Question

As per IS 456:2000 provisions for two-way slabs with continuous edges, the longitudinal steel reinforcement to be provided in the edge strip is based on:

• A. the calculated minimum bending moment
• B. the area of longitudinal steel provided in the middle strip in the shorter span
• C. the area of longitudinal steel provided in the middle strip in the longer span
• D. the prescribed minimum cross-sectional area of longitudinal steel for slabs

Hint:

When working with slab reinforcement, always refer to the relevant IS code for minimum reinforcement criteria, especially for edge strips and boundary conditions.

Answer 1

The Correct Option is D

According to IS 456:2000, the minimum cross-sectional area of longitudinal steel reinforcement in the edge strip of a two-way slab with continuous edges is prescribed based on the following:

• The edge strips have minimum reinforcement requirements to ensure proper load distribution and avoid excessive cracking.
• The prescribed minimum cross-sectional area of reinforcement for edge strips is typically based on a percentage of the slab's gross area.

The minimum reinforcement area is provided in terms of the specified percentage of the total slab area and is related to the type of steel used. For instance:

• For Fe250 grade steel, the minimum reinforcement is 0.15% of the slab's total gross area (\( BD \)).
• For HYSD steel, the minimum reinforcement is 0.12% of the slab's total gross area (\( BD \)).

This ensures that there is enough reinforcement in the edge strips, especially in slabs with continuous edges, which are more susceptible to stresses and cracking due to their boundary conditions.

Thus, the correct answer is option (D) because the longitudinal steel reinforcement in the edge strip is based on the prescribed minimum cross-sectional area, as specified by IS 456:2000.

Options (A), (B), and (C) do not refer to the prescribed minimum cross-sectional area but rather to other aspects like calculated bending moments or the reinforcement in the middle strip.