• Title/Summary/Keyword: Finite Element Analyses

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Comparative study between Finite Element Method and Limit Equilibrium Method on Slope Stability Analysis (사면안정해석에 있어서의 유한요소법과 한계평형법의 비교)

  • 이동엽;유충식
    • Proceedings of the Korean Geotechical Society Conference
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    • 2002.10a
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    • pp.483-490
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    • 2002
  • This paper presents the results of a comparative study between FEM and LEM on slope stability analysis. For validation, factors of safety were compared between FEM and LEM. The results from the two methods were in good agreement suggesting that the FEM with the shear strength reduction method can be effectively used on slope stability analyses. A series of analysis were then performed using the FEM for various constitutive laws, slope angles, flow rules, and the finite element discretizations. Among the findings, the finite element method in conjunction with the shear strength reduction method can provide reasonable results in terms of factor of safety. Also revealed is that the results of FEM can be significantly affected by the way in which the type of constitutive law and flow rule are selected.

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Dynamic analysis of helicoidal bars with non-circular cross-sections via mixed FEM

  • Eratli, Nihal;Yilmaz, Murat;Darilmaz, Kutlu;Omurtag, Mehmet H.
    • Structural Engineering and Mechanics
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    • v.57 no.2
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    • pp.221-238
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    • 2016
  • One of the objectives of this study is to implement the direct calculation of the torsional moment of inertia for non-circular cross-sections, which is based on the St. Venant torsion formulation and the finite element method. Recently the proposed method provides a unique calculation of the torsional rigidity of simply and multiply connected cross-sections. Next, free vibration analyses of cylindrical and non-cylindrical helices with non-circular cross-sections are solved by a curved two-nodded mixed finite element based on the Timoshenko beam theory. Some thin-thick closed or open sections are handled and the natural frequencies of cylindrical and non-cylindrical helices are compared with the literature and the commercial finite element program SAP2000.

Finite element formulations for free field one-dimensional shear wave propagation

  • Sun-Hoon Kim;Kwang-Jin Kim
    • Earthquakes and Structures
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    • v.26 no.2
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    • pp.163-174
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    • 2024
  • Dynamic equilibrium equations for finite element analysis were derived for the free field one-dimensional shear wave propagation through the horizontally layered soil deposits with the elastic half-space. We expressed Rayleigh's viscous damping consisting of mass and stiffness proportional terms. We considered two cases where damping matrices are defined in the total and relative displacement fields. Two forms of equilibrium equations are presented; one in terms of total motions and the other in terms of relative motions. To evaluate the performance of new equilibrium equations, we conducted two sets of site response analyses and directly compared them with the exact closed-form frequency domain solution. Results show that the base shear force as earthquake load represents the simpler form of equilibrium equation to be used for the finite element method. Conventional finite element procedure using base acceleration as earthquake load predicts exact solution reasonably well even in soil deposits with unrealistically high damping.

Design and ultimate behavior of RC plates and shells: two case studies

  • Min, Chang-Shik
    • Structural Engineering and Mechanics
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    • v.14 no.2
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    • pp.171-190
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    • 2002
  • Two cases of design are performed for the hyperbolic paraboloid saddle shell (Lin-Scordelis saddle shell) and the hyperbolic cooling tower (Grand Gulf cooling tower) to check the design strength against a consistent design load, therefore to verify the adequacy of the design algorithm. An iterative numerical computational algorithm is developed for combined membrane and flexural forces, which is based on equilibrium consideration for the limit state of reinforcement and cracked concrete. The design algorithm is implemented in a finite element analysis computer program developed by Mahmoud and Gupta. The amount of reinforcement is then determined at the center of each element by an elastic finite element analysis with the design ultimate load. Based on ultimate nonlinear analyses performed with designed saddle shell, the analytically calculated ultimate load exceeded the design ultimate load from 7% to 34% for analyses with various magnitude of tension stiffening. For the cooling tower problem the calculated ultimate load exceeded the design ultimate load from 26% to 63% with similar types of analyses. Since the effective tension stiffening would vary over the life of the shells due to environmental factors, a degree of uncertainty seems inevitable in calculating the actual failure load by means of numerical analysis. Even though the ultimate loads are strongly dependent on the tensile properties of concrete, the calculated ultimate loads are higher than the design ultimate loads for both design cases. For the cases designed, the design algorithm gives a lower bound on the design ultimate load with respect to the lower bound theorem. This shows the adequacy of the design algorithm developed, at least for the shells studied. The presented design algorithm for the combined membrane and flexural forces can be evolved as a general design method for reinforced concrete plates and shells through further studies involving the performance of multiple designs and the analyses of differing shell configurations.

Effects of soil-structure interaction on construction stage analysis of highway bridges

  • Ates, Sevket;Atmaca, Barbaros;Yildirim, Erdal;Demiroz, Nurcan Asci
    • Computers and Concrete
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    • v.12 no.2
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    • pp.169-186
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    • 2013
  • The aim of this paper is to determine the effect of soil-structure interaction and time dependent material properties on behavior of concrete box-girder highway bridges. Two different finite element analyses, one stage and construction stage, have been carried out on Komurhan Bridge between Elazi$\breve{g}$ and Malatya province of Turkey, over Fırat River. The one stage analysis assume that structure was built in a second and material properties of structure not change under different loads and site conditions during time. However, construction stage analysis considers that construction time and time dependent material properties. The main and side spans of bridge are 135 m and 76 m, respectively. The bridge had been constructed in 3 years between 1983 and 1986 by balanced cantilever construction method. The parameters of soil-structure interaction (SSI), time dependent material properties and construction method are taken into consideration in the construction stage analysis while SSI is single parameter taking into consideration in the one stage analysis. The 3D finite element model of bridge is created the commercial program of SAP2000. Time dependent material properties are elasticity modulus, creep and shrinkage for concrete and relaxation for steel. Soft, medium, and firm soils are selected for evaluating SSI in both analyses. The results of two different finite element analyses are compared with each other. It is seen that both construction stage and SSI have a remarkable effect on the structural behavior of the bridge.

The Study of Finite Element Method for Analyses of Travelling Magnetic Field Problem (운동자계 문제의 해석을 위한 유한요소법에 관한 연구)

  • Chang Ho-Sung
    • Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.19 no.4
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    • pp.108-116
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    • 2005
  • This paper presents finite element analyses solution in the travelling magnetic field problem. The travelling magnetic field problem is subject to convective-diffusion equation. Therefore, the solution derived from Galerkin-FEM with linear interpolation function may oscillate between the adjacent nodes. A simple model with Dirichlet, Neumann and Periodic boundary condition respectively, have been analyzed to investigate stabilities of solutions. It is concluded that the solution of Galerkin-FEM may oscillate according to boundary condition and element type, but that of Upwind-FFM is stable regardless boundary condition.

Stress Analysis of Curved Portions of Pipe Loops Used in Ships and Offshore Structures (선박 해양구조물 파이프 루프 곡선부의 응력 해석)

  • Park, Chi-Mo;Bae, Byoung-Il
    • Journal of Ocean Engineering and Technology
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    • v.25 no.5
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    • pp.52-57
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    • 2011
  • Most ships and offshore structures are equipped with a variety of pipes, which inevitably contain curved portions. While it has been a usual practice to conduct bending stress analyses of these curved pipes using the straight-beam theory, this paper adopts two different types of finite elements, straight-beam elements and two-dimensional shell elements, for finite element analyses of a variety of curved pipes. It then compares the analysis results for two different types of elements to determine correction factors, which can be used to transform the bending displacements and bending stresses obtained by straight-beam elements to those obtainable by two-dimensional shell elements. The paper ends with a practical suggestion on how to efficiently use these correction factors to estimate the combined axial and normal stresses in a curved portion of a pipe.

Clamping Analysis and Design of a Package of a Microwave Oven (전자레인지 포장품의 클램핑 해석 및 설계)

  • Lee, Boo-Youn;Son, Byung-Sam
    • Journal of the Korean Society for Precision Engineering
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    • v.26 no.3
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    • pp.113-121
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    • 2009
  • Behavior of a package of a microwave oven under the clamping condition is evaluated by tests and the finite element analyses. PAM-CRASH software is used for the finite element analyses. Results of the analyses are compared with those of the tests and accuracy is shown to be favorable. Under the clamping condition of the original design, severe deformation occurs and an improved design of the outer case and upper EPS(Expandable Poly Styrene) is proposed to reduce it. Face beads of the outer case are introduced and shape of the upper EPS is modified to reduce the deformation resulting from the clamping load. The improved design model is analyzed and its deformation is shown to be satisfactory. A prototype is produced according to the improved design and tests are performed. Results of the clamping test of the prototype show that the plastic deformation is removed totally.

A Study on the Measurement of the Crack Length for the Real Scale Pipe Specimen (실배관 시험편의 균열 길이 측정에 관한 연구)

  • Park, Jae-Sil;Seok, Chang-Sung
    • Proceedings of the KSME Conference
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    • 2003.04a
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    • pp.397-402
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    • 2003
  • Fracture resistance curves for concerned materials are required in order to perform elastic-plastic fracture mechanical analyses. Fracture resistance curve is built with J-integral values and crack extension values. The objective of this paper is to apply the load ratio method to the measurement of the crack length for the real scale pipe specimen. For these, the fracture test using the real scale pipe specimen and finite element analyses were performed. A 4-point bending jig was manufactured for the pipe test and the direct current potential drop method and the load ratio method was used to measure the crack extension and the length for the real scale pipe test. Finite element analyses about the compliance of the pipe specimen were executed for applying the load ratio method according to the crack length.

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Strain localization and failure load predictions of geosynthetic reinforced soil structures

  • Alsaleh, Mustafa;Kitsabunnarat, Akadet;Helwany, Sam
    • Interaction and multiscale mechanics
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    • v.2 no.3
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    • pp.235-261
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    • 2009
  • This study illustrates the differences between the elasto-plastic cap model and Lade's model with Cosserat rotation through the analyses of two large-scale geosynthetic-reinforced soil (GRS) retaining wall tests that were brought to failure using a monotonically increasing surcharge pressure. The finite element analyses with Lade's model were able to reasonably simulate the large-scale plane strain laboratory tests. On average, the finite element analyses gave reasonably good agreement with the experimental results in terms of global performances and shear band occurrences. In contrast, the cap model was not able to simulate the development of shear banding in the tests. In both test simulations the cap model predicted failure loads that were substantially less than the measured ones.