Bolted Joint Memebers Stiffness Calculation

[struclearner]

When the Bolted Joint members stiffness under the grip length, using Rotscher's pressure-cone method is calculated, the upper member, the top frusta starts from the washer face and the outer diameter of top frusta is taken 1.5 x of bolt shank diameter.
In the case of flanged screws, where the screw has flange under the head, and for 1.5 screw nominal diameter, the flange diameter is 1.5 x of this diameter and the flange height is about 0.383 inches.
I could not see any example of joint members stiffness calculations with flanged screws in Mechanical Engineering Design by Shigley's (7th & 10th Edition).
My question/clarification is, do the screw flange thickness will be included in the members stiffness calculations, if it does, this will increase the top frusta height/length.

Thanks for your input and valuable help.

Reference: Mechanical Engineering Design by Shigley's (10th Edition)
Chapter 8: Screws, Fasteners, and the Design of Nonpermanent Joints
Section 8-5: Joints-Member Stiffness
Example 8-2

 

[desertfox]

Hi

I would ignore the flanges of the bolt/screw when looking at the joint stiffness, this site below deals with joint stiffness as you describe however there are no washers shown on the illustrations.

https://roymech.org/Useful_Tables/Screws/.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein