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CONTENTS
Volume 13, Number 5, May 2014
 

Abstract
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Key Words
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Address
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Abstract
In this study, an indirect approach is developed for assessing the state of a bridge on the basis of mode shapes estimated by the responses of passing vehicles. Two types of damages, i.e., immobilization of a support and decrease in beam stiffness at the center, are evaluated with varying degrees of road roughness and measurement noise. The assessment theory\'s feasibility is verified through numerical simulations of interactive vibration between a two-dimensional beam and passing vehicles modeled simply as sprung mass. It is determined that the damage state can be recognized by the estimated mode shapes when the beam incurs severe damage, such as immobilization of rotational support, and the responses contain no noise. However, the developed theory has low robustness against noise. Therefore, numerous measurements are needed for damage identification when the measurement is contaminated with noise.

Key Words
damage identification; bridge vibration; mode shape; bridge; vehicle interaction

Address
Yoshinobu Oshima and Kunitomo Sugiura: Graduate School of Engineering, Kyoto University, Kyoto, 604-8530, Japan
Kyosuke Yamamoto: Graduate School of Systems and Information Engineering, University of Tsukuba, Tsukuba, Japan

Abstract
The natural frequency of a bridge is an important parameter in many engineering applications such as bridge seismic design and modal-based bridge health monitoring. The natural frequency of a bridge vibrating alone may differ from that vibrating along with a vehicle. Although such vehicle-induced variability in bridge frequency is revealed in several experimental and numerical simulation studies, few attempts have been made on the theoretical escriptions. In this study, both theoretically and experimentally, the variability in the bridge frequency induced by a parked vehicle is verified, and is therefore suggested to be considered in bridge-related engineering, especially for those cases with near vehicle-bridge resonance conditions or with large vehicle-to-bridge mass ratios. Moreover, the variability ranges could be estimated by an analytical formula presented herein.

Key Words
bridge engineering; bridge frequency; vehicle-bridge interaction (VBI); vibration-based health monitoring

Address
K.C. Chang, C.W. Kimand Sudanna Borjigin: Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto 615-8540, Japan

Abstract
This study presents a vibration-based health monitoring strategy for short span bridges utilizing an inspection vehicle. How to screen the health condition of short span bridges in terms of a drive-by bridge inspection is described. Feasibility of the drive-by bridge inspection is investigated through a scaled laboratory moving vehicle experiment. The feasibility of using an instrumented vehicle to detect the natural frequency and changes in structural damping of a model bridge was observed. Observations also demonstrated the possibility of diagnosis of bridges by comparing patterns of identified bridge dynamic parameters through periodical monitoring. It was confirmed that the moving vehicle method identifies the damage location and severity well.

Key Words
bridge engineering; bridge frequency; vehicle-bridge interaction (VBI); vibration-based health monitoring

Address
C.W. Kim, R. Isemoto and P.J. McGetrick : Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto 615-8540, Japan
M. Kawatani :Department of Civil Engineering, Kobe University, Kobe, Japan
E.J. OBrien: School of Civil, Structural & Environmental Engineering, University College Dublin, Newstead, Belfield, Dublin4, Ireland

Abstract
This paper presents a theoretical algorithm for constructing the mode shapes of a bridge from the dynamic responses of a test vehicle moving over the bridge. In comparison with those approaches that utilize a limited number of sensors deployed on the bridge, the present approach can offer much more spatial information, as well as higher resolution in mode shapes, since the test vehicle can receive the vibration characteristics of each point during its passage on the bridge. Basically only one or few sensors are required to be installed on the test vehicle. Factors that affect the accuracy of the present approach for constructing the bridge mode shapes are studied, including the vehicle speed, random traffic, and road surface roughness. Through numerical simulations, the present approach is verified to be feasible under the condition of constant and low vehicle speeds.

Key Words
mode shape identification; test vehicle; instantaneous amplitude; vehicle-bridge interaction

Address
Y.B. Yang and Y.C. Li: Department of Civil Engineering, National Taiwan University, Taipei, Taiwan 10617
K.C. Chang: Department of Civil and Earth Resources Engineering, Kyoto University, Kyoto 606-8501, Japan

Abstract
This paper presents a novel method to carry out monitoring of transport infrastructure such as pavements and bridges through the analysis of vehicle accelerations. An algorithm is developed for the identification of dynamic vehicle-bridge interaction forces using the vehicle response. Moving force identification theory is applied to a vehicle model in order to identify these dynamic forces between the vehicle and the road and/or bridge. A coupled half-car vehicle-bridge interaction model is used in theoretical simulations to test the effectiveness of the approach in identifying the forces. The potential of the method to identify the global bending stiffness of the bridge and to predict the pavement roughness is presented. The method is tested for a range of bridge spans using theoretical simulations and the influences of road roughness and signal noise on the accuracy of the results are investigated.

Key Words
acceleration; bridge; global stiffness; inverse dynamics; road profiles; vehicle-bridge interaction; vehicle forces

Address
E.J. OBrien and A. González: School of Civil, Structural and Environmental Engineering, University College Dublin, Newstead, Belfield, Dublin 4, Ireland
P.J. McGetrick: SPACE, David Keir Building, Queen\'s University Belfast, BT9 5AG, UK

Abstract
An indirect approach is explored for structural health bridge monitoring allowing for wide, yet cost-effective, bridge stock coverage. The detection capability of the approach is tested in a laboratory setting for three different reversible proxy types of damage scenarios: changes in the support conditions (rotational restraint), additional damping, and an added mass at the midspan. A set of frequency features is used in conjunction with a support vector machine classifier on data measured from a passing vehicle at the wheel and suspension levels, and directly from the bridge structure for comparison. For each type of damage, four levels of severity were explored. The results show that for each damage type, the classification accuracy based on data measured from the passing vehicle is, on average, as good as or better than the classification accuracy based on data measured from the bridge. Classification accuracy showed a steady trend for low (1-1.75 m/s) and high vehicle speeds (2-2.75 m/s), with a decrease of about 7% for the latter. These results show promise towards a highly mobile structural health bridge monitoring system for wide and cost-effective bridge stock coverage.

Key Words
indirect SHM; laboratory experiment; damage detection; classification

Address
Fernando Cerda : Universidad de Concepción, Concepción, Chile
Siheng Chen: Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
Jacobo Bielak and James H. Garrett: Department of Civil and Environmental Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA
Piervincenzo Rizzo: Department of Civil and Environmental Engineering, University of Pittsburgh, PA 15261, USA
Jelena Kovačević: Department of Electrical and Computer Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA;
Department of Biomedical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213, USA

Abstract
In this study, a damage detection approach using train-induced vibration response of the bridge is proposed, utilizing only direct structural analysis by means of introducing soft computing methods. In this approach, the possible damage patterns of the bridge are assumed according to theoretical and empirical considerations at first. Then, the running train-induced dynamic response of the bridge under a certain damage pattern is calculated employing a developed train-bridge interaction analysis program. When the calculated result is most identical to the recorded response, this damage pattern will be the solution. However, owing to the huge number of possible damage patterns, it is extremely time-consuming to calculate the bridge responses of all the cases and thus difficult to identify the exact solution quickly. Therefore, the soft computing methods are introduced to quickly solve the problem in this approach. The basic concept and process of the proposed approach are presented in this paper, and its feasibility is numerically investigated using two different train models and a simple girder bridge model.

Key Words
damage detection; bridge diagnosis; train-bridge interaction; soft computing; health monitoring

Address
Xingwen He and Toshiro Hayashikawa: Faculty of Engineering, Hokkaido University, Sapporo 060-8628, Japan
Mitsuo Kawatani and Chul-Woo Kim : Graduate School of Engineering, Kobe University, Kobe 657-8501, Japan
F. Necati Catbas: Department of Civil, Environ. and Constr. Eng., University of Central Florida, Orlando, FL 32816-2450, USA
Hitoshi Furuta : Faculty of Informatics, Kansai University, Osaka 569-1095, Japan


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