Combined stress for moving load

I want to get clarification on the combined moving load stress to composite section.

As show in attached mode, I checked the max tension stress at element 1314 under moving load case "Cen MV". The combined stress at point 4(-y,-z) is 11.1MPa, however, the individual stresses are 2.99MP for Sax, 0.795MPa for Sby, 5.72MPa for Sbz. All this stress will give sum as 9.505MPa. It's different to the combined stress.

I also extract the critical moving load location as "MVmaxCenMVMy1314" static loadcase. under this loadcase, the combined stress at 4(-y,-z) is 8.3MPa, whick is closer to 9.505MPa.

Could you please advise where I am wrong?

In the bending stress column, the program would show the maximum possible stress component of the section. For Mz in the above section maximum stress would occur at points 1 & 2. Therefore in bending stress column, it shows this stress result. 



Now for the combined stress calculation at points 3 & 4, we can not simply add this stress to the axial stress. The program internally calculates the stress at point 3 & 4 for the Mz component and then calculate the combined stress. I have attached a verification excel sheet for your reference. 

Hope this helps. Kindly let us know if further assistance would be required.

Regards,
Kaushal Mittal
Technical Support Engineer

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In combined stress, there are 3 components, A(axial stress), B (Bending -Y stress), and C (Bending - Z stress. Now to maximize the A+B+C, I have taken three static load case (created using MVL tracer):- (1) Amax & concurrent (2) Bmax & concurrent (3) Cmax & concurrent.