Slab Stiffness (AS3600)

[Ophirian]

Thank you in advance for giving your time to address my question.

I am modeling a flat plate in ETABS and I am trying to figure out what stiffness modifier should I use. I know ACI gives this value to be 0.7 for Column, 0.35 for Beam, and 0.25 for Slabs. I am designing the structure for Australian code and I can't find recommendations for stiffness factor to account for cracking.

Cheers!

 

[Agent666]

Work it out based on your reinforcing content and some averaging of moments and see?

I know SAFE would have an option to do a non linear analysis where cracking was explicitly calculated (been a few years since I used it), maybe Etabs has something similar in the new slab analysis added in version 16?

 

[Tomfh]

Is this what you are looking for?:

6.3.2 Analysis
An elastic analysis incorporating secondary bending moments shall comply with the
requirements of Clause 6.2 and the following:
(a) The effect of lateral joint displacements shall be taken into account.
(b) For strength design of a regular rectangular framed structure, the cross-sectional
stiffness of the flexural members and columns may be taken as 0.4EcIf and 0.8EcIc
respectively

 

[rapt]

Are you modelling this for vertical load analysis or sway analysis for wind or earthquake effects?

 

[Yt.]

This article stand for shear post-cracking probably the code do considerations about this, but i don't which consideration were made. It's easy to find in google.

Post-cracking shear modulus of reinforced concrete membrane elements.
khaldoun Rahal