Question

For a slab spanning in two directions, the ratio of span to the depth of slab should not exceed

1. 10
2. 20
3. 35
4. 50

Answer 1

Correct Answer - Option 3 : 35

Concept:

Control of deflection:

The vertical deflection limit may generally be satisfied if

(a) Basic span to effective depth ratio for span up to m is

Types of Beams: \(\frac{{{\rm{span}}}}{{{\rm{effective\;depth}}}}\)

For cantilever → 7

For simply supported → 20

For continuous → 26

(b) For span > 10 m effective depth \( = \frac{{{{\left( {{\rm{span}}} \right)}^2}}}{{10 \times {\rm{A}}}}\)

Where ‘A’ is span to effective depth ratio for span up to 10 m.

(c) Deflection check for two way slab:

Support Condition	Span/overall depth
	Mild steel	Fe415/Fe500
Simply supported	35	28
Continuous	40	32

So, From the above table It is clear that Span/depth ratio for two way slab should not be greater than 40. But From the given options, 35 is the closest one.