• Title/Summary/Keyword: elasto-plastic stability

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Modification of the Sloan치s Substepping Scheme for the Numerical Stress Integration of Elasto-plastic Constitutive Models (탄소성 구성 모델의 수치 응력 적분을 위한 단계분할 절차에 관한 연구)

  • 김범상;정충기
    • Geotechnical Engineering
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    • v.14 no.4
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    • pp.129-140
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    • 1998
  • Elasto-plastic finite element analysis of geotechnical boundary value problems necessitate the stress integration for the known strain increments. For the elasto-plastic constitutive model, the stress integration is generally achieved by numerical schemes, because analytical integration is impossible for general strain path. In this case, the accuracy of numerical stress integration has an important role on the overall accuracy of nonlinear finite element solution. In this study, the Sloan's substepping method which is one of explicit integration methods has been adopted and iris applicability has been checked. The unstability and inaccuracy of ifs results initiated from initial stress level were revealed. So. a new modified numerical integration method which employs the basic concept of modified Euler scheme for error control is proposed and accuracy and stability of the solutions are confirmed by triaxial test simulation.

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Stability Analysis of a Subway Tunnel Excavated in Soft Rock (연약암반에 굴착되는 지하철 터널의 안정성 해석)

  • 이연규;서영호;이정인
    • Tunnel and Underground Space
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    • v.3 no.2
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    • pp.118-131
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    • 1993
  • In this study, the results of elasto-plastic analysis for a subway tunnel using finite element method are presented. To determine input data for the analysis we carried out rock mass classificaton, insitu test and back analysis using measured displacements. Tunnel convergence, extension of yielding Zone and support load are described. By comparing the results of four different reinforcement patterns, the influence of those patterns on tunnel stability is presented. As a result of the analysis we suggest a ratonal reinforcement pattern.

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Stability Analysis of Concrete Liner installed in a Compressed Air Storage Tunnel (압축공기 저장용 터널에 설치된 콘크리트 라이닝의 안정성 해석)

  • Lee, Youn-Kyou;Park, Kyung-Soon;Song, Won-Kyong;Park, Chul-Whan;Choi, Byung-Hee
    • Tunnel and Underground Space
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    • v.19 no.6
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    • pp.498-506
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    • 2009
  • The stability assessment of a concrete liner of a compressed air storage tunnel should be performed by an approach which is different from that commonly used for the liners of road tunnels, since the liner is exposed to high air pressure. In this study, the stability analysis method for the liner of compressed air storage tunnel is proposed based on the elastic and elasto-plastic solutions of the thick-walled cylinder problem. In case of elastic analysis, the yield initiation condition at the inner boundary is considered as the failure condition of the liner, while the condition which results in the extension of yielding zone to a certain depth is taken as a failure indicator of the liner in the elasto-plastic analysis taking Mohr-Coulomb criterion. The application of the proposed method revealed that the influence of the relative magnitude of boundary loads on the stability of liner is considerable. In particular, noting that the estimation of the outer boundary load may be relatively difficult, it is thought that the precise prediction of outer boundary load is very important in the analysis. Accordingly, the emphasis is put on the selection of the liner installation time, which may govern the magnitude of outer boundary load.

Ultimate behavior and ultimate load capacity of steel cable-stayed bridges

  • Choi, D.H.;Yoo, H.;Shin, J.I.;Park, S.I.;Nogami, K.
    • Structural Engineering and Mechanics
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    • v.27 no.4
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    • pp.477-499
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    • 2007
  • The main purpose of this paper is to investigate the ultimate behavior of steel cable-stayed bridges with design variables and compare the validity and applicability of computational methods for evaluating ultimate load capacity of cable-stayed bridges. The methods considered in this paper are elastic buckling analysis, inelastic buckling analysis and nonlinear elasto-plastic analysis. Elastic buckling analysis uses a numerical eigenvalue calculation without considering geometric nonlinearities of cable-stayed bridges and the inelastic material behavior of main components. Inelastic buckling analysis uses an iterative eigenvalue calculation to consider inelastic material behavior, but cannot consider geometric nonlinearities of cable-stayed bridges. The tangent modulus concept with the column strength curve prescribed in AASHTO LRFD is used to consider inelastic buckling behavior. Detailed procedures of inelastic buckling analysis are presented and corresponding computer codes were developed. In contrast, nonlinear elasto-plastic analysis uses an incremental-iterative method and can consider both geometric nonlinearities and inelastic material behavior of a cable-stayed bridge. Proprietary software ABAQUS are used and user-subroutines are newly written to update equivalent modulus of cables to consider geometric nonlinearity due to cable sags at each increment step. Ultimate load capacities with the three analyses are evaluated for numerical models of cable-stayed bridges that have center spans of 600 m, 900 m and 1200 m with different girder depths and live load cases. The results show that inelastic buckling analysis is an effective approximation method, as a simple and fast alternative, to obtain ultimate load capacity of long span cable-stayed bridges, whereas elastic buckling analysis greatly overestimates the overall stability of cable-stayed bridges.

A Study on the Behavior of the Retaining Walls with the Improved Top-Down Support System using the Building Structure (건축 구조체를 이용한 개량 역타공법 적용시 흙막이 벽체의 거동 연구)

  • Chun, Byung-Sik;Roh, Bae-Young;Do, Jong-Nam;Rew, Woo-Hyun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.1666-1672
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    • 2008
  • In this study, it collected and analyzed a construction case of the improved top-down support system application field on a case by case retaining wall method. The behavior of horizontal displacement was analyzed according to retaining wall type after reviewing a design stage and estimated horizontal displacement under the construction. The study results showed that it is judged stable until excavation termination irrelevant to a retaining wall method at the improved top-down support system application. It is judged that the settlement of behind ground can minimize because the retaining wall head displacement also behave stably. It was compared the predicted horizontal displacement in design and the measured horizontal displacement acquired through a measurement by using Elasto-Plastic analysis program. The comparison results showed that a similar horizontal displacement was predicted within stability standard irrelevant to a retaining wall method. So, it is decided that the advanced prediction is reasonable by Elasto-Plastic analysis in design applied the improved top-down support system. In the case of the ground anchor method application under a same condition, it is decided that a horizontal displacement will more increase than the improved top-down support system is applied. If a section condition is same, it was decided that to apply top-down support system is more stable than that.

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Reducing Effect Analysis on Earthquake Response of 100m Spanned Single-Layered Lattice Domes With LRB Seismic Isolation System (LRB 면진 장치를 갖는 100m 단층 래티스 돔의 지진 응답에 대한 감소 효과 분석)

  • Park, Kang-Geun;Lee, Dong-Woo
    • Journal of Korean Association for Spatial Structures
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    • v.19 no.1
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    • pp.53-64
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    • 2019
  • The objective of this study is to investigate the earthquake response for the design of 100m spanned single-layer lattice dome. The plastic hinge analysis and eigenvalue buckling analysis are performed to estimate the ultimate load of single-layered lattice domes under vertical loads. In order to ensure the stability of lattice domes, it is investigated for the plastic hinge progressive status by the pushover increment analysis considering the elasto-plastic connection. One of the most effective methods to reduce the earthquake response of large span domes is to install the LRB isolation system of a dome. The authors discuss the reducing effect for the earthquake dynamic response of 100m spanned single-layered lattice domes. The LRB seismic isolation system can greatly reduce the dynamic response of lattice domes for the horizontal and vertical earthquake ground motion.

A NEW FEEDBACK TECHNIQUE FOR TUNNEL SAFETY BY USING MEASURED DISPLACEMENTS DURING TUNNEL EXCAVATION

  • Sihyun PARK;Yongsuk SHIN;Sungkun PARK
    • International conference on construction engineering and project management
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    • 2009.05a
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    • pp.432-439
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    • 2009
  • This research project was carried out to develop the technique to assess quantitatively and rapidly the stability of a tunnel by using the measured displacement at the tunnel construction site under excavation. To achieve this purpose, a critical strain concept was introduced and applied to an assessment of a tunnel under construction. The new technique calculates numerically the strains of the surrounding ground by using the measured displacements during excavation. A numerical practical system was developed based on the proposed analysis technique in this study. The feasibility of the developed analysis module was verified by incorporating the analysis results obtained by commercial programs into the developed analysis module. To verify the feasibility of the developed analysis module, analysis results of models both elastic and elasto-plastic grounds were investigated for the circular tunnel design. Then the measured displacements obtained in the field are utilized practically to assess the safety of tunnels using critical strain concept. It was verified that stress conditions of in-situ ground and ground material properties were accurately assessed by inputting the calculated displacement obtained by commercial program into this module for the elastic ground. However for the elasto-plastic ground, analysis module can reproduce the initial conditions more closely for the soft rock ground than for the weathered soil ground. The stability of tunnels evaluated with two types of strains, that is, the strains obtained by dividing the crown displacement into a tunnel size and the strains obtained by using the analysis module. From this study, it is confirmed that the critical strain concept can be fully adopted within the engineering judgment in practical tunnel problems and the developed module can be used as a reasonable tool for the assessment of the tunnel stability in the field.

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Comparative Study on the Stability Analysis Methods for Underground Pumped Powerhouse Caverns in Korea (국내 양수발전소 지하공동 안정성 해석방법의 비교)

  • 임한욱;김치환
    • Tunnel and Underground Space
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    • v.12 no.4
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    • pp.248-258
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    • 2002
  • The sixth underground pumped powerhouse cavern is now under construction in Korea. For the stability analysis for the caverns of the five underground powerhouses, finite element method was used. For the analysis, in-situ rock stress were measured by overcoring method. The stress measurement showed that initial horizontal to vertical stress ratio was 1.07-1.32 in low powerhouse sites. Rock mass strength and elasticity were assumed from rock core properties through engineering processes. So the ratio of input elasticity fur the analysis were about 0.16-0.55 to rock core elasticity. In most of the analysis, elasto-plastic condition with Mohr-Coulomb failure criteria were applied. But in one case, viscoelastic condition was applied, too. The input cohesion and internal friction angle were approximately 0.12-0.22, 0.6-0.87 to rock core strength parameters, respectively.

Case study on stability performance of asymmetric steel arch bridge with inclined arch ribs

  • Hu, Xinke;Xie, Xu;Tang, Zhanzhan;Shen, Yonggang;Wu, Pu;Song, Lianfeng
    • Steel and Composite Structures
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    • v.18 no.1
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    • pp.273-288
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    • 2015
  • As one of the most common failure types of arch bridges, stability is one of the critical aspects for the design of arch bridges. Using 3D finite element model in ABAQUS, this paper has studied the stability performance of an arch bridge with inclined arch ribs and hangers, and the analysis also took the effects of geometrical and material nonlinearity into account. The impact of local buckling and residual stress of steel plates on global stability and the applicability of fiber model in stability analysis for steel arch bridges were also investigated. The results demonstrate an excellent stability of the arch bridge because of the transverse constraint provided by transversely-inclined hangers. The distortion of cross section, local buckling and residual stress of ribs has an insignificant effect on the stability of the structure, and the accurate ultimate strength may be obtained from a fiber model analysis. This study also shows that the yielding of the arch ribs has a significant impact on the ultimate capacity of the structure, and the bearing capacity may also be approximately estimated by the initial yield strength of the arch rib.

Effect of the Residual Excess Pore Water Pressure on the Slope Stability Subjected to Earthquake Motion (잔류 과잉공극수압이 지진 하중을 받는 사면의 안정에 미치는 영향)

  • Lee, Jun-Dae;Kwon, Young-Cheul;Bae, Woo-Seok
    • Journal of the Korean Society of Safety
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    • v.21 no.2 s.74
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    • pp.107-113
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    • 2006
  • Earthquake motion is one of the most significant influence factors on the slope stability. In this paper, an effective stress analysis with the elasto-plastic model was carried out to investigate the behavior of the slope stability subjected to the successive two strong earthquake motions, fore and main shock. The major influence of fore shock to the slope stability was considered as the existence of the residual excess pore water pressure. The paper presents the influence of the existence of the fore shock to slope stability using the numerical analyses. In conclusion, the excess pore pressure by the fore shock was not dissipated during the 7hrs of consolidation. By this residual excess pore water pressure, the factor of safety at the sliding face showed the minimum values, and the deformations of slope was large when compared with the case that considered the main shock only. Furthermore, the minimum of the factor of safety came out after the end of the earthquake motion.