RAM SS - Proper Moment Connection Modeling

Question

Hello, 
 
 I have a couple of moment connections that I need to model in RAM SS and I want to make sure that I am modeling correctly. 
 
 My first case is a continuous beam over the top of a column. I believe the correct way to model the beam is to use the "Assign Cantilever Beam" tool and put in an extension to the back span. Is there anything special I need to model with the columns? The beam runs over the top of one column and has a column bearing at the same point above. 
 My second case has the column being continuous with a beam on one side and a cantilever on the other. I have assigned the cantilever as a "stub" Do I need to turn the backspan into a frame member in order to get it to pick up the moment from the cantilever?

Thank you!

Seth Guthrie · Answer

1. Correct, a beam with a cantilever extension is normal. Such a beam is always fixed through the cantilever side support. If you want a fully fixed connection both beam and column should be lateral members with full fixity. For gravity framing, a fulcrum is assumed, no moment transferred to the column from a cantilever extension. A simple span beam and a stub cantilever can also be used. In this case the stub cantilever is fixed to the support and the back-span is assumed pinned. The back-span can still be fixed if it is a lateral beam. See also: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3038/ram-instability-in-finite-element-analysis-tn#cantilever 
 2. Yes, the back-span beam would need to be lateral in order to be fixed, but a beam with a cantilever extension is still allowed at lower levels following the same rules above.