My question concerns the Drift Control Module and the loads used for this analysis.
With the understanding that this Module follows Castigliano's Theorem, under what circumstances would it make sense to create a Virtual Work load case with a non-zero force at more than one level?
If trying to use the Drift Control Module to evaluate a structure's behavior for drift at each level (in the same direction) of a multi-story building, shouldn't a Virtual Work load case be created for each level where only the level of interest has a non-zero magnitude? And in turn, each of these Virtual Work load cases would have a separate load pair with the real load case of interest?
On a similar note, when or why would a factor other than 1 be used for a load pair?
Appreciate any insight.
I have only used virtual load cases with lateral force on a single diaphragm. The program allows you to enter other loads, but I've never had a good reason to do so.
I ran a simple test here and I don't think the scale for the load pair actually does anything. I get the same results in my test using 1 or 20.
I think it was originally implemented so that users could linearly scale up the various participation values you see in the member view/update dialog in case the reported values were too small to offer enough significant digits. I'll try to get confirmation on that point.
The virtual work analysis in Ram Frame is one of those features that I think can be very useful, but most engineers don't use it because it's not a code requirement. I would love to hear more about your building and any other feedback you have about it's usefulness in optimizing the structure.