Towers may be strengthened to stop house-of-cards collapses

Structural engineers at New York-based Thornton-Tomasetti and Arup said strengthening certain floors with trusses and supports would prevent the house-of-cards effect that occurred on 11 September.

Emmanuel Velivasakis, managing principal at Thornton-Tomasetti subsidiary LZA Technology, said:

"To me, it is not difficult to design this. You can design a mechanical floor to contain a collapse. You could lose one-third of the building but not all of it."

Arup has suggested a similar solution. A report by the engineer said: "What if we incorporated 'collapse' storeys every 10 floors … designed to carry the debris from the nine storeys above?"

All of us are doing a lot of soul searching. To me, things will change. Our codes will definitely change

Emmanuel Velivasakis, managing principal at LZA Technology

Velivasakis said structural codes would change in the USA. He said: "All of us are doing a lot of soul searching at this point. To me, things will change. Our codes will definitely change."

He said the changes might be targeted at commercial buildings, and would be similar to the overhaul that occurred in the wake of the 1995 Oklahoma bombing, where back-up structures were introduced to contain bomb blasts. The changes could raise building costs 30%.

A review of the part of the Building Regulations dealing with structure may be revised because of the New York disaster.

Sue Doran, director of technical activities at the Institution of Structural Engineers, said: "The institution has set up a working party to look at the events in New York. I am sure some of this will feed through into Part A, particularly the section on disproportionate collapse."