Abstract
The problem of random vibration response based damage detection for a composite beam under non-measurable environmental and operational variability, presently temperature and tightening torque, is considered via a Functional Model based method. The method is based on proper representation of the healthy structural dynamics under any environmental/operating conditions via a data based Functional Model obtained in the method’s baseline phase and used to define a ‘healthy subspace’. Damage detection is, in the method’s inspection phase, achieved by examining whether or not the current dynamics belongs to the healthy subspace. The experimental results obtained for damage detection on a composite beam indicate excellent detection performance, with correct detection rate of 100% for false alarm rate as small as 1%. The superiority of the proposed method is confirmed via comparisons with a state-of-the-art Principal Component Analysis based method.
Highlights
For many in-service structures the variability in their dynamics due to varying environmental and/or operating conditions, such as temperature, wind, boundary conditions and so on, may be so significant as to ‘mask’ changes due to damage
Vibration based Structural Health Monitoring (SHM), which aims at detecting damage via changes it induces on the dynamics [1], may be subject to poor performance, characterized by low detection rate and/or high false alarm rate
Vibration response signals from Points Y1 and Y2 obtained from a single experiment with the healthy beam under specific values of temperature (12 oC) and tightening torque (1 Nm) are used for the estimation of a conventional ARX model based on standard identification procedures [10, pp. 203-205]
Summary
For many in-service structures the variability in their dynamics due to varying environmental and/or operating conditions, such as temperature, wind, boundary conditions and so on, may be so significant as to ‘mask’ changes due to damage. Vibration based Structural Health Monitoring (SHM), which aims at detecting damage via changes it induces on the dynamics [1], may be subject to poor performance (lack of robustness to the varying conditions), characterized by low detection rate and/or high false alarm rate. The problem of vibration based SHM robustness may be accounted for by attempting separation of the effects of damage from those of varying environmental/operating conditions on the dynamics. In cases where the varying environmental/operating conditions may be continuously measured during the normal operation of the structure, their effects in the dynamics may be counteracted via cause-and-effect type modeling, allowing for their separation from those of damage [2].
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