Damage Detection for Truss Structures Using Incomplete Modes

This paper presents a damage detection method for truss structures using incomplete measured modes. The underlying principle of the proposed technique is to add known masses to the physical structure, measure the natural frequencies of this mass-modified system, and then use this set of new data as well as the original test data to identify damages with the help of eigenvalue perturbation method. Regardless of whether the structure is unsymmetrical or symmetrical, the proposed method can precisely identify damages of truss structures only by changes of the first few natural frequencies. The method has the practical attraction of only requiring information about the changes in a few of the eigenvalues between the undamaged and damaged states. A plane truss structure is used as a numerical example to demonstrate the feasibility of the proposed scheme. Results show that the presented method can successfully detect both the location and extent of damage in the truss structure even if the noisy data inevitably make the damage detection more difficult.