Model updating of the complex modeshapes and the damping matrix

The problem of updating the damping matrix from incomplete modal experiment al data is considered, It is assumed that the mass and stiffness matrices a re accurate, or have been updated before. Hence the suggested model updatin g procedure is restricted to the damping matrix while the normal system and its modal parameters do nor change, The first step is modification of the complex eigenvectors so that they satisfy the governing orthogonality condi tions for damped systems. Using an approximation of these conditions a clos ed form solution is obtained. With the modified eigenvectors, the damping m atrix is updated using the reference basis approach. Two solutions are give n. One for the case of accurate eigendata, and a second, less sensitive to errors, for corrected, yet inaccurate, eigenvectors. The proposed method is demonstrated by means of two examples.