• Title/Summary/Keyword: numerical stability

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Behavior of a Geosynthetic Reinforced Two-tier Segmental Retaining Wall on a Yielding Foundation (압축성이 큰 지반 위에 시공되는 계단형 블록식 보강토 옹벽의 거동)

  • Yoo Chung-Sik;Jeon Han-Yong
    • Journal of the Korean Geotechnical Society
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    • v.21 no.7
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    • pp.21-29
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    • 2005
  • This paper presents the results of a numerical investigation on the behavior of a geosynthetic reinforced two-tier segmental retaining wall (GR-SRW) on a yielding foundation. A hypothetical 10 m high two tier GR-SRW to be constructed on an incompetent foundation containing a layer of relative soft soil deposit was considered. A verified finite-element procedure was employed to get insights into the effect of foundation yielding on the wall behavior including the wall deformation and the reinforcement load. It is shown that the effect of foundation yielding is to increase the wall deformation as well as the reinforcement load, thus influencing both the internal as well as the external stability of the wall. Practical implications of the findings obtained from this study are highlighted in this paper.

Design of Pile Foundations Considering Negative Skin Friction (부마찰력을 고려한 말뚝기초 설계)

  • Kim Ju-Hyong;Kwon Oh-Sung;Kim Myoug-Mo
    • Journal of the Korean Geotechnical Society
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    • v.21 no.5
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    • pp.65-74
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    • 2005
  • The negative skin friction on piles, which are installed in currently consolidating soft deposits, creates significant problems on the stability of pile foundations. This study investigated whether or not the pile foundation designs were appropriate in soft deposits with large amount of consolidation settlement. The final settlements of the grounds along the pile depth were estimated by the soil parameters obtained from the laboratory tests and by the field-measured settlement curves, if they were available. The displacement of the piles along the pile depth was estimated by both the load transfer method and the numerical method. Both methods gave similar locations of neutral planes and magnitudes of the maximum axial forces on the piles. The movements of the ground and the piles were compared to calculate the down drag acting on piles. For the piles whose bearing capacities were less than the design loads including the down drag, slip layer coatings and/or incrementing of the pile penetration depth into the bearing stratum were proposed to improve the pile capacities.

The design of coffer dam utilized P.R.D. method (P.R.D. 공법을 활용한 가물막이 설계)

  • Park, Chal-Sook;Lee, Kyu-Tak;Yum, Kyung-Taek;Kim, Yoon-Ku;Kang, Bong-Gwon;Lee, Jae-Weon;Lim, Seok-San;Jeong, Ji-Yearl
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.869-887
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    • 2008
  • Coffer dam for tunnel type spillway in inflow section of Dae-am dam was originally planned as 2 lines sheet piles with Water Zet method. But, the result of pilot test was caused of some problems that vibration during installation of pile could pollute water and water leakage could the lower part. So, sheet piles was not satisfactory for faculty of coffer dam. Structural instability of sheet pile system need to reinforcement. Characteristic of Dae-am dam was small reservoir capacity but wide drainage area, of which it was judgment that security of leakage and stability was difficult during excavation of inlet part. So, we consider that water curtain method utilized with in site pouring concrete pile method was designed at weir part of spillway. We were known about basement rock that geological boring was carried out in weir part. After taking a deep consideration, PRD method was accepted as a new method. Concrete pile by PRD was installed to below country rock. CJM method was carried out with PRD. After making concrete wall using Top-down method, earth anchors were installed for supporting it. According to the result of numerical analysis, as water level rises, wall is stable.

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Estimation of Dynamic Characteristics of Core Zone of Rockfill Dam by Multi-channel Analysis of Surface Waves (MASW 조사를 통한 사력댐 코어존 동적물성의 평가)

  • Lee, Jong-Wook;Ha, Ik-Soo;Oh, Byung-Hyun
    • Proceedings of the Korean Geotechical Society Conference
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    • 2008.10a
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    • pp.860-868
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    • 2008
  • Seismic safety analysis of rockfill dams are consist of the stability analysis as an simplifed method and the dynamic analysis as an detailed method. When high risk dams such as Multi-purpose dams were often applied detailed method by dynamic analysis, dynamic properties of dam materials such as shear modulus are considered as most important factor. Dynamic material properties such as shear modulus had to be investigated by cyclic triaxial test et al. during design and construction stage but these were not conducted because of the condition of domestic seismic design technique. MASW and SASW methods had been applied as a non destructive method to investigate dynamic material properties of existing rockfill dam, has no problems in dam safety at present. These methods were usually performed under the assumptions that the subsurface can be described horizontally homogeneous and isotropic layers. Recent studies(Marwin, 1993, Kim, 2001) showed that surface waves generated through inclined structures have different characteristics from those through a horizontally homogeneous layered model. further Kim et al(2005) and Min and Kim(2006) showed that central core type rockfill dam overestimated the shear wave velocities as increasing the depth through the 3D numerical modelling dut to the effect of outer rockfill and geometrical reasons In this study the results of shear wave velocities of seven rockfill dams form comprehensive facility review, was carried out from 2003 to 2007, were collected and analysed to establish the shear wave velocity distribution characteristics in increasing confining stress in rockfill dams and surface wave velocity ranges in rockfill dam through MASW and the limitation in application are discussed to be utilized as an reference value for dynamic analysis.

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Distributed Server based Data Management and Device Control Scheme for Efficient IoT Service in Smart Building (스마트 빌딩에서의 효율적인 사물인터넷 서비스를 위한 분산 서버 기반 데이터 관리 및 제어 기법)

  • Choi, Sang-Il
    • Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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    • 2017.05a
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    • pp.547-550
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    • 2017
  • With the deployment of Internet of Things (IoT) services, the interest of smart building management system is rapidly increased. However, existing smart building management system has some limitations such as single point of failure, scalability, processing delay by using the centralized service platform server. To overcome these limitations, in this paper, the distributed server based smart building management scheme is proposed. In the proposed scheme, it is possible to provide fast and efficient IoT services, regardless of the scale of smart building, by using the distributed server of each floor. From the numerical analysis, it is shown that the proposed scheme provides better performance than the existing centralized scheme in terms of stability of database and service processing delay.

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Saccharification Characteristics and Kinetic Analysis of Modified Cellulase with a Copolymer (공중합 고분자를 이용한 수식셀룰라아제의 당화 특성 및 반응속도에 관한 연구)

  • 전영호;신호철박진원
    • KSBB Journal
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    • v.11 no.6
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    • pp.712-717
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    • 1996
  • Cellulase was modified with synthetic copolymers of polyoxyethylene derivative and maleic acid anhydride. The saccharification characteristics and enzymatic reaction kinetic mechanism of modified and native cellulases were observed. In modification reaction of cellulase, degree of modification(DM) increased, as mass ratio of copolymers to enzyme increased. Maximum DM was 55% at mass ratio of 4 and remained activity was 75%. In saccharification experiment modified enzyme had maintained higher stability than native enzyme over all the reaction and the final conversion yield of modified enzyme was greater than that of native enzyme. Numerical simulation based on the reaction mechanism considering enzymatic deactivation was performed. Modified enzyme had kept higher free enzyme concentration over all the reaction than that of native enzyme. Comparing calculation values with experimental data, calculation values were in accordance with experimental data.

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A Study on the Failure Mode of FRP Bridge Deck in It's Weak Axis (FRP 바닥판의 약축방향 파괴모드에 관한 연구)

  • Kim Byeong-Min;Hwang Yoon-Koog;Lee Young-Ho;Kang Young-Jong;Zi Goang-Seup
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.19 no.1 s.71
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    • pp.73-83
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    • 2006
  • The failure mechanism of a hollow bridge deck which is made of fiber reinforced polymer (FRP) to improve its durability and life time significantly is investigated using both experiments and analyses. While the Load-displacement behavior of the deck in the longitudinal direction is almost linear just before the failure, the behavior in the transverse direction shows a strong nonlinearity even in its initial response with relatively small magnitude of loads. We found that the nonlinearity is due to the imperfection of the connection between the flange and the web; a plastic deformation can t라e place in the connection. The argument is demonstrated using a simple structural model in which a rigid plastic hinge is introduced to the connection. We also checked the contribution of the delamination mechanism to the failure. But the delamination is not the main mechanism which initiates and causes the failure of the bridge deck. In order to improved the structural behavior of the deck in the transverse direction, we suggested that the empty space of the bridge deck is filled with a foam and confirmed the improved behavior by a numerical analysis.

A Bifurcation Analysis of Space Structures by Using 3D Beam-Column Element Considering Finite Deformations and Bowing Effect (유한변형과 굽힘효과가 고려된 3차원 보-기둥요소에 의한 공간구조물의 분기좌굴해석)

  • Lee, Kyung-Soo;Han, Sang-Eul
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.22 no.4
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    • pp.307-314
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    • 2009
  • The present paper briefly describes the space frame element and the fundamental strategies in computational elastic bifurcation theory of geometrically nonlinear, single load parameter conservative elastic spatial structures. A method for large deformation(rotation) analysis of space frame is based on an eulerian formulation, which takes into consideration the effects of large joint translations and rotations with finite deformation(rotation). The local member force-deformation relationships are based on the beam-column approach, and the change in member chord lengths caused by axial strain and flexural bowing are taken into account. and the derived geometric stiffness matrix is unsymmetric because of the fact that finite rotations are not commutative under addition. To detect the singular point such as bifurcation point, an iterative pin-pointing algorithm is proposed. And the path switching mode for bifurcation path is based on the non-negative eigen-value and it's corresponding eigen-vector. Some numerical examples for bifurcation analysis are carried out for a plane frame, plane circular arch and space dome structures are described.

Design of umbrella arch method based on adaptive SVM and reliability concept (Adaptive SVM 기법 및 신뢰성 개념을 적용한 강관다단공법의 설계기법 연구)

  • Lee, Jun S.;Sagong, Myung;Park, Jeongjun;Choi, Il Yoon
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.20 no.4
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    • pp.701-715
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    • 2018
  • A reliability based design approach of the tunnel reinforcement with umbrella arch method was considered to better represent the uncertainties of the weak rock properties around the tunnel. For this, a machine learning approach called an Adaptive Support Vector Machine (ASVM) together with the limit equilibrium method were introduced to minimize the iteration numbers during the classification training of the tunnel stability. The proposed method was compared with the results of typical Monte Carlo simulations. It was concluded that the ASVM was very efficient and accurate to calculate the probability of failure having auxiliary umbrella arches and uncertain material properties of the tunnel. Future work will be concentrated on the refinement of the fast adaptation of the SVM classification so that the minimum number of numerical analyses can be used where the limit solution is not available.

Hydrodynamic Performance of a 2,500-ton Class Trimaran

  • Kang, kuk-Jin;Lee, Chun-Ju;Kim, Sun-Young;Park, Yun-Rak;Lee, Jin-Tae
    • Journal of Ship and Ocean Technology
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    • v.6 no.2
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    • pp.23-36
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    • 2002
  • This paper describes the powering, seakeeping and maneuvering performances for a 2,500-ton class trimaran. Influence of the side-hull forms and location of those in longitudinal and transverse direction to resistance performance was systematically investigated by a series of model tests and numerical calculations. It was found that the longitudinal location of side-hulls was the most influential design parameter to the resistance performance of the trimaran and the optimum location of side-hull depends on ship speeds. When the side-hull stem is located near the primary wave hollow generated by the main hull, the trimaran shows the best resistance performance. Powering performance of the trimaran is superior to those of similar mono-hull ships. Seakeeping model tests for the trimaran were executed and the results were compared with the theoretical results of a similar mono-hull ship. Generally speaking, seakeeping performance of the trimaran is superior to that of a mono-hull ship. In particular, pitching and rolling performance of the trimaran is excellent, which is due to the increased length and breadth. Maneuvering model tests using a HPMM equipment were executed to evaluate the maneuvering performance of the trimaran. Maneuvering simulation was performed using the maneuvering coefficients from the model tests. The results show that the control ability of heading angle and the direction keeping stability of the trimaran is excellent, even though the turning performance is rather worse compared to those of a similar mono-hull ship.