Design of columns as per IS 456 code basic formulas

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Design of columns as per IS 456 code basic formulas

The complete column design process as per IS code is determined by using below 3 basic formulas

  1. The minimum eccentricity values as per IS 456 code provision is calculated by using below formula in the column design we need to consider minimum or greater than 20 mm value as eccentricity value.

emin = (L/500) + (D/30) ≥ 20 mm

2. The calculation of main steel is determined by using the below formulae which is shown below

Pu=0.45fckAc+0.67fyAsc

3. The gross area, steel area required for the column section is determined by using below formulae

Ag=Asc + Ac

Basic key points taken in design

The following four key points are used in complete RCC column design

  • Percentage of steel in RCC column is taken as 0.8% to 6% of the gross area.
  • Minimum of 4 Bars are used in Rectangular column and 6 Bars in circular column
  • Transverse reinforcement (pitch not greater than)

Least lateral dimensions

16d (d is small longitudinal bar diameter)

300 mm

  • Diameter of the bar not less than

0.25 d

5 mm



Steps followed in column design by using IS456-2000

The following 4 steps are followed in RCC column design

  1. Calculation of Ac by assuming Asc
  2. Calculation of dimensions of the column by using Ag
  3. Calculation of reinforcement values of main steel Ac
  4. Calculation of transverse reinforcement

 




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