- It should not less than 20 mm and it can be reduced to 15mm for mild exposure & bar diameter of 12mm or less.
- Compression reinforcement is required only in condition which is exceptional.
- Shear reinforcement is not provided generally if slab fails, its thickness is increased.
- Temperature & shrinkage reinforcement are invariably provided in transverse direction to main reinforcement (it is termed as distribution steel or secondary reinforcement)
- Distribution bars are always placed above the reinforcement (so that effective depth are available which offer higher resistance)
- In case of two way slab since load transfer is more on shorter span, main reinforcement along this is kept near to tension face.
Maximum diameter (dmax) should not greater than D/8
- Minimum diameter for distribution steel is 6mm for both fe250 and HYSD.
- No maximum reinforcement criteria for slab.
- Ast,min not less than 0.15% of gross area for Fe250.
- Ast,min not less than 0.12% of gross area for HYSD.
- Maximum spacing of main bars should not be more than (3d or 300mm)min and for distribution steel (5d or 300mm)min
- Before amendment in code IS456, It was 450mm instead of 300 mm
- Shear strength of concrete without shear reinforcement is taken as KTc.
Where, K= Constant that depends on thickness of slab. (1.6-0.002D; D is Overall thickness)
Slabs are checked for development length same as beam.
If rectangular two way slab is supported all four sides with shorter span up to 3.5m & loading up to 3 KN/m2 . then Leff/D ratio should be less than
Note : If rectangular slab is supported all four sides then shorter span is always used in Bending Moment calculations and all above criteria.
