EN 1991-1-4 Wind Loads Family

 

The EN 1991-1-4 Wind loads family is created when the Eurocode 1 (EC1) - General climatic standard is selected for the current project.

EN 1991-1-4 Wind loads family properties

EN 1991-1-4 Wind loads family - Properties

Family
Automatic generation

Allows enabling / disabling the automatic wind generation components (i.e., loading areas exposure, split loading areas, loads generation, automatic Cpe and Cpi calculation).

Wind direction: Select the wind direction (WindX+, WindX-,WindY+, WindY-)

Horizontal setbacks

Horizontal setbacks

Downwind setback

Upwind setback

Upwind setback

Wind loads on Awning load areas

- Default cpe calculation. By using this option, the cpe is chosen based on the area of the load area (and the coplanar ones).

* If the area A <= 1 m2 then cpe = cpe1

* If the area A >= 10 m2 then cpe = cpe10

* else the Figure 7.2 is used:

- cpe10. Only the cpe10 values are extracted from the tables.

- cpe1. Only the cpe1 values are extracted from the tables.

The default behaviour is that the cpe values are extracted from the Table 7.4a for positive slope angles. The user can change this by selecting the negative slope or the max cpe option. The negative option will determine the extraction of the cpe values for each pitch angle as if they would be negative. If the max cpe option is used, then for each pitch angle the values of cpe for the |α| and -|α| are compared and the maximum absolute value, with sign, is used further in the automatic calculation. For example for α = 150 , F zone and cpe10, between -1.9 and -1.3 we choose -1.9.

- per direction:: The user can define parameters for each wind direction.

- all directions: The fields are defined the same for all directions.

Dynamic base pressure

NOTE The lack of correlation of wind pressures between the windward and leeward side may be considered as follows. For buildings with h/d ≥ 5 the resulting force is multiplied by 1. For buildings with h/d ≤ 1, the resulting force is multiplied by 0,85. For intermediate values of h/d, linear interpolation may be applied.

The available options are:

- ‘No’ option means that Kdc = 1.

- ‘Imposed’ implies that Kdc can impose the value.

- ‘Auto’ means that Kdc is the interpolated value between 0.85 and 1 depending on 1 < H/d < 5.

Terrain category

Z0 (m)

Zmin (m)

0 - Sea or coastal area exposed to the open sea

0.003

1

I - Lakes or flat and horizontal area with negligible vegetation, without obstacles

0.01

1

II - Area with low vegetation such as grass and isolated obstacles (trees, buildings) with separations of at least 20 obstacle heights

0.05

2

III - Area with regular cover of vegetation or buildings, or with isolated obstacles with separations of maximum 20 obstacle heights (such as villages, suburban terrain, permanent forest)

0.3

5

IV - Area in which at least 15 % of the surface is covered with buildings and their average height exceeds 15 m

1.0

10

Site effect

- Use of Cf (for portal frame design) generates loads obtained from force coefficients.

- Use of Cp,net (for purlins design) uses the net pressure coefficients to generate the maximum local loads. It is useful in the design of roofing elements (e.g., purlins).

- Both - both of the above options are taken into account.

There are three options:

- 0: There will be automatically generated loads for φ max and φ = 0.

- 1: There will be automatically generated loads for φ max and φ = 1.

- Other: The user can impose the value of φ  in the ‚Obstruction value(φ)’ field. There will be automatically generated loads for φ max, φ = 0, φ = 1 and the user imposed value.

- Only exposed area: load position is influenced by wind direction;

- All areas: the 4 load positions from Figure 7.16 from EN1991-1-4 are considered, regardless of the wind direction.

Dynamic effect - The calculated values in this category (Cr(z), Iv(z), ce(z) and qpz) values are depending on h and they are only informative. They are recalculated in the automatic generated process, and the values might differ for various elements or parts of the elements depending of the height of that element/part of the element/building.
Combinations

Define properties that are taken into account when generating concomitance combinations. See Configuring load cases combinations.

Color

Tip

Click a section of the properties window. Notice the bottom area of the window; it displays a short description of the active cell's content.

 

Note

The following articles from EC1 are not implemented:

Accessing the properties

After creating a wind load case family: in the Project Browser, expand the Loading group and select Wind EN 1991-1-4.

See Also