Linear and Nonlinear Bucking Load Values

Can I get higher nonlinear buckling than linear buckling?

Typically, a nonlinear buckling case provides a more realistic buckling simulation than a linear buckling case, often predicting a lower buckling load. Nevertheless, opposite behavior can also be found.

Linear buckling analysis predicts the first buckling load of a given structure according to its original geometry. However, the predicted linear buckling load sometimes does not result in the collapse of the structure in reality because:

• the buckling mode is local rather than global
• the geometrical configuration of the structure is such that as the initial buckling shapes start to appear and deform the structure, it becomes stiffer (e.g., a plate with stiffeners), and according to that, the nonlinear buckling load is higher than the linear one

To reproduce nonlinear buckling analysis, several techniques can be applied:

- Use a linear perturbation method.

- Scale eigenvalue mode and perturb the geometry using UPGEOM command.

- If the geometry is unsymmetrical, load the structure until no convergence is achieved (this will buckle the structure).