In the Mesh input, highlight the slab (which you designated as curve beam), right click to call up the 'selection properties'.
Then under the 'behavior tab' and 'behavior', change the 'two way slab' to 'no torsion 2 way slab'.
Although i'm not sure how Concept does the beam torsional design. As you said, i see no reason why would you need to release the torsion of the beam.
In fact, IMO, i thought it would be necessary the curve beam to design to resist the torsion.
I personally have not designed the curve beam before, can't give you further advice on that.
However, you could compare the output with some manual calculation to verify. There's a saying that FEM programs have lot of 'black box', you'll need some verification on the result.
Then under the 'behavior tab' and 'behavior', change the 'two way slab' to 'no torsion 2 way slab'.
Although i'm not sure how Concept does the beam torsional design. As you said, i see no reason why would you need to release the torsion of the beam.
In fact, IMO, i thought it would be necessary the curve beam to design to resist the torsion.
I personally have not designed the curve beam before, can't give you further advice on that.
However, you could compare the output with some manual calculation to verify. There's a saying that FEM programs have lot of 'black box', you'll need some verification on the result.