• Steel and Composite Structures
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• 제32권5호
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• pp.571-582
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• 2019

This study aimed to assess the feasibility on the wide and long 9%Ni steel plate for use in the LNG storage inner tank shell. First, 5-m-wide and 15-m-long 9%Ni steel plates were test manufactured from a steel mill and specimens taken from the plates were tested for strength, toughness, and flatness to verify their performance based on international standards and design specifications. Second, plates with a thickness of 10 mm and 25 mm, a width of 4.8~5.0 m, and a length of 15 m were test fabricated by subjecting to pretreatment, beveling, and roll bending resulting in a final width of 4.5~4.8 m and a length of 14.8m with fabrication errors identical to conventional plates. Third, welded specimens obtained via shield metal arc welding used for vertical welding of inner tank shell and submerged arc welding used for horizontal welding were also tested for strength, toughness and ductility. Fourth, verification of shell plate material and fabrication was followed by test erection using two 25-mm-thick, 4.5-m-wide and 14.8-m-long 9%Ni steel plates. No undesirable welding failure or deformation was found. Finally, parametric design using wide and long 9%Ni steel plates was carried out, and a simplified design method to determine the plate thickness along the shell height was proposed. The cost analysis based on the parametric design resulted in about 2% increase of steel weight; however, the construction cost was reduced about 6% due to large reduction in welding work.

• 한국건설안전학회 논문집
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• 제2권1호
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• pp.1-8
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• 2019

현재 건축물의 높이가 높아지고 우리나라 가구 형태가 개인 주택에서 아파트로 변화함에 따라 타워크레인의 사용 횟수는 계속해서 증가하고 있다. 그러나 이처럼 증가하는 타워크레인 사용 횟수에 반해 우리나라 타워크레인 관련 정책은 매우 미비한 실정이다. 특히 타워크레인과 관련된 사고의 원인 중 가장 큰 비중을 차지하는 타워크레인 연식에 대한 기준은 그 설정 근거가 부족하다. 따라서 본 연구에서는 이와 같은 문제점에 주목하여 타워크레인의 보다 신뢰성 있는 타워크레인의 연식을 설정하는 연구를 진행한다. 이를 위해 본 연구에서는 기존 연구에서 사용했던 사례와 영국 타워크레인 기준을 바탕으로 사용 연식을 설정한다.

• 대한치료과학회지
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• 제10권2호
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• pp.47-57
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• 2018

Objective: The purpose of this study was to compare the effects of exercise program combined with spaced retrieval and exercise program to show the effects on elderly people with dementia by presenting them to clinics and welfare facilities such as long-term care facilities. Method: This study was conducted in 20 elderly patients with dementia and randomly assigned to exercise program combined with spaced retrieval and exercise program. After screening the subjects for compliance with the criteria, Before starting the experiment, activites of daily living, depression, and nitive evaluation were performed. After 8 weeks, 3 times per week, 40 minutes per intervention, and 4 and 8 weeks, respectively K-MBI, GDSSF-K and MMSE-K were used to evaluate the differences between the experimental and control groups. Results: There was no statistically significant difference in the daily activities, depression, and cognitive scores between the groups of exercise program combined with spaced retrieval and exercise program group. However, there was a significant difference between the two groups after training (p<.05). Particularly, there was statistically significant difference in post-training cognitive evaluation (MMSE-K) only in the exercise program combined with spaced retrieval group (p<.05) Conclusion: This study suggests that exercise program combined with spaced retrieval is more effective in improving cognitive ability. This suggests that the exercise program combined with spaced retrieval is more effective.

• 환경영향평가
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• 제28권4호
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• pp.413-426
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• 2019

주거지 내 위치하거나 매우 인접한 곳에 무분별하게 난립된 개별입지 공장들은 궁극적으로는 준 산업단지 또는 새로운 계획입지로의 조정이 필요하다. 본 연구에서는 김포시 환경을 예로 김포시 전역에 난립된 개별입지 공장들을 새로운 지역으로 군집시킴에 따른 대기 $SO_2$ 오염도의 변화를 AERMOD 모형을 이용하여 평가하였다. 평가결과 개별입지 공장들의 공간 재배치를 통해 김포시 자체 배출원에 의한 오염도를 개선할 수 있는 가능성을 확인하였다. 재배치와 더불어 배출 굴뚝의 높이 조정과 같은 배출규제가 병행되는 경우 김포시 자체 배출원에 의한 오염도를 김포시 전체적으로 볼 때 약 70% 감소 가능하며 행정 구역별로는 최대 약 87% 감소 가능함을 정량적으로 확인하였다. 단, 군집지역으로 선정된 해당 행정구역은 김포시 전체 오염도의 변화 폭과 비교했을 때 상대적으로 큰 오염도 증가가 나타날 수 있다.

• International Journal of Naval Architecture and Ocean Engineering
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• 제11권1호
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• pp.624-637
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• 2019

A semi-submersible offshore platform always operates under complex weather conditions, especially wind and waves. It is vital to analyze the structural dynamic responses of the platform in short-term sea states under the combined wind and wave loads, which touches upon three following work. Firstly, a derived relationship between wind and waves reveals a correlation of wind velocity and significant wave height. Then, an Improved Mixture Simulation (IMS) method is proposed to simulate the time series of wind/waves accurately and efficiently. Thus, a wind-wave scatter diagram is expanded from the traditional wave scatter diagram. Finally, the time series of wind/wave pressures on the platform in the short-term sea states are converted by Workbench-AQWA. The numerical results demonstrate that the proposed numerical methods are validated to be applicable for wind and wave simulations in structural analyses. The structural dynamic responses of the platform members increase with the wind and wave strength. In the up-wind and wave state, the stresses on the deck, the connections between deck and columns, and the connection between columns and pontoons are relatively larger under the vertical bending moment. These numerical methods and results are wished to provide some references for structural design and health monitoring of several offshore platforms.

• 국제강구조저널
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• 제18권4호
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• pp.1191-1199
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• 2018

Concepts of submerged floating tunnels (SFTs) for land connection have been continuously suggested and developed by several researchers and institutes. To maintain their predefined positions under various dynamic environmental loading conditions, the submerged floating tunnels should be effectively moored by reasonable mooring systems. With rational mooring systems, the design of SFTs should be confirmed to satisfy the structural safety, fatigue, and operability design criteria related to tunnel motion, internal forces, structural stresses, and the fatigue life of the main structural members. This paper presents a feasibility study of a submerged floating tunnel moored by an inclined tendon system. The basic structural concept was developed based on the concept of conventional cable-stayed bridges to minimize the seabed excavation, penetration, and anchoring work by applying tower-inclined tendon systems instead of conventional tendons with individual seabed anchors. To evaluate the structural performance of the new type of SFT, a hydrodynamic analysis was performed in the time domain using the commercial nonlinear finite element code ABAQUS-AQUA. For the main dynamic environmental loading condition, an irregular wave load was examined. A JONSWAP wave spectrum was used to generate a time-series wave-induced hydrodynamic load considering the specific significant wave height and peak period for predetermined wave conditions. By performing a time-domain hydrodynamic analysis on the submerged floating structure under irregular waves, the motional characteristics, structural stresses, and fatigue damage of the floating tunnel and mooring members were analyzed to evaluate the structural safety and fatigue performance. According to the analytical study, the suggested conceptual model for SFTs shows very good hydrodynamic structural performance. It can be concluded that the concept can be considered as a reasonable structural type of SFT.

• 한국측량학회지
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• 제38권6호
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• pp.645-653
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• 2020

최근 무인비행장치의 활용방안에 대한 연구들이 활발히 진행되고 있다. 이를 지원하기 위해서 국토지리정보원은 『무인비행장치 이용 공공측량 작업지침』을 제정하였다. 하지만 작업지침에는 각 활용 분야에 필요한 최적의 촬영 조건은 제시되어 있지는 않다. 본 연구에서는 측량분야에서 많이 활용되는 3D 공간정보, 정사영상 제작에 적합한 촬영 조건을 알아보고자 하였다. 이를 위해 특별승인을 받지 않아도 비행할 수 있는 고도 150m 이내에서 다양한 고도, 중복도, 촬영각도에 따라 45번의 실험을 진행하였다. 3D 모델링의 촬영조건별 품질을 파악하기 위해 총 9곳의 검증영역의 점밀도를 분석하였으며, 정사영상과 1/1,000 수치지도를 비교하였다. 결과물의 품질과 작업시간을 고려할 때, 정밀 3D구축을 위해서는 촬영고도 50m 중복도 70~80% 촬영각도 80~90°의 촬영조건이 적합하고, 정사영상 제작에는 촬영고도 100m 촬영각도 80~90°의 촬영조건이 적합함을 알 수 있었다.

• 화약ㆍ발파
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• 제38권4호
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• pp.37-45
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• 2020

토도는 부산신항 앞바다에 위치한 무인도였다. 이 섬은 해발 32 m 높이의 작은 섬으로서 물속에 잠긴 부분을 포함한 총면적은 24,400 이었다. 그런데 불행하게도 이 섬은 부산신항의 북 컨테이너 부두와 남 컨테이너 부두로 들어가는 좁은 입구에 위치해 부두를 드나드는 수많은 선박들이 섬을 피해 운항하느라 급선회하면서 다른 선박이나 크레인과 자주 충돌하는 사고의 원인이 되어 왔다. 이와 같은 위험을 없애고, 해로를 더 넓고 깊게 만들기 위하여 해양수산부 당국은 토도를 제거하기로 결정하였다. 토도가 제거되면 부산신항 입구를 운항하는 대형 선박들의 안전이 확보될 것이고, 이는 부산신항의 경쟁력을 한층 높일 것으로 기대되었다. 이 논문에서는 토도 제거의 전체 과정을 상세하게 소개한다. 토도 제거작업은 국내 최초로 벌크 에멀젼 폭약과 비전기뇌관을 적용하여 성공적으로 수중발파를 완수한 최초의 사례이기도 하다.

• 한국안전학회지
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• 제36권3호
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• pp.31-39
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• 2021

In Korea, more than half of work-related fatalities have occurred on construction sites. To reduce such occupational accidents, safety inspection by government agencies is essential in construction sites that present a high risk of serious accidents. To address this issue, this study developed risk prediction models of serious accidents in construction sites using five machine learning methods: support vector machine, random forest, XGBoost, LightGBM, and AutoML. To this end, 15 proactive information (e.g., number of stories and period of construction) that are usually available prior to construction were considered and two over-sampling techniques (SMOTE and ADASYN) were used to address the problem of class-imbalanced data. The results showed that all machine learning methods achieved 0.876~0.941 in the F1-score with the adoption of over-sampling techniques. LightGBM with ADASYN yielded the best prediction performance in both the F1-score (0.941) and the area under the ROC curve (0.941). The prediction models revealed four major features: number of stories, period of construction, excavation depth, and height. The prediction models developed in this study can be useful both for government agencies in prioritizing construction sites for safety inspection and for construction companies in establishing pre-construction preventive measures.

• 한국습지학회지
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• 제23권3호
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• pp.234-241
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• 2021

본 논문은 자유수면을 갖는 와류수차의 성능에 풀리의 영향을 이해하는 것이다. 실험은 개수로 유입구 유량 0.0069 ~ 0.0077 m³/s 범위에서 물리적 인자(와류높이, 유속, 유효낙차 등)에 따른 수차의 회전수, 전압 및 전류를 측정해 분석하였다. 실험결과에 따르면 와류수차의 전압, 전류 및 회전수는 블레이드 형태와 상관없이 풀리비가 증가할 경우 감소하였다. 직선형 블레이드와 비틀린 블레이드의 효율은 풀리비 0.45 지점에서 52 %인 반면 소형 비틀린 블레이드의 효율은 풀리비 0.21 지점에서 54 %이다. 와류수차의 최대 발전량은 풀리비 0.5 지점 내에서 발생했다. 와류수차의 효율은 풀리비에 따라 0.2 ~ 58 % 범위에서 관찰되었다.