Can multiple fact tables have the same structure? I'm designing the schema of a data base and I have two solutions :
the first is to use one fact table linked to multiple dimensions.
the second is to use multiple fact tables with same structure for each group (I have eight groups ) and all these fact tables are linked to the same eight dimensions.

I think the second solutions sounds good because I can avoid some joins to analyse per group.But I'm not sure about using multiple fact tables with same attributes for each group.
for example :
Fact1:
Id_Ap #|Id_cst#|Id_Ac#|Id_Dt#|Bp
Fact2:
Id_Ap#|Id_cst#|Id_Ac#|Id_Dt#|Bp
.. Fact 8 : the same.
Yes and depending on what you are doing that might be a very good idea. I will use a request table as an example.

Request comes in and goes to a submitted request table. After it gets processed it moves to a pending table. If it gets approved it moves to an approved/completed table. If it gets canceled it gets moved to a canceled table. Having the same table structure allows for the system to easily move data around and for users to easily select data from any of the tables.

While this can also be done with a status column the design of the database and amount of data could make it more desirable to have a separate table for each state.