• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.26 no.6A
• /
• pp.943-953
• /
• 2006

We investigated experimentally the static behavior of an orthotropic bridge deck which is made from glass fiber reinforced polymer (GFRP) and polyurethane foam. The bridge deck consists of many unit cells with rectangular holes which are filled with the foam to improve its structural behavior in its weak axis. It is found that although the elastic modulus of the foam compared to that of the GFRP is about the order of, the structural behaviors in the weak axis such as nominal strength, stiffness, etc. are greatly improved. Owing to the low mass density of the foam used in this study, the bridge deck is still light enough with the improved structural properties. Webs of the cells filled with the foam did not significantly contribute to the strength development of the deck. However, the propagation of a crack initiated in a cell is caught by the webs and limited to the inside of that cell only, which makes the load-displacement behavior of the foam-filled GFRP deck less brittle.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.4
• /
• pp.61-68
• /
• 2017

Bridge decks are members that rapidly deteriorated due to various environmental factors such as heavy vehicle and deicing salt, etc. As the lifespan of bridges built in Korea increases, it is expected that the demand for replacing the deteriorated bridge decks will increase. In other countries, Accelerated Bridge Construction technology using precast decks is already actively being used as a countermeasure for replacement demand of deteriorated bridge decks. In this study, bridge decks deterioration models are proposed by collecting and analysing the condition index data of domestic bridge decks. Also, the future replacement demands of deteriorated bridge decks in terms of replacement time and replacement scale are predicted.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2006.05a
• /
• pp.352-357
• /
• 2006

매년 도로와 주차공간의 확장보다 차량의 수가 빠르게 증가하여 그에 따라 불법 주차 관리의 어려움이 증가하고 있다. 이러한 문제점을 해결하기 위해 지능형 주차 관리 시스템이 필요하게 되었다. 본 논문에서는 획득된 차량 영상에서 수직 에지의 특징을 이용하여 번호판 영역과 개별 코드를 추출하고, 추출된 개별 코드를 퍼지 신경망 알고리즘을 제안하여 학습 및 인식한다. 본 논문에서는 차량 번호판 영역을 검출하기 위해 프리윗 마스크를 적용하여 수직 에지를 찾고, 차량 번호판의 정보를 이용하여 잡음을 제거한 후에 차량 번호판 영역을 추출한다. 추출된 차량 번호판 영역은 반복 이진화방법을 적용하여 이진화하고, 이진화된 차량 번호판 영역에 대해서 수직 분포도와 수평 분포도를 이용하여 번호판의 개별 코드를 추출한다 추출된 개별 코드는 제안된 퍼지 신경망 알고리즘을 적용하여 인식한다. 제안된 퍼지 신경망은 입력층과 중간층간의 학습 구조로는 FCM 알고리즘을 적용하고 중간층과 출력층간의 학습 구조는 Max_Min 신경망을 적용한다. 제안된 방법의 추출 및 인식 성능을 평가하기 위하여 실제 차량 영상 150장을 대상으로 실험한 결과, 기존의 차량 번호판 인식 방법보다 효율적이고 인식 성능이 개선된 것을 확인하였다.

• Composites Research
• /
• v.25 no.4
• /
• pp.105-109
• /
• 2012

Recently, development of a small aircraft has been carried out for the BASA(Bilateral Aviation Safety Agreement) program in Korea. This aircraft adopted all composite structures for environmental friendly by low fuel consumption due to its lightness behavior. However the composite structure has disadvantage which is very weak against impact damages. Therefore, damage allowable design of aircraft structure must be performed considering compressive fracture strength. This point is very important for certification of composite structure aircraft. In this paper, it is performed the research on damage tolerance of thick laminate adopting aircraft structure. The damage tolerance of three different types of thick laminates such as no damage, open hole and impact damage is evaluated under compression loading.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.27 no.6
• /
• pp.625-633
• /
• 2014

Mark III CCS plate is considered in this paper to perform its strength assessment. Mark III CCS plate is designed and constructed by stacking various non-metallic engineering materials such as plywood, triplex and reinforced PU foam that are supported by series of mastic upon inner steel hull structure. From the viewpoint of structural analysis, this plated structure is treated as a laminated anisotropic structure. Commercially available general purpose finite element analysis programs such as MSC PATRAN and MARC are used to develop the finite element (FE) model of the Mark III CCS plate. Because of the characteristics of LNG cargo that the Mark III CCS plate deals with, it is subjected to a wide range of temperature variations, i.e. about $-163^{\circ}C$ to $20^{\circ}C$. Different material properties of the Mark III CCS plate at these temperature levels are considered in the FE model. Using the developed FE model, strength assessment procedure is developed incorporating various anisotropic failure criteria such as Hashin, Hill, Hoffman, Maximum stress and Tsai-Wu. The strength assessment is performed within the initial failure state of the Mark III CCS plate and, as a result, failure details such as failure locations and loads are identified.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.8 no.2
• /
• pp.147-158
• /
• 2004

For stiffened plates composed of composite materials, many researchers have used a finite element method which connected isoparametric plate elements and beam elements. However, the finite element method is difficult to reflect local behavior of stiffener because beam elements are transferred stiffness for nodal point of plate elements, especially the application is limited in case of laminated composite structures. In this paper, for analysis of laminated composite stiffened plates, 3D shell elements for stiffener and plate are employed. Reissner-Mindlin's first order shear deformation theory is considered in this study. But when thickness will be thin, isoparamatric plate bending element based on the theory of Reissner-Mindlin is generated by transverse shear locking. To eliminate the shear locking and virtual zero energy mode, the substitute shear strain field is used. A deflection distribution is investigated for simple supported rectangular and skew stiffened laminated composite plates with arbitrary orientation stiffener as not only variation of slenderness and aspect ratio of the plate but also variation of skew angle of skew stiffened plates.

• Journal of the Korea Organic Resources Recycling Association
• /
• v.25 no.1
• /
• pp.5-13
• /
• 2017

Polypropylene is the main existing material in the domestic market being used for the filter plate because of its moldability, low cost, and commercial availability. Polypropylene filter plate once distorted due to the high-pressure during operation may cause the problem in the continuous operation of the solid-liquid separation module. Thermoplastic Poly Urethane (TPU) can be a high-performance alternative material for the filter plate in the solid-liquid separation module of the dehydration process. Hence, to predict and evaluate the TPU for structural stability in the filter plate through analytical techniques designed and experimental verification is essential. As a result, TPU filter plate had maximum strain of 27.85 MPa at 20 bar pressure condition. This result is less than TPU stress-strain limit, which ensures the structural stability of the TPU material.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.1
• /
• pp.85-93
• /
• 2019

Structural performance and serviceability of precast deck system are mostly determined by connection details between precast decks. Particularly, since the bridge deck is under repeated loads such as traffic loads, fatigue behavior and performance of joints should be investigated. In this study, a two-girder continuous composite bridge specimen was fabricated using the asymmetric ribbed loop joints, and static and fatigue load tests were conducted to evaluate the structural behavior and the crack pattern of the bridge deck. From the test results, the proposed precast deck system resulted in sufficient fatigue performance and failure strength. Therefore, the proposed precast deck system can be applied to the connection part of precast decks effectively.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5A
• /
• pp.719-727
• /
• 2008

The tensile and bond performance of GFRP rebar are different from those of conventional steel reinforcement. It requires some studies on concrete members reinforced with GFRP reinforcing bars to apply it to concrete structures. GFRP has some advantages such as high specific strength, low weight, non-corrosive nature, and disadvantage of larger deflection due to the lower modulus of elasticity than that of steel. Bridge deck is a preferred structure to apply FRP rebars due to the increase of flexural capacity by arching action. This paper focuses on the behavior of concrete bridge deck reinforced with newly developed GFRP rebars. A total of three real size bridge deck specimens were made and tested. Main variables are the type of reinforcing bar and reinforcement ratio. Static test was performed with the load of DB-24 level until failure. Test results were compared and analyzed with ultimate load, deflection behavior, crack pattern and width.

• Journal of Science Education
• /
• v.32 no.2
• /
• pp.121-145
• /
• 2008

The purposes of this study were to identify the misconceptions that students have on the magma and plate tectonics and to present the implications in developing textbooks as well as related curriculum of high school textbooks. Data were collected through questionnaire, consisting of some questions, short essays, and descriptive drawings, developed by the research team. A total of 140 high school students(9th graders) responded to those questionnaires and were interviewed for further information. It was reported that participants displayed various misconceptions related to magma and plate tectonics. The identified misconceptions are as follows: For the definition of magma, the 31% of participants misunderstood magma as lava. In respect to the generative mechanism of magma at subduction zone, over 90% of students responded that it is generated by frictional heat. The source of misconceptions were identified as a result from textbooks and related reference-books. For the concept of plates, 87% of students conceived 'crust or a lower part of the plates' as 'plates'. Most participants hold the right concept of oceanic ridge, whereas, 66% of them considered 'rift valley' as either 'divergence of continental plates' or 'converging boundary'. 63% of them defined 'collision boundary of continental plate' as either 'subduction zone' or 'diverging boundary'. For the definitions of the trench and Benioff zone, 86% of students responded them as the place of subduction or differing density between two converging plates. The students' misconceptions were resulted from the errors and insufficient explanation, inappropriate figures, and data presented in textbooks, reference-books, lecture, and web sites. The results of this study are implied to contribute the improvement of students' misconceptions.