Engineers at the University of Surrey and partner institutions have developed a simpler way to assess how reinforced concrete floors behave when a supporting column suddenly fails. The method could help designers prevent a single failure from spreading into the collapse of a whole building.The research targets a failure mode called punching shear. It aims to help engineers design buildings that better withstand unexpected structural damage.How slabs can failCar parks, office blocks and apartment developments are often built with concrete slabs supported directly by columns, forming each floor. The layout gives designers flexibility and makes efficient use of space.But it can be vulnerable to punching shear, in which a column effectively punches through the slab above it. If the load suddenly shifts to neighboring columns, the added stress can trigger a chain reaction known as progressive collapse.The 2020 collapse of the Nueva Montaña car park in Santander, Spain, showed the danger of this type of failure.A simpler assessment methodThe team worked with Universidad Politécnica de Madrid, Universidad de Extremadura and industry partner Skidmore, Owings & Merrill (SOM). Building on earlier mathematical models, they developed a set of equations that removes the need for some of the more complex calculations previously required.Engineers can use the method to estimate how much reinforcement may be needed to prevent further structural failure. It is also compatible with the next generation of Eurocode 2, the European standard for designing concrete structures, so it can slot into existing practice.Tested against santander collapseThe researchers checked the equations against existing experimental results and new data from the Nueva Montaña collapse. The calculations successfully predicted the type of failure seen at the site, which developed around a neighboring column.They also showed that the method can handle situations in which several columns are lost at once.Lead author Dr. Maria Liapopoulou did the work as a research fellow at Surrey and is now a Brunel Fellow at the University of Cambridge. She said it was encouraging to see “how closely our calculations matched what actually happened.” Testing a model against a real case, she said, gives greater confidence that it could make a difference in practice.Toward safer design guidanceProfessor Juan Sagaseta of Surrey’s Centre for Civil Infrastructure Systems and Engineering, the study’s corresponding author, said engineers cannot predict every accident that might damage a building. They can, however, design structures so that consequences are not catastrophic. Engineers are “under a lot of pressure to get this right,” he said.A single column loss “should not mean the loss of an entire building,” he said, which is why the team made these checks easier to carry out.The findings could inform future design guidance, helping engineers assess how buildings respond to unexpected damage and keep local failures from growing into wider collapse.The research was published in the journal Structural Concrete.