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RE: Shear-off bolted connection

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Majid Sarraf wrote:

. > As for DTIs. First, I thought this would be the best, but this did not 
. > last for long, since I thought about the senario that you just mentioned 
. > too (over-pretensioning). 
. > 
. > I have an explanation though, and I hope this can be used in a way to
. > improve they way the washers are made or used. Due to the size and form (
. > arch type) of the typical bumps on these washers, froce-deformation after
. > initial yielding becomes highly non-linear, as opposed to a nice yield
. > plateau. Non-linearity in geometry and property of the material, can both
. > make their resistance highly sensetive to the deformation imposed. Perhaps
. > some test results would confirm this, and can indicate how much 
. > overstrength would be developed in washers. 
. > 

Actually the arch shape is necessary.  If the deformations were a constant 
(uniform) size, then there would be no increase in force as the bolt was 
tightened and there would be no increase in bolt tension after first yield.  
(The yield plateau is horizontal, or nearly so.)

A. Roger Turk, P.E.(Structural)
Tucson, Arizona