huangyhg

glued plywood to use as rafter
so i have this curved roof and it looks like the easiest to frame this is to use (2) 3/4" plywood nailed and glued together to create curved rafters. i only need probably 4-5 rafter at this particular location of the roof. what value can i use? is it conservative to say it is d-f 2x12 #2 (i tell them to cut it 11.25", so it will have the same area as 2x12 so i can use the same hanger).

plywood design specification, supplement #5, "design & fabrication of all-plywood beams". free apa download, after registering:
not big enough project to consider glulams?
it is curved almost like 1/4 circle. can you order curved glulams? but i think it is still cheaper to just use plywood. thanks for the link slideruleera!
not sure how the cut is going to come out of the plywood, but only veneers running parallel should be counted on, so around 50% of section? maybe less. also, i am guessing less than 8 foot long rafter?
you can get cambered glulams. check for axial stress due to the curvature, i would also consider glulams instead.
its only spanning 5 ft. i will probably be using the same plywood as the floor. what do you mean veneers running parallel? how much can you camber the glulams? can you camber it almost like 1/4 of a circle? (5ft radius).
5 ft may be a little too short for cambering a glulam. i had a larger span in mind.
yes, gluelams are curvable....much more than small cambers. call your local rep, they can get some pretty tight radiuses. also, look at
the nds provides design stress values for sheathing in it's supplements. i would check there also.
the veneers in plywood are turned 90 degerees for each laminiation. i think the two exterior laminations run parallel with the 8' dimension. a veneer by itself can literally be torn apart by hand perpendicular to grain. i think the glue between the veneers helps some, but i wouldn't count on it to be able to take any tenion (bending). so the section to design for would roughly be 50% of the gross section due to the alternating orientation of the veneers.

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