Steel Compression Ring Beam (roof) 1

[Mat_W]

Hi,

Long time reader first time poster.

Does anyone know of a design guide for a compression ring design (steel?

Thanks in advance.

 

[JStephen]

Roark's Formulas for Stress and Strain includes a load case with N radial loads applied to a circular ring that may help.
I believe he also includes elastic buckling of a circular ring under uniform radial load, although I doubt that would control.

 

[WARose]

I went through something like this some years back (a lifted ring):

https://www.eng-tips.com/viewthread.cfm?qid=325168

 

[dhengr]

Mat_W:
Note that there must be a tension ring at the bearing elev. of all of the rafters. And, the two rafters opposite each other, and the compression ring and the rafter/ring connections at the compression ring, in effect must act like a bunch of three member (2 inclined legs + the ring) rigid frames at 15° (or whatever) intervals around the circle. The moment connections of the rafters to the comp. ring are the tough part, so the comp. ring, in its horiz. plane doesn’t become unstable. Sometimes, because the connection detailing up at the comp. ring gets too tight/complex, only ever other or every third rafter runs full length (tension ring to comp. ring) and the others are headered off half way up the roof plane. The header runs btwn. the full length rafters to pick up the lower/shorter rafters. The full length rafters become larger members, but are likely easier to make work up at the comp. ring. This sometimes cleans up the sub-framing rafters and roof sheathing or layup of roof decking with std. lengths. Unbalanced (one sided) loading, wind or snow, are important design considerations. The walls below the rafter bearing elev. must offer some shear and/or torsional/twisting resistant, otherwise these roofs can be unstable. The roof system above the tension ring can rotate and cause the wall studs (window jambs) to rack and the whole thing just cork screws down to the ground. Another alternative is to run 4 main rafters (ridge beams at 90°) to the peak, where they can be connected together with a much smaller compression ring connection.