Wethere RFEM can be used in the wind turbine concrete tower design? this software looks like don't have the post tension part?
Thank you very much for your new inquiry 
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Our prestressed concrete/tendon add-on is currently in beta, but many features are already available.
You can define and analyze arbitrary tendon layouts within surfaces or members. At present, planar surfaces are supported; curved surfaces (quadrangles) will be released in the coming weeks. Prestressing is currently defined in terms of axial strain. As results, you will obtain all internal forces as well as the interactions between the tendons and the adjacent structural elements 
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We also recommend taking a look at our manual:
https://www.dlubal.com/en/downloads-and-information/documents/online-manuals/tendons
If you have any further questions, please feel free to contact us at any time. You are also welcome to send us your model so that we can better understand your specific requirements.
Best regards,
Max