A building should be able to lose a supporting column without losing everything around it. Achieving that is a demanding engineering problem: once one support fails, the loads it carried have to go somewhere else.
Researchers led by the University of Surrey have developed a simpler way to assess how reinforced concrete floors respond to that sudden change. Their method could help engineers design structures that better withstand unexpected damage, reducing the risk of an initial failure spreading through a building.
The work focuses on flat-slab construction, where concrete floor slabs are supported directly by columns. Common in car parks, offices and residential buildings, this arrangement makes efficient use of space and offers flexibility in how interiors are laid out.
One vulnerability is ‘punching shear’. This occurs when a column effectively punches through the concrete slab it supports. When that connection fails, loads are redistributed to neighbouring supports. If those connections cannot withstand the additional demand, further failures can follow, potentially triggering progressive collapse.
Advertisement
The challenge for engineers is assessing that response and deciding what reinforcement is needed to stop the damage spreading. A sudden loss of support introduces dynamic effects, making the problem more complicated than simply calculating the loads on an undamaged floor.
Working with Universidad Politécnica de Madrid, Universidad de Extremadura and engineering practice Skidmore, Owings & Merrill, the researchers developed equations that simplify some of the calculations previously required.
The method builds on earlier mathematical models and is compatible with the next generation of Eurocode 2, the European standard for designing concrete structures. That compatibility could make it easier to incorporate the approach into established design practices.
‘The loss of a single column should not mean the loss of an entire building,’ said Professor Juan Sagaseta, professor of structural robustness at Surrey. ‘That’s why we’ve worked to make these safety checks easier to carry out, helping engineers make better-informed decisions and ultimately protect the people who use these buildings.’
To test their approach, the team compared its predictions with existing experimental results and data from the Nueva Montaña car park collapse in Santander, Spain, in 2020.
Advertisement
The equations successfully predicted the type of failure observed around a neighbouring column at the site. The findings also indicated that the method could be applied where several columns are suddenly lost.
Lead author Dr Maria Liapopoulou, now a Brunel Fellow at the University of Cambridge, carried out the research while working at Surrey. She said the agreement between the calculations and the real collapse gave the team greater confidence in the method’s practical potential.
The work could inform future improvements to structural design guidance. Its contribution is a more accessible way to examine how damage might spread, giving engineers another means of assessing whether a local failure could have disproportionate consequences.
For designers, that means a clearer basis for decisions about reinforcement and structural robustness, with the aim of keeping an unexpected loss of support from becoming a much larger failure.
The research is published in Structural Concrete.