Spacing of Bolts/Rivets in Built-up Beams

$$ S = \dfrac{R I}{V Q} $$

where:

$S$ = spacing of bolts/rivets
$R$ = shear force that the bolts/rivets can resist $R = F_v (A_b)$
$F_v$ = maximum allowable shear stress of bolt/rivet
$A_b$ = cross-sectional area of a single bolt/rivet $A_b = \dfrac{\pi d_b^{2}}{4}$
$d_b$ = bolt/rivet diameter
$I$ = moment of inertia of the beam built-up section
$V$ = shear force on the beam
$Q$ = statical moment of the section above the discontinuity $Q = A \bar{y}$