ecu in Concrete04 model

[archeura]

Hi!
I am looking for the relation to compute ultimate strain for the concrete04 model.
The relation I have is:

ecu = 0.004 + 0.9*%a*(fy/300) (mod.Scott,Park & Priesteley)
(fy in N/mm2)
(%a is the shear reinforcing bars percentage)

but its values seem to be so low...

Any suggest? (sorry for mistake!)

Thanks!