Von Mises stresses and Maximum stresses

Hello

I am currently working on a small bridge project and in connection with that i am doing some detailed stress calculaitons.

In the litterature available for me, the Von Mises stress is the combination of normalstress in the x- and y-direction, AND the maximum shearstress. When i do some minor checks of the stresses found in my model it seems as if MIDAS does not take the shear stress in calculation in the Von Mises stress? Can that be true?

And if so, does that mean, that the "Sig-max" actually in the total Von Mises, where the maximum shear is taken into account?

Best regards 

I can:

The von mises check is calculated as: sqrt(sig_x^2+sig_y^2-sig_x*sig_y-3*tau_max)

You can see som edetalis in the PDF document.

How does Midas calculate the Von Mises stress??

Regard