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Design of Concrete Long Column as per IS:456-2000 code requires to satisfy the Notes 1, 2 and 3 of Clause 39.7.1 of this code. To take care of the terms “Braced” and “Unbraced”, as described in these notes, STAAD.Pro has a design parameter associated with this code as “BRACING”.
The available options of this BRACING parameter are –
0: The column is braced about both axis (Default).
1: The column is unbraced about major axis, but braced about minor axis.
2: The column is unbraced about minor axis, but braced about major axis.
3: The column is unbraced about both axis.
As per Note 2 of Clause 39.7.1, the additional moment (as calculated by Cl 39.7.1) is added to an initial moment equal to sum of 0.4 Mu1, and 0.6 Mu2, where Mu2 is the larger end moment from analysis and Mu1 is the smaller end moment from analysis (assumed negative if the column is bent in double curvature). In no case shall the initial moment be less than 0.4 Mu2 nor the total moment including the initial moment be less than Mu2. For unbraced columns, the additional moment shall be added to the end moments.
BRACING 0: Initial moments are calculated and added to the Additional moments about both axis.
BRACING 1: Initial moment is calculated about minor axis and is added to the Additional moment about minor axis.
BRACING 2: Initial moment is calculated about major axis and is added to the Additional moment about major axis.
BRACING 3: No Initial moments are calculated.
If the BRACING parameter is not assigned (default value as 0), the program will consider that the column is braced about both the axes.