Stresses in Circular Bolt Patterns

  1. Hello, all. Can someone please direct me to a good source of information which explains how the threaded fasteners in a circular bolt pattern - such as used in a flanged joint - collectively "share the load", and how the stresses which arise due to tension, bending, and shear forces acting upon that circular bolt pattern are distributed? The particular example that I have in mind is one which is comprised of a pair of carbon steel flanges connected by eight(8) @ 5/8"-18NC Socket Head Cap Screws and hexnuts arranged on a 6"-dia. bolt circle. If an ultimate material tensile strength of 170,000psi is used, what would be the maximum tensile and shear loads which could be supported by such an arrangement? Thanx! :surprised
  2. jcsd
  3. FredGarvin

    FredGarvin 5,087
    Science Advisor

    In a "proper" joint, the fasteners shouldn't see too much of the loading apart from loads due to pretension. The frictional force created by the fasteners supports the external loads on the joint. Do a google search for joint diagrams.

    Bickford pretty much wrote the bibles on fasteners: bickford, fasteners&f=false
  4. PhanthomJay

    PhanthomJay 6,186
    Science Advisor
    Homework Helper
    Gold Member

    The above not withstanding, I've always designed flange bolt connections assuming that all bolts equally share the shear load, and equally share any tensile loads from axial forces; then the greatest tensile load in the bolts comes from the bending moments at the connection, in which case the outer bolt sees the greatest load, the center bolts see none, etc., as determined from M/S calculations. It is then common practice to use equally sized bolts in the connection, to accomodate bending moments in any direction. The thickness of the flange plate is also calculated primarily from the bending moments.
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