• Title, Summary, Keyword: 조화하중

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Laterally Loaded Soil-Pile Interaction Analysis in Frequency Domain (횡하중을 받는 지반-말뚝 상호작용계의 동적 주파수 응답해석)

  • 김문겸;임윤묵;김민규;조석호
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.13 no.4
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    • pp.437-448
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    • 2000
  • In this study, a numerical analysis method for soil-pile interaction in frequency domain problem is presented. The total soil-pile interaction system is divided into two parts so called near field and far field. In the near field, beam elements are used lot a pile and plain strain finite elements for soil. In the far field, dynamic fundamental solution for multi-layered half planes based on boundary element formulation is adopted lot soil. These two fields are coupled using FE-BE coupling technique. In order to verify the proposed soil-pile interaction analysis, the dynamic responses of pile on multi-layered half planes are simulated and the results are compared with the experimental results. Also, various numerical analyses of piles considering different conditions of soil-pile interaction system are performed to examine the dynamic behavior of the system. It has been found that the developed method which satisfies the radiation conditions of multi-layered half planes can be applied to various structure systems effectively in frequency domain.

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Detecting Chaotic Motions of a Piecewise-Linear System in the Noisy Fields by Mean Poincare Maps (평균 포인케어맵을 이용한 Noisy Field에서의 chaos거동의 검출방법)

  • 마호성
    • Computational Structural Engineering
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    • v.10 no.4
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    • pp.239-249
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    • 1997
  • The method to distinguish chaotic attractors in the perturbed response behaviors of a piecewise-linear system under combined regular and external randomness is provided and examined. In the noisy fields such as the ocean environment, excitation forces induced by wind, waves and currents contain a finite degree of randomness. Under external random perturbations, the system responses are disturbed, and consequently chaotic signatures in the response attractors are not distinguishable, but rather look just random-like. Mean Poincare map can be utilized to identify such chaotic responses veiled due to the random noise by averaging the noise effect out of the perturbed responses. In this study, the procedure to create mean Poincare map combined with the direct numerical simulations is provided and examined. It is found that mean Poincare maps can successfully distinguish chaotic attractors under stochastic excitations, and also can give the information of limit value of noise intensity with which the chaos signature in system responses vanishes.

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Dynamic Buckling Characteristics of Arch Structures Considering Geometric Nonlinearity (기하학적 비선형을 고려한 정현형 아치 구조물의 동적 좌굴 특성)

  • 윤태영;김승덕
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.492-497
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    • 2003
  • The dynamic instability for snapping phenomena has been studied by many researches. There is few paper which deal with the dynamic buckling under the load with periodic characteristics, and the behavior under periodic excitation is expected the different behavior against STEP excitation. We investigate the fundamental mechanisms of the dynamic instability when the sinusoidal shaped arch structures subjected to sinusoidal distributed excitation with pin-ends. In this study, the dynamic direct snapping of shallow arches is investigated under not only STEP load excitation but also sinusoidal harmonic excitations, applied in the up-and-down direction. The dynamic nonlinear responses are obtained by the numerical integration of the geometrically nonlinear equations of motion, and examined by the Fourier spectral analysis in order to get the frequency-dependent characteristics of the dynamic instability for various load levels.

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Theoretical Prediction of Noise Generated by Unsteady Loading of Marine Propellers (프로펠러의 비정상하중에 의해 발생하는 소음의 이론적 추정)

  • Chang-Sup Lee;Chung-Ho Cho
    • Journal of the Society of Naval Architects of Korea
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    • v.36 no.3
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    • pp.29-40
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    • 1999
  • A numerical method in frequency domain for the analysis of the acoustic wave equation governing the sound field generated by a non-cavitating propeller under a steady of unsteady loading condition is developed. Theory shows that only multiples of the blade passage frequency exist and that the wave number consists of the frequency component due to the nonuniformity of the wake and the Doppler effect originated from the rotation of the blades. Correlation with experiments for a two bladed propeller, designed to be load-free at a particular advance speed, indicate that the thickness effect can be significant in steady case, but can be negligible compared to the unsteady loading effect.

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Detection of Structural Damage from Measured Acceleration (측정 가속도를 사용한 구조 손상 진단)

  • 곽임종
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.144-151
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    • 1997
  • 구조물로부터 측정된 가속도 시간이력을 이용하여 구조손상을 찾아내고 평가하는 기법을 제시하였다. 구조계의 손상을 찾아내는 알고리즘의 주요한 수단으로써 parametric system identification 방법을 사용하였고 매개변수화된 구조물의 최적 매개변수를 추정하기 위해 구속된 비선형 최적화기법을 사용하였다. 손상된 부재를 분리하기 위한 방법으로서 적합적 매개변수 모음법을 적용하였고 손상의 정도를 통계적으로 평가하기 위하여 측정된 가속도 시간이력에 time window 기법을 적용하였다. 가속도 이력 측정에 있어서의 불충분성과 측정오차를 고려하여 알고리즘을 개발하였고, 조화진동하중으로 구조물을 가진하여 구조 손상을 진단하는 수치모의 실험을 실시하였다.

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Shape Optimal Design of Anti-Vibration Rubber Assembly to Reduce the Vibration of a Tractor Cabin (트랙터 캐빈의 진동저감을 위한 방진고무의 형상최적설계)

  • Choi, Hyo-Joon;Lee, Sang-Hoon
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.19 no.4
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    • pp.657-663
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    • 2018
  • In this study, shape optimization was performed to improve the vibration isolation capability of an anti-vibration rubber assembly, which is used in the field option cabin of agricultural tractors. A uniaxial tension test and biaxial tension test were performed to characterize the hyper-elastic material properties of rubber, and the data were used to calibrate the material model used in the finite element analyses. A field test was performed to quantify the input excitation from the tractor and the output response at the cabin frame. To account for the nonlinear behavior of rubber, static analyses were performed and the load-displacement curve of rubber was derived. The stiffness of the rubber was calculated from this curve and input to the harmonic analyses of the cabin. The results were verified using the test data. Taguchi's parameter design method was used to find the optimal shape of the anti-vibration rubber assembly, which indicated a shape with reduced stiffness. The vibration of the cabin frame was reduced by the optimization by as much as 35% compared to the initial design.

Dynamic Load Factor for Floor Vibration due to Lively Concerts (공연하중에 의한 바닥진동 설계용 동하중계수)

  • Hong, Kap Pyo;Yoon, Kwang Sup
    • Journal of Korean Society of Steel Construction
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    • v.14 no.6
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    • pp.721-728
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    • 2002
  • Modern structrues are being built using high-strength and light-weight construction materials resulting in decreased structural mass and damping properties. Rhythmic activities such as jumping, dancing and clapping during lively concerts can produce excessive vibration of steel structures. In this study, dynamic load factors that occur during lively concerts were presented through vibration test and real-time monitoring of an existing concert hall. The vibration test included modal analysis and jumping test according to the forcing frequencies and the number of participants. Dynamic load foactors were acquired directly from peak acceleration responses of each harmonics. Comparing NBCC 1995, the 3rd harmonic must be included in the design of concert halls. Dynamic load factors must be increased as a result of the vibration test.

Dynamic Analysis of ROV Cable with the Coupling of Ship Motion (선체 운동을 고려한 ROV 케이블의 연성 동력학 해석)

  • Cho, Kyu-Nam;Song, Ha-Cheol
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.94-98
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    • 2003
  • Remotely Operated Vehicle. ROV is a new concept equipment being made to replace the manned systems for investigating the deep sea environment. This paper presents the dynamic cable response during ROV launching considering the coupling effects of ship motion. By the harmonic response analysis, the variations of cable tensions were obtained. Harmonic forces in head/beam sea states were calculated by the concept of relative acceleration which obtained by ship motion analysis.

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Experimental Evaluation of Design Parameters for TLCD and LCVA (TLCD와 LCVA의 설계파라미터에 대한 실험적 평가)

  • Lee, Sung-Kyung;Min, Kyung-Won;Park, Ji-Hun
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.5
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    • pp.403-410
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    • 2009
  • In this paper, damping coefficients and effective masses of tuned liquid-type column dampers were quantitatively evaluated based on experimental results by using system identification technique. First, shaking table tests were performed for two types of tuned liquid-type column dampers. Then, the dynamic characteristics of dampers used in this study were experimentally grasped from harmonic wave excitation testing results of the dampers with various water level. Finally, damping ratios and effective masses of the dampers with varying water level were quantitatively evaluated from minimizing the errors between numerical and experimental results. It was confirmed from system identification results that damping ratio and effective mass are decreased as the water level of dampers is increased.

An Experimental Study on the Ultimate Strength and Deformation Capacity of Composite Beams with Eccentric Web Openings (편심유공합성보의 종국내력 및 변형능력에 관한 실험적 연구)

  • Choi, San Ho;Seo, Seong Yeon
    • Journal of Korean Society of Steel Construction
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    • v.12 no.5
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    • pp.595-604
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    • 2000
  • Web openings of large beams provide space for wiring, piping, and duct work to provide for proper drainage, pipes and duct must be slightly sloped with the attendant result that all web openings can not be centered on the centroidal axes of the beams. Test specimens are made for opening-depth to beam-depth ratio of 0.5 and for eccentricities of the opening center line of 10% from middepth of the beam because of the proximity of the opening edge to the flange. In this paper, available test results and theories relating to the strength of composite beams having eccentric rectangular openings are surveyed and experiments were carried out to examine the structural behaviors. In all the tests in this paper good agreement is demonstrated with maximum loads measured in tests, and observed failure modes Furthermore, compared with analytical values and experimental values of interaction diagram between moment and shear capacity were safed as it is scattered with outer part of the analytical values.

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