Alcan Structural Engineering

Vertical component of the seismic action

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(1) If avg is greater than 0,25 g (2,5 m/s2) the vertical component of the seismic action, as defined in 3.2.2.3, should be taken into account in the cases listed below:

- for horizontal or nearly horizontal structural members spanning 20 m or more;

- for horizontal or nearly horizontal cantilever components longer than 5 m;

- for horizontal or nearly horizontal pre-stressed components;

- for beams supporting columns;

- in base-isolated structures.

(2) The analysis for determining the effects of the vertical component of the seismic action may be based on a partial model of the structure, which includes the elements on which the vertical component is considered to act (e.g. those listed in the previous paragraph) and takes into account the stiffness of the adjacent elements.

(3) The effects of the vertical component need be taken into account only for the elements under consideration (e.g. those listed in (1) of this subclause) and their directly associated supporting elements or substructures.

(4) If the horizontal components of the seismic action are also relevant for these elements, the rules in 4.3.3.5.1(2) may be applied, extended to three components of the seismic action. Alternatively, all three of the following combinations may be used for the computation of the action effects:

a) EEdx "+" 0,30 EEdy "+" 0,30 EeAz (4.20)

b) 0,30 ¿Edx "+" EEdy "+" 0,30 EEdz (4.21)

c) 0,30 EEdx "+" 0,30 EEdy "+" EEdz (4.22) where

"+" implies "to be combined with''; EEdx and EEdy are as in 4.3.3.5.1(3);

EEdz represents the action effects due to the application of the vertical component of the design seismic action as defined in 3.2.2.5(5) and (6).

(5) If non-linear static (pushover) analysis is performed, the vertical component of the seismic action may be neglected.

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