curved steel beams

huangyhg

curved steel beams
an architect client has literally thrown me a curve. a custom home i am designing the framing for has a circular great room (radius = 16'-0"), the walls of which support a stick framed roof above the great room and pre-engineered wood trusses from the remainder of the house. this is in colorado, snow load at this location is 30 psf. truss reactions range from 635 lbs to 1200 lbs. the stick framing allows for some fancy soffiting that could not be accomplished in the depth of the trusses. the circular area does not extend above the roof. as currently planned, the great room walls have to be supported by beams in the floor framing as the lower level (basement to those of us who can't afford a custom home) wall layout does not match the main level. i am trying to re-work the truss framing so that the curved wall is no longer loadbearing, except at discreet points under girder trusses, and make the drywall wizards create the circle effect. failing that, a curved beam becomes necessary. some questions:
1. how tight a radius can a beam be curved to? 16'-0" seems awfully tight to me.
2. what method is used to curve the beam and how does it affect the beam properties? seems to me that rolling to that tight a radius pre-stresses the beam alot. i wonder how they can do it with out buckling the flanges.
3. how often along the arc should there be supports? space them too far and the beam really starts wanting to crank around an axis.
4. this is too big to ship in one piece. should i require full pen welding at the joints? i can see some torsional deflection between supports but welding to produce a single piece i think would eliminate the need for a beefy column connection to handle torsion.
5. if not full pen welded will the beam relax or spread out over time?
6. any insights and comments are welcome.
engrman
rolling w shapes is common, but much is dependant on the type and capacity of the rolling equipment used, material spec., the size/depth of the beam and the required radius.
have inspected many a project with beams which have been rolled, some were very good, others were extremely poor in continuity. much is dependant on the company who rolls your material.
whenever we were unable to roll a w-shape, we fabricated it in 3 pieces.   we rolled the web, and the flanges were laser cut, and stitch welded on both sides of the web.
flores
try:
yes, your radius is over sized for one piece over the road shipping.  if the section is required fabricate the section in pieces and weld on site.   
for the curved wall plates, check a product called flex-c trac (405/302-0611;