0As per IS.456, the total deflection including the long term deflections need to be limited to Span/250,Span/350 or 20mm.
This includes elastic deflections(which can be retrieved from software or easily calculated) and the long term deflection which is not retrievable from most software. One need to use formulas available in annex of IS456 to calculate long term deflection which is a little challenging to use for many combinations.
Therefore code suggests span/depth ratios if you stick to can ensure that the total deflections are in limit.This Span/depth ratios are not accounting for the deflection control that the rebars provide. It is accounted as a modification factor for tension steel and another modification factor for compressive steel in code.
