Question

The span to depth ratio limit is specified in IS : 456-1978 for the reinforced concrete beams, in order to ensure that the

• A.
  tensile crack width below a limit
• B.
  shear failure is avoided
• C.
  
  stress in the tension reinforcement is less than the allowable value
• D.
  
  deflection of the beam is below a limiting value

Answer 1

The correct option is D


deflection of the beam is below a limiting value
For beams & slabs, the vertical deflection limits may generally be assumed to be satisfied, provided that the span to depth ratio are not greater than the values obtained as below

(i) Basic values of span to effective depth ratios for spans upto 10 m

Cantilever = 7
Simply supported = 20
Continuous = 26

(ii) For spans above 10 m, the value in (a) may be multiplied by $\frac{10}{Span}$ except for cantilever in which case deflection calculation should be made.