Applies To
	Product(s):	STAAD.Pro
	Version(s):	All
	Environment:	N/A
	Area:	Concrete Design Solutions
	Subarea:	American Concrete Design
	Original Author:	Bentley Technical Support Group

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 6.6.4.3 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 6.6.4.6.2 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.