From what I understand...

The "Worst Case Stress" in a beam analysis the software calculates the highest stress at a critical point on the cross-section by combines the axial and bending stresses due to moments M1 and M2.

**In a beam only model** - the worst case stress does a good job of calculating the absolute value of the axial stress, bending dir 1, and bending dir 2.

This value is ALWAYS positive for all elements.

Ill give an example:

For element # 300:

Axial Stress = **-500** psi

Bending Stress 1 = **-20,000** psi

Bending Stress 2 = **+2500** psi

Worst Case Stress = |-500| + |-20,000| + 2500 = **23,000 psi**

**In a mixed mesh model** (beam and shell) - I have placed an shell part in the model (this part has no impact on element 300). I am confused. I have worst case stress values that are negative. Even if I have an insignificant shell part in the model, the Worst Case Stress scale is now in the negative region.

For element # 300:

Axial Stress = **-500** psi

Bending Stress 1 = **-20,000** psi

Bending Stress 2 = **+2500** psi

Worst Case Stress = -500 + -20,000 + (-1) * 2500 = -**23,000 psi**

Can someone help with what is going on here?

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I try to reproduse it but I don't get that kind of behavior on PS4.0.

Can you send me your model?