All,
What are the best practices for modeling (RAM SS) a floor in a multi story building that has a large opening against the exterior wall (such as an atrium)? We have modeled it so that the slab edge is the perimeter of the building. Then put in the large opening ringed by beams. The diaphragm is rigid. Since there is a small sliver of slab on the exterior beams (with a rigid diaphragm), it does not transfer any wind loads to these beams and therefore they *and the columns they are attached to) are not properly designed. It also means the load paths for this area are not 100% correct. We are looking at designing them in a component software (spreadsheet).
Any thoughts or recommendations for this?
Thanks,
Mike
We typically use a semi rigid diaprhagm, with lateral columns and gravity beams - essentially the diaphragm there acts like a wind girt and load the column mid-span to the adjacent diaphragms above/below.
We have a glass curtainwall enclosed atrium that starts at the Second Floor and goes past the Third Floor and the Attic Floor up to the Roof Level. The screenshot shows some intermediate framing that only occurs at the Third Floor. The floor is a composite deck (rigid diaphragm). Could I include the HSS beams at the curtainwall perimeter in a separate semi-rigid diaphragm and properly capture the wind loads with my HSS-W16 moment frame H9-J9 in both directions?
Should I change anything else at this level (3rd Flr)? I hope you can click on the screenshot to see it full-size.
Is it even possible to enclose just the HSS curtainwall beams in a semi-rigid diaphragm adjacent to the rigid diaphragm at the Third Floor?
You could model an outer slab edge with an opening, but you would have to make the entire diaphragm semi-rigid in this case.