What is the difference between distribution steel and extra bars in slab?

Torsion Bars Are Not Extra Bars They Are Essential

I don't agree with smit patel.

Torsion Steel is not categorised as extra bars. Torsion steel is important part of two way slab reinforcement it act separately.

Extra bars are the one which might or might not be provided in structure.

Extra Bars

As we knows continuous slab is subjected to hogging moment at continuous edges.

So how do we resist the hogging moment caused at continuous edge ?

We deal with hogging moment by bending the bars at end alternatively.

In most of the cases this alternate bent up bars are enough to resist the hogging moment , but in some case it might be insufficient. Thus in such cases few extra bars are provided at the top at continuous edge of slab.