Steel Buildings in Europe

Part 3: Actions 3 - 3 2.3 Characteristic values and design values of actions 2.3.1 General Actions shall be classified by their variation in time as follows:  Permanent actions ( G ), e.g. self-weight of structures, fixed equipment, etc.  Variable actions ( Q ), e.g. imposed loads, wind actions, snow loads, etc.  Accidental actions ( A ), e.g. explosions, impact from vehicles, etc. Certain actions may be considered as either accidental and/or variable actions, e.g. seismic actions, snow loads, wind actions with some design situations. 2.3.2 Characteristic values of actions The characteristic value ( F k ) of an action is its principal representative value. As it can be defined on statistical bases, it is chosen so as to correspond to a prescribed probability of not exceeding on the unfavourable side, during a “reference period” taking into account the design working life of the structure. These characteristic values are specified in the various Parts of EN 1991. 2.3.3 Design values of actions The design value F d of an action F can be expressed in general terms as: F d =  f  F k where: F k is the characteristic value of the action  f is a partial factor for the action  is either 1,00,  0 ,  1 or  2 2.3.4 Partial factors Partial factors are used to verify the structures at ULS and SLS. They should be obtained from EN 1990 Annex A1, or from EN 1991 or from the relevant National Annex. 2.3.5  factors In the combinations of actions,  factors apply to variable actions in order to take into account the reduced probability of simultaneous occurrence of their characteristic values. The recommended values for  factors for buildings should be obtained from EN 1990 Annex A1 Table A1.1, or from EN 1991 or from the relevant National Annex.