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# Analysing A Bolted Joint4

## Analysing A Bolted Joint

(OP)
I am required to analyse a bolted joint in order to find the most optimum bolt properties. i have done most of the calculations and what is left is just the flange stiffness. the formula i currently have is incorrect. can some one tell me what the formula for flange stiffness (Km) is?

### RE: Analysing A Bolted Joint

The stiffness of a flange is related to the stiffness of the bolted joint. this means that Km is related to Kb. the formula can be located in any engineer's design handbook. the most common one is by Shigely. Just in case you cannot find it the formular for Km is given as

Km=dAE e(b(d/lm)

### RE: Analysing A Bolted Joint

4
mmud9613:  Flange stiffness km, assuming compression zone frusta in bolt grip region, is computed as follows per Shigley, Mechanical Engineering Design, McGraw-Hill, 1989, p. 340, Eq. 8-13, where ki is stiffness of ith plate (layer) truncated frustum.

km = 1/summation(1/ki).

ki = pi Ei dhi tan(alpha)
/ln[ (2 ti tan(alpha)   +   di  -  dhi)(di + dhi)
/((2 ti tan(alpha)   +   di  +  dhi)(di - dhi)) ].

where
alpha = compression frustum apex half angle.
Ei = ith layer modulus of elasticity.
ti = ith layer thickness.
di = outer diameter of outer end of ith truncated frustum layer.
dhi = ith layer hole diameter.
pi = 3.141593.

### RE: Analysing A Bolted Joint

shigley provides a pretty good formular but if you use this then you will have to use all of shigleys formulars otherwise solutions will vary. his way of doing things are right only if you use it from the begining.

### RE: Analysing A Bolted Joint

Have you looked in "Roark's Formulas for Stress & Strain",published by McGraw-Hill?

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