Very simple when we increase the diameter of the reinforcing bar it results in the increased area, so increase the spacing to get the required area of steel.
Exmaple
We can change the 12mm dia @150mm c/c spacing to 16mm dia @
150mm c/c but the area of steel provided will get increased.
Let assume for 1m (1000mm) span
d1=12mm
s1=150 approx No. =8pcs
d2=16mm
s1=? approx No. =?
We have to use this formula
d1^2 / s1 = d2^2 /s2 So s2=266.66 and
approx Spacing 250mm, and
New approx No of the bar will be 4pcs
Note:
This change should not be effective in design work
