• Title/Summary/Keyword: 소성변형모형

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Lateral Earth Pressures on Buried Pipes due to Lateral Flow of Soft Grounds (연약지반의 측방유동으로 인하여 매설관에 작용하는 측방토압)

  • Hong, Byungsik;Kim, Jaehong
    • Journal of the Korean GEO-environmental Society
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    • v.11 no.9
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    • pp.27-38
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    • 2010
  • A series of model test as well as numerical analysis by FEM was performed to investigate lateral earth pressure acting on a buried pipe in soft ground undergoing horizontal soil movement. A model test apparatus was manufactured so as to simulate horizontal soil movement in model soft ground, in which a model rigid buried pipe was installed. The velocity of soil deformation could be controlled as wanted during testing. The model test was performed on buried pipes with various diameters and shapes to investigate major factors affected the lateral earth pressure. The result of model tests showed that the larger lateral earth pressure acted on the buried pipes under the faster velocity of soil movement. The result of numerical analysis, which was performed under immediate loading condition, showed a similar behavior with the result of model tests under 0.3mm/min to 1.0mm/min velocity of soil deformation. Most of model tests showed the soil deformation-lateral load behavior, in which the first yielding load developed at small soil deformation and elastic behavior was observed by the yielding load. Then, lateral load was kept constant by the second yielding load, in which plastic behavior was observed between the first yielding load and the second yielding one. Beyond the second yielding load, the compression behavior zone was observed. When the velocity was too fast, however, the lateral load was increased with soil deformation beyond the first yielding load without showing the second yielding load. The buried pipes with the larger diameter was subjected to the larger lateral load and the larger increasing rate of lateral load. At small soil deformation, the influence of diameter and shape of buried pipes on lateral load was small. However, when soil deformation was increased considerably, the influence became more and more.

A Study on the Lateral Flow in Soft Soils subjected to Unsymmetrical Surcharges (편재하중을 받는 연약지반의 측방유동에 관한 연구)

  • 안종필
    • The Journal of Engineering Geology
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    • v.3 no.2
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    • pp.177-190
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    • 1993
  • When soft soils are effected by unsymmetrical surcharge due to embankement and abutements of a bridge, large plastic sheraring deformations such as settlements, lateral displacements, upheavals and sliding shearing failure in the soils occurred and they have often damaged considerabily to the soils and structure. This study examines the existing theoretical background for the behavior of the displacement of soils by unsymmetrical surcharge on the soft soils and compares the analytical results to the actual measurements performed through the model test. The procedures of model test are that a model stock device is made and soft soils are filled in a container which fixes the soils. Then the displacements observed when surcharge load increa ses by regular interval at undrainage condition. It analyzes the relation of soil characteristics to displacement, critical surcharge and ultimate bearing capadty, condition of plastic flow and lateral flow pressure, comparing them with the existing theories. Understanding the causes of lateral displacement in soft soils due to unsymmetrical surchages will prevent a damage in advance.

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Universal Distinct Element Code (개별요소 프로그램 UDEC의 소개)

  • 이선구;변광욱
    • Computational Structural Engineering
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    • v.4 no.1
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    • pp.42-43
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    • 1991
  • 균열성암반의 모형화 기술은 계속적으로 보완발전되어 UDEC이 개발되었으며, 현재 UDEC의 최신판은 블록 내부를 다시 유한차분요소로 분할하여 블록의 소성거동(Mohr-Coulomb Model) 및 쪼개짐을 고려할 수 있고, 절리면에서의 유체흐름 및 유압의 발생, 그리고 열응력 해석 등 평면변형 문제의 정적해석과 지진 및 폭발하중을 고려한 동적해석이 가능하다. UDEC은 전처리 기능이 뛰어나 최소한의 입력데이타로써 전체 모형의 데이타를 자동생성시키며 절리면의 통계학적 자동생성 및 터널형상의 자동생성도 가능하다. UDEC은 실용적인 보강요소를 구비하여 Rock Bolt 뿐만 아니라 그라우트를 고려한 Cable Bolt를 모형화할 수 있으며 국부적인(Key Block)보강으로써 불연속체 전체의 안정을 검토할 수 있다.

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Constitutive Relation of Concrete to Predict P-M Interaction Strength of Rectangular CFT Short Columns (콘크리트충전 각형강관단주의 P-M 조합강도 예측을 위한 콘크리트 구성방정식)

  • Lee, Cheol Ho;Kang, Ki Yong;Kim, Sung Yong
    • Journal of Korean Society of Steel Construction
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    • v.27 no.1
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    • pp.31-42
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    • 2015
  • The plastic stress distribution method and the strain compatibility method are the two representative methods to calculate the P-M interaction strength of RCFT (rectangular concrete filled tube) columns. The plastic stress distribution method is approximate while the stress compatibility method should approach the exact solution if accurate constitutive relations of the materials involved are used. Recent study by the authors pointed out that, because of lack of accurate constitutive model for the concrete confined by the rectangular steel tube, no strain compatibility method according to the current structural provisions provides a satisfactory prediction of the P-M interaction strength of RCFT columns under various material combinations. An empirical constitutive model which can capture the stress-strain characteristics of the confined concrete of RCFT columns is proposed based on analyzing extensive exisitng test database. The key idea was to define the concrete crushing strain as a function of steel-to-concrete strength ratio and width-to-thickness ratio of steel tube. It was shown that the proposed model leads to more accurate and more consistent prediction of the P-M interaction strength of RCFT columns under general design conditions.

Evaluation of Ground Deformation during Excavation of Vertical Shaft through Centrifuge Model Test (원심모형실험을 통한 원형 수직구 굴착 중 발생하는 지반 변형 평가)

  • Kim, Joonyoung
    • Journal of the Korean Geotechnical Society
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    • v.38 no.1
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    • pp.35-45
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    • 2022
  • When constructing a cylindrical vertical shaft through the open-cut method, the walls are generally designed to be temporary flexible walls that allow a certain level of displacement. The earth pressure applied to the flexible walls acts as an external force and its accurate estimation is essential for reasonable and economical structure design. The earth pressure applied to the flexible wall is closely interrelated to the plastic deformation of the surrounding ground. This study simulated a stepwise excavation for constructing a cylindrical vertical shaft through a centrifugal model test and evaluated the continuous deformation behaviors of the surrounding ground through digital image analysis.

The Mechanical Behavior of Steel Circular Caisson by Horizontal Load (水平載荷에 따른 鋼製圓筒 케이슨의 力學的 擧動)

  • 장정욱
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.10 no.3
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    • pp.141-150
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    • 1998
  • Model tests were performed to examine the mechanical behavior of steel circular caisson by horizontal load. It was generally found that displacements and bottom pressure of the caisson model were increased rapidly at the local plastic load. The maximum displacement was measured at the loading point, whereas the less displacement was measured at the upper part of the caisson model. The bottom pressure was getting higher, as it was nearer the loading side. Furthermore, the increase ratio of the bottom pressure was higher as the load was increased.

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Analysis of the Strain Rate Effect in Electro-Magnetic Forming (전자기 성형에서의 변형률 속도 효과 해석)

  • 곽신웅;신효철;이종수
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.14 no.5
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    • pp.1043-1058
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    • 1990
  • The Strain rate effect in electro-magnetic forming, which is one of the high velocity forming methods, is studied by the finite element method in this paper. The forming process is simplified by neglecting the coupling between magnetic field and work-piece deformation, and the impulsive magnetic pressure is regarded as inner pressure load. A rate-dependent elasto-plastic material model, of which tangential modulus depends of effective strain rate, is proposed. The model is shown to well describe the transient increase of yield stresses, the decreases of the final displacement and yield stress, the decrease of the difference in the distribution of deformation along the axial direction, and the change of deformation mechanism due to strain rate effect. As a result, displacement, final deformed shape, radial velocity, deformation energy, and the changes of effective stress, effective strain and effective strain rate through plastic working are given. Based on the results, the effectiveness of this model and the strain rate effect of the deformation process of the work-piece are discussed.

Analyses on the Impact of Plastic Deformation on Change of the Road Surface Condition (소성변형 정도를 고려한 시간전개에 따른 노면상태 변화 분석)

  • SON, Young Tae;PARK, Sang-Hyun
    • Journal of Korean Society of Transportation
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    • v.36 no.3
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    • pp.216-228
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    • 2018
  • In this study analyzed the ponding changing of plastic deformation section follwed time development to apply weather, geometry and traffic data in additon to time development to improve road management service and safety of roads during or after rain. After We selected an 8.3km section of old national highway the Seongnam-Janghowon section and created a three-demensional surface of terrain through the numerical transformantion of design drawing data, with reflection the linear data of the same coordinate system in order to describe more realistic roads, we design additional structures with shading above roads. The altitude and azimuth of the sun were calculated and set based on the longitude and latitude data of the survey line for the analysis of the sun rate, and the daylight impact zone was visualized by setting the shaded time to an interval of 1 hour and the shade rate of the corresponding section. In addition, the evaporation volume calculated from weather data such as temperature, humidity, radiant energy, and road temperature analyzes together, it will use the way of a safer and more efficient road management as grasping the ponding changing more efficent in time development.

Constitutive Model for Plastic Damage of Ductile Materials (연성재료의 소성손상 구성방정식에 관한 연구)

  • I.S. Nho;S.J. Yim;J.G. Shin
    • Journal of the Society of Naval Architects of Korea
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    • v.29 no.4
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    • pp.179-192
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    • 1992
  • An elasto-plastic-damage constitutive model for ductile materials was derived under the framework of thermodynamic approach of contimuum damage mechanics(CDM) in which internal irreversible thermodynamic change of micro-structure of materials such as plastic deformation and damage evolution were considered as thermodynamic state variables. New constitutive model can predict not only the elasto-plastic behaviors but also the sequential degradation process of ductile materials more rationally.

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Finite Element Analysis for Plastic Large Deformation and Anisotropic Damage (소성 대변형 및 이방성 손상의 유한요소해석)

  • I.S. Nho;S.J. Yim
    • Journal of the Society of Naval Architects of Korea
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    • v.30 no.1
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    • pp.145-156
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    • 1993
  • An improved analysis model for material nonlinearity induced by elasto-plastic deformation and damage including large strain response was proposed. The elasto-plastic-damage constitutive model based on the continuum damage mechanics approach was adopted to overcome limitations of the conventional plastic theory, which can manage the anisotropic tonsorial damages evolved during time-independent plastic deformation process of materials. Updated Lagrangian finite element formulation for elasto-plastic damage coupling problem including large deformation, large rotation and large strain problems was completed to develop a numerical model which can predict all kinds of structural nonlinearities and damage rationally. Finally, a finite element analysis code for the 2-dimensional plane problem was developed and the applicability and validity of the numerical model was investigated through some numerial examples. Calculations showed reasonable results in both geometrical nonlinear problem due to large deformation and material nonlinearity including the damage effect.

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