• Journal of Korea Water Resources Association
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• v.39 no.7 s.168
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• pp.583-592
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• 2006

There has been debated on the fact that a scour hole produced by the construction of a groyne has environmental benefits such as provision of diverse underwater habitats and shelter for fish in the event of flooding. Therefore researches are focusing on the scour field around the groyne area beyond the existing safety issues. The scour area on aquatic habitats would format many form on groyne conditions so that the analysis of scour area is strongly required. This study conducted the experiments on permeability and installation angle of groyne and suggested the data for groyne selection in environmental point as analyzing scour area. The physical modeling was performed in different permeability (0%, 20%, 40%, 60%, 80%) and installation angle of groyne ($60^{\circ},\;90^{\circ},\;120^{\circ}$). As the result of the study, scour area and scour depth at maximum scour condition was revealed for each case and suggested the differences according to experiment conditions.

• Journal of Industrial Technology
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• v.29 no.A
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• pp.67-75
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• 2009

In this study, the investigation of hydraulic characteristics and the pier data for the rivers in Youngseo area of Gangwon Province was carried out and the evaluation and comparison between the values from existing formulas and the values from the model tests was conducted, along with the statistical sensitivity analysis of the elements influencing the scour. As a result, the deviation between the values calculated from the existing formulas and the model tests appeared to be 1.09%~63.98% as the piers were getting larger, which indicated that the existing formulas were not appropriate to estimate the scour in the rivers in Gangwon area. And the formula which estimates the scour with the size of the pier only, among the existing ones, was far behind in estimating the sensitivity because of insufficient incorporation of the hydraulic characteristics, though it is convenient to estimate the value. The sensitivity analysis of the value from the model tests and the depth of the scour proved the significant impact on scour by the size of the pier and water depth, indicating 64% and 36%, respectively. In this study, the formula developed through the regression analysis performed based on the values from the model tests, which appeared to be appropriate for the rivers in Gangwon Province, was proposed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5C
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• pp.323-331
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• 2006

It is a recent worldwide trend that erosion characteristics of soil, the resistance factor against scour, are quantified and considered in the estimation of scour depths in fine-grained soils. As part of the efforts, local erosion characteristics on fine-grained soils of the West Coast area are analyzed through scour rate experiments, where a lot of sea-crossing long-span bridges are planned and being constructed in recent years. Four sites including Incheon Bridge, Choji Bridge, Hwankyung Bridge, and Janghang area are finally selected for this study and the scour rate tests are performed using 34 undisturbed soil samples from the sites. The critical shear stresses which represent erodibility of the soil tend to be proportional to the undrained shear strength values. The relative ability of cohesive fine-grained soils to resist erosion is assumed to be higher than that of noncohesive soils. Quantified local erosion characteristics of fine-grained soils in the West Coast area are presented in forms of charts showing relationships between scour rates and shear stresses, and suggested as basic data for the estimation of scour depths and design of bridge foundations in the West Coast area.

• Structural Monitoring and Maintenance
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• v.6 no.2
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• pp.125-145
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• 2019

Bridge scour is one of the predominant causes of bridge failure. Current climate deterioration leads to increase of flooding frequency and severity and thus poses a higher risk of bridge scour failure than before. Recent studies have explored extensively the vibration-based scour monitoring technique by analyzing the structural modal properties before and after damage. However, the state-of-art of this area lacks a systematic approach with sufficient robustness and credibility for practical decision making. This paper attempts to develop a data-driven methodology for bridge scour monitoring using support vector machines. This study extracts features from the bridge dynamic responses based on a generic sensitivity study on the bridge's modal properties and selects the features that are significantly contributive to bridge scour detection. Results indicate that the proposed data-driven method can quantify the bridge scour damage with satisfactory accuracy for most cases. This paper provides an alternative methodology for bridge scour evaluation using the machine learning method. It has the potential to be practically applied for bridge safety assessment in case that scour happens.

• Water Engineering Research
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• v.4 no.2
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• pp.99-109
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• 2003

Since bed elevation changes are mainly dependent on the flow velocity and corresponding shear stress, it is possible to predict bed elevation numerically using velocity components. For the scour analysis due to channel contraction, a bed load transport model is developed and applied to estimate scour depth around coffer dam in the Mississippi River. During Phase I of the Lock & Dam No. 26 replacement project, a coffer dam was constructed to reduce the flow area approximately by 50%. Flow velocity increases due to the flow area reduction yields significant lowering (erosion) of the channel bed elevation. The proposed numerical model solves the sediment continuity equation using the finite element method to evaluate scour process in the vicinity of the coffer dam

• Journal of the Korean Society for Marine Environment & Energy
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• v.20 no.2
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• pp.84-90
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• 2017

In this research, a three-dimensional Computational Fluid Dynamics(CFD), scour characteristics around monopile was grasped and the effect of circular ring type scour protection on reducing protection was assessed. When Torsethaugen(1975) found that the scour area and its depth were coincided quantitatively On the ground of previous findings, after scour was assessed in terms of sea current velocity, we also found that the tendency of maximum scour depth and its width were increased as the sea current velocity was increased. The experiments were performed by attaching ring-circular typed scour protection under the bottom in order to reducing scour around the constructs of monopile type and showed reduced scour approximately by 68.5%. In addition, there were reduction of downward flow and bottom velocities, suggesting that scour protection reduce the effect of downward flow on scour.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.2 s.17
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• pp.29-35
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• 2005

In Korea more than ninety bridges are collapsed every year by flood, which causes the scour of pier foundation. Researches on the quantitative assessment method to assess the integrity of bridge against scour have not been organized systematically in the bridge design practice and maintenance area. In this study, dynamic characteristics assessment experiments are carried out as an emergency inspection method to assess the integrity of the pier foundation for scour after a flood. According to the dynamic characteristics assessment experiment, which simulates foundation scour of the spread footing pier, foundation scour can be evaluated by the first mode natural frequency of the pier.

• Proceedings of the Korea Water Resources Association Conference
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• 2004.05b
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• pp.429-433
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• 2004

According to researchers, the influential factors of scouring are generally divided into three factors: the flow conditions, the type and position of structures, and the characteristics of bed materials. In addition, scouring is affected by the 3-dimensional turbulent boundaries, the unsteady flow, the movement of sediment in the scour-hole area, the approach flow velocity and depth, the width of bridge foundation/pier, and the particle size of bed materials. However, it is difficult to estimate the scour depth near bridge piers when all conditions are factored in at once. Therefore, for reasonably accurate estimates of scour depth, it is essential to consider sufficiently the flow force and resisting force for scour. That is, to determine the shear stress concerning the bed material distribution is needed. In this study, the experiments were performed under the condition of a steady state of flow. As a result, scouring occurred at velocity ratios of 0.476,$(V/V_c=0.476)$, and the scour depth was increased linearly as the velocity ratio increased. in addition, the average values of shear stress ratio at zero scouring depth in both rectangular and circular piers were approximately 7$(\tau_c/\tau_{approach})$ and in the case for same size bed particle material. The results of this study can be used for the fundamental material for estimating the scour depth of bed materials.

• Journal of the Korean Geotechnical Society
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• v.20 no.3
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• pp.67-74
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• 2004

A case study was performed to verify the applicability of existing formulae for predicting bridge scour in cases where its piers are founded in fine-grained soils. The object of study was the Kanghwa Choji Bridge area where the streambed consists of mainly clayey soil. Site investigation included: direct measurement of scour depths around piers using an ultrasonic probe; and collection of undisturbed soil samples which were later used to determine geotechnical properties and scour rate under different stream velocities. Scour depth prediction was made by employing several conventional methods and compared with the measured value. All methods, not taking soil's intrinsic property against erosion into consideration, overestimated scour depth by a factor of 3.6 to 6.5. On the other hand, the SRICOS method yielded a reasonably acceptable overestimation by a factor of 1.7.

• Journal of Korea Water Resources Association
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• v.41 no.8
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• pp.845-854
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• 2008

The old bridge of Woljeong-gyo, which has the fluvial history and culture, represents the ancient construction and civil engineering techniques. It is the oldest stone bridge in Korea and currently restored with its vicinities. In this study, the experimental model was used to analyze the hydraulic characteristics, the local pier-scour depth without scour protection, and the stability of riprap protection using the old grid type panels and stones for Woljeong-gyo of the study area. The water levels were increased around 30cm due to the restored bridge piers and foundations and the effects went up to 200m upstream. The maximum scour depth of 5.4m was measured and the scour protection tests were performed with the riprap size calculated using empirical equations and the existing scour protection range. The riprap of the existing scour protection in the upstream side was broken away, while the riprap of extended scour protection was very stable for the design flood condition of Woljeong-gyo area.