메가와트급 부유식 해상풍력발전기용 페어리드 체인 스토퍼의 강도 성능평가를 위한 구조 모형 시험

송창용 한국산업융합학회 2023 한국산업융합학회 논문집 Vol.26 No.3

Recently, the destructive power of typhoons is continuously increasing due to the influence of global warming. In a situation where the installation of floating wind turbines is increasing around the world, concerns about the huge loss and collapse of floating offshore wind turbines due to strong typhoons are deepening. Regarding to the safe operation of the floating offshore wind turbine, the development of a new type of disconnectable mooring system is required. A new fairlead chain stopper considered in this study is devised to more easily attach or detach the floating offshore wind turbine with mooring lines comparing to other disconnectable mooring apparatuses. In order to investigate the structural safety of the initial design of fairlead chain stopper that can be applied to MW-class floating type offshore wind turbine, scale-down structural models were produced using a 3-D printer and structural tests were performed on the models. For the structural tests of the scale-down models, tensile specimens of acrylonitrile butadiene styrene material that was used in the 3-D printing were prepared, and the material properties were evaluated by performing the tensile tests. The finite element analysis of fairlead chain stopper was performed by applying the material properties obtained from the tensile tests and the same load and boundary conditions as in the scale-down model structural tests. Through the finite element analysis, the structural weak parts on the fairlead chain stopper were reviewed. The structural model tests were performed considering the main load conditions of fairlead chain stopper, and the test results were compared to the finite element analysis. Through the results of this study, it was possible to experimentally verify the structural safety of the initial design of fairlead chain stopper. It is also judged that the study results can be usefully used to improve the structural strength of fairlead chain stopper in a detailed design stage.

분리하중에 대한 항공기용 외부연료탱크 구조 건전성 평가

김현기(Hyun-gi Kim),김성찬(Sungchan Kim),박민수(Min-su Park),안수홍(Su-hong An) 항공우주시스템공학회 2024 항공우주시스템공학회지 Vol.18 No.1

The external fuel tank of an aircraft is a main component that can increase the cruising range of the aircraft. It must be able to be stably separated from the pylon in an emergency situation. At this time, a separation load is applied to the fin and the pivot of the external fuel tank. To stably separate the external fuel tank, the structural soundness of the fin and the pivot must be confirmed. In this study, structural tests were conducted to verify the structural integrity of the external fuel tank pin and pivot when the external fuel tank was separated from the aircraft. Results are then presented. In this paper, a test configuration diagram consisting of the hydraulic and load control equipment, data acquisition system, and pneumatic supply unit used in the structural test was explained. Test installation and test load application plan for each test condition were provided. As results of the structural test, it was found that test load and internal pressure of the test specimen were properly controlled within the allowable range in each test. It was confirmed that serious structural defects in the test specimen did not occur under required load conditions. In conclusion, through structural test for design limit load and design ultimate load, it was proven that the fin and pivot of the external fuel tank for aircraft covered in this study had sufficient structural strength.

Shake table tests on a non-seismically detailed RC frame structure

Sharma, Akanshu,Reddy, G.R.,Vaze, K.K. Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.1

A reinforced concrete (RC) framed structure detailed according to non-seismic detailing provisions as per Indian Standard was tested on shake table under dynamic loads. The structure had 3 main storeys and an additional storey to simulate the footing to plinth level. In plan the structure was symmetric with 2 bays in each direction. In order to optimize the information obtained from the tests, tests were planned in three different stages. In the first stage, tests were done with masonry infill panels in one direction to obtain information on the stiffness increase due to addition of infill panels. In second stage, the infills were removed and tests were conducted on the structure without and with tuned liquid dampers (TLD) on the roof of the structure to investigate the effect of TLD on seismic response of the structure. In the third stage, tests were conducted on bare frame structure under biaxial time histories with gradually increasing peak ground acceleration (PGA) till failure. The simulated earthquakes represented low, moderate and severe seismic ground motions. The effects of masonry infill panels on dynamic characteristics of the structure, effectiveness of TLD in reducing the seismic response of structure and the failure patterns of non-seismically detailed structures, are clearly brought out. Details of design and similitude are also discussed.

Test Anxiety among Chinese Undergraduates from Urban versus Rural Backgrounds

Dianping Liu,Ken Springer,Yang-Hee Kim 국제언어문학회 2021 國際言語文學 Vol.- No.49

본 연구는 중국 도시와 농촌 학부생들의 시험 불안을 깊이 이해하기 위한 질적 연구이다. 이 연구를 위해 연변대학교에 재학 중인 5명의 도시 학생들과 5명의 시골 학생들이 참여하였다. 학생 개개인을 대상으로 실시한 정형화되지 않은 면접은 그들의 수행능력에 대한 자기평가, 시험 불안의 정도, 시험 불안 원인에 대한 이해, 선호하는 대처전략, 시험 불안을 줄일 수 있는 여부에 중점을 두었다. 인터뷰를 통해 모든 학생들이 반드시 시험 기간 동안에만 불안감을 느낀 것이 아니라 그들이 시험 전에 불안을 느꼈던 것으로 드러났다. 이러한 시험 불안을 해소하고자 학생들은 다양한 정서 중심 및 문제 중심 대처 전략을 사용했던 것으로 나타났다. 도시와 농촌 학생들 간 차이의 결과에서 시골학생들이 과하도록 심한 시험 불안을 경험했고, 자신 통제력을 포함한 시험 불안을 다루는데 있어 비교적 효율성이 떨어지는 대처 전략을 사용했다는 경향을 보였다. 마지막 성별에 따른 시험 불안에 대한 차이에서는 기대와는 다르게 차이가 발견되지 않았다. 이 연구는 농촌 학생들이 갖는 시험 불안에 대한 심각성을 이해함으로써 그들의 시험 불안을 줄여, 학교생활에 잘 적응할 수 있도록 방안을 찾는데 교육적 의의를 두었다. This is a qualitative research study conducted to deepen understanding of test anxiety among Chinese undergraduates from urban versus rural backgrounds in China. Five urban and five rural students currently attending Yanbian University participated in the study. Semi-structured interviews conducted with individual students focused on self-assessment of performance, extent of test anxiety, understanding of causes of test anxiety, preferred coping strategies, and the possibility to reduce test anxiety. The interviews revealed that all students experienced anxiety before tests but not necessarily during tests. To reduce test anxiety, students used a variety of emotion-focused and problem-focused coping strategies for dealing with test anxiety. The differences between urban and rural students tended to show that rural students appeared to experience more severe, unqualified test anxiety, and they relatively used less effective coping strategies involving self-control to deal with test anxiety than their urban peers. Finally, contrary to expectations, no gender differences in test anxiety were found. The educational significance of this study is to help reduce Chinese undergraduates’ test anxiety and adapt well to university settings by understanding the challenge of test anxiety, particularly among Chinese rural students.

Shake table tests on a non-seismically detailed RC frame structure

Akanshu Sharma,G.R. Reddy,K.K. Vaze 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.41 No.1

A reinforced concrete (RC) framed structure detailed according to non-seismic detailing provisions as per Indian Standard was tested on shake table under dynamic loads. The structure had 3 main storeys and an additional storey to simulate the footing to plinth level. In plan the structure was symmetric with 2 bays in each direction. In order to optimize the information obtained from the tests, tests were planned in three different stages. In the first stage, tests were done with masonry infill panels in one direction to obtain information on the stiffness increase due to addition of infill panels. In second stage, the infills were removed and tests were conducted on the structure without and with tuned liquid dampers (TLD) on the roof of the structure to investigate the effect of TLD on seismic response of the structure. In the third stage, tests were conducted on bare frame structure under biaxial time histories with gradually increasing peak ground acceleration (PGA) till failure. The simulated earthquakes represented low, moderate and severe seismic ground motions. The effects of masonry infill panels on dynamic characteristics of the structure, effectiveness of TLD in reducing the seismic response of structure and the failure patterns of non-seismically detailed structures, are clearly brought out. Details of design and similitude are also discussed.

자동차 충돌해석을 위한 구조용 접착제 유한 요소 해석 모델 개발

이태현(Taehyun Lee),신성기(Shounggi Shin) 한국자동차공학회 2008 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-

A very successful approach among the many things done is the use of structural adhesive, which have brought significant improvements in automobile for the reason that adhesive-bonded joints can reduce the stress concentration compared to mechanical joints, increase strength and endure against the environment variable such as corrosion. The objective of this paper is to develop structural adhesive model for car crash analysis. The power of the FEA for predicting the structural integrity of adhesively bonded vehicle structure is apparent. To obtain mechanical properties of the adhesives, First, Tensile test and shear test were carried out for material properties of structural adhesive such as young's modulus, shear modulus, strain- stress curves. Second, correlation between test and FEA is conducted to verify that the adhesive material properties derived earlier do indeed represent the mechanical properties of the physical adhesives in the single lap shear test, T-peel test, wedge impact test, three point bending test and compression test.

낙하시험에 의한 폴리에틸렌 보트의 구조 안전성 평가

이성룡(Sung-Riong Lee),강경주(Gyung-Ju Kang),조석수(Seok-Swoo Cho) 한국산학기술학회 2017 한국산학기술학회논문지 Vol.18 No.5

강선이나 강화플라스틱선 등의 선박 재료는 선박안전법에 규정된 규격재료를 사용하는 경우로서 판두께 측정시험이나 종굽힘강도시험을 통하여 제작 선체의 구조 안전성을 쉽게 확인할 수 있다. 한편, 염가의 폴리에틸렌 등과 같은 비규격재료를 선체 전장이 짧은 플레저 보트의 선체로 사용하는 경우 역학적 특성을 파악하기 쉬워 선체 설계를 수행하기에 매우 유리하고, 대량 생산 시스템을 갖추는 경우 제작 비용이 낮아 해당 제품의 가격 경쟁력을 가질 수 있다. 그러나 폴리에틸렌 선체의 경우 비규격재료를 사용함에 따라 기존의 소형선체에 대한 종굽힘강도시험을 이용하여 선체의 구조 안전성을 평가할 수 없다. 이러한 문제점을 해결하기 위하여 본 연구에서는 플레저 보트의 낙하시험 표준절차인 플레저 보트 검사 기준과 ISO 12215-5를 기초로 폴리에틸렌 선체에 대한 낙하시험을 수행한 후 이것을 기초로 정적구조해석을 수행하여 비규격재료로 개발된 선체의 구조 안전성을 확인함으로서 플레저 보트 검사 기준과 ISO 12215-5의 낙하시험방법이 선체 구조설계에 이용될 수 있음을 보였다. The structural safety of small craft, such as steel ships and FRP ships, can be estimated using the measurement test of the hull plate thickness or the longitudinal bending strength test. A polyethylene boat is made using inexpensive HDPE and can be mass produced. The structural safety of a polyethylene boat cannot be guaranteed because a polyethylene boat hull is notspecified in the KR technical rules. The inspection procedure of sailing yachts and pleasure boats and drop test method of ISO standard 12215-5 propose the structural strength required for small crafts as the drop test height. Therefore, in this study, the drop test of a polyethylene boat hull was carried out based on the inspection procedure of a sailing yacht and pleasure boat and the drop test method of ISO standard 12215-5. The drop load was acquired by the drop acceleration ofa boat hull. Structural analysis and safety of a polyethylene boat were performed by the drop load and allowable stress criteria. The calculation results of the hull plate thickness by structural design specification of ISO standard 12215-5 showed that polyethylene boat hull was more than two times thicker than a steel ship hull and the boat hull determined by the inspection procedure of sailing yacht and pleasure boat and drop test method of ISO standard 12215-5 was more than 1.2 times thicker than the boat hull determined by structural design specification of ISO standard 12215-5. Therefore, inspection procedure of sailing yachts and pleasure boats and drop test method of ISO standard 12215-5 was much more conservative than the structural design specification of ISO standard 12215-5 and could be used as the structural design method of a polyethylene boat.

An Analysis of the Test Items on Text Structures in High School English Tests

Sung-Ae Kim 한국응용언어학회 2010 응용 언어학 Vol.26 No.4

The aim of this study is to investigate how students’ comprehension of text structures is assessed in high school English tests. For that aim, the study analyzed 30 high school English tests, focusing on the frequency/proportion of the test items made on text structures and the types of tasks required by those items. In order to investigate the similarities and/or differences among the tests, the study also compared the tests for the three grades and for the same grade. The result shows that there is a great variation among the tests in the frequency of the test items on text structures, but the types of tasks asked by those items are quite limited and similar across all the tests. Based on the result, the study argues that the test items on text structures in high school English tests leave much room for improvement and teachers need help and guide in the construction of test items.

복합재료 조종면의 정하중 구조시험

조숙경,이명건,조창민,이기범 한국항공우주학회 2012 한국항공우주학회 학술발표회 논문집 Vol.2012 No.11

항공기에 장착되는 조종면의 종류는 플랩, 에일러론 등이 있고, 현재 운용중인 대부분의 항공기는 복합재로 제작된 조종면을 장착하고 있다. 본 연구에서는 항공기의 주익에 장착되는 조종면에 대한 구조건 전성을 검증하기 위해 정하중 구조시험을 별도로 수행하였다. 주익에 연결되는 실제 경계조건을 모사한 시험장치를 구성하였으며, 시험조건에 대한 유한요소모델(FEM)을 생성하여 금속재료 피팅 및 복합재료 샌드위치 구조에 대한 구조해석이 수행되었다. 임계하중 조건에 대한 설계제한하중시험(design limit load test: DLLT) 및 설계극한하중시험(design ultimate load test: DULT)을 수행하여 설계하중에 대한 구조건전성을 검증하였으며, 파단시험(design fracture load test: DFLT)을 통해 조종면이 견딜 수 있는 강도를 확인하였다. 시험결과와 해석결과를 비교하여 FEM의 상관성을 입증하였다. The control surfaces of an aircraft consist of flap and aileron. Most of the aircraft which is working has composite control surfaces. The static structural test for the control surface of the large composite wing box was performed to verify the static strength analysis and the design ultimate strength capabilities. The static test was set according to the real boundary condition. The finite element model was made and structural analysis was performed for the metal fitting and composite sandwich structure. The design limit load test and the design ultimate load test were performed and the ultimate strength of the control surface was confirmed by the design fracture load test. The comparison between the test results and the analysis results are presented here and discussed.

Patterns of Resistographs for Evaluating Deteriorated Structural Wood Members

LEE, Jun Jae,KIM, Kwang Chul,BAE, Mun Sung 한국목재공학회 2003 목재공학 Vol.31 No.6

The density and strength of wood is affected by degradations and defects, such as voids and knots. Old wooden structures such as traditional cultural properties have been deteriorated by these types of defects. They were evaluated by a visual observation that is difficult to evaluate the inner deterioration in structures. In this study, three nondestructive testing techniques were investigated to detect the wooden structural members. Ultrasonic stress wave tests, drilling resistance tests and visual inspections were used to examine the structural wood members. Patterns of Resistograph using by drilling resistance tests could indicate the features of internal wood such as voids, knots, decay, fungi, and so on. The technique just like as ultrasonic stress wave tests, however, difficult to detect exactly area where small amounts of internal deterioration in logs are. In spite of results of ultrasonic stress wave test, the internal deterioration of wooden structural members could be evaluated by the relationship between ultrasonic stress wave tests and drilling resistance tests.