Glossary · Snow and wind
Mean return period T
The 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).
Ground frame designer
Design the ground frame for your solar plant
Solispec picks the profiles and posts, checks the frame against snow and wind to the DBN and prices it down to the last bolt.
- No sign-up
- Snow and wind check
- Drawings and estimate
Definition
The characteristic S₀ and W₀ in DBN V.1.2-2:2006 correspond to 50 years: such a load is exceeded on average once in 50 years. The limit design value for another period is obtained through γfm, which Tables 8.1 and 9.1 give as a function of T.
How is T chosen? For mass construction clauses 8.11 and 9.14 allow T to equal the structure’s service life Tef. For structures of higher importance, where the brief sets a probability P of non-exceedance over the service life, T is computed as:
T = Tef · KpExample: Kyiv
| T, years | γfm snow | Sm on a flat surface |
|---|---|---|
| 25 | ≈ 0.86 | ≈ 1,337 Pa |
| 50 | 1.00 | 1,550 Pa |
| 100 | 1.14 | 1,767 Pa |
Cutting the term to 25 years reduces snow by about 14 %. It is tempting, but panels usually carry a 25–30-year power warranty and the structure often outlives the first set of modules. That is why 50 years is a sensible default for the frame. For wind, Table 9.1 has the same anchor points: 1.00 for 50 years and 1.14 for 100.
How Solispec applies it
In Solispec the structure’s service life is entered in years, 50 by default. The engine takes T equal to it (as allowed for mass construction) and interpolates γfm for snow and wind from it. The probabilistic formula T = Tef · Kp is not used by the engine.
Norms and clauses
- DBN V.1.2-2:2006, cl. 8.11, 9.14, Tables 8.1, 8.2, 9.1, 9.2, formulae (8.6), (9.6)
Related terms
- Reliability factor for the limit value γfmThe 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).
- 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).
- 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.
- Characteristic wind pressure W₀The 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.
- 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.