« Imposed loads Combinations of actions »


Design values of actions

Non-seismic actions

The design value (Fd) of an action [EC0, 6.3.] is equal to the product of the characteristic value Fk times the factor γf (Fdf·Fk). The values of γg (multiplying the permanent values Gk) and γq (multiplying the variable values Qk) are stated on the following table [EC0, table A1.2(B)].


In certain structures, taking account of the uncertainties in modelling effects of actions or in modelling the actions, a second partial factor γ Sd is involved in the calculation affecting the actions safety factor γFSd·γfGSd·γg, γQSd·γq). Although the value of γSd depends on the designer, in such cases, its value usually varies between 1.05 and 1.15.

Seismic actions

Vibrations produced by earthquakes cause seismic accelerations to the structure. The structure's seismic response depends on the seismic Zone Z of the building, the Type of Soil, the Factor of Importance γI, the Viscous Damping ξ, the Behaviour Factor q and of course the magnitude and distribution of stiffness EI and the mass M of the structure.

Calculations, simple or extremely complicated (§6.3), result, for every seismic combination i, at each position of the structure j with mass Mj, to the maximum seismic design acceleration ai,j,. The design seismic force for the combination i at position j is equal to Fi,j=a i,j·Mj.Forces Fi,j represent the Seismic Actions.


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