Starting with Advance Design 2013, the automatic generation of wind forces according to the EC1 norm (EN 1991-1-4) can be realized by using different wind characteristics for different wind directions. This is useful especially when designing structures which have their faces exposed to different terrain categories (for example structures having one face oriented to the sea, while the others are exposed to different terrain categories (with smaller wind forces) - Figure 1).
Figure 1. Terrain categories 0 and IV
(Sea and Town terrain)
For example, we consider the storehouse from Figure 2. Its location on site makes the face exposed in the +X direction to be characterized by terrain category I, and terrain category II for the face exposed in the +Y direction. Taking into account these characteristics, the terrain roughness will have different values on the two exposed faces.
Note: The terrain roughness is quantified by the roughness factor cr(z), which accounts for the variability of the mean wind velocity at the site of the structure (chapter 4.3.2, EN 1991-1-4).
Figure 2. 3D view of the analyzed structure
For example, in Figure 2, only +X and +Y wind directions are considered. Similarly, the other wind directions can be analyzed.
In order to obtain the corresponding forces for this situation the following steps are performed:
- Taking into account that there are different wind characteristics, the option "Per direction" from the "Wind definition" cell is chosen (Figure 3).
- For the first wind direction considered, in the "Current wind direction" cell, "X+" is chosen (Figure 3). Choose the terrain category (I) and the other wind characteristics considered for this direction.
- For the second wind direction considered, in the "Current wind direction" cell, "Y+" is chosen (Figure 4). Choose the terrain category (II) and the other wind characteristics considered for this direction.
Figure 3. Wind EN 1991-1-4 - +X direction
Figure 4. Wind EN 1991-1-4 - +Y direction
Using the characteristics from Figure 3 and Figure 4, the wind loadings on the +X and +Y directions are generated. This can be done from the Pilot by right-clicking on the load case family "Wind EN 1991-1-4" and by choosing the "Automatic generation" option (Figure 5). The structure with the wind loadings is presented in Figure 6.
Figure 5. Automatic generation of wind forces
Figure 6. Wind forces obtained with automatic generation