As part of the concrete column design output STAAD.Pro plots the Pn and Mn. Does Staad convert the Nominal Strength to Design Strength in order to check the column? Does it design for axial load plus biaxial bending ? How is the phi factor ascertained?
Yes it does convert the nominal strengths to design strengths and checks the factored column loads/moments against those values. It designs against combined axial load and biaxial bending. The Phi factor for column design is based on compression controlled section and on the type of transverse reinforcement being used.