Flat Roof Canopy Design with Tension Rod Supports 1

[kshook1824]

I am getting ready to, but have never designed one before, a tension rod supported canopy and am looking for some insight on the correct path for design. Any help would be greatly appreciated.
What design checks need to be done?
Typical Connection Details?
Size and Spacing of Rods?
Are pipes better than rods? (Wind Uplift Issues...)

Thanks!

 

[KootK]

- rods are better for uplift. Architects sometimes object however in those cases, I've used light duty moment connections at the low wall connection and just let the rods buckle out of the way.

- depending on your code and geometry, you may need to deal with snow blown onto the canopy from the adjacent roof.

- I usually make the low rod connection a gusset plate that's tall enough to get the connection safely above the roof assembly to make roofing the penetration as easy as possible.

- there's often a gutter that your framing needs to dance around.

- if aesthetics are important, I'll sometimes use a post installed connection at the top. Cast in plates have tolerances and they can be mislocated or rotated in ways that catch the eye.

- use materials suitable for outdoor exposure do that you don't get rust bleed all over. This can often be a issue at the cast-in plates.

- if possible, I'll provide field adjustability in the rods. One way is turnbuckles but those can be visually obtrusive. I've often used a detail where a bent plate is welded to the upper connection plate. A threaded rod passes through one of the legs of the bent plate and a pair of nuts. It's pretty clean.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[jayrod12]

I've done the threaded rod many times as Koot has described in his last sentence. For the architect's that don't like the looks of turnbuckles it is generally a reasonable middle ground with them.

 

[hokie66]

The uplift has to be designed for. If there is a lot of uplift, as in cyclonic areas, rods don't help much. The choices are usually either struts in the form of hollow sections, or else sufficient ballast to resist the uplift. The appropriate solution depends on a lot of things, including the type structure which supports the awning, and I can't tell that from your sketch.

 

[Ron]

Agree with hokie66....uplift has to be checked and rods are not good for uplift....they buckle

I've designed many of these and have used both square tube and pipe sections for the strut. Either can be designed for the uplift buckling mode. Pay attention to the strut connections.

 

[Once20036]

As a matter of detailing - be mindful of dissimilar materials.
You don't want an aluminum canopy bolting to a carbon plate due to galvanic corrosion. Pick a material & stick with it - or provide details on how to prevent the different materials from contacting.