• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.519-528
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• 2006

In the construction of hydraulic structures deciding a design flood is one of the most important works. It should be especially noted that the time distribution of the design rainfall method makes a significant effect on the results of the design flood. Thus, choosing an appropriate time distribution method for the design rainfall is a very important process. In recent years, Huff's method is usually used in Korea. This method presents dimensionless rainfall-time cumulative curves, which are made through the analyses of storm data. In this study, the annual maximum rainfall data, from 1961 to 2004 were analyzed to make the dimensionless rainfall-time cumulative curves and hyetographs in Seoul. The results were compared with the "Regional Time Distribution of the Design Rainfall", (KICT, 1989 and MCT, 2000). As a result, the dimensionless rainfall-time cumulative curves are smoother than Huff's results when the duration of an annual maximum rainfall is short. In addition, the curves are similar with the Huff's results as the duration is longer.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.379-387
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• 2006

An urban inundation model coupling an one-dimensional stormwater model, SWMM(Storm Water Management Model), and a two-dimensional inundation model was developed to simulate inundation caused by the surcharge of storm sewers in urban areas. The limitation of this model which can not simulate the interaction between drainage systems and surcharged flow was resolved by developing Dual-Drainage inundation analysis model which was based upon hydraulic flow routing procedures for surface flow and pipe flow. The Dual-Drainage inundation analysis model can simulate the effect of complex storm drainage system. The developed model was applied to Dorim, catchment. The computed inundated depth and area have good agreement with the observed data during the flood events. The developed model can help the decision support system of flood control authority for redesigning and constructing flood prevention structures and making the potential inundation zone, and establishing flood-mitigation measures.

• Journal of the Korean Geotechnical Society
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• v.39 no.10
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• pp.27-39
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• 2023

To effectively manage flood risk, it is crucial to assess the stability of flood defense structures like levees under extreme flood conditions. This study focuses on the time-dependent probabilistic assessment of embankment slope stability when subjected to rapid water level drops. We integrate seepage analysis results from finite element analysis with slope stability analysis and employ Monte Carlo simulations to investigate the time-dependent behavior of the slope during rapid drawdown. The resulting probability of failure is used to develop fragility curves for the levee slope. Notably, the probability of slope failure remains low up to a specific water level, sharply increasing beyond that threshold. Furthermore, the fragility curves are strongly influenced by the rate of drawdown, which is determined through hydraulic analysis based on flood scenarios. Climate change has a significant impact on the stability of the water-side slope of the embankment due to water level fluctuations.

• Journal of Korean Society of Disaster and Security
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• v.16 no.2
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• pp.65-73
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• 2023

Fishways are essential structures that must be installed in rivers to facilitate the movement of fish between upstream and downstream areas. However, the efficiency of fish passage varies depending on the flow conditions within the fishway. Therefore, this study examined the fish-friendly flow characteristics within a stepped fishway at different overflow depths using FLOW-3D, and conducted experiments for model validation. The key parameters affecting fish swimming ability include velocity, turbulent kinetic energy, and energy dissipation rate. These factors were assessed using a simulated fish species, the zacco platypus, to evaluate the suitability of fish-friendly flow condition. It was confirmed that overflow depth significantly influences fish behavior, and an appropriate overflow depth is required for stepped fishway design. The results of this study are expected to serve as fundamental data for the design of stepped fishways in the future.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.1-8
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• 2023

Marine and hydraulic structures are subject to durability damage not only due to the penetration of sea water but also due to the attachment of marine organisms. Therefore, in this study, we tried to develop an antifouling coating agent with self-cleaning function for marine concrete. It was confirmed that the antifouling coating agent mixed with AKD, cellulose nanofibers and BADGE had sufficient antifouling performance at a well hydrophobicity of around 140° in contact angle and an inclination angle of 15°. In the abrasion resistance test of the surface, only a maximum loss of 0.015 g occurred. In the durability test, as a result of the chloride ion permeation test, almost no chloride ion permeation occurred in the variable where the coating agent was applied, and carbonation and freeze-thaw damage also rarely occurred, so it was analyzed that it was effective in securing durability of concrete.

• Smart Structures and Systems
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• v.33 no.1
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• pp.1-16
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• 2024

The investigation on vehicle-bridge coupling system (VBCS) is crucial in bridge design, bridge condition evaluation, and vehicle overload control. A real-time hybrid testing (RTHT) method for VBCS (RTHT-VBCS) is proposed in this paper for accurately and economically disclosing the dynamic performance of VBCSs. In the proposed method, one of the carriages is chosen as the experimental substructure loaded by servo-hydraulic actuator loading system in the laboratory, and the remaining carriages as well as the bridge structure are chosen as the numerical substructure numerically simulated in one computer. The numerical substructure and the experimental substructure are synchronized at their coupling points in terms of force equilibrium and deformation compatibility. Compared to the traditional iteration experimental method and the numerical simulation method, the proposed RTHT-VBCS method could not only obtain the dynamic response of VBCS, but also economically analyze various working conditions. Firstly, the theory of RTHT-VBCS is proposed. Secondly, numerical models of VBCS for RTHT method are presented. Finally, the feasibility and accuracy of the RTHT-VBCS are preliminarily validated by real-time hybrid simulations (RTHSs). It is shown that, the proposed RTHT-VBCS is feasible and shows great advantages over the traditional methods, and the proposed models can effectively represent the VBCS for RTHT method in terms of the force equilibrium and deformation compatibility at the coupling point. It is shown that the results of the single-degree-of-freedom model and the train vehicle model are match well with the referenced results. The RTHS results preliminarily prove the effectiveness and accuracy of the proposed RTHT-VBCS.

• Structural Monitoring and Maintenance
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• v.10 no.4
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• pp.315-337
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• 2023

During the design phase, it is crucial to determine the interface stresses between the reinforcing plate and the concrete base in order to predict plate end separation failures. In this work, a simple theoretical study of interface shear stresses in beams reinforced with P-FGM and E-FGM plates subjected to an arbitrarily positioned point load, or two symmetrical point loads, was presented using the linear elastic theory. The presence of pores in the reinforcing plate distributed in several forms was also taken into account. For this purpose, we analyze the effects of porosity and its distribution shape on the interracial normal and shear stresses of an FGM beam reinforced with an FRP plate under different types of load. Comparisons of the proposed model with existing analytical solutions in the literature confirm the feasibility and accuracy of this new approach. The influence of different parameters on the interfacial behavior of reinforced concrete beams reinforced with functionally graded porous plates is further examined in this parametric study using the proposed model. From the results obtained in this study, we can say that interface stress is significantly affected by several factors, including the pores present in the reinforcing plate and their distribution shape. Additionally, we can conclude from this study that reinforcement systems with composite plates are very effective in improving the flexural response of reinforced RC beams.

• Tunnel and Underground Space
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• v.13 no.5
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• pp.362-372
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• 2003

Since the occurrence of Portland cement, a great number of concrete structures were constructed. But the concrete structures have their own life times, which inevitably demand repairing treatments, especially on their surface parts. Currently many various methods have been developed and are being applied fer this purpose. In this study, a newly developed method using pneumatic chipping machine and anchor pin was adopted far repair of old concrete structure and the mechanical characteristics of cementing plane between existing and new concrete were tested. Comparing the removal methods for the decrepit part of existing concrete using pneumatic chipping machine and hydraulic breaker, the peak cohesion was higher when using chipping machine at the cementing plane. On the other hand, the residual cohesion was higher for the case of breaker. Step shaped chipping on the cementing plane was effective in increasing peak cohesion, which results 14% increase in the case of 30 mm step height and 22% in 50 mm height when compared with planar chipping plane. The use of anchor pin increased the residual cohesion, which restricted shear slip on the cementing plane after peak shear stress and the tensile strength of 32% compared with that of non-anchored case. According to the combined effect of step shaped chipping of 30 mm and anchor pin with an interval of 15 cm, the peak cohesion reached up to 77% and the residual cohesion showed 180% of the ones of the fresh concrete, respectively.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4B
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• pp.309-314
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• 2011

Analysis of discharge characteristics through control gates at river crossing structures is important for an effective water level control and water resources management. In recent years, many river control structures in four major rivers are under construction but only few researches on discharge characteristics at control gates could be found in Korea. The discharge characteristics depend on both shape of control gates and the effects of downstream water-depth. In this research, classification index for discharge patterns (free weir, submerged weir, free orifice, submerged orifice) through a control gate were reviewed with $h_g/h_1$, $h_3/h_g$, and $h_3/h_1$. Classification criteria of discharge patterns were also suggested. Representative discharge estimation equations for each discharge patterns were adopted and discharge coefficients were developed from a hydraulic model for a specific control gate which will be constructed in Nakdong river. Reliability of the derived discharge equation and coefficients were confirmed by comparisons between the real discharge in a model and the predicted discharge from the results of this research.

• Journal of Korea Water Resources Association
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• v.48 no.5
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• pp.379-391
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• 2015

Multi-functional weirs has been installed in four rivers are hydraulic structures across the river. The structures were divided into movable and fixed weirs. Hence, riverbed-level variation and sediment transport can be varied due to water gate operation. In this study, the long-term riverbed-level variation of Geum river basin due to water gate operation of multi-functional weirs was studied. Result of this study shows that the variation of thalweg elevation was greater than the variation of annual average riverbed elevation due to multi-functional weirs construction and water gate operation. Maximum riverbed degradation of thalweg elevation that occurred was 2.79m and riverbed aggradation was 1.90m. Maximum riverbed degradation of the annual average riverbed elevation that occurred was 2.16m and riverbed aggradation was 1.24m. Analysis result of flood stage by the variation of riverbed-level shows that flood stages were increased in majorities area. The maximum increase in the value of flood stage was 2.23m. For this reason, flood stages can be greater than the freeboard of the levees. Therefore, we should consider the water gate operation of multi-functional weirs when planning and managing sediment in the river. We are expecting to use the result of this study in river planning for river management and selecting the river regime.