A no spill-over updating method for undamped structural systems

A new numerical method for simultaneously updating mass and stiffness matrices based on incomplete modal measured data is presented. By using the Kronecker product, all the variables that are to be modified can be found out and then can be updated directly. The optimal approximation mass and stiffness matrices which satisfy the required eigenvalue equation are found under the Frobenius norm sense. The large number of unmeasured and unknown eigeninformation and the physical connectivity of the original model are preserved and the updated model will exactly reproduce the modal measured data. The method is computationally efficient as neither iteration nor eigenanalysis is required. The numerical results show that the method proposed is reliable and attractive.