Robustness is the ability of a structure to withstand events like fire, explosions, impact or the consequences of human error, without being damaged to an extent disproportionate to the original cause – as defined in EN 1991-1-7 of the Accidental Actions Eurocode.
[2] Buildings of some kinds, especially large-panel systems and precast concrete buildings, are disproportionately more susceptible to collapse; others, such as in situ cast concrete structures, are disproportionately less susceptible.
[2] Three alternative measures are used, sometimes jointly, to achieve structural robustness and reduce the risk of disproportionate collapse.
[2] Buildings in consequence class 1 should be designed and constructed in accordance with EN 1990 - 1999 for satisfying stability in normal use, no specific consideration (required by EN 1991-1-7) is necessary with regard to accidental actions from unidentified causes.
Buildings in consequence class 2b (in addition to what is recommended for consequence class 1 and 2a) should be provided with effective vertical ties in all supporting columns and walls, or alternatively the building should be checked to ensure that upon the notional removal of each supporting column and each beam supporting a column, or any nominal section of load-bearing wall (one at a time in each storey of the building) the building remains stable and the local damage does not exceed a certain limit.