Di Su

Vibration of Reinforced Concrete Viaducts Under High-speed Train Passage: Measurement and Prediction Including Train-Viaduct Interaction

This study investigates the dynamic interactions between high-speed trains and reinforced concrete viaducts using field measurements and numerical simulations. The dynamic responses of a 40 year old viaduct under high-speed train passage are measured. Using general finite-element method software, a new numerical vibration prediction scheme for a train–bridge system is developed. Following the Newmark scheme, a decoupling algorithm is derived through the contact force between a train and viaduct. Track irregularity is also taken into account. The proposed numerical scheme is verified through a comparison between calculated responses and in situ measured responses. This approach is expected to provide not only an accurate simulation tool for train-induced vibration, but also instructive information for the retrofit of railway structures, especially at higher speeds.

A Damage Detection Algorithm Utilizing Dynamic Displacement of Bridge under Moving Vehicle

A damage detection method is proposed, which utilizes dynamic displacement of bridge structures under moving vehicle. The problem is first elaborated with closed-form solution of dynamic displacement, which is decomposed into quasi-static component and dynamic component. Dynamic curvature is defined as second derivative of the dynamic displacement for detecting damage location and estimating damage extent. Damage is modeled by local reduction of stiffness in this paper. Numerical study was conducted on a simply supported beam to verify the proposed method. Vehicle model is analyzed with Newmark’s method using Matlab to obtain the contact force acting on the bridge. Beam model is established in commercial finite element software ABAQUS. The effects of road surface roughness and vehicle-bridge interaction are both considered in the analysis. In order to identify damage location and extent, dynamic curvature was calculated with midspan displacement. Parametric study on measurement noise level, damage location, damage extent, and multiple damage cases is performed, and the analysis results show both reliability and efficacy of this method in damage detection of bridge structures. At last, conclusions are drawn for its application to bridges in engineering practice.

Development of a stereo camera system for road surface assessment

In Japan, large number of road structures which were built in the period of high economic growth, has been deteriorated due to heavy traffic and severe conditions, especially in the metropolitan area. In particular, the poor condition of expansion joints of the bridge caused by the frequent impact from the passing vehicles has significantly influence the vehicle safety. In recent year, stereo vision is a widely researched and implemented monitoring approach in object recognition field. This paper introduces the development of a stereo camera system for road surface assessment. In this study, first the static photos taken by a calibrated stereo camera system are utilized to reconstruct the three-dimensional coordinates of targets in the pavement. Subsequently to align the various coordinates obtained from different view meshes, one modified Iterative Closet Point method is proposed by affording the appropriate initial conditions and image correlation method. Several field tests have been carried out to evaluate the capabilities of this system. After succeeding to align all the measured coordinates, this system can offer not only the accurate information of local deficiency such as the patching, crack or pothole, but also global fluctuation in a long distance range of the road surface.

An interferometric radar for displacement measurement and its application in civil engineering structures

Recent progress in radar techniques and systems has led to the development of a microwave interferometer, potentially suitable for non-contact displacement monitoring of civil engineering structures. This paper describes a new interferometric radar system, named IBIS-S, which is possible to measure the static or dynamic displacement at multiple points of structures simultaneously with high accuracy. In this paper, the technical characteristics and specification of the radar system is described. Subsequently, the actual displacement sensitivity of the equipment is illustrated using the laboratory tests with random motion upon a shake table. Finally the applications of the radar system to the measurement on a cable-stayed bridge and a prestressed concrete bridge are presented and discussed. Results show that the new system is an accurate and effective method to measure displacements of multiple targets of structures. It should be noted that the current system can only measure the vibration of the target position along the sensors line of sight. Hence, proper caution should be taken when designing the sensor posture and prior knowledge of the direction of motion is necessary.

Local Train-Induced Vibration in High-Speed Train Steel Bridge

Because of limited financial resources, it is necessary for the current railway infrastructures to remain sustainable while maintaining reasonable reliability in the future. In this study, the dynamic behavior of train-induced vibrations of a steel bridge is investigated by carrying out numerical analysis, with an emphasis on the local vibration of dynamic interaction between the high-speed train and the bridge. A new numerical vibration prediction scheme for the train-bridge system using commercial software is developed. The analysis results revealed that local vibration at the lower flange had a localized effect on the stresses at the bottom of the vertical stiffener. The vibrations at the lower flange of the main girder accompanied by increased local stresses could cause fatigue damage. This approach is expected to provide not only an accurate simulation tool for predicting train-induced vibration but also instructive information for the sustainability of rail infrastructure