Designing a resilient and structurally sound roof is important in construction projects, and one crucial aspect that demands is the consideration of wind loads. In this context, the European standard EN 1991-1-4 NF provides a comprehensive framework for determining wind actions on buildings, helping architects and engineers ensure the safety and stability of structures.

Assumptions for the calculation of the loads on a duopitch roof

Wind EN 1991-1-4 NF calculation example for a duopitch roof

Wind EN 1991-1-4 NF calculation example for a duopitch roof - properties

**CsCd calculation for X+ direction:**

h = 7.6284831 m

reevaluate Iv(z) for CsCd at z = 0.6 h = 4.5771 m

but zmin > z => z = 9 m => we don’t need to reevaluate Iv (z), it is the same as above

External pressure coefficients for duopitch roofs

External pressure coefficients for duopitch roofs

The area of each slope is 207.18738 m^{2} and the pitch angle is 10.31° so the cpe10 values are extracted from Table 7.4a for X+ direction and Table 7.4b for Y+ direction.

**X+:**

**cpe10_1 cpe10_2**

- [F] -1.27494077 0.106264806
- [G] -0.98747039 0.106264806
- [H] -0.44060279 0.106264806
- [I] -0.49373519 0.093735194
- [J] -0.81252961 0.093735194

Also, both values of Cpi values, +0.2 and -0.3 (the default option in the Cpe cpi dialog) are used resulting in 4 load cases for the same direction.

CsCd is considered the same for the entire building per wind direction. The value for X+ is calculated above.

For the F zones:

- w F cpe10_1&cpi1 = c
_{s}c_{d}∙ q_{p}(z_{e}) ∙ -1.27494 - q_{p}(z_{i}) ∙ 0.2 = 550.18769 N/m2 (in WX+S load case) - w F cpe10_2&cpi1 = c
_{s}c_{d}∙ q_{p}(z_{e}) ∙ 0.106265 - q_{p}(z_{i}) ∙ 0.2 = 45.64301 N/m2 (in WX+D load case) - w F cpe10_1&cpi2 = c
_{s}c_{d}∙ q_{p}(z_{e}) ∙ -1.27494 - q_{p}(z_{i}) ∙ -0.3 = 339.03569 N/m2 (in WX+S2 load case) - w F cpe10_2&cpi2 = c
_{s}c_{d}∙ q_{p}(z_{e}) ∙ 0.1062648 - q_{p}(z_{i}) ∙ -0.3 =**-**165.50899 N/m2 (in WX+D2 load case).

Like all above the position and the geometry of the loads based on the zones provided by Figure 7.8 on the roof are calculated automatically. All the loads and the load cases are automatically generated.

e = 15.257 m

For the F zones:

- w F cpe10_1&cpi1 = c
_{s}c_{d}∙ q_{p}(z_{e}) ∙ -1.27494 - q_{p}(z_{i}) ∙ 0.2 = 557.14567 N/m2 (in WY+S load case) - w F cpe10_1&cpi2 = c
_{s}c_{d}∙ q_{p}(z_{e}) ∙ -1.27494 - q_{p}(z_{i}) ∙ -0.3 = 345.9937 N/m2 (in WY+D load case)

e = 15.2569 m

The resulting loads are: