
where:
| F | operation force | 
| Ψ | factor of joint tightness | 
| F o | prestress force | 
| F max | maximum operation force in the bolt | 
| ΔF 1 | increasing of prestress in the bolt due to the operation force | 
| ΔF 2 | reduction of clamping force in the joint due to the operating force | 
| Δl 1 | bolt elongation | 
| Δl 2 | compression of connected material | 
| c 1 | bolt spring constant | 
| c 2 | connected material spring constant |