MANIPULATION OF EIGENVALUES OF A STIFFNESS MATRIX FOR AN ELASTO-PLASTIC ANALYSIS INCLUDING INSTABILITY

Abstract

　Eigenvalue manipulation of a stiffness matrix is newly proposed. The method of the eigenvalue manipulation is defined by Equations 2 and 5 for symmetrical and asymmetrical matrix, respectively. This manipulation magnifies the unbalance forces in only directions of eigenvectors with negative eigenvalues, and does not affect in the other directions with positive eigenvalues. In a simple inverted bar model, first order equilibrium leads its results to an unstable balanced path under compression. Additionally, its stable balanced paths are based on a solution of a cubic equation. Analytical results of 3D cantilever column model with 4 elastoplastic springs are very successful.