Civil Engineering - RCC Structures Design - Discussion

It's 30 for the simply supported slab, 20 is for the beam.

@Adi.

The correct answer should be 20 and what you are telling is for two-way slabs.

@Amar @Prasad.

How did you say the answer is correct by pointing to the IS 456 Provision?

Where is 30 in it? Please explain clearly.

Well, it depends on the grade of steel being used.

Here, it seems valid for low grade upto 300MPa yield steel.

Continues beam-20.

For slab it should be 35. 20 for simply supported Beam.

Normal ratio:
Cantilever 7.
SS beam 20.
Continuous 26.

Max ratio:
Cantilever 12.
SS beam 30.
Continuous 35.

The above answer is right.

But as per cl 24.1, cl 23. 2.1 IS456 2000,

Basic values of~span to effective depth ratios for spans up to 10 m.
Cantilever 7.
Simply supported 20.
Continuous 26.
For spans above 10 m, the values in (a) may be multiplied by lo/span in meters, except for cantilever in which case deflection calculations should be made.

For two-way slabs of short spans (up to 3. 5 m) with mild steel reinforcement, the span to overall depth ratios given below may generally be assumed to satisfy vertical deflection limits for loading class up to 3 kN/m.

Simply supported slabs 35.

Continuous slabs 40.
For high strength deformed bars of grade Fe 415. The values given above should be multiplied by 0.8.

Above answer is right.

But as per cl 24.1, cl 23. 2.1 IS456 2000,

Basic values of~span to effective depth ratios for spans up to 10 m.
Cantilever 7.
Simply supported 20.
Continuous 26.
For spans above 10 m, the values in (a) may be.

Multiplied by lo/span in metres, except for cantilever in which case deflection calculations should be made.

For two-way slabs of short spans (up to 3. 5 m) with mild steel reinforcement, the span to overall depth ratios given below may generally be assumed to satisfy vertical deflection limits for loading class up to 3 kN/m.

Simply supported slabs 35.

Continuous slabs 40.

For high strength deformed bars of grade Fe 415. The values given above should be multiplied by 0.8.

Above answer is right.

But as per cl 24.1, cl 23. 2.1 IS456 2000,

Basic values of~span to effective depth ratios for spans up to 10 m.
Cantilever 7.
Simply supported 20.
Continuous 26.
For spans above 10 m, the values in (a) may be.

Multiplied by lo/span in metres, except for cantilever in which case deflection calculations should be made.

For two-way slabs of short spans (up to 3. 5 m) with mild steel reinforcement, the span to overall depth ratios given below may generally be assumed to satisfy vertical deflection limits for loading class up to 3 kN/m.

Simply supported slabs 35.

Continuous slabs 40.

For high strength deformed bars of grade Fe 415. The values given above should be multiplied by 0.8.