Over the last 2 years, the National Institute of Standards and Technology or NIST has been investigating the unexpected collapse of portions of the 39-year-old 12 story Champlain Towers South Building located oceanside in Surfside Florida, at 1:30 am on June 24, 2021, killing 98 residents. The day after the collapse, a team of NIST scientists and engineers began working with federal, state and local authorities, to identify, preserve, and analyze materials that might reveal the cause of the collapse. The ultimate goal of the NIST is to recommend changes to regulations and building codes when their investigation is completed in the Spring of 2024 and a detailed report issued in 2025. Given, there are an estimated 1.5 million oceanside condominium units in Florida, the report cannot come too soon!
While forensic engineering of the collapse is ongoing, NIST is currently focusing upon 400 chunks of steel reinforced concrete recovered from the collapsed building, stored in a nearby warehouse. By focusing upon chunks of steel reinforced concrete, NIST reveals its hand as to what the final report may reveal and appears to validate preliminary findings made by independent engineers. Preliminary findings suggest the oceanside condo building was negligently designed, negligently constructed, negligently maintained, and negligently managed, all of which contributed to the collapse. The current premise appears to be that the reinforced concrete pool deck adjacent to the condo building collapsed into the parking deck below thereby undermining one or more reinforced concrete columns supporting the condo building causing portions of the adjacent 12 story condo building to collapse.
The premise underlying the failure of reinforced concrete in the pool deck, columns, and the structure of the condo building is based upon the symbiotic relationship between traditional concrete and reinforcing steel. Concrete has a very high compressive strength – when pushing it together. But concrete has very low tensile strength – when pulling it apart. Reinforcing steel or rebar is exactly the opposite. Rebar has low compressive strength when pushing it together, but high tensile strength when pulling it apart. When rebar is embedded in traditional concrete, the combined properties give reinforced concrete both compressive and tensile strength, thereby creating flexural strength or resistance to sag. Of course, the key to this symbiotic relationship is dependent upon design, construction and maintenance of the reinforced concrete as well as management of the building.
Negligent Design. Design of reinforced concrete entails coordinating the tensile strengths contributed by the rebar with the compressive strengths contributed by the traditional concrete. This is achieved by balancing the size, amount, and embed location of the rebar with the thickness and cement content of the concrete. Together the concrete and rebar must have sufficient strength to support the weight of the structure or dead load, the weight of the occupants and their possessions or live loads, and the stresses imposed by temperature changes. Significant safety factors are then applied which can be as high as 200% or more of the dead loads, live loads, and temperature stresses used in the design. Preliminary findings at the collapsed building show that the size and embed location of the rebar within the reinforced concrete was not properly designed to support the anticipated stresses. Ironically, the licenses for several of the designers involved with the collapsed building had been revoked or suspended prior to the collapse due to design shortcuts involving other unrelated projects.
Negligent Construction. Construction of reinforced concrete requires properly embedding the rebar at the proper locations within the reinforced concrete. Preliminary findings at the collapsed building show that the rebar was not properly located in multiple areas within the pool deck and structural columns. Additionally, the pool deck was not properly sloped to shed water from rain, salt air and chlorinated pool water, causing ponding on the deck. Preliminary findings further show this ponded water migrated into the reinforced concrete causing rust and deterioration to the rebar within the reinforced concrete that was deficiently designed and improperly embedded in the first place.
Negligent Maintenance. Maintenance of reinforced concrete demands that cracks and crevices be sealed to prevent water – especially salt water – from causing rust and deterioration of the rebar. Preliminary findings at the collapsed building show water intrusion throughout the pool deck and condo building was widespread and significantly impacted the strength of the rebar within the reinforced concrete. Prior repairs to the reinforced concrete to remedy the water intrusion issues had been negligently performed and failed to prevent water from reaching the rebar. Other cracks and crevices went unrepaired. The ponded water, coupled with the unrepaired cracks and crevices contributed to rusting of the rebar and deterioration of the reinforced concrete already defectively designed and constructed.
Negligent Management. Management of a facility involves knowledge of the design and construction parameters supporting the permissible live loads. Before heavy loads or objects are moved into the facility, management must identify the weight of the live load to be added to the structure and if the structure has sufficient strength to support the live load. Preliminary findings at the collapsed building show several very large, very heavy planters were relocated to the pool deck, planted with large palm trees, and became water-logged from recent rainstorms. The overloads created by these planters contributed to the negligent design, construction, and maintenance of the reinforced concrete.
Pending release of the final NIST investigation and report, preliminary findings suggest there is more than enough blame to go around regarding the causes of the collapse of the Surfside condo building. Consequently, it should not be surprising that the estates of the 98 residents killed in the collapse, were paid a cumulative amount in excess of $1 Billion dollars in damages for property damages and loss of life. We can only await what NIST will recommend to avoid the perfect storm of design, construction, maintenance, and management, mishaps that appears to have caused the collapse in the first instance.