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On the map of the national annex, the French metropolitan area is divided into four wind zones identified from 1 to 4. Amendment A3, published in April 2019, replaces the division by cantons into a division by municipalities.
Zone | 1 | 2 | 3 | 4 |
---|---|---|---|---|
Fundamental value of the basic wind velocity vb,0 | 22m/s | 24m/s | 26m/s | 28m/s |
Zone | French Guiana | Mayotte Island | Martinique Island | Reunion Island | Guadeloupe Island |
---|---|---|---|---|---|
Fundamental value of the basic wind velocity vb,0 | 17m/s | 30m/s | 32m/s | 34m/s | 36m/s |
Zone | New Caledonia | Wallis and Futuna | Saint Martin | Saint Barths | Saint Pierre and Miquelon |
---|---|---|---|---|---|
Fundamental value of the basic wind velocity vb,0 | 36m/s | 41.2m/s | 36m/s | 36m/s | 36m/s |
A variation have to be considered with the probability factor cprob.
When the wind comes from a direction where the probability of occurrence of strong winds is less, a reduction can be considered with the directional factor cdir.
You should also take in account the effect of the roughness of the terrain (vegetation / urbanization) and the effect of orography (terrain relief) to accurately determine the peak velocity pressure for each wind direction.
The terrain categories have been transposed to Caledonian landscapes. The reference to terrain category IV is removed and categories 0 to III of standard NF EN 1991-1-4 are illustrated by the photographs below :
Distances / Direction | At the place of construction | 500m | 1000m |
---|---|---|---|
North | 436 m | 360m | 407m |
Northeast | 405m | 465m | |
East | 456m | 473m | |
Southeast | 419m | 446m | |
South | 449m | 476m | |
Southwest | 432m | 411m | |
West | 360m | 468m | |
Northwest | 403m | 452m |
Sectors | 1 | 2 | 3 | 4 |
---|---|---|---|---|
Categories | IIIa | IV | IV | IV |
Sectors | 1 | 2 | 3 | 4 |
---|---|---|---|---|
Sector definition | from 35° to 125° | from 125° to 215° | from 215° to 305° | from 305° to 35° |
Fundamental value of the basic wind velocity vb,0 | 24.0m/s | |||
Shape parameter K | 0.2 | |||
Exponent n | 0.5 | |||
Annual probability of exceedence p | 0.01 | |||
Probability factor cprob | 1.038 | |||
Directional factor cdir | 0.7 | 1.0 | 1.0 | 1.0 |
Basic wind velocity vb | 17.4m/s | 24.9m/s | 24.9m/s | 24.9m/s |
Reference roughness length z0,II | 0.05m | |||
Roughness length z0 | 0.2m | 1.0m | 1.0m | 1.0m |
Terrain factor kr | 0.209 | 0.234 | 0.234 | 0.234 |
Height above ground z | 15.0m | |||
Minimum height zmin | 5.0m | 15.0m | 15.0m | 15.0m |
Roughness factor cr(z) | 0.904 | 0.635 | 0.635 | 0.635 |
Orography factor* co(z) | 1.0 | 1.0 | 1.0 | 1.0 |
Mean wind velocity vm(z) | 15.8m/s | 15.8m/s | 15.8m/s | 15.8m/s |
Turbulence factor kl | 0.97 | 0.854 | 0.854 | 0.854 |
Standard deviation of the turbulence σv | 3.544m/s | 4.989m/s | 4.989m/s | 4.989m/s |
Turbulence intensity Iv(z) | 0.225 | 0.315 | 0.315 | 0.315 |
Air density ρ | 1.225kg/m3 | |||
Exposure factor ce(z) | 2.102 | 1.292 | 1.292 | 1.292 |
Peak velocity pressure qp(z) | 392.0N/m2 | 491.5N/m2 | 491.5N/m2 | 491.5N/m2 |
Peak wind velocity for Serviceability Limit States vp(z),SLS | 91.1km/h | 102.0km/h | 102.0km/h | 102.0km/h |
Peak wind velocity for Ultimate Limit States vp(z),ULS | 111.5km/h | 124.9km/h | 124.9km/h | 124.9km/h |