MODEL UPDATING USING AN INCOMPLETE SET OF EXPERIMENTAL MODES

New approaches are presented that use the measured natural frequencies and mode shapes to update the analytical mass and stiffness matrices of a structure. By adding known masses to the structure and measuring its new modes of vibration, we can utilize this additional information to correct the mass matrix of the system, after which the stiffness matrix can be updated by requiring it to satisfy the generalized eigenvalue problem associated with the structure. Manipulating the unknown system matrices into vector forms, the connectivity information can be easily implemented to preserve the physical configuration of the structure, and to reduce the computational efforts required to correct the system matrices. A comparison is made between the proposed updating schemes introduced in this paper and other updating algorithms found in the literature, and drastic improvements are observed.