• Title/Summary/Keyword: Design Durability

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Effect of the initial imperfection on the response of the stainless steel shell structures

  • Ali Ihsan Celik;Ozer Zeybek;Yasin Onuralp Ozkilic
    • Steel and Composite Structures
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    • v.50 no.6
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    • pp.705-720
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    • 2024
  • Analyzing the collapse behavior of thin-walled steel structures holds significant importance in ensuring their safety and longevity. Geometric imperfections present on the surface of metal materials can diminish both the durability and mechanical integrity of steel shells. These imperfections, encompassing local geometric irregularities and deformations such as holes, cavities, notches, and cracks localized in specific regions of the shell surface, play a pivotal role in the assessment. They can induce stress concentration within the structure, thereby influencing its susceptibility to buckling. The intricate relationship between the buckling behavior of these structures and such imperfections is multifaceted, contingent upon a variety of factors. The buckling analysis of thin-walled steel shell structures, similar to other steel structures, commonly involves the determination of crucial material properties, including elastic modulus, shear modulus, tensile strength, and fracture toughness. An established method involves the emulation of distributed geometric imperfections, utilizing real test specimen data as a basis. This approach allows for the accurate representation and assessment of the diversity and distribution of imperfections encountered in real-world scenarios. Utilizing defect data obtained from actual test samples enhances the model's realism and applicability. The sizes and configurations of these defects are employed as inputs in the modeling process, aiding in the prediction of structural behavior. It's worth noting that there is a dearth of experimental studies addressing the influence of geometric defects on the buckling behavior of cylindrical steel shells. In this particular study, samples featuring geometric imperfections were subjected to experimental buckling tests. These same samples were also modeled using Finite Element Analysis (FEM), with results corroborating the experimental findings. Furthermore, the initial geometrical imperfections were measured using digital image correlation (DIC) techniques. In this way, the response of the test specimens can be estimated accurately by applying the initial imperfections to FE models. After validation of the test results with FEA, a numerical parametric study was conducted to develop more generalized design recommendations for the stainless-steel shell structures with the initial geometric imperfection. While the load-carrying capacity of samples with perfect surfaces was up to 140 kN, the load-carrying capacity of samples with 4 mm defects was around 130 kN. Likewise, while the load carrying capacity of samples with 10 mm defects was around 125 kN, the load carrying capacity of samples with 14 mm defects was measured around 120 kN.

Measurement of Porcine Aortic and Pulmonary Valve Geometry and Design for Implantable Tissue Valve (돼지 대동맥, 폐동맥의 근위부 기하학적 구조 측정을 통한 판막 구조 수치의 계량화와 판막 도안에 관한 연구)

  • Park, Sung-Joon;Kim, Yong-Jin;Nam, Jin-Hae;Kim, Soo-Hwan;Lee, Chang-Ha;Lim, Hong-Gook
    • Journal of Chest Surgery
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    • v.43 no.6
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    • pp.602-613
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    • 2010
  • Background: As life expectancy has been increased, the cardiac valve disease has been increased. In past, mechanical valve for valve replacement surgery was used widely, but it has many weaknesses, such as hemorrhage, teratogenic effect caused by warfarin, acute mechanical failure, taking warfarin during life, etc. So, the tissue valve is used widely and researches for durability of tissue valve are in progress. Tissue valves being used are all imported in Korea, and there is a lack of information on its geometry and design. So, we studied the geometry of porcine aortic and pulmonary valve, and tried to suggest theoretical basis for making the aortic and pulmonary valve. Material and Method: We harvested aortic and pulmonary valves of 25 pigs and measured the geometry of valve at fresh and glutaraldehyde (GA) fixed state. In each group, we measured the diameter of the base, diameter of commissure, valve height, commissural height, etc. Also, for making implantable porcine and bovine pericardial valve, we designed the valve stent form, thickness, height, and leaflet size, form, thickness by different size of valve. Result: The aortic and pulmonary valve geometry and ratio were measured in each group. The right coronary cusp of aortic valve and right facing cusp of pulmonary valve was bigger than other cusps and non coronary cusp was smaller than others (RCC: NCC : LCC=1 : 0.88 : 1). Valve height was correlated to the leaflet size. We designed the outer diameter of stented porcine aortic valve from 19 mm to 33 mm and designed stent height and width, using previous measured ratio of each structure, stent thickness, working thickness (for making valve). Also, we designed the size of stent and form for stented bovine pericardial valve, considering diameter of valve, leaflet length, height and leaflet minimum coaptation area. Conclusion: By measuring of 25 pig's aortic and pulmonary valve geometry and ratio, we can make theoretical basis for making implantable stented porcine valve and bovine pericardial valve in various size. After making implantable valve using these data, it is necessary to do in vivo and in vitro researches, furthermore.

Effects of Encapsulation Layer on Center Crack and Fracture of Thin Silicon Chip using Numerical Analysis (봉지막이 박형 실리콘 칩의 파괴에 미치는 영향에 대한 수치해석 연구)

  • Choa, Sung-Hoon;Jang, Young-Moon;Lee, Haeng-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.25 no.1
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    • pp.1-10
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    • 2018
  • Recently, there has been rapid development in the field of flexible electronic devices, such as organic light emitting diodes (OLEDs), organic solar cells and flexible sensors. Encapsulation process is added to protect the flexible electronic devices from exposure to oxygen and moisture in the air. Using numerical simulation, we investigated the effects of the encapsulation layer on mechanical stability of the silicon chip, especially the fracture performance of center crack in multi-layer package for various loading condition. The multi-layer package is categorized in two type - a wide chip model in which the chip has a large width and encapsulation layer covers only the chip, and a narrow chip model in which the chip covers both the substrate and the chip with smaller width than the substrate. In the wide chip model where the external load acts directly on the chip, the encapsulation layer with high stiffness enhanced the crack resistance of the film chip as the thickness of the encapsulation layer increased regardless of loading conditions. In contrast, the encapsulation layer with high stiffness reduced the crack resistance of the film chip in the narrow chip model for the case of external tensile strain loading. This is because the external load is transferred to the chip through the encapsulation layer and the small load acts on the chip for the weak encapsulation layer in the narrow chip model. When the bending moment acts on the narrow model, thin encapsulation layer and thick encapsulation layer show the opposite results since the neutral axis is moving toward the chip with a crack and load acting on chip decreases consequently as the thickness of encapsulation layer increases. The present study is expected to provide practical design guidance to enhance the durability and fracture performance of the silicon chip in the multilayer package with encapsulation layer.

Digital painting: Image transfonnation, simulation, heterologie and transfonnation (현대회화에서의 형태와 물질 -Digital Transfiguration에 관한 연구-)

  • Jeong, Suk-Yeong
    • Journal of Science of Art and Design
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    • v.10
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    • pp.161-181
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    • 2006
  • The words which appeared in my theoretical study and work are image transformation to digital painting, simulation, heterologie and transfiguration, etc. Firstly, let's look into 'digital era' or 'new media era'. Nowadays, the image world including painting within the rapid social and cultural change, which is called as digital era, is having the dramatic change. Together with the development of scientific technology, large number of events which was deemed to be impossible is happening as real in image world Moreover, these changes in image world is greatly influencing to our life. The word which compresses this change of image world and shows is 'digital'. Digit, which means fingers in Latin, indicates separately changing signal, and to be more narrow, it indicates the continual signal of '0' and ' 1' in computer. The opposite word is 'analogue'. As analogue is the word meaning 'infer' or 'similarity', it indicates the signal or form which continuously changes along the series of time when it is compared to digital. Instead of analogue, digital is embossed as a major ruler along the whole area of our current culture. In whole culture and art area, and in whole generalscience, digital is appearing as it has the modernism and importance. The prefix, 'digital', e.g. digital media, digital culture, digital design, digital philosophy, etc, is treated as the synonym of modernism and something new. This advent of digital results the innovative change to the image world, creates the new beauty experience which we could not experience before, and forecasts the formation of advanced art and expansion of creative area. Various intellectual activities using computer is developing the whole world with making the infrastructure. Computer in painting work immediately accomplishes the idea of painters, takes part in simulation work, contingency such as abrupt reversal, extraction, twisting, shaking, obscureness, overlapping, etc, and timing to stimulate the creativity of painters, and provides digital formative language which enables new visual experience to the audience. When the change of digital era, the image appeared in my work is shown in 'transfiguration' like drawing. The word, 'transfiguration' does not indicate the completed and fixed real substance but indicate endlessly moving and floating shape. Thus, this concept is opposite to the substantial consideration, so that various concepts which is able to replace this in accordance with the similar cases are also exist such as change, deterioration, mutation, deformity of appearance and morphing which is frequently used in computer as a technical word. These concepts are not clearly classified, and variably and complicatedly related. Transfiguration basically means the denial of "objectivity' and '(continual) stagnation' or deviation from those. This phenomenon is appeared through the all art schools of art ever since the realism is denied in the 19th century. It is called as 'deformation' in case of expressionism, futurism, cubism, etc, in the beginning of the century, which its former indication is mostly preserved within the process of structural deviation and which has the realistic limit which should be preserved. On the contrary, dramatic transfiguration which has been showing in the modern era through surrealism is different in the point that dramatic transfiguration tends to show the deterioration and deviation rather than the preservation of indicated object. From this point, transfiguration coming out from morphing using computer deteriorates and hides the reality and furthermore, it replaces the 'reality'. Moreover, transfiguration is closely approached to the world of fake or 'imaginary' simulation world of Baudrillard. According to Baudrillard, the image hides and deteriorates the reality, and furthermore, expresses 'not existing' to 'imaginary' under the name of transfiguration. Certain reality, that is, image which is absent from the reality is created and overflowed, so that it finally replaces the reality. This is simulation as it is said by Baudrillard. In turn, Georges Bataille discusses about the image which is produced by digital technology in terms of heterologie. Image of heterologie is the visual signal which is established with the media. Image of media is to have the continuous characteristics of produce, extinction, and transformation, and its clear boundary between images becomes meaningless. The meaning of composition, excess, violation, etc of digital image is explained to heterological study or heteologie suggested as important meaning of Georges Bataille who is a heretic philosopher. As the form and image of mutation shows the shape in accordance with mechanical production, heterologie is introduced as very low materialism (or bas materialisme), in this theory. Heterologie as low materialism which is gradually changing is developing as a different concept and analysis because of the change of time in the late 20s century beside high or low meaning. Including my image, all images non-standardizes and transforms the code. However, reappearance and non-standardization of this code does not seem to be simple. The problem of transformation caused by transfiguration which appears in my digital drawing painting, simulation, heterologie, etc, are the continual problems. Moreover, the subject such as existence of human being, distance from the real life, politics and social problems are being extended to actual research and various expressing work. Especially, individual image world is established by digital painting transfiguration technique, and its change and review start to have the durability. The consciousness of observers who look at the image is changing the subject. Together with theoretical research, researchers are to establish the first step to approach to various image change of digital era painting through transfiguration technique using our realistic and historical image.

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Evaluation of Musculoskeletal Disease Risk Assessment and User Satisfaction in Accordance With Using Front-Entry Sitting Toilet for Wheelchair Users (휠체어 사용자의 전면진입착석 화장실 사용에 따른 근골격계질환 위험성 및 만족도 평가)

  • Park, Je-Mo;Hwang, Do-Yeon;Kim, Hee-Dong;Chung, Hyun-Ae;Jung, Hwa-Shik
    • Korean Journal of Occupational Therapy
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    • v.26 no.4
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    • pp.73-84
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    • 2018
  • Objective : The purpose of this study was to promote R&D of toilet design for the disabled by evaluating the Front-entry sitting toilet applied it to actual wheelchair users to examine the possibility of their application as a toilet that is low physical demanding and high satisfaction. Methods : Forty wheelchair users were asked to demonstrate using Front-entry sitting toilet after collecting the general characteristics and their current wheelchair usage information. Musculoskeletal disease risk assessment and user satisfaction were evaluated throughout Rapid Entire Body Assessment(REBA), Quebec Evaluation of Satisfaction with assistive Technology 2.0(QUEST) and subjective opinion questionnaire. Results : Statistical result showed that REBA scores($3.18{\pm}.38$) of Front-Entry Sitting Toilet were significantly lower(z=-5.930, p<.05) than the conventional toilet($6.53{\pm}1.15$). Overall, user satisfaction ratings were high with detailed scores were high in order of durability($4.48{\pm}.62$), safety($4.38{\pm}.63$), necessity($4.33{\pm}.73$) and universal ($4.6{\pm}.61$). Subjective opinion survey showed most were 'it was convenient to not have to rotate(30.8%).' Conclusion : This study found that Front-entry sitting toilet was highly likely to reduce the risk of musculoskeletal disorders and users' satisfactions were high. Through this study, we hope to expand the scope of occupational therapists and contribute to the physical, mental and social health in the daily activities of the people by applying various approaches.

A Study on the Properties and Mix Design of Eco-friendly Concrete Bricks Using Recycled Fine Aggregates (순환잔골재를 활용한 친환경 콘크리트 벽돌의 물성 및 배합설계 연구)

  • Choi, Hyungkook;Yang, Sungchul;Son, Jaeho;Lee, Seunghyun
    • Korean Journal of Construction Engineering and Management
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    • v.25 no.5
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    • pp.32-40
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    • 2024
  • In the construction industry, lack of reliability in the quality of recycled aggregates, harmful substance problems, and negative consumer perceptions limit the expansion of the use of recycled aggregates. In this respect, existing studies mainly focus on the use of recycled coarse aggregates in concrete in consideration of durability. On the other hand, in the case of recycled fine aggregates, not only are there insufficient cases applied to major structures, but the scope of application is very limited due to lack of awareness. Therefore, the main purpose of this study is to present the possibility of their application in bearing and non-bearing wall structures through physical characteristics experiments of concrete bricks for masonry according to various mixing ratios of recycled fine aggregates and cement amounts. To this end, the compressive strength and absorption rate of concrete bricks were measured focusing on the mixing ratio of the recycled fine aggregate and the crushed fine aggregate and the amount of cement. As a result, it is found that it is possible to use 100% of recycled fine aggregate for 200kg/m3 of cement or 25% of crushed fine aggregate mixed with 75% of recycled fine aggregate for the same amount of cement to achieve the compressive strength of 13MPa, witch is one of the quality requirements for concrete bricks for bearing walls. In addition, it is found that to meet the strength of 8MPa, one of the quality requirements for non-bearing walls, it is sufficient to use 100% of the recycled fine aggregate for 100kg/m3 of cement. Through the absorption rate tests, it is also confirmed that the absorption rate of the concrete brick is 13% or less by meeting the required performance criteria. This means that even if recycled fine aggregate is used in the manufacture of concrete bricks, the quality standards required by KS F 4004 (concrete bricks) can be sufficiently met.

Stud and Puzzle-Strip Shear Connector for Composite Beam of UHPC Deck and Inverted-T Steel Girder (초고성능 콘크리트 바닥판과 역T형 강거더의 합성보를 위한 스터드 및 퍼즐스트립 전단연결재에 관한 연구)

  • Lee, Kyoung-Chan;Joh, Changbin;Choi, Eun-Suk;Kim, Jee-Sang
    • Journal of the Korea Concrete Institute
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    • v.26 no.2
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    • pp.151-157
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    • 2014
  • Since recently developed Ultra-High-Performance-Concrete (UHPC) provides very high strength, stiffness, and durability, many studies have been made on the application of the UHPC to bridge decks. Due to high strength and stiffness of UHPC bridge deck, the structural contribution of top flange of steel girder composite to UHPC deck would be much lower than that of conventional concrete deck. At this point of view, this study proposes a inverted-T shaped steel girder composite to UHPC deck. This girder requires a new type of shear connector because conventional shear connectors are welded on top flange. This study also proposes three different types of shear connectors, and evaluate their ultimate strength via push-out static test. The first one is a stud shear connector welded directly to the web of the girder in the transverse direction. The second one is a puzzle-strip type shear connector developed by the European Commission, and the last one is the combination of the stud and the puzzle-strip shear connectors. Experimental results showed that the ultimate strength of the transverse stud was 26% larger than that given in the AASHTO LRFD Bridge Design Specifications, but a splitting crack observed in the UHPC deck was so severe that another measure needs to be developed to prevent the splitting crack. The ultimate strength of the puzzle-strip specimen was 40% larger than that evaluated by the equation of European Commission. The specimens combined with stud and puzzle-strip shear connectors provided less strength than arithmetical sum of those. Based on the experimental observations, there appears to be no advantage of combining transverse stud and puzzle-strip shear connectors.

Rewetting Strategies for the Drained Tropical Peatlands in Indonesia (인도네시아의 배수된 열대 이탄지에 대한 재습지화 전략)

  • Roh, Yujin;Kim, Seongjun;Han, Seung Hyun;Lee, Jongyeol;Son, Yowhan
    • Korean Journal of Environmental Biology
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    • v.36 no.1
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    • pp.33-42
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    • 2018
  • The tropical peatlands have been deforested and converted to agricultural and plantation areas in Indonesia. To manage water levels and increase the overall productivity of crops, canals have been constructed in tropical peatlands. The canals destructed the structure of the tropical peatlands, and increased the subsidence and fire hazard risks in the region. The Indonesian government enacted regulations and a moratorium on tropical peatlands, in order to reduce degradation. A practical method under the regulations of rewetting tropical peatlands was to permit a canal blocking. In this study, four canal blocking projects were investigated regarding their planning, construction priority, design, building material, construction, monitoring, time and costs associated with the canal blockings. In the protected areas, regulations restricted the development of the tropical peatlands areas that were noted as deeper than 3 m, and the administration stopped issuing new concessions for future work projects for this noted criteria of land use. A noted purpose of canal blockings in these areas was to effectuate the restoration of the lands in the region. The main considerations of the restoration efforts were to maintain a durability of the blockings, and to encourage the participation of the area stakeholders. In the case of a concession area, regulations were set into place to restrict clear-cutting and shifting cultivation, and to maintain groundwater level in the tropical peatland. The most significant priorities identified in the canal blocking project were the efficiency and cost-effectiveness of the project. Nevertheless, the drainage of tropical peatlands has been continued. On the basis of a literature review on regulations and rewetting methods in tropical peatlands of Indonesia, we discussed the improvements of the regulations, and adequate canal blockings to serve the function to rewet the tropical peatlands in Indonesia. Our results would help establishing an adequate direction and recommended guideline on viable rewetting methods for the restoration of drained tropical peatlands in Southeast Asia.

A Comparative Study on the Recognition of Urban Agriculture between Urban Farmers and Public Officials (도시농업인과 공무원의 도시농업 인식 비교·평가)

  • Park, Won-Zei;Koo, Bon-Hak;Park, Mi-Ok;Kwon, Hyo-Jin
    • Journal of the Korean Institute of Landscape Architecture
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    • v.40 no.4
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    • pp.90-103
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    • 2012
  • The aim of this study is to be able to understand the problems within the urban agriculture policy promoted by the Government and local autonomous entity base on the comparison of the consciousness of the urban agriculture between urban farmers and public officials and to inquire into the further revitalization scheme in the end. For this purpose, this study drew implications through studying latest trend and the legislation of domestic and foreign urban agriculture and then conducted a questionnaire survey of urban farmers and public officials. Because of this research, the revitalization schemes of urban agriculture are as follows: First, it's necessary to secure the usable arable land, such as the green roof, community garden, as well as urban agriculture park, etc. Second, it is necessary to establish the urban agriculture relations act suited for the actual circumstances of our country and to back up the legislation at an institutional, technological level in terms of a nation in order to secure the durability of urban agriculture. Third, it is advisable to make a proposal about the problems in time of activities for cultivation by forming a network between urban farmers and public officials and to prepare the plan for the active exchange of farming technologies. Fourth, it's necessary to activate the community gardens by supplying the education through cultivation method & its management method, and a variety of urban-agriculture-participation programs. Fifth, it is necessary to set up the specialized and practical education through an institute for landscape architecture. Sixth, it is necessary to induce the spontaneous participation in urban agriculture from urban farmers accompanied by the activities for promotion that are worth arousing urban farmers' interest. Lastly, it is also necessary to establish a legal basis of urban agricultural parks and facilities as well as to promote a search for multilateral policies and their practice so that the further urban agriculture can be stably continued within city boundaries.

Consumer Intention to Purchase Domestic/Foreign Brand Jeans;Beliefs, Attitude, and Individual Characteristics. (국내 및 외국 상표 청바지의 구매의도에 따른 평가기준에 대한 신념과 추구이미지 및 의복태도의 차이연구)

  • 고애란
    • Journal of the Korean Society of Clothing and Textiles
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    • v.18 no.2
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    • pp.263-272
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    • 1994
  • The purpose of this study was to identify factors that might distinguish those who have a high level of Intention to purchase each of domestic, foreign designer and national brand jeans from those who have a low intention in terms of evaluative criteria belief, ideal jeans image and clothing altitude. The sample consisted of 198 male and 197 female students from five universities in Seoul. The questionnnaire consisted of 50 seven-point semantic differential scales dealing with evaluative criteria and ideal jeans image, beliefs about and intention to purchase domestic, foreign designer and foreign national brand jeans and 25 Likert type clothing attitude scales. Based on a series of t-tests the results showed that color and design were the most influencing factor among the evaluative criteria belief, regardless of brand type, while durability, accessory, sewing were the least. Sexy image, brand consciousnees and fashion interest were the important factor that distinguish high intention to purchase group fro)m low intention to purchase group.

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