The loading which yields maximum reinforcement is called the critical load. Column design is done for square, rectangular, and circular sections. By default, square and rectangular columns and designed with reinforcement distributed on each side equally for the sections under biaxial moments and with reinforcement distributed equally in two faces for sections under uniaxial moment. You may change the default arrangement of the reinforcement with the help of the parameter RFACE (see D8.E.3 Design Parameters). Depending upon the member lengths, section dimensions, and effective length coefficients specified, STAAD.Pro automatically determines the criterion (short or long) of the column design. All major criteria for selecting longitudinal and transverse reinforcement as stipulated by IS:456 have been taken care of in the column design of STAAD.Pro. Default clear spacing between main reinforcing bars is taken to be 25 mm while arrangement of longitudinal bars.

Default column design output (TRACK 0.0) contains the reinforcement provided by STAAD.Pro and the capacity of the section. With the option TRACK 1.0, the output contains intermediate results such as the design forces, effective length coefficients, additional moments etc. All design output is given in SI units. An example of a TRACK 2.0 output follows:

            C O L U M N   N O.      1  D E S I G N   R E S U L T S
  
         M20                    Fe415 (Main)               Fe250 (Sec.)
  
   LENGTH:  3000.0 mm   CROSS SECTION:  400.0 mm X  600.0 mm  COVER: 40.0 mm
  
   ** GUIDING LOAD CASE:    1 END JOINT:     1  SHORT COLUMN
   
   DESIGN FORCES (KNS-MET)
   -----------------------
   DESIGN AXIAL FORCE (Pu)             :    2000.00
  
                                            About Z            About Y
   INITIAL MOMENTS                     :     160.00             120.00
   MOMENTS DUE TO MINIMUM ECC.         :      52.00              40.00
  
   SLENDERNESS RATIOS                  :     -                  -
   MOMENTS DUE TO SLENDERNESS EFFECT   :     -                  -
   MOMENT REDUCTION FACTORS            :     -                  -
   ADDITION MOMENTS (Maz and May)      :     -                  -
  
   TOTAL DESIGN MOMENTS                :     160.00             120.00
  
   REQD. STEEL AREA   :     3587.44 Sq.mm.
   REQD. CONCRETE AREA:   236412.56 Sq.mm.
   MAIN REINFORCEMENT : Provide  32 - 12 dia. (1.51%,   3619.11 Sq.mm.)
                        (Equally distributed)
   TIE REINFORCEMENT  : Provide  8 mm dia. rectangular ties @ 190 mm c/c
  
   SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)
   ----------------------------------------------------------
   Puz :   3244.31   Muz1 :    269.59   Muy1 :    168.42
  
   INTERACTION RATIO: 0.98 (as per Cl. 39.6, IS456:2000)
  
   SECTION CAPACITY BASED ON REINFORCEMENT PROVIDED (KNS-MET)
   ----------------------------------------------------------
   WORST LOAD CASE:     1
   END JOINT:     1 Puz :   3253.88   Muz :    271.48   Muy :    170.09   IR: 0.96
   ============================================================================