Hanging a banner outdoors

[tristanpants]

I am hanging a 3x10 banner and attaching it to 2x10ft truss towers that is connected with a 10ft horizontal piece of truss. I am building this outdoors.

Question: How large should me truss bases be?
Question: How many sand bags?
Question: Does my sign have to absolutely have wind slits if there is a potential for high wind?

Regards.

 

[kicknargel]

You're going to need to do some math. Some research should turn up formulas for wind load.

You might consider printing on a mesh material that is designed for wind pass-through.

 

[derekleffew]

Just so we're clear, something like this?



Drawn as 20.5"x20.5" truss, but 12"x12" would work also. Most base plates are 4'x4'. What kind of wind load are we talking about? 20-30 mph?

 

[LavaASU]

***Assuming Derek's diagram is correct***

I typically try to avoid banners/sail like objects on that type of structure. It often takes less than it would seem like to tip those.

As far as your questions, I'd use the largest baseplate I could find. Sandbags and guys (most likely you will need guys) depend on what the max potential wind is. I typically use 15psf x safety margin** for wind load, but thats for the spandex and mesh we use, not solid banners. Google should help you here. As far as wind slits, no, as long as you build it to accommodate the wind load.

Assuming you are renting the truss to do this, talk to the riggers/lighting guys from the shop. They should be able to tell you how they would do it (also they know weather for your area). Sorry to be fairly non-specific, but without being a lot more involved in the project, thats about all I can say with certainty.

** safety margin depends on the risk of failure (obviously if this is over 20 people in an area prone to sudden wind gusts you would need a higher safety margin than if it were in the middle of an empty field)

 

[tristanpants]

Derek is correct in his cad drawing. I have 2ft steel 95lb bases and they can fit 5 sandbags on each. Thank you for your help. Where do you get the formula for 15psf x safety margin from? Is there an industry standard?

 

[LavaASU]

It's a minimum sometimes used for construction. http://tiedowneng.com/pdf/dstructural.pdf and Minnesota Department of Transportation Noise Analysis
If you do some google searching you can find studies with numbers based on different conditions. It can be as high as 30psf (and probably higher, but that's the highest I've seen). The 15psf + safety margin is also based on the fact that we always have a tech onsite and the *whatever* is coming down if it gets windy.

 

[derekleffew]

See this site: Wind Loads .

...Question: Does my sign have to absolutely have wind slits if there is a potential for high wind?

As kicknargel said, if "wind slits" are undesirable, consider having the banner printed on plasticized scrim. One Google-induced source: Mesh Banners | $3.2/SF Mesh Custom Banners, Outdoor Mesh Banners .

 

[MPowers]

I am hanging a 3x10 banner and attaching it to 2x10ft truss towers that is connected with a 10ft horizontal piece of truss. I am building this outdoors.
Question: How large should me truss bases be?
Question: How many sand bags?
Question: Does my sign have to absolutely have wind slits if there is a potential for high wind?

Here's an example of a 3'x17' banner, 16' high to the top of the banner, hanging the way you describe.
http://www.clelights.com/documents/roadrace.pdf
It doesn't show it but our base was a 10' stick of truss centered horizontally under each tower, perpendicular to the banner axis, making an outrigger. Each end of the "outrigger" had adjustable screw jack levelers. We had a 100# sandbag on each end of each outrigger, so 200# on each tower, 400# total. As you can see, no slits and a fair wind. I was on another job so I don't know the actual wind speed, but I hope this helps.

 

[bishopthomas]

Last year I was asked to provide structure for a 20x20 solid banner on a barge in the middle of a river. I passed on the job, something I don't often do.