Circular slabs are commonly used as roofs or floors with a circular plan, such as water tanks. They experience bending stresses in two perpendicular directions - radially and circumferentially. Reinforcement is provided as a mesh of bars with equal cross-sectional area in both directions. Near the edges, additional radial and circumferential reinforcement may be needed if edge stresses are significant. Circular slabs are analyzed based on elastic theory, and deflect into a saucer shape under uniform loads, developing tensile and compressive stresses on the convex and concave surfaces respectively. Reinforcement must be provided in both radial and circumferential directions near the convex surface.

1. Circular Slab

2. Introduction
• Uses of Circular Slabs:
1.Roof of a room or hall circular in plan
2.Floor of circular water tanks or towers
3.Roof of pump houses constructed above tube
wells
4.Roof of a traffic control post at the
intersection of roads

3. • In circular slab, Bending takes place in
distinctly two perpendicular directions along
the two spans.
• Reinforcement is provided in the form of a
mesh of bars having equal area of cross
section in both the directions, the area being
equal to that required for the bigger of the
radial and circumferential moments.
• However, if the stresses near the edge are not
negligible, or if the edge is fixed, radial and
circumferential reinforcement near the edge
becomes essential.

4. Circular slab
• Circular slabs are more commonly used in the design of circular
water tank containers with flat bottom and raft foundations.
• The analysis of stresses in these slabs is generally based on elastic
theory. Under uniformly distributed loads, these slabs deflect in the
form of a saucer and develop radial and circumferential stresses.
Tensile stresses develop on the convex surface and compressive
stresses develop on the concave surface.
• Tensile stresses must be provided in the radial and circumferential
directions near the convex surface.
• Alternatively, reinforcing bars can be provided in two mutually
perpendicular directions instead of in the radial and circumferential
directions.
• Normally, near the Centre of the slab, reinforcement is provided in
the form of mutually right angle mesh; and near the edge of the
slab, in the form of radial and circumferential bars.

5. Simply supported slab with, uniformly
distributed load

6. Simply supported slab with, uniformly
distributed load

7. Fully restraint slab with uniformly
distributed load

8. Fully restraint slab with uniformly
distributed load

9. Simply supported slab with concentric
load

10. Simply supported slab with concentric
load

11. Simply supported slab with uniformly
distributed load inside a concentric circle

12. Simply supported slab with uniformly
distributed load inside a concentric circle

13. Simply supported slab with a circular hole
and with uniformly distributed load

14. Simply supported slab with a circular hole
and with uniformly distributed load

15. Simply supported slab with a circular
hole and with concentric load

16. Simply supported slab with a circular hole
and with concentric load

17. Simply supported slab with a circular hole
and linearly varying distributed load

18. Simply supported slab with a circular hole
and linearly varying distributed load

19. Simply supported slab with a circular hole
and linearly varying distributed load