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Bolt Failure Modes

There are six bolt failure modes which can be reported in SWedge:

  • Pullout
  • Tensile
  • Stripping
  • Shear
  • User-Defined
  • Compression
The term "Failure" as used here, does not necessarily mean that a bolt has actually failed. It really refers to the potential failure mode of a bolt, if wedge failure occurs. Remember that the SWedge analysis is a limit equilibrium analysis. The actual stresses and deformations of the bolts are not computed.

Pullout / Tensile / Stripping

These are all tensile failure modes and are determined by the Bolt Force Diagram, and the point at which a wedge plane intersects the bolt. For examples of bolt force diagrams, see the Bolt Force Diagram topic, and the topics for the individual bolt types in SWedge(e.g. Cable Bolt, Swellex etc).

Pullout Pullout Pullout
Pullout, tensile, and stripping bolt failure modes


The Shear failure mode will only be reported if:

  • the "Use Shear Strength" option is selected, for a given bolt type.
  • a bolt intersects a sliding plane of a wedge (as opposed to a dilating plane)

See the Bolt Shear Strength and Bolt Support Force topics for more information.

Shear bolt failure mode
Shear bolt failure mode


If a bolt failure mode is reported as User Defined, this simply means that the bolt (tensile) properties have been defined with a User-Defined bolt type (i.e. the user creates an explicit Bolt Force diagram, rather than entering tensile properties). For more information, see the User Defined Bolt topic.

For a User-Defined Bolt type, it does not matter where a wedge plane intersects the Bolt Force diagram. The failure mode will simply be reported as User Defined. The specific modes of Pullout, Tensile or Stripping are not reported.


The Compression failure mode will only be reported under the following circumstances:

Only if all three of these conditions apply, will Compression be reported as a bolt failure mode.

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