• Title, Summary, Keyword: 준 정적 실험

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Peridynamic Modeling for Crack Propagation Analysis of Materials (페리다이나믹 이론 모델을 이용한 재료의 균열 진전 해석)

  • Chung, Won-Jun;Oterkus, Erkan;Lee, Jae-Myung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.31 no.2
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    • pp.105-114
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    • 2018
  • In this paper, the computer simulations are carried out by using the peridynamic theory model with various conditions including quasi-static loads, dynamic loads and crack propagation, branching crack pattern and isotropic materials, orthotropic materials. Three examples, a plate with a hole under quasi-static loading, a plate with a pre-existing crack under dynamic loading and a lamina with a pre-existing crack under quasi-static loading are analyzed by computational simulations. In order to simulate the quasi-static load, an adaptive dynamic relaxation technique is used. In the orthotropic material analysis, a homogenization method is used considering the strain energy density ratio between the classical continuum mechanics and the peridynamic. As a result, crack propagation and branching cracks are observed successfully and the direction and initiation of the crack are also captured within the peridynamic modeling. In case of applying peridynamic used homogenization method to a relatively complicated orthotropic material, it is also verified by comparing with experimental results.

Detection of Unknown Malicious Scripts Using Static Analysis (정적 분석을 이용한 알려지지 않은 악성 스크립트 감지)

  • Lee, Seong-Uck;Bae, Byung-Woo;Lee, Hyong-Joon;Cho, Eun-Sun;Hong, Man-Pyo
    • The KIPS Transactions:PartC
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    • v.9C no.5
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    • pp.765-774
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    • 2002
  • Analyzing the code using static heuristics is a widely used technique for detecting unknown malicious codes. It decides the maliciousness of a code by searching for some fragments that had been frequently found in known malicious codes. However, in script codes, it tries to search for sequences of method calls, not code fragments, because finding such fragments is much difficult. This technique makes many false alarms because such method calls can be also used in normal scripts. Thus, static heuristics for scripts are used only to detect malicious behavior consisting of specific method calls which is seldom used in normal scripts. In this paper. we suggest a static analysis that can detect malicious behavior more accurately, by concerning not only the method calls but also parameters and return values. The result of experiments show that malicious behaviors, which were difficult to detect by previous works, due to high false positive, will be detected by our method.

Static Behavior Analysis of Spillway Pier for Dam Safety Evaluation (댐 안전성 평가를 위한 여수로 피어부의 정적 거동 분석)

  • Jang, Bong-Seok;Lim, Jeong-Yeul;Lee, Myung-Kue;Lee, Hyung-Jun
    • Journal of the Korea Concrete Institute
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    • v.19 no.1
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    • pp.11-18
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    • 2007
  • Seismic performance evaluation for dam safety evaluation has been continually conducted. However the behavior analysis for the spillway pier which is known as the weak point of dam is seldom reported. Therefore, this study performed the static loading tests for a prototype structures as elementary tests for the final seismic performance evaluation of dam safety. The prototype of pier structure has 1/20 scale and it adopts to strength model. And cracking loads and ultimate loads of real structures are calculated through numerical analysis using commercial FEM program (ABAQUS). The results of this study show some difference between the results of prototype tests and the results of numerical analysis. Also, the ultimate and cracking loads can be estimated through the prototype loading test and numerical analysis.

Planar Dynamics of the Electric Charaged Particles (전기전하의 평면계 동특성)

  • 강수준;박기순
    • Journal of KSNVE
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    • v.9 no.3
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    • pp.621-628
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    • 1999
  • The fundamental dynamic properties of the planar electric charged particle are investigated experimentally. The experiment is conducted using electric charged spheres(4 table tennis balls with conductive surfaces) suspended by insulating strings to cancel the gravitational force. The measurements of the equilibrium angles and the natural frequencies of oscillation agree well with the analytical predictions with some error, respectively.

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Quasi-Static Test for Seismic Performance of Circular Hollow RC Bridge Pier (원형 중공 콘크리트 교각의 내진성능에 대한 준정적 실험)

  • 정영수;한기훈;이강균;이대형
    • Journal of the Earthquake Engineering Society of Korea
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    • v.3 no.2
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    • pp.41-54
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    • 1999
  • Because of relatively heavy dead weight of concrete itself and unavoidable heat of massive concrete in bridge piers, circular hollow columns are widely used in Korean highway bridges. Since the occurrence of 1995 Kobe earthquake, there have been much concerns about seismic design for various infrastructures, inclusive of bridge structures. It is, however, understood that there are not much research works for nonlinear behavior of circular hollow columns subjected to eqrthquake motions. The objective of this experimental research is to investigate nonlinear behavior of circular hollow reinforced concrete bridge piers under the quasi-static cyclic load, and then to enhance their ductility by strengthening the plastic hinge region with glassfiber sheets. Particularly for this test, constant 10 cyclic loads have been repeatedly actuated to investigate the magnitude of strength degradation for the displacement ductility factor. Important test parameters are seismic design, confinement steel ratio, axial force and load pattern. It is observed from quasi-static tests for 7 bridge piers that the seismically designed columns and the retrofitted columns show better performance than the nonseismically designed colums, i.e. about 20% higher for energy dissipation capacity and about 70% higher for curvatures.

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The Evaluation of Seismic Performance for Concrete-filled Steel Piers (콘크리트 충전 강교각의 내진 성능 평가)

  • 정지만;장승필;인성빈
    • Journal of the Earthquake Engineering Society of Korea
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    • v.6 no.5
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    • pp.53-58
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    • 2002
  • A recent development, a concrete-filled steel(CFS) pier is an alternative to a reinforced concrete bridge pier in an urban area, because of its fast construction and excellent ductility against earthquakes. The capacity of CFS piers has not been used to a practical design, because there is no guide of a seismic design for CFS piers. Therefore, the guide of a seismic design value is derived from tests of CFS piers in order to apply it to a practical seismic design. Steel piers and concrete-filled steel piers are tested with constant axial load using quasi-static cyclic lateral load to check ductile capacity and using the real Kobe ground motion of pseudo-dynamic test to verify seismic performance. The results prove that CFS piers have more satisfactory ductility and strength than steel piers and relatively large hysteretic damping in dynamic behaviors. The seismic performance of steel and CFS piers is quantified on the basis of the test results. These results are evaluated through comparison of both the response modification factor method by elastic response spectrum and the performance-based design method by capacity spectrum and demand spectrum using effective viscous damping. The response modification factor of CFS piers is presented to apply in seismic design on a basis of this evaluation for a seismic performance.

Seismic Performance Analysis of RC Piers with Lap-spliced Reinforced Steel and Differentiated Aspect Ratios (주철근 겹침이음 및 형상비에 따른 철근콘크리트 교각의 내진거동 분석)

  • Cho, Chang-Beck;Shin, Ho-Jin;Kwahk, Im-Jong;Chung, Young-Soo
    • Journal of the Earthquake Engineering Society of Korea
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    • v.16 no.5
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    • pp.41-53
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    • 2012
  • The objective of this study is to evaluate the seismic capacity of RC piers with small aspect ratios. Test specimens were selected from the prototype piers among existing national roadway bridges which are expected to fail in shear and/or complex shear-flexural mode. Two groups of full scale RC pier models were constructed with aspect ratios of 2.25 and 2.67. Quasi-static tests have been implemented to investigate the failure behavior of the RC piers in terms of the lap-spliced longitudinal reinforcing steel and the aspect ratio. It is confirmed that regarding its shear-flexural behavior, the pier is very sensitive to the aspect ratio or details. In the case of a test pier with highly lap-spliced longitudinal bars, the bond failure of lap-splice steels was the dominant cause of failure before the occurrence of flexure or shear-flexural failure, despite a slight change in the aspect ratio. Finally, based on the test results and analysis, this paper proposes formulas for the yielding and ultimate displacements of circular reinforced concrete bridge piers without seismic details. These formulas will be useful for the investigation and upgrade of the seismic capacity of bridge piers without seismic details.

Investigation of Molten Fuel Relocation Dynamics with Applications to LMFBR Post-Accident Fuel Relocation

  • Chun, Moon-Hyun
    • Nuclear Engineering and Technology
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    • v.12 no.2
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    • pp.88-98
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    • 1980
  • The process of solidification of a single-phase flowing hot fluid in a cylindrical tube has been investigated analytically and experimentally. A series of tests were performed, using paraffin -wax and Wood's metal as flowing hot fluids. These data verified the existing quasistatic numerical analysis model of freezing process developed at Brookhaven National Laboratory In addition, experimental results provided information regarding the effects of various parameters on the .process of transient flowing and freezing through a vertical channel. The experimental apparatus and techniques are described. Comparison of experimental data with predictions of mathematical models for transient molten fluid displacement are presented in graphical form. In addition, the mathematical model is applied to LMFBR post-accident conditions.

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Performance Evaluation of Scale-down Concrete Filled FRP Columns (축소모형실험을 통한 콘크리트 충전 FRP 합성교각의 성능 평가)

  • Youm, Kwang-Soo;Lee, Seung-Hwe;Lee, Young-Ho;Song, Jae-Joon;Hwang, Yoon-Koog
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.1
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    • pp.135-144
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    • 2009
  • The present paper represents experimental studies on the performance of concrete filled FRP columns. Eight scale-down specimens were conducted by quasi-static cyclic loading test. FRP thickness, concrete strength, horizontal rebar ratio, and diameter were selected as test parameters. The capacities of ductility for cyclic loading was evaluated and the damping ratio and failure mode from the stiffness reduction of each test specimen were compared.

Seismic Performance Analysis of RC Bridge Piers with 3.5 Aspect Ratio depending on Testing Methods (형상비 3.5 RC교각의 실험 방법에 의한 내진성능 분석)

  • Hong, Hyun-Ki;Park, Chang-Young;Chung, Young-Soo
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.93-96
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    • 2008
  • This paper deals with the shaking table test(STT), the Quasi-Static Test(QST), and the Pseudo-Dynamic Test(PDT) to evaluate the seismic performance of RC bridge piers under near fault ground motion. Five scaled specimens were constructed the weight of the superstructure was applied through the prestressing strand at the centroid of the column section during the QST and PDT. However, the STT was simulated. The lateral inertia force of the superstructure by the mass frame which was linked with the pier because of the limited payload of shaking table. Particularly for the STT, friction underneath the mass frame was minimized by special details and it was verified by a series of pre-load test. Scale factor of the RC piers was 4.25.

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