I've read the portion of the RAM Frame manual that talks about how lateral loads are distributed for the different diaphragm types, however, I'm currently analyzing a model for which I can't make sense of the way the RAM-calculated wind loads are being distributed.
The building is a 7-story structure. When I initially ran the model with all diaphragms as semi-rigid. My understanding is this does an analysis that, in the end, is a "hybrid" between distributing lateral loads based on tributary and wall stiffness, dependent on the rigidity of the diaphragm. I didn't like the results I was getting as semi-rigid, so I changed all diaphragms to rigid. It is my understanding that now, all loads should be distributed based on stiffness.
See the screenshot below. I have two identical walls pictured with the exception of an opening in the bottom level of one wall. The one on the left takes ~15k while the one on the right, with an opening, takes ~37k. I can't think of a reason that the one with the opening would be taking more load than the one without, and by a significant margin.
Thanks in advance.
If you have not seen these posts I often refer to them.
https://communities.bentley.com/products/structural/structural_analysis___design/w/structural_analysis_and_design__wiki/8430.ram-frame-building-and-frame-story-shear
communities.bentley.com/.../8174.aspx
It's impossible to say from a picture exactly what's happening, but here are a few considerations.
If there is torsion, or rotation, in addition to lateral force, then seemingly identical walls can take significantly different forces. If those walls in your picture are not parallel, that.s a similar issue. Check the nodal displacements and confirm that the displacements are in line wit the shear and overturning moments you see.