Etabs modelling of a stadium

[Bishal Nepali]

Hi there. Am designing a stadium on radial shapes. There is a deep beam on the steps of 1270mm and treads of 900 mm. Am trying to design it by extrusion but can i extrude the portion of deep beam too as a slab and assign its section properties as a beam later on?? Does the extrusion as slab and defining as beam does not effect the model?