Yang Deng

Structural Damage Warning of a Long-Span Cable-Stayed Bridge Using Novelty Detection Technique Based on Wavelet Packet Analysis

This paper describes the development of a multi-stage scheme for structural damage warning of the Runyang Cable-stayed Bridge using the measured dynamic responses from an on-line instrumentation system. In the first stage, the wavelet packet energy spectrum (WPES) is extracted using wavelet packet analysis from the measured dynamic responses caused by ambient excitations, thus providing parameters warning of occurrence of structural damage. The second stage is to formulate correlation models describing the seasonal relationship between WPES and temperature and the third stage is to classify the measured changes of WPES, whether due to environmental temperature or to structural damage, using a novelty detection technique based on statistical process control. The usefulness of the approach is examined on the Runyang Cable-stayed Bridge using 236 days of health monitoring data. The results reveal that the seasonal change of environmental temperature accounts for variation in the measured WPES, which averaged a 200% variance, and that the approach is able to eliminate the temperature effects and provides a good capability for detecting the damage-induced 10% variance.

Experimental and Analytical Studies on Static and Dynamic Characteristics of Steel Box Girder for Runyang Cable-Stayed Bridge

In this study, a multi-scale computational model and methodology is presented for a comprehensive simulation of the static and dynamic characteristics of the steel box girder of Runyang Cable-stayed Bridge. The global-scale finite element model uses the shell elements with the equivalent orthotropic materials to simulate the top/bottom plate and its U-shape rib, which leads to accurate modeling of structural properties of the steel box girder in terms of vertical, lateral, torsional and warping stiffness. The local-scale finite element modeling of the girder is essentially a combination of fine finite element sub-models of selected details and the global-scale shell element model of the steel box girder by using the submodeling method. The developed three-dimensional global-scale and local-scale FE models have achieved a good correlation with the field load tests and ambient vibration tests. The static and dynamic characteristics of steel box girder of Runyang Cable-stayed Bridge under vehicle load tests and ambient vibration tests are further discussed.

Variability of WPT-Based Dynamic Identification of a Suspension Bridge under Changing Temperature, Wind and Traffic Conditions

This paper addresses the quantification of environmental variability of wavelet packet energy spectrum (WPES) extracted from the ambient dynamic responses of a suspension bridge using wavelet packet transform (WPT). The daily averaged WPES using multi-sample averaging technique are first obtained to eliminate the inherent randomness arising from the identification algorithm. Then the effect of temperature on the measured WPES is quantified using the seasonal correlation models. The traffic-induced and wind-induced variability are further quantitatively evaluated by establishing the traffic-WPES and wind-WPES correlation models. The analysis results reveal that temperature and inherent randomness are the critical sources causing WPES variability, and the WPES variability caused by wind speed and traffic loadings is negligible compared with temperature and inherent randomness. Considering seasonal correlation models of temperature-WPES can effectively eliminate the temperature effect and inherent randomness, it is suitable for structural damage warning of long-span bridges if future seasonal correlation models deviate from these normal models.

Experimental Research on Structural Damage Alarming of Benchmark Structure Based on Empirical Mode Decomposition

A structural damage alarming method is proposed using empirical mode decomposition. The basic idea of this method is that with respect to the intact model and damaged models, the energy redistribution of the intrinsic mode functions decomposed from the structural response can represent the variation of the structural dynamic characteristics caused by the structural damage. By taking the Benchmark test model as the research object, the structural dynamic responses from the hammer-impact tests are collected then the damage alarming parameters and the damage alarming indices are evaluated. The experimental results reveal that the structural damage alarming indices based on empirical mode decomposition is able to effectively detect the structural initial damage with preferable damage alarming capacity.

Study on Parameters for Identification of Wavelet Packet Energy Spectrum for Structural Damage Alarming

The damage alarming analysis based on wavelet packet energy spectrum is performed with regard to the experimental data of Benchmark steel frame structure and online monitoring data of Runyang Suspension Bridge, on the basis of which the damage alarming effects using various wavelet functions are investigated in detail. Results reveal that the Daubechies wavelet functions and Coiflets wavelet functions are applicable to structural damage alarming.