Ixx property of I-composite section
While creating a model and verifying sectional properties I have noticed some difference in Ixx between the MIDAS value and the one I calculated by hand.
Please see below the screenshot of my calcs and the MIDAS output.
I have reviewed the clarification in Q&A you provided on similar issue: http://manual.midasuser.com/EN_Common/Civil/875/Questions_and_Answers.htm
however I have the following queries in relation to the aspect of Ixx calculation:
I noticed the ratio for slab component calculation used by MIDAS is based on G (shear) modulus not E (Young’s) modulus of the materials, could you please clarify.
In composite I-section it appears the slab torsional stiffness is already reduced by 50% to account for double twist action at orthogonal directions in the grillage model, could you please confirm this is the case.
Could you please clarify what does the Ixx value in Composite Section for Construction Stage represent as per the snapshot below:
1) This is because generally torsion is a shear effect, rather than normal stress, and so the equivalent section is calculated using the shear modulus.