Maximum spacing between Individual Bars
1- The maximum diameter of the bar used in the slab should not exceed 1/8 of the total thickness of the slab.
2- For main bars, maximum spacing is restricted to 3 times effective depth or 300 mm whichever is smaller.
3- For distribution bars, the maximum spacing is specified as 5 times the effective depth or 450 mm whichever is smaller.
Hence, the diameter of the bar, the thickness of the slab, effective depth and spacing are co-related.
Effective depth
The effective depth (d) of a reinforced concrete floor slab is the distance from the compression face to the centre of the tensile steel when an element is subjected to a bending moment.
Effective depth = depth of slab – clear cover- half of the diameter of the bar
Minimum Distance between Individual Bars
Minimum Distance between Individual Bars and main reinforcing bars shall usually be not less than the greatest of the following:
The following shall apply for the spacing of bars
1- The diameter of the bar if the diameters are equal.
2- The diameter of the larger bar if the diameters are unequal.
3- 5mm more than the nominal maximum size of coarse aggregate.
Clear cover (Nominal Cover) shall be kept in mind while calculating the above parameters.
