Modeling Concrete Domes and Ring Beams in RISA3D
Modeling Concrete Domes and Ring Beams in RISA3D
(OP)
Does anyone have any experience modeling concrete domes with ring beams in RISA3D? I'm having a hard time getting the tension force in the ring beam to match the theoretical force based on shell theory. The meridinal forces are reasonably close (within 0.5%) of the theoretical, but my tension forces are way off. I'm pretty sure it has something with the way I'm restraining the roof. Basically, I modeled the circular roof with a concrete member around the outside. I restrained each node of the concrete beam in the vertical direction. I also restrained one node in the global x and z directions and another node I restrained just the z direction, which is tangential at that node. This allows the ring beam to stretch but not twist; but it is restrained against "stretching" at the pinned node. See the attached plan view of my model for clarity. Note that because it is plan view, the vertical restraints are not shown.






RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
I would model it with the x and z reactions at the peak of the dome only and just vertical reactions at the ring.
RE: Modeling Concrete Domes and Ring Beams in RISA3D
I might try a single global support restraining all translation and rotation about the vertical axis.
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: Modeling Concrete Domes and Ring Beams in RISA3D
If so, then you might check out the Modeling Tips section of the help file / General Reference an look for a sub-topic called "Modeling inclined supports". In that topic you create a short rigid link member in the direction desired (in your case perpendicular to the circle). One side of the link is connected to a rigid support. The other side is connected to the ring beam and you use the end release for the rigid line to restrain the structure in whichever local direction it needs to be restrained. Make sense?
RE: Modeling Concrete Domes and Ring Beams in RISA3D
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: Modeling Concrete Domes and Ring Beams in RISA3D
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: Modeling Concrete Domes and Ring Beams in RISA3D
Thanks again.
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
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: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
RE: Modeling Concrete Domes and Ring Beams in RISA3D
I recently read an account of how the Orange Peel hypothesis of cracked domes allows the St. Peter's dome to remain viable post spread (pic below). It's fascinating. To some degree, this redistribution of load will take place even in a reinforced dome as it transitions to the cracked state. I'm not suggesting that you should design your dome this way. This is just fun shop talk. You can take some comfort from knowing that this two way arch behaviour is available as a last resort however.
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: Modeling Concrete Domes and Ring Beams in RISA3D
Thanks again for the help!