Curved Roof Deck
Curved Roof Deck
(OP)
I have a curved roof (62 foot radius) constructed of bowstring LH trusses and metal roof deck.
I'd like to use 18 gage deck but I have no idea if it's possible to curve it (the easy way) at a radius like this.
On a related note, the Architect wanted to use straight joists framed the opposite direction and roll the roof deck the hard way. I told him no because I was worried about diaphragm capacities. Has anyone seen any design guidance for using curved roof decking? Also, what is your favorite method of getting a curved roof?
I'd like to use 18 gage deck but I have no idea if it's possible to curve it (the easy way) at a radius like this.
On a related note, the Architect wanted to use straight joists framed the opposite direction and roll the roof deck the hard way. I told him no because I was worried about diaphragm capacities. Has anyone seen any design guidance for using curved roof decking? Also, what is your favorite method of getting a curved roof?






RE: Curved Roof Deck
RE: Curved Roof Deck
RE: Curved Roof Deck
Dik
RE: Curved Roof Deck
One thing you can do if you have a lot of time, is calculate the distance of bend that the deck sheet metal is put under. The length of the effective bend is perhaps the 6" rib spacing. Essentially you would construct a pseudo beam (say a 12" wide piece of deck, 6" long) that would bend some distance.
Then determine the moment of inertia of the sheet metal (very small) and calculate the flexural stress in the sheet metal as it is bent. You'll most likely have a very small stress.
RE: Curved Roof Deck
I don't think there should be any problem getting the curvature the "easy way" but if it is 3" or deeper deck, it might be a little tough getting it the "hard way".
BA
RE: Curved Roof Deck
I just have no concept as to how thick 18 gage material is and how hard the contractor is going to have to work to lay it down on a curve.
Thanks for the info.
RE: Curved Roof Deck
BA
RE: Curved Roof Deck
I agree. I'd love to use 20 gage deck which is the minimum allowed by the unified facilities criteria, but the Air National Guard has a technical memo stating that all roof structures must meet Factory Mutual approval criteria, which also, incidentally, rules out 3" deck.
RE: Curved Roof Deck
Dik
RE: Curved Roof Deck
RE: Curved Roof Deck
So if you were to magically "fix" the edge of a deck and let it bend about its weak direction with a cantilever = 7'-6" ft, the bend that results under its own self weight alone is huge - the deck is essentially a wet noodle.
RE: Curved Roof Deck
I actually have 6'-0" truss spacing, except for the last bay. The front of the building curves creating a longer end bay. There's no practical way to decrease the end bay length because of the curve. The Architects put all these curves on a building and then are bewildered when the construction estimate is over budget.
I'd actually planned on using 3" deck before finding out that there aren't really any Factory Mutual approved 3" decks.