I'm sure that my readers (all two or three of them) are aware of the collapse of the 13-story Champlain condominium building at 1:25 a.m. on June 24, 2021 in Surfside, Florida. I have a fascination with disasters like that, so I am going to share my thoughts on it.
Let me start out by saying that I don't think the disaster would have been possible if the building hadn't been made of concrete. In recent years, I have learned of several similar disasters, and in every case in which a building spontaneously collapsed, it was made of concrete and rebar.
There was the South Korean department store that collapsed (while it was open and full of customers) in 1996. Then there was the Bangladeshi clothes factory that collapsed in 2013.
In 2001, there was a building in Israel in which the floors collapsed under the weight of the dancing celebrants during a wedding banquet. The floors of that building were not typical concrete and rebar, but used a construction method called Pal-Kal which was invented around 1980. Nonetheless, the floor was mostly concrete.
When I heard about the Champlain condominium collapse, I wasn't at all surprised to learn that the building was made of concrete. Actually, I was surprised—but only because I didn't know that concrete-and-rebar was a construction method used in America. I assumed that in the U.S., a steel frame would have been used for such a tall building. (Since then, I have learned that the tallest building in the world is made of concrete and rebar.)
The problem with concrete is that it is brittle, and it doesn't have much tensile strength. "Tensile strength" means the ability to flex before it breaks. Both wooden and steel beams have significant tensile strength.
Because it is brittle, concrete can develop cracks, and it can also crumble -- you'll never see wood or steel crumble, unless the wood becomes rotten. Right now I live in a 130-year-old wood-frame building. The wood in the frame has gotten very dry over the years, but it is still flexible. If I were to jump up and down in my apartment, the building would shake, but nothing would break. Jumping up and down in an old concrete building might create fissures in the concrete.
In the pictures of the Surfside disaster, I noticed that the rebar was all pointing in one direction (at least, the rebar that I could see). Most of the visible rebar was sticking out of the floors. Now, perhaps the supporting columns of the building had more rebar in them, and perhaps the rebar was in a lattice structure (which is stronger). (Later: It appears the rebar was all straight and not in a lattice pattern.)
Concrete obviously isn't the only thing that contributed to the disaster. All of these things appear to be contributing factors:
* The building had endured forty years of being buffetted by hurricanes and salty spray from the sea. Salt attracts moisture, and moisture weakens concrete. Each time a hurricane passed through the area, it probably left some cracks in the concrete. Salty water also makes rebar rust, which weakens the concrete dramatically.
* Weeks before the collapse, nearby construction was making the building shake.
* The pool deck wasn't built with a slope, so water pooled on it
instead of draining off, which undoubtedly weakened the deck concrete. (As it turned out, the pool deck played a significant role in the collapse.)
* A 2018 inspection determined that there was significant structural damage in the garage, which was under the pool deck and the building itself, and also in the support columns.
* The 2018 inspection also determined that a large slab of supporting concrete under the pool deck needed repair. Altogether, the damages were so serious that the repairs were expected to cost $15 million.
* When workmen arrived to start reinforcing the building in November, 2020, they found that the damage to the concrete was so severe that they couldn't work on it, especially since they were told that they couldn't close the swimming pool.
* Shortly before the collapse, someone took a video of a broken pipe in the basement that was spewing water (although that may have happened after the pool deck collapsed). Moments before the collapse, some residents noticed that the pool deck (meaning the paved ground around the pool) suddenly collapsed.
These things turned out to be a factor also:
* Many areas of the building did not have adequate waterproofing, especially the pool deck. Waterproofing is essential to keeping concrete strong over the years.
* The building was under-built. It needed thicker and more robust columns. One particularly curious fact is that the columns under the portion that collapsed were thinner than the columns under the portion that didn't collapse, even though both portions of the building were the same height.
* Many of the apartments had been renovated with heavy marble floors and walls, which added significant weight to the building. The pool deck was also renovated with tiles, as were the balconies. The appliances used in the building may also have been upgraded, although that's just a guess on my part.
* Heavy planters holding palm trees were installed on the pool deck, probably contributing to its collapse. Several years earlier, a small crane was driven onto the pool deck to service the palm trees. That crane probably weakened the pool deck.
* Cars were permitted to park on the portion of the pool deck under the western portion of the building (the portion that didn't collapse). That may have contributed to the collapse of the pool deck, which ultimately brought the south portion of the building down (see next point).
* The chief structural mistake that was made was that the pool deck was attached to the columns that supported the South side of the building. When the pool deck collapsed, it pulled several columns under the building sideways, and that ultimately caused the building to collapse.
* A contributing factor to the collapse may have been the cool overnight weather. Concrete shrinks when it is cool, and the pool deck may have pulled away from its supports.
So far, I haven't mentioned the human tragedy. Because I'm fascinated by the science of what happened doesn't mean that I don't care about the people.
Perhaps because I'm gay, the saddest of the deaths for me is the handsome 21-year-old Greek man named Andreas Giannitsopoulos. He was a proud track-and-field athlete. As I write this, he is still trapped in the rubble, undoubtedly dead after seven days. Pictures of him in his red track outfit can be found on the internet.
Giannisopoulos was staying with his godfather, who obviously also died.
Another young man and his girlfriend, Ilan Naibryf and Deborah Berezdivin, were staying in the building for just one day so they could attend a funeral.
A terribly sad story from this tragedy is that a woman's voice was heard coming from the rubble during the initial hours after the collapse, but the rescuers couldn't figure out where she was, or get to her. The debris from the collapsed building must weight a thousand tons. She probably died a very slow and painful death.
There were also half-a-dozen young children living there.
When Nova does their show on the tragedy, I will be very interested to see it.
* * *
It is now about three weeks later, and I am getting a better idea of what happened during the collapse. (In this section, I repeat some of the things I said above.)
The pool deck was nothing more than a huge slab of concrete held up by narrow columns, an arrangement I still find surprising given the tendency of concrete to become brittle with time and exposure. (For that matter, the building was also held up by concrete columns that were narrower than they needed to be, especially given that weight added to the building over the years.) Under the pool deck and the building itself was a huge garage—in other words, the entire property was over the garage, which was its basement level. Given that the pool deck was level and therefore didn't drain properly, and given that the pool deck wasn't waterproofed properly, it makes perfect sense that the pool deck failed. Now, the pool deck was attached to the front row of columns under the south side of the building, the side which started to collapse first. In other words, those columns were doing double-duty, supporting the pool deck and supporting the building. It would seem that when the pool deck collapsed, it pulled on those columns, causing them to fail, and bringing down the building along with the pool deck.
So, that's the way I think it happened: The collapsing concrete of the pool deck weakened columns that held up the building, and the building collapsed. As one section collapsed, other sections became weak and also collapsed.
There were two great flaws in the design of this property: First, making the pool deck level so that water would pool on it, which weakened the concrete over time. Second, attaching the pool deck to the columns that supported the south side of the building.
* * *
It is August now, and I have decided to add the story of Maria Iliana Monteagudo, who lived in the portion of the building that collapsed, and who was in bed sleeping, but who nonetheless escaped from the building.
Monteagudo lived in apt. 611. Something woke her up, probably around 1:10 a.m. or 1:15 a.m. She describes her waking as a supernatural event, although at the time she thought it was the breeze coming from the patio in the living room. She walked to the living room to close the patio door. She then noticed that the building was swaying, and that the door wouldn't close. She heard a cracking sound and saw that a wide fissure was opening in the living room wall from the ceiling to the floor. She ran to the bedroom, quickly put on some clothes, grabbed her purse, and headed for the stairs.
There was an exit stairway right near her apartment, but she had moved into the building only six months before, and she wasn't aware of it. So she dashed down the hall towards the front of the building (the part that didn't collapse), and she started descending a stairway there. By the time she got to the fourth floor, she could hear the building collapsing (which included the hall she had just dashed through). All the time she was praying to God, and fearful that the building was collapsing in stages, and that her portion was next. She made it to the bottom, where she ran into a security guard, who thought that an earthquake had happened. Together, they found their way to the street, which involved wading through water and climbing over fallen concrete.
In other words, her portion of the building, including the hall outside her apartment, collapsed within a minute of her leaving. Now, that's what I call an "escape"! If she had taken the stairs near her apartment, she would have been crushed in the falling debris.
The interesting thing about this story is that it must have taken her at least five minutes to make her escape. If you consider that she took the time to get into street clothes, it could have taken ten minutes. What that means is that the collapse wasn’t instantaneous. The video reconstructions I have seen suggest that a column under the building was compromised, and the building came down quickly, but it may have actually been a more progressive event. It’s too bad that more people didn’t notice what was happening and get out.
Clearly, one of the reasons that Monteagudo fled instead of staying in the building is that she learned of its structural problems after she moved in a half-year before. She was probably already concerned about the integrity of the building.
There was another woman who might have gotten out in time if she had realized the danger she was in: Cassondra Billedeau-Stratton. She was a younger woman who apparently stayed up later than Monteagudo did. She saw from her apartment (which I think was on the fourth floor) that the pool deck had collapsed; but instead of running out, she called her husband, who was travelling, to tell him about it. The building then collapsed while they were talking. Billedeau-Stratton was a very attractive forty-ish woman who had been a model and interior decorator, and who had an interesting web site which can still be seen here:
http://www.chicliving365.com/
(I suspect the site has been left up as a kind of memorial.)
One more bit of information about this tragedy, which is particularly sad, is that as many as nine of the victims may not have been killed when the building collapsed. One of them in particular may have remained alive for as many as ten hours after the collapse. How awful.
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