Question

A flitched timber beam made up of steel and timber has a section as shown in figure below. The permissible stress in steel and timber are 100 N/mm${}^2$ and 5N/mm${}^2$ respectively. The moment of resistance of the beam is________kNm.

• A. 40
• B. 14
• C. 22
• D. 6

Answer 1

The correct option is B 14

Moment of resistance of timber section,

$M_T={\sigma }_T\times Z_T$

$=5\times (2\times \frac{60\times {200}^2}{6})=4kNm$


Moment of resistance of steel section,

$M_s={\sigma }_s\times Z_s$

$=100\times \frac{15\times {200}^2}{6}Nmm=10kNm$

$\therefore \text{Total moment of resistance of beam = 4 + 10 = 14 kNm}$