Why do we use minimum eccentricity in column design?

When we design an axially loaded column, it is very important to consider some moments along with the axial load. As in the practical scenarios it is not possible to neglect the moment completely. According to IS 456:2000, in order to ensure the safety of column we should consider a minimum value of eccentricity. Also we further reduce the design strengths of concrete and steel for a more optimistic design of such columns.

  • The design strength of concrete is reduced to 0.4 fck
  • Consider 0.67 fy for design strength of steel
  • The value of minimum eccentricity should be :
    • ex min = greater of (l/500 + D/30) or 20 mm
    • ey min = greater of (l/500 + b/30) or 20 mm

Where, ex min and ey min is the minimum eccentricity in x and y direction and l, b and D are the length, width and depth of the column respectively.

Column with an axial load “P” and moment in x direction “Mx ”

So yes even if you are designing the column as a axially loaded column, you should consider the eccentricity in both directions. Thus the moment corresponding to the minimum eccentricity is considered for the design of reinforced concrete column.

Column design

  • RCC Column Design is a free app for designing reinforced concrete columns as per Indian Standards.
  • RCC Design and detailing could be performed for uniaxial and biaxial bending conditions specified in IS456:2000
  • Option to save the design projects in local storage.
  • Detailed calculation steps presented for verification and validation.
column design android app

Leave a Comment