In the fastener dialog box there is a pull-down called, "Stiffness" where the default is, "Using diameter and material" that can be changed to, "Use spring stiffness property". Selecting this option will allow you to use the properties of an advanced spring, of which you can set Kyy and Kzz to 0 (these are the stiffness components that are orthogonal to the direction of the fastener direction; see the image below). You will, of course, have to determine what stiffness values to use (which are tied to the size and material associated with your bolt). Also make sure that you have "Frictionless Interface" checked if you don't want the faying surfaces to carry any shear.
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Where:
- Kxx—extensional stiffness along the axis of the fastener.
- Kyy—shearing stiffness
- Kzz—shearing stiffness
- Txx—torsional stiffness of fastener
- Tyy—bending stiffness
- Tzz—bending stiffnes
