Flat Slab Deflection

[grillo05]

When  I look at the deflection in a slab the box dialogue show active deformation. Does it mean  long term deflection - instantaneous SW deflection. I have seen the option to reduce the Inertia of the section and ACI recommend to use a factor 0.25 for Slabs, is this to estimate the crack effect? , Should I also use a reduced E modulus for the concrete to take into account the lost of strength or applying that coefficient is enough?

[grillo05]

Hello,

I am designing a RC slab and I would like to know which deflection is showed in the tab Deformations/Active, is instant deflection or long term deflection?

[tony.ridley]

my guess is instant

[Artur.Kosakowski]

The elastic one as you display the results of static analysis of the model rather then cracked deflection. The latter (which is the final one) can be displayed on the SLS tab of the Reinforcement map dialog instead.

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[Rafal.Gaweda]

This is map for elastic \ FEM calulated deflections. To have "cracked" deflection you have to modify E or Iy

or run RC design and look at map here: