curved wood beam

huangyhg

curved wood beam
does anyone have any experience with designing a laterally curved wood beam? i have a client who wants a 35' long beam with a 22' radius that will be supported on the ends and at the center. i am trying to figure out the best way to construct the beam, whether it be built up from dimensional lumber or if it could be built up from some type of engineered product. it's going to be outdoors and therefore exposed to the weather so i have to take that into consideration as well. any input would be appreciated. thanks.

what kind of loading will it take?  it is going to be expensive and it will probably be glue lam that is made to curve vertically.  you are introducing torsion thats why i want to know if the loading.
never, but never question engineer's judgement
no experience with that, but i think i would start out by talking to my friendly neighborhood glulam fabricator.
ba
just use a steel tube section and wrap it with wood veneer.
tell the architect that the tube section is a recycled a wood beam that was made to look like steel for use by another architect.  he won't know the difference.
mike mccann
mmc engineering
mike,
you need another beer.
ba
the loading will be pretty minimal, it's the main beam for a outdoor pergola. i would say it won't see anything more than 250 pounds per foot at the most. i think i might try to push the architect towards using something other than wood, seems like that might be the best way to go.   
mwhite1206,
who said anything about an outdoor pergola?  what the hell is a pergola, anyway?  you are guessing.  you need another beer. if you and mike want to get together for a beer, let me know...i'll be there!
ba
they sell curved glulam that can be outside.  
check this out
give the glulam manufacturer a six pack.  he'll make it real curved.
mike mccann
mmc engineering
no problem, the torsion is limited to the 70 degree arc between supports and the center suport will get loads from both arcs.  rectangular wood sections have good torsional properties, (as do rectangular steel hss).  vertical laminations bent around a jig or form and then glued will hold the desired radius.  a good polyurethane finish would be recommended as well as waterproof glue or epoxy.
before you give this client a laminated beam for a pergola, you need to find out what he wants it to look like, and for how long.  if he wants a clear finish on the beam like you would see in a church roof, the finish won't last long in the sunshine, no matter what newfangled coating is used.  maintenance will be required often, say every 12 months if lucky.  if he is going to use an opaque finish, then he might as well use a steel tube.