Why is the maximum y value different from the centroid?

[kasse]

I've got a sectional area of a beam that is subjected to an axial force N = -100 and momenst M(y) = -50 kNm and M(z)= - 120 kNm. I've found the centroid and the second moment of area around both axes.

How can I compute the maximum axial stress?

Here's the section: http://www.badongo.com/pic/624173


Edit:
I got the correct answer after trying Naviers formula several times:

Max stress = N/A + (M(z)*y(max))/I(z) + (M(y)*z(maks))/I(z)

What I don't understand is: Why is y(maks)=124 and not 151??

 

[radou]

Well, if you got the correct answer, you should ask yourself what ymax and zmax represent in your formula and compare them with your results.

 

[Pyrrhus]

Look at the stress distributions diagrams.