• Journal of Korean Society of Steel Construction
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• v.14 no.5 s.60
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• pp.627-639
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• 2002

Bridge construction is almost complete in many countries. Thus, the government and highway agencies change their focus from constructing to maintaining. Effectively maintaining bridges require predicting their lifespan using a system reliability viewpoint. Likewise, maintenance models based on the system reliability concept should be developed. Thus, this study developed maintenance models for preventive maintenance and essential maintenance using system reliability and lifetime distributions. The optimal maintenance strategy for an existing bridge was obtained using the developed maintenance models.

• Journal of Korean Society of Steel Construction
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• v.14 no.3
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• pp.443-452
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• 2002

Construction of highway bridges is almost complete in many countries. Thus, the government and highway agencies are shifting their remaining life span from the viewpoint of system reliability. As such, it is necessary to develop maintenance models based on system reliability concept. In this paper, preventive and essential maintenance models were developed using system reliability and lifetime distribution.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.232-237
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• 2008

Several research institutes including KISTEC and KRRI etc., recently, have studied maintenance activities and performance, in order to determine proper maintenance level and maintenance cost of rail tracks. But it may extremely difficult to make a decision in maintenance matters of concrete track and ballast containing other sub-components. For these reasons, this study investigate variables related to current maintenance, essential maintenance, and preventive maintenance. It is intended to suggest estimation method of proper maintenance cost maximizing rail track performance. It is stated that proposed approach may be very useful to make a decision of proper maintenance level. Typical section of rail track is applied for calculation of life cycle cost according to each maintenance strategy. A proper profile for maintenance is determined minimum life cycle

• Nuclear Engineering and Technology
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• v.7 no.2
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• pp.159-165
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• 1975

The Nuclear power industry today faces a serious and rapidly emerging problem in reactor maintenance and occupational radiation exposure control. The basic problem is the need for much maintenance on nuclear power plants. The problem is seriously compounded by radiation exposure control requirements. Many studies are underway seeking solutions tut the industry is developing rapidly and new plants will not await the results of such studies. It is essential that attention be given to maintenance and exposure control in all phases of plant design, construction and operation.

• Journal of the Korean Society for Railway
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• v.8 no.6 s.31
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• pp.544-549
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• 2005

Nowadays, most of bridge networks are complete or close to completion. The biggest challenge railroad./highway agencies and departments of transportation face is the maintenance of these networks, keeping them safe and serviceable, with limited funds. To maintain the bridges effectively, there is an urgent need to predict their remaining life from a system reliability viewpoint. And, it is necessary to develop the maintenance models based on system reliability concept. In this paper, maintenance models are developed for preventive maintenance and essential maintenance by using system reliability and lifetime distributions. The proposed model is applied to an existing railroad bridge. The optimal maintenance strategy of this bridge is obtained in terms of services life extension and cumulative maintenance cost.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.331-336
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• 2005

A lot of manufacturing knowledge and method have applied to increase manufacturing efficiency in industry field. DES(Discrete Event Simulation) is one of solution to deal with manufacturing problems in factory. Beginning of research, old maintenance system of KNR ( Korea National Railroad) and its technical problems are basically investigated. KNR has maintained railway vehicle with their own solution based on experience. Very advanced railway vehicles such as KTX (Korea Train Express) and TTX(Tilting Train Express) will be difficult to maintain with their old maintenance method. In order to apply knowledge of DES, maintenance field of railway must be considered. Imaginary maintenance machine are selected to variable of DES. Maintenance capability of each machine will be evaluated base on imaginary data from imaginary machine. The machine could be very expensive as well as difficult to replace. Target of research is minimization of number of machine in railway workshop. So basic knowledge of discrete event simulation is introduced. Then five essential stages of discrete event simulation are provided. Each maintenance case defined as event. Each event is discrete and simulated base on different case such as one maintenance line with one machine and one maintenance line with two machines in railway workshop. simple maintenance method, discrete event simulation, will be come out very powerful in complicate maintenance system and will be helpful to reduce maintenance cost as well as maintenance labor.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.43 no.3
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• pp.41-52
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• 2020

This paper investigates the stress-reducing preventive maintenance model through numerical experiments. The preventive maintenance model is used to analyze the relationship between related conditions and variables to gain insight into the efficient operation of the system when performing preventive maintenance in real-world situations. Various preventive maintenance models have been developed over the past decades and their complexity has increased in recent years. Increasing complexity is essential to reflect reality, but recent models can only be interpreted through numerical experiments. The stress-reducing preventive maintenance is a newly introduced preventive maintenance concept and can only be interpreted numerically due to its complexity, and has received little attention because the concept is unfamiliar. Therefore, for information purposes, this paper investigates the characteristics of the stress-reducing preventive maintenance and the relationship between parameters and variables through numerical experiments. In particular, this paper is focusing on the economic feasibility of stress-reducing preventive maintenance by observing changes in the optimal preventive maintenance period in response to changes in environmental stress and the improvement factor. As a result, when either the environmental stress or the improve effect of stress-reducing preventive maintenance is low, it is not necessary to carry out the stress-reducing preventive maintenance at excessive cost. In addition, it was found that the age reduction model is more economical than the failure rate reduction model.

• Proceedings of the KSR Conference
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• 2007.11a
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• pp.784-791
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• 2007

Most operational organization and railway authority which conduct scheduled maintenance(SM) have carried out the preventive maintenance(PM) based on the information provided from supplier and manufacturer of railway system. However these activities are far away from reality and low the efficiency, it is because an appropriate methods for system selection didn't take into account for improving maintenance efficiency. Therefore, the current SM tasks and maintenance activities lead to lots of spend on the cost and time. To solve the above problem, this thesis presents new approach methodology. This proposes the criteria for reliability centered maintenance(RCM) system selection through level of quantification of each parameter, i.e, frequency, severity and maintenance cost, etc. To do this, the field operation data and information of maintenance cost are essential. As applying this methodology, we can look forward to improving efficiency of PM/SM, and reducing cost.

• International Journal of Railway
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• v.1 no.3
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• pp.94-98
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• 2008

Static inverters are essential devices onboard of rolling stock. State-of-the-art static inverters have an impact on both rail infrastructure and vehicle maintenance due to their new topology with new features. The paper describes two important aspects as examples of new features available in state-of-the-art static inverters: active input current control and the effects on the rail infrastructure as well as the detection of the state of charge and the state of health of batteries to simplify vehicle maintenance.

• KIEE International Transactions on Power Engineering
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• v.5A no.4
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• pp.331-338
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• 2005

In this paper, an improved maintenance scheduling approach suitable for the competitive environment is proposed by taking account of profits and costs of generation companies and the formulated combinatorial optimization problem is solved by using Reactive Tabu search (RTS). In competitive power markets, electricity prices are determined by the balance between demand and supply through electric power exchanges or by bilateral contracts. Therefore, in decision makings, it is essential for system operation planners and market participants to take the volatility of electricity price into consideration. In the proposed maintenance scheduling approach, firstly, electricity prices over the targeted period are forecasted based on Artificial Neural Network (ANN) and also a newly proposed aggregated bidding curve. Secondary, the maintenance scheduling is formulated as a combinatorial optimization problem with a novel objective function by which the most profitable maintenance schedule would be attained. As an objective function, Opportunity Loss by Maintenance (OLM) is adopted to maximize the profit of generation companies (GENCOS). Thirdly, the combinatorial optimization maintenance scheduling problem is solved by using Reactive Tabu Search in the light of the objective functions and forecasted electricity prices. Finally, the proposed maintenance scheduling is applied to a practical test power system to verify the advantages and practicability of the proposed method.