Question

The development length in compression for a 20 mm diameter deformed bar of grade Fe 415 embedded in concrete of grade M 25 whose design bond stress is 1.40 N/mm${}^2$, is

• A. 1489mm
• B. 1289 mm
• C. 806 mm
• D. 645 mm

Answer 1

The correct option is D 645 mm

(d)
According to clause 26.2.1 of IS 456: 2000
The development length is $L_d$given by

$L_d=\frac{\varphi {\sigma }_s}{4{\tau }_{bd}}$

For deformed bars ${\tau }_{bd}$ shall be increased by 60%.
For bars in compression ${\tau }_{bd}$ shall be increased
by 25%.

$\therefore$ $L_d=\frac{20\times 0.87\times 415}{4\times 1.4\times 1.6\times 1.25}$

$=645mm$