Wind zones map – Belgium
What are the Belgian wind zones according to Eurocode 1 ?
On the map of the national annex, the Belgian area is divided into four wind zones.
| Fundamental value of the basic wind velocity vb,0 | 23 m/s | 24 m/s | 25 m/s | 26 m/s |
|---|
How to adjust the basic wind velocity for each direction of wind and according to return period in Belgium ?
\[\displaystyle v_{b} = c_{prob} \cdot c_{dir} \cdot v_{b,0}\]- 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.
Quelles sont les catégories de terrain en Belgique ?
0 :
Sea or coastal area exposed to the open sea.
I :
Lakes or area with negligible vegetation and without obstacles.
II :
Area with low vegetation such as grass and isolated obstacles (trees, buildings) with separations of at least 20 obstacle heights.
III :
Area with regular cover of vegetation or buildings or with isolated obstacles with separations of maximum 20 obstacle heights (such as villages, suburban terrain, permanent forest).
IV :
Area in which at least 15% of the surface is covered with buildings and their average height exceeds 15m.
Eurocodes Zoning lets you obtain the wind zones free of charge from a GPS point
Example of results given by the software Eurocodes Zoning
B1 – Localization
- Coordinates in World Geodetic System 1984 (WGS84) 4.9053°, 50.2445°
- Coordinates in Belgian Geodetic System 2008 (Lambert 2008) 688279m, 603864m
Address Rondchêne, 5500 Dinant, Wallonie
B2 – Altitudes
| Coordinates | 4.9013°, 50.241° | 4.9044°, 50.2436° | ||
|---|---|---|---|---|
| Elevations | 96m | 189m | ||
| Obstacle effective height H | 93m | |||
| Slope actual length Lu / Ld | 361.4m | |||
| Slope angle Φ | 25.7% | |||
| Horizontal distance site/top x | 121.2m | |||
| Elevation at the place of construction | 197m | |||
B3 – Building
- Type of building : common building with floors (apartments and/or office spaces)
- Design working life category : 100 years
- Max height : 7.0m
- Orientation from North : 35°
B4 – Terrain categories
| Sectors | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Categories | II | II | III | II |
C1 – Snow
NBN EN 1991-1-3 ANB (october 2007)
- Zone Belgium : (sk,0 = 0.5 kN/m²)
- Criteria for zoning : Dinant, Namur
- Characteristic value of snow on the ground at the relevant site : sk,197 = 0.613 kN/m²
- Ground snow load with a return period of 100 years : s100 ans = 0.695 kN/m²
C2 – Wind
NBN EN 1991-1-4 ANB (december 2010)
- Zone : 24.0 m/s
- Criteria for zoning : Dinant, Namur
- Zone cdir : Belgium
| Sectors | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Sector definition | from 350 ° to 80 ° | from 80 ° to 170 ° | from 170 ° to 260 ° | from 260 ° to 350 ° |
| 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 | 1.0 | 0.983 | 1.0 | 1.0 |
| Basic wind velocity vb | 24.9m/s | 24.5m/s | 24.9m/s | 24.9m/s |
| Reference roughness length z0,II | 0.05m | |||
| Roughness length z0 | 0.05m | 0.05m | 0.3m | 0.05m |
| Terrain factor kr | 0.19 | 0.19 | 0.215 | 0.19 |
| Height above ground z | 7.0m | |||
| Minimum height zmin | 2.0m | 2.0m | 5.0m | 2.0m |
| Roughness factor cr(z) | 0.939 | 0.939 | 0.678 | 0.939 |
| Obstacle type | cliffs | |||
| Exposure type | – | – | downwind | – |
| Factor depending on the type and dimensions of the obstacle s max | 0.0 | 0.0 | 0.598 | 0.0 |
| Orography factor * co(z) | 1.0 | 1.0 | 1.308 | 1.0 |
| Mean wind velocity vm(z) | 23.4m/s | 23.0m/s | 22.1m/s | 23.4m/s |
| Turbulence factor kl | 0.995 | 0.995 | 1.247 | 0.995 |
| Standard deviation of the turbulence σv | 4.713m/s | 4.634m/s | 6.696m/s | 4.713m/s |
| Turbulence intensity Iv(z) | 0.201 | 0.201 | 0.303 | 0.201 |
| Air density ρ | 1.225kg/m3 | |||
| Exposure factor ce(z) | 2.124 | 2.124 | 2.456 | 1.124 |
| Peak velocity pressure qp(z) | 824.7N/m2 | 797.5N/m2 | 953.3N/m2 | 824.7N/m2 |
| Peak wind velocity for Serviceability Limit States vp(z),SLS | 130.8km/h | 128.6km/h | 140.6km/h | 130.8km/h |
| Peak wind velocity for Ultimate Limit States vp(z),ULS | 160.2km/h | 157.5km/h | 172.2km/h | 160.2km/h |
C3 – Seism
NBN EN 1998-1 ANB (october 2011)
- Zone : 1 (0,39 m/s²)
- Criteria for zoning : Dinant, Namur
- A seismic analysis may be required for this building.