Does Class C Apply to PT Two-way Slab

Hi there,

I'm working on a PT two-way slab. Out of curiosity I switched the design environment from Class U to Class C and wanted to see if the design results were the same. Turns out, the design status is the same. Error 18.3.3 still shows up even when the design strip is designed as Class C.

Does that mean RAM Concept assigns Class U to a flat slab automatically? If so, when would Class C apply to a PT two-way slab?

Thanks,

Jonathan