Nonlinear eigenvalue analysis for spectral element method

Spectral element method (SEM) is a robust and efficient mathematical technique for dynamic analysis of structures in frequency domain. Unlike finite element method (FEM), in SEM, the dynamic stiffness matrix forms a nonlinear eigenvalue problem (NLEP) to compute the natural frequencies and vibration modes of the structure which cannot be solved using linear numerical eigen-solvers. In this paper, two distinct numerical methods, i.e. (1) a root finding method of rational polynomial functions and (2) a linearization of Lagrange matrix interpolating polynomials, have been used to compute the eigenvalues of a problem more efficiently employing SEM. These proposed methods can solve NLEP in a stable, efficient and accurate way even in the presence of singularities. The accuracy of these methods are numerically evaluated by comparing with the solutions from the modal analysis using FEM.