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RE: Bolts as Fuse Link

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The concept that you are using is called "frangibility".  Frangible
connections are commonly specified by the FAA for structures at airports and
DOT's for unprotected structures adjacent to roadways.  The concept is to
have structures that break away due to airplane or vehicular impact.  The
bolts are generally reduced in section by machining at the shear plane, and
the coefficient of friction of the shear plane is maintained by Teflon
sheets or other materials that won't change due to weather exposure.  

After you push your knowledge of fracture mechanics to the limit you still
should test the connection assembly.  I haven't worked on a frangible
connection in years, but I would search the web sites of FAA, FHWA, FDOT,
state DOT's for frangible connections.

Harold Sprague
The Neenan Company

-----Original Message-----
From: John W. Bryan [mailto:jaybryan(--nospam--at)]
Sent: Friday, June 25, 1999 11:09 AM
To: seaint(--nospam--at)
Subject: Bolts as Fuse Link

I am designing a dolphin to take impacts from a docking ferry.  I would like
to connect the plum and batter piles with bolts which will act as a fuse
link, and shear at a certain load.  My question:
Does anybody out there have, or can you direct me to, a force/displacement
diagrams for shearing bolts?  This would help because I am concerned with
(a) the maximum force required, and (b) the energy absorbed.
Jay Bryan