Here I start discussion on bolted joints in steel structures. I think it will help to give you clear concept on bolted joints in steel structures. There are two types of bolted joint. Those are
Now we should go foreword to know this two type of bolt joint briefly.
When the two members to be connected together by overlapping then the joint is called lap joint.A single bolted lap joint and a double bolted lap joint are shown in figure respectively.
When the two members are to be connected by placing the members end to end and additional plate/plates provided on either one or both sides to attach them properly,then this joint is called butt joint.And the additional plate is called cover plate.
If the cover plate is provided on one side then it is called a single cover butt joint,But if the cover plates are provided on both sides of the main plates then it is called double cover butt joint.A single cover butt joint and double cover double bolted butt joint shown in figure below.
Now the question automatically comes in our mind that which joint is better and which joint is more desirable among all the joints in steel structure?
It is more desirable to provide a butt joint rather than a lap joint for main two reasons:
- In the case of a double cover butt joint,the total shear force to be transmitted by the members is split into two parts and the force acts on each half. But in the case of lap joints,there is only one plate one which the forces acts and,therefore,the shear-carrying capacity of a bolt in a double cover butt joint is double that of a bolt in a lap joint.
- In the case of a double cover butt joint,eccentricity of forces does not exist and hence bending is eliminated,whereas it exists in the case of a lap joint.
Failure of Bolted joints:
- Shear failure of bolts.
- Bearing failure of bolts.
- Bearing failure of plates.
- Tension failure of bolts.
- Tension or tearing failure of plates.
- Block shear failure.