In previous version of Revit Structure, if you enabled worksharing for your project, but then you want to change it back to a non-workshared project, there is no function to change it back directly.
In Revit Structure 2012, you can disable worksharing.
1.Click [R]>Open>Project (or click Open icon in Quick Access Toolbar), browse to the central file or local file
2.Check “Detach from Central”，click Open
3.In “Detach from Central” dialog, select “Detach and discard worksets”, the file will be opened
4.Click Collaborate tab>Worksets panel, you will see worksharing is not enabled currently.
So the project you opened now has changed back to normal file without worksharing enabled. You can save this project, or click Collaborate tab>Worksets panel>Worksets to re-enable worksharing again.