Question

A steel flat plate of a rectangular section of size $70mm\times 8mm$ is connected to a gusset plate by three bolts each having a shear capacity of $30kN$. If allowable tensile stress in flat is $160Mpa$, the maximum tension that can be applied to flat plate is :

• A. $110kN$
• B. $75kN$
• C. $85kN$
• D. $90kN$

Answer 1

The correct option is B $75kN$

Net area calculationAlong $1-2-3-4-6$, $A_1=(70-3\times 10+2\times \frac{{30}^2}{4\times 20})\times 8$
$=500m{m}^2$

Along $1-2-3-5$, $A_2=(70-2\times 10+\frac{{30}^2}{4\times 20})\times 8$
$=490m{m}^2$

Along $7-3-5$, $A_3=(70-10)\times 8$
$=480m{m}^2$

$\therefore$ Effective net area, $A_n=480m{m}^2$
Strength of flat in net area rupture $=A_n\times 160N/m{m}^2$
$=480\times 160\times {10}^{-3}kN$
$=76.8kN$
Strength of bolts $=30\times 3=90kN$
$\therefore$ Maximum load that can be applied $=Min(76.8,90)$
$=76.8kN$