Not Enough Rebar?

Concrete is strong in compression, steel in tension. Once the concrete cracks, salt air attacks the steel which fails, causing the concrete in tension to separate. This is a problem on bridges in cold climates where roads are deiced, but I suppose in warm seaside locations, the ocean spray could accomplish the same thing.

It's also possible that the builder cut some corners and the inspectors looked the other way...

I haven't seen anything written about it, but maybe it should be obvious... Did anybody try calling the cell phones of the missing, starting with the upper floors?

Interesting thought, although I suspect that those layers of concrete with rebar act much like a Faraday Cage, much as my house with foil-lined insulation does.

And of course by now the batteries are all dead.

The problem is noted in the inspection reports....whether that is responsible for the collapse, or it was a series of failures, remains to be seen....a $15 million repair needed sounds rather substantial...

click on "listen to article"

https://www.miamiherald.com/news/local/community/miami-dade/miami-beach/article252385083.html

https://uwaterloo.ca/centre-pavement-transportation-technology/sites/ca.centre-pavement-transportation-technology/files/uploads/files/Carlos_Videla_Seminar.pdf

IMHO:

I don't see any rebar,rusted or otherwise, in the top floors.Plenty of conduits,water pipes,etc from each apartment,but no rebar.

I presume there is none in the lower floors either.

Slow-mo shows the collapse started at the bottom.

They could have used fiberglass reinforced concrete,but still I think in a critical job such as this,rebar should have been required,however I do not know the local building codes.

The rebar aalso has to be positioned properly in the concrete,depending on

the direction of the anticipated load.

As I stated,the building had been settling unevenly over the years,and when the torque exceeded the tensile strength of the concrete,it failed catastrophically.

The corners had the most load concentration and probably were settling more than the rest,creating an unsustainable load on the unreinforced concrete.

It does look like there is rebar around the support columns...

...although it does look like the placement was too near the surface....

In photo #1 of this pair, I see the rebar still has hooks on the ends, with a couple of chunks of concrete still attached, so the concrete cracked away without significantly pulling on the rebar. That tells me it is either poor quality concrete, or significantly degraded.

Anybody who has tried to break up 40 year old concrete knows that concrete gets harder with age, even exposed to water....the rebar does not look badly rusted, so I don't think moisture is the problem...The quality of the concrete seems to be a contributing factor...

Watching the building as it collapses looks like a demolition...in a demolition all the supporting structures are drilled and explosive charges imbedded...so it looks like the infrastructure is just collapsing under its own weight...It looks like a number of column supports and/or floor/ceiling, under the housing located in the parking area garage, collapsed, and this caused a chain reaction of an already crumbling structure....

There is no reason that the second section should have collapsed, other than the vibrations generated by the first section collapse, which shows how close to collapse both structures were....

I actually lived in a 12 story condo on the beach for several years, which was also built in the 80's, by the same construction methods....seems like the concrete was tested periodically, and the patios were renovated while I was living there...It took over a year...they went around with hammers tapping on the concrete listening for hollow sounds, then took an air hammer and busted out the section down to expose the rebar and coated everything and filled it back in, then all the patios were epoxied and surfaced after all the railings were replaced...they did this in the elevator shafts as well...the building was being constantly worked on....

Funny, but my first though was that it actually looked like a controlled demolition - but it clearly wasn't. Your comment "...they went around with hammers tapping on the concrete listening for hollow sounds..." hmm, I would offer a correction, based on experience, they were probably using a Schmidt hammer, or a rebound hammer, if you will, or concrete hammer test. In the US the ASTM C805 / C805M - 18 - Standard Test Method for Rebound Number of Hardened Concrete read with ACI 228.1R4 or BS EN 13791 - we tend to follow the AS/NZ Standards or BS EN and Eurocode's here. The 2018 report mentions none of this

No they weren't Schmidt hammers, I was watching...You could hear when they hit a hollow spot clearly...

Obviously hold contractors in pretty low esteem

There are many methods to test concrete: a scratch test,which looks like a kitched-aid mixer,which oscillates and rotates a carbide (or other) tool against the concrete,and is allowed to run for hours,or days in some cases.

The downward pressure is precisely determined and controlled,as well as RPM.

The depth of the scratch patter is measure to determine the hardness and wear resistance.

The placement of the rebar can be determined magnetically.

A simple magnet on a string can detect rebar,and can be used for a quick test,but the more sophisticated machines can determine dept also.

These methods have been available since at least the '70's,so no excuse for them not to have been used on buildings,especially apartment buildings.

The amount of lime and the proper aggregate sizes determines the quality of the concrete,as well as the age,and whether the concrete was properly cured.

I saw a contractor struggle with a 100+ year old smokestack foundation that had been covered with fill.Jack hammers on track hoes merely bounced around on top of it,barely a dent.After all other attempts failed,a demolition expert was call in,and he used a diamond bit to drill holes in precise locations.

They covered it with about 8 feet of dirt,and when the explosions detonated,there was not even a sound.I thought the detonators had failed,but not so.

When they removed the dirt, only a little smoke wafted up from below, but the foundation had been split into 4 pieces.It took 2 D8's to push each piece onto a flat bed trailer.

They had to dig a trench for the flat bed to back into,because they could not be lifted.

The demo guy said there was a lot of lime and quartz in the concrete that made it very hard to drill or scratch.He also stated,as you did,that concrete gets harder over time,especially if kept wet or moist.

They did not cut corners 100 years ago and the contractors and workers had very high ethics.

Sad to see that such quality is becoming an endangered species.

Poor construction by disreputable builders has happened for millennia. Those structures didn't last to see your 100-year benchmark, too.

My wife and I have had a co-op on the beach up in Broward since the 1980's. Our co-op was built in the 1960's. The impact of salt air that near the beach is horrible on any steel components (even many Stainless steels) as well as electrical contacts. Our maintenance people are continually tapping on the concrete, checking for hollow sounds to determine when and where rebar needs to be epoxied and resurfaced.

Unless the contractor didn’t used the correct cement/aggregate mix. But this is all speculation at this time

Was fiberglass reinforced concrete around 40 years ago? I thought it took a while to develop glass which could withstand the high pH of cement/concrete.

"...a $15 million repair needed sounds rather substantial..." yes but a strange number. The consultants original estimate was $9m ... the management came up with $15m ...give or take a bit a 167% rise ...or was the original so badly wrong? Why - 60+% inflation over 2.5 years?
I look forward the seeing the coroners/inquiry's findings.

I don't know about that time period but most of what I see going up now has "post tensioned slabs" https://www.concretenetwork.com/post-tension/basics.html. I don't actually know but I would guess that they have much less rebar in them than you would guess.

You can see in the video https://www.youtube.com/watch?v=In697MamSKE that the central part of the building had a failure that caused a section of roof/floor break, fall onto a lower floor, break it, and the breaking and pulling caused a very chaotic rubble pile as everything breaks and comes down.

You can also see in the video that after much of the central part of the building came down the eastern part of the building had its supports broken out and the eastern part of the building pancaked down in somewhat unbroken layers.

I can't find the shot again but there are photographs on the internet showing the eastern part of the building down in somewhat uniform and somewhat unbroken layers with each layer shifted a little more to the south as you progress up the pile. Thus, the southern lower supports were the first to fail and that failure was caused by the central part of the building falling.

There are reports that there were crews on the roof in previous days working on significant structural problems caused by water leakage. I would guess that to fix structural steel you would have to remove material to open up the area where structural steel needs repair. There is no way for internet story reading me to know what caused the building to fall but this sure seems like a smoking gun.

Modern tall buildings don't have enough strength for the remainder to stay up if they have an area with a significant failure. Thus, they don't look like they have enough rebar. They will also never find me in one as a permanent resident.

Once the site is cleared of rubble, a close, deep inspection of the sunken foundation piers will disclose their number, their layout, their cross-section, their depth and of course their reinforcement.

A comparison with the specification values and a modern assessment of that specification must follow.

These piers are the primary source of the settlement in sand which has stressed all the above-ground materials.

It seems to me that the clue is in the sentence, "The building had been settling slowly for many years,but not evenly." Concrete is strong in compression but readily fails in tension. Although rebar holds the concrete in compression, the "uneven settling" would likely subject regions of concrete to tension which apparently failed.

The engineering report of 2018 indicated severe salt-water intrusion causing significant degrading of the concrete in the lower levels...

There is also the possibility that a sinkhole developed under this condo.

Could be, but anecdotally, I've never seen sinkhole "stories" in Florida near the beaches. Solar Eagle would have a closer perspective on the issue.

According to one insurance company report, the geology for the entire region of Miami is bare or thinly covered limestone.

Recent story just reported that a victim called her husband at 1:30 AM to report about noises. He was away up in DC. She was standing on a 4th floor balcony and told him that the swimming pool had dropped down into a sinkhole. He then lost the connection. Another story said that it appeared that 'the collapse started at the bottom' which would also indicate the possibility of a sinkhole.

That "sinkhole" may well have been the parking garage of the facility.

If a sinkhole opened up under the building, I suspect it would collapse whether it was in good or bad condition.

I'm wondering if ground penetrating radar could be used to detect underground voids under buildings before they become sink holes in locations like Florida.

Yes, if a sinkhole is the origin of this disaster then the building condition and maintenance are irrelevant.

At the Wikipedia entry for sinkholes, I found this critical sentence:

Sinkholes are common where the rock below the land surface is limestone or other carbonate rock, salt beds, or in other soluble rocks, such as gypsum,^[12] that can be dissolved naturally by circulating groundwater.

I like your suggestion of ground-penetrating radar to look for voids. Building owners probably didn't want to know if there was a hole below before this disaster.

Well I've lived in Florida for most of my life, and I've never seen a sinkhole....

Sinkholes are a very rare phenomenon but so are multi-story buildings collapsing. I proffered this scenario only to try and keep people open-minded about how this disaster happened. Identifying the actual cause of this disaster won't happen until the entire debris pile is cleared and studied.

Actually, how about Fatigue caused by location and exasperated by construction.

You have salt air. Hurricane and aircraft stresses as well.. Cracks that have been patched but still let the salt in..

Add the fact construction is never quick so rebar gets some rust started before getting into concrete.

Recent vibrations from nearby construction probably hastened the job that nature started. Other building being to the south by 1/4 mile may actually have it away from the flight path further...

But most newer construction has gone up a size on all rebar.. as well. No more 3/8 with 1/4 wire stirrups.. closer spacing.. and many newer contractors adding gfrc as well..

It is way to early to make any GUESS's.
Time to get survivors and recover the dead and THEN do an autopsy on them and the building.
As for the re-bar theory, until someone does scans, measurements and so on, and gets their hands on the original drawings - of 40+ years ago - any presumption is gum flapping.

Sadly,the ultimate cause,in all such situations is friction;A greedy wallet rubbing against a rigid time table and flexible ethics, in all directions.

This is a tragic event. Thoughts and prayers to the families, friends and first responders impacted with this collapse. Based on what is known so far (little), it will be critical to understand a 5-why investigation of what happened.

My other thought is that based on the final cause, how many other high rise, oceanfront buildings have similar issues. Personally, it sure makes me think of renting rooms for vacation in low rise buildings.

Again, thoughts to those impacted.

You can't hide from the grim reaper....If anything this shows the quality of construction and maintenance in that only one building has failed, one out of how many? Too many to count....

"In fact, Florida has a total of thirty-seven buildings that reach or exceed a height of 550 feet. While a majority of these towers were built in Miami, you can also find some in Tampa and Jacksonville.Sep 18, 2019"

What I see is a totally inadequate response to a structural engineering report, 2018, that comes just short of a condemnation.

Why? (insert your favorite rebar, concrete add-mix, substrate stability, salt air weathering or whatever cause here).

I really don't care. If my structural engineer(s) tells me one of my mega-sculptures is an accident/ failure waiting to happen I don't screw around hemming and hawing about causalities, timeframe and the dollars to rectify; I fix the issue(s). I certainly don't do what the then City of Surfside's building inspector verifiably did with the building's residential committee, re: homeowners association, telling them they live(d) in a good and safe building with minor issues that should be addressed.

This guy has a lot of information and building plans, pictures, and some interesting info we haven't heard or seen yet....

Other building residents in the area are starting to get panicky...

SE: Thanks for finding those videos with significant information. Flooding in the parking garage probably caused damage to the columns which hold the whole building up. Plus, it was said that they had problems pumping the water out, but it went away anyway. To me, that means concerns about washout of the soil under the building. In addition, the building is probably sitting on a forest of pilings; were they damaged by all this water? The following is pure conjecture! Maybe it was specified that the piling be made from weathering steel under the false statement that "it doesn't rust." When used where there are wet & dry cycles, a coating does form that prevents further rusting. However, as I learned many years ago when working on high tension poles, when weathering steel is continuously wet, it will rust like ordinary steel. Probably the piling was continuously wet; but what type of steel was it made from? Was the piling filled with concrete after being placed?

Yes it seems pretty clear that the issue was lack of maintenance through renovation and repair, that was pointed out and identified over the past few years, but not addressed in a timely fashion....The building manager is the most important position in a condo building, keeping things in good working order is a real battle, and a full time job....you need qualified personnel doing the repairs and when needed you must not hesitate to call in the big guns....Waiting till the last minute to do repairs on a commercial building is not a sound strategy....This requires a condo board that facilitates the building managers' recommendations, so that things get done properly and on schedule....

Thanks. Some real information here.

Not enough oversight. Government or otherwise.

Texas can't generate power because of corruption. Florida can't keep its older buildings safe for the same reasons. We're drilling for oil like there's no tomorrow. In pristine National Forests and off-shore wells.

Let's see. Who was in charge when this all started? Does it really matter, now.

I'm sure that SE will set me straight about how the "other side' is all to blame.

Shirley you can't be serious....

Oh man, this guy is toast....

Let the finger pointing begin....

Sadly,the final analysis will boil down to the reason in #15.

Seriously do you think anybody living in these condos had any belief that the building was about to collapse? Clearly the problem was that people were led to believe that the building was safe....that has nothing to do with money, that is incompetent management....

Of course the occupants did not know,but management did,and it was too expensive($$$$$$) to take action to do a PROPER repair.

Loss of rental income,expensive repair costs,etc.

Management's focus was on $$$

Surely,SE,you can see the connection,you are an intelligent person.

That is why I think management should live in the outer walls of the buildings that they manage.

I won't be surprised to find out that the earlier maintenance for this building was substandard if not deferred and the building management pocketed the maintenance fees or directed it to their corrupt cronies. A need for a fifteen-million-dollar repair doesn't happen overnight.

Still, everything reported here is premature speculation from hundreds of miles away. It took over a year for a final report on the cause of the pedestrian bridge collapse at Florida International University. They've yet to clear all of the rubble from this much bigger building collapse.

Hopefully, some of the individuals responsible for this disaster will pay a price.

The condo board keeps open books, there is no pocketing of money....the condo board is also elected from the residents, and are not compensated generally speaking....So the board members go down with the ship so to speak, if anything goes wrong....

When did you become a forensic accountant? Who's public accounting books did you examine? Can you post a link to these books, please?

Open financial books can hide grafts and all sorts of financial misdeeds. This blind spot is particularly true for individuals without formal bookkeeping training.

In the condo I lived in the minutes of all meetings were posted in the lobby, including any expenses, condo account balance, special assessments, and monthly payment adjustments to meet obligations, it was always in the $400 - $500 range...as well as the phone numbers and apt numbers of the board members you could call or contact if you had any questions...all work was done by getting written estimates from minimum 3 sources, and choosing the best, which was voted on...The interior of the condo was inspected every year and the toilet flappers and valves were replaced if needed, water heaters were required to be replaced every 7 years....the list goes on and on...Every part of the building is inspected and any problems must be corrected in a timely fashion or the condo association will do it and charge you for it....

It sounds like you didn't examine the books for this collapsed condo. It also sounds like you are convinced every condo association in Florida operates as impeccably as you believe your condo association did. So how do you think this rebar got exposed?

That looks like maintenance neglect to me.

Image from a Miami Herald report.

https://www.miamiherald.com/news/local/community/miami-dade/miami-beach/article252421658.html

Clearly there was a management crisis from 2018 on, and possibly well before that....

..."SURFSIDE, Fla. — The former Surfside building official who three years ago told residents at the South Florida condominium that collapsed last week that the structure appeared to be “in very good shape” was placed on leave from his current job, city officials said....

...Prieto was the top Surfside building official when the 40-year recertification inspection process was being done at the Champlain Towers South building in November 2018, The Wall Street Journal reported. Prieto served as the building official in Surfside for about seven years, the newspaper reported.....

...A month after engineer Frank Morabito noted there was “major structural damage” at Champlain Towers South, Prieto attended a condominium association meeting and told the board he had reviewed the report. He told association members that he believed the building was in good shape, according to minutes from the meeting obtained by the Herald.

Prieto told the Herald on Saturday that he did not recall receiving the report and did not recall any major concerns with the building, adding: “If there had been, they would have been addressed right away.”....

https://www.kiro7.com/news/trending/rosendo-prieto-ex-surfside-building-official-who-signed-off-condo-placed-leave/IZYOENKJEJE3FFC4ZVDDVEZMS4/

Your comment/statement "....that has nothing to do with money, that is incompetent management...." needs expanding to the two, or maybe more points raised.
1. Money - invariably.
2. Incompetence - possibly but refer back to 1.
3. Corruption - on many parts, refer back to 1.
4. Stupidity - who hired them, refer back to 1, 2, and 3.
5. Engineering, really - the 2018, 9 page "missive" on a habitable structure that big...really? Refer back to 1, 2, 3 and 4.
https://www.wfla.com/wp-content/uploads/sites/71/2021/06/8777-collins-ave-structural-field-survey-report.pdf
- would love to see the blood letting that this guy is going to receive in the box; and so on

Owners of million dollar condo's that are beachside or anywhere else for that matter, do not scrimp on maintenance, in fact if anything they go overboard in the other direction spending left and right upgrading the property....

IMHO:

Apartment buildings should be held to the same standards as NASA on their launches.

There are more human lives at risk in apartments.

Most failures at NASA can be attributed to reply #15.

Sure it would cost more to build this way,but what price hundreds of lives?

Obviously the Board did not consider the human costs.

They should all be held accountable as criminally negligent,and serve real time in real prison.

They should also be required to live in the bottom outside floors of all the buildings in their purview,on a rotating basis,perhaps 1 month in each if inspections reveal structural problems.

Embellish them as they please,but not structurally;Make them live there,no vacations while serving their required resident time.

Perhaps they will then realize the lesson that King Dionysius taught Damocles.

Make the men that packed the chute jump with it.

That sounds very fair to me.

Inspectors should likewise be held legally and morally accountable,and given the power to act to effect corrective action...but them again,there will be much friction generated by this suggestion.

Does anyone remember what GM calculated as the cost of a single human life?

Here is what the government says about that:

https://www.npr.org/2020/04/23/843310123/how-government-agencies-determine-the-dollar-value-of-human-life

How can one put a value on a life?

in Vietnam,if a military vehicle ran over a chicken,the military was billed for the chicken,all eggs it may have laid and the output of all of it's hatched eggs,their eggs,etc,on and on and on.

We put a value on life every day when we purchase life insurance.

Sister building well maintained and in good shape....proper maintenance makes the difference...and that requires good management...

..."Video recorded at Champlain Tower South minutes before its deadly collapse Thursday appears to show water pouring out of a ceiling in a parking garage and rubble on the ground, ABC News has confirmed.

Adriana Sarmiento told ABC News that she and her husband were on vacation and swimming in the pool at the nearby Bluegreen Vacations Solara Surfside Resort when they heard a loud noise. They went out into the street to investigate and recorded water flowing from the parking garage and what appears to be rubble on the ground. In her comments on TikTok, Sarmiento said the video was taken at 1:18 a.m. on June 24. The building collapsed at 1:25 a.m., she said."...

In depth analysis of the above video....

..."This Colombian-Cuban couple were on vacation in the building next door, in their interview in Spanish they said this: they went down to walk and heard a loud noise and realized that the noises came from the garage of the collapsed building, a lot of water and parts of the The roof of the garage had already collapsed, some people went out to the balconies because of the noise and this couple yelled at them to get out of the building, but they either did not understand or did not hear well, in minutes it began to fall and the couple ran for their lives behind wall, when they looked back they could not see .. until they noticed that there were no people or buildings .. she replies in Spanish .. they all died, they all died .."...

Evidence continues to mount that the garage area was structurally failing for several years....

They would also have to take soil samples... being in Florida, there could also be an issue with a lowered water table. That actually helps support the foundation strata.

Sometime earlier, I think in one of the videos that SE found, there was mention that there was a gap in the bedrock about where the condominium is. How did that affect the foundation? Did they do test borings or just "assume?" Is the condominium resting on pilings? If so, how were the pilings designed?

Thanks,

I’m reading through the posts now... I can see I posted possible issues that have already been address or brought up in later posts.

Some new shots...

A starting point for anyone with a theory...

https://townofsurfsidefl.gov/departments-services/town-clerk/champlain-towers-public-records-documents
https://www.townofsurfsidefl.gov/docs/default-source/default-document-library/town-clerk-documents/champlain-towers-south-public-records/8777-collins-ave---structural-field-survey-report.pdf?sfvrsn=882a1194_2

GA

I like public disclosure of formal documents. There is a lot of data here.

If it was built like this one,(except for the piss-poor foundation substrate geological research), in Texas,it would not have collapsed.

The reinforced structure was very tough to destroy even by experts.

https://www.youtube.com/watch?v=y0zArm4FR1Y

They just took down the rest of the building....

SE: Something's wrong with that video--it won't play. Comes on with the red line all the way across.

Click on the "Watch on Youtube button" ...then move your pointer along the red line and find where the building is still standing and click...this is the beginning of the explosion...It is a live recording....

Here's a ground floor view from the other side....

Here's another angle....

Thanks. Got it. This qualifies as operator error! I didn't notice that the video was hours long and the event took far less than a minute at around the 54-minute mark.

This seems like a contributing factor...it seems to me that there was several layers of concrete poured over the years for patio stamping in the pool area, resulting in a very heavy 12"+ thick total slab which may have exceeded the design weight of the pillar supports in the garage below, add to that the deterioration of the columns themselves, and the lack of rebar and it would explain the supports punching through the slab....

https://www.documentcloud.org/documents/20985354-20201014bodminutesapproved#document/p36

The support columns in the part of the building that collapsed seem to be much smaller than the columns in the part left standing....

The support columns in the part of the building that collapsed seem to be much smaller than the columns in the part left standing....

A not unusual occurrence, and usually the norm - not the exception.

To have any opinion there you need a full set of plans and the original engineering load take downs. All of them.

Sadly,the problems with mot failures is not with engineering,but with cost cutting accountants reducing everything to the bare minimum,without knowing anything about engineering. An example is the Titanic.The original plans called for water tight compartments that reached all the way to the ceiling.The accountants ,over the objections of the engineer,decide that water would never get that high,so they reduced the height of the wall so they did not reach the ceiling,in effect nullifying their purpose.

The engineer regretted letting them have their way and deliberately went down with the ship.

The original design called for more life boats,but the cost and esthetics ruled them out over the original design.

And the cost saving,corner cutting deviations continue everywhere,down to the contractor and worker level.

Who knows what will be found when the evidence is examined.

Their should be personal accountability for every job failure.

Several layers of concrete would make me wonder about adhesion between the layers. I'm not a concrete guy, so don't know if adhesion requires special prep or if it "automatically" happens.

Speculation, It’ll be stratified.. no adhesions, but since it’s Florida, the problem would be effects of chlorides.

In the northern states, it would be moisture and the frost/freezing.

Pouring a slab over another existing slab...