Thickness of Cover Plates in Double Cover Butt Joints

When joining two plates end-to-end using a butt joint, cover plates are often used on one or both sides to connect the main plates. In a double cover butt joint, two cover plates are used, one on each side of the main plates.

The thickness of these cover plates is important for ensuring the strength of the joint. Design codes and standards provide guidelines for determining the appropriate thickness.

For a double cover butt joint, the thickness of each cover plate is typically specified relative to the thickness of the main plate. Let 't' represent the thickness of the main plates being joined.

According to common design practices and codes (like IS 800), the thickness of each cover plate in a double cover butt joint is taken as 5/8 times the thickness of the main plate.

So, if the main plate thickness is 't', the thickness of each cover plate is \(\frac{5}{8}t\).

Let's look at the given options:

• Option 1: \(\frac{8}{5}t\) - This would mean the cover plate is thicker than the main plate, which is not the standard for double cover joints.
• Option 2: \(\frac{5}{8}t\) - This matches the standard requirement for the thickness of each cover plate in a double cover butt joint.
• Option 3: \(\frac{3}{5}t\) - This is a thinner option, often used for single cover butt joints or might represent minimum requirements in some cases, but \(\frac{5}{8}t\) is the more common standard for double cover plates to ensure adequate strength.
• Option 4: \(\frac{5}{3}t\) - This would mean the cover plate is significantly thicker than the main plate, which is not standard practice.

Therefore, the thickness of each cover plate in a double cover butt joint is taken as \(\frac{5}{8}\) of the thickness of the main plate 't'.