• Journal of the Korean Society of Safety
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• v.24 no.5
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• pp.48-56
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• 2009

This paper presents the procedure for the optimal design of a PSC-I girder bridge considering life cycle cost (LCC). The load carrying capacity curves for the concrete deck, PSC-I girder and $\pi$-type pier were derived and used for the estimate of service lives. Total life cycle cost for the service life was calculated as sum of initial cost, damage cost, maintenance cost, repair and rehabilitation cost, user cost, and disposal cost. The advanced First Order Second Moment method was used to estimate the damage cost. The optimization method was applied to the design of PSC-I girder bridge. The objective function was set to the annual cost, which is defined by dividing the total life cycle cost by the service life, and constraints were formulated on the basis of Korean Standards. The optimal design was performed for various service lives and the effects of design factors were investigated.

• Journal of the Korea Safety Management & Science
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• v.3 no.4
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• pp.1-9
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• 2001

Cost-benefit analysis was investigated to propose the analysis method of the effect of investment and the optimum investment level of safety management cost for preventing gas accident in the B governor station. From five classifications of safety management costs consisting of cost items with similar characters and potential accident costs calculated by risk assessments(FMEA/HAZOP), we found that the order of the benefit(the reduction cost of the potential accident cost) was the instrument increase and repair cost > the safety checking and inspection cost > the labor and training cost > the safety equipment and corresponding cost > the research and development cost. As the benefit was increased with increasing the investment cost, the effect of investment was increased with decreasing the Investment cost. As a result, the optimum safety management cost was estimated and the investment level was analyzed by the model of optimum investment level.

• The Journal of Fisheries Business Administration
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• v.9 no.2
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• pp.59-89
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• 1978

The analyzed results of the actual state of stow net fishery based on the cost expended are as follows. According to the calculation of interests, the total cost of this fishery comes to ￦38,010,653 and in this account, the production cost comes to ￦35,477,198(93.3%), the material cost, 14,567,239(38.3%), the labour cost, 12,740,274(33.5%), the expenses, ￦8,169,685(21.5%), the commision and administration expenses, 2,533,455(6.7%). The expenses for this fishery are paid out as production costs, and the expenses for sale and administration expenses are the lowest of them, and the 93% of expenses are paid out as production costs. The ratio of cost element to 100% is as follow. The wages, 28.4%, fuel, 15.2%, repair, 11.6%, deprecation, 9.5%, fishing gear, 8.7%, ice, 6.1%, container(box for fish), 5.2% administration expenses, 5.2%, food, 3.5%, ship grar, 3.2%, public welfare, 1.7%, commision for sale, 1.5%, insurance for crew, 0.2%, taxes, 0.2%. This fishery is managed with the larger fishing boat than it was and so, it demands better crews with higher wages. In the former fishery, the search for fishing ground is very difficult with long navigation and great fuel consumption. when the weak fishing gears are used, the expenses for their repair and for their gears are greatly paid out. The unit costs of catches to each box come to ￦2.807(￦187 each kg). As the ratio of cost of sales comes to 86.7%and the ratio of interests comes to ￦5,850,812(13.3%), and so the net profit comes to 13.3% of total profits. According to above the ratio of cost of sales is shown as a universal validity, Asthe total expenses comes to 86.7% to the money on sales in the break-even point, the break-even point comes to ￦26,209,168 Accordingly for the profit control the account of production should be raised, and by the saving method of expenditure the break-even point should be brought down for the development of total profits.

• Proceedings of the Korea Concrete Institute Conference
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• 1993.10a
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• pp.71-78
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• 1993

The R/C structures is very popular because of its low construction cost and its semi-permanent life. But in Korea, unfortunately there are few exprets in this field, and the repair methods and selection of material for R/C structures are determined by their subjective personal opinions. Therefore systematic study of this field is ulgently required. For attainning this purpose, in this study the related documents and knowledge or experience from human experts were collected. Based on the collected information cracks are classified into 25 patterns and repair related-knowledge base, which will be formulated and encoded into the domain knowledge, is built. And then an expert system, that can suggest the repair methods in the same way the human experts would, is developed. The results using the developed expert system are compared to the real field practices and they are satisfactory.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2006.06a
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• pp.287-288
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• 2006

Cracks on the cylinder block of diesel engines will often happen due to cyclic load and thermal stress. According to the Classification Societies' rules, welding repairs of cylinder block made of cast irons are generally not permitted. However, such welding repairs became inevitable taking enormous cost and time for their renewal into consideration. In this study repair welding methods for the cylinder blocks, made of gray cast irons were reviewed and the tests of their welds were carried out in order to purpose the repair welding methods of packing seat and o-ring seat of cylinder block and apply them to the practice. It is concluding remarks that the suspected crack by a magnetic particle test due to different magnetic permeability can be identified, which are not associated with a mechanical discontinuity.

• Journal of Aerospace System Engineering
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• v.10 no.2
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• pp.27-33
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• 2016

For the continued airworthiness of aviation products, aviation authority requires that every manufacturer should provide ICA(Instruction of Continued Airworthiness) to their users, and the users should follow it by themselves or using another approved maintenance agent. To reduce the cost and improve performance quality of maintenance activities, lots of users tries to outsource this job. To perform maintenance or repair of other owned air products, an air carrier and aviation maintenance companies should obtain AMO(approval of maintenance organization). It means AMO is a postulation to enter MRO(Maintenance Repair and Overhaul) market. For that, this paper discusses the comparison of requirements and procedures of AMO system between Korea and US to help understand the AMO system, and then, tries to point out what improvement should be made to Korean AMO system to be more effective, efficient and safe.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.32 no.4
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• pp.9-16
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• 2009

본 논문에서는 시스템 연령(年齡)에 의해 보전 활동의 효과를 설명하는 일반 수리(修理) 개념을 이용한 최적 보전(保全) 정책에 대한 연구를 수행하였다. 본 논문에서는 주기적인 일반 수리와 고장 시 최소 수리가 적용되는 최적 보전 정책을 고려하였다. 따라서 일반 수리에 따른 보전 정책의 비용 함수를 도출하였고 최적 보전 정책을 도출하는 알고리즘을 제시하였고 예제를 통해 알고리즘의 성능을 분석하였다. 이 연구를 통해 시스템을 운영하는데 있어서 어느 수준의 보전 정책을 적용하며 어느 정도의 기간 동안 시스템을 유지할 것인지에 대안을 제공할 수 있을 것이다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.576-579
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• 1997

In order to repair sewage pipes, it is necessary to dig up the damaged sewage pipes, which results in traffic jams. Since digging up the pipes takes too much time and cost, this method is inefficient. So, in stead of digging up the damaged pipes, a robot is sent down to the pipe to do the repair works. For big pipes, human workers go into the pipe and do to repair works, but for small pipes, it is impossible for human worker to go inside the pipe. In this case, mobile robots have used. The procedures for repairing pipes are as follows : First, the condition of the sewage pipes is observed by a robot. Second, appropriate steps for repair are determined according to the types of the damage. While repairing procedures, a newly-developed packer is sent into the sport to be repaired inside the pipe. Then, the packer is filled with air by a V-shaped wrinkel pipe. This makes the packer inflates uniformly and adhere closely to the inside wall of the pipe in large area. This increases the area that can be repaired. Therefore, the newly-developed packer will be very helpful for sewage pipe repair works.

• Journal of the Korean Institute of Educational Facilities
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• v.24 no.6
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• pp.27-36
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• 2017

Educational facilities have an affect to make a decently learning environment. After constructed, it needs a maintenance plan to keep the performance or function which provide the repair time, repair scope and ratio. But the fundamental data are so insufficient that the field worker can't provide the maintenance plan and has no choice use the other data which concerned with apartment or office building. Above all, the service life is indispensible to make a repair plan because the repair time and scope would be provided within the service life. This study aimed at providing the method to make a service life of component in educational facilities and applying the method into the roof proof and floor finishing. Results are shown that first, it is important to set the $1^{st}$ repair time after constructed. when it proposes the three ways with the probability approach, choice probability model and cumulative cost function. Second, the service life of roof proof is provided with about 35 years. In addition, the service life of the floor finishing is about 40 years. These result would be utilized to conduct the repair plan under the service life.

• Computers and Concrete
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• v.6 no.4
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• pp.281-303
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• 2009

The lack of safety of bridge deck structures causes frequent repair and strengthening of such structures. The repair induces great loss of economy, not only due to direct cost by repair, but also due to stopping the public use of such structures during repair. The major reason for this frequent repair is mainly due to the lack of realistic and accurate assessment system for the bridge decks. The purpose of the present research was to develop a realistic expert system, called Bridge Slab-Expert which can evaluate reasonably the condition as well as the service life of concrete bridge decks, based on the deterioration models that are derived from both the structural and environmental effects. The diagnosis assessment of deck slabs due to structural and environmental effects are developed based on the cracking in concrete, surface distress and structural distress. Fuzzy logic is utilized to handle uncertainties and imprecision involved. Finally, Bridge Slab-Expert is developed for prediction of safety and remaining service life based on the chloride ions penetration and fick's second law. Proposed expert system is based on user-friendly GUI environment. The developed expert system will allow the correct diagnosis of concrete decks, realistic prediction of service life, the determination of confidence level, the description of condition and the proposed action for repair.