Answer Verified By: Abubeker Ali
I am having a similar error using version 15.04.00.000. When attempting to run concrete gravity analysis, the following error is noted: "Invalid Distance of 0.0000 between Nodes 3262 and 3262 is found for Shell Element Wall 228 at Story Roof and Floor Roof. This distance is smaller than the accepted tolerance (0.0000)." I will upload my model and reference this thread, thanks!
I can't really support v 15.04 any longer, but the wiki noted above still applies. Make sure the walls align, and column with walls (when that's the intent). Avoid overly complicated deck layouts (a single 2-way deck is simpler than a bunch of one way decks).