Hi, Bentley,
1.) Is it allowed to incorporate Dynamic Seismic Load Cases to a Repeat Load combination? If not, Why?
2.) How about Static Seismic Load Cases, is it recommended to be incorporated to a Repeat Load combination?
You cannot include a dynamic load case in a REPEAT LOAD combination. You need to use LOAD COMBINATION for that. A REPEAT LOAD requires all the component loads to be applied on the structure for the analysis and that is where the challenge lies when it comes to dynamic loads as it is not constant but varies with time.
You can use static seismic cases in REPEAT LOADs. Just make sure that each static seismic load case is followed by a PERFORM ANALYSIS and a CHANGE command. Now whether to use REPEAT LOADs or LOAD COMBINATIONs would depend on what kind of analysis you are doing. More details on this are available at
https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/3441/member-tension-and-combination-load-cases-tn