Glossary · Snow and wind
Reliability factor for the limit value γfm
The multiplier on S₀ and W₀ that depends on the mean return period T: 1.00 at 50 years, 1.14 at 100 years (Tables 8.1, 9.1).
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Definition
In DBN V.1.2-2:2006 the characteristic S₀ and W₀ refer to a 50-year period. If a structure is meant to last longer or shorter, the limit value is adjusted with γfm. For snow it comes from Table 8.1 (cl. 8.11), for wind from Table 9.1 (cl. 9.14). Intermediate values are interpolated linearly.
| T, years | γfm, snow (Table 8.1) | γfm, wind (Table 9.1) |
|---|---|---|
| 10 | 0.69 | 0.69 |
| 40 | 0.96 | 0.96 |
| 50 | 1.00 | 1.00 |
| 100 | 1.14 | 1.14 |
| 150 | 1.22 | 1.22 |
For mass construction the norm allows the mean return period to be taken equal to the structure’s service life. For structures of higher importance T is computed as Tef · Kp (formulae 8.6 and 9.6) from the required probability of non-exceedance.
Example: Kyiv
For Kyiv at T = 50 years the limit snow load on a flat surface equals S₀ = 1,550 Pa. At T = 100 years it is 1,550 · 1.14 = 1,767 Pa. If you plan a 25-year plant, the wind γfm is 0.87 (listed in Table 9.1) and the snow one is interpolated between 20 and 40 years: ≈ 0.86.
How Solispec applies it
Norms and clauses
- DBN V.1.2-2:2006, cl. 8.11, 9.14, Tables 8.1, 9.1
Related terms
- Mean return period TThe period in years over which a load is exceeded once on average; γ_fm depends on it (Tables 8.1, 9.1 of DBN V.1.2-2:2006).
- Reliability factor for the serviceability value γfeThe multiplier for serviceability loads (deflections): at η = 0.02 snow 0.49, wind 0.21 (Tables 8.3, 9.3 of DBN V.1.2-2:2006).
- Limit design snow load SmThe snow load on the horizontal projection used for strength checks: S_m = γ_fm · S₀ · C under DBN V.1.2-2:2006.
- 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.
- 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.