Wind load parameters. 1

[ramihabchi]

hi,
In the french code for wind.masking effect could reduce or increase wind pressure.there is no formulation to get this coeficient in case of turbulant wake(or in french "sillage turbulant") as it said that it is complicated and it need an experiment.my question is how to know if this effect happens or not in case of my structure, to avoid doing experiment and being cappable of neglecting this effect.

 

[ilyas415]

Hi Ramihabchi,

Just to be clear, are you talking about wake buffeting / wake interference? (for example, when the winds on the building being designed are affected by a building at some distance "behind" it?).

Or do you mean vortex shedding?

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Ilyas

 

[ThomasH]

ramihabchi

Whrn you mention the french code, I assume that you mean the Eurocode? Or is it the french annex, or something else?
The term "masking" is not in the Eurocode but what chapter is it?

Thomas

 

[ramihabchi]

Hi sorry i wasnt clear,it is mentioned in NV65 chapter 3 1.243.yes i think it can be called wake interference/wake buffeting.

 

[ilyas415]

To be honest, I don't know anything about NV65.

I can suggest taking the Eurocode approach... which is defined in Annex A, Section A.4 of Eurocode EN 1991-1-4:2005.

It involves taking the pressure acting at the top of your building / structure to be equal to the pressure at a slightly higher height above ground. This introduces a bit of conservatism in your design since wind pressure increases with height.

If you expect your structure to be dynamically sensitive (e.g. fundamental frequency of vibration below 1 Hz, or greater than 200 m in height), then this approach might NOT be valid... and you will need to do as the building guide asks and undertake wind tunnel testing.

Please let me know if you have further questions.

Kind Regards,
Ilyas

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Ilyas

 

[ilyas415]

I had another look at the Eurocode criteria for Wake Buffeting.

I have included it in the image below:

EN 1991-1-4:2005

Ilyas

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Ilyas