Understanding Buckling Load Predictions in Linear-nonlinear Base Analyses

Why does the load multiplier reduce by 1 in eigenvalue buckling when I turn on the Large Deflection setting in the base structural analysis?

If the base analysis is linear, the total perturbation load multiplied by the buckling load factor represents the ultimate buckling load. The prediction of the buckling load can be written as:

F_buckling = 0 + lamda * F_perturbed

If the base analysis is nonlinear, the ultimate buckling load is the sum of the restart point load and the additional perturbation load:

F_buckling = F_restart +lamda*F_perturbed

By default setting the "Keep Pre-Stress Load-Pattern" property to "Yes" retains the loading pattern from the static structural analysis in the eigenvalue buckling analysis. Therefore, you will find that the load multiplier reduces by 1 when changing the base analysis from linear to nonlinear.