Parallel-spring axial screen
Bolted-joint separation
Inputs
Preload for one stated bolt/joint condition; uncertainty and loss are not modeled.
User-entered equivalent axial bolt stiffness for the stated grip condition.
User-entered equivalent axial clamped-member stiffness; geometry is not inferred.
Known applied separating load on this one joint; positive is separating and negative is compressive.
Results
Bolt load fraction CC
33.333
%External-load share carried by boltFb
6
Residual clamp forceFc
8
Ideal separation-load threshold
30
Threshold minus stated external load
12
C = kb/(kb+km); ΔFb = CP; Fm = Fp−(1−C)P; Psep = Fp/(1−C)
A first-pass number, not a code check, certification, or approval. Read the method and its limits below. What this is and is not.
Nearby: Axial response · Beam deflection & reactions · Elastic stability · Solid-shaft torsion
Method
Formula, when it applies, and when it does not
Estimate load sharing, residual clamp force, and a separation-load threshold from bolt/member stiffness and preload for one axial joint.
C = kb/(kb+km); ΔFb = CP; Fm = Fp−(1−C)P; Psep = Fp/(1−C)
When
- One preloaded axial joint
- User-entered stiffnesses
- Linear parallel springs
- Known external load
Don’t
- This is a one-bolt, axial, linear parallel-spring screen with user-entered equivalent stiffnesses. It does not infer stiffness from geometry, distribute a system load among bolts, account for preload variation or relaxation, nonlinear contact, shear, bending, thermal effects, fatigue, gasket behavior, joint slip, safety factors, or prove that a joint will not separate.
SAND2008-0371, Guideline for Bolted Joint Design and Analysis (Sandia)