 It is March 1981 and construction workers are preparing to pour the concrete full of the roof of the new apartment block. Most of the concrete framework has already been completed during the pour, however the newly built structure would fail catastrophically, killing 11 and injuring over 20 more. Today's video we're back in Florida to what seems to be a state tradition, the collapse of a concrete structure. My name is John, welcome to Plainly Difficult and this is my video on the Harbour Key Condominium Collapse. Background Our story starts in the land of the Florida man, officially known as the US state of Florida, but today more specifically, Cocoa Beach, a small coastal town which is around here on a map. The area's economy was closely linked to NASA's operation from the nearby Kennedy Space Center, in which many locals were employed either directly or via third party companies. As such, when the Apollo program was shelved in 1975, the local economy crashed. Unemployment went to 14%, but the local jobs market would improve after the announcement of the Space Shuttle program just a few years later. This would bring new people to Cocoa Beach and as such new housing was needed. Cocoa Beach was undergoing a bit of a building boom in the 1980s with new condos being built along State Road A1A. Part of this demand would be plugged with plans to build a new five-storey concrete framed set of apartment blocks. The developer was to be Milwaukee based town Realty. They had built other buildings in the area and to help they contracted out a local firm for construction work called Univel Inc. The Cocoa Beach apartment blocks were planned to be made up of five storeys and were to be 242 feet long and 58 feet wide. The structure would rely on reinforced concrete and framed with multiple columns of 10 x 18 inches wide with narrow ones of 10 x 12 inches at the ends of the building. The floor slabs were to be 8 inches thick although slightly thinner for the balcony sections. However I should point out that state regulations were actually a requirement of 11 inches. Both the slabs and the columns were reinforced with ATSM 60 grade steel. To hold the steels in place during concrete pouring things called chairs were used. These ensured that the vital reinforcement is at the correct depth. You see if it's not in the right place the concrete section can bend as the load is spread unevenly. The facade walls of the building were made of non-structural masonry. Construction works began in 1980 with preparation of the site and building the blocks foundations. The structure itself would begin to be built in February 1981 when the ground floor form work was begun. The schedule for frame construction was to add around a floor a week and this would involve starting at the south half of each particular floor slab cast on a Tuesday. Replacement of steel bars in the north half of the slab and casting of the columns over the south half were carried out the next day. On Thursday the columns in the south half were stripped and then the north half of the slab was cast and the forms below the south half of the slab were lowered. On Friday the forms in the south half were replaced by reshalls and flown to the same location in the story directly above and the columns over the north half were cast. The following Monday the columns in the north half were stripped, the steel bars in the south half of the slab above were placed and the flying forms below the north half were lowered. Now all of that was pretty much a bit of a mouthful. But although quick, soon enough after the first floors were added workers started to notice some worrying indicators of a disaster ahead. Several workers raised concerns that cracks had started to show on some of the concrete work. After each level's flying form was removed cracks could be seen on the slab at the mid span and where the columns met the floor. A foreman circled the cracks with a crayon and called out the structural engineer on the 10th of March 1981. By now the second and third floors were in place. The suggestion from the engineer was to place more reinforcing bars in the mid spans. Joints between the columns and the floor slabs were described by some workers as having a honeycomb or spider's web cracked face. Slabs around the north and south end second floor apartments had deflected almost immediately after their forms were removed. Deflection is a type of bending or sagging of a concrete slab. A worrying little quirk was found during the construction on the fourth floor. Workers discovered on the east side near the lift tower a puddle of water. Well what does a puddle of water have to do with anything you might ask? Well this was hinting at the building becoming uneven. The depression was refinished with a concrete skim but bizarrely the water began to reappear. Multiple issues were highlighted by workers on almost every part of the construction. Parts of the structure had its rebar exposed after form removal which needed to say exposes the structure to corrosion and this was due to poorly poured concrete. Concrete quality was also very poor with a low water content meaning it dried out too quickly for it to be properly finished. The project received its concrete from two sources. The first was from a ready-made supplier. This accounted for roughly one third of the total requirement. The other was from an onsite batch plant. Although issues were raised construction continued all the way to the top floor. This was because nothing had failed so far. Well, until it would. The disaster. The time had come to start pouring the Koka Beach Condominium's roof. Workers began their shift on the 27th of March 1981 and I'm sure no one expected how the day would end up. The building at this point had in the south end the exterior walls for the first two stories. And in the north end construction of masonry walls was completed in the first three stories. Each floor had some level of activity on it with various stages of the project being undertaken. On the roof the concrete was being placed around column H. As the poor had continued throughout the day some workers noticed some trembling throughout the building. At roughly 2.45pm a work on the fifth floor heard a popping sound. At roughly 3pm around the centre of the building at the fifth floor suddenly gave way to what would be described as one long slide with one thump. Within seconds the entire structure plummeted into the ground with massive piles of concrete and rebar. Anyone nearby who could swamp to where the building was to try and find and save any workers. These people were just a few minutes before having a normal day at work. Due to the area undergoing a building boom many workers on other projects helped with the rescue work. Some even turned up with heavy equipment. Emergency responders and air force members reached the site and helped with the rescue efforts. Floor slabs were cut away into approximately 20ft square pieces by air hammers and removed by mobile cranes. The work continued over the weekend as heavy equipment removed the concrete and other debris. It would only be Sunday that workers got down to the foundation where the final two bodies were removed. In total 11 were killed in the collapse with 27 more injured. Now as with all of these types of incidents the question of how and why must be asked and this would lead to an investigation. The investigation. The National Bureau of Standards would head up the investigation into the collapse. Investigators would visit the site on March 28th and 30th 1981 just one day after the collapse. Followed up by a second visit that was made on the 7th to 8th of April. Investigators found that the slabs broke away from the columns at the slab column interface. As well as a number of vertical reinforcements bent severely. Hinting it would mean damage during fabrication. A number of conflicting eyewitness statements from the workers on site raised questions about how the building was being reshored. You see, reassuring is a vital part of concrete building construction. After the forms are removed, when the newly poured concrete is set enough, reshores are added to support the structure as the concrete hardens. This is because even though it looks solid, concrete gets fully set over a period of time in which it needs extra support. This is where the reshores are vital as if they are removed too early then the concrete hasn't gotten strong enough to support itself and more importantly the weight put on top of it. This issue can be even more dramatic if the concrete is of poor quality. The investigation would not just involve on-site visits but also forensic examination of the whole project from design to concrete mix. They found the concrete was of poor quality especially around the samples taken from the 5th floor which was discovered to be less than 85% of the required 4000 psi of compressive strength. After all that was said and done, the investigators released its report and it was really damming of the whole project. They found that the placements of the reinforcing bars in the concrete slabs were inconsistently placed which violated the ACI code requirement for clear spacing. This inconsistency created a congestion that prevented flow of concrete into the space between the reinforcement bars which in turn caused issues with the bonding of the concrete to the rebar. The concrete slabs were only 8 inches thick instead of the required 11 inches to satisfy the American Concrete Institute's building code minimum. During construction lower individual chairs for supporting the top layer reinforcement bars were used reducing the effective shear capabilities of the slabs. This caused the structural integrity of the building to be severely reduced and the addition of extra weight during the pour of the roof was the straw that broke the weakened concrete camels back. The damming report helped with charging two engineers, an architect and the two contractors with negligence, misconduct and failing to conform to state and local building laws. Both engineers gave up their license to practice engineering in the state of Florida. Unival, one of the contractors, folded almost immediately under the financial strain and the developer contractor, Town Realty out of Milwaukee, agreed to a settlement out of court to avoid litigation. They have continued to develop properties to this day, even including several more in Cocoa Beach. The disaster helped the state show up its enforcement of construction projects, but it wouldn't fix it completely. As well we know from a number of recent collapses that nothing is foolproof. Strangely enough, one of which also involved a construction project that all started in the 1980s and this came to light very recently and was called Champlain Towers. Now a number of you have noticed that I haven't been doing disaster scales at the end of my videos anymore. Well this is because the ratings were getting a little bit erratic. So I'm launching a new scale called the Balls Rating and it will have five set ratings. The first is not great. After all, the story has found its way onto the Plain Difficult channel. The second is bad day at the office. Next is Oh Balls, people will remember this. Fourth is outright negligent. And the fifth and final rating is dumpster fire. This week's video will be rated outright negligent. This is the Plain Difficult production. All videos are produced by me, John, in the currently wet and windy corner of South East London, UK. All videos on the channel are creative commons attribution share alike licensed. I'd like to thank my patrons and YouTube members for your financial support as well as the rest of you viewers for tuning in every week. I have a second channel, which is mainly for my music, so feel free if you want to check that out. It's called Made by John and I also have Instagram and Twitter where I post up random photos. And all that's left to say is Mr Music, play us out please.