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Q: For a ribbed slab :
  • A. clear spacing between ribs shall not be greater than 4.5 cm
  • B. Width of the rib shall not be less than 7.5 cm
  • C. overall depth of the slab shall not exceed four times the breadth of the rib
  • D. All option are correct
Correct Answer: Option D - According to IS 456 : 2000 Cl 30.5 • In-situ ribs shall be not less than 65 mm wide. • They shall be spaced at centres not greater than 1.5 m apart and their depth, excluding any topping shall be not more than four times their width. • Generally ribs shall be formed along each edge parallel to the span of one way slab. • When the edge is built into a wall or rests on a beam, a rib at least as wide as the bearing shall be formed along the edge.
D. According to IS 456 : 2000 Cl 30.5 • In-situ ribs shall be not less than 65 mm wide. • They shall be spaced at centres not greater than 1.5 m apart and their depth, excluding any topping shall be not more than four times their width. • Generally ribs shall be formed along each edge parallel to the span of one way slab. • When the edge is built into a wall or rests on a beam, a rib at least as wide as the bearing shall be formed along the edge.

Explanations:

According to IS 456 : 2000 Cl 30.5 • In-situ ribs shall be not less than 65 mm wide. • They shall be spaced at centres not greater than 1.5 m apart and their depth, excluding any topping shall be not more than four times their width. • Generally ribs shall be formed along each edge parallel to the span of one way slab. • When the edge is built into a wall or rests on a beam, a rib at least as wide as the bearing shall be formed along the edge.