Some time ago I did a version for calculix of this Abaqus example: Abaqus Example Problems Guide (6.13) ( 1.1.1 Axisymmetric analysis of bolted pipe flange connections)
Please, check as well the original paper with test results so you can compare FEM, hand methods and tests.
You can download the ccx inp file from here boltpipe4_calculix.inp - Google Drive
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