I have a model with gap contacts including friction. The order in which I analyse my loadcases has an effect on the results, because of the stored contact state. If it were frictionless it wouldn't matter. I want a load order independent analysis, and have to have a single OP2 file for further post-processing.
My questions are:
There is no utility to combine op2 files.Why would you really need too? Femap can attach as many op2 files as you need and if you use the option to use the filename in the study title, it is easy to keep track of which results you are looking at.
If you have friction in gap elements, then it is not a linear contact analysis, period. If you are running solution 106, then the analysis and its subcases are a loading history. The only way to go back to the original state, is to create a subcase where zero load is applied, get a converged answer at zero, then begin again in the next subcase.
There is no reason to do this, you should run a separate analysis for each unique load case.
Are you actually trying to set up a preload type condition and then apply different load conditions to this same preload solution?
A more complete description of the intent might help us provide more helpful suggestions.