Wind loads are climatic loads on buildings, representing variable actions. They result from the pressure distribution around the building that is subject to wind flow. In general, wind loads are applied as surface loads that act perpendicularly on the surfaces, featuring compression and suction effects.
Wind loads are regulated in specific standards, such as EN 1991‑1‑4 [1], ASCE/SEI 7‑16 [2], and NBC 2015 [3]. In the Eurocode, the application area is specified for buildings with heights up to 200 m. This limit may be increased to 300 m for wind profiles valid according to the "German National Annex," for example.
In the standards, wind loads are converted into characteristic values so that the load capacity of buildings can be determined. As these loads represent actions that vary over time and geometry, their distinct stochastic characteristics are accounted for by those values.
For the design values, both the location of the building with its local wind climate and the surrounding topography are essential. The wind climate is recorded in the standards via wind zone maps. In EN 1991‑1‑4 [1], for example, the fundamental basic wind velocities are given. They represent the average values determined over the time the wind takes effect. For detailed information on wind zones according to administrative borders, you can use the Dlubal Geo-Zone Tool to conveniently obtain the values of the basic wind velocity vb,0 and of the velocity pressure qb.
This Knowledge Base article describes in detail how wind loads on mono- and duopitch roofs are to be considered according to EN 1991‑1‑4 [1] in Germany. In another Knowledge Base article, you can find an example of applying wind on vertical walls.
The standards provide information on how to apply wind loads on buildings featuring mainly rectangular shapes. RWIND, however, is able to determine the surface pressure and wind velocities for buildings with any kind of shape. The fundamental (or mean) wind velocity is applied to determine the specific loads of a building – with or without interaction with other buildings – by a numerical wind tunnel simulation. If the wind velocity is defined individually for each level height of the model, the simulation can also be carried out for standards other than EN 1991‑1‑4 [1] or independently of any code.
The wind profiles described in EN 1991‑1‑4 [1] also account for the ground roughness. With the character of the terrain, specific turbulence effects near the ground level and, thus, reduced velocities are associated. EN 1991‑1‑4 [1], Table 4.1, gives the corresponding terrain categories. These turbulence effects are different from the turbulences due to the shape of the building. They are described in the following chapter.