• 한국해양공학회지
• /
• 제34권3호
• /
• pp.208-216
• /
• 2020

The Integrated Offshore Standard Specification (IOSS) involves Korean shipyards, classification societies, research institutes, the Korean industrial society, engineering companies, and oil companies with the objective of reducing costs and risks without compromising safety in international offshore engineering procurement construction (EPC) projects using new standardized bulk components and qualification procedures. The activities of the IOSS include the analysis of the existing rules and regulations to achieve the best standardization, which is reflected in the best practices, and minimize the variables in regulations and rules. In addition, a standard inventory of shapes and dimensions, referred to as specifications, is proposed in the IOSS. In this paper, the aluminum tertiary standardization part (IOSS S102-1/2 S104: Specification for Structural Tertiary Design) is presented with the details of the procedures, background reviews, and cost-benefit analyses of the design and verification methods for standard designs in the IOSS standardization items. Based on the cost-benefit analysis, the application of standardized aluminum tertiary items to offshore projects has significant advantages in terms of maintenance and repair compared to the carbon steel tertiary items utilized in current industrial practices.

• 한국화재소방학회논문지
• /
• 제16권2호
• /
• pp.1-7
• /
• 2002

유도등은 일정한 조도를 가지고 상용전원에 의하여 항상 점등되어 있어야 함으로 전력소비 및 광원 교체등 경제적 손실과 관리상의 문제가 있게 된다. 본 논문은 이제까지 광원으로 사용하고 있던 형광등이나 백열전구 대신에 소비전력이 적은 고효율 발광다이오드를 사용하여 전력소비의 절감과, 점검시의 문제점을 개선하기 위해 원격제어가 가능한 새로운 유도등회로를 제안하고 실험한 것이다. 그 결과 원격제어 스위치에 의한 유도등 점검을 제어각의 범위에서 쉽게 제어할 수 있었으며 반응시간은 600〔$\mu$s〕로 매우 빠르게 동작하였다. 또한 출력 상승시간(Rise time)과 하강고시간(Fall time)은 최대 200〔ns〕로 예민하게 반응하였다. 광원으로 고효율 발광다이오드를 사용함으로 광원을 교체해야 하는등의 문제를 제거하였으며 전력소비를 감소시킬 수 있음을 확인하였다.

• 한국도로학회논문집
• /
• 제15권4호
• /
• pp.127-133
• /
• 2013

PURPOSES : The impact performance of flexible barrier system such as structural response, vehicular motion and occupant safety vary depending on the impact point. Thus, to properly evaluate the performance of a flexible barrier system, impact should be made to a point which will lead to the worst possible results. This point is called the Critical Impact Point (CIP). This paper presents the way to determine the CIP for a SB2 class flexible barrier system which is consisted of Thrie-Beam rail and circular hollow tube post of 2m span. METHODS: Barrier VII simulations were made for impact points; Case 1 at a post, Case 2 at 1/3 span downstream from a post, Case 3 at middle of the span, Case 4 at 2/3 span downstream from a post. For the structural performance (deflections), impact simulation of 8000kg-65km/h-15degree was used, and for vehicle motion and occupant safety, simulation of 1300kg-80km/h-20degree impact was made and analysed. RESULTS: Case 1 gave the largest dynamic deflection of 75.72cm and also gave the largest snag value of 44.3cm. Occupant safety and exit angle of the vehicle after the impact were not sensitive to the impact point and were all below the allowable limit. CONCLUSIONS : For the SB2 class flexible barrier system's CIP can be regarded as a post which is sufficiently away from the end of Length of Need in order to avoid the end-effect of the barrier system. It can be more economic in the long run because the normal concrete pavement material is likely to cost more due to higher probability of maintenance and repair and higher social cost due to traffic accident, etc.

• Tribology and Lubricants
• /
• 제37권2호
• /
• pp.48-53
• /
• 2021

Wind energy is considered as the most competitive energy source in terms of power generation cost and efficiency. The power train of the pitch drive for a wind turbine uses a 3-stage complex planetary gear system in being developed locally. A gear train of the pitch drive consists of an electric or hydraulic motor and a planetary decelerator, which optimizes the pitch angle of the blade for wind generators in response to the change in wind speed. However, it is prone to many problems, such as excessive repair costs in case of failure. Complex planetary gears are very important parts of a pitch drive system because of strength problem. When gears are designed for the power train of a pitch drive, it is necessary to analyze the fatigue strength of gears. While calculating the specifications of the complex planetary gears along with the bending and compressive stresses of the gears, it is necessary to analyze the fatigue strength of gears to obtain an optimal design of the complex planetary gears in terms of cost and reliability. In this study, the specifications of planetary gears are calculated using a self-developed gear design program. The actual gear bending and compressive stresses of the planetary gear system were analyzed using the Lewes and Hertz equation. Additionally, the calculated specifications of the complex planetary gears were verified by evaluating the results from the Stress - No. of cycles curves of gears.

• 콘크리트학회논문집
• /
• 제29권1호
• /
• pp.3-10
• /
• 2017

내 공용중인 고속도로의 60%는 콘크리트로 포장이 되어 있으며, 그중 50% 이상의 도로가 설계 수명 이상 사용으로 인해 포장 손상, 줄눈부 파손, 부분 탈락 등의 다양한 문제가 발생하고 있다. 하지만 기존 도로 구조물의 보수보강은 높은 비용과 그로인한 복잡한 유지관리가 발생하므로 경제적인 보수보강 재료의 개발이 시급하다. 본 연구에서는 도로보수재료로서 기초물성 평가를 위해 칼슘 알루미나 시멘트에 OPC를 무게 대비 0, 10, 20%로 혼입한 재료를 적용하여 응결시간, 압축강도, 휨강도를 측정하였다. 그 결과, 최소물성 기준 및 재료 단가 측면을 고려하였을 때 20% OPC의 경우가 최적배합임을 도출하였다. 또한 일반적인 보수재료들을 이용한 특정 도로의 공사비용 산정을 위해, 상용 프로그램(CA4PRS)을 사용하여 경제성 분석을 실시하였다. 그 결과 20% OPC의 경우 총 시공 및 이용자 비용으로 각각 40.52, 15.77억 원이 발생하였으며, 총합으로 비교 시 가장 경제성이 높은 재료로 판단되었다.

• 농업과학연구
• /
• 제31권1호
• /
• pp.53-75
• /
• 2004

This study is aimed at identifying the national economic value of the irrigation facilities by reviewing the existing papers on economic values of the irrigation facilities and presenting current status of dual O & M problems of the irrigation facilities. This study suggested the unified O & M system rather than continuing the existing dual O & M system of irrigation facilities based on the surveyed results of the activities of irrigation fraternities in Chungnam Province. The findings and proposals for the successful unified and mono O & M system of the irrigation facilities are as follows: (1) Total number of irrigation facilities in the nation accounts for 67,582, while the total length of irrigation and drainage canals amounted to about 174,259km. On account of the total length of structural canals was estimated at 31%, much losses of water and much O & M costs have been inevitable for the full irrigation rice culture. In spite of the past heavy investment for irrigation facilities, the ratio of rain-fed and partially irrigated paddy fields accounts for 23% in 2003. Both Korea Agricultural and Rural Infrastructure Corporation (KARICO) and the city and Gun Governments have managed the irrigation facilities separately by irrigation fraternities. The KARICO have commanded 59% of irrigation paddy area with 18% of the total irrigation facilities, while the city and Gun governments covered 41% of irrigation paddy area with 82% of the existing number of irrigation facilities representing small and medium scale. (2) The 1999 demand prices of irrigation water per ton expressed in 2000 constant market price was estimated at 388 won, the supply price was amounted to 184 won per ton. Considering the supply and demand curve of the irrigation water, the existing irrigation facilities could not satisfy the demand of irrigation water. (3) In 1999, total present added value of the irrigation facilities during the economic life accounted for 48 trillion won, while total supply cost was 44.7 trillion won. The marginal benefit and cost ratio of irrigation water was 1.08. (4) The total O & M cost per year amounting to 681.1 billion won have been required to maintain and repair the existing irrigation facilities in Korea. For the successful unified O & M of irrigation facilities covering whole irrigated paddy field in Korea, 950 billion won of O & M costs are required to keep up the marginal benefit of irrigation water as 2,800 billion won per year. The total O & M cost as 950 billion won should be allocated 40%, 380 billion won for O & M costs of irrigation facilities and 60%, 570 billion won for improvement of irrigation facilities. (5) The study investigated and reviewed the present O & M status of the irrigation facilities by small and medium irrigation fraternities. Most of the farmers belong to the irrigation fraternities preferred not only unified O & M but also KARICO take-over of the whole O & M activities of the irrigation facilities. The prevailing O & M cost per 10a expended by the Corporation was amounted to 104,890 won, while that of city and Gun governments was only amounted to 4,600 won per 10a. regarding the small amount of O & M cost expended by city and Gun governments, it is evident that the existing irrigation system have been managed ineffectively and deteriorated the facilities comparing that of KARICO. In conclusion, the Government could not satisfied the demand of irrigation water by suppling water with existing irrigation facilities. Therefore new additional investment and financial support for irrigation water development should be made to convert rain-fed and partially irrigated paddy fields into fully irrigated ones. The operation and maintenance cost should be supported to keep the marginal values of rice production of existing irrigation facilities in the national economy and to modernize the obsolete irrigation facilities. By unifying the existing dual O & M systems, all the farmers belong to the irrigated paddy fields have to be equally benefited and could be increased their farm income and be stabilized their rural lives.

• 농촌계획
• /
• 제22권2호
• /
• pp.19-29
• /
• 2016

Disasters that occur most frequently in rural areas are drought, flood, damages from wind and cold weather. Among these, damages from storm and flood and drought are the main disasters and recently, these are occurring on a large scale due to unusual weather conditions. Under such circumstances, projects and researches on disasters in rural areas are under way but they are mostly targeting one area or making approaches focusing on repair facilities, maintenance project of facilities in small streams, and disaster management, so there have not been enough studies on the current status of overall damaged facilities in the rural areas. Against this backdrop, through the analysis of the current status of damaged facilities due to storm and flood in rural areas, this study aims to provide base data for policies needed for disaster recovery planning and maintenance work of rural areas. For the analysis of damaged facilities due to storm and flood in rural areas, using the annual report on disasters issued by Ministry of Public Safety and Security and based on the occurrence rate of estimated damage in each city and district for the past 10 years(2004~2013), 8 areas with the highest number of occurrence and cost of damage were found from each province and target areas were selected. Then, regarding the selected target areas, the General Plan for Reducing Damages from Storm and Flood, which is the report on top-level plan for preventing disasters, was secured and the current status of damaged facilities were analyzed. After organizing the analysis of current status, the tendency of damaged facilities due to storm and flood in rural areas, the items of damaged facilities depending on the types of storm and flood damages, and risk factors were suggested. Based on this result, in order to generalize the results of follow-up researches, it is thought that disaster recovery planning and establishing the system of remodeling items necessary for maintenance work would be possible by analyzing damage investigation items recorded in additional researches on rural areas, researches on natural disasters, and recovery plan instructions and by conducting on-site investigation on the damaged villages from storm and flood in rural areas.

• 한국조경학회지
• /
• 제40권1호
• /
• pp.81-91
• /
• 2012

본 연구는 조경공사 하자판례를 조사하여 하자소송의 일반적 분석, 공종별 판결 결과, 하자유형별 판결결과를 분석하고 하자분쟁을 완화하기 위한 조경공사 하자처리 개선방안을 제안하는 것이다. 본 연구의 주요 결과는 다음과 같다. 1. 2000년대 들어 조경공사와 관련된 하자소송이 증가하고 있으며, 소송 기간은 1심의 경우 603일, 2심의 경우는 550일로 나타나 사용자와 시공자 모두에게 심각한 시간적 경제적 손실을 초래하고 있다. 2. 감정금액 대비 인용금액이 1심의 경우 52.0%, 2심의 경우 57.3%, 전체적으로는 53.6% 수준으로 감정금액이 과다하게 책정되는 경향이 있는 것으로 나타났다. 3. 공종별 하자판결 결과는 조경수목식재가 전체 하자 발생 공종의 75%에 달하여 주요한 쟁점으로 나타났으며, 사용자인 원고의 승소율이 77%에 달하여 시공자들의 하자이행에 심각한 부담으로 나타났다. 4. 하자유형별 판결 결과에서는 사용자의 유지관리 부실로 인한 하자가 28%를 차지하고 시공자인 피고의 승소율이 64%로 높게 나타나 사용자의 유지관리 책임이 중요하게 부각되었다. 이러한 문제를 개선하기 위해서는 하자를 줄일 수 있도록 정확한 시공을 하고, 적절한 유지관리를 시행하도록 해야 하며, 부적기 식재 및 천재지변에 의한 피해 등 하자면책규정, 공종별 하자판정기준, 하자이행절차 등을 포함하는 조경공사 하자판정 및 처리기준을 마련해야 한다.

• 한국터널지하공간학회 논문집
• /
• 제23권4호
• /
• pp.221-232
• /
• 2021

유지관리에 활용되는 계측 센서들은 교통 수단 통행 및 강우와 같은 다양한 환경적인 요인에 지속적으로 노출됨으로써 손망실 가능성이 점차 증가하게 된다. 관련 연구에 따르면, 국내 지하철 터널 유지관리 계측 센서는 설치 후 약 5~6년이 경과한 상태에서 평균 14.2~14.8%의 손망실율을 보이고, 국외의 경우에는 동일 기준 약 13.9%로 국내외 평균 15%의 유지관리 계측 센서가 5~6년이 지난 후 정상적인 계측 값을 제공하지 못한다는 것을 알 수 있다. 원활한 유지관리를 위해서는 손망실 계측 센서에 대한 보수 및 교체를 통해 해당 계측 데이터를 확보해야 하지만, 일부 손망실된 계측 센서의 경우에는 설치 후 매립되어 유지보수 비용에 단순한 장비 구입만이 아닌 재시공까지 포함되는 등 계측 센서 보수에는 많은 시간 및 비용이 소요되고 이로 인한 지속적인 데이터 손실이 발생한다. 따라서 본 논문에서는 손망실 계측 센서의 보수 및 교체 기간 동안 일시적으로 손실되는 데이터를 추정치로서 보완하여 끊김 없는 인프라 유지관리를 지원할 수 있는 인접 센서 데이터 추세 분석 기반 손망실 계측 센서 데이터 추정 기법을 제안한다.

• 한국도로학회논문집
• /
• 제11권1호
• /
• pp.13-24
• /
• 2009

본 연구에서는 콘크리트의 건조수축을 저감시키며 강도와 내구성을 높임과 동시에 콘크리트의 주간 태양광에 의한 반사도를 줄인 저수축, 저반사, 고강도, 고내구성, 콘크리트 포장재료를 개발하였다. 문헌조사를 바탕으로 건조수축 저감과 장기강도 발현에 효과가 있는 플라이 애쉬와 반사도를 저감시키기 위하여 검은색 안료를 넣고 강도와 내구성을 좋게 하기 위해 최적입도를 고려하여 배합설계를 하였다. 실내실험을 통해 검은색 안료의 첨가율에 따른 명암값과 반사율은 차이가 없는 것으로 나타났으며 최적입도를 고려하면 강도와 내구성에서 좋은 것으로 평가되었다. 또한 플라이 애쉬를 사용한 배합이 건조수축 저감에 효과가 있었으며 염화이온 침투 저항성도 높은 것으로 드러났다. 플라이 애쉬(25% 치환)와 검은색 안료(3% 첨가)를 넣고 최적입도를 고려한 배합이 건조수축과 반사율 저감, 강도와 내구성 향상에 가장 적합한 배합으로 판단하였다. 경제성 분석을 통하여 일반 콘크리트 포장보다 저수축 저반사 고강도 고내구성 콘크리트 포장이 초기공사비는 많은 것으로 분석되었지만 장기적인 관점에서 유지보수비용과 사회비용 감소로 인하여 경제성으로 타당한 것으로 나타났다.