• 한국방재학회:학술대회논문집
• /
• 2011.02a
• /
• pp.39-39
• /
• 2011

This study presents an effective vision-based system for cable bridge damage detection. In theory, cable bridges need to be inspected the outer as well as the inner part. Starting from August 2010, a new research project supported by Korea Ministry of Land, Transportation Maritime Affairs(MLTM) was initiated focusing on the damage detection of cable system. In this study, only the surface damage detection algorithm based on a vision-based system will be focused on, an overview of the vision-based cable damage detection is given in Fig. 1. Basically, the algorithm combines the image enhancement technique with principal component analysis(PCA) to detect damage on cable surfaces. In more detail, the input image from a camera is processed with image enhancement technique to improve image quality, and then it is projected into PCA sub-space. Finally, the Mahalanobis square distance is used for pattern recognition. The algorithm was verified through laboratory tests on three types of cable surface. The algorithm gave very good results, and the next step of this study is to implement the algorithm for real cable bridges.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2003.09a
• /
• pp.271-279
• /
• 2003

The objective of this study is to evaluate the damage of the reinforced concrete bridge piers. For the purpose of this research, twelve reinforced concrete specimens were fabricated and experimented with quasi-static test method. The selected test parameters are lap splice, axial load ratio, confinement steel ratio and number of loading cycle. The method of evaluate of damage index is the model proposed by Park and Ang. In accordance with this research, the most effective test parameter is lap splice of longitudinal steel. Therefore, the retrofit scheme of reinforced concrete bridge piers with lap splice of longitudinal steel, which was constructed before 1992, must be settled without delay. Otherwise, the effect of axial force is trivial. The more confinement steel is less damage index and more loading cycle lead to raise damage. The damage statement proposed Park and Ang is the same with experimental results.

• Journal of the Korean Society of Safety
• /
• v.36 no.3
• /
• pp.40-49
• /
• 2021

This study surveyed damage to small and medium-sized RC slab bridges, the largest in number in Korea. Four common types of damage were identified, and their static and dynamic structural behaviors were examined through structural analysis. The degree of damage was selected as an analysis parameter for three superstructures of RC slab bridges. After structural analysis, a damage assessment process was proposed that can be used as the basis for establishing maintenance yplans for these bridges. The results of the present study can be used for the safety management of RC slab bridges, classified as bridges suspected of safety flaws or requiring maintenance in load-carrying capacity tests.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.6
• /
• pp.34-41
• /
• 2020

In recent years, magnitude and frequency of earthquakes have increased in Korea. Damage to a bridge, which is one of the main infrastructures, can directly lead to considerable loss of human lives. Therefore, engineers need to evaluate the seismic fragility of the structure and prepare for the possible seismic damage. In particular, the number of aging bridges over 30 years of service increases, and thus the seismic analysis and fragility requires accounting for the aging and retrofit effects on the bridge. In this study, the nonlinear static and dynamic analyses were performed to evaluate the effects of the aging and FRP retrofit on a PSC bridge. The aging and FRP retrofit were applied to piers that dominate the response of the bridge during earthquakes. The maximum displacement of the bridge increased due to the aging of the pier but decreased when FRP retrofit applied to the aged pier. In addition, seismic fragility analysis was performed to evaluate the seismic behavior of the bridge combined with the seismic performance of the pier. Compared with the aged bridge, the FRP retrofit bridge showed a decrease in the seismic fragility in all levels of damage. The reduction of the seismic fragility in the FRP bridge was prominent as the value of PGA and level of damage increased.

• Structural Engineering and Mechanics
• /
• v.70 no.3
• /
• pp.311-324
• /
• 2019

Long-span steel suspension bridges develop significant vibrations under the effect of external time-variable loadings because their slenderness. This causes significant stresses variations that could induce fatigue problems in critical components of the bridge. The research outcome presented in this paper includes a fatigue analysis of a long suspension bridge with 3300 meters central suspended span under wind action and train transit. Special focus is made on the counterintuitive interaction effects between train and wind loads in terms of fatigue damage accumulation in the hanger ropes. In fact the coupling of the two actions is shown to have positive effects for some hangers in terms of damage accumulation. Fatigue damage is evaluated using a linear accumulation model (Palmgren-Miner rule), analyses are carried out in time domain by a three-dimensional non-linear finite element model of the bridge. Rational explanation regarding the above-mentioned counterintuitive behavior is given on the basis of the stress time histories obtained for pertinent hangers under the effects of wind and train as acting separately or simultaneously. The interaction between wind and train traffic loads can be critical for a some hanger ropes therefore interaction phenomena within loads should be considered in the design.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.5
• /
• pp.84-95
• /
• 2019

This paper reports the process of seismic fragility analysis for the rahman-type continuous bridge system. The target structure was the five span highway bridge with maximum pier hight of 72m. OpenSees software was used for the nonlinear time history analysis. In this study, 50 ground motions are considered for nonlinear time history analysis. For each ground motion, PGA was scaled from 0.1g to 2.0g with intervals of 0.1g in order to consider a wide range of the seismic intensity measure. In addition, yield displacement and ultimate displacement of each pier were calculated through section analysis. Based on the result of non linear time history analysis and section analysis, damage condition of target bridge was classified according to the definition of damage condition proposed by Barbat et al. As a result, it was predicted that Extensive Damage occurred at P1 when 0.731 g earthquake occurred in the longitudinal direction. Based on the seismic fragility analysis results, it is found that the probability of occurrence of Extensive Damage in the 4,800 - year period earthquake was about 4.2%. Therefore the target bridge has enough safety for earthquake.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.99-104
• /
• 2002

This paper presents an analytical prediction of the fatigue damage of reinforced concrete bridge columns subjected to cyclic load. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuity in deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The effect of number of load reversals with the same displacement amplitude has been also taken into account to model the reinforcing steel and concrete. The proposed numerical method for fatigue damage of reinforced concrete bridge columns subjected to cyclic load is verified by comparison with reliable experimental results.

• Computational Structural Engineering
• /
• v.6 no.2
• /
• pp.71-78
• /
• 1993

A method to estimate damage of bridge structures is developed using system identification approach. Dynamic behavior of damaged structures is represented by a non-linear hysteretic moment model. Structural properties can be evaluated through system identification. To incorporate variability of the structural properties and uncertainties of structural response, damage is represented as random quantities. Numerical example is shown for the bridge structure under different ground excitation.

• Proceedings of the Earthquake Engineering Society of Korea Conference
• /
• 2001.04a
• /
• pp.329-336
• /
• 2001

This study examines the fragility curves of a bridge by Capacity Spectrum Method. A sample of 10 nominally identical but statistically different bridge and 80 ground-motion time histories are considered to account for the uncertainties related to the structural capacity and ground motion, respectively. The comparison of fragility curves by Capacity Spectrum Method with those by time-history analysis indicates that the agreement is excellent for the state of at least minor damage, but not as good for the state of major damage where nonlinear effects clearly play a crucial role. Overall, however, the agreement is adequate even in the state of major damage considering the large number of typical assumptions under which the analyses of fragility characteristics are performed.

• Interaction and multiscale mechanics
• /
• v.3 no.4
• /
• pp.321-331
• /
• 2010

A new technique is proposed for bridge structural damage detection based on spatial wavelet analysis of the time history obtained from vehicle body moving over the bridge, which is different from traditional detection techniques based on the bridge response. A simply-supported Bernoulli-Euler beam subjected to a moving spring-mass unit is established, with the crack in the beam simulated by modeling the cracked section as a rotational spring connecting two undamaged beam segments, and the equations of motion for the system is derived. By using the transfer matrix method, the natural frequencies and mode shapes of the cracked beam are determined. The responses of the beam and the moving spring-mass unit are obtained by modal decomposition theory. The continuous wavelet transform is calculated on the displacement time histories of the sprung-mass. The case study result shows that the damage location can be accurately determined and the method is effective.