Detecting damage to offshore platform structures using the time-domain data

Abstract

A new method that uses time-domain response data under random loading is proposed for detecting damage to the structural elements of offshore platforms. In our study, a time series model with a fitting order was first constructed using the time-domain of noise data. A sensitivity matrix consisting of the first differential of the autoregressive coefficients of the time series models with respect to the stiffness of structural elements was then obtained based on time-domain response data. Locations and severity of damage may then be estimated by solving the damage vector whose components express the degrees of damage to the structural elements. A unique aspect of this detection method is that it requires acceleration history data from only one or a few sensors. This makes it feasible for a limited array of sensors to obtain sufficient data. The efficiency and reliability of the proposed method was demonstrated by applying it to a simplified offshore platform with damage to one element. Numerical simulations show that the use of a few sensors’ acceleration history data, when compared with recorded levels of noise, is capable of detecting damage efficiently. An increase in the number of sensors helps improve the diagnosis success rate.

Keywords

offshore platform / damage detection / time-domain response / time series analysis / sensitivity analysis / autoregressive coefficient

References

[1] Zong Z. H., Ren W. X., Ruan Y. Recent advances in research on damage diagnosis for civil engineering structures[J]. China Civil Engineering Journal, 2003, 36(5): 105-110

[2] Doebling S. W., Farrar C. R., Prime M. B. A summary review of vibration-based damage identification methods[J]. The Shock and Vibration Digest, 1998, 30(2): 91-105

[3] Mangal L., Idichandy V. G., Ganapathy C. Structural monitoring of offshore platforms using impulse and relaxation response[J]. Ocean Engineering, 2001, 28(6): 689-705

[4] Diao Y. S., Li H. J., Shi X., Wang S. Q. Experiment verification of damage detection for offshore platforms by neural networks[J]. China Ocean Engineering, 2006, 20(3): 351-360

[5] Majumder L., Manohar C. S. A time-domain approach for damage detection in beam structures using vibration data with a moving oscillator as an excitation source[J]. Journal of Sound and Vibration, 2003, 268(4): 699-716

[6] Choi S., Stubbs N. Damage identification in structures using the time-domain response[J]. Journal of Sound and Vibration, 2004, 275(3–5): 577-590

[7] Galvanetto U., Violaris G. Numerical investigation of a new damage detection method based on proper orthogonal decomposition[J]. Mechanical Systems and Signal Processing, 2007, 21(3): 1346-1361

[8] Li D. S., Zhang Z. D., Wang D. Y. Damage detection methods for offshore platforms based on wavelet packet transform[J]. China Ocean Engineering, 2005, 19(4): 701-710

[9] Fugate M. L., Sohn H., Farrar C. R. Vibration-based damage detection using statistical process control[J]. Mechanical Systems and Signal Processing, 2001, 15(4): 707-721

[10] Sohn H., Farrar C. R. Damage diagnosis using time series analysis of vibration signals[J]. Smart Materials and Structures, 2001, 10(3): 446-451

[11] Lu Y., Gao F. A novel time-domain auto-regressive model for structural damage diagnosis[J]. Journal of Sound and Vibration, 2005, 283(3–5): 1031-1049

[12] Sohn H., Worden K., Farrar C. R. Statistical damage classification under changing environmental and operational conditions[J]. Journal of Intelligent Material Systems and Structures, 2003, 13(9): 561-574

[13] Sohn H., Allen D. W., Worden K., Farrar C. R. Structural damage classification using extreme value statistics[J]. Journal of Dynamic Systems, Measurement and Control, 2005, 127(1): 125-132

[14] Nair K. K., Kiremidjian A. S., Law K. H. Time series-based damage detection and localization algorithm with application to the ASCE benchmark structures[J]. Journal of Sound and Vibration, 2006, 291(1–2): 349-368

[15] Yang S. Z., Wu Y. Time series analysis in engineering application[M]. 1992, Wuhan: Huazhong University of Science and Technology Press

[16] Stubbs N. Global non-destructive damage evaluation in solid[J]. International Journal of Analytical and Experimental Modal Analysis, 1990, 5(2): 1-12

[17] Wang D., Haldar A. Element-level system identification with unknown input information[J]. Journal of Engineering and Mechanics, 1994, 120(1): 159-176