The following information would explain how ACI implementation in Staad currently handles the Stability design of a member.
User need to provide the information if the column is braced against side sway or not braced against side sway.
To define the effective length factor along both the orthogonal axes, one has to specify by SKY and SKZ.
Use the equation no. 6.2.5 or 184.108.40.206 to determine if the column member is to be categorized SWAY or NON-SWAY.
For analyzing as NON SWAY, code first suggests comparing Q (stability index ) with 0.05. One has to determine the Q value and enter the same in Staad by SQY and SQZ parameter.
Now, ACI code specifies the different rules for the frame checking both against the drift (Member Ends) and the
member internal curvature (Member length) . So, fundamentally, by these check code is capturing both the P-Large Delta and P-Small Delta effect.
The Moment magnifier as mentioned in the equation 220.127.116.11.2 needs to be defined by the parameter MMAG
In case of member internal curvature due to the intermediate loading, TRN parameter needs to be defined.