I have been working on the unstiffened panel.

It was strange when I found the thickness of the panel which is a part of upper skin under +3g load is designed to have almost the same thickness as that of the corresponding panel of the lower skin under -1.5g load by the panel buckling criteria.( I assume the thickness of the upper panel is twice than that of the lower skin) Both panels have curvatures. Applied load in upper skin panel is definitely larger than that in lower skin panel.

The reason I found is the maximum Y-span length in the buckling tab. These are the data I have.

Upper skin panel:

Nx,Ny,Nxy=-707, -8, -35

X-span=1073, Y-span=340 (126 max), Radius of Y-curvature= 1021

Design results: t=5.64, MS=0.35 by Panel Buckling (Discrete Design Vaule used)

Lower skin panel:

Nx,Ny,Nxy=-358, -6, -3

X-span=1070, Y-span=325 ( 317 max), Radius of Y-curvature= 2560

Design results: t=5.64, MS=0.31 by Panel Buckling (Discrete Design Vaule used)

At this point, my questions are

1) Why and how is the Y-span limited by different max values?

2) Is the buckling load calculated with the max Y-span values?

3) How do I take actions if I would like to evaluate the buckling load with the actual value of Y-span length?

Thanks in advance.