Topic: What is exactly the definition of the Shear factor?

Hello there,

I really need to understand the definition of the parameters regarding the shear behaviour.

there are those 3 shear concerning features in ATENA:

Using the fixed crack model activates the law of Kolmar where the shear modulus is reduced due to the crack opening

The aggregate Interlock ag limits the shear stress transfere parralel to the crack

correct me if im wrong!

But what actually is the shear factor. The Theory says:

the normal Stiffness of cracked concrete is calculated by dividing the current tensile strength by the total fracturing strain
means: Ecr=ft(wmax)/eps_fr

we assume the current tensile strength calculated by hordijks crack opening law and devide it by the  strain which is also taken from the crack opening law.
My assumption: The normal stiffness is calculated by the slope of the ascending branch of the crack opening law ??

Then  the shear modulus for mode II and III is calculated by multiplying the normal Stiffnes with the shear factor.

Can someone please explain this to me in words? is there any example i should take this parameter into account or even vary it appart from the default value sf=20 ?

Thank you in advance