Question

In a reinforced concrete section, the stress at extreme fibre on compression side is $6MPa$. The depth of neutral axis is $60mm$. The grade of concrete and steel are $M20$ and $Fe415$ respectively. Assuming linear elastic behaviour of concrete, the effective curvature of the section (in per mm) is____$\times {10}^{-6}$

• A. 4.4

Answer 1

The correct option is A 4.4

$\frac{M}{I}=\frac{f}{y}=\frac{E}{R}$ (flexure formula)
$E=5000\sqrt{f_{ck}}=5000\sqrt{20}=22631N/m{m}^2$
$\frac{1}{R}=\frac{f}{Ey}$
$=\frac{6}{22361\times 60}=4.47\times {10}^{-6}permm$