Eurocode _ Wind on Canopy Duopitch Roof 1

[Mina Barsoum]

Hi,

According to Eurocode EN1994-1-4 section 7.3 for wind loads on canopy roofs, the duopitch roofs should have cases for unbalanced loading (where one half of the roof is loaded and the other half is not).

Do you have any idea why this condition is required? It makes no sense that the wind would act on half of the roof and the other half will not be affected.
And it is causing a huge increase in the number of load combinations which make the calculations very slow.

Thanks in advance

 

[HTURKAK]

Pls notice this is a requirement for canopy structures (which does not have permanent walls, such as petrol stations,barns, etc.) which the internal pressure coefficients are zero.

Use it up, wear it out;
Make it do, or do without.

NEW ENGLAND MAXIM

 

[STpipe]

The code is not saying that the wind is only acting on half the roof. The pressure distribution on both halves of a duopitch roof based on the Eurocode diagrams will lead to a net downward or upwards force since the horizontal components will cancel each other out. Applying the pressure on half of the roof ensures that there is a net lateral load for wind design. Other codes like ASCE 7 achieve this by having different pressure values applied on each side of the roof which creates the same effect (One side will be larger than the other creating a net lateral force). You want to design for the worst case lateral load (and overturning moment) when it comes to wind.

It's the same reason the force is applied at the quarter point of the roof for monoslope canopies.

 

[Mina Barsoum]

STPipe,

Thanks a lot for your clarification. Now it is more clear to me.

Another question, based on this clarification, as per my understanding, there will be no need to apply this unbalanced wind load for the case of wind acting on the end wall (acting over the long dimension of the building). This unbalanced load would only be needed in case the wind is acting on the side wall (acting along the short dimension of the building).
Am I getting it correctly?