(CNN) When sunrise paints the skyline of downtown Miami in hues of gold, blue, orange and pink, the light sliding across the buildings, highlights more than just a dazzling display of architectural design. Many of these buildings are also a triumph of innovative structural technology. They are a testament to the dual nature of coastal, tropical Florida: long stretches of pristine sand and placid surf that are regularly transformed by violent, often deadly storms.
I have spent the best part of my career here designing and preserving historic structures that can withstand what nature throws at them — the flooding and erosion from extreme rains and high tides, the projectiles tossed by tropical storms and hurricanes. We Miami architects design apartment buildings — vertical homes — following the highest standards in safety, like high-impact windows and reinforced concrete structure on vertical pilings, without sacrificing the structural allure that makes Miami so breathtaking.
I was up before dawn as usual on Thursday to make coffee and watch the sun come up. I sat outside, opened my phone and saw the reports of a collapsed building on the 87th block of Collins Avenue in Surfside: Champlain Tower Condominiums. I was in high school in 1981, the year it was built. Its concrete piles, shear walls and columns with floors of horizontal concrete slabs represented what has been the gold standard of coastal construction for nearly 100 years.
Those standards got tougher after Hurricane Andrew, a Category 5 storm, battered Florida in 1992. The state implemented new building codes with strict safety requirements that all new and existing structures had to meet. They were among the most stringent in the industry.
And they worked. A paper by James Done of the National Center for Atmospheric Research, prepared in collaboration with the University of Pennsylvania found that ,”A multiple regression analysis finds homes built after implementing a statewide Florida Building Code (FBC) in the early 2000s experience significantly lower losses than homes built in the previous decade, in agreement with previous literature.”
Understanding the structural integrity of the buildings that face the ocean on Miami Beach, I have struggled to reconcile the partial collapse of Champlain Towers South, which had 136 units. Within hours of the collapse I began fielding questions from the media and others on the probable cause of the structural failure that led to the collapse of the northeast facing facade. (It’s still not fully clear what caused the collapse.)
I reviewed the live images and video footage, which revealed that the collapse began at the internal aspect of the edifice. The structural failure appears to have happened at the core of the building, where the horizontal concrete slabs meet the vertical concrete columns and shear walls, which are designed to resist lateral forces. The videos show that shortly after the compromise of the internal structure the building falls away from the ocean to the west, which suggests the concrete slabs disengaged from the internal backbone of the building, causing a “pancake” collapse.
Post-tension reinforcement — or rebar — gives 6-8 inch concrete slabs with the high structural integrity; however, building floors are not designed to absorb the load produced by the collapse of a floor. Therefore, when the initial slab fell, this may have caused a buckling effect between floors and the complete collapse of the northeast block of the building.
In live images, we see the vertical elevator shafts and stairwells, which are commonly where the shear walls connect to the horizontal slabs, providing the necessary lateral strength. The quagmire question now becomes how is only half of the building compromised? Champlain Towers was undergoing its 40-year building inspection at the time of the event, though documents have not yet been submitted to Surfside officials, according to the town clerk. Information from that ongoing process may produce insights into the cause of the collapse.
To be certain, over the course of the days, weeks and months ahead, forensic engineers will shed light on what went so terribly wrong.
I am moved by the cohesive efforts of the first responders, the city and government officials, media and my neighbors, as we rally our efforts. But my heart is heavy with the loss of life from this tragedy. Miami is my home.
The collapse at Champlain Towers is unique, and not necessarily representative of the potential problems of such construction. When the cause of a structural compromise is revealed, it must be treated as an opportunity to reevaluate our maintenance and inspections, materials and construction to innovate.
Every day, I am inspired and humbled by my role and responsibility as an architect.
Source: https://edition.cnn.com/2021/06/25/opinions/miami-architect-building-collapse-kobi-karp/index.html