peteroznewman
Bbp_participant
I don't write APDL code, so someone may answer the question you asked.
I will tell you that a common approach to introduce a geometric imperfection is to update the nodal coordinates with a tiny fraction of the deformed shape from a linear eigenvalue buckling solution before starting a nonlinear static structural solver to evaluate a post-buckled state. In the link below are many links to posts on this site to this concept.
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