Learning from 9/11 to make buildings more robust in fire

Award-winning research by Professor Ian Burgess of the University of Sheffield's Department of Civil and Structural Engineering is helping us to understand how we can improve a building's robustness in a fire.

Tragically, one example of how fire can seriously reduce a building's integrity was reflected in the events of September 11th 2001.

The twin towers of the World Trade Centre in New York both survived the impact of the aircraft which were flown into them by terrorists. However, the fuel from the aircraft spilt over many floors of the buildings, ignited and burned at very high temperatures. This caused the steel beams supporting the floors to heat up and expand. This heating caused the beams to become very weak so that they sagged, causing the main columns around the face of the building to collapse. This then produced a "pancaking" effect, with the upper floors falling on to the floors below, destroying the whole structure within seconds.

The concept of robustness which designers increasingly have to adopt is that one part of a building should be able to collapse in a fire without causing the rest of the building to collapse. For a number of years now, Professor Burgess and his team have been involved in an entirely new area of study; how buildings behave in fire situations.

A current project, which is funded by the Engineering and Physical Sciences Research Council, involves putting steel connections in a furnace and heating them to around 700°C. They are then pulled downwards on one side to simulate a sagging beam, and the results are used to develop computer models of the structural behaviour. The work has led to some important breakthroughs in developing new ways of increasing robustness in steel connections.

As Professor Burgess points out, "No matter what the protection level, fire situations can always be worse than are allowed for in design, which makes the inherent robustness of a building incredibly important."

Moreover, the research has produced a number of highly practical applications, including the double-award-winning software Vulcan. In addition, the group's investigation into the behaviour of concrete slabs in fire buildings was awarded the American Society of Civil Engineers' Raymond C. Reese Research Prize in 2005 for two papers published in the Society's Journal of Structural Engineering.

The papers describe developments of Vulcan which enable it to show the mechanisms at work, particularly in composite floor slabs, when structures are at very high temperatures. As a result, Vulcan can be used by structural engineers to help design buildings with the appropriate level of safety against catastrophic collapse in fire.

For further information, please contact Professor Ian Burgess at:

tel: 0114 222 5060

email : ian.burgess@sheffield.ac.uk