Slab thicknes and tension reinforcement. ration?

[drile007]

I'm using EN 1992-1 for designig concrete elements, particulary slabs. I'm confused in deflection control, where the depth of the slab is limited by the span/depth ratio (in the cases where calculations may be omitted. This span/depth ratio is dependent on the required tension (compression) reinforcement ratio. OK, but where should I take this required reinforcement ratio, from the span or support? There are cases where the reinforcement under the support is much higher than in span.
Thank you in advance.



Drile007

 

[apsix]

From Cl.7.4.2;
"Expressions (7.16.a) and (7.16.b) have been derived on the assumption that the steel stress, under the appropriate design load at SLS at a cracked section at the mid-span of a beam or slab or at the support of a cantilever, is 310 MPa.."

I take that as requiring to use the midspan reinforcement ratio.