although i set the discipline of the all the floors to "structural", but when i create a sheet it is created for example with this name "A101" referring to architectural system. my question is how to create sheets in structural discipline.
just a dumb first question... are you working in RAC or RST?
Assuming you're working in RST, what project template file did you start with? Was it OOTB, or was it created specifically for your group? If it was OOTB, I think you may have pulled from a RAC template instead of an RST template. If it was created for you, it may have been created beginning with a RAC template.
Either way, once you place your first sheet, the A101 sheet, rename it to S(whatever). The sheets you create after that will consecutively number after the latest sheet creation.