My Question is: if we performed P-Delta analysis on Moment Resisting Frame, do we have to calculate the stability index to check whether it's a sway or non-sway frame? And in case of sway frames and we performed P-delta analysis, do we have to calculate K and check the box beside "Design as Sway Frame", and the last question why the program increases the reinforcement of the columns when designing as sway frame although the program is using the same moment coming out from P-Delta analysis?
Here's some advice on the matter of ACI and slenderness considerations for columns: https://communities.bentley.com/products/ram-staad/w/structural_analysis_and_design__wiki/27705/ram-concrete-column---aci-slenderness-design