It is well known that many real systems have nonsymmetric mass, damping and stiffness matrices. In this case, the method for calculating eigenpair sensitivity is different from that of symmetric system.
To determine the derivatives of the eigenpairs in nonsymmetric damped case, a modal method was recently developed by Adhikari. The results are derived in terms of the eigenvalues and eigenvectors of the second-order system. Therefore Adhikari's modal method need all eigenvalues and eigenvectors for accurate results. But when a dynamic system has many degrees of freedom, only a few lower modes are available, and because the higher modes should be truncated to use the modal method, the errors may become significant. In this paper a procedure for determining the sensitivities of the eigenpairs of nonsymmetric damped system using a few lowest set of modes is proposed. Numerical examples show that proposed method achieves better calculating efficiency and highly accurate results when a few modes are used.
