• 제목/요약/키워드: Frame Stress

검색결과 653건 처리시간 0.021초

Crack propagation in flexural fatigue of concrete using rheological-dynamical theory

  • Pancic, Aleksandar;Milasinovic, Dragan D.;Goles, Danica
    • Computers and Concrete
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    • 제27권1호
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    • pp.55-62
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    • 2021
  • The concrete fatigue analysis can be performed with the use of fracture mechanics. The fracture mechanics defines the fatigue crack propagation as the relationship of crack growth rate and stress intensity factor. In contrast to metal, the application of fracture mechanics to concrete is more complicated and therefore many authors have introduced empirical expressions using Paris law. The topic of this paper is development of a new prediction of fatigue crack propagation for concrete using rheological-dynamical analogy (RDA) and finite element method (FEM) in the frame of linear elastic fracture mechanics (LEFM). The static and cyclic fatigue three-point bending tests on notched beams are considered. Verification of the proposed approach was performed on the test results taken from the literature. The comparison between the theoretical model and experimental results indicates that the model proposed in this paper is valid to predict the crack propagation in flexural fatigue of concrete.

강판 형상비 및 판폭두께비에 따른 강판전단벽의 변형모드 및 이력특성 (Hysteretic Characteristics and Deformation Modes of Steel Plate Shear Walls According to Aspect Ratios and Width-to-Thickness Ratios)

  • 신동현
    • 한국공간구조학회논문집
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    • 제24권1호
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    • pp.37-45
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    • 2024
  • Steel plate shear walls (SPSWs) have been recognized as an effective seismic-force resisting systems due to their excellent strength and stiffness characteristics. The infill steel plate in a SPSW is constrained by a boundary frame consisting of vertical and horizontal structural members. The main purpose of this study was to investigate deformation modes and hysteretic characteristics of steel plate shear walls (SPSWs) to consider the effects of their aspect ratios and width-to-thicness ratios. The finite element model (FEM) was establish in order to simulate cyclic responses of SPSWs which have the two-side clamped boundary condition and made of conventional steel grade. The stress distribution obtained from the FEA results demonstrated that the principal stresses on steel plate with large thickness-to-width ratio were more uniformly distributed along its horizontal cross section due to the formation of multiple struts.

Spectral analysis of semi-actively controlled structures subjected to blast loading

  • Ewing, C.M.;Guillin, C.;Dhakal, R.P.;Chase, J.G.
    • Structural Engineering and Mechanics
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    • 제33권1호
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    • pp.79-93
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    • 2009
  • This paper investigates the possibility of controlling the response of typical portal frame structures to blast loading using a combination of semi-active and passive control devices. A one storey reinforced concrete portal frame is modelled using non-linear finite elements with each column discretised into multiple elements to capture the higher frequency modes of column vibration response that are typical features of blast responses. The model structure is subjected to blast loads of varying duration, magnitude and shape, and the critical aspects of the response are investigated over a range of structural periods in the form of blast load response spectra. It is found that the shape or length of the blast load is not a factor in the response, as long as the period is less than 25% of the fundamental structural period. Thus, blast load response can be expressed strictly as a function of the momentum applied to the structure by a blast load. The optimal device arrangements are found to be those that reduce the first peak of the structural displacement and also reduce the subsequent free vibration of the structure. Semi-active devices that do not increase base shear demands on the foundations in combination with a passive yielding tendon are found to provide the most effective control, particularly if base shear demand is an important consideration, as with older structures. The overall results are summarised as response spectra for eventual potential use within standard structural design paradigms.

핵폐기장 유치에 대한 텔레비전 뉴스 프레임 분석 -KBS, MBC의 전국 및 지역(전북지역) 뉴스를 중심으로- (Framing an Issue of Building a Nuclear Waste Site on Television News)

  • 나미수
    • 한국언론정보학보
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    • 제26권
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    • pp.157-208
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    • 2004
  • 본 연구는 2003년도 중요란 국책사업의 하나로서 첨예한 사회적 갈등이 나타났던 핵폐기장 유치 이슈를 텔레비전 뉴스보도가 어떠한 시각에서 다루고 해석, 평가함으로써 이슈에 대한 성격을 어떻게 규정하고 있는지 살펴보고자 하였다. 이를 위해 본 연구는 핵폐기장 유치선언이 있던 2003년 7월 11일부터 유치 재검토가 발표된 12월 10일까지 5개월 동안 보도된 핵폐기장 유치이슈에 대한 KBS, MBC 저녁종합뉴스의 전국 및 지역(전북지역) 뉴스에 대한 프레임분석을 실시하였다. 분석결과 중요한 국책사업으로서 사회적 논란이 많았던 핵폐기장 유치 이슈는 길 등의 원인과 해결보다는 주민들의 시위와 사회적 혼란만 부각시키는 양상을 보였다. 따라서 갈등의 근본원인이자 이슈의 보다 본질적인 사안이라 할 수 있는 선정 절차상의 정당성 문제라든가 위도지역의 지질 적합성, 안전성 문제, 에너지 정책 등의 문제는 제대로 다루어지지 않았다. 결국 텔레비전 뉴스보도에서 핵폐기장 유치이슈는 국가정책적 이슈라기보다는 지역 내 집단간 분쟁으로 그 성격이 규정되고 있음을 알 수 있다.

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Investigation on the performance of a new pure torsional yielding damper

  • Mahyari, Shahram Lotfi;Riahi, Hossein Tajmir;Esfahanian, Mahmoud Hashemi
    • Smart Structures and Systems
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    • 제25권5호
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    • pp.515-530
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    • 2020
  • A new type of pure torsional yielding damper made from steel pipe is proposed and introduced. The damper uses a special mechanism to apply force and therefore applies pure torsion in the damper. Uniform distribution of the shear stress caused by pure torsion resulting in widespread yielding along pipe and consequently dissipating a large amount of energy. The behavior of the damper is investigated analytically and the governing relations are derived. To examine the performance of the proposed damper, four types of the damper are experimentally tested. The results of the tests show the behavior of the system as stable and satisfactory. The behavior characteristics include initial stiffness, yielding load, yielding deformation, and dissipated energy in a cycle of hysteretic behavior. The tests results were compared with the numerical analysis and the derived analytical relations outputs. The comparison shows an acceptable and precise approximation by the analytical outputs for estimation of the proposed damper behavior. Therefore, the relations may be applied to design the braced frame system equipped by the pure torsional yielding damper. An analytical model based on analytical relationships was developed and verified. This model can be used to simulate cyclic behavior of the proposed damper in the dynamic analysis of the structures equipped with the proposed damper. A numerical study was conducted on the performance of an assumed frame with/without proposed damper. Dynamic analysis of the assumed frames for seven earthquake records demonstrate that, equipping moment-resisting frames with the proposed dampers decreases the maximum story drift of these frames with an average reduction of about 50%.

Improvement, analytical verification and application of RC frame beam-column joint models

  • Fan, Guoxi;Wang, Debin;Jia, Jing
    • Earthquakes and Structures
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    • 제14권3호
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    • pp.273-283
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    • 2018
  • Previous experimental researches indicate that reinforced concrete beam-column joints play an important role in the mechanical properties of moment resisting frame structures, so as to require proper design. In order to get better understanding of the beam-column joint performance, a rational model needs to be developed. Based on the former considerations, two typical models for calculating the shear carrying capacity of the beam-column joint including the inelastic reinforced concrete joint model and the softened strut-and-tie model are selected to be introduced and analyzed. After examining the applicability of two typical models mentioned earlier to interior beam-column joints, several adjustments are made to get better predicting of the test results. For the softened strut-and-tie model, four adjustments including modifications of the depth of the diagonal strut, the inclination angle of diagonal compression strut, the smeared stress of mild steel bars embedded in concrete, as well as the softening coefficient are made. While two adjustments for the inelastic reinforced concrete joint model including modifications of the confinement effect due to the column axial load and the correction coefficient for high concrete are made. It has been proved by test data that predicted results by the improved softened strut-and-tie model or the modified inelastic reinforced concrete joint model are consistent with the test data and conservative. Based on the test results, it is also not difficult to find that the improved beam-column joint model can be used to predict the joint carrying capacity and cracks development with sufficient accuracy.

PIV System for the Flow Pattern Anaysis of Artificial Organs ; Applied to the In Vitro Test of Artificial Heart Valves

  • Lee, Dong-Hyeok;Seh, Soo-Won;An, Hyuk;Min, Byoung-Goo
    • 대한의용생체공학회:의공학회지
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    • 제15권4호
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    • pp.489-497
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    • 1994
  • The most serious problems related to the cardiovascular prothesis are thrombosis and hemolysis. It is known that the flow pattern of cardiovascular prostheses is highly correlated with thrombosis and hemolysis. Laser Doppler Anemometry (LDA) is a usual method to get flow pattern, which is difficult to operate and has narrow measure region. Particle Image Velocimetry (PIV) can solve these problems. Because the flow speed of valve is too high to catch particles by CCD camera, high-speed camera (Hyspeed : Holland-Photonics) was used. The estimated maximum flow speed was 5m/sec and maximum trackable length is 0.5 cm, so the shutter speed was determined as 1000 frames per sec. Several image processing techniques (blurring, segmentation, morphology, etc) were used for the preprocessing. Particle tracking algorithm and 2-D interpolation technique which were necessary in making gridrized velocity pronto, were applied to this PIV program. By using Single-Pulse Multi-Frame particle tracking algorithm, some problems of PIV can be solved. To eliminate particles which penetrate the sheeted plane and to determine the direction of particle paths are these solving methods. 1-D relaxation fomula is modified to interpolate 2-D field. Parachute artificial heart valve which was developed by Seoul National University and Bjork-Shiely valve was testified. For each valve, different flow pattern, velocity profile, wall shear stress and mean velocity were obtained.

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기둥-보 용접접합부의 보단부 스캘럽형상과 탄소성 거동에 관한 실험적 연구 - 600MPa(SM570TMC)의 경우 - (Study on Elasto-Plastic Behavior of Column to Beam Connection with 600MPa High Performance Steel(SM 570 TMC))

  • 김종락;김성배;권준엽
    • 한국강구조학회 논문집
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    • 제20권6호
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    • pp.691-700
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    • 2008
  • 최근 건축구조물의 구조는 다양한 형태의 복잡한 건축물이 구현되고 있다. 이러한 건축구조물의 복합 다양성은 수평저항력에 효과적 으로 저항하기 위해 강재와 접합부의 요구성능이 점차 중요시되고 있다. 접합부는 형상의 불연속과 응력집중 및 다축응력 등이 발생되는 부분으로 골조전체의 변형능력에 큰 영향을 미치고 강성과 인성을 결정하는 중요부위이다. 본 연구에서는 고강도 고성능강 적용에 대한 인성평가를 위해 구조체의 기둥-보 접합부를 빌트업 H형강의 T형 기둥-보 용접접합부로 제작하여 실대실험을 수행하였다. 실험변수는 응력집중 및 형상의 불연속이 발생되는 보 스캘럽을 중심으로 논스캘럽(Non-Scallop)과 종래형 스캘럽, 개량형 스캘럽으로 제작하여 스캘럽 형상이 접합부의 인성에 미치는 영향과 고강도 고성능강의 건축구조물 적용성을 평가하였다. 기존의 기둥-보 용접접합부에 대한 평가방법을 기초로 최근 개발된 고강도 고성능강의 초고층 건축물 적용을 위한 내진설계 자료를 제시하였다.

서브모델링 기법을 이용한 철도차량 복합재 대차프레임의 금속재 체결부 볼트 위치 최적화 해석 연구 (A Study on Optimum Design Analysis of Bolt Locations for Metal Joint Parts of Railway Composite Bogie Frames using Sub-modeling Method)

  • 김준환;신광복;고희영;김정석
    • Composites Research
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    • 제23권6호
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    • pp.19-25
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    • 2010
  • 본 논문은 유리섬유/에폭시 4-매 주자직 적층 복합재와 PVC 폼 코어로 제작된 철도차량용 복합재 대차프레임의 금속재 체결부 볼트 위치 최적화 연구에 대해 서술했다. 최적화 해석은 APDL(Ansys Parameter Design Language)을 이용한 서브모델링 기법을 적용하였으며 부분문제 근사방법에 의한 최적화를 수행하였다. 이때, 최적화 해석에 적용된 서브모델링 기법은 관심영역을 포함한 부분모델에 대한 계산을 재수행 함으로써 해석에 소요되는 시간을 절약하고 상세한 결과를 도출 할 수 있다. 복합재 대차프레임의 구조해석은 JIS E 4207에 의거하여 수행하였다. 서브모델링 기법을 적용한 복합재 대차프레임의 최적화 해석은 전체모델에 대한 결과에 비해 요소망 밀도의 조절을 통한 해석시간 절약과 상세한 결과를 얻을 수 있으며, 또한 볼트위치의 최적화로 인해 보다 낮은 Von-Mises 응력값이 나타남을 확인하였다.

소방.가스안전용 헬멧의 최적설계에 관한 연구 (A Study on the Optimized Design of the Helmets for Fire and Gas Safety)

  • 조승현;김도현;김청균
    • 한국가스학회지
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    • 제12권3호
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    • pp.24-30
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    • 2008
  • 본 본문에서는 유한요소법과 다구찌의 최적설계법을 사용하여 헬멧의 모체 구조물에 대한 응력과 변형률 특성을 소재의 특성치, 헬멧의 두께, 보강뼈대의 수량과 두께의 함수로 각각 해석하였다. 소방관과 가스 작업자의 안전성 확보를 위해 필요한 헬멧에 대한 최적화 설계연구는 외부에서 작용하는 충격력에 대한 강도안전성을 높이고, 충격에너지 흡수력을 강화시킬 수 있는 데이터를 제공하기 때문에 대단히 중요하다. 따라서 헬멧 모체 구조물의 균일한 두께는 헬멧 모체의 중량을 감축하고 변형률 에너지를 높여 준다는 측면에서 줄여야 하지만, 헬멧의 보강뼈대의 수량과 두께는 헬멧의 충격강도를 높여준다는 측면에서 늘려주는 최적화 설계가 추진되어야 헬멧의 안전성은 확보된다는 해석결과를 제시하였다.

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