How much tension is in a sail roof?
How much tension is in a sail roof?
(OP)
Hello,
A building I am working on has a small sail awning. Does anyone know roughly how much tension these carry? I have seen a few bust loose.
Thanks,
Tom
A building I am working on has a small sail awning. Does anyone know roughly how much tension these carry? I have seen a few bust loose.
Thanks,
Tom






RE: How much tension is in a sail roof?
Roark's Formulas for Stress & Strain gives the following equation:
P = (w*L^2) / (8*y)
w: unit load along element (in your case consisting of self-weight and some allowance for wind pressure)
L: unstretched length
y: maximum displacement
y = L*[(3*w*L)/(64*E*A)]^(1/3)
RE: How much tension is in a sail roof?
How much tension it will have to take will be determined by local weather conditions.
Limit States are probably:
Water + Self Weight
Wind + Self Weight (If it's angled so the downwards force of the wind will be worse)
Wind - Self Weight (If it's angled so the upwards force of the wind will be worse)
The wind and water values will depend on the area and location of the canopy.
Usually these things don't tear in the middle they break free at the supports so that should probably be your area of focus.
RE: How much tension is in a sail roof?
Cheers
Greg Locock
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.
RE: How much tension is in a sail roof?
RE: How much tension is in a sail roof?
Complex structures can be highly non-linear in behaviour. The stress changes as the fabric stretches under load. In a simple-span structure, this is conservative; you calculate your tension by w-l>2/8*y as shown above, then calculate the sretch in the fabric, then you have a new "y" based on the fabric stretch, then repeat until the change is satisfactorally small. If the structure has two or more panels arranged in such a way that the two panels of the membrane can affect each other, this stretch can end up making the "simple" analysis unconservative.