A Study on Efficacy of Wavelet Transform for Damage Identification in Reinforced Concrete Buildings
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Structural damage and its extent can be detected by vibration-based techniques to avoid failure or to minimize maintenance. Among different damage identification techniques, modal curvature approaches are widely researched and applied one. On the contrary, wavelet transformation (WT) methods are gaining popularity in damage identification of real life buildings because of their suitability for non-stationary signals and non-dependency on baseline data. This paper presents a novel approach utilizing complex continuous wavelet to effectively locate change in physical properties of reinforced concrete (RC) buildings by virtue of variation in frequency and mode shapes due to small change in mass and stiffness.
In this paper, the effect of variation of mass and stiffness of a building on the modal parameters is established analytically using theequation of motion for a multi-degree freedom system under forced vibration condition. A 3-D finite element model was developed for predicting the modal frequencies and mode shapes of the scaled down six storey RC building and the effect of addition of mass on a particular level of structure on the modal parameters was studied. Further, acceleration time histories were recorded with variation in mass on 3rd story of building using wireless tri-axial accelerometers and the time histories were processed to arrive at Curvature Damage Factor and wavelet coefficients for identification of the additional load on the particular floor.
Vibration responses from all floors of RC building in ambient and loaded conditions were analyzed for frequency response spectra (FRS). Mode shapes were drawn for unloaded case and loaded cases. It was observed that the modal frequency of building decreases with the increase in mass at floors. It is observed that CDF approach could detect the change in mass in both numerical and experimental results. However, CDF algorithm could not detect the addition of load in case 1, 2 and 3, i.e. when load was less than 25 kg, i.e. only 2.6% of floor mass (960 kg). The acquired data for the above stated load cases were analyzed using complex Gaussian ‘cgau5’ wavelet in MATLAB toolbox to determine the singularity in the signal in terms of wavelet coefficient modulus. It is observed that the WT approach is able to precisely locate the change in physical parameters of the RC model building. However, it is seen that additional load could not be detected in case where only 9 kg, i.e. 0.93% of the total floor mass, was placed on 3rd floor.
From the research work, it is observed that CDF technique is inefficient in damage detection and always demand prior baseline information, which is usually difficult to obtain in practice. However, the wavelet transform-based approach more accurately detects the location of change without relying on intact state vibration data.
KeywordsWavelet transformation Damage identification Structural health monitoring Reinforced concrete building Signal processing Curvature damage factor
- 1.Koohdaragh M, Lotfollahi-Yaghin MA, Ettefagh MM, Mojtehedi A, Beyghbabaye B (2011) Damage detection in beam-like structure based on wavelet packet. Sci Resa Essays 6(7):1537–1545Google Scholar
- 2.Rytter A (1993) Vibration based inspection of civil engineering structures. Ph.D. dissertation, Department of Building Technology and Structural Engineering, Aalborg University, Denmark, vol R9314, no 44Google Scholar
- 6.Amiri GG, Asadi A (2009) Comparison of different methods of wavelet and wavelet packet transform in processing ground motion records. Int J Civil Eng 7(4):248–257Google Scholar
- 13.Amaravadi V, Rao V, Koval LR, Derriso MM (2011) Structural health monitoring using wavelet transforms. In: Proceedings of SPIE, smart structures and materials 2001: smart structures and integrated systems, vol 4327, pp 258–269Google Scholar
- 15.Jaya Prakash G, Swarnamani S (2008) Damage identification in composite beams using continuous wavelet transform applied to mode shape and strain energy data. Adv Vib Eng 7(2):127–141Google Scholar
- 17.Panigrahi SK, Chakraverty S, Mishra BK (2013) Damage assessment in beam with sparse modal information. Adv Vib Eng 12(4):343–348Google Scholar
- 23.Radzienski M, Krawczuk M (2009) Experimental verification and comparison of mode shape-based damage detection methods. In: 7th International conference on modern practice in stress and vibration analysis. J Phys Conf Ser, vol 181Google Scholar
- 24.Asaee ZS, Anvar SA, Sherafat Z (2011) Comparison of modal parameters of multi-story buildings obtained by different wavelet functions. In: Proceedings of IOMAC11-4th international operational modal analysis conferenceGoogle Scholar
- 29.Buyukozturk O, Yu T (2003) Structural health monitoring and seismic impact assessment. In: Proceedings of fifth national conference on earthquake engineering, Istanbul, Turkey, 26–30 May 2003Google Scholar
- 32.Harry HG, Gajanan MS (1999) Structural modeling and experimental techniques, 2nd edn. CRC Press, Washington, DCGoogle Scholar
- 33.Kanwar VS, Kwatra N, Aggarwal P, Gambir ML (2008) Health monitoring of RCC building model experimentally and its analytical validation. Eng Comput Int J Comput Aided Eng Softw 25(7):677–693Google Scholar