Question

The development length required for Fe250 reinforcing bars of 20 mm diameter, as per IS 456:2000 Code for M20 grade concrete and having bars in compression with design bond stress ${\tau }_{bd}=1.2MPa$, is nearly equal to ____ mm. (Nearest integer value)

• A. 725

Answer 1

The correct option is A 725
For bars in compression, ${\tau }_{bd}$ must be increased by $25$%. Thus

$L_d=\frac{\varphi \left(0.87f_y\right)}{4\times 1.25\times {\tau }_{bd}}$

$=\frac{20(0.87\times 250)}{4\times 1.25\times 1.2}=725mm$