PCA and modal flexibility-based structural novelty detection under temperature variations
LI Miao1,2; REN Wei-xin1,2
1. Department of Civil Engineering, Central South University, Changsha 410075, China; 2. National Engineering Laboratory for High Speed Railway Construction, Central South University, Changsha 410075, China
Abstract：eAbstract: Vibration-based SHM detects damage of structure through changes in vibration features, such as natural frequencies, mode shapes and modal flexibility. Modal parameters are not only affected by damage in structure, but also environmental and operational conditions. Compared to changes in the modal parameters induced by environmental and operational effect, those by local damage in structure could be much smaller. The subtle changes caused by delicate damage in structure may be masked because of such effect. To get real condition of structure, it is highly necessary to eliminate effect of environmental and operational condition on modal parameters. Modal flexibility was chosen as damage parameter for its sensitivity to damage. Via numerical model of simply supported beam, effect of local structure damage and temperature on modal flexibility was analyzed comparatively. After principal component analysis (PCA) being applied to modal flexibility under different conditions, statistical distribution patterns of structure were established on the residual errors of the PCA models. The structure novelty under environmental variations can be diagnosed by recognizing difference between the patterns using method of statistical pattern recognition. It’s demonstrated that false damage diagnosis may occur without considering effect of environmental variations; PCA-based novelty detection ffectively eliminate temperature influences on modal flexibility and provides indication of novelty for structure.
2011, Vol. 30 
