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Wind - CsCd

Details of Wind - CsCd

CsCd factor is not available in SCIA Engineer (cf art.6.1 from EN 1991-1-4) :

"The structural factor CsCd should take into account the effect on wind actions from the non-simultaneous occurrence of peak wind pressures on the surface (Cs) together with the effect of the vibrations of the structure due to turbulence (Cd). 

NOTE The structural factor CsCd may be separated into a size factor Cs and a dynamic factor Cd, based on 6.3. Information on whether the structural factor CsCd should be separated or not may be given in the National Annex."

But there is a little trick to take into account this factor in the software while waiting for its development.

The wind pressure is equal to:

qp * (Cpe*CsCd + Cpi)

[qp*Cpe*CsCd] + [qp*Cpi]

CsCd * qp * [Cpe + (Cpi/CsCd)]

From the version 22 of SCIA Engineer, we can see this qp pressure in the view parameters setting:

A solution could be to:

  •        Manually calculate the CsCd factor,

  •        Multiply the qp pressure by CsCd and manually define it :


  •     Automatically generate wind loads from this customized pressure, taking care of dividing Cpi by CsCd in the wind generator: