Question

A column section ISHB 350@674 N/m carries an axial load a nd bending moment. A base plate provided is 450 x 550 mm with 100 mm projections on each side of column flange. Maximum and minimum compressive stress in concrete at edges is
$3.938N/m{m}^{2}and1N/m{m}^2.$
The thickness of base plate if permissible bending stress is
$185N/m{m}^2$

• A. 25 mm
• B. 12 mm
• C. 20 mm
• D. 16 mm

Answer 1

The correct option is A 25 mm

Stress under critical section x-x

$=1+(3.938-1)\frac{450}{550}=3.4038N/m{m}^2$

Moment at the critical section = moment of hatched area about section x-x

$=3.4038\times 100\times \frac{100}{2}+\frac{(3.938-3.4038)}{2}\times 100\times (\frac{2}{3}\times 100)$

$=18799.66N-mm$

Moment of resistance at critical section x-x

$=\frac{1}{6}\times 1\times t^2\times {\sigma }_{bs}=\frac{1}{6}\times t^2\times 185N-mm$

Moment of resistance

$=\frac{1}{6}\times t^2\times 185=18799.66$

$t=24.69mm$

$=25mm$