July 13, 2021
While it’s still too early to determine what caused a condo to collapse in Florida last month, a Mizzou Engineer is looking into some of the possible causes of collapse of buildings under constant loads.
“Most collapses aren’t due to just one cause; there are a lot of things contributing,” said Sarah Orton, an associate professor and director of undergraduate studies in the Civil and Environmental Engineering Department.
One of the biggest factors? Time. Orton is currently studying the role time plays in the overall life span of a building as part of ongoing research on structural failure.
“Concrete has a time dependent effect,” she said. “The strength of concrete under a high load for a long period of time is less than that under a short period. In addition, the building structure may be deteriorating due to causes like corrosion. After 40 years, there may be enough corrosion for the structure to lose capacity enough that the building may fail. We’re trying to understand how time contributes, and once we get that figured out, we can start looking at other things to really understand the capacity of a structure.”
With funding from the National Science Foundation, Orton investigates the near-collapse behavior of reinforced concrete buildings under sustained gravity loads. Gravity loads are mostly composed of a building’s own weight, but also include the weight of interior objects such as heavy heating and cooling equipment.
While buildings are designed with a high factor of safety, problems such as design and construction errors, poor-quality materials, overloading and deterioration can decrease the safety factor of a building. The cumulative effect over time can lead to partial failure, such as one column cracking or breaking. That puts more weight on other support columns and can lead to a progressive collapse.
Orton’s team recently wrapped up lab tests of flat plate connections, which is a similar structural system as used at the Champlain Towers South building that collapsed on June 24. Flat plates are concrete slabs supported on columns.
For that work, she used half-scale concrete models, determining how long a slab can hold a certain amount of weight. She is now using that data to translate the work into computational models that will provide insight into what happens on a larger scale.
Ultimately, the research could help guide building design, allowing engineers to better predict and account for the behavior of material over time.
“I’m hoping with this additional work and research, we really understand the behavior of these types of structures,” Orton said, “and are able to prevent collapses here and around the world.”