• Corrosion Science and Technology
• /
• v.20 no.3
• /
• pp.143-151
• /
• 2021

In this study, optimal shot peening process conditions were investigated for improving the cavitation erosion resistance of gray cast iron under a marine environment. Shot peening was performed with variables of injection pressure and injection time. The durability was then evaluated through cavitation erosion test which was conducted according to the modified ASTM G-32 standard. The tendency of cavitation erosion damage according to shot peening process condition was investigated through weight loss rate, surface and cross-sectional analysis of the specimen before and after the test. As a result, the shot peening process condition that could minimize cavitation erosion was when the injection pressure was the lowest and when the injection time was the shortest. This was because the flake graphite exposed on the gray cast iron surface could be easily removed under such condition. Therefore, the notch effect can be prevented by surface modification. In addition, the cavitation erosion damage mechanism of gray cast iron was discussed in detail.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2022.04a
• /
• pp.208-209
• /
• 2022

This study aims to analyze the risk factors caused by object damage and third-party damage loss in actual bridge construction based on past insurance premium payment data from major domestic insurers for bridge construction projects, and develop a quantitative loss prediction model. For the development of quantitative bridge construction loss model, the dependent variable was selected as the loss ratio, and the independent variable adopted 1) Technical factors: superstructure type, foundation type, construction method, and bridge length 2) Natural hazards: flood anf Typhoon, 3) Project information: total construction duration, total cost and ranking. Among the selected independent variables, superstructure type, construction method, and project period were shown to affect the ratio of bridge construction losses, while superstructure, foundation, flood and ranking were shown to affect the ratio of the third-party losses.

• Proceedings of the KSR Conference
• /
• 2001.05a
• /
• pp.437-442
• /
• 2001

In Korea, collapse of railway slopes is frequently occurred due to tycoon or heavy rainfall doling rainy season and has been made personal and social damage greatly. In order to evaluate the stability of railway slopes under rainfall, explanatory variables and subordinate variables were selected for multivariate analysis. The sites which failure had occurred due to rainfall were investigated and critical rainfall was defined by the case that had high value of correlation factor after multivariate analyses for 121 cases had been executed. The maximum hourly rainfall during 24 hours before failure caused the collapse of railway embankment and the 0.3 square value of maximum hourly rainfall during 24 hours before failure caused the collapse of railway cut-slope, From the application to collapse examples, it is judged that critical rainfall curve will be used to estimate the stability of slopes.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2012.05a
• /
• pp.467-467
• /
• 2012

As the features of recent flood are spatially concentrated, loss of life and property increase by the impact of climate change. In addition to this the public interest in water control information is increased and socially reasonable justification of water control policy is needed. It is necessary to estimate the flood risk in order to let people know the status of flood control and establish flood control policy. For accurate flood risk analysis, we should consider inter-relation between causal factors of flood damage. Hence, flood risk analysis should be applied to interdependence of the factors selected. The Bayesian networks are ideally suited to assist decision-making in situations where there is uncertainty in the data and where the variables are highly interlinked. In this research, to provide more proper water control information the flood risk analysis is performed using the Bayesian networks to handle uncertainty and dependency among 13 specific proxy variables.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.7 no.6
• /
• pp.1007-1019
• /
• 2015

The determination of the required seawall height is usually based on the combination of wind speed (or wave height) and still water level according to a specified return period, e.g., 50-year return period wind speed and 50-year return period still water level. In reality, the two variables are be partially correlated. This may be lead to over-design (costs) of seawall structures. The above-mentioned return period for the design of a seawall depends on economy, society and natural environment in the region. This means a specified risk level of overtopping or damage of a seawall structure is usually allowed. The aim of this paper is to present a conditional risk probability-based seawall height design method which incorporates the correlation of the two variables. For purposes of demonstration, the wind speeds and water levels collected from Jiangsu of China are analyzed. The results show this method can improve seawall height design accuracy.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.571-576
• /
• 2001

The objective of this study is to assess seismic damage potential and evaluate structural performance of columns in concrete moment frames. For this purpose the results of 3 former studies are compared. Experimental variables considered in these studies are lap-splice of longitudinal reinforcement, axial load level, longitudinal reinforcement ratio, etc. The columns in 1st story of the building are considered in these studies since the columns in 1st story shall resist largest axial force during an earthquake. Based on test results strength, ductility capacities as well as plastic hinge length are compared and discussed.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 1999.10a
• /
• pp.79-86
• /
• 1999

This paper aims to propose a method that helps maintenance engineers to evaluate the damage states of bridge systems by using a Fuzzy Fault Tree Analysis(FFTA). It may be stated that Fuzzy Fault Tree Analysis may be may useful for the systematic md rational condition and safety assessment for real bridge systems problems because the approach is able to effectively deal with all the related bridge system damages in terms of the linguistic variables that incorporate systematically experts experiences and subjective judgement.

• 제어로봇시스템학회:학술대회논문집
• /
• 2001.10a
• /
• pp.47.1-47
• /
• 2001

The drilling process has a great importance for the production technology due to its widerspread use in the manufacturing industry. In order to enhance a maximum production rate and prevent the drill from the damage, it is important to monitor and control the drilling system. Thrust force and cutting torque are the main output variables in the design of drilling control systems. In this paper, an alternative estimation method of thrust force by using flexible neural networks is proposed. Flexible neural network uses the sigmoid activation function with adjustable parameter in order to enhance the approximation accuracy ...

• International Journal of Highway Engineering
• /
• v.16 no.2
• /
• pp.119-129
• /
• 2014

PURPOSES : The purpose of this study is to develop the U-turn accident model at 4-legged signalized intersections in urban areas. METHODS : In order to analyze the characteristics of the accidents which are associated with U-turn operation at 4-legged signalized intersections in urban areas and develop an U-turn accident model by regression analysis, the tests of overdispersion and zero-inflation are conducted about the dependent variables of number of accidents and EPDO (Equivalent Property Damage Only). RESULTS : As their results, the Poisson model fits best for number of accident and the ZIP (Zero Inflated Poisson) fits best for EPOD, the variables of conflict traffic, width of opposing road, traffic passing speed are adopted as independent variable for both models. The variables of number of bus berths and rate of U-turn signal time at which the U-turn is permitted are adopted as independent variable only for EPDO. CONCLUSIONS : These study results suggest that U-turn would be permitted at the intersection where the width of opposing road is wider than 11.9 meters, the passing vehicle speed is not high and U-turn operation is not hindered by the buses stopping at bus stops.

• Journal of Environmental Science International
• /
• v.13 no.6
• /
• pp.505-512
• /
• 2004

This study was attempted to review the information data for minimizing the destruction of environmental naturalness and the visual damage of landscape from road construction by establishing a model of environmental naturalness for national roads in the suburb areas to suggest an answer to a research question, ' hat does decide the environmental naturalness of roadscape?'. We found that 1) The road-side slope showed no statistical significance in the description of environmental naturalness of roadscape, but the fact that the road-side slope from road construction is the destruction of natural topography cannot be overlooked. 2) In terms of the direction of value variations for independent variables, signboard and telegraph post, soundproofing and protection wall, structure, and building acted toward negative (-) direction, while mountains, sky, road trees, fields, and surrounding green including the road-side slope acted toward positive(+) direction. 3) The variable with highest relative contribution to dependent variables among independent variables is building, which has importance as many as 148 times of road-side slope, while the variable road-side slope has the least importance. Building has the importance of 7.22 times, mountains 5.51 times, road trees 2.59 times, surrounding green 2.54 times, structure 2.41 times, signboard and telegraph post 2.37 times, soundproofing and protection wall 2.20 times, and sky 1.32 times of the fields as a standard criterion values 1.