Question

ISA 100 x 100 x 10 mm (Cross sectional area = 1908 $m{m}^2$) is welded along A and B (Refer to figure in the below question) such that the lengths of the weld along A and B are $l_1$ and $l_2$ respectively. Which of the following is a possibly acceptable combination of $l_1$ and $l_2$.

• A. $l_1$= 150mm and $l_2$ = 60 mm
• B. $l_1$ = 60 mm and $l_2$ = 150mm
• C. Any of the above, depending on the size of the weld
• D. $l_1$ = 150mm and $l_2$ = 150mm

Answer 1

The correct option is B $l_1$ = 60 mm and $l_2$ = 150mm

For a moment free connection CG of the resisting forces must pass through the CG of the member.


CG of the member is nearer to 'B'. Hence,
$h_1>h_2$
Now, Moment of all resisting forces about CG = 0.
$\therefore P_1{h}_1=P_2{h}_2$
$\Rightarrow P_1<P_2$
$l_1<l_2.$

$\therefore$ Option (a) $l_1$ = 60 mm and $l_2$ = 150 mm is a possibly acceptable combination of $l_{1}and{l}_2.$