From an FEA viewpoint, yes CAESAR II can perform the analysis. This will yield displacements, restraint reactions, and element forces. However, as noted above, the stresses may be suspect due to the thin-wall nature of your system. The B31 codes warn you against D/t ratios above 100.
Piping flexibility analysis assumes the cross-section will not change under load - in other words it remains circular, and overall behavior is dominated by bending. If these assumptions are not valid, neither are the results.
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Regards,
Richard Ay - Consultant