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Slip-resistant joint

In a slip-resistant joint, preloaded bolts clamp the plates together so hard that friction carries the load. The bolts then do not take shear directly. The capacity depends on the preload, the friction coefficient and how many surfaces slide against each other.

F_s = \mu\,n\,m\,F_p

force the joint can transfer

Symbols

$F_s$	transferable force	N
$\mu$	friction coefficient
$n$	number of bolts
$m$	number of friction surfaces
$F_p$	preload per bolt	N

Example

4 bolts, 2 friction surfaces, $\mu = 0.3$ and 50 kN preload:

$F_s = 0.3\cdot 4\cdot 2\cdot 50 = 120$ kN.

Rust, paint and oil on the surfaces can give much lower friction than the table value.

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