Question

The dimensions of a symmetrical welded section are shown in the figure:


( all dimensions are in mm )
The plastic section modulus about the weaker axis (in $c{m}^3$, up to one decimal place) is ______.

• A. 89.89

Answer 1

The correct option is A 89.89
Weaker axis of the section is the minor axis y - y.
Plastic section modulus about y - y axis:


$Z_p=\frac{A}{2}(y_1+y_2)$

$y_1=y_2=\frac{(2\times 70\times 9\times 35)+(182\times \frac{6.1}{2}\times \frac{6.1}{4})}{(2\times 70\times 9)+(182\times \frac{6.1}{2})}$

$=\frac{44946.53}{1815.1}$

$=24.76mm$

$A=(140\times 9\times 2)+(182\times 6.1)$
$=3630.3m{m}^2$

$Z_p=\frac{3630.3}{2}[24.76+24.76]$

$=89886.228m{m}^3$
$=89.89c{m}^3$