If when you import a repository created from a Revit model into RAM Structural System you may be getting gravity members that want to analyze as lateral. You can change the analysis properties in the Revit model so they export the way you want.
Steps to Accomplish
Select an element in the model that you want to set to lateral
In the properties panel, under the shape type left click the drop down and select the Analytical option
Scroll down in Properties dialog and make your Analytical properties selection
You can do this for individual elements or select a group of like elements and change them all at once.