Using the Criteria - General command, the user can declare whether the P-Delta effect should be considered or ignored. To consider P-Delta, the Yes option button is selected. This instructs the program to perform secondary moment calculations as prescribed by code.

Two options are provided for P-Delta effects to be considered in analysis:

• Use Mass Loads – this option uses building mass to calculate P-Delta effects. It is briefly mass associated with diaphragms. Note that this is the default method used in the program.
• Use Gravity Loads – instead of using building mass, this option uses applied dead and live loads to calculate P-Delta effects. Note that different scale factors can be defined for dead and live load components.

In either case, the program applies the same method to calculate P-Delta effects. The only difference is that the former uses building mass converted to building weights to be used in P-Delta calculations and the latter uses dead and live loads instead for P-Delta effects.

It should be also noted that P-Delta effects are not only considered for rigid diaphragms but they are also included for analysis with semirigid diaphragms.

Making changes to the P-Delta Effects criteria after a model has been analyzed necessitates a re-analysis of the structure.