Finite Element Model Updating Using Frequency Response Function of Incomplete Strain Data

A method is presented to detect changes in stiffness and mass parameters of a structure using strain data in the frequency domain. Sensitivity of the strain-based frequency response function is characterized as a function of the changes in stiffness, mass, and damping at the element level. The transfer function of a damaged structure is approximated using the measured natural frequencies of the damaged structure and the analytical mode shapes of the intact structure. These approximations result in a set of quasi-linear sensitivity equations. A sensitivity-based algorithm is proposed forfinite elementmodel updating. These sensitivities are used to select themeasured frequency points for model updating and to investigate the weighting of sensitivity equations. The proposed method was successfully applied to a plane truss and a plane frame structure using numerically simulated, error-contaminated strain data. Nomenclatures AS, AM = stiffness and mass connectivity matrices ASe, AMe = nonzero eigenvalues of element stiffness and mass matrices Bi = strain-displacement mapping matrix C = structural damping matrix