Youliang Ding

A Study on the WPT-based Structural Damage Alarming of the ASCE Benchmark Experiments

A workable realization procedure for damage alarming of frame structures is put forward based on energy variations of structural dynamic responses decomposed using wavelet packet transform in the paper. The WPT-based method consists of two steps: 1) calculation of the wavelet packet energy spectrum from the measured structural dynamic responses; 2) extraction of the damage alarming index ERVD from the wavelet packet energy spectrum, which is sensitive to structural local damage and insensitive to measurement noise. The ASCE benchmark experiments demonstrate the practicability of the damage alarming method for fame structures, which reveal that the WPT-based damage alarming index ERVD is a good candidate index that is sensitive to structural local damage affected by the actual measurement noise. Also, the experimental results reveal that the lower decomposition level and dominant frequency bands are sufficient for the detection of the damage occurrence using the index ERVD, which makes the proposed damage alarming procedure practical.

Multi-scale Damage Analysis for a Steel Box Girder of a Long-span Cable-stayed Bridge

Accurate evaluation of the effect of possible damage in critical components on the dynamic characteristics of a structure is of critical importance in developing a robust structural damage identification scheme for a long-span cable-stayed bridge. The strategies of finite element (FE) modelling of a long-span cable-stayed bridge for multi-scale numerical analysis are first investigated. A multi-scale model of the Runyang cable-stayed bridge is then developed, which is essentially a multi-scale combination of a FE model for modal analysis of the entire bridge structure and FE sub-models for local stress analysis of the selected locations with respect to the substructuring method. The developed three-dimensional global-scale and local-scale FE models of Runyang cable-stayed bridge achieve a good correlation with the measured dynamic properties identified from field ambient vibration tests and stress distributions of a steel box girder measured from vehicle loading tests, on the basis of which the effectiveness of some damage location identification methods, including a modal curvature index, a modal strain energy index and a modal flexibility index, are evaluated. The analysis results show that the effect of the simulated damage in various components of the steel box girder on the dynamic characteristics of a long-span cable-stayed bridge should be properly considered in structural damage analyses using multi-scale numerical computation.

Finite Element Model Updating for the Runyang Cable-Stayed Bridge Tower Using Ambient Vibration Test Results

The finite element (FE) model updating method aims to fit the parameters of a given initial analytical model in such a way that the model behavior corresponds as closely as possible to the measured behavior. However, the success of applications of the method depends on the analytical conceptualization of complex civil engineering structures, a well-designed and controlled modal test and an integration of analytical and experimental arts. This paper presents a sensitivity-analysis-based FE model updating procedure for FE model updating of Runyang Cable-stayed Bridge tower based on ambient vibration measurements. The updated model results correlate well with the experimental data in both the active frequency range and the passive frequency range. Extensive comparisons are made among the results obtained from different model updating cases. It is found that the appropriate initial FE model and determination of updating parameters are very important for the FE model updating of Runyang Cable-stayed Bridge tower.

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.

Long-Term Structural Health Monitoring System for a High-Speed Railway Bridge Structure

Nanjing Dashengguan Bridge, which serves as the shared corridor crossing Yangtze River for both Beijing-Shanghai high-speed railway and Shanghai-Wuhan-Chengdu railway, is the first 6-track high-speed railway bridge with the longest span throughout the world. In order to ensure safety and detect the performance deterioration during the long-time service of the bridge, a Structural Health Monitoring (SHM) system has been implemented on this bridge by the application of modern techniques in sensing, testing, computing, and network communication. The SHM system includes various sensors as well as corresponding data acquisition and transmission equipment for automatic data collection. Furthermore, an evaluation system of structural safety has been developed for the real-time condition assessment of this bridge. The mathematical correlation models describing the overall structural behavior of the bridge can be obtained with the support of the health monitoring system, which includes cross-correlation models for accelerations, correlation models between temperature and static strains of steel truss arch, and correlation models between temperature and longitudinal displacements of piers. Some evaluation results using the mean value control chart based on mathematical correlation models are presented in this paper to show the effectiveness of this SHM system in detecting the bridges abnormal behaviors under the varying environmental conditions such as high-speed trains and environmental temperature.

Assessing Static Performance of the Dashengguan Yangtze Bridge by Monitoring the Correlation between Temperature Field and Its Static Strains

Taking advantage of the structural health monitoring system installed on the steel truss arch girder of Dashengguan Yangtze Bridge, the temperature field data and static strain data are collected and analyzed for the static performance assessment of the bridge. Through analysis, it is found that the static strain changes are mainly caused by temperature field (temperature and temperature difference) and train. After the train-induced static strains are removed, the correlation between the remaining static strains and the temperature field shows apparent linear characteristics, which can be mathematically modeled for the description of static performance. Therefore, multivariate linear regression function combined with principal component analysis is introduced to mathematically model the correlation. Furthermore, the residual static strains of mathematical model are adopted as assessment indicator and three kinds of degradation regulations of static performance are obtained after simulation of the residual static strains. Finally, it is concluded that the static performance of Dashengguan Yangtze Bridge was in a good condition during that period.

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.

Early-Warning Method of Train Running Safety of a High-Speed Railway Bridge Based on Transverse Vibration Monitoring

Making use of long-term transverse vibration monitoring data of DaShengGuan Bridge, the early-warning method of train running safety of the high-speed railway bridge is established by adopting principal component analysis (PCA) method. Firstly, the root mean square (RMS) of the transverse acceleration of the main girder is used as the monitoring parameter for the train running safety. The correlation model between the RMS values measured from different positions is further adopted as the evaluating model for the train running safety. Finally, the effects of the environmental changes on the evaluating model are eliminated using the PCA method and the warning index for the train running safety is further constructed. The analysis results show that the correlation between the RMS values of the accelerations from different measuring positions on the main girder can be analyzed by a quadratic polynomial fitting model. The PCA method can effectively remove the environmental effects on the quadratic polynomial fitting model. The proposed warning method provides a good capability for detecting the abnormal changes of the measured transverse accelerations and hence it is suitable for early-warning of the train running safety.

Vibration Test and Analysis of An Aircraft Maintenance Hangar under Multi-Support Excitations:

Vibration tests on an AMECO (Aircraft Maintenance Engineering Company) maintenance hangar were performed as multi-support excitations in order to verify the effectiveness of the multi-support time history method. The excitation sources represented the three cases of aeroplane taking-off, aeroplane landing and the running in the hangar of the aeroplane engine. Acceleration sensors were installed on the column bases of the hangar structure in order to collect the ground motion records for various excitation cases. The structural dynamic responses were obtained when subjected to the collected ground motions via the multi-support time history method. The calculation results were generally in agreement with those of the test in both the time domain (acceleration peaks) and the frequency domain, which verify the effectiveness of the multi-support time history method. The vibration test can also provide valuable reference data for long-span space structures under multi-support excitations.

Investigations on serviceability control of long-span structures under human-induced excitation

The increasing strength of new structural materials and the span of new structures, accompanied by aesthetic requirements for greater slenderness, are resulting in more applications of long-span structures. In this paper, serviceability control technology and its design theory are studied. First, a novel tuned mass damper (TMD) with controllable stiffness is developed. Second, methods for modeling human-induced loads are proposed, including standing up, walking, jumping and running, and an analysis method for long-span floor response is proposed based on a finite element model. Third, a design method for long-span floors installed with a multiple TMD (MTMD) system considering human comfort is introduced, largely based on a study of existing literature. Finally, a design, analysis and field test is conducted using several large scale buildings in China including the Beijing Olympic Park National Conference Center, Changsha New Railway Station and the Xi’an Northern Railway Station. The analytical and field test results show that the MTMD system designed using the proposed method is capable of effectively mitigating the vertical vibration of long-span floor structures. The study presented in this paper provides an important reference for the analysis of vibration serviceability of similar long-span floors and design of control system for these structures.