Structural damage detection method based on incomplete modal information study

A common requirement of damage detection method based on modal shapes is the necessity to use complete modal data, which, however, is unavoidably that measurements yield only partial mode shapes with respect to the total degrees-of-freedom corresponding to the finite-element model, duo to practical testing limitations. This paper presents a structural damage detection method by first optimizing the measured information. According to degrees'-of-freedom contribution to the ability of localizing the structural damage sites, locations that have little contribution are removed; only a small subset of total degrees-of-freedom of structure is persisted and selected for the sensor placement. After that, the reconstruction and expansion of incomplete damaged modes will be gained when only a. limited amount of measurements of incomplete modal data are available. In order to eliminate influence of modal shapes truncation error, applies practical complete modal space theory that use equivalent high-order modal shapes to replace unmeasured high-order modal shapes. A new model-based method for structural damage detection, which is based on the change of modal strain energy in each element before and after the occurrence of damage, is put forward in the paper. Preliminary estimated damage element stiffness matrices that can be gained when modal shapes are reconstructed will be employed to detect structural damage for a computational procedure. At last, the proposed method in the paper is applied to locate structural damage and furthermore, to determine the damage extent.