HHT-Based Bridge Structural Health-Monitoring Method

Abstract

A new Hilbert-Huang transform (HHT)-based method for nondestructive instrument structure health monitoring is developed. When applied to bridges, this new method depends on a transient test load and simple data collection. The essense of the method is the newly developed HHT for nonstationary and nonlinear time series analysis, which consists of the empirical mode decomposition and Hilbert spectral analysis. The final decision on the health of the bridge structure is based on two criteria. The first criterion detects the nonlinear characteristic of the intra-wave frequency modulations of the bridge response, which usually appears during comparisons of light with heavy loads. The second criterion detects the frequency downshift as an indication of structural yield. This new method enjoys many advantages: no a priori data required, simple data collection, minimum traffic disruption, and precise and nuance quantitative answers. The result of a case study is presented, which establishes the feasibility of this new approach for structural health monitoring. IntroductionWith the inevitable aging of civil infrastructures, structural health monitoring has become an urgent problem worldwide (Chang 1997(Chang , 1999(Chang , 2001. To safeguard the safety performance of a bridge, regular inspections are essential (see, for example, Mori and Ellingwood 1994a,b). At the present time, the inspection method is primarily visual: a technician has t o go through a bridge t o examine each member and certify its safety. This method is subjective and flawed, lacking rigorous and objective standards. For example, for a bridge deteriorating from fatigue or aging, the damage is not clear-cut at any time. Therefore, any call is judgmental. Furthermore, using this method for complicated bridge structures is not feasible: some members might be located at positions too awkward t o access; the members might require too much time t o inspect; and the damage might be too subtle t o be detected visually. Because of these limitations, the visual-inspection results are known to be not totally reliable, yet we are forced to rely on them today.According t o Doebling e t al. (1996, 1998), a n ideal inspection method would have t o satisfy the following conditions:(1) be robust, objective, and reliable, 263 Hilbert-Huang Transform and Its Applications Downloaded from www.worldscientific.com by UNIVERSITY OF QUEENSLAND on 10/04/15. For personal use only.

An investigation into the acceleration response of a damaged beam-type structure to a moving force

“…Others have applied empirical mode decomposition to the acceleration response [24,25]. All these approaches have something in common, the damage is visualised through the appearance of a singularity in a processed signal supposed to be smooth in a healthy case.…”

Identifying damage in a bridge by analysing rotation response to a moving load

“…Some authors use a wavelet transform of beam translation (W. W. Zhang, Wang, & Ma, 2009;Zhu & Law, 2006) or acceleration (Hester & González, 2012) response to a moving vehicle to locate damage in a beam, while other researchers have applied empirical mode decomposition to the acceleration response (Bradley, González, & Hester, 2010;N. E. Huang, Huang, & Chiang, 2005).…”

Structural Health Monitoring Based on Vehicle-Bridge Interaction: Accomplishments and Challenges

“…With the EMD's initial processing, the data can be decomposed into a finite set of intrinsic mode functions (IMFs). Huang et al (2005) proposed two damage features for monitoring the health of the bridge structure subjected to moving vehicles: the nonlinear characteristics from employing the light and heavy loads and the frequency shift. The HHT was also used to extract the damage feature from one measurement on the bridge (Roveri and Carcaterra 2012).…”