How to consider non-linear creep coefficient to the model as per code that is not available in Midas data base?

For user-defined creep to accurately calculate creep effects at least 15 functions need to be defined for different ages of loading. Only then does the software takes the value of the creep coefficient correctly and also interpolates accordingly.

First minimum 15 functions for different loading would be defined : 

Then these function would be linked to creep/shrinkage properties. 

We have attached a small file for your reference.

Note that it is just a sample for Creep user defined function and the values mentioned are not to be taken at face value.