wind dragging force calculation

[ramihabchi]

hi,
as I understand the french code nv65 there are two ways to calculate wind loads.calculating dragging load (or the global action),which consider the structure as a whole and calculating pressure per unit.my question is how do I know which one should I use?

 

[ThomasH]

I am not familiar with Frence code nv65 but I Googled it and it seems to be fairly old, publiced 1973.
I don't know exactly what you are doing but why don't you use the currenty code, which I assume would be the Eurocode?

If you use Eurocode I think it will be easier to help you.

Thomas

 

[ramihabchi]

Thomas I cannot use eurocode as I am already using PS92 for seismic loads and bael91 for design.if i use eurocode for wind i become obligated to use other parts of eurocode for rc design and seismic load determination.
Nv 65 has its latest revision in 2009.

 

[JStephen]

In the current US codes, wind design is specified for the structure as a whole (or large parts thereof) and also separate pressures for components and cladding used for design of local items only. It sounds like your code could be set up similarly.

 

[ThomasH]

I expected the Eurocode to be used in the countries that are EU members. I have actually found data for wind loads in France based on the Eurocode. But perhaps there are other options available, but I would check the status of the codes to avoid surprises.

Regarding JStepens comment, it is the same in most modern codes I have seen. You have a wind climate besed on a governing wind speed, terrain and height above the terrain. If the structures dynamic properties (generally frequency and mass) are unfavorable that must also be considered. And that can complicate the design significantly.
Then you have the basic design pressure and the wind effects on the structure can be described with shape factors for either the whole structure or components and cladding, large area vs small area.

In older codes I have seen simplified approaches. But sometimes there are crude methods that is difficult to understand.

Edit: I checked with a reference (EU site) regarding France and it is my impression that Eurocode 8 is the current code for seismic design. But there might be other optins available. ramihabchi, didn't you ask in another tread regarding Eurocode 8 and ASCE? A friendly advice is that you check so you are consistent in your choice of codes.

Thomas

 

[hardbutmild]

I'm not familiar with your code, but you mentioned there are two procedures, one that gives a global force and one that gives pressure on some area.
Now, I might be very wrong, I'll just tell you what i think. It seems to me that you could use that global force to check global stability of a structure (like overturning), or if you have a simple structure (like a one storey high frame) to determine sizes of columns or check connection of your frame with foundations. Also, to determine the number and position of stabilization trusses or walls.

Then use the pressure approach to maybe check edge rafters (english is not my native tongue, secondary elements laying on top of beams used to shorten the span of your roofing) since they might have local lifting problems or any details that require the knowledge of the exact position and distribution of that force. If you have a complex roof maybe to determine a force on a specific beam.

Basically, global action for global checks, pressure approach for some specific details.
But also check your code thoroughly to see if they wrote somewhere when a certain approach may or may not be used!