Structural damage detection by changes in natural frequencies

Based on the new conception of natural frequency vector (NFV) and natural frequency vector assurance criterion (NFVAC), a new damage detection method using the natural frequencies as damage feature is described in detail. For a specific structure, a series of damage states can be simulated based on the finite element model of the intact structure. Then, the NFVs of these damaged structures can be calculated and used to build the damage feature database of the structure. At last, the NFVAC, which is defined by the relationship of NFVs in the damage feature database and the NFV measured on the actual structure are used as damage index. An 8-story shear frame model is adopted as an example to verify the feasibility and validity of the proposed method. Both numerical simulations and model experiments for damage detection are performed, the results of damage detection for several damage cases demonstrate that using NFVAC as damage index, the damage location can be identified correctly and the damage extents can be estimated as well.