D8.G.5 Column Design
Columns are designed for axial forces and biaxial moments per IS 456:2000. Columns are also designed for shear forces as per Clause 7.3.4. 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. However following clauses have been satisfied to incorporate provisions of IS 13920:
-
The minimum grade of concrete shall preferably be M20. (Clause 5.2)
-
Steel reinforcements of grade Fe415 or less only shall be used. (Clause 5.3)
-
The minimum dimension of column member shall not be less than 200 mm. For columns having unsupported length exceeding 4m, the shortest dimension of column shall not be less than 300 mm. (Clause 7.1.2)
-
The ratio of the shortest cross-sectional dimension to the perpendicular dimension shall preferably be not less than 0.4. (Clause 7.1.3)
-
The spacing of hoops shall not exceed half the least lateral dimension of the column, except where special confining reinforcement is provided. (Clause 7.3.3)
-
Special confining reinforcement shall be provided over a length lo from each joint face, towards mid span, and on either side of any section, where flexural yielding may occur. The length lo shall not be less than a) larger lateral dimension of the member at the section where yielding occurs, b) 1/6 of clear span of the member, and c) 450 mm. (Clause 7.4.1)
-
The spacing of hoops used as special confining reinforcement shall not exceed ΒΌ of minimum member dimension but need not be less than 75 mm nor more than 100 mm. (Clause 7.4.6)
-
The area of cross-section of hoops provided are checked against the provisions for minimum area of cross-section of the bar forming rectangular, circular or spiral hoops, to be used as special confining reinforcement. (Clause 7.4.7 and 7.4.8)
D8.G.5.1 Column Design Output
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 column design output (with option TRACK 1.0) is given below.
============================================================================
C O L U M N N O. 3 D E S I G N R E S U L T S
M20
Fe415 (Main)
Fe415 (Sec.)
LENGTH: 3000.0 mm CROSS SECTION:
350.0 mm X 400.0 mm COVER: 40.0 mm
** GUIDING LOAD CASE: 5 END JOINT:
2 SHORT COLUMN
DESIGN FORCES (KNS-MET)
-----------------------
DESIGN AXIAL FORCE (Pu)
: 226.7
About Z
About Y
INITIAL MOMENTS
: 0.64
146.28
MOMENTS DUE TO MINIMUM ECC.
: 4.53 4.53
SLENDERNESS RATIOS
: -
-
MOMENTS DUE TO SLENDERNESS EFFECT :
-
-
MOMENT REDUCTION FACTORS
: -
-
ADDITION MOMENTS (Maz and May)
: -
-
TOTAL DESIGN MOMENTS
: 4.53
146.28
** GUIDING LOAD CASE: 5
Along Z Along Y
DESIGN SHEAR FORCES
: 43.31
76.08
REQD. STEEL AREA : 3313.56 Sq.mm.
MAIN REINFORCEMENT : Provide 12 - 20 dia.
(2.69%, 3769.91 Sq.mm.)
(Equally distributed)
CONFINING REINFORCEMENT : Provide 10 mm dia.
rectangular ties @ 85 mm c/c
over a length 500.0 mm from each joint face towards
midspan as per Cl. 7.4.6 of IS-13920.
TIE REINFORCEMENT
: Provide 10 mm dia. rectangular ties @ 175 mm c/c
SECTION CAPACITY (KNS-MET)
--------------------------
Puz : 2261.52 Muz1 :
178.71 Muy1 : 150.75
INTERACTION RATIO: 1.00 (as per Cl. 39.6, IS456:2000)
============================================================================
********************END OF COLUMN DESIGN RESULTS********************