Standing Seam Metal Roof Canopy

[DaveAtkins]

I am currently designing a standing seam metal roof canopy. Yes, I did provide a wide rib steel roof deck below the standing seam roof, so no diaphragm issues. The support framing is structural steel (curved beams), on steel tube columns, on concrete piers and footings. It is a stand alone canopy at an amusement park.

My client (local public works engineer) is wondering if the summer heat will cause the steel roof deck (not the standing seam metal roof--it is able to slide on its support clips) to expand, resulting in failure of the deck welds. I am currently just showing standing seam directly on steel deck--perhaps I should provide rigid insulation, to prevent the hot standing seam roof from transferring heat to the steel deck? Seems strange, because this is an unheated structure.

DaveAtkins

 

[Ron]

DaveAtkins...yes, provide the insulation and a "slip sheet" between to allow for differential movement.

 

[XR250]

How big is the structure?

 

[MotorCity]

While I think adding insulation is cheap insurance, my gut tells me expansion of the deck would not be an issue. If you ran the numbers and calculated the actual linear expansion and the resulting stress on the welds, I would expect the effects to be very minimal.

If you were to get significant expansion due to changes in the ambient air temperature, wouldn't you also have to add insulation to the bottom of the deck since it would be exposed to the ambient air? (I assume the discussed above was to only add insulation between the deck and standing seam roof)

I have used exposed roof deck in warm climates and have not heard of this being a problem (typically used in industrial applications for shielding, canopy, or storage structures)

 

[BUGGAR]

Can the continuous spaces between the wide-ribs and below the standing seam panels provide vent spaces to remove the heated air?

 

[DaveAtkins]

The canopy is 19' wide by 28' long. So maybe this isn't a big deal after all.

DaveAtkins

 

[KootK]

Another alternative might be to use Hilti pins instead of deck welds. The pins have some give and would not fail in a brittle manner as the welds might. I'm not sure if there are issues with using pins in an exterior application.

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.

 

[XR250]

…..or even self drilling screws if the flanges are not too thick