Difference between butt joint and lap joint

 LAP JOINT -

In this joint, two members are overlapped and connected together.

The load in lap joint has eccentricity because centre of gravity of load in both members are not in same line.

Thus, a couple is formed which causes undesirable bending in the connection and the rivets may fail in tension.

Also due to the eccentricity, the stresses are distributed unevenly across the contact area between the rivets and members to be connected.


 BUTT JOINT -

In butt joint, both members are placed end to end and additional plate/plates (cover plate) is provided on either one side or both sides and connected to the main plates.

When one cover is provided, it is called single cover riveted butt joint and when double cover is provided,it is called double cover riveted butt joint.


 

It was the difference between lap and butt joint. Now, we will know superiority of butt joint.

Butt joint is superior than lap joint because

1. In the case of a double cover butt joint, eccentricity of force does not exist and bending is eliminated whereas it exists in the case of a lap joint.

2. In double cover butt joint, total shear force is distributed in two planes but in lap joint there is only one plane on which force acts. Therefore, the shear carrying capacity of a rivet in butt joint is double than that of a rivet in lap joint 


 

  Thank you.

 

 

 

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