I have a Ram Elements file wherein I am modeling a PEMB to obtain preliminary reactions. The building consists of 4 distinct buildings with a low flat roof and three higher roofs with monoslope roofs. I have the bracing and portal frames modeled to deal with the lateral load but am receiving instability errors when running the P-delta analysis that prevents the model from running; all seemingly related to RY at nodes where the horizontal X-braces meet at the monoslope roofs. Any idea on why this instability is arising? Could there be excessive racking in the frames that would be causing this? Any help appreciated. Thank you,
It's hard to tell from the picture. It it runs without P-Delta but not with P-Delta and you have tension-only braces, then you could proceed without using P-Delta or you could switch to tension and compression braces for example. For more see: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/18931/ram-elements---tension-only-members
and https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3038/ram-instability-in-finite-element-analysis-tn