Design situations

Design situations are conditions in which the structure finds itself at different moments in its working life.

In normal use, the structure is in a persistent situation; under temporary conditions, such as when it is being built or repaired, the structure is in a transient situation; under exceptional conditions, such as during a fire or explosion, the structure is in an accidental situation or (if caused by an earthquake) a seismic situation. [en 1990 ยง3.2(2)P]

Society is willing to accept that fires and explosions may lead to building damage - necessitating repair - whereas snow and wind should not. None of these events must lead to collapse. The Structural Eurocodes define partial factors for accidental and seismic situations (i.e. exceptional conditions which are unlikely to occur) that are typically 1.0. These factors are considerably lower than those specified for persistent and transient situations (conditions which are more likely to occur), typically 1.2-1.5. The development of different design situations helps to determine what level of reliability the design requires and what actions need to be considered as part of that design situation.

| Functioning of the structure irreversible

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