Percentage of resistance threaded surface in respect to total threaded surface (p):
<select name="percent">
<option value="0.75">75%</option>
<option value="0.50">50%</option>
<option value="0.40">40%</option>
</select>

S = p \cdot ( \pi  d_r h_{nut} )

F_{max,bolt} = \sigma_{y,bolt} * A_{res} = \sigma_{y,bolt} * \pi * (0.9d)^2/4

SF = 2
F_{nut} = \tau_{res} * \pi * d * p * h_{nut} / SF = 1 / 3^{0.5} * \sigma_{nut} * \pi * d * p * h_{nut} / SF 

<a href="http://www1.unipa.it/giovanni.petrucci/Disp/Bulloni.pdf">Reference</a>