By T. Bart Quimby, P.E., Ph.D.Quimby & Associates

Break force into it’s

components

Move Horizontal Force to Center of

Bolt Group

Move Vertical Force to Center of

Bolt Group

Combine the Two

Moments into One

fy =Py/(Abnb) fx =Px/(Abnb)fmi = M ri / Jfmxi = fmi * dyi/ci

fmyi = fmi * dxi/ci

Find Bolt Stresses

due to Vertical Force Find Bolt

Stresses due to

Horizontal Force

Find Bolt Stresses

due to Moment

Bolt stresses due to Moment are perpendicular to radial lines from

the center of the bolt group

The resultant stress in each fastener equals the vector sum of the stresses applied to it.

fi = sqrt[(fyi + fmyi)2 + (fxi + fmxi)2]Pi = fi Ab

Elastic MethodGood

Very easy and straight forward use of Mechanics

Not so GoodVery conservativeNot consistent with test results resulting in a

widely variable factor of safety