One way Slab is a slab in which one side is very large compared to the other one. Generally, if one side is more than double of the other one, the slab will be one way.
Now in one way Slab as one side is bigger than the other side most of the load is carried by that side only so providing main reinforcement corresponding to that load-carrying side will be sufficient. So to support that larger side Main Reinforcement is provided perpendicular to that side or parallel to shorter side and along longer side(I.e. parallel) only steel required for supporting is provided called distribution steel which will not help in carrying any load.
Main steel will be calculated by the formula for limit state design formula which is derived by equating compressive and tensile forces which are
Ast = 0.5Fck/Fu{1-√1–2.6Mu/Fck.b.d}b.d
and Distribution Steel is calculated as
0.15% of Ag for mild steel.
0.12% of Ag for tor steel.
Where, Ast=area of steel in tension
Fck= Characteristic strength for a grade of concrete used.
Fu=Ultimate strength of the steel used.
Mu=Ultimate moment resisted
b=breadth of the section
d=depth of the section
Ag=Gross area for the section.
