Concept of robustness and risk in constructions

Any structure (or structural element) must be designed in such a way that, during its expected service life (or period of use), it can, for example :

• withstand, with an appropriate degree of safety, all actions and deformations likely to occur during its construction and operation;

• maintain, in the event of accidental action or defects likely to lead to local failure, a sufficient safety margin against the possibility of collapse from close quarters;

• maintain sufficient resistance and stability in the event of fire;

• demonstrate satisfactory performance in normal operation;

• be suitably durable against biological, chemical, etc. action.

The notion of robustness is thus introduced (second paragraph). According to the French language dictionary, "robuste" is an adjective derived from the Latin robustus, from robur, strength. The first definition is that what is robust is solidly built, capable of sustaining great physical effort and resisting fatigue. Alternatively, what is robust is capable of resisting the causes of aggression or alteration (a robust constitution).

In the field of civil engineering, robustness is the ability of a structure "to withstand unforeseen adverse events without being damaged to an extent disproportionate to the original cause". The notion of robustness was introduced into the Eurocodes gradually, as its definition and rules of application were very difficult to include in an international standard, even if the concept seems simple and obvious.