The given figure shows:

Explanation:

In double cover butt joint, the bolts or rivets can be placed in the following manner:

1. In multiple rows having zero staggered pitch called chain riveting as shown in the following figure:

2. In multiple rows having either non-uniform pitch or having staggered pitch i.e. bolts are placed in a zig-zag pattern as shown below: 

Additional Information

As per IS 800:2007, the tensile strength based on rupture of the net section of the plate is given as:

\({T_{n\;}} = \frac{{0.9{f_u}{A_{net}}}}{\gamma }\)

Where,

fu = Ultimate strength of the plate

Anet = Minimum net area of the section

γ = Factor of safety for plate

To calculate Anet, all possible failure paths (straight as well as zig-zag) are required to be considered and the corresponding net area is to be computed for each possible failure path and the minimum net area is to be selected.

\({A_{net}} = \left\{ {B - n{d_h} + \;{\rm{\Sigma }}\left( {\frac{{{s^2}}}{{4g}}} \right)} \right\}t\; \)

Where,

t is the thickness of the plate joined.

dh­ is the diameter of the hole

s is staggered pitch , g is gauge distance, b is width of plate