Barrel Framed Roof Joists
Barrel Framed Roof Joists
(OP)
When barrel framing roof joists have you typically designed the joists for combined strong + weak axis bending or have you assumed that the sheathing and finish material forms a "deep beam" and therefore you don't need to check weak-axis?
In our case we have a curved roof framed ideally with 2x10 joists @ 24" oc. The max rotation of a joist in the roof is 15 degrees. If we break up the vertical force into strong and weak-axis we have strong-axis cos 15 = 0.97 ~ 1.0 (full load) and weak-axis sin (15) = 0.25.
Designing the 2x10 in weak-axis bending for the 25% of the load doesn't work, and would require 3x10 @ 16" oc. What do you all do?
In our case we have a curved roof framed ideally with 2x10 joists @ 24" oc. The max rotation of a joist in the roof is 15 degrees. If we break up the vertical force into strong and weak-axis we have strong-axis cos 15 = 0.97 ~ 1.0 (full load) and weak-axis sin (15) = 0.25.
Designing the 2x10 in weak-axis bending for the 25% of the load doesn't work, and would require 3x10 @ 16" oc. What do you all do?






RE: Barrel Framed Roof Joists
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.
RE: Barrel Framed Roof Joists
Any thoughts?
RE: Barrel Framed Roof Joists
Not my area of expertise I'm afraid. It's my wife's though. I'll query her tonight. I just get a bit nervous about relying on diaphragm action in sheathing that will be all bent and kerfed as will surely be the case. Probably just paranoia for small scale stuff though. What scale are we talking here?
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.
RE: Barrel Framed Roof Joists
RE: Barrel Framed Roof Joists
RE: Barrel Framed Roof Joists
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.
RE: Barrel Framed Roof Joists
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.
RE: Barrel Framed Roof Joists
Straps though, are they really necessary? The roof is the bottom half of a circle (more ellipse I guess). Therefore the weak-axis bending should always be putting the blocks in compression and not tension. Any accidental tension caused from wind loading seems like it may be able to be taken by the roof plywood nailing and blocking attachment (I'm not in high wind). If I were to put a strap on the top side, how effective would it really be as if it were in tension it would create uplift on the nails. Straps on the underside would likely get me a lot of flack.
RE: Barrel Framed Roof Joists
RE: Barrel Framed Roof Joists
Agreed. I can't speak for Eric but I was definitely thinking that your barrel was convex down. Didn't know you were building a giant sushi boat to catch rainwater. Crazy Californians. More GDP than sense.
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.
RE: Barrel Framed Roof Joists
We are in a drought...
Architect is looking at building slope for drainage at the bottom to come to the two sides. No snow loads obviously.
RE: Barrel Framed Roof Joists
RE: Barrel Framed Roof Joists
RE: Barrel Framed Roof Joists
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.
RE: Barrel Framed Roof Joists