By T. Bart Quimby, P.E., Ph.D.
Quimby & Associates
Elastic Method
Move
Horizontal
Force to
Center of
Bolt Group
Move
Vertical
Force to
Center of
Bolt Group
Break force
into it’s
components
Combine
the Two
Moments
into One
Elastic Method
f y =Py/(Abnb)
Find Bolt
Stresses
due to
Vertical
Force
fx =Px/(Abnb)
Find Bolt
Stresses
due to
Horizontal
Force
fmi = M ri / J
fmxi = fmi * dyi/ci
fmyi = fmi * dxi/ci
Find Bolt
Stresses
due to
Moment
Bolt stresses due to Moment are
perpendicular to radial lines from
the center of the bolt group
Elastic Method
The resultant stress in each
fastener equals the vector
sum of the stresses applied
to it.
fi = sqrt[(f yi + fmyi)2 + (fxi + fmxi)2]
Pi = fi Ab
Elastic Method
 Good
 Very easy and straight forward use of Mechanics
 Not so Good
 Very conservative
 Not consistent with test results resulting in a widely
variable factor of safety