Wind Pressure Requirements

[RMRudnicki]

I'm hoping someone can help me here. I need to calculate what the wind pressure applied to a flush mounted 46.5" x 94.5" wall sign with a 3/4" edge would be. I am not looking just for an answer(although that would be appreciated), I would like the formula shown so that I will know how to do this in the future on my own. I need this for a village code ordinance that applies to a sign I am building for my small business. I'm not sure if this is needed, but I figure more information is always better...it's a small suburb that borders southwest Chicago & the sign will be on a one story building mounted with the bottom edge roughly 5' off the ground. The sign itself will be a sheet of .040 aluminum(roughly 20pnds) that will make up the front & edging with a 3/4" treated plywood backing(roughly 75pnds) for a total sign weight of 100pnds(with hardware). The sign will be mounted using 3/4” x 5 1/2” Tapcon screws with a tension rating of 13048pnds & shear rating of 17908pnds (I was planning on 6 each on the top & bottom & 4 each on the sides). I have tried searching for this formula & have not come up with anything that shows me what variables I need in order to make this calculation, if anyone here could give me a hand I would greatly appreciate it.

Thanks,
Robert

 

[Qrs]

It depends what building code is adopted in the area. Most likely you will need to look at ASCE 07 (though which version will vary...maybe 05 or 10) which can be found here:

http://www.asce.org/sei/Content.aspx?id=23622324319

Unfortunately, the wind pressure is not simply an equation, but an equation with several coefficients/variables that depend on the specific site conditions.

 

[vmirat]

Most, if not all, building departments use the IBC as their code. The IBC then references ASCE 7 for specific formulas such as wind loading.

The wind pressure is a function of wind speed, height above ground, surrounding terrain, and whether it's the main wind force resisting system or components and cladding. The wind speed is usually dictated by the local building department. The rest of the information is based on coefficients found in ASCE 7. The short answer is that there is no simple response to your question.

On a side note, it sounds like you're not a structural engineer. It's one thing to know how to work mathematical equations. It's a completely different matter to know how and why you are using these equations. If you're having to comply with a local code, then they will most likely want calculations stamped by a registered professional engineer or architect.

It will be interesting to see how other engineers on this forum answer your post. I think most will tell you that we make a living answering questions such as this, so go get yourself a structural engineer. I guess I'm telling you the same thing, in the nicest way possible.

 

[RMRudnicki]

Thank you.

 

[ztengguy]

I would spend 200 bucks and hire a local engineer. he will do a quick calc, stamp a letter. that way, if god for bid a windstorm rips it off and it decapitates some one, you can point them (or family) to the engineer.

 

[XR250]

Nice Ztengguy!

BTW, where are you finding those Tapcon capacities? Seem a bit high...

 

[Ron]

ztengguy....too cheap. That service should be in the $600 range. Don't give away engineering services! They (clients) will always expect lowball prices if you ever start it.