Structural pounding can cause considerable damage and even lead to collapse of structures. Most research focuses on modeling, parameter investigation, and mitigation approaches. With the development of structural health monitoring, the on-line detection of pounding becomes possible. The detection of pounding can provide useful information of potential damage of structures. This paper proposed using wavelet scalograms of dynamic response to detect pounding and examined the feasibility of this method. Numerical investigations were performed on a pounding system that consisted of a damped single-degree-of-freedom (SDOF) structure and a rigid barrier. Hertz contact model was used to simulate pounding behavior. The responses and pounding forces of the system under harmonic and earthquake excitations were numerically solved. The wavelet scalograms of acceleration responses were used to identify poundings. It was found that the scalograms can indicate the occurrence of pounding and occurrence time very well. The severity of the poundings was also approximately estimated. Experimental studies were carried out, in which shake table tests were conducted on a bridge model that underwent pounding between its different components during ground motion excitation. The wavelet scalograms of the bridge responses indicated pounding occurrence quite well. Hence the conclusions from the numerical studies were verified experimentally. 1. Introduction The different phase vibrations of neighboring buildings or adjacent parts of the same building or bridge can result in pounding under earthquake excitation if the separation distance between them is not sufficient. The pounding can cause considerable damage and even lead to collapse of structures, for example, the bridges with columns of unequal heights [1, 2]. Damage of buildings and bridges due to pounding has been documented in the reports of many earthquakes by researchers. The existed pounding research concentrated on modeling of pounding systems, parameter investigations, and mitigation approaches. Most mathematical pounding modeling methods fall into two categories: (a) stereomechanical impact approach, which is primarily based on impulse-momentum law; (b) contact element approach, a force-based approach. The first approach was used in [3] and other literature. Hertz contact model, a contact element approach, has been extensively used to model impact [4–7]. The numerical study portion of this paper used this model. With the development of structural health monitoring systems in bridges and other civil structures, the
References
[1]
R. Jankowski, K. Wilde, and Y. Fujino, “Pounding of superstructure segments in isolated elevated bridge during earthquakes,” Earthquake Engineering and Structural Dynamics, vol. 27, no. 5, pp. 487–502, 1998.
[2]
M. J. N. Priestley, F. Seible, and G. M. Calvi, Seismic Design and Retrofit of Bridges, John Wiley and Sons, 1996.
[3]
P. K. Malhotra, “Dynamics of seismic pounding at expansion joints of concrete bridges,” Journal of Engineering Mechanics, vol. 124, no. 7, pp. 794–802, 1998.
[4]
C. P. Pantelides and X. Ma, “Linear and nonlinear pounding of structural systems,” Computers and Structures, vol. 66, no. 1, pp. 79–92, 1998.
[5]
R. O. Davis, “Pounding of buildings modelled by an impact oscillator,” Earthquake Engineering and Structural Dynamics, vol. 21, no. 3, pp. 253–274, 1992.
[6]
K. T. Chau and X. X. Wei, “Pounding of structures modelled as non-linear impacts of two oscillators,” Earthquake Engineering and Structural Dynamics, vol. 30, no. 5, pp. 633–651, 2001.
[7]
S. Muthukumar and R. DesRoches, “A Hertz contact model with non-linear damping for pounding simulation,” Earthquake Engineering and Structural Dynamics, vol. 35, no. 7, pp. 811–828, 2006.
[8]
J. S. Walker, A Primer on Wavelets and Their Scientific Applications, Chapman & Hall/CRC, Boca Raton, Fla, USA, 1999.
[9]
Z. K. Peng and F. L. Chu, “Application of the wavelet transform in machine condition monitoring and fault diagnostics: a review with bibliography,” Mechanical Systems and Signal Processing, vol. 18, no. 2, pp. 199–221, 2004.
[10]
K. Gurley and A. Kareem, “Applications of wavelet transforms in earthquake, wind and ocean engineering,” Engineering Structures, vol. 21, no. 2, pp. 149–167, 1999.
[11]
J. G. M. van Mier, A. F. Pruijssers, H. W. Reinhardt, and T. Monnier, “Load-time response of colliding concrete bodies,” Journal of Structural Engineering, vol. 117, no. 2, pp. 354–374, 1991.
[12]
W. Goldsmith, Impact: The Theory and Physical Behaviour of Colliding Solids, Dover Publications, Mineola, 2001.
[13]
J. Lin and L. Qu, “Feature extraction based on morlet wavelet and its application for mechanical fault diagnosis,” Journal of Sound and Vibration, vol. 234, no. 1, pp. 135–148, 2000.
[14]
Y.-T. Sheen and C. K. Hung, “Constructing a wavelet-based envelope function for vibration signal analysis,” Mechanical Systems and Signal Processing, vol. 18, no. 1, pp. 119–126, 2004.
[15]
C. C. Liu and Z. Qiu, “A method based on Morlet wavelet for extracting vibration signal envelope,” in Proceedings of the 5th International Conference on Signal Processing, pp. 337–340, 2000.
[16]
A. Teolis, Computational Signal Processing with Wavelets, Birkh？auser, Boston, Mass, USA, 1st edition, 1998.
[17]
L. A. Wong and J. C. Chen, “Nonlinear and chaotic behavior of structural system investigated by wavelet transform techniques,” International Journal of Non-Linear Mechanics, vol. 36, no. 2, pp. 221–235, 2001.
[18]
S. G. Mallat, A Wavelet Tour of Signal Processing, Academic Press, San Diego, Calif, USA, 2nd edition, 1999.
[19]
Q. Meng, M. Zhang, and G. Zhou, “The study on SMA Pseudo-Rubber Metal damper's control efficiency on aseismic pounding in high-pier bridge in shaking table testing,” Advanced Materials Research, vol. 163–167, pp. 4429–4441, 2011.
