In the first part of the paper, variation principles in the elastic and creep theory for prestressed concrete plates are derived respectively.

One important conclusion is that nonlinear creep theory gives almost the same results as those of linear one, but gives rather different results from those of strain-softening model.

Based on the creep theory, the mechanical relationship of VSR and cyclic creep was discussed, and common factors such as stress amplitude, temperature and material properties were analyzed.