I've set the scale factor for each orthogonal direction (I=1.5 either way, but different R based on deformability from ASCE 7-5 Ch 13). I've entered a site-specific response spectrum (handy little spreadsheet on the wiki link above - thanks!). I have landings with 3" up to 7 1/2" of concrete, so a rigid diaphragm would be a valid assumption. some of the landings are freestanding on columns, others are suspended from hangers, and some are column supported at one corner and anchored to concrete walls at 1 or 2 of the other corners. I had simply modeled wall anchorages as a pinned reaction on previous gravity-only designs, but if I try to model a rigid floor diaphragm with 1 node pinned, I get an error. Is there a way around that with the lumped masses or would I need to apply my mass as nodal masses at each node at that level? And if I do that, would the program be double-counting? I have self-weight enabled, and was a little unclear on that point from the wiki. Thank you much.
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