What is the Difference between Main Reinforcement Bars and Distribution Reinforcement Bars in Slab?

Difference between Main Bars and Distribution Bars

Difference between Main Bars and Distribution Bars

Main reinforcement bars placed in bottom of distribution reinforcement bars. Distribution bar placed on top of main bars. Main bars are placed at the shorter span direction, to transfer the bending moment at the bottom of the slab to the beam. 
Distribution bars are used in the slab to resist the shear stress. Because the cracks are developed due to shear stress on the top of the slab.

Main Bars:

  •  It resist bending moment.
  •  It resist tensile stress produced in the slab.
  •  It resist superimposed and dead load of the slab.
  •  Diameter of main bar should not less than 8mm(HYSD bars) and 10mm for plain bars.
  •  Diameter of main bar is always grater than distribution bar. 

Distribution Bars:

  •  It distribute the superimposed load equally to the main bars.
  •  It resist temperature stress produced in the slab due to temperature variations.
  •  It maintain the main bars in their proper position (spacing).
  •  Diameter of distribution bar should not less than 8 mm.
  •  Diameter of distribution bars always less than main bars.