity will do the rest. Whether the parking garage slabs were overloaded or have been slowly failing for some time until last night the capacity finally dropped below demand is currently unknown. My guess is the parking garage slabs failed in punching shear for some reason and the suddenly (more) slender columns were instantaneously overloaded leading to the collapse.

ETA - from the picture, there weren't drop panels or thickened slabs at the column locations.

I just saw this report that there's something like 50 people unaccounted for:

More than 50 unaccounted for in deadly Surfside, Florida, building collapse, official says

https://www.cnn.com/2021/06/24/us/building-collaps...

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

IRstuff, that's what I see as well. Sure looks like the failure started near the base. Punching shear down low is certainly plausible and would be abrupt and without warning.

I think in order for the roofing to have caused the collapse the weight of materials would need to buckle a column (or fail a transfer beam). Sure seems like it'd take an awful lot of load since it's 8 stories+.

I just heard that it's now up to nearly 100 people unaccounted for.

When you consider that this collapse occurred at 1:30AM, if this apartment building was close to being fully occupied, that might be a very conservative estimate.

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

Collapsed Miami condo had been sinking into Earth as early as the 1990s, researchers say
Link

Closer view of punching shear failures: https://s7d2.scene7.com/is/image/TWCNews/062421_n1...

@bones206. That is under the section of the building that is still standing isn't it? Seems like incidental damage to me from being hit by falling debris.

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

According to this item, the building was in "OK shape" and the owners had just started a mandatory 40-year inspection and upgrade:

‘The building was in OK shape.’ The upscale condo near Miami Beach still collapsed

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

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

I'm curious why in the photos posted here we don't seem to see any rescue efforts despite reports of up to 99 people being missing? Anyone seen anything regarding this? Seems strange to me.

https://engineervsheep.com

Quote (bones206)

Closer view of punching shear failures: https://s7d2.scene7.com/is/image/TWCNews/062421_n1...

I spent more than a few minutes scrutinizing the rubble pile before I noticed the parking slab under the standing portion. There is not a lot of reinforcing in the top of that slab. Nor do I see any PT even though the slab is pretty thin. I think that may be why the rescue efforts are not extremely active and robust. If that parking slab did that under the entirety of the standing portion, I would be really concerned about the stability of that remaining portion.

Robert Hale, PE, SE

Link

This is a pretty interesting tool to see the extents of the collapse.

Here's an article without a paywall, about the sinking of the condo building. Measured in the 1990s as 2 mm/year. Apparently this was built on "reclaimed" (i.e. filled) wetlands.
Link

@Agent666

Search & rescue pics:
https://www.miamiherald.com/latest-news/jdzgc4/pic...
https://www.miamiherald.com/latest-news/tvr4b7/pic...
https://static01.nyt.com/images/2021/06/24/us/24mi...
https://i.cbc.ca/1.6078788.1624557189!/fileImage/h...
https://s.yimg.com/ny/api/res/1.2/qJfAx9QVjbb2fQAp...

Video:
https://www.miamiherald.com/news/local/community/m...
https://www.nbcnews.com/now/video/miami-mayor-mass...

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

I served with a USACOE USAR task force as a structural engineer for several years and although I did not respond to anything quite like this, I can tell you that it can take much longer than you might expect for a full USAR team to mobilize other than a small advance recon team. I recall that response time was one of the issues in the Elliot Lake Mall collapse in Ontario as well. Response times will vary from state to state and from team to team due to everything from long term state funding and local politics down to the diligence of the team itself, and so many other factors. I'll defer to others more familiar with TF3 and the other Florida TFs as to the circumstances surrounding readiness.

Also, even though a collapse like this is the worst case event that TFs train for, it is not something that many teams or engineers have ever worked and I'd think that the mobilization of teams and cranes and other logistics would take 24 hrs or more. This seem unacceptable on the surface however many teams do not have the support they need to be on continual standby and deploy within 4 hrs for an event like this.

Most of you already know but I will say that a pancake collapse like this is the worst possible scenario for survivors as there are so few voids and refuge spaces. Rescue will be slow and dangerous and will be frustrating to observers. It really makes your mind start to work in overdrive trying to conceive a system or technology to rapidly clear a debris field like this to reach survivors but the reality is that it is an unknown and unstable and unconsolidated mass which will be removed one piece at a time, and on that last point I am exaggerating less than I wish.

Clearest daytime image I could find of the collapse showing the parking area.
https://i.dailymail.co.uk/1s/2021/06/24/14/4462478...

U.S. NEWS - 99 missing, 10 hurt and 1 dead in high-rise collapse near Miami Beach, officials say, Surfside Commissioner Eliana Salzhauer said search-and-rescue operations could "play out for days." Posted about 5:00 PM EST

Some good (can you say anything about an event this awful can be good?) video and before / after comparison.

Quote (Gary Slossberg)

Another possibility, he said, is that the building's balconies may have had some construction issues. Many Miami-area buildings, he said, are built with concrete balconies that are "back-pitched," meaning they don't allow water to escape properly after it rains.

seems like this could be a failure mode if water intrusion was occurring at every balcony

https://www.foxbusiness.com/lifestyle/miami-buildi...

Quote (OH)

It looks like a pseudo pan joist system formed with insulation

Those lines appear to be the tear lines where the bottom steel has ripped out of the concrete soffit. You can see those tear lines extend into the support wall.

Quote (I recall that response time was one of the issues in the Elliot Lake Mall collapse in Ontario as well.)

I did a detailed critique on the Engineering report for the Algo Mall... report was terrible, and apparently written by a PhD dude...

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

-Dik

BBC News 22:15 GMT+1 reporting 99 people missing.

Politicians like to panic, they need activity. It is their substitute for achievement.

I noticed that the remaining part of the slab around the columns, which have punched through, is almost nothing:



I would have expected the normal ~30 degree pyramid shape still attached to the column, unless this was lost among all the damage and debris?

gusmurr: Based on that picture I dont think those columns had capitals or drops (based on bot reinforcement location). Look at where the paint ends, it's to high if there were capitals that sheared off.

Man that far column looks precarious, like it’s already sheared but is just barely hanging on.

Construction PE (KY)
Bridge Rehab, Coatings, Structural Repair

My speculation (at this time) is also that things initiated in the underground parking level or subgrade. It looks to my eye like the debris pile in the vicinity of the portion which collapsed first appears to be a 'shorter pile' than the portion of the structure which collapsed second. If true, that may also support a sinkhole or other similar subgrade issue concentrated under the area of initial collapse.

Wow - my thoughts are with all those affected by this. Truly horrifying.

That column slab connection looks distinctly lacking in reinforcement, both top and bottom, for a relatively thin flat slab spanning 6 to 8m.

From the Daily Mail (almost a newspaper)...

https://www.dailymail.co.uk/news/article-9722547/C...

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

-Dik

You're right about that.

Headline: "Collapsed Miami beach condo tower hadn't been certified since 1981 when it was built and has been 'sinking into the ground since the NINETIES' "

Article: " Miami Dade building code dictates that buildings have to be re-certified every 40 years so the building was due to be recertified for the first time this year. "

Still a tabloid.

Quote (Engr1888)

The structure stood for 40 yrs before collapse, so I think the structure was adequate.

You can’t assume that a structure standing for decades means that it’s structurally adequate. Inadequate structures often survive for significant amounts of time.

Standing for 40 years is no guarantee of structural adequacy, or future performance.

FoxSE14, I agree the debris pile in the area that fell first is significantly smaller. I image there is only one parking level below grade due to proximity to the ocean. It appears a large portion of the debris from the first failure is now below grade. It's interesting (and terrifying) that the second piece stood for a good 5 seconds after the initial collapse.

I once looked at a 1910 bridge that had some distress (scouring) and eventually realized that the bridge foundation did not rest on rock (about another 3 feet). This bridge was designed for very heavy rail load. But everyone said is was really strong until they shut it down for a while.

The rescuers have about 100 hours to get the trapped people out. There might be some space between the pancaked floors that will allow them to survive. Really hope so.

ex USAR Task Force 7 Sacramento. Structural Specialist.

The collapse looks like it started next to the elevator shaft. At first I thought, maybe they overloaded the roof with roofing materials but the failure was bottom up. Still have to wonder where construction supplies were stored.

The weekend after the Loma Prieta Earthquake a team from our company was working the Oakland area. Signed in, at one Red Tagged building 'transient hotel', walked up 7 flights of stairs to a landing where we could step out onto a low roof. Standing there looking up, there was floor after floor of giant 'X' patterned shear crack between the windows. The lowest 'x' shear crack, I could put my arm through. I reached in and grabbed a hunk of concrete, with my gloved hand and squeezed it, until it crumbled in my hand. There was no modulus left, completely friable. I can't say whether it was carbonation or if the sand used at the time was just not washed well enough. The building had smooth rebar, so early 1900s. Could not believe there were people sitting on the mattresses on the floor in a couple units, wondering what they should do.

I am a bit puzzled by the report about the building settling 2mm a year. One news station state the Professor indicated the land was settling. That has been my impression since looking at Sweetwater across from the FIU Pedestrian Bridge Collapse. There is an ongoing effort to remediate flooding in Sweetwater. All the old USACE work has reached capacity with runoff from surface streets. The problem stated was that the land was settling and also the Okefenokee Swamp watershed was getting larger. Bigger and more pumps were needed. Sweetwater is a good ways inland.

I don't see any tie beams. Corrosion?? I once saw a building pancake because of a single stirrup failure in a single column. However, it was only a three story apartment building and only the first floor pancaked. It was also as a result of an earthquake of 5.5 on the Richter scale with significant vertical shocks. No earthquake here.

Quote (spinspecdrt)

It appears a large portion of the debris from the first failure is now below grade.

...my thoughts exactly. Continued speculation for sure, but...that initial collapse debris could even extend below the base of the building within some sink hole whose size is most certainly hard to discern right now. Again, my heart goes out to those people.

Related: has anyone else noticed the LACK of structural engineers weighing in among the media outlets? I admit I have not viewed any of this on television today, so perhaps I missed one or two, but I'm reading article after article with 'expert opinions' from

• local architects 'who've never seen this in 30 years of living and doing business in S. Florida',
• some owner of a local home builder (very applicable to mid/high-rise concrete construction over underground parking built along the coast),
• an attorney who represented someone on a trip & fall case in the building who is 'very familiar with that building'...

...WHERE are the SEs and PEs of Florida?? I hate to say it, but this is the kind of event where the public is thirsting for our knowledge and they don't even know it...talk about an opportunity to elevate the profession. Perhaps we as a field need to have public speaking and media training to draw us away from our desks and in front of the cameras in cases like these. Meanwhile, I have to get back to my condition assessment report, so someone else please do it. (end rant)

FoxSE14,
Or perhaps the structural engineers consider that it is irresponsible to wildly speculate, as some of those other 'experts' are doing. The press will tag an expert label on anyone who has ever held a hammer.

Very brief observations based on what is known so far:

1. @FoxSE14 - Hopefully local PE's are staying cautious and don't want to speculate. Although I did hear an FIU professor answer a few (not so great) questions of a local reporter.
2. There was one level of underground parking - this is actually not uncommon in this area - land is way too valuable to waste any, esp. when above ground gives you ocean view and there are height restrictions of the oceanside properties.
3. My guess would be that the columns holding the ground floor (the lobby/pool deck level) did not coincide 100% with the columns above.
4. Collapse looked, as others have pointed out, in the center of the building. (which ironically appears to be slightly shorter than the oceanside end)
5. As others have stated above: could be a 'simple' as a column being taken down in the parking, maybe the overloading of materials happened at the lobby/pool deck area rather than at the roof? I've heard random statements about a possible crane aiding with the ongoing roof work, but have not seen any sign of one or that being verified. It would be sad to find out the failure of ONE column would cause this, so maybe a transfer beam or punching shear failure would make more sense? Although with little redundancy if the floors above don't match the basement columns then this def could be a weak point.

It's hard to imagine a tragedy like this happening with no warning signs. Expecting the typical "stacking of mistakes" result.

God help the people still trapped and guide the responders to find them ASAP.

To whoever asked above why there is no recovery - there is! Miami Dade PD tweeted out a video showing them working through the flooded basement - this is no easy task to try to find Survivors and not compromise the debris pile
https://twitter.com/MiamiDadeFire/status/140817768...
You can find the pictometry historical aerial views for free on the Miami Dade Property Appraiser site
-- sorry for long post, this has def hit way to close to home

I agree with FoxSE14, it should be SEs/PEs commenting on this and not other "experts".

I got about 5 phone calls this morning from friends and family asking my opinion on the collapse. I have no idea what happened, but I loved having the discussion with them.

As long as those engineers talking to the public state that their opinions are speculation, it would be better for our profession overall.

S&T

Some background on the recertification process: https://www.wlrn.org/news/2021-06-24/after-a-dea-b...

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

What an absolutely horrendous event.

Looking through recent sales - the finishes in the common areas and the units are pretty high-end, I would guess than any signs of on-going settlement would easily reflect on the marble floors and floor to floor windows?...
https://www.zillow.com/homedetails/8777-Collins-Av...?

The typical building foundation in this region consists of grouted friction piles and grade beams. Underground parking structures with transfer beams are basically par for the course. What I can not wrap my head around is how a building can have such a catastrophic failure without anyone noticing the obvious signs.

The only thing that I can plausibly imagine is that a major transfer beam failed, which overloaded adjacent columns -- leading to a cascading failure.

In this region moments from seismic events are not an issue, our biggest challenge is protecting the buildings envelope from wind loading, especially negative pressure.

Dating back to 1980s, what were the disproportionate collapse requirements like back then over there?

A truly horrific event.

Latest news says four confirmed dead and 159 missing. Absolutely tragic.

One news source has said there may have been concrete restoration ongoing - thinking if they chipped too much or more than one column at once without proper shoring, combined with the "weak story" in the lobby where it is likely columns shifted locations....
So sad and tragic that I can't wrap my head around how a failure like this happens..

This picture just makes my jaw drop and my heart sink: https://i.dailymail.co.uk/1s/2021/06/24/14/4462478...

https://www.yahoo.com/news/video-shows-concrete-ra...

Someone has security video from inside their apartment just before collapse.

How much concern should there be about the remaining structure? I’m not a structural guy but it seems that floor diaphragm might be kind of important as it pertains to those columns.

It seems like if any sort of forensics is going to be done the cleanup and recovery will have to be done in a very controlled fashion. Will they have to bring that part of the building down before they can start to clean all of this up?

Where does this spontaneous (for the moment) collapse disaster rank in the US? And worldwide?

Tragic.

Has anyone ever seen a design where a single point of failure leads to this? I sure have not. Spalling decks, columns, sheer walls and beams, along with PT wedge failures on bonded PT are pretty common in buildings of this type and era in the region. It is really not a big deal in terms of life safety, simply because the signs of distress are pretty obvious, and remediation of the various conditions is pretty straight forward.

I really am doubtful of subsidence, simply because a mat foundation with piers is not very common on oceanfront construction at that NGVD or NAVD elevation. The sheet piles for the underground parking and the associated dewatering is tough enough,

Depending on how many are recovered vs. lost in the pancaked rubble, it could be the second worst non-deliberate structural failure (in the USA), right behind the Hyatt Regency. This is coming from this article:

https://www.nydailynews.com/news/national/ny-deadl...

Another data point:

One of the residents claims he noticed pool patio pavers cracking during the construction of the adjacent high rise building.

Quote:

Cohen said he raised concerns years ago about whether nearby construction might be causing damage to the building after seeing cracked pavers on the pool deck.

Source: https://www.pbs.org/newshour/nation/wing-of-miami-...

"Has anyone ever seen a design where a single point of failure leads to this?" - Keith 1
Ronan Point Apartment Tower
Alfred P. Murrah Federal Building - ref. Oklahoma City Bombing

In this case, I don't think it is wild speculation to hypothesize that long term settlement overstressed and led to the failure of a 2-way floor slab to column connection. This doubled the bracing length of this column which then exceeded its axial capacity and failed suddenly under buckling. The other hypothesis would be a failure at a column to transfer beam connection.

Questions to investigate - what is the detailing of the 2 way slab to column connection? Photos only evidence top horizontal rebar
What was the geometry of the parking grid columns to apartment grid columns?
Did the building really settle 3" and was that settlement discrete or overall?

I think its important to recognize that the reason for our attention on this disaster is due mostly to the lessons that we, as engineers, learn from failures. A failure that occurs suddenly 40 years after a building's construction, especially if it was properly detailed and built, is something to be identified and corrected for the sake of the rest of our buildings' catalog.

It was perhaps a filigree slab.

@Spartan5
https://i.guim.co.uk/img/media/cff046f016f8d329b3d...
and
https://i.guim.co.uk/img/media/1bf3fd047ad86fc5c0e...
show damage to the walls about half way up one remaining façade.

@Spartan5 I'm actually concerned about the columns supporting the remaining mid-rise. Their unbraced length has doubled due to the ground floor slab falling down. Thats can be a significant drop in axial and bending capacity for a column.

ongoing settlement over decades certainly seems related to the problem. Seems a, "pop-type" failure, for sure.

Live load considerations?

Shoreline rebar deterioration and or inadequate cover from the onset.

Such a catastrophe!

f-d

ípapß gordo ainÆt no madre flaca!

Quote (Teguci)

I think its important to recognize that the reason for our attention on this disaster is due mostly to the lessons that we, as engineers, learn from failures. A failure that occurs suddenly 40 years after a building's construction, especially if it was properly detailed and built, is something to be identified and corrected for the sake of the rest of our buildings' catalog.

As I just learned (and shared the link above), the instigating event behind Miami's 40 year recertification process was the collapse of the Miami DEA building in 1974, which was 40 years old at the time. The Miami-Dade engineer behind the effort saw the particular vulnerabilities of aging structures in the area, and was determined to create a process that would help prevent future collapses.

My wild-ass guesses (WAGs):

Long-term settlement caused cracks in concrete, allowing saltwater access to the reinforcing rebar, and increased stresses on connections.

Vibration from nearby construction (and general use) worsened fatigue.

Roof work increased live load.

One of the basement connections eventually failed, and the whole thing pancaked.

Obviously there are lots of open questions. Was the settlement due to sea-level rise unaccounted for at the time of construction? What was the immediate cause of the collapse? Are any of the WAGs even true, or was it something else like a sinkhole? What code or enforcement changes could prevent this? How many other buildings in the area are at similar risk?

Just a question for the SE types here, but has there been any change or increase in live load or dead load for parking structures due to the fact that cars seem to get bigger and heavier with every decade?

I wondering if there is a gradual effect a bit like the increase in "average" passenger weight that they use for aircraft has needed to be updated as the population got bigger and heavier??

A little of googling finds the average weight of a car in the 1980s was about 3,000 lbs and is now over 4,000 lbs.

Given the residents of the block are probably in the higher percentile earning group are likely to have bigger cars than the general population??
Could you be talking double the weight compared to what was assumed in 1980?

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

That's a 1.25x increase in weight, but aren't design loads for 3x+? And I don't think I could buy in to the theory all of the cars (on the top garage floor) were up-sized... maybe 25-50%? I'm not sure I buy the average weight of a car being 4k pounds, either... there may be a number of large vehicles that hit that weight (SUVs and the like), but plenty of others are well below the 3k mark (your average mid-size is probably in the high-2k range).

Dan - Owner
http://www.Hi-TecDesigns.com

Quote (LittleInch)

Just a question for the SE types here, but has there been any change or increase in live load or dead load for parking structures due to the fact that cars seem to get bigger and heavier with every decade?

Before IBC 2006 I believe parking garages were 50 psf. Now they are 40 psf.

Average car length is like 14-15 feet x 6' wide. Cars this size weight less than 3000 pounds. 40 psf gets you 3360 that's assuming cars are packed like sardines. With the drive aisles spaces between cars, etc. 40 psf is pretty conservative in most parking garages.

RC

bones206,

Maybe they should make it every 30 years?

Good Luck,
Latexman

Some of the residents observed cracking at the pool and maybe other locations during/after the adjacent building's construction. I've read other's thoughts about soil subsidence from a possibly higher water table coupled with construction vibration could have been an issue, but I wonder if there were any subsurface structures/other construction nearby that required the water level to be dropped via well points.

wonder if the neighboring construction included dewatering?

f-d

ípapß gordo ainÆt no madre flaca!

First of all my prayers to the victims and family of this disaster.
a disaster of this magnitude. where does the investigation begins to resolve the cause?
since this is a high rise building were to start.
what test would be required.

Wonder what the lead agency would be for the investigation? With a transportation failure, including bridges, it would be the NTSB. Even the FIU pedestrian bridge investigation was led by the NTSB. I'm not aware of an established process for a building failure investigation or even what government level - local, state or federal - has authority.

There are some reports of there being a significant amount of standing water in the garage at least a few days prior to collapse. How might that have contributed?

https://www.newsweek.com/water-underneath-surfside...

NovaEngr, it looks like NIST will at least play a role.

Quote (Washington Post)

A team of six National Institute of Standards and Technology scientists and engineers will be sent to the collapsed portions of the condo to determine whether an investigation or study will be conducted.

Jennifer Huergo, a spokeswoman for the government agency, told The Washington Post in a statement that the experts will work with federal, state and local authorities to identify and preserve materials that could be helpful in understanding why the collapse happened.

“If a full investigation or study is conducted, its ultimate goal would be to determine the technical cause of the collapse and, if indicated, to recommend changes to building codes, standards and practices, or other appropriate actions to improve the structural safety of buildings,” she said.

The team will not interfere with search-and-rescue efforts and it will enter the site only after it is determined it is safe to do so, Huergo said.

The agency has conducted four previous investigations, including final reports about the World Trade Center, under the National Construction Safety Team Act, which President George W. Bush signed into law in October 2002.

Monitoring building for settlement, tilting & vibration is a must for multistory and high-rise buildings. Routinely inspecting structure for signs (cracks, deflections, etc) of distress needs to be enforced.
This type of catastrophe appears to be from overall stability failure. Buildings just don't collapse suddenly like this even with some local structural failure.

A condo building about three miles away collapsed before demolition a few years ago. Empty at the time.

https://profilemiamire.com/miamirealestate/2017/9/...

Quote (As I just learned (and shared the link above), the instigating event behind Miami's 40 year recertification process was the collapse of the Miami DEA building in 1974, which was 40 years old at the time. The Miami-Dade engineer behind the effort saw the particular vulnerabilities of aging structures in the area, and was determined to create a process that would help prevent future collapses.)

If Miami wasn't enforcing this requirement, I can see the lawyers lining up at their door... criminal negligence, anyone?

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

-Dik

so That is why an investigation is necessary

On the early news this morning, a woman spoke of her phone conversation with an acquaintance who lived in and was speaking from her condo that faced over the pool. She said something to the effect that "The pool is sinking, the sidewalk is sinking". Then the phone went dead and she's pretty obviously missing. Don't know whether she was in the first or second collapse. It would indicate though that the pool area (underground parking) collapse happened very soon or even before the first collapse. Horrible.

Jon43442, that building collapsed during a poorly executed illegal demolition effort.

https://www.eng-tips.com/viewthread.cfm?qid=442327

Testimony about woman who was talking while building collapsed at 1:30 of this video:

https://sw-ke.facebook.com/CBS12News/videos/teri5a...

There's definite spalling on the underside of the concrete on the roof and some balconies in Google street view. Rebar exposed. Image taken in January 2021. The March 2018 images don't show nearly the same level of damage, just a small amount on the corner of the roof. Even that isn't present in the 2015 photos.

https://www.google.com/maps/@25.8732046,-80.121095...

@Eufalconimorph

I played with the street view you linked to, and you can definitely see that several of the lower balconies were in poor repair on their undersides:

Yup, here's another view of damage from Google street view:

https://www.google.com/maps/@25.8732099,-80.120874...

https://www.google.com/maps/@25.8732046,-80.121095...

But would that explain it collapsing from below?

'Wagner also stated his client from 2015 recently provided him with pictures of her unit at the building, which showed "exposed stucco that was broken off showing the cracked concrete within and the rebar completely corroded through."'

https://www.newsweek.com/2015-complaints-collapsed...

To littleInch's question, cars have been getting smaller and lighter, it's the pick-ups and SUV's that have replaced them which are getting heavier, although that's not a hard and fast issue either. For example, my new 2021 GMC Terrain is about 400 lbs lighter than the 2013 GMC Terrain that I traded-in. And my wife's Mercedes C300 is lighter than the Honda Accord that it replaced, primarily due to about 70% of the external sheet metal being Aluminum.

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

2018: not much visible concrete damage
2019: construction of building on adjacent lot
2021: noticeable damage at roof and balconies

I am hesitant to speculate, but that building did not collapse due to overloading. Design defects, construction defects, settlement, corrosion, sinkholes, are all issues for investigation.

What is the procedure in that area regarding dewatering during construction? Are there established rules? Do people follow the rules?

I'm with Hokie. I think there is a lot to learn here.

In big accidents like this, it's rarely 1 single item that causes the failure; there are usually many contributing factors that all come together in the wrong way.

I would think the sinkhole aspect will be validated or thrown out rapidly; but all the other possible causes will probably take months to figure out.

After the Florida International Pedestrian Bridge, this is a 2nd large failure in Florida. I think that will motivate the public; who will then motivate the politicians on some substantial engineering changes. I would be surprised if there were not national implications.

We will be studying this collapse in college classes forever, just like the Hyatt Regency walkway collapse in the early 1980's.

I feel so bad for the families in that building.

Quote (JoelTXCive)

After the Florida International Pedestrian Bridge, this is a 2nd large failure in Florida.

Don't forget the collapse of the parking garage from about a decade or so ago and the collapse of that outdoor deck that injured a bunch of people.

When they do the root cause analysis I hope they add up all the money ever paid to real estate agents to sell the land and units involved and compare it to all the money ever spent on design, maintenance and inspection.

Insurance will or maybe cover it.

@JoelTXCive right on the money.. never a single issue. Sinkholes are unlikely in South Florida and that building is surely pile supported just like 95% of structures along the coast.

Here is some additional information, including name of firm doing the 40-year certification in link below.
Someone asked above if the enforce the certification, they do, but just like the rest of sad state of our profession, a lot of people don't want to pay for what i think is a big liability and responsibility task.

https://www.local10.com/news/local/2021/06/25/meet...

When you look at the debris field, you see columns and floors but not many walls. Link It explains why the debris pile is not higher, most of the walls are CMU, which can be seen here and there but likely a great deal completely crushed. Another reason, there isn't a lot of hope for finding survivors.

@epoxybot that is very typical construction in S Florida, main structural system is concrete slab/columns/beams, shear walls at cores. Most of the masonry is "infill" only

That bottom photo in epoxybot's post is intriguing. Are those black rods individual unbonded PT tendons? Are those closely spaced spalls where the tendons were? Is that photo of a tranfer slab?

I'd also be looking at the detailing... there appears to be little redistribution.

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

-Dik

The building changed its HVAC equipment sometime after 2019. This equipment was on a red steel platform with corners sitting on concrete columns clearly visible in aerials. The equipment flipped over the platform as it fell down the building, this tells me it didn't ride down the building but may have been the reason of the collapse - falling first. The new equipment was on sitting the portion of the building that is still standing yet fell. There also is a large gash in the remaining portion of the building under where the equipment sat.

Furthermore, initial reports confused 135 and 136 units, it appears at some point the "Penthouse A" was added (possibly during construction) as the flyer from 1980 for the building only states 135 units and 12 floors. The penthouse is the 13th floor and 136th unit - it was recently sold and the listing noted marble floors. The penthouse and HVAC unit appear to share a column at the SE corner of the HVAC platform that seems to be the source of the collapse.

I wonder if they placed any additional equipment on or near the HVAC platform prior to collapse and if the building was structurally designed for the penthouse. It is also possible the platform itself failed if it was not designed for the new equipment - it does not look like they replaced or strengthened the platform when the new equipment was installed. To me, this does not look like a sinkhole but a progressive collapse from the roof for the first portion that collapsed as it did not tip over, followed by a failure of a low level (possibly garage) column due to debris causing the second collapse where the remaining building essentially tipped over on top of the first collapse.

Note: I have not been able to access assessor or permit info for this building on the town or county websites, it seems to be blocked - which is pretty unusual.

-W

2019 aerial (old equipment):


2020 aerial (new LARGER equipment):

hokie66, good eye. Those look like PT tendons that have been ripped out of the bottom of that slab as the area beyond came down. This spot looks to be at the juncture between the standing and the collapsed. The rescue worker seems to be standing on one or two floor slabs that have come down along with the PT. Area to right shows something similar with the PT still in slab. Although, the way those concrete blocks are dangling, and it being near the column, that could also be mild steel in the slab-column connection zone.

I'm not seeing any PT??

Dik - yes, what I keep wondering is how a localized failure event became a near global failure.

Whatever the failure mechanism was, it started local. Why couldn't those forces redistribute?

In the Oklahoma City bombing, half the building was blown off and it did not pancake. The same is true of the World Trade Center bombing in the mid-nineties. Both buildings took massive blows without total global failure.

It's being reported that heavy smoke is starting to come from the rubble, that it appears that there are fires burning somewhere under the debris.

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

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

Quote (hokie66)

That bottom photo in epoxybot's post is intriguing. Are those black rods individual unbonded PT tendons? Are those closely spaced spalls where the tendons were?

hokie66: No PT from my observations. I am seeing bottom rebar that has 'unzipped' from the slab soffit.

Doesn't it look a little too clean to you Ingenuity if those are direct bonded bar? I know the water has probably washed off a bunch but when I repair structures concrete is stuck onto rebar all over the place, even when it basically falls down from the slab. To see all those bars cleanly rip from the underside, it just feels like there was a greasing agent or something on the bars inhibiting the bond. Maybe not, but it's weird to my eye. Those bars look like new.

Quote (TheGreenLama)

Those look like PT tendons that have been ripped out of the bottom of that slab as the area beyond came down.

I don't think these are PT tendons.

No appearance of drape. No anchorages appear to have been ripped out. No one - not even in the 'evid-80's' - placed single PT tendons at 12" centers - always multiples bunched in flat groups at greater spacings.

Looks like deformations on the fallen/hanging 'bars' - so possibly rebar (that has unzipped from the slab soffit)?

The lack of ductility here is truly striking.

I re-watched the video and it doesn’t look like a “pancake” type of progressive collapse. There’s a loss of support of one side the building which then radiates through the rest.

Regardless of what caused the loss of support, the structure should have been able to redistribute that load.

Where are the transverse bars? I guess the longitudinal bars (in this view) were on the bottom of the cage and they unzipped?

If the design was inadequate, can the insurer's walk away? and, being condominiums, are the owners responsible for the repair costs? Some questions... Same questions for Millennium Towers in San Francisco.

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

-Dik

In Texas, to my knowledge; all design responsibility for the engineer and contractor ends at 10 years. They call it the Statute of Repose. I think even if you are grossly negligent you walk after the 10 years. I don't know if other states have that.

I see what you are saying. The insurers will say it was a bad design from day one, so how can they be responsible.

How about a broken water main, possibly caused by the nearby new construction?

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

My first step would be to look for the construction documents, and at the same time start to test in place concrete strengths.

Here's the Link for the Garage photo. Definitely Rebar. Link

No doubt about that. My query was about the black tubes. Maybe conduit?
But I agree with someone else above that the deformed bars look uncommonly clean to have been ripped out of the slab.

In many of the photos you see the same pattern of spalling on the underside of the floor slabs. It makes me think the rebar was just laid on the forms without chairs, and the rebar wasn't really imbedded in the concrete.

There was a building collapse further up the east coast of Florida long ago (early '70s?) where the chairs were too tall. The building pancaked during construction as an upper floor was being poured, killing several workers. As I recall, the incorrect height of the chairs was found to be a major factor in the failure, so proper placement of the rebar is obviously critical.

Would having the rebar too close to the bottom surface seriously weaken the slab? Or is this something that would show up after the failure that didn't contribute to the failure?

Quote (Retiredat46)

There was a building collapse further up the east coast of Florida long ago (early '70s?) where the chairs were too tall. The building pancaked during construction as an upper floor was being poured, killing several workers. As I recall, the incorrect height of the chairs was found to be a major factor in the failure, so proper placement of the rebar is obviously critical.

On this building if you look at the roof level and the floor below that (11th or 12th), the rebar appears to have also unzipped like the photo posted at the ground level (photo above):




I think the bottom cover to the bottom rebar was very small - with possible badly consolidated concrete surrounding bottom of rebar and therefore little bond ==> hence ease of unzipping.

The potential unzipping of rebar may have commenced at a construction joint - the rebar was developed into the slab portion that collapsed, and as the slab/s fell it ripped/zipped the reduced-cover rebar in the span that remained. Notice how 'clean' the exposed slab edge at the roof level.

Also, notice the 3" vertical slices @ 10" c/c (?) to the dry-wall under the roof slab soffit - rebar 'cut' the top of the partition wall.

The sudden collapse of relatively new RC concrete frame building is unusual. As the failure appears to be related to the crushing of
one or more concrete columns at the garage level the plausible reason is salt weathering of concrete. Concrete spalling due to the corrosion of rebars
should be also considered, but this will be rather unlikely, as the core of column shall be unaffected, and the local loss of section would create a "Freyssinet
hinge" contained by the vertical rebars and stirrups, or the remaining parts of these. The following is an interesting and likely related quote from a research paper
"Damage of Concrete and Reinforcement of Reinforced-Concrete Foundations Caused by Environmental Effects" published by Procedia Engineering as open access article:

"Salt weathering"
This occurs in concrete due to the capillary rise of water rich in slats through the soil and foundation structure. It
is prevalent in the areas with the considerable concentration of chlorides in the soil, ground water and atmosphere,
which is mostly the case in the coastal areas of the warm seas or in the structures where defrosting salt is often used
414 Zoran Bonić et al. / Procedia Engineering 117 ( 2015 ) 411 – 418
(road structures). Nevertheless, the mechanism of the crystallization process is similar to frost action. Namely, the
pressure caused by crystallization brings about the onset of cracks in the pore walls and afterwards the cracks, due to
crystallization in them grow bigger. This process, in presence of new amounts of water rich in salts, continues,
causing massive concrete degradation. The basis of this process is the reaction of calcium chloride (CaCl2) and
sodium chloride (NaCl) which causes changes in the Portland cement and causes generation of calcium hydroxide
(Ca(OH)2) [5].
This kind of concrete degradation, known also as chloride aggression, is particularly prominent in those cases
when the structures are positioned near the warm seas, in the conditions of high concentration of chlorides in the sea
water, soil and air. Warmer climate, in comparison to the areas with the continental and temperate continental
climate enhance salt weathering. In addition, high temperatures have an additional detrimental effect because
concretes, for the reasons of better workability are made with a high water/cement ratio which causes, in the
concrete hydration process, an increase in the concrete paste porosity, which facilitates capillary rise of chloride
saturated water after concrete hardening. The higher temperatures are the cause of the faster initial hydration of
cement which leads to the increased porosity of concrete and facilitates capillary rise and crystallization of chlorine
ions"
Full article is attached as pdf file.

• https://files.engineering.com/getfile.aspx?folder=f9bd48ff-443d-4c2f-9a5f-c

8777 COLLINS AVE-1979 PLANS:

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


8777 COLLINS AVE - Structural Field Survey Report:

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

8777 COLLINS AVE - Unverified Inspection Report:

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

All Records:

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

The reports go some way to suggest a lot of durability issues.

Not looked at the drawings yet but I suspect you'll find why that's the case....

Those bars ripping out of the underside of the slab is quite extraordinary, never ever seen that previously on any other structural collapse. Usually you see fractured bars not delamination areas like this. Very odd.

https://engineervsheep.com

Some of the most important drawings are conveniently missing - the piling plan, type of the piles used (looks like "Franki" piles), diameter, and the most important the location and exact composition
of the foundations - the beams listed suggest that some of the columns were supported by them, and that's adding to the list of potential mode of failure. It's also worth of noting that the level of the parking garage is below the sea level, so it's making the columns bases located in the "splash" zone and subject to accelerated corrosion and salt weathering of concrete. Unfortunately all of this is not a subject of 40 years' certification investigation, as the most important are the roofs and AC units.

The possible subsiding mentioned above is easy to observe in this image. Link to image so you may view at full size.

Link

8" thick RC flat plate to typical floors.

9.5" thick RC flat plate at ground floor.



EDIT: No obvious column transfer conditions to the ground floor level See post below.

Typical floor dimensions and column layout to the collapsed area:




Basement dimensions and column layout to the collapsed area:



Very 'light' on structural walls for lateral in E-W direction!

3,000 psi concrete from Level 9 floor to roof level - oh, the 80's!!!

Sorry, I spoke too soon, punched columns are visible in the region, so depression does not indicate ground subsiding.

Link

Quote (wiktor)

Some of the most important drawings are conveniently missing - the piling plan, type of the piles used (looks like "Franki" piles), diameter,

Whilst drawing S-3 PILE CAP DETAIL PLAN appears to be missing (or out of order in the many documents) drawing S-11 has this note:

There is a 'planted' column (from all typical floors over), however it is supported by 24"W x 42" deep transfer beam/s at the ground floor:


Typcal floor part framing:




Ground floor part framing:

Maybe these drawings are not as-built / for construction drawings?

Compare the photo and the layout, the area hatched in blue is not built.

Something that wasn't obvious to me before. The entire site's at-grade slab was elevated, and a large portion collapsed, essentially all the way to the pool and to the property line, even though the collapse of the tower was 100' or so away from this extent of the pool deck. It is remarkable that the remaining building didn't collapse as the elevated slab supporting the parking of the cars in the images failed and dropped a level, leaving the still standing columns with an unbraced height which is double of the "design" condition.

Champlain Towers Town of Surfside Public Record LINK...
https://townofsurfsidefl.gov/departments-services/...

Champlain Towers Plans LINK...

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

Are there structural drawings of that transfer beam BM35?

I am on my phone and it does not want to open such a large PDF

Discernable column remnants?

• https://files.engineering.com/getfile.aspx?folder=ab3ad243-1d57-43f7-b074-8

That area near the pool does look like subsidence or a slight depression.

Is there a garage underneath?

Quote (Kreemerz ..garage..?)

Yes, but not under pool itself. The small spa drained into the lower level? Columns to lower level can be seen on pool deck area.

See Ingenuity (Structural)26 Jun 21 02:3 for image taken from below the pool deck.

Quote (gusmurr)

Are there structural drawings of that transfer beam BM35?

Beams BM33, BM34, and BM35 are in the attached beam schedule.

Stirrups in BM33 and BM34 look odd to me. Seems like the shear would be nearly constant on each side of the point load.

• https://files.engineering.com/getfile.aspx?folder=a0801186-4cc3-4f5c-9baa-f

Looks like PFI - Pressure Injected Footings were the deep foundation system (S3 typical piling section) ?

https://www.keller-na.com/expertise/techniques/fra...

In my opinion, the collapse looks like it initiated somewhere between grids H-N. The area with the transfer beams was part of the secondary collapse.

CONFUSION?

Foundation drawings shows PIF's (pressure injected footings). Then call out 14 x 14 precast driven to 50 tons (100 kips).

14x 14 precast are usually driven to 75 kips and I doubt that they would ever be used at 100 kips in South Florida.

Likely Franki or other PIF's at 100 kips. Franki's were being used in South Florida in that time period.

Videos show what appears to me as a failure that started at or near the bottom of the building.

Without speculating as to the cause, which would not be ethical as I am not involved, I would pursue the question of column failure at the
garage level as suggested by others in this forum. Photos show corrosion and indication of previous flooding of the garage which is accordance
with resident reports.

Was the concrete remediation started? Had garage columns been chipped to repair without multi floor shoring? Had past repairs to the columns been made?

Remediation plans call for no more than 1/4 of a damaged column be repaired at one time and call for shoring.

Mojojohn

There's a TV news interview out there of with 3rd party testimony from someone on the phone with a victim who was complaining right before the collapse about the pool patio area sinking. (Edit 6/26/21: I am referring to the video link posted by Jon43442, above, where the interviewee at 1:30 says 'She was on the balcony on 4th floor and she was telling her husband in a frantic way that "the pool was sinking, the ground was cracking," ... "The pool is sinking. The ground is shaking" ... "The building's shaking! The building's shaking" and then she screamed a screech and the phone went dead.')

It's actually pretty plausible that a patio slab failure could have been the initiating event here:

There is otherwise not a whole lot of reason why the collapsed portion of the building zone should have caused as large a portion of the patio to fail as it did. Water ingress through failed waterproofing in the patio area could have damaged rebar connecting columns to the slab leading to shear failure and a single initiating punch-through of a single column. Such a punch-through could overload neighboring columns with similar damage leading to a cascading collapse in the patio zone.

The suspended patio would now have very high tensile stresses in its rebar with the rebar acting like the cables in a suspension bridge. The rebar on the bottom (east-west oriented) seems to have torn out relatively easily, relieving those stresses and potentially saving the southwest corner of the structure and making the load be carried in the north-south oriented rebar.
The extreme tensile stresses in the north-south oriented rebar from the collapsing patio would mean that the patio level slab, instead of providing lateral stabilization to the columns in the portion of the building that failed first, would instead be destabilizing those columns.

From the perspective of the patio slab, the (relatively) stiff intact columns become stress concentrators for those tensile stresses. The columns under the building proper, probably bigger and better protected from water/corrosion than those under the patio, would be less likely to have punchout failures and more likely to transfer the tensile loads into the sides of the columns. Now we have highly loaded vertical columns with a significant sideload. It would only take one of these to buckle to initiate the major collapse. I am thinking of our undergraduate mechanics of materials lab where students put a rod in compression and then tap it from the side and it buckles instantly. With few internal walls, such a single column failure may have been enough to destabilize the larger structure.

Where do the call out 100 kip driven piles?

The PFI call out on S3 is for 300 kips

General Structural Note #3 on S11 spec's precast piles to 100 kips. FYI the North Building is included in the PDF, and there are differences between the two.

799931

Page S-11 notes state 14 x 14 at 50 tons.

A couple of observations... it appears there is a lack of concrete cover to the reinforcing... bad news if there are chloride corrosion issues... also the 40 year inspection report was developed to expressly eliminate this type of failure.

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

-Dik

Quote (As I just learned (and shared the link above), the instigating event behind Miami's 40 year recertification process was the collapse of the Miami DEA building in 1974, which was 40 years old at the time. The Miami-Dade engineer behind the effort saw the particular vulnerabilities of aging structures in the area, and was determined to create a process that would help prevent future collapses.)

40 years may be too long a stretch... maybe 20 or 25 years would be more appropriate considering the 'corrosive' environment...

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

-Dik

Slabs seem awfully thin, at least by today's standards for mild-reinforced flat plate construction. And no drop caps? I see square/rectangular regions shown in hidden lines circumscribing the columns on the original CDs, but no specific annotation indicating the presence of an actual thickened feature. No stud rails or comparable shear reinorcement either, apparently (though probably a bit before the time of stud rails).

The sensitivity of a punching shear mechanism is well-documented, with transfer of unbalanced moment at the slab-column joint component always requiring close consideration in addition to the direct two-way shear component. Eccentricities and misalignments in the concrete frame, whether subsurface settlement/subsidence-related or otherwise, only serve to magnify the system's sensitivity.

Just seems like a confluence of a lot of less than ideal attributes: subsurface element performance/displacement, a comparatively sensitive structural system (two-way flat plate, not to mention some big-time transfer girder elements down low), and an unforgiving coastline exposure.

I have read through this entire thread, so I think this is new information here but my apologies if this is already been posted. A link to a story originally on the New York Times from The Drudge Report says that an engineer warned in 2018 that major structural repairs to the pool deck area were required. This work was designed and ready to be performed. This gives new understanding to the condition of the building that needed to be addressed.

Engineer Warned of ‘Major Structural Damage’ at Florida Condo Complex in 2018
https://dnyuz.com/2021/06/26/engineer-warned-of-ma...

As has been suspected here the report documents a lot of cracking and concrete deterioration due to environmental damage. And has been noted before many complaints by the residents of water intrusion. Waterproofing near the pool had failed and was contributing to the environmental damage, partly due to poor design where water had nowhere to drain to.

Quote (Ingenuity)

The potential unzipping of rebar may have commenced at a construction joint - the rebar was developed into the slab portion that collapsed, and as the slab/s fell it ripped/zipped the reduced-cover rebar in the span that remained. Notice how 'clean' the exposed slab edge at the roof level.

I can’t help but draw a parallel to the Hard Rock collapse in New Orleans, where a design flaw created a weak plane that inadvertently allowed a section of the building to collapse without dragging down the rest of the building.

Somebody speaks out...

https://www.cnn.com/videos/us/2021/06/26/structura...

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

-Dik

New information

https://www.dailymail.co.uk/news/article-9728053/M...

I'm SUPER SUSPICIOUS about that central chase with elevator/stairs/utilities. That wall is the failure plane and those shafts are definitely part of the shear transfer. I must have had at least 20 projects where the transition point between slabs and shafts are a total mess during rebar inspection and require lots of extra work to keep going.

The problem apparently existed for several years...

"SURFSIDE, Fla. (AP) — The oceanfront condominium building that collapsed near Miami had “major structural damage” to a concrete structural slab below its pool deck that needed to be extensively repaired, according to a 2018 engineering report on the building.

The report was among a series of documents released by the city of Surfside as rescuers continued to dig Saturday through the rubble of the building in an effort to find any of the 159 people who remain unaccounted for after its collapse."

Anyone able to obtain a copy of this report?

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

-Dik

NYT Article indicates that column cracking was epoxy injected, but cracks reformed directly adjacent. That to me is a pretty clear indicated that the root cause of the cracking still existed. If there was embedded and ongoing corrosion of the rebar for the columns that wasnt addressed in 2018, that may be a contributing factor.

I see from the drawings there is a transfer beam as well, I have not looked at the shear reinforcement in that area, but if the reinforcement is corroding in the below grade beam, but if the Vs value drops due to corrosion of the ties, that could be a source of concern as well.

dik, here is report you requested.

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

Thanks jrs... I have that one... apparently there is a report of far more serious damage that seems to have been missed/overlooked in the Morabito report.

Maybe the're the same... I got the impression that the 'second' report was more comprehensive... I didn't get that from the Maratibo report.

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

-Dik

There is a difference between designing a building and maintaing one, the design/build/inspection system works. Unfortunately the maintence of these structures are left to property management companies that do not have to show that they have the knowledge to maintain the structure or its systems.

Now for rant (I apologize)

The fact that column was not shored immediately, to study the cause of the distress makes me extremely frustrated. Buildings, do have problems but when a visible issue is not investigated for 3 years, someone needs to go to prison. The lack of accountability drives me nuts, for example.

1) I' am not a Electrical Engineer, but yet I know that the Switch Gears need to be greased and maintained.
2) I' am not Mechanical Engineer, but yet I know that cooling towers need to be cleaned.
3) I'am not a specialty engineer (elevators) but I know that the motors and cables need to be maintained.

There are many things that I personally am not qualified qualified to do, or in the case of the switch gear (too afraid to do) but yet it is pretty simple and inexpensive to find a qualified professional maintain the systems.



/

dik, This might offer clues: https://www.classaction.org/media/drezner-v-champl...

That class action was filed less than 24 hours after the collapse. While legal action is inevitable, and surely is warranted at some point, less than 24 hours is barely enough time to write the submission let alone vet any of the claims it makes. Moreover, if it was your family in the building would your first instinct, less than 24 hours after collapse, be to get a class action lawyer involved?

Makes me sad. What an absolute tragedy (what happened and what will happen).

Question for the SEs: i've got a "can you design this building like this under todays codes?" question.... Specifically, can the stair tower in the far wing NOT be designed with just 1 shear wall? Isn't there some limit to how much open floor plan you can have before you connect to a shear wall? (Seems like there should be, just sayin') The video shows the building dropping up against the central shaft first.... then there is a delay and far end of the wing becomes unstable and drops. I wonder if that stair tower had been a full rigid box could it have done the job of halting the progression and saved a third of the lives???

I'm on the HOA board of a 130 unit property. It's probably rare for an engineer to be on such a board. The horror stories are true.

I have family in an old low-rise condo down there. One of the buildings near the water was settling badly, and they reached out to a foundation repair contractor. I then received a call from one of the board members, who thought their proposal of four helical piles was way too many and they could get away with two.

These condos are full of cheapskate board members who think they’re engineers. And the owners don’t understand that these coastal RC structures have usable lifespans. As they age, repairs (and special assessments) will get more frequent, until the building becomes uneconomical to repair and must be demolished. I predict that in the coming decades, you’ll see older units become essentially “free”, with astronomical fees to fund repairs.

@Dik
Structural damage from what?! Good grief....

Kreemerz, are you going to be a troll?

Yeah, I'll chime in that I mostly do forensic structural engineering and repair design in my career -- I'll add to SocklessJ and JRs87 statement, that anecdotally Condo boards and HOA's are often the least versed clients (present company not withstanding) and often the most cost conscious we/I have. For commercial properties, there are some property management companies that have the stuff well handled and communicate wtih ownership very effectively to get things repaired and done. Other property management firms get pummeled by ownership and defer repairs because they cost money.

engineer WARNED ABOUT DAMAGE
https://dnyuz.com/2021/06/26/engineer-warned-of-ma...

https://www.miamicondoinvestments.com/champlain-to... is a near carbon copy.

jrs... doesn't work... I are thick skinned.

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

-Dik

I still can't get over how cleanly that structural steel unzipped from the floor slabs. It reminds me of what you might see when pulling electrical wiring out of drywall. There is definitely some compromised concrete here.

One way or another, you can bet the City of Surfside & the developer of the newer property next door are going to be dragged into whatever legal wranglings arrise. There used to be a public street/parking lot for beach access between the two properties. Now there is just a walkway for beach access, with the remainder of the former street providing a trash enclosure, landscaping and some other enclosure. I assume below all of this is underground parking. Surfside also has a parking lot for beach-goers across the street.

Quote (TheGreenLama (Structural)26 Jun 21 17:25)

clean rebar

Perhaps the unzipping occurred at a very high velocity. The unzipping was secondary to the collapse, as corroded bar would not unzip like this.

A lot to unpack here...

Someone should investigate whether (in an attempt to appease today's multi-vehicle families) the parking structure was reconfigured from the original layout to pack more vehicles in, exceeding the original design's specs.

Even if it wasn't changed I have to believe the load on the parking deck was more than it was in 1981, despite some cars being lighter. The number of crossovers, SUVs, and pickups owned today cancels out any weight improvements in sedans and other small cars. And that doesn't even take into account electric cars, which are a lot heavier than their 1980's counterparts.

The timing of the collapse is interesting. Do bars still close at 1AM like they did when I lived down their in the 70's and 80's? As suggested earlier in this thread, it wouldn't be much of a stretch of the imagination to think that someone who had too much to drink mistook the accelerator for the brake pedal and plowed into a column, dropping the already weak deck above them and causing a cascading failure due to all the other problems this building had. Was there CCTV coverage of the garage and did the server survive? Regardless of what triggered the collapse, that would be some interesting footage indeed.

A column being taken out under the pool deck could explain the "sinking" that was reported just before the collapse. If it turns out it did start under the pool deck, it's criminal a part of the structure that has no bearing on the rest of the building could "tug" enough on the columns where the collapse occurred, causing them to snap in half and causing a catastrophic drop of the deck under that part of the building - and as has been speculated already - the lack of lateral support causing a cascade event of columns buckling.

I'm shocked by how easily the deck sheared from the columns and how cleanly the column rebar pulled out of the deck in the section where the building managed to remain standing. Those residents are extremely lucky - the only thing that saved them was the parking deck cleaving cleanly from itself, leaving the rest of the deck aloft to provide the necessary lateral bracing.

The piss-poor rebar placement is just as shocking. Perhaps someone thought because Florida doesn't have earthquakes the possibility of rebar unzipping from the bottom of the deck was highly unlikely? Perhaps even thinking the more concrete above the rebar made the rebar less likely to unzip from the top of the deck where it mostly mattered? I suppose the most likely reason for what we are seeing is a rushed construction schedule which prevented workers from properly positioning the rebar in the middle as it should be.

The building seemed top-heavy to me, especially from the slow twisting path the last section took during its fall. There's no excuse for that section to remain standing and then fall soon after. A building should be able to stand even if an entire row of columns is compromised. It's interesting the part that fell had a penthouse addition added after the initial design. It also doesn't help non-structural concrete block was used as sound and fireproofing. That's a lot of extra dead weight the structure had to carry.

And finally it's being revealed the building actually did have major structural issues that needed to be fixed, which only compounded all the issues (and possible issues) above. It is unfortunate it was procrastinated upon for 3 years until it was too late.

Quote (darthsoilsguy2)

Question for the SEs: i've got a "can you design this building like this under todays codes?" question.... Specifically, can the stair tower in the far wing NOT be designed with just 1 shear wall?

No, you can not! The structure doesn't have sufficient shear walls parallel to the numeric grid.

The design wind load for buildings located on the coastline is very high. Note, I'm not saying that is the cause of the collapse, but the drawing shows only two 8ft long shear walls to fend off a high-velocity hurricane zones wind pressure x the building area facing the ocean(150ft x 117ft)? You can't make this work.

@Jrs87
Why are you calling me a troll?

What's that all about?

Dik mentioned that there was a report in 2018 that mentions 'structural damage'. As a Californian, I usually only hear of structural damage caused by seismic activity.

How do I reply with a quote? Maybe that's why @jrs87 is not clear on my question.

I wonder if the construction crew was primarily from Central America.
During my time in Central America I observed the following construction sequence many times.
1: Low slump is your enemy. Concrete was typically mixed with almost no very high slump so as to be easy to place.(Corrected)
2: Re-bar is often laid directly on the forms for elevated floor slabs.
The wet mix leaves the concrete very porous.
Moisture attacks the re-bar and corrodes it.
Iron oxide has more volume than the original iron, and the expansion due to corrosion blows the concrete from the re-bar.
A common sight in older buildings is a concrete ceiling with the re-bar grid exposed and rusty.
A friend of mine was having a new house built. The design called for a cantilevered shade deck over the entrance to the garage.
When the contractor started to remove the forms, the deck started to subside.He tied it back to a parapet wall with cables and turnbuckles.
I was asked to look at it. I remarked that an overhung deck would not be supported by rebar lying on the bottom form. The re-bar must be higher in the slab to be effective.
The owner talked to the engineer and reported back to me:
"The engineer says that the re-bar must be on the bottom to keep the concrete from falling."
Without close supervision, a crew with southern experience will tend to revert to the way that they were originally taught, which is also easier.
I would suggest that the lower the wages, the more supervision is needed and the more suspect will be the concrete quality and the correct placement of the re-bar.

My favorite for the all time worst re-bar placement was a narrow roadway up a side hill.
The roadway was graded and the re-bar was laid directly on the ground. Then construction traffic ran over the re-bar for a week or so.
Then the concrete was poured with no attempt to lift the re-bar up out of the dirt.

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

Quote (waross)

Concrete was typically mixed with almost no slump so as to be easy to place.

'No slump' concrete is very difficult to place - I think you mean high slump concrete - like 8"+ slump.

With today's admixture technology, concrete with a large slump can be ready-mixed without reduction in strength nor durability - not so much in the 'evil-80's'.

"FEMA was ready to deploy to the condo collapse almost immediately, and included the crisis in its daily briefing, but didn't get permission from Gov. DeSantis to get on the ground for a full day." source Link

Kreemerz, no offense was meant, I assure you. I asked if that was your intent, that is different than calling you one.

There is a toolbar with icons in the editor that help you form your post. The term "Good grief..." in this neck of the woods is sometimes pejorative and mocking.

Hope, we are past this now with no worries and back to the subject.

P.S. Corrosion is form of energy like seismic activity. So corrosion plus gravity equals structural damage. Right?

The planted column Ingenuity pointed out is interesting, it seems like it would take a few structrual irregularities like this to fail in order to bring a stucture down so quickly.

Would be interesting to see if any of the damage/corrosion from the 2018 report affected any elements in that area.

This still just so hard to believe, I would expect more load redistrubtion and large displacements before full collapse on a RC structure (even if the engineering/construction is suspect).

Slump tests are extremely important, because it is the only to know if the aggregate is incorporated. Plasticizers are necessary to make hot mixes both deliverable and workable.

• ]]]

Here's an interesting post from YouTube, it's the initial fire department radio traffic from the initial response. How cool the responding units are is truly impressive.
Miami FD communications

Help. Has anyone been able to find the plans for the new penthouse and replacement AC unit? Thanks.

SF Charlie
Eng-Tips.com Forum Policies

Quote (Kreemerz)

Why are you calling me a troll?

Welcome to the board. Don't be disheartened. I was slammed hard for my very first post a few years ago. We have some spirited discussions here.

Brad Waybright

The more you know, the more you know you don't know.

Yes, welcome Kreemerz

Focus shifting to long term pool leak.

https://www.dailymail.co.uk/news/article-9728053/M...

Here's a reddit thread with extensive details of the camera, witness, and survivor locations within the building: /r/CatastrophicFailure.

Quote (warrenslo (Structural)26 Jun 21 01:48)

Thanks for the photos. I know what it takes to dig these out.
To me, it looks as if they not only replaced the AC, but also changed it's location???

SF Charlie
Eng-Tips.com Forum Policies

From 8777-collins-ave---unverified-inspection-report:

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

Inspection done between 8/01 and 9/06/2018:

"2.Settlement: Good – no building settlement observed"

The city's major concern was interior lighting being bad for turtles at the seashore. (reddit)

According to this report, there is nothing wrong...

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

-Dik

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

I've seen several posts referring to the changing of the rooftop HVAC. While that's very obvious in the photos that have been posted just because a new unit is larger doesn't mean it's heavier. In many cases newer HVAC equipment, as well as many other types of equipment, are much lighter these days because of new materials and "value engineering". It's certainly something that needs to be looked at but certainly isn't a smoking gun IMO.

Something is not adding up. Pool deck and garage seem to not have been on the agenda. Roof and facade were.

https://news.sky.com/story/miami-building-collapse...

The interior columns have over 500,000 pounds of dead load in them. Assuming a conservative safety factor of 1.2, while it wouldn't meet code, the columns should be able to support an additional 100,000 lbs of load before failure. I don't feel that an RTU would cause a collapse of this magnitude. Failure of the pool deck or garage slab causing an increase in unbraced length seems more plausible given the deferred maintenance.

The take away from the Reddit thread is that there was a collapse in the garage 2-3 minutes before the whole things came down. It was felt by the resident of unit 111 at 1:19 am. There was a larger jolt and shaking that prompted the family to evacuate the unit and flee the building. The catastrophic failure happened at 1:22.

Sounds like there was a column and slab failure in the basement with a few minutes of load redistribution before there wasn’t anywhere left for it to go.

Security video of higher quality and starts a second or too earlier.

https://www.reddit.com/r/CatastrophicFailure/comme...

Just for the record, Epoxy Injection of cracks resulting from corrosion of rebar, is not a viable solution to repairing the crack or remediating the corrosion. It is just kicking the can down the road.

Nearly all of the upper-level columns in the remaining portion of the building sit on transfer beams between the first and second floors.
The three exposed columns where the parking slab fell (J12, J14, J15) are larger than necessary for architectural reasons below the second floor, likely why this portion of the building did not collapse.



The columns in the collapsed portion were at minimum dimension all the way down, hence they would be first to fail with deterioration, settling, etc.
ALL of the columns in the initial collapsed portion are Type C at the exterior and Type G at the interior.
These columns have quite a bit of rebar at the lowest levels 12 x #11 in 16 x 16 (Type C) and 10 x #11 in 14 x 18 (Type G.)
Both types near the maximum reinforcement ratio, once concrete spalling occurs they would theoretically be over code allowed ratio and need to be strengthened.
But, they weren't strengthened due to parking, to enlarge columns reduces parking space size or the space altogether, so the HOA technically wasn't allowed due to zoning laws.



In addition, they appear to have been overloaded. According to the plans provided, the columns were not designed for the penthouse addition.
The column schedule mislabels floor 12 as the penthouse.



The penthouse addition drawings show the penthouse at the roof level or floor 13 (the elevator to the penthouse from floor 12 does not appear to have been added, instead the corridor was extended to the main elevators.)
The area under this corridor collapsed first.



Finally, the recertification documents note the structural steel supporting the HVAC system had isolated rusting.
Failure of the HVAC steel would have caused exactly the type of collapse we saw (see my prior post above.)




-W

I wonder if the column with the wide crack was along column line 10, where the failure originated?

Quote (warrenslo)

Finally, the recertification documents note the structural steel supporting the HVAC system had isolated rusting.

The question is when was that review of the supports for the HVAC done. Considering we have documentation that the equipment was replaced within the last 2 years it seems hard to imagine that the supports would be in that bad a condition that rapidly.

Quote (warrenslo)

Finally, the recertification documents note the structural steel supporting the HVAC system had isolated rusting.

The review you quote showing rusting of the HVAC system was supposedly done between 8/01 and 9/06/2018 but was not received by the town of Surfside until "5:35 PM on June 24, 2021."

Otherwise, I agree with you. Maybe the unit wasn't anchored properly and a jolt loosened it, so that it wasn't the trigger but it helped precipitate the collapse. The reddit thread said there were two jolts about 3 minutes apart. Alternatively, it simply fell when the building fell and it wasn't involved in the collapse. Corrosion failure of an overloaded structure wouldn't be surprising. If the margins of safety had been greater, maybe many lives might have been spared. Finding that the columns weren't designed for the penthouse addition is a smoking gun.

IEGeezer: Beginning of the report says: "This report was not formally submitted or authorized by the property owner Champlain Towers South Condominium Association, Inc., as required by Section 8-11(f)(iv) of the Miami-Dade County Code."

Quote (Warrenslo)

IEGeezer: Beginning of the report says: "This report was not formally submitted or authorized by the property owner Champlain Towers South Condominium Association, Inc., as required by Section 8-11(f)(iv) of the Miami-Dade County Code."

I saw that also and wonder who paid for and authorized the study if it wasn't the Condominium Association?

warrenslo: You are correct. That's why I said supposedly. Providing a report two years late and hours after the collapse raises eyebrows.

Quote (Mark R)

I saw that also and wonder who paid for and authorized the study if it wasn't the Condominium Association?

It looks to me that Morabito submitted it after the collapse, but originally prepared it alongside the 2018 report he did for the Condo. I'd guess he sent it in to be as helpful as possible and avoid any appearance of concealing anything from the investigation.

On the rooftop HVAC unit, I don't believe it's at the root of the failure. The photo of the steel frame corrosion in this unauthorized form report doesn't look severe enough to fail in 3 years. The location, directly north of the elevators does not fit with the start of the collapse in the security camera looking across from the new building to the south. The collapse of the upper levels appears to initiate around the x11 apartments and ramp to the parking garage, in the middle of the wing. The section closest to the elevators appears to be pulled into the collapse later, presumably pulling the HVAC unit and frame down with it.

"Gabe" from apartment 111, directly over the lower end of the ramp, seems to be saying that the pool deck slab out in the open had visibly collapsed while the building was still standing. He was able to escape with his family after seeing that, before the collapse. That progression doesn't really fit with the new HVAC unit being at the root. It suggests that the exterior pool deck failed at a column, progressed towards the x11 apartments, then pulled out a column or two below apartment 111.

Quote (Murph 9000)

Quote (Murph 9000)

On the rooftop HVAC unit, I don't believe it's at the root of the failure. The photo of the steel frame corrosion in this unauthorized form report doesn't look severe enough to fail in 3 years. The location, directly north of the elevators does not fit with the start of the collapse in the security camera looking across from the new building to the south. The collapse of the upper levels appears to initiate around the x11 apartments and ramp to the parking garage, in the middle of the wing. The section closest to the elevators appears to be pulled into the collapse later, presumably pulling the HVAC unit and frame down with it.

The HVAC unit was replaced with a larger and most likely heavier unit in a different location after the 2018 inspection.

Do we know which column on the x11 stack failed? Assuming it was a corridor column as the collapse seemed to start there. Those columns had an extra floor added to the roof for the walkway to the penthouse addition. The corridor column part of the collapse furthest to the east had both the penthouse walkway and HVAC frame added to it.

-W

Thanks for the catch, ingenuity.
Correction made.
Central American concrete. I once pulled over too far to the right and my door and rocker panel clipped a concrete pedestal that had once supported a lamp standard.
There was little damage to my truck. There was a lot of damage to the concrete.

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

The only design flaws in this building that I can possibly see is a lack of slope and water infiltration on the parking deck. This is not an engineering problem, it is a licensing and accountability problem. For the most part every issue that caused this structure to catastrophically fail could have be easily been remediated.

If a column failure, or major deck damage is documented and not addressed for years someone needs to go to prison. That column alone should have been immediately shored up, ask questions later.

This was an entirely preventable event, thank god for extremely conservative redundancy factors, or we would see alot more of this.

Quote (warrenslo)

Do we know which column on the x11 stack failed?

I don't think the current public evidence gives any certainty around that. To me, the security CCTV from the south makes it look like the K,L,M columns were first to go in the upper collapse, probably rows 4,8,10 (I'd guess row 10 first, but it might have started at the corridor row 4).

The red HVAC support frame looks to be the same for both old and new. It appears to span E & H columns in rows 2 and 4. There's also the I series of columns between it and where I believe the earliest upper collapse is visible.

There's a fair bit of interpretation / guesswork above, trying to interpret the distant CCTV image which is looking diagonally across to it and it's all very quick. We can't rule the new HVAC unit out as one of many contributing factors, it just doesn't look to me that it was at the root of the failure or part of the early progression.

I'm all in with @sdh4 on the patio/lobby/pooldeck slab being the initiator here. Obviously there were concerns/evidence of corrosion in the pool deck slab. And multiple eyewitness accounts indicate that the "pool area" slab had dropped one or more panels prior to the superstructure collapse.

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.

See attached snip from the lobby level slab. A couple of items regarding the yellow area and the column with the arrow pointing at it:
Lets say:
+10'-10" = pool deck level
+11'-10" = plaza level
+13'-4" = lobby level




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.

If the yellow area collapsed first or another area at pool deck level collapsed first then triggered the yellow area to collapse doesnt really matter I suppose. If the yellow area fell at any point I would start looking at some amount of lateral force being applied to the column between two supports (foundation/basement slab and the slab at lobby level).

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.



Also, I highly doubt any sort of mechanical equipment had anything to do with this.

Quote (This is not an engineering problem,)

Having done dozens of parkades... slope and drainage is a real engineering issue.

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

-Dik

The second part of this video seems interesting to me.
The flashing light coming from next to the elevator roof machine room could be from the rupture of the power supply wires of the AC rooftop unit while falling down.

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

"Where the spirit does not work with the hand, there is no art." - Leonardo da Vinci

Quote (jrs87 (Mechanical)26 Jun 21 20:57

The city's major concern was interior lighting being bad for turtles at the seashore. (reddit))

This is the most believable statement in this entire thread.

cute... but there are other parts that are OK, too.

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

-Dik

@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.>

This is exactly the column that stood out to me.... It kinda looks from aerial that it could be where the planter was located 🤔 extra load and water infiltration and maybe not as easy to see during a visual inspection.

The waterproofing may not be a structural issue, but the slope and drainage definitely is a consideration and coordination that should always be considered. Even now I've seen lots of architects try to apply waterproofing to a flat slab and then "slope the finishes"..

Obv lots of speculation at this point, but as engineers our brain is trying to find an explanation to this horrible tragedy.

@missstructures I agree with columns on 9.1 line. Particularly @ I and K line. Both are exposed to planter box at lobby level.

Below is an image taken from a youtube clip on the sister building. The column doesn't look safe with the cracks and concrete spalling.
Surprisingly residents are still allowed to live in the building, given the witnessed catastrophe.

• https://files.engineering.com/getfile.aspx?folder=f3cb725e-0c11-416c-92c8-a

Quote (Engr1888)

Below is an image taken from a youtube clip on the sister building. The column doesn't look safe with the cracks and concrete spalling.
Surprisingly residents are still allowed to live in the building, given the witnessed catastrophe.

That's from https://youtu.be/qTUykkOSLEw

They say that's Champlain Towers East, which is the much newer of the three buildings (1994, I think), which makes it all the worse. Champlain Towers North is the one which is near identical and the same approximate age as the South tower that has collapsed.

That looks about head height, so unlikely to be vehicle damage, it must be corrosion damage. I'm not an expert on corrosion in RC, but up high on the column suggests to me it's probably coming from the slab above rather than rainwater from vehicles. I know how destructive the ocean environment can be, but that's scary. How bad is the pool deck slab as a whole, if that's the state of the columns supporting it?

I certainly wouldn't want to be within a block of that building right now, until it's been properly surveyed (and appropriately shored up / repaired).

Quote (warrenslo)

ALL of the columns in the initial collapsed portion are Type C at the exterior and Type G at the interior. These columns have quite a bit of rebar at the lowest levels 12 x #11 in 16 x 16 (Type C) and 10 x #11 in 14 x 18 (Type G.) Both types near the maximum reinforcement ratio, once concrete spalling occurs they would theoretically be over code allowed ratio and need to be strengthened. But, they weren't strengthened due to parking, to enlarge columns reduces parking space size or the space altogether, so the HOA technically wasn't allowed due to zoning laws.

...

In addition, they appear to have been overloaded. According to the plans provided, the columns were not designed for the penthouse addition. The column schedule mislabels floor 12 as the penthouse.

If this is true for the South tower, then it may be true for the North tower as well (and maybe the East depending on whether the East tower has an added on penthouse also). You can find the "Typical Floor Plan Dimensions" blueprint for the North tower at page 164 of 336 of the 1979 plans. The "Column Schedule" for the North tower can be found at page 171 of 336 of the 1979 plans. The penthouse is also shown on the column schedule for the North tower to be floor 12. Maybe it was added also.

Given the picture of the lower level garage posted by Engr888 (which Murph9000 says is actually from the East tower), maybe somebody ought to consider evacuating the North (and maybe the East) tower until it (or they) can be shored up. Just a thought.

missstructures: To me it looked like the column line along the corridor went first due to the light flashes, otherwise the first portion to collapse would have tipped over more rather than fell in on itself. The rebar pattern also makes it appear a middle column failed. Did unit 101 escape into the pool deck, he had direct access. Finally, the pool itself looks undamaged.

Engr1988: is that North or East. East was built in the 1990s.

I can't comprehend how the other towers haven't been evacuated

I trust it was not constructed like this...maybe it was:



On drawing S-9 (penthouse framing) and S-10 (roof framing) the drawings detail top reinforcing at these column locations.

EDIT: Drawing S-6 (second floor framing) also details top reinforcing at these column locations.

warrenslo: I think in that video clip it was mentioned East.

Concrete strength is 3000psi.

To the current Australian code, since 1988, minimum concrete strength within 1Km of the ocean is 40Mpa (5800psi) because of the exposure to sea spray!

So I would be expecting bad corrosion a long time ago independent of any water leaks.

Typical floor slabs are flat plates, 8" thick spanning a maximum of 22'6", so about 6.9m and it is an end span. I would expect that sort of depth with a properly designed PT slab and 40MPa concrete, not an RC slab.

I do not have the complete drawings and design requirements, but from what I have seen, I would suggest the expected deflection on the typical floors would have been in the order of 100mm (4") if they had been correctly reinforced, and that is doubtful from the details we have so far.

And it would require significant amounts of shear reinforcement for punching shear, which I still do not believe is possible to make effective in an 8" slab and from the drawings I have seen has not been provided.

I still have difficulty imagining a collapse like the one that happened. About 50 years back, one of my few albatrosses, I was asked to put a price in to determine the cause of excessive deflections on a flat slab roof over a parkade. I didn't get the project, but that's another one. The column arangement was unusual, and I determined that a column had been completely missed during the construction and the slab was 2x approx the span in that area. The structure had been in place for a few years. When I see this catastrophic collapse, I have to shake the sawdust out, to try to vision the cause and am surprised that nothing held it together.

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

-Dik

Quote (concrete strength within 1Km of the ocean is 40Mpa (5800psi))

With salt de-icing, I use 35MPa min... with added cover. Does the Australian code have minimum cover requirements?

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

-Dik

dik,

It has stood up for 40 years with its problems! It normally takes a lot more than one problem for collapse, but punching shear is very unforgiving once it decides to go. Pancake failure!

Yes it has minimum covers, but for that exposure it has minimum 40Mpa strength independent of cover.

Quote (geotechguy1)

I can't comprehend how the other towers haven't been evacuated

Unbelievable. How would this even be a discussion?

This "40 years" is a completely arbitrary number as far as i'm concerned. What do the 40yr inspection reports of the other Champlain tower(s) say? Assuming they were built within a short time of each other. Or are they also just waiting a cool 2 years to take action on known issues. Critical issues.

Where does the inspecting PE's responsibility end? I.e., I feel like the findings of this report should have been followed up on. The inspection report has a forensic architecture flavor to it, not so much structural.

IEGeezer: North has a nearly identical penthouse. East was built in the 1990s and does not appear to have a penthouse.

I'm sure every building of that era will be looked at a bit more closely now. I could see even a mass inspection and required retrofit similar to what many jurisdictions in California have recently required.

Quote (dold)

This "40 years" is a completely arbitrary number as far as i'm concerned.

Dr. Atorod Azizinamini, a structural engineering professor from FIU, is advocating a much better approach than 40 years:
https://youtu.be/pex8u5NfWYs

I encourage you to watch his video in full, his thoughts on this disaster are worth your time. The short version, however, is different levels of inspection at 5, 10, 25 years, or something like that; so you have an expert eye taking a quick look far more often, and a detailed examination at longer intervals.

Dik,

I apologize if I seemed flippant about the design of the Parkcade (I really love that term), it was not my intention. What I was trying to convey is that failures during construction, or soon after completion are different than a structure that has been up for 40 years.

I totally agree that the bars appear to to not have has adequate concrete coverage and became unbound to cleanly from the slab/deck. this in not engineering 101. This is a pretty specialized forum, and I think that the general level of discourse reflects that. My point is that there is a huge knowledge gap in understanding structures such as a Parcade between the members of this forum, and the general public.

We are a self regulating industry, and I would wager a $2 bill that several members of this forum are either current active members or former members of at least one code committee.

In my opinion I feel that we fail the public post construction, in terms of inspection, and maintence codes for mid to high rise residential buildings.

There is no doubt in my mind that the people are actually reading this, could have prevented the loss of so many lives.

The type of professionals that participate (myself included) in discussions such as this, are the ones that write the building codes, so in a sense we are all responsible for this catastrophic event.

Here is the original interview with the person who made it out of 111 that @Spartan5 mentioned, He doesn't say where he ran toward but sounds similar to what the lady said on the phone (412) that the 'pool/lobby's deck may have been the initiating failure.
https://twitter.com/OfficialJoelF/status/140798540...


Is there a ok plan showing the apt #s?

News interview from a sister of one of the missing: (from Apt 412)
"Suddenly she says, 'honey the pool is caving in, the pool is sinking to the ground'," "He said 'what are you talking about?'
And she says, 'the ground is shaking, everything's shaking' and then she screamed a blood curdling scream and the line went dead."

Link:
https://news.sky.com/story/miami-building-collapse...

In 2018 MC [Morabito Consultants] Structural Report recommends that the Entrance/Pool Deck concrete slabs that are showing distress be REMOVED & REPLACED in their entirety.

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

missstrucutures, there is not a floor plan with numbers that I am aware of. But this thread explains the numbering system based on what they were able to glean from records and real estate postings:
https://www.reddit.com/r/CatastrophicFailure/comme...

missstructures, about that 1st floor survivor. I would guess that he exited his condo into the interior hallway and ran for the street entrance, which is within the still standing tower. Once he made it into the hallway portion within the standing portion he would have been protected.

Separately, as was mentioned earlier, NIST investigators are on the scene. This from yesterday.

Quote (jrs87)

Kreemerz, no offense was meant, I assure you. I asked if that was your intent, that is different than calling you one.

There is a toolbar with icons in the editor that help you form your post. The term "Good grief..." in this neck of the woods is sometimes pejorative and mocking.

Hope, we are past this now with no worries and back to the subject.

P.S. Corrosion is form of energy like seismic activity. So corrosion plus gravity equals structural damage. Right?

Wow... that's an interesting way of handling being rather direct and potentially hostile to a guest here... calling someone a "troll" on account of them using a commonly harmless idiom that only

might be pejorative or mocking. I've never heard of a such a thing. Good grief is an expression of surprise, dismay, alarm or other emotion. The only one who has the right to be upset might be God since it's derived from Good God...

In any case, thanks for pointing that out. Intriguing.

Thanks for explaining the report's discussion of "structural damage". I wasn't clear on what the report was referring to when they said that. But now I am.

Quote (I apologize if I seemed flippant about the design of the Parkade (I really love that term), it was not my intention.)

No need... wasn't taken as such... I just wanted to let people know that drainage is critcal for parkades... generally to minimise corrosion issues. Also need good expansion joints. You either install cheap ones, or ones that work.

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

-Dik

Quote (Yes it has minimum covers,)

Thanks rapt... in Winnipeg, we typically have one freeze-thaw cycle per year...

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

-Dik

Quote (dik)

drainage is critcal for parkades... generally to minimise corrosion issues.

Corrosion is supercharged in spots where it's constantly damp and constantly exposed to air. You can see this very visibly on steel canal boats. You get a roughly half inch band of much faster corrosion at the waterline; the metal that's constantly submerged is good, as is the metal that's generally above the water. That's with sacrificial zinc / magnesium anodes welded to the hull to slow it down, and reasonable attempts to protect it with coatings. Just giving this as a practical example where you can see it in action.

A flat surface that doesn't properly drain / dry out is creating that sweet spot for rust.

Quote (that's an interesting way of handling being rather direct and potentially hostile to a guest here... calling someone a "troll")

He simply asked if you were being one... Your kurt comment could not have been taken another way, IMHO. I ignored it. Let's drop this.

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

-Dik

Quote (Average car length is like 14-15 feet x 6' wide. Cars this size weight less than 3000 pounds. 40 psf gets you 3360 that's assuming cars are packed like sardines. With the drive aisles spaces between cars, etc. 40 psf is pretty conservative in most parking garages.)

Your typical 'real' load on a parkade structure is in the order of 15psf to 20psf as a maximum load and I use these values for alternate LLs.

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

-Dik

Quote (Dik)

Thanks rapt... in Winnipeg, we typically have one freeze-thaw cycle per year...lol

Surely a slight exaggeration. grin.
We have a couple of months in both the spring and the fall with a daily freeze thaw cycle. The daily freeze thaw cycles for a thermal mass are very much shorter. Is that what you were refering to?
By the way; Does Portage and Main still claim the record for the coldest intersection on earth?

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

Quote (Does Portage and Main still claim the record for the coldest intersection on earth?)

Seems that way.. but, there are likely colder intersections in Siberia, etc. Winnipeg is colder than Moscow...

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

-Dik

A new kid, here.

This topic is (unfortunately) interesting.

I note that two witnesses appear to be saying that the "pool deck" failed first, by perhaps a minute or more. To me, the pool deck is the expanse between the pool and the building. Photos show it surely did drop, by one level, I think.

I propose that by having that floor drop, there was then, for the soon to fall building(s), nothing to keep the intersection of their columns at that same level from moving towards the south (towards the pool deck location). I am assuming a solid sheet of concrete across the whole expanse, and I believe it likely there was a garage under the whole thing. The building could stand until some perturbation caused the sideways movement of those points on the columns, and they fell.


spsalso

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

MJCronin
Sr. Process Engineer

Witness from the next door Blue Green Hotel was lounging poolside when the collapse happened. He said he saw the first floor collapse first (go to 1:20 of video).

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

He would have been blocked from seeing the pool deck by the still standing buildings. It appears it happened and he missed seeing it.

One of the witnesses was in one of the buildings that fell, and said something about the pool area acting funny. So it surely seems like that HAD to have happened first.

spsalso

I'm with sdh4 and dold.... the pool deck could have racked the columns along column line 9.1

That would explain the sudden collapse if several columns were able to fail nearly simultaneously

This would have been view from BlueGreen Hotel next door. They wouldn't have seen pool deck, but he could have seen first floor collapse into the garage first.

Link

The Miami Herald is doing it's usual job of excellent reporting and asking "experts"
See what experts say is the probable sequence of collapse at the Florida condo tower
To go to the 3d model directly:
Champlain Towers South
Less than I expected, but for the time being useful.

SF Charlie
Eng-Tips.com Forum Policies

The National Institutes of Standards and Technology (and it's predecessor National Bureau of Standards) have had a presence in building sciences since it was founded. They have a standing working grout "The National Construction Safety Team" that is chartered with responding to building disasters. This is the team that generated the official report on the WTC collapse.
Nothing specific on the current event is posted on the NIST site yet.

Some quick comments...

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

-Dik

Good photo of the pool deck area post-collapse:

What's interesting about that photo is at it shows the deck dropped straight down instead of pulling away like has been discussed in some of the potential sequences. If it dropped straight down it probably means that it's not a contributing factor to the actual collapse rather it's just a result of the collapse.

The phonecall would indicate otherwise.

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

-Dik

It dropped minutes before the building went down, it was a contributing factor

Quote (dllk)

The phonecall would indicate otherwise.

I agree but physical evidence is much better than evidence from untrained views of the situation while it occurred.

Quote (MJCronin (Mechanical)27 Jun 21 18:16
https://www.townofsurfsidefl.gov/docs/default-sour...)

Very interesting that the majority of structural retrofitting (add drop panels, columns, etc) is in areas that didn't collapse!

It's seems the 40 year inspection system was working. The issues were identified, the plans were being created. I guess the lesson here is 40 years is too long.

Quote (I agree but physical evidence is much better than evidence from untrained views of the situation while it occurred.)

Sometimes, maybe... but the phonecall is pretty solid.

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

-Dik

The building is very close to the shore line. I heard speculation about sinkholes. If that's a possibility, very likely sinkholes may have occurred previously in the lawn fronting the building.

Alleged photo of cracking on first floor from Jan 2021 Google Street View (though hard to really see).

https://imgur.com/gallery/lvlxnr6

A resident on the 6th floor (unit 611 in the first portion to collapse) was awoken by the initial ground level failure, saw a two-finger wide crack run up the wall, and managed to get out of the building before it collapsed.

Quote (NY Post article)

Monteagudo, who is in her 50s, woke up from a restless sleep and heard strange noises. She initially believed they came from the open sliding door to the oceanfront balcony.

“I ran and tried to close it 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.”

https://nypost.com/2021/06/26/florida-survivor-rec...

Video interview (en Español):
https://www.univision.com/local/miami-wltv/tenia-q...

Quote (Mark R)

If it dropped straight down it probably means that it's not a contributing factor to the actual collapse rather it's just a result of the collapse.

Even a perfect vertical drop is likely to do a little damage to the column as the joint detaches. It's not difficult to see a mostly vertical drop giving the columns a little kick or pull at some point between detaching and landing on the slab below. The doubled vertical span has much less safe capacity, and probably has a bit of fracturing at the mid point. There's a fairly big chunk of energy moving around as that slab fails and falls, regardless of the precise way it falls. The column can't just let go of the slab, there's forces and release of both tension and compression as it happens.

If the structural system as a whole was a bit too close to limits, a little extra damage could be all that's needed for the next step in the progressive failure.

Combined with multiple witnesses reporting the pool deck failing first, it's likely more on the contributing than result side of the collapse.

Quote (Jon43442)

Alleged photo of cracking on first floor from Jan 2021 Google Street View (though hard to really see).

https://imgur.com/gallery/lvlxnr6

Hard to see is definitely an understatement! You could have easily seen cracks of some type but you certainly can't distinguish whether they are just cracks in the stucco surface or if they are truly structural cracks.

A timeline for this event is going to be very interesting to see.

It seems that the time of the main collapse could be picked off of the video recording we've seen.

For the pool deck, I wonder if something might show up in the electrical metering record, or maybe some kind of alarm system. I imagine the garage was piped for fire, and that the pipe broke. That might give a time stamp.


spsalso

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?

Dik/Waross,

The terms you use, freeze and thaw and de-ice, are foreign to Australians for construction. Freeze is how we preserve meat. Thaw is what we do before we cook it. De ice is what we put in de glass before de whisky.

Just incredible that people were walking by this on their way to their bedroom without any concern or alarm...

I'd be checking on the ground beneath it to see if there is any debris. That alone would certainly get my attention.

Is this part of the structure that is still standing? or another separate building nearby?

Quote (The terms you use, freeze and thaw and de-ice, are foreign to Australians for construction.)

Same here, as far as meat...

In some northern or very southern (polar) areas there are several months where the temperature falls below freezing 0deg C (32F). At the beginning of winter and at the end, the temperature fluctuates where the temperature is above and below freezing. These fluctuations are called freeze-thaw. With moisture in concrete, this alternate freezing and thawing causes deterioration called freeze-thaw damage. We use air entrainment in the concrete to minimise the damage.

Because of ice on the roads during winter, some places use a mixture of salt and sand to provide traction. This is called de-icing salt. The salt causes corrosion of reinforcing steel in concrete structures. Damage caused by corrosion in minimised by using a high strength concrete, admixtures and thicker concrete cover to the reinforcing.

Hope that explains it...

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

-Dik

Quote (Just incredible that people were walking by this on their way to their bedroom without any concern or alarm...)

or that the matter was not brought to the attention of the authorities...

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

-Dik

Just incredible that people were walking by this on their way to their bedroom without any concern or alarm...

I'd be checking on the ground beneath it to see if there is any debris. That alone would certainly get my attention.
You have to remember that those of us here are engineers, the majority of if not all of the people who lived in this building were not technically oriented people. Thus they had no idea that if I saw stuff like this it was actually a problem for the buildings integrity.

Even if I wasn't an engineer, I would be a little concerned... my problem is that when I'm out, I see things that many people miss, because of my engineering experience... I'm not even looking for them, but they seem to be noticed, anyway. I often spot wildlife, that others miss, simply because of the number of decades that I hunted... and I don't have to be looking for them.

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

-Dik

[link dik] Damage caused by corrosion in minimised by using a high strength concrete, admixtures and thicker concrete cover to the reinforcing.[/link]
Also, in many areas epoxy coated rebar is used to limit the effects of salt on the rebar.

That's one of the curses for being an engineer. A non-engineer notices something like this and wonders what it is, we look and wonder what caused it, what might happen if nothing is done to fix it and if it was going to be fixed, how would you go about doing it.

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

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

Quote (Also, in many areas epoxy coated rebar is used to limit the effects of salt on the rebar.)

that too, there are a couple of issues with epoxy coated bars... the bond strength is diminished, and they are more costly. They do may (see below) work, but you have to use extra care in handling them. Nicking the coating can accelerate the corrosion at that location. Most roadwork and bridgework I've seen done in the last decade or two have used epoxy coated bars. Most regular construction, including parkades use conventional 'black' iron bars.

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

-Dik

Many DOT's and Canadian provinces in the "freeze-thaw" zones have been moving away from Epoxy Coated Rebar.
The theory is that the epoxy coating wears down in the alkali environment of the concrete in about 30 years. Based on the concrete cover used on bridges - about 3" (75mm), but depends on location - it takes about 30 years for the chlorides to reach the reinforcement. So basically, just when you need the Epoxy Coating to work - it no longer works.

Our Concrete people always say that strength = impermeability is old-school. Many DOT's now specifically have permeability requirements and don't rely on the loose relationship with strength. Rapid Chloride Penetration (RCP) is the test done - but it is not that rapid as it usually takes 56 days.

A bit off topic, but most of the bridge decks locally have gone to stainless or low carbon/chromium bars lately, with GFRP bars used in a few places. Epoxy coated bars are now only permitted on low volume roads here.

Burloak and gwynn... Thanks for the added info... I'm of the old school... I think strength has an influence, even if reducing the carbonation effect as well as improving the (im)permeability, and concrete cover, for sure.

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

-Dik

A close-up of the concrete damage at (Sister Tower) Champlain Towers EAST garage.

https://images.wsj.net/im-360760?width=1260&si...

Quote (Kreemerz (Computer)27 Jun 21 21:35)

Is this part of the structure that is still standing? or another separate building nearby?

Do you have the url of the video?
Thanks

SF Charlie
Eng-Tips.com Forum Policies

I have a question regarding the alleged phone call with a woman who claimed to be in the building while she was on the phone with her husband just as this whole thing started.
She reportedly yelled "honey the pool is caving in, the pool is sinking to the ground".

From the recent photos, the swimming pool doesn't look very much like it's caving in or sinking. it looks surprisingly intact.

There is definitely an extensive collapse of the pool deck immediately adjacent from the pool.

And you are paraphrasing a quote of someone who was paraphrasing a quote of someone whose loved one was talking while in the process of being killed by a progressive building collapse that they were trying to make sense of after being woken up at 1:30 in the morning.

What’s your question?

Well, the question was more in regards to what she was describing. I didn't notice the pool had drained. I initially thought she had described the pool as draining. But it seems that she was only describing that it was "sinking" or "caving in". I was trying to understand what she was describing.

Also, not sure where she was in the building.... and how one could see that pool actually caving in.

I'm assuming the story is authentic.

@Kreemerz I think it's safe to assume by "pool" the eyewitnesses were describing the pool area. As in, the entire ground level slab that collapsed as can be seen in the photos. The pool itself had walls extending to the foundation, so it remained intact.

She was in 412.

FWIW, it does look like the very small pool (jacuzzi?) has drained.

There are other reports (which I can no longer remember where I saw them) from employees at the building that minutes before the collapse, they were seeing flooding in the bottom garage level where the valet parking was located. At first I thought it might have been from the main pool, but the image earlier in the topic shows the pool is still full the next morning. It seems reasonable it was the spa that caused the flooding they saw, though it could also be a water line broke if the deck above was in the process of failing.

Also, a former mainentance manager from 1995-2000 who worked at both the South and North towers claims the South tower lower level garage would flood with saltwater during king tides and it was so bad the cars would be floating down there:

https://youtu.be/gh7cnY7PkLU?t=312

He goes on to say the North tower did not exhibit this issue. It's not a smoking gun, but if true, it is another example of there being serious saltwater infiltration issues going on at the property beyond just the improperly sloped promenade deck by the pool.

Dik; I did experience one annual freeze thaw cycle.
The heater failed on my underground stock watering system.
I froze up in the fall and thawed the next May.
The frost goes down a long way and the earth is slow to warm up.

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

Hot, Moist, Corroding Concrete..., what is it they say about every 18 degrees C and the rate of chemical reaction doubles...?

Quote (DavPc (Computer)28 Jun 21 00:49)

Condo Collapse: Former Maintenance Staff Manager Was Concerned About Saltwater Intrusion

Thanks for the URL!

Quote (Kreemerz (Computer)27 Jun 21 21:35)

Is this part of the structure that is still standing? or another separate building nearby?

Please find me the URL, and I'll sleuth it out.

SF Charlie
Eng-Tips.com Forum Policies

Quote (3Engr1888 (Structural)27 Jun 21 03:04)

Below is an image taken from a youtube clip on the sister building

Please do you have the URL of the youtube clip?
Thanks

SF Charlie
Eng-Tips.com Forum Policies

https://youtu.be/qTUykkOSLEw Is the link for the column in the sister building. Someone (Murph_9000) had posted it above. It shows at 1:16.

I see on sheet 96 of 336 (the mixed up plan sets) shows three area drains (referred to as “DD”, Deck Drains?) are indicated in the sloped area surrounding the pool. And the pool is a simple rectangle, no stairs shown. But on later sheets the drains don’t show. The 2018 report indicates that the lack of slope (and drains?) was instrumental in the damage to the deck. However, the 89 sheet set of proposed drawings, Phase IIC, done buy, in part, the same firm that bears name of the engineer that did the 2918 report does not seem to rectify the “flatness” of the area around the pool.
Where are Phase IA, XX, XXX etc plans? Where are the Phase IIA Plans.
I may have used a golf club to “sound” the walls and ceiling, but don’t think I would have mentioned the club, only the results in the report. Rather brings up an image of the inspector wearing golf clothes with white shoes.
Steve

Stevewag, sheet S2C-1.1 shows the overlay to correct deck drainage.

From the Miami Herald.

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



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

-Dik

Former Building Superintendent 1995-2000 mentioned salt water flooding in the parkade was a recurring problem at high tides, king tides. 1-2 feet of water "enough to make cars float around" and the two sump pumps were also problematic and could not keep up, not always working. [CBS Miami]

I looked and tide levels vary about 2-1/2' pk-pk and nothing special that day. https://tidesandcurrents.noaa.gov/map/index.html?id=8723214
Sea level trend +2.39mm/yr https://tidesandcurrents.noaa.gov/sltrends/sltrends_station.shtml?id=8723170

https://youtu.be/gh7cnY7PkLU?t=316

They needed an earthquake to undo some of that subsidence.

The inspector was on the roof inspecting the replacement of roof anchors.

"Jim McGuinness, who made the comment during a Town of Surfside emergency meeting, said he was on the roof to inspect work of replacing roof anchors, which are where window cleaners attach their equipment."

Modern roof anchors are tied to the structure of the building due to the 5,000# OSHA requirement. As far as I understand, there is not a way possible to meet this requirement without tying back to the building structure. The 2018 report noted to install anchors prior to commencing work, this report was flawed, the structure needed to be strong enough to add the anchors prior to adding them. Now, looking at the roof anchor permit drawings, they seem to indicate jackhammering directly into the tops of these overloaded & distressed columns from the roof (see comments above.) This was apparently happening within 14 hours of collapse. Do we know which columns were worked on? If the building was cracking for days why didn't the inspector know.

Finally, the firm that did the structural review of the building also did the structural drawings for this work, I personally think this is a conflict of interest. For example on every project I am a part of I instruct the owner to use a separate surveyor and civil, the surveyor catches a civil error every time (seriously.) They all have the young guys drawing and the older guys are hustling work barely checking. It's simple and important stuff. While we are much more precise than the hand-drawn days, CAD isn't perfect, it's only as perfect as the operator. I can recall the many times I have caught a consultant missing the thickness of a double-sided plywood shearwall. I'm thankful the framers are using Revit now and building a model themselves.

While I'm not part of a code committee yet, I have been licensed for many years, and I feel we really need to simplify the code for younger architects and engineers to understand it, or at least add pictures of what the committee means IN THE CODE! And, existing buildings need more than just a code, we need to force those who adopt IBC et al to review existing structures more often somehow. I have previously worked at an architecture office in Santa Monica where there is visible earthquake damage (cracked beams) and ownership doesn't care. They don't have to, unless they are forced to. This collapse won't be the last unless we fix the process, the boomer days of its standing don't touch it need to end.

-W

Quote (warrenslo)

they seem to indicate jackhammering directly into the tops of these overloaded & distressed columns from the roof

The roof anchor drawings you reference show this detail for the "column anchors':



Two x 7/8" dia percussion drill holes @ 5" deep is not very destructive. Probably drilled with a 30lb electric percussion drill. Also, it is the ROOF LEVEL - highly unlikely the upper level columns were "overloaded and distressed".

I may have an different opinion if they were drilling a lot of holes in BASEMENT columns if there was significant visible distress, but they were not.

Adding to my comment from earlier, Morabito Consultants (structural engineer for the report and the roof anchors) already has prior accusations in recorded lawsuits of failing to calculate live loads in changes of use of a building (in Champlain they were responsible for calculating roof anchor loads and drew structural drawings of the installation.)

"In 1997, on a routine inspection of the building, appellant found significant movement "internal to the building" on the fifth floor. It retained Whitney, Bailey, Cox & Magnani, consulting engineers, to inspect the building. That firm did so and concluded that the design team for the renovation, which included Morabito Consultants, Inc., had failed to calculate properly the increase in live loads associated with the change in occupancy of the building. As a result of the increase in loads, the truss system was overstressed. -- College of Notre Dame of Maryland, Inc. v. Morabito Consultants, Inc., 752 A.2d 265, 268 (Md. Spec. App. 2000)"

https://www.espn.com/college-sports/story/_/id/317...

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 (ESPN)

When they saw dust and debris rising up over the balcony, they went out into the hall and saw two holes where the elevators once were, and saw the next-door apartment was gone. Willis ... made it down 11 flights of stairs

That suggests the collapse started before what we've seen on the CCTV footage.

They were in the portion of the building that did not collapse; directly adjacent to the portion that did.

Quote (air1970)

That suggests the collapse started before what we've seen on the CCTV footage.

That was my 1st thought when I 1st read the article but after I read it a 2nd time I realized that I think they were in the section of the building that didn't collapse.

Quote (alr1970)

That suggests the collapse started before what we've seen on the CCTV footage.

The combined witness statements all point to some sort of failure of the outdoor pool/patio/plaza slab prior to any major collapse involving upper levels. It's hard to say how much in advance, but it seems to be at least a minute or two, possibly as much as 15 minutes for the first signs of it. The CCTV footage from the south that's widely circulated only includes the upper collapse. It would be very interesting to carefully review the preceding hour from that camera for any movement or dust.

Some details don't quite add up, like "holes where the elevators were", since the elevator shaft is still there and appears largely intact. They are not necessarily trying to embellish or be deceptive about it, as this would be them trying to make sense of a chaotic scene with dust and destruction all around. The brain has difficulty processing what it's seeing, and constructs a memory as best it can while running on adrenalin in survival mode.

I think Willis was probably in the surviving section of the building, and the dust was from the main collapse.

He was in the part of the building that remained standing.

Two hypthesises (is it Hypothesi?) I've seen here, I dont think I quite agree with.

1. The Cooling tower at the roof level was changed out. Normally these things are about 20-30 kips for a building this size and distributed over 2-4 columns. For a concrete building this size, and with typical live load reduction - its not likely the cooling tower would over load a concrete column (unless said column(s) was severely deteriorated). I dont think that is likely.

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.

Not sure if this has already been mentioned or not, but ultimately it may be a nonissue since all of the principles involved in the original development are deceased:

Developers of doomed Fla. tower were once accused of paying off officials

https://nypost.com/2021/06/27/developers-of-fla-to...

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

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

Quote (Two hypthesises)

Hypotheses?

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

-Dik

Quote (JohnRBaker)

Developers of doomed Fla. tower were once accused of paying off officials

I'm twice divoced. I've been 'accused' of lots of things.

Brad Waybright

The more you know, the more you know you don't know.

Well, they did make political contributions which later had to be returned. And in one case they appeared to have made a payment which resulted in them getting an advantage over other developers. Also, one of the principles was convicted of tax fraud in Canada and only ended-up in Florida so as to avoid paying what he owed.

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

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

Quote (kreemerz)

Is this part of the structure that is still standing? or another separate building nearby?

That is Champlain Towers EAST, between South and North, that is still OCCUPIED at this moment. Built in 1994, but does not seem to have the penthouse which added load that the columns were not designed for. Even without the penthouse, I'd recommend evacuating EAST and ordering a full structural inspection. JMO