Glossary · Snow and wind
Characteristic wind pressure W₀
The mean wind pressure at 10 m height exceeded on average once in 50 years; Kyiv has 370 Pa under DBN V.1.2-2:2006.
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Definition
Under clause 9.6 of DBN V.1.2-2:2006, W₀ is the mean (static) component of wind pressure at 10 m above ground that may be exceeded on average once in 50 years. It is read from the wind zoning map (Fig. 9.1) or from the table of cities in Annex E. As with snow, the norm allows statistical processing of site wind measurements.
The 10 m height matters. A ground-mounted table has its top edge at 2–3 m, where the wind is weaker, so W₀ is converted with the height factor Ch and then multiplied by the panel’s aerodynamic coefficient:
Wm = γfm · W0 · C, C = Caer · Ch · Calt · Crel · Cdir · CdExample: Kyiv
Kyiv has W₀ = 370 Pa. The highest values among the regional centres are 520 Pa in Lviv, Ternopil and Rivne; Kherson has 480 Pa and Uzhhorod 370 Pa. For a table topping out at 2 m in terrain type II, Ch = 0.7, so the design pressure before the aerodynamic coefficient is 370 · 0.7 = 259 Pa. On a panel at 30° with an uplift coefficient of 1.8 that becomes 466 Pa trying to lift the table.
Unlike snow, wind acts both ways: it presses the panel down and lifts it. For ballasted ground tables it is usually the uplift that sets the block mass, see uplift and sliding.
How Solispec applies it
Solispec takes W₀ from the same table of 22 regional centres as S₀ (or your own value) and computes Wm = γfm · W₀ · Ch · Calt at the height of the array top. The topography, direction and dynamic factors are taken as 1 (clauses 9.11–9.13 for low structures on level ground), and the panel’s aerodynamic coefficient comes from Table 7.6 of EN 1991-1-4:2005.
Norms and clauses
- DBN V.1.2-2:2006, cl. 9.6, Fig. 9.1, Annex E
- DBN V.1.2-2:2006, formulae (9.1), (9.3)
Related terms
- Limit design wind load WmThe wind load used for strength checks: W_m = γ_fm · W₀ · C, where C covers aerodynamics, height, topography and dynamics.
- Height factor ChThe wind correction for height above ground and terrain type, Table 9.01 of DBN V.1.2-2:2006: 0.7 at 5 m and 0.9 at 10 m for type II.
- Terrain type I–IVThe wind classification of a structure’s surroundings under cl. 9.9 of DBN V.1.2-2:2006: from open water (I) to dense urban areas (IV).
- Aerodynamic coefficient Caer (cf)The multiplier turning wind pressure into force on a shape; for panels Solispec takes c_f from Table 7.6 of EN 1991-1-4:2005, as cl. 9.8 of the DBN allows.
- Wind uplift and slidingThe two checks of a ballasted table: wind must neither lift the structure nor slide it across the ground or roof.
- Characteristic snow load S₀The weight of snow cover per 1 m² of ground exceeded on average once in 50 years; under DBN V.1.2-2:2006 Kyiv has 1,550 Pa.
- DBN V.1.2-2:2006 “Loads and actions”: what matters for a solar plantNorms explained
Solispec’s calculation is preliminary: for a design it has to be checked by an engineer. The values and clauses follow the current editions of the norms on the date of the page.