# Consideration of the Correlation with Wind Loads

### Tips & Tricks

001517 2 May 2018
If the wind load for buildings or structures is to be determined by the simultaneous assumption of aerodynamic pressure and suction coefficients on the windward and leeward sides of the building, the correlation of the wind pressure on zones D and E of the wall surfaces may be taken into account.

For buildings with an aspect ratio of h / d = 5, the resulting force is multiplied by 1. For buildings with h / d = 1, the resulting force may be multiplied by 0.85. Intermediate values of h / d are linearly interpolated.

However, it must be ensured that the consideration of this approach [1] can be limited by the National Annex of DIN 1991-1-4. For example, this approach does not apply in [2] Germany according to DIN EN 1991-1-4 / NA.

#### Example

National Annex: CEN

Building height h = 7 m
Building width d = 6 m
Ratio h / d = 1.166667

External pressure coefficients according to Table 7.1:
Zone D: cpe,10 = 0,800
Zone E: cpe,10 = -0,508

Basic wind speed vb, 0 = 20 m / s

Resulting wind load without consideration of the correlation:
Zone D: Zone D: we = 0.56 kN / m²
Zone E: we = -0,35 kN/m²

Resulting wind load with consideration of the correlation:
Zone D: we = 0,56 kN/m² ∙ 0,85 = 0,48 kN/m²
Zone E: we = -0,35 kN/m² ∙ 0,85 = -0,30 kN/m²

Depending on whether the correlation in the respective National Annex is allowed or not, this can be activated in the input table of the wind load generator in RFEM / RSTAB (see Fig. 01).

#### Literature

 [1] Eurocode 1: Actions on structures - Part 1-4: General actions - Wind loads; EN 1991-1-4:2005 + A1:2010 + AC:2010 [2] National Annex - Nationally determined parameters - Eurocode 1: Actions on structures - Part 1-4: General actions - Wind loads; DIN EN 1991-1-4/NA:2010-12