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    • Snow zones map – Belgium

    Image pour illustrer les zones de neiges

    What are the Belgian snow zones according to Eurocode 1 (NBN EN 1991-1-3 ANB) ?

    The Belgian territory is not divided (so there is no map in the national annex). sk0 = 0.50 kN/m²

    How to determine the influence of elevation on the ground snow load in Belgium ?

    Snow loads are calculated as follows:

    • Up to 100m :
    \[\displaystyle s_{k} = s_{k,0}\]
    • From 100m to 700m where A is the elevation of the site :
    \[\displaystyle s_{k} = s_{k,0} + 0.007 \cdot \frac{A – 100}{6}\]

    How to adjust the ground snow load according to return period in Belgium ?

    \[\displaystyle s_{n} = s_{k} \cdot \left[ \frac{ 1 – V \cdot \frac{\sqrt 6 }{\pi} \cdot [\ln(-\ln(1-P_{n})) + 0.57722] } {(1 + 2.5923 \cdot V)} \right]\]
    • Pn  is the annual probability of exceedence :
    \[\displaystyle P_{n} = \frac{1}{dwl}\]
    • dwl is the design working life, in years.
    • V is the coefficient of variation of annual maximum snow load, calculated as follow :
    \[\displaystyle V = \frac{1.01 + 0.00248 \cdot A}{1 + 0.00614 \cdot A}\]
    • It should not be applied for annual probabilities of exceedence greater than 0,2 (i.e. return period less than approximately 5 years).

    Eurocodes Zoning lets you obtain snow loads 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

    Coordinates4.9013°, 50.241°4.9044°, 50.2436°
    Elevations96m189m
    Obstacle effective height H93m
    Slope actual length Lu / Ld 361.4m
    Slope angle Φ 25.7%
    Horizontal distance site/top x121.2m
    Elevation at the place of construction197m

    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

    Sectors1234
    CategoriesIIIIIIIII
    Radius R of the angular sector 300m

    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
    Sectors1234
    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 n0.5
    Annual probability of exceedence p0.01
    Probability factor  cprob 1.038
    Directional factor  cdir 1.00.9831.01.0
    Basic wind velocity  vb 24.9m/s24.5m/s24.9m/s24.9m/s
    Reference roughness length  z0,II 0.05m
    Roughness length  z0 0.05m0.05m0.3m0.05m
    Terrain factor  kr 0.190.190.2150.19
    Height above ground z7.0m
    Minimum height  zmin 2.0m2.0m5.0m2.0m
    Roughness factor  cr(z) 0.9390.9390.6780.939
    Obstacle typecliffs
    Exposure type––downwind–
    Factor depending on the type and dimensions of the obstacle  s max 0.00.00.5980.0
    Orography factor  * co(z) 1.01.01.3081.0
    Mean wind velocity  vm(z) 23.4m/s23.0m/s22.1m/s23.4m/s
    Turbulence factor  kl 0.9950.9951.2470.995
    Standard deviation of the turbulence  σv 4.713m/s4.634m/s6.696m/s4.713m/s
    Turbulence intensity  Iv(z) 0.2010.2010.3030.201
    Air density  ρ 1.225kg/m3
    Exposure factor  ce(z) 2.1242.1242.4561.124
    Peak velocity pressure qp(z) 824.7N/m2797.5N/m2953.3N/m2824.7N/m2
    Peak wind velocity for Serviceability Limit States  vp(z),SLS 130.8km/h128.6km/h140.6km/h130.8km/h
    Peak wind velocity for Ultimate Limit States  vp(z),ULS 160.2km/h157.5km/h172.2km/h160.2km/h
    * The orography factor is calculated for a well individualized obstacle (an emergent zone compared to a general ground without marked relief)

    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.
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