## Linearised Pre-Buckling Solver

The linearised pre-buckling solver is commonly used in stress analysis of slender or thin-walled structures, it allows for the direct solving of 'buckling' problems around an equilibrium position along the non-linear path. The solver is invoked by the MDL command analysis linearised_prebuckling; this command must be specified in the case block.

Note When executing B2000++, warnings of the following kind WARNING:solver.eigenvalue.arpack:12:36:35.234: Maximum number of iterations taken. All possible eigenvalues (0) have been found. are indicative that the value for the nmodes option should be increased.

## 1. MDL Commands

In addition to the MDL command analysis linearised_prebuckling, the following commands may be specified in the case block.

nmodes v

Number of buckling modes v to be computed (default: 1). It is often necessary to set this option to values of 10 or even 20 for the successful solution of the eigenvalue problem.

shift v

The spectral frequency shift value. The computed buckling modes are the ones whose eigenvalues (load factors) are near this value. The default of 0 selects the nmodes lowest buckling modes.