Hi Mathan, I am sure I am missing something... could you please elaborate on your question?
An MPC is a displacement relationship between two nodes. If you want to define a relationship between a node and ground using an MPC, I'd recommend 2 coincident nodes and then SPC the ground side and write the MPC between the coincident nodes.
An MPC is a linear relationship between two or more DOF... you can see the Quick Reference Guide and Linear Static Analysis User Guide for details. This might be something it is best to open a support ticket with our hotline so a more in-depth dialog can be had. You can email .mscnastran.support@mscsoftware.com
