The cost of the bolts is more,but the rapid growth in steel industry requires bolted connections for faster construction. It takes less time to erect structure with bolted connections. Bolts may be used for the structures not subjected to excess vibrations.
The erection works with bolts is noise less and less skilled workers can also handle it.
Let’s find out the logic behind the number 8.8…
For property class – 8.8, the yield stress = 640 Mpa
In 8.8, The first number 8 indicates 1/100 of nominal tensile strength .Hence the tensile strength = 800 Mpa.
The second number indicates 10 times the ratio between lower stress(proof stress) and nominal tensile strength(yield stress ratio) means, 10 times the yield stress = 10 x 640/800 = 6400/800 = 8.
The multiplication of these two numbers gives 1/10 of the yield stress = 8 x 8 x 10 = 640Mpa.
Finally, remember simply like for 8.8 class of bolts yield stress = 8 x 8 x 10 = 640 Mpa
