Question

A double riveted double cover butt joint in plates 25 mm thick with 30 mm diameter rivets at 100 mm pitch. The permissible stress in tension, shear and crushing are 120 MPa, 100 MPa and 150 MPa respectively. What is the efficiency of joint, taking the strength of rivet in double shear as twice that of single shear?

• A. 70%
• B. 60%
• C. 50 %
• D. 68%

Answer 1

The correct option is A 70%

1. Shearing resistance of rivets per pitch length,

$P_a=2\times n\times \frac{\pi }{4}\times d^2\times {\tau }_s$

n = Numbr of rivets per pitch length

for double riveted joint, n = 2

$P_s=2\times 2\times \frac{\pi }{4}\times {30}^2\times 100=282743.33N$

$=282.74kN$

2. Crushing strength per pitch length,

$P_c=n\times d\times t\times {\sigma }_c=2\times 30\times 25\times 150=225000N$

= 225 kN

3. Tearing resistance of the plate per pitch length


$P_t=(p-d)\times t\times {\sigma }_t$

$=(100-30)\times 25\times 120=210000N$

= 210 kN

Strength of solid plate = $p\times t\times {\sigma }_t$

$=100\times 25\times 120$

= 30000 = 300 kN

${\eta }_{joint}=\frac{210}{300}=0.7=70$%