Reinforced concrete columns - Design

Remember:

(1) The reinforced concrete column is a compression member the effective length of which exceeds three times the least lateral dimension.

(2) The reinforced concrete column is considered as a short column if its slenderness ratio l/b is less than 12.

(3) If in any plane one end of the column is unrestrained, its unsupported length l, shall not exceed 100*b*b/D.  where b= width of that cross section and D= depth of the cross section measured in the plane under consideration.

(4) All columns shall be designed for a minimum eccentricity of 20 mm.

(5)  All columns shall be designed for a minimum eccentricity equal to   l/500 + b/30  where l = unsupported length of the column and b= least lateral dimension of column.

(6) The area of the longitudinal reinforcement in a column shall not be less than 0.8% of the gross area.

(7) The area of longitudinal reinforcement in an R.C.C. column shall not exceed 6% of the gross area.

(8) The minimum numbers of longitudinal bars in a column of rectangular section is 4.

(9) The minimum numbers of longitudinal bars in a column of circular section is 6.

(10) The diameter of a bar of a column shall not be less than 12 mm.

(11) The spacing of longitudinal bars measured along the periphery of the column shall not exceed 300 mm.

(12) In a pedestal of a column the area of the longitudinal reinforcement shall not be less than 0.15% of the gross area.

(13) Pedestal is a compression member whose effective length does not exceed 3 times the least lateral dimension.

(14) When polygonal lateral ties are provided in a column the internal angles of the polygon shall not exceed 135 degrees.

(15)  The diameter of the lateral ties in a column shall not exceed the one-fourth of the diameter of the bars in longitudinal direction.

(16) The diameter of lateral ties in a column shall not be less than 5 mm.

(17) The pitch of the lateral ties shall not exceed 16 times the diameter of the longitudinal bars, and 48 times the diameter of the ties.

(18) The diameter of the helical reinforcement in a column shall not be less than 5 mm.