Question

Compute the radius of relative stiffness (in cm) of a 15 cm thick cement concrete slab from the following data:
Modulus of elasticity of cement concrete =
$2.1\times {10}^{5}kg/c{m}^2$
Poisson's ratio of concrete = 0.15
Modulus of subgrade reaction, k $=5kg/c{m}^2$

• A. 44.81
• B. 58.96
• C. 64.85
• D. 53.06

Answer 1

The correct option is B 58.96

Radius of relative stiffness, $l={\left[\frac{E{h}^3}{12k(1-{\mu }^2)}\right]}^{1/4}$

$={\left[\frac{2.1\times {10}^5\times {15}^3}{12\times 5\times {(1-0.15)}^2}\right]}^{1/4}$

$=58.959\simeq 58.96cm$