I originally modeled my building with flat steel since I was not sure how we would slope the steel for roof drainage. We have determined the slope so I went back into the modeler and adjusted top of columns and story heights to match my building. When I reran my building, the forces were drastically different and when I look at the displacements too my roof decking is displacing freely vertically. It seems like the roof decking is no longer acting as a unit with major displacement in the center of the bays. What did I do wrong? I removed the decking prior to sloping the steel and then reapplied so my 3D model looks correct.
Thanks,
Chris