Building Construction Handbook, Eighth Edition

Typical RC Column Details ~

Steel Reinforced Concrete † a modular ratio represents the

amount of load that a square unit of steel can safely transmit

relative to that of concrete. A figure of 18 is normal, with some

variation depending on materials specification and quality.

Area of concrete = 88,743 mm^2

Equivalent area of steel = 18 ¾ 1257 mm^2 = 22626 mm^2

Equivalent combined area of concrete and steel:

88743

+22626

111369mm^2

Using concrete with a safe or working stress of 5 N/mm^2 , derived

from a factor of safety of 5, i.e.

Factory of safety =Ultimate stressWorking stress=25 N=mm

2

5N=mm^2 =5N=mm

2

5 N/mm^2 ¾111369 mm^2 = 556845 Newtons

kg¾9„81 (gravity) = Newtons

Therefore:^556845 9„81 = 56763 kg or 56„76 tonnes permissible load

Note: This is the safe load calculation for a reinforced concrete

column where the load is axial and bending is minimal or nonexistant,

due to a very low slenderness ratio (effective length to least lateral

dimension). In reality this is unusual and the next example shows how

factors for buckling can be incorporated into the calculation.

Simple Reinforced Concrete Column Design (1)