• Title/Summary/Keyword: 아치형태

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Finite Element Analysis of Gabled Hyperbolic Paraboloid Shells (모임지붕형 쌍곡포물선 쉘구조의 유한요소해석)

  • Kim, Seung-Nam;Yu, Eun-Jong;Rha, Chang-Soon
    • Journal of Korean Association for Spatial Structures
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    • v.12 no.1
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    • pp.87-98
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    • 2012
  • In this study, mechanical role of edge beams in the gabled hyperbolic paraboloid shells was investigated through the comparisons of Finite element(FE) analysis results between the shells structures with and without edge beams. In addition, the effects of roof slope was studied. FE analysis showed that roof loads was directly transferred to the supports at corners by the arch action in the diagonal direction of the shells, thus, less member forces in the edge and ridge beams but higher stresses near supports were estimated than those from the membrane theory. When the edge beams were removed, stress concentration in the shells near the supports and the deflections along the shell edge were increased. Such phenomenon were intensified as the roof slope decrease. Thus, in gable hyperbolic paraboloid shell, the thickness of the shell near supports needs to be increased and careful investigation should be made in the cases when the roof height is low and/or the edge beams are removed.

Life Cycle Assessment of Timber Arch-Truss Bridge by Using Domestic Pinus rigida Glued-Laminated Timber (리기다소나무 구조용 집성재를 활용한 아치 트러스 목조교량의 전과정평가)

  • Son, Whi-Lim;Park, Joo-Saeng;Kim, Kwang-Mo
    • Journal of the Korean Wood Science and Technology
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    • v.42 no.1
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    • pp.1-12
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    • 2014
  • This study carried out life cycle assessment for evaluating environmental impacts of timber Arch-Truss bridge by using domestic Pinus rigida Miller glued-laminated timber throughout life cycle such as extraction, manufacturing, transportation, construction, use, dismantlement, transportation of waste, disposal and recycling. The life cycle GHG (GreenHouse Gas) emissions of the target bridge are 192.56 ton $CO_2$ eq. in 50 years. Especially, the life cycle GHG emissions of concrete used in the target bridge are 82.84 ton $CO_2$ eq. which accounts for 53.02% of the GWP (Global Warming Potential) in extraction and manufacturing stages. The target bridge is constructed of $116.57m^3$ of domestic Pinus rigida Miller glued-laminated timber and used timber has stored 104.72 ton $CO_2$. If an effect of carbon storage in timber is applied to the total GHG emissions of the target bridge, the GHG emissions can be reduced by 54.38%. In the case of substitution effect, if domestic Pinus rigida Miller glued-laminated timber replaces steel manufactures used in other bridge which has the same structure and life span as the target bridge, the GHG emissions in extraction and manufacturing stages can be reduced by 10.26% to 23.91%.

Prediction of Shear Strength in High-Strength Concrete Beams without Web Reinforcement Considering Size Effect (크기효과를 고려한 복부보강이 없는 고강도 콘크리트 보의 전단강도 예측식의 제안)

  • Bae, Young-Hoon;Yoon, Young-Soo
    • Journal of the Korea Concrete Institute
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    • v.15 no.6
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    • pp.820-828
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    • 2003
  • Recent research has indicated that the current ACI shear provision provides unconservative predictions for large slender beams and beams with low level of longitudinal reinforcement, and conservative results for deep beams. To modify some problems of ACI shear provision, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear prism in strut-tie model deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, effective depth, longitudinal reinforcement ratio, concrete compressive strength and shear span-to-depth ratio, about 300 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim &Park's equation and Zsutty's equation. The proposed shear equation is not only simpler than other shear equations, it is but also shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practical shear design.

Inelastic Nonlinear Analysis of Arch Truss and Space Truss Structures (아치 트러스 및 공간 트러스 구조의 비탄성 비선형 거동해석)

  • Kim, Kwang-Joong;Jung, Mi-Roo;Kim, Yeon-Tae;Baek, Ki-Youl;Lee, Jae-Hong
    • Journal of Korean Association for Spatial Structures
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    • v.8 no.5
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    • pp.47-58
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    • 2008
  • Spatial structure is an appropriate shape that resists external force only with in-plane force by reducing the influence of bending moment, and it maximizes the effectiveness of structural system. With this character of the spatial structure, generally long span is used. As a result, large deflection is accompanied from the general frame. the structure is apt to result in a large deflection even though this structure experiences a small displacement in absence. Usually, nonlinear analysis in numerical analysis means geometric nonlinearity and material nonlinearity and complex nonlinearity analysis considers both of them. In this study, nonlinear equation of equilibrium considering geometric nonlinearity as per finite element method was applied and also considered the material nonlinearity using the relation of stress-strain in element. It is applied to find unstable result for tracing load-deflection curve in the numerical analysis tech. especially Arc-length method, and result of the analysis was studied by ABAQUS a general purpose of the finite element program. It is found that the present analysis predicts accurate nonlinear behavior of plane and space truss.

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Measurement of Oblique ion-induced by electric fields secondary electron emission coefficient($\gamma$) and work function ${\Phi}w$ of the MgO protective layer in plane structure AC-PDPs (면방전 구조의 AC-PDP에서 전기장에 의해 기울어진 이온빔에 의한 MgO 보호막의 이차전자방출계수 ($\gamma$)와 일함수 (${\Phi}w$) 측정)

  • Lee, H.J.;Son, C.G.;Yoo, N.L.;Han, Y.G.;Jung, S.H.;Lee, S.B.;Lim, J.E.;Lee, J.H.;Song, K.B.;Oh, P.Y.;Jung, J.M.;Ko, B.D.;Moon, M.W.;Park, W.B.;Choi, E.H.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2005.05a
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    • pp.135-138
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    • 2005
  • 현재 널리 상용되어 있는PDP는 3전극 변방전형이다. 3전극 면장전형 PDP는 주방전이 유전체 아래에 서로 평행하게 위치하고 있는 ITO투명전극 사이에서 발생한다. 따라서 방전시의 전기장은 MgO 보호막 위에서 아치형태로 형성되게 된다. 플라스마 방전 시 전자에 의해 이온화된 이온 입자들은 전기장에 의해 그 방전경로가 정해지게 된다. 물론 전기장은 표면에서 수직이지만 전기장에 의해 가속되어진 이온입자들은 MgO 보호막에 기울어져서 입사하게 된다. 따라서 플라스마 방전시의 이온들의 MgO 보호막으로의 입사각은 매우 다양하다. $\gamma$-FIB (Focused ion beam) 시스템은 이온입사에 의한 물질의 이차전자방출계수 측정에 효과적인 장비이다. 본 실험은 이러한 $\gamma$-FIB 시스템을 이용하여 다양한 각도로 입사하는 이온빔에 의한 MgO 보호막의 이차전자방출계수를 측정하였다. 또한 이온화 에너지가 다른 여러 종류의 불활성 기체를 사용하여 이온의 입사하는 각도에 따른 MgO 보호막의 일함수를 측정하였다. 이온빔의 입사각은 각각 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 변화시키면서 이차전자방출계수 및 일함수를 측정하였다. 이러한 실험을 통해 입사각이 클수록 이차전자방출계수는 증가하고 일수는 감소하는 것을 확인 할 수 있었다.

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Explicit Stress-Erection and Ultimate Load Analysis of Unit STRARCH Frame Considering Geometrically and Materially Nonlinear Characteristics (기하학적 재료적 비선형 특성을 고려한 스트라치 단위부재의 명시적 긴장설치 및 극한하중 해석)

  • Lee, Kyoung-Soo;Han, Sang-Eul
    • Journal of Korean Society of Steel Construction
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    • v.23 no.4
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    • pp.429-438
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    • 2011
  • In this study, the explicit numerical algorithm was proposed to simulate the stress erection process and ultimate-load analysis of the strarch (stressed arch) system. The strarch system is a unique and innovative structural system and member prestress comprising prefabricated plane truss frames erected through a post-tensioning stress erection procedure. The flexible bottom chord, which has sleeve and gap details, is closed by the reaction force of the prestressing tendon. The prestress imposed on the tendon will enable the strarch system to be erected. This post-tensioning process is called "stress erection process." During this process, plastic rigid-body rotation occurs to the flexible top chord due to the excessive amount of plastic strain, and the structural characteristic is unstable. In this study, the dynamic relaxation method (DRM) was adopted to calculate the nonlinear equilibrium equation of the system, and a displacement-based finite-element-formulated filament beam element was used to simulate the nonlinear behavior of the top chord sections of the strarch system. The section of the filament beam element was composed by the amount of filaments, which can be modeled by various material models. The Ramberg-Osgood and bilinear kinematic elastic plastic material models were formulated for the nonlinear material behaviors of the filaments. The numerical results that were obtained in the present study were compared with the experiment results of the stress erection and with the results of the ultimate-load analysis of the strarch unit frame. The results of the present studies are in good agreement with the previous experiment results, and the explicit DRM enabled the analysis of the post-buckling behaviors of the strarch unit frame.

Theoretical Analysis of Embankment Loads Acting on Piles (성토지지말뚝에 작용하는 연직하중의 이론해석)

  • 홍원표;이재호;전성권
    • Journal of the Korean Geotechnical Society
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    • v.16 no.1
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    • pp.131-143
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    • 2000
  • Several theoretical analyses are performed to predict the vertical load on embankment piles with cap beams. The piles are installed in a row in soft ground below the embankment and the cap beams are placed perpendicular to the longitudinal axis of the embankment. Two failure mechanisms such as the soil arching failure and the punching shear failure are investigated according to the failure pattern in embankment on soft ground supported by piles with cap beams. The soil arching can be developed when the space between cap beams is narrow and/or the embankment is high enough. In the investigation of the soil arching failure, the stability in the crown of the arch is compared with that above the cap beams. The factors affecting the load transfer in the embankment fill by soil arching are the space between cap beams, the width of cap beams and the soil parameters of the embankment fill. The portion of the embankment load carried by cap beams decreases with increment of the space between cap beams, while it increases with the embankment height, the width of cap beams, the internal friction angle and cohesion of the embankment fill. Thus, the factors affecting load transfer in embankment should be appropriately decided in order to maximize the effect of embankment load transfer by piles.

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A Study on the Original Form of the Chwihyanggyo Bridge and the Creation of the Hyangwonjeong in Gyeongbokgung Palace (경복궁(景福宮) 향원정(香遠亭)의 조성시기(造成時期)와 취향교(醉香橋)의 원형(原形))

  • Nam, Ho Hyun;Kim, Tae Min
    • Korean Journal of Heritage: History & Science
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    • v.51 no.4
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    • pp.192-207
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    • 2018
  • The Hyangwonjeong and Chwihyanggyo located in the back garden of Gyeongbokgung Palace have mainly been investigated by referring to historical records about the reign of King Gojong and various drawings thought to have been made in the late Joseon period. Because the current Chwihyanggyo was rebuilt temporarily after being burned to the ground during the Korean War, its form and the location of its reconstruction are not grounded on any accurate historical investigation. Although there are some photos of the Chwihyanggyo that were taken between the end of the Joseon period and the Japanese colonial era, there is no information about the photographer or when they were taken, and it is hard to see which photos show the original Chwihyanggyo Bridge with them. The Cultural Heritage Administration, which is currently promoting the restoration of the Chwihyanggyo, has recognized this problem and initiated research on the matter. In 2017, an excavation survey successfully identified the original location of the Chwihyanggyo, as well as that of Hyangwonji Gado (假島), and the shape of the first foundation stone in the pier. With these findings it was possible to infer the ways in which the Chwihyanggyo has changed over the years. Moreover, by measuring the AMS (Accelerator Mass Spectrometer) of the samples collected in the mounding layer of the Gado where the Hyangwonjeong is located, it was discovered that the Hyangwonjeong was constructed sometime after the Imjin waeran (Japanese Invasion of Korea in 1592), which means that the theory that 'the late Joseon Hyangwonjeong was not the former early Josenn Chwirojeong' is groundless. Judging by the materials found to date, we can reasonably assume that the Chwihyanggyo and Hyangwonjeong must have been built around the same time that Geoncheonggung Palace was founded in the late Joseon period.

Cellular Responses and Morphological Changes of RDX-degrading Bacterium, Pseudomonas sp. HK-6 Exposed by Explosive Hexahydro-1,3,5-triaitro-1,3,5-triazine (RDX). (폭약 Hexahydro-1,3,5-trinitro-1,3,5-triazine(RDX)에 노출된 분해세균 Pseudomonas sp. HK-6의 세포반응과 형태변화)

  • 장효원;강형일;김치경;오계헌
    • Microbiology and Biotechnology Letters
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    • v.31 no.1
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    • pp.75-82
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    • 2003
  • The cellular responses of RDX-degrading bacterium, Pseudomonas sp. HK-6 to explosive hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) were examined. Strain HK-6 grown at different RDX concentrations was found to demonstrate the survival rate in proportional to the rate of the stress shock proteins produced in this bacterium. Analysis of total cellular fatty acid acids showed that lipids 10:0 iso and 14:1 $\omega$5c/$\omega$5t increased approx three times in strain HK-6 grown on RDX media than TSA media. SDS-PAGE and Western blot using anti-DnaK and GroEL revealed that several stress shock proteins including 70 kDa DnaK and 60 kDa CroEL were newly synthesized in strain HK-6 exposed to different RDX concentrations in exponentially growing cultures. 2-D PAGE of soluble protein fractions from the culture of HK-6 exposed to RDX demonstrated that approximately 300 spots were observed on the silver stained gel ranging from pH 3 to pH 10. As a result, 10 spots were significantly induced and expressed in response to RDX. Scanning electron microscopy fur the cells treated with 0.135 mM RDX for 12 hrs showed the presence of perforations and irregular rod shapes with wrinkled surfaces.

Analysis Model of the Stress Ribbon Bridge considering the Construction Stage (시공단계가 고려된 스트레스 리본 교량의 해석 모델)

  • Yun, Kyung-Min;Kim, Kee-Dong;Lee, Chin-Ok;Lim, Nam-Hyoung
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.15 no.11
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    • pp.6898-6905
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    • 2014
  • A stress ribbon bridge is a PSC structure that behaves as a reverse arch structure due to post-tensioned thin deck of the catenary type. In foreign countries, the stress ribbon bridge is recognized as the minimum destruction of nature and beautiful bridge, and has many construction examples as pedestrian and car bridges. On the other hand, there have been few studies in Korea. In this study, the FE Analysis model was established for different construction stages considering the nonlinear and time-dependent behaviors. The FE model was verified by a comparison with the numerical results and the behavior was analyzed for the different construction stages.