On the Disproportionate Collapse Risk and Robustness in the Eurocode

Abstract

After the partial collapse of Roman Point residential tower in London in 1968, the tensile catenary, or the known tie-forces’ method, is the norm for robustness check of building in risk classes A and B2 of the Eurocodes. This method is discussed here in light with recent developments in testing and simulation. It is shown that this principle can be further improved, for example it can be proven that the tie-forces are inefficient for the corner assemblies, and without sufficient lateral stiffness, it increases the risk of pull-down of other parts of the structure.

The risk index, informative in the code, is discussed focusing on probability of structural failure as a result of structural damage. The index can be extended to cover structural robustness against disproportionate progressive collapse. It is found that if uncertainty in model is considered, the index becomes inconsistent. A modification is proposed and supported by example limit-state functions appropriate for the new purpose.

Along the line of structural robustness, disaster-safety can be considered. Bearing economy in mind, development is promoted for the informative part of the code. While clue is available that engineered structures preserve certain level of structural robustness, need for research is called for. In this call, unavoidable progressive collapse can be delayed giving users chance to escape which eliminates lives’ risk under collapse.