V. IS456 2000-Circular Column
Verify the designed results produced by the program with hand calculated design results for an axially loaded circular column section as per IS456:2000.
References
Bureau of Indian Standards. SP 16 - Design aids for reinforced concrete to IS: 456-1978. 1980. New Dehli: Indian Standards Institution. p. 141.
Details
The fixed-base, 2.5 m cantilever column is subjected to axial force of 800 kN and a moment at the top of 162.5 kN·m. The section is 500 mm in diameter. The concrete strength is 20 N/mm2 and the yield strength of steel is 415 N/mm2. Use a clear cover of 50 mm. The main reinforcement is 20 mm and the lateral ties are 10 mm.
Validation
Slenderness Ratio
From Table. 28 Clause E-3 of IS 456 : 2000, the effective length of the compression member:
Least lateral dimension of column = (5,000/500) = 10 < 12
Large lateral dimension of column = (5,000/500) = 10 < 12
So, we can consider and design as a short column.
Check for Minimum Eccentricity of Column
As per Clause 25.4 of IS 456 : 2000, calculate the minimum eccentricity:
For Width emin = (2,500/500) + (500/30) = 21.7 mm > 20 mm. (OK)
Hence Minimum Eccentricity is ok.
Check for Maximum Eccentricity of Column
As per Clause 39.3 of IS 456 : 2000 calculate the maximum eccentricity:
For Width emax = 0.05 × 500 = 25 mm. Hence, emin < emax (OK)
Hence Maximum Eccentricity is ok.
Design for Flexure
Determine the non-dimenstional parameters to use with interaction chart 56 of SP 16:
From the chart, , and thus
The area of longitudinal reinforcement required then is given by:
Let assume 20 mm dia bar. So, Ast = (3.14/4) × 252 = 314 mm2 .
Number of bars = (2,355/314) = 7.5 ≈ 8 bars
So, the actual reinforcement will be = 8 × 314 mm2 = 2,513 mm2As per Clause 26.5.3.2 (c) of IS 456 : 2000 Bar Diameter of Lateral Ties:
So, Provide 10 mm dia. bar for lateral ties.
As per Clause 26.5.3.2 (c) of IS 456 : 2000 Pitch of Lateral Ties:
- Least lateral dimension = 500 mm
- 16 × 20 = 320 mm
- 300 mm
Provide 10 mm dia. bar @ 300 mm for lateral ties.
Results
Result Type | Reference | STAAD.Pro | Difference | Comments |
---|---|---|---|---|
Reqd. area of steel (mm2) | 2,355 | 2,367.71 | negligible | |
Spacing of rectangular ties reinforcement (mm) | 300 | 300 | none |
STAAD.Pro Input
The file C:\Users\Public\Public Documents\STAAD.Pro 2024\Samples \Verification Models\10 Concrete Design\India\IS456 2000-Circular Column.STD is typically installed with the program.
STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 09-Dec-20
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 0 2.5 0;
MEMBER INCIDENCES
1 1 2;
DEFINE MATERIAL START
ISOTROPIC CONCRETE
E 2.17185e+07
POISSON 0.17
DENSITY 23.5616
ALPHA 1e-05
DAMP 0.05
TYPE CONCRETE
STRENGTH FCU 27579
END DEFINE MATERIAL
MEMBER PROPERTY
1 PRIS YD 0.5
CONSTANTS
MATERIAL CONCRETE ALL
SUPPORTS
1 FIXED
LOAD 1 LOADTYPE Dead TITLE LOAD CASE 1
JOINT LOAD
2 FY -800
LOAD 2 LOADTYPE None TITLE LOAD CASE 2
JOINT LOAD
2 MZ 162.5
LOAD COMB 3 COMBINATION LOAD CASE 3
1 1.0 2 1.0
PERFORM ANALYSIS PRINT ALL
LOAD LIST 3
START CONCRETE DESIGN
CODE INDIAN
FC 20000 ALL
FYMAIN 415000 ALL
FYSEC 415000 ALL
CLEAR 0.050 ALL
MAXMAIN 20 ALL
MAXSEC 10 ALL
MINMAIN 20 ALL
MINSEC 10 ALL
TRACK 2 ALL
DESIGN COLUMN 1
END CONCRETE DESIGN
FINISH
STAAD.Pro Output
COLUMN
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IS 456 - 2000 C O L U M N D E S I G N R E S U L T S
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IS-456 L I M I T S T A T E D E S I G N
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) Fe415 (Sec.)
LENGTH: 2500.0 mm CROSS SECTION: 500.0 mm dia. COVER: 50.0 mm
** GUIDING LOAD CASE: 3 END JOINT: 1 SHORT COLUMN
DESIGN FORCES (KNS-MET)
-----------------------
DESIGN AXIAL FORCE (Pu) : 800.00
About Z About Y
INITIAL MOMENTS : 162.50 0.00
MOMENTS DUE TO MINIMUM ECC. : 17.33 17.33
SLENDERNESS RATIOS : - -
MOMENTS DUE TO SLENDERNESS EFFECT : - -
MOMENT REDUCTION FACTORS : - -
ADDITION MOMENTS (Maz and May) : - -
TOTAL DESIGN MOMENTS : 162.50 17.33
REQD. STEEL AREA : 2367.71 Sq.mm.
REQD. CONCRETE AREA: 193981.83 Sq.mm.
MAIN REINFORCEMENT : Provide 8 - 20 dia. (1.28%, 2513.27 Sq.mm.)
(Equally distributed)
TIE REINFORCEMENT : Provide 10 mm dia. circular ties @ 300 mm c/c
SECTION CAPACITY BASED ON REINFORCEMENT REQUIRED (KNS-MET)
----------------------------------------------------------
Puz : 2482.79 Muz1 : 173.76 Muy1 : 173.76
INTERACTION RATIO: 0.98 (as per Cl. 39.6, IS456:2000)
STAAD SPACE -- PAGE NO. 7
SECTION CAPACITY BASED ON REINFORCEMENT PROVIDED (KNS-MET)
----------------------------------------------------------
WORST LOAD CASE: 3
END JOINT: 2 Puz : 2526.78 Muz : 176.84 Muy : 176.84 IR: 0.97
============================================================================
********************END OF COLUMN DESIGN RESULTS********************