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m ipcdfum-(Bent "2Mode S7brohen-ace0=00399t
Hubert SOectasn- (Bert 13 Node S& broken-ace d* 003379)
Figure 8: Hilbert amplitude spectra of vibration at (a, left) node 37 and (b, right) node 53 of Bent 12
in severe-damage stage with d= 0.003979.
CONCLUDING REMARKS
This study presents the use of HHT to characterize damage of recordings and model-based simulated
data of bridge structures in their intact, minor- and severe-damage stages. It reveals that the HHTbased
characterization is able to identify the local dynamic properties from a limited number of
recordings. In addition, comparison of the HHT analysis of two recordings from damaged and health
structural elements in one condition stage of the structure can tell the signature difference of local
structural members. This eliminates the need of a priori data required in traditional damage diagnosis,
and thus significantly improves the efficiency in data collection. It should be emphasized here that the
above observations are, at this point, qualitative and suggestive, not quantitative and conclusive.
Validation requires further examination of other recordings and model-based simulation.
AKNOWLEGMENTS
The authors 'would like to express their appreciation for the financial supports provided by the
National Science Foundation with Grant No. 0085272 and by the Federal Highway Administration
DTFH61-96-00030. The financial supports are also acknowledged from the strategic research
program in the Hong Kong Polytechnic University (HKPU) and US-PRC Researcher Exchange
Program administered by Multidisciplinary Center for Earthquake Engineering Research, which makes
it possible for the first author to conduct the study in HKPU during the summer of 2001. Thanks are
also extended to Larry Olson who provided the destructive testing data.
REFERENCES
Huang, N.E., S. Zheng, S.R. Long, M.C. Wu, H,H. Shin, Q. Zheng, N-C. Yen, C.C. Tung, and M.H.
Liu (1998a). "The Empirical Mode Decomposition And Hilbert Spectrum For Nonlinear
And Nonstationary Time Series Analysis." Proc. Roy. SocLond., A 454 903-995.
Sanayei, M. and E.M. Santini (1998) "Dynamic bridge substructure evaluation and monitoring
system," Report of subcontract to Tufts University from FEW A Grant to Olson Engineering.