Question

A base plate of 460 x 400 mm is to be provided below a column section ISHB 300@ 576.83 N/m. The bearing pressure from concrete below the base plate is $8.8N/m{m}^2$.
The suitable thickness of the base plate will be ______.
$[Take,b_f=250\text{mm},t_f=10.6\text{mm},t_w=7.6\text{mm},{\gamma }_{m0}=1.1,f_y=250\text{MPa}]$

• A. $24\text{mm}$
• B. $26\text{mm}$
• C. $20\text{mm}$
• D. $22\text{mm}$

Answer 1

The correct option is D $22\text{mm}$

$t=\sqrt{2.5w(a^2-0.3b^2)\times \frac{{\gamma }_{m_0}}{f_y}}$

$\text{a = larger projection}$
$=\frac{460-300}{2}=80\text{mm}$

$\text{b = smaller projection}$
$=\frac{400-250}{2}=75\text{mm}$

$\therefore t=\sqrt{2.5\times 8.8\times ({80}^2-0.3\times {75}^2)\times \frac{1.1}{250}}$
$\Rightarrow t=21.36\text{mm}\simeq 22\text{mm (say)}$