> The force in the anchor bolt is equal to the GREATER of the
> pretension OR the applied bolt load. If the pretension is 125% of
> the fatigue loading it should never change, hence, zero stress
> range, hence zero fatigue (unless I'm misunderstanding your
> description of the problem).
This assumes that the bolt is a lot softer (compliant soft, not
brinnell soft) than the contact compliance of the parts being clamped
together. This is usually true for bolted joints steel, but maybe not
for anchor bolts embedded in concrete. What actually happens in that
case is that the change in applied loading nearly equals the change
in contact force so the bolt tension doesn't change much. So a cyclic
applied load doesn't cycle the bolt load, provided the two halves of
the joint remain in contact.
You might want to check your joint design compliances to make sure
the relative stiffness is such that the bolt load doesn't cycle.
There's a good explanation of all this in machine design handbooks
and the arithmetic isn't difficult. If you're really intending to do
this, you might also want to make provisions that mimic the
installation of preloaded high strength bolting in ordinary
structural joints.
Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw@skypoint.com | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania
1864)
http://www.skypoint.com/~chrisw/
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