• Title/Summary/Keyword: elasto-plastic stability

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Investigation of the rapid embankment stability on the soft ground using nonlinear analysis (급속한 성토시 비선형 해석을 통한 연약지반의 안전성 검토)

  • Do, Ki-Hoon;Kim, Moo-Il;Lee, Jun-Seok
    • Proceedings of the KSR Conference
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    • 2006.11b
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    • pp.1348-1353
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    • 2006
  • In this paper, nonlinear elasto-plastic analysis was performed to investigate the stability of the rapid embankment under undrained condition. The commercial code ABAQUS/Standard was used in the study. Resonant Column test (RC test) results and Ramberg-Osgood model were utilized to simulate the nonlinear behavior of soft clay. Ramgerg-Osgood model was tested whether it simulates the nonlinear behavior of the soil properly in first. Then the analysis result was compared with the previous research results. It was found that the Ramberg-Osgood model matched well with the soil behavior of soft clay in the rapid embankment under undrained condition.

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Searching for critical failure surface in slope stability analysis by using hybrid genetic algorithm

  • Li, Shouju;Shangguan, Zichang;Duan, Hongxia;Liu, Yingxi;Luan, Maotian
    • Geomechanics and Engineering
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    • v.1 no.1
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    • pp.85-96
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    • 2009
  • The radius and coordinate of sliding circle are taken as searching variables in slope stability analysis. Genetic algorithm is applied for searching for critical factor of safety. In order to search for critical factor of safety in slope stability analysis efficiently and in a robust manner, some improvements for simple genetic algorithm are proposed. Taking the advantages of efficiency of neighbor-search of the simulated annealing and the robustness of genetic algorithm, a hybrid optimization method is presented. The numerical computation shows that the procedure can determine the minimal factor of safety and be applied to slopes with any geometry, layering, pore pressure and external load distribution. The comparisons demonstrate that the genetic algorithm provides a same solution when compared with elasto-plastic finite element program.

Deformation Analysis of Excavated Behind Ground by The Artificial Displacement Method (II) - Numerical Analysis and Application - (강제변위법을 이용한 굴착배면지반의 변형해석(II) - 수치해석 및 적용성 -)

  • Yun, Jung-Mann
    • Journal of the Korean Geosynthetics Society
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    • v.7 no.3
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    • pp.31-40
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    • 2008
  • The deformation behavior of the excavated behind ground due to the displacement shape of retention walls is predicted by numerical analysis, which can be performed using the artificial displacement method with elasto-plastic constitutive model. The displacement shape of the behind ground around the retention wall is similar to the displacement shape of the retention wall. However, far from the retention wall, it changes to the displacement shape of cantilever. The deformation (the settlement, the lateral movement) of the excavated behind ground can be decreased by restraining the upper displacement of the retention wall. The displacement shape of the retention wall due to excavation affects on the plastic failure zone and decreasing zone of stability of the excavated behind ground.

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A nonlinear Co-rotational Quasi-Conforming 4-node Shell Element Using Ivanov-Ilyushin Yield Criteria (이바노브-율리신 항복조건을 이용한 4절점 비선형 준적합 쉘요소)

  • Panot, Songsak Pramin;Kim, Ki Du
    • Journal of Korean Society of Steel Construction
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    • v.20 no.3
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    • pp.409-419
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    • 2008
  • A co-rotational quasi-conforming formulation of four- node stress resultant shell elements using Ivanov-Ilyushin yield criteria are presented for the nonlinear analysis of plate and shell structure. The formulation of the geometrical stiffness is defined by the full definition of the Green strain tensor and it is efficient for analyzing stability problems of moderately thick plates and shells as it incorporates the bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. This formulation also integrates the elasto-plastic material behaviour using Ivanov Ilyushin yield condition with isotropic strain hardening and its asocia ted flow rules. The Ivanov Ilyushin plasticity, which avoids multi-layer integration, is computationally efficient in large-scale modeling of elasto-plastic shell structures. The numerical examples herein illustrate a satisfactory concordance with test ed and published references.

Development of Constitutive Equation for Soils Under Cyclic Loading Conditions (反復荷重을 받는 흙의 構成關係式 開發)

  • Jang, Byeong-Uk;Song, Chang-Seop
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.34 no.1
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    • pp.41-48
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    • 1992
  • Various soil behaviors usually occurring in the geotechnical problems, such as, cutting and embankments, stability of slope, seepage, consolidations, shearing failures and liquefaction, should be predicted and analyzed in any way. An approach of these predictions may be followed by the development of the constitutive equations as first and subsequently solved by numerical methods. The purpose of this paper is develop the constitutive equation of sands uder monotonic or cyclic loadings. The constitutive equation which is based on elasto-plastic theory, modified anisotropic consolidated stress parameter by Sekiguchi et al and Pender's theory is derived. And the equation is included a new stress parameter, hardening function, Bauschinger's effects and Pender's theory. The model is later evaluated and confirmed the validity by the test data of Ottawa sand, Banwol sand Hongseong sand. The following conclustions may be drawn: 1. The consititutive equation which is based on elasto-plastic theory, modified anisotropic consolidated stress parpameter by Sekiguchi et al and Pender's theory is derived. The equation in included a new stress parameter, hardening function, Bauschinger's effect and Pender's theory. 2. For Ottawa sand, the result of the constitutive equation shows a better agreement than that of Oka et al. The result of axial strain agrees well with the tested data. However, the result of horizontal strain is little bit off for the cyclic loadings or large stress. It is thought that the deviation may be improved by considering Poisson's ratio and precise measurement of shear modulus. 3. Banwol sand is used for the strain and stress tests with different relative densitites and confining pressures. The predeicted result shows a good agreement with the tested data because the required material parameters were directly measurd and determined form this laboratory. 4. For Hongseong sand, the tests under same amplitude of cyclic deviatoric stress shows a similar result with the tested data in absolute strain. It shows the acute shape of turning point because the sine wave of input is used in the test but the serrated wave in prediction.

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Stability Analysis of Tunnels Excavated in Squeezing Rock Masses (압출 암반내 굴착된 터널의 안정성해석)

  • 정소걸
    • Tunnel and Underground Space
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    • v.13 no.4
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    • pp.245-259
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    • 2003
  • Refering to the articles "Squeezing rocks in tunnels(Barla, 1995)" and "Tunnelling under squeezing rock conditions(Barla 2002)" this article deals with technologies for design, stability analysis and construction of the tunnel being driven in the squeezing rock mass. The definition of this type of behavior was proposed by ISRM(1994). The identification and quantification of squeezing is given according to both the empirical and semi-empirical methods available to anticipate the potential of squeezing problems in tunnelling. Based on the experiences and lessons learned in recent years, the state of the art in modem construction methods was reported, when dealing with squeezing rock masses by either conventional or mechanical excavation methods. The closed-form solutions available for the analysis of the rock mass response during tunnel excavation are described in terms of the ground characteristic line and with reference to some elasto-plastic models for the given rock mass. Finally numerical methods were used for the simulation of different models and for design analysis of complex excavation and support systems, including three-dimensional conditions in order to quantify the influence of the advancing tunnel face to the deformation behavior of the tunnel.

Numerical study of dynamic buckling for plate and shell structures

  • Liu, Z.S.;Lee, H.P.;Lu, C.
    • Structural Engineering and Mechanics
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    • v.20 no.2
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    • pp.241-257
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    • 2005
  • A numerical approach combining the finite element method with two different stability criteria namely the Budiansky and the phase-plane buckling criteria is used to study the dynamic buckling phenomena of plate and shell structures subjected to sudden applied loading. In the finite element analysis an explicit time integration scheme is used and the two criteria are implemented in the Finite Element analysis. The dynamic responses of the plate and shell structures have been investigated for different values of the plate and shell imperfection factors. The results indicate that the dynamic buckling time, which is normally considered in predicting elasto-plastic buckling behavior, should be taken into consideration with the buckling criteria for elastic buckling analysis of plate and shell structures. By selecting proper control variables and incorporating them with two dynamic buckling criteria, the unique dynamic buckling load can be obtained and the problems of ambiguity and contradiction of dynamic buckling load of plate and shell structure can be resolved.

Theory and Analysis Method of Tunnel Convergence (터널 내공변위의 이론과 계측결과의 분석)

  • 김호영;박의섭
    • Tunnel and Underground Space
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    • v.3 no.1
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    • pp.80-95
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    • 1993
  • Convergence measurements play very important role in the assessment of stability of a tunnel and of the economics of rock reinforcements. The characteristics of convergences are both due to the face advance effect and the time-dependent behaviour of rocks. As the convergence law can be modeled as a specific function of two variables of distance and time, we can determine the type of function and the related parameters from the field measurements. By using the regression method based on the Levengberg-Marquardt algorithm, an analysis of convergence of two different tunnels and one numerical example is described. It is shown that the convergence can be modeled as following function, C(x)=a{1-exp(-bx)} or C(t)=a{1-exp(-bt)} in case of a tunnel excavated in elastic rocks, in case of elasto-plastic or over stressed rocks.

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A Study on Characteristic of Residual Stresses in a wind Tower Using the Tandem Circumferential Welding Process (Tandem 용접을 이용한 풍력타워 원주용접부 잔류응력 특성에 관한 연구)

  • Kim, Ji Sun;Kim, In Ju
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.21 no.6
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    • pp.938-945
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    • 2012
  • This research proposes FEM analysis for Tandem welding process used in wind tower and predicts optimal welding process to improve the stability of welded structures. Three dimensional elasto-plastic analyses are employed to evaluate thermo-mechanical behavior of residual stress and deformation during Tandem welding for different distance between two touches. To confirm the thermal distribution, Goldak's ellipse heat source model and the real size wind tower pipe model are utilized. Four different analyses are being performed, where in each case the distance between two electrode torches is being changed and residual stress and welding deformation are predicted. Depending on base material state, each case is divided into: Liquid (100mm), Austenite+Liquid (200mm), Austenite+Cementite (400mm), Pearlite+Cementite (800mm).

A Study on the Analysis of Construction Process for the Stressed-Arch System (Stressed-Arch 시스템의 시공 과정 해석에 관한 연구)

  • 김종범;윤종현;이경수;한상을
    • Proceedings of the Korean Institute of Building Construction Conference
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    • 2001.11a
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    • pp.118-123
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    • 2001
  • The objectives of this research are to verify the structural stability and estimate the resisting performance of Stressed-Arch system during the construction process. Full scale models are taken to obtain the objective shape by the Dynamic Relaxation Method. As a result, it measured more strain than yielding strain at the extreme fiber of top chord member on the crown, but it is shown that members have the sufficiently compressive resisting performance as well as a considerable strain recovery capacity under unloading. Therefore, it is confirmed that Stressed-Arch system apparently have sufficient range of the structural capacity, but it is required that the elasto-plastic behavior of this system must be verified more detailed by numerical analysis and experiments.

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