FINITE-ELEMENT GEOMETRIC STIFFNESS MATRIX LUMPING BYNUMERICAL INTEGRATION FOR STABILITY ANALYSIS

摘要

Using numerical integration in the formulation of the finite-element geometric stiffness matrix and placing movablernnodes at integration points causes the geometric stiffness matrix to become lumped or diagonal. The consistent geometricrnstiffness matrix which is a non-diagonal matrix, is normally used in the finite-element eigenvalue buckling problem. Alteringrnthe method to deliver a diagonal (lumped) geometric stiffness matrix simplifies the process of solving the eigenvalue problemrnand results in computational savings. The advantage of the diagonal geometric stiffness matrix, also called the lumped forcernstiffness matrix, is that it usually provides lower buckling loads than the magnitude of the true buckling load. As an examplernof the method, the lumped force stiffness matrix formulation using the numerical integration is presented for the beam, shell,rnand rectangular plate elements.