Keywords: strain energy based damage index, false alarms, nodal points, damage localization, damage quantification.

Vibration based damage identification techniques (VBDIT) have progressed in recent years in the field of structural health monitoring (SHM) due to advances in computer and sensor technology. Among the VBDITs, the strain energy based method has been identified as one which has a good potential for damage detection and localization [1]. Different strain energy based damage indices are presented in the literature by Stubbs et al. [2,3], Cornwell et al. [4], Park et al. [5], Jiachun et al. [6] and Shih et al. [7]. However, these damage indices may indicate false alarms or may not detect damage at or near the nodal point if individual modes are used. Further, the existing strain energy based damage indices have a lower potential to quantify the damage [1].

In this paper a new modal strain energy based damage index is proposed by introducing a correction function to reduce the false alarms. Application of this damage index is illustrated for simply supported and continuous beam structures under single and multiple damage scenarios. Results indicate that the proposed damage index has the potential to minimise false alarms, detect damage at or near the nodal points and in most cases quantify the damage using individual modes. Compared to existing strain energy based damage indices, the proposed damage index therefore enhances the reliability of the damage assessment process with individual modes. This may result in the saving of calculation time, cost and data storage requirements.

1

A. Alvandi, C. Cremona, "Assessment of vibration-based damage identification techniques", Journal of Sound and Vibration, 292, 179-202, 2005. doi:10.1016/j.jsv.2005.07.036

2

N. Stubbs, J.T. Kim, K. Topole, "An efficient and robust algorithm for damage localization in offshore platroms", in "Proceedings ASCE 10th Structures Congress", 543-546, 1992.

3

N. Stubbs, J.T. Kim, C.R. Farrar, "Field verification of a non-destructive damage localization and severity estimation algorithm", in "Proceedings of 13th International Modal Analysis Conference", 210-218, 1995.

4

P. Cornwall, S.W. Doebling, C.R. Farrar, "Application of the strain energy damage detection method to plate-like structures", Journal of Sound and Vibration, 224(2), 359-374, 1999. doi:10.1006/jsvi.1999.2163

5

S. Park, Y.B. Kim, N. Stubbs, "Nondestructive damage detection in large structures via vibration monitoring", Electronic Journal of Structural Engineering, 2, 59-75, 2002.

6

J. Li, F. C. Choi, B. Samali, K. Crews, "Damage localization and severity evaluation of a beam-like timber structure based on modal strain energy and flexibility approaches", Journal of Building Appraisal, 2(4), 323-334, 2007. doi:10.1057/palgrave.jba.2950059

7

H.W. Shih, D.P. Thambiratnam, T.H.T. Chan, "Vibration based structural damage detection in flexural members using multi-criteria approach", Journal of Sound and Vibration, 323, 645-661, 2009. doi:10.1016/j.jsv.2009.01.019

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