Wind standard

Fundamental values of the basic wind velocity

Basic wind velocity v_b on the building site during a period of 50 years

Probability coefficient of exceeding

The probability p of exceedance is considered on the useful life of the project, itself based on the use of the project.
For our building project, the use is dwelling house, the recommended duration of use, necessary for determining the return period, is therefore 50 years.
The 10 minutes mean wind velocity having the probability p for an annual exceedence is determined by multiplying the basic wind velocity v_b by the probability factor of severe wind c_prob:
(NTC GAZZETTA UFFICIALE - 3.3.3 (02/2018))

Directional factor of wind

'wind direction' means the direction from which the wind comes.
The Italian standard does not mention a wind direction coefficient to reduce the resulting pressures. We therefore assume that c_dir = 1.

Season factor

The Italian standard does not mention a season factor coefficient to reduce the resulting pressures. We therefore assume that c_season = 1.

The basic wind velocity v_b on the building site, defined for each direction of the wind at 10 m above ground level in terrain of 'open country' type falling into the terrain category II, is shown in the graph below:

with:

Peak velocity pressure q_p

Maximum equivalent peak wind velocity (at the ridge Lvl +5.0 m)

• 105 km/h to control the vibrations and the deformations of the structure at serviceability limit states (SLS).
  
• 129 km/h to control the resistance of the structure at ultimate limit state (ULS).