slab thicknes and tension reinforcement. ration

huangyhg

slab thicknes and tension reinforcement. ration?
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?fff"> there are cases where the reinforcement under the support is much higher than in span.
thank you in advance.
drile007
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.