Evaluating wind pressure Uplift - Entertainment Stage structure

[SilverBeam75]

Hi,

I've to design an outdoor (temporary) stage structure. The dimensions are: 70' x 53' x 45' high. The roof is covered with a dense fabric (kevlar type) and the rest of the structure we use a mesh type shade.

I know that if I have fabric around 3 faces and my downstage is left open the wind will penetrate the stage and the uplift will be very important. But I'm unable to interprete the ASCE-7 wind calculation for this kind of structure.

Anyone has an idea ?

any help would be appreciated,

thank you,

 

[vandede427]

try using the provisions for signs. essentially you've got a sailboat.

 

[BAretired]

I would think the uplift would be similar to an internal pressure. The NBC suggests an internal pressure coefficient of +/-0.7 for Category 3 buildings (those with large or significant openings through which gusts are transmitted to the interior). The gust factor is 2.0 for this type of building.

I am not familiar with the ASCE-7 document.

BA

 

[Bagman2524]

Take a look at ASCE-7-05 section 6.5.11.4 which covers roof overhangs.

 

[SilverBeam75]

Thanks all for the help.

Do you think I can reduce the internal pressure on the assumption that I have a mesh type fabric on 3 faces that will let the air flow through? Because the internal pressure is giving me an uplift of 25 psf on the roof (its very important)

Any suggestion ?

thank you all for helping,

 

[BAretired]

Yes, you could reduce it. How much depends on the opening size of the mesh.

BA

 

[Bagman2524]

I would suggest reducing it by the proportion of the total area of the holes to the total area of the side.

 

[BAretired]

I would not reduce it quite that much Bagman. Commentary I of NBC 2005 User's Guide has some information on force coefficients for various shapes and for shapes with openings (such as trusses).

BA