Dynamic damage identification using complex mode shapes. Issue 12 (2nd September 2020)

• Record Type: Journal Article
• Authors: Lofrano, E.; Paolone, A.; Ruta, G.
• Is Part Of: Structural control and health monitoring. Volume 27:Issue 12(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2020-09-02
• Subjects: dynamic identification -- modal complexity -- non‐proportional damping -- perturbation approach -- structural damage identification -- vibration‐based approach; Structural engineering -- Periodicals; Structural control (Engineering) -- Periodicals; Automatic data collection systems -- Periodicals; Detectors -- Periodicals; 624.17
• DOI: 10.1002/stc.2632
• Languages: English
• ISSNs: 1545-2255

Abstract

Summary: Damage, be it a material or a geometric degradation, modifies some features of the response foreseen by the original structural design. These variations, once the dependence on the damage causing them is established, can be used for identification purposes. In the literature, vibration‐based approaches usually compare some responses of linear elastic structures with dissipative properties that are assumed proportional to the mass and stiffness measures. However, such an assumption is reasonable for new, undamaged structures, but can be unreliable in existing, potentially damaged structures, particularly for damages localised in narrow areas. The eigenmodes of a proportionally damped system can be reduced to the real ones of the relevant ideal undamped system. On the other hand, non‐proportional damping exhibits complex eigenmodes that cannot be reduced to those of the ideal, or of the proportionally damped, structure. Thus, we may assume the complexity of the eigenmodes as a measure of non‐proportional damping, hence of damage. On this basis, some contributions in the literature verified the relationship among presence of damage and amount of complexity. Here, we propose a perturbation approach and an objective function able to identify presence, location and amplitude of localised damages, intended as sources of non‐proportionality in viscously damped linear systems. A prototype naturally discrete structure with four degrees‐of‐freedom is chosen to test and show capability and accuracy of the proposed method.