Appropriate application of InitStrainMaterial

[dschmuhl]

Hello all!

I am modeling a prestressed concrete pile that is subjected to gravity and then pushover analysis. For the prestressed strands, I am using truss elements constructed with InitStrainMaterial to impose initial stress. In my case, the initial strain is large and will immediately induce nonlinear behavior in strands. Using this setup, I assume that all of the initial strain is applied in the first step of gravity analysis. Considering the induced nonlinearity due to the application of high initial strain, I am concerned that one step of analysis for initial strain application may not produce reliable results. I am wondering whether there is a way to apply the initial strain gradually in several steps.

As a side note, I am also curious if others have had success and reliable results modeling prestressed strands in this manner. I am still a relative novice with OpenSees so I appreciate help and suggestions.

Thanks!
Dan