What is orography?

The orography is the study of the reliefs and in particular of the hills, the mountains or the cliffs.
In wind calculation according to Eurocode 1 part 1-4, the orography is taken in account as a factor which increase the mean wind velocity and the wind turbulence.

How to calculate orography factor?

When the orography increases wind velocity by more than 5%, it is recommended to consider the effects using the co coefficient.
The effects of orography may be neglected when the average slope of the terrain in the wind is less than 3°.
The windward terrain can be considered up to a distance of 10 times the height of the isolated orographic element.

• The general procedure is given in Eurocode 1 part 1-4 §A.3. It is usable in the case of very simple and marked reliefs, such as an isolated hill or an escarpment separating two levels of flat land but is difficult to apply when it is difficult to precisely define a peak or a crest. This procedure involves the slope of the terrain that follows the wind and the position of the construction in relation to the top of the hill or the crest of the escarpment.
• Alternatively, the French National Annex to Eurocode 1 part 1-4 proposes a method based on a statistical approach to the results of numerous numerical simulations. This one is applicable in all circumstances.

How to get orography analysis with Lisa.blue?

Orography is automatically detected with Lisa.blue, and you can update factors manually.
On this example, you can see different orography factor calculated, varying upon every wind.