Two-step identification approach for damped finite element models

The application of well-established identification procedures in the time domain for finite element (FE) models with a larger number of degrees of freedom (DOF) in general causes quite severe difficulties; i.e., the solution diverges in most cases and the procedures are computationally too demanding. In this paper, a two-step identification approach is presented that is especially suitable for FE models with many DOE The two complementary approaches are a least-square-based method and a special form of the Extended Kalman Filter. Both approaches use modal decomposition as a key for avoiding the initially mentioned problems. To enable the identification of local damping phenomena, nonclassically damped structures are assumed throughout the computational procedures, implying the solution of the complex eigenvalue problem. For this purpose, a subspace iteration is used for solving the eigenvalue problem advantageously.