• Title, Summary, Keyword: Nonlinear FEM analysis

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A Study on the Improvement of the Steel Pylon Base Design Using Nonlinear FEM Analysis (비선형 FEM 해석을 이용한 기존 강재 주탑기부 설계의 개선방안 연구)

  • Jung, Soo-Hyung;Park, Sung-Woo
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.18 no.1
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    • pp.19-30
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    • 2014
  • In this study nonlinear FEM analysis for steel pylon base of a cable supported bridge is performed in order to compare the results of Akashi-Kaikyo bridge's design specification established in 1970. Due to convenience of its application, the Akashi grand bridge's design specification has been applied to the base design of cable stayed bridges. It has been using linear spring in order to model prestressed high tensioned bars between steel pylon bottom plates and the base concrete. However, the results of nonlinear FEM analysis revealed that the Akashi-Kaikyo bridge's design specification has various problems in the analysis of the steel pylon base. And the steel pylon base has various complex members connecting with each other, and it is main member to resist against the wind load or the earthquake load. Therefore, the nonlinear FEM analysis has to be conducted in order to predict the behavior of steel pylon base exactly. Also, the nonlinear FEM analysis is more reasonable for the load and resistant factor design.

Computer aided reinforcement design of RC structures

  • An, Xuehui;Maekawa, Koichi
    • Computers and Concrete
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    • v.1 no.1
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    • pp.15-30
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    • 2004
  • In this study, a design process for reinforced concrete structures using the nonlinear FEM analysis is developed. Instead of using the nonlinear analysis to evaluate the required performance after design process, the nonlinear analysis is applied before designing the reinforcement arrangement inside the RC structures. An automatic reinforcement generator for computer aided reinforcement agreement is developed for this purpose. Based on a nonlinear FEM program for analyzing the reinforced concrete structure, a smart fictitious material model of steel, is proposed which can self-adjust the reinforcement to the required amount at the cracking location according to the load increment. Using this tool, the reinforcement ratio required at design load level can be decided automatically. In this paper, an example of RC beam with opening is used to verify the proposed process. Finally, a trial design process for a real size underground RC LNG tank is introduced.

A Study on a Composite Laminate Pull-through Joint

  • Kwon, Jeong-Sik;Kim, Jin-Sung;Seo, Bum-Kyung;Lee, Soo-Yong
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.1
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    • pp.63-69
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    • 2017
  • In this paper, composite laminate pull-through resistance was analyzed using the FEM method and compared with test results. 2D and 3D simplified FEM models, a nonlinear analysis, and a progressive failure analysis utilizing three composite laminate failure theories Maximum Stress, Maximum Strain, and Tsai-Wu were used to predict the FEM results with the test results. The load and boundary conditions of the test were applied to the FEM to simulate the test. A composite laminate pull-through test (ASTM D7332 Proc. B) was designed with a special fixture to collect more precise data. The test results were compared with the FEM analysis results.

Nonlinear analysis of viscoelastic micro-composite beam with geometrical imperfection using FEM: MSGT electro-magneto-elastic bending, buckling and vibration solutions

  • Alimirzaei, S.;Mohammadimehr, M.;Tounsi, Abdelouahed
    • Structural Engineering and Mechanics
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    • v.71 no.5
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    • pp.485-502
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    • 2019
  • In this research, the nonlinear static, buckling and vibration analysis of viscoelastic micro-composite beam reinforced by various distributions of boron nitrid nanotube (BNNT) with initial geometrical imperfection by modified strain gradient theory (MSGT) using finite element method (FEM) are presented. The various distributions of BNNT are considered as UD, FG-V and FG-X and also, the extended rule of mixture is used to estimate the properties of micro-composite beam. The components of stress are dependent to mechanical, electrical and thermal terms and calculated using piezoelasticity theory. Then, the kinematic equations of micro-composite beam using the displacement fields are obtained. The governing equations of motion are derived using energy method and Hamilton's principle based on MSGT. Then, using FEM, these equations are solved. Finally the effects of different parameters such as initial geometrical imperfection, various distributions of nanotube, damping coefficient, piezoelectric constant, slenderness ratio, Winkler spring constant, Pasternak shear constant, various boundary conditions and three material length scale parameters on the behavior of nonlinear static, buckling and vibration of micro-composite beam are investigated. The results indicate that with an increase in the geometrical imperfection parameter, the stiffness of micro-composite beam increases and thus the non-dimensional nonlinear frequency of the micro structure reduces gradually.

Nonlinear static and vibration analysis of Euler-Bernoulli composite beam model reinforced by FG-SWCNT with initial geometrical imperfection using FEM

  • Mohammadimehr, M.;Alimirzaei, S.
    • Structural Engineering and Mechanics
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    • v.59 no.3
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    • pp.431-454
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    • 2016
  • In this paper, the nonlinear static and free vibration analysis of Euler-Bernoulli composite beam model reinforced by functionally graded single-walled carbon nanotubes (FG-SWCNTs) with initial geometrical imperfection under uniformly distributed load using finite element method (FEM) is investigated. The governing equations of equilibrium are derived by the Hamilton's principle and von Karman type nonlinear strain-displacement relationships are employed. Also the influences of various loadings, amplitude of the waviness, UD, USFG, and SFG distributions of carbon nanotube (CNT) and different boundary conditions on the dimensionless transverse displacements and nonlinear frequency ratio are presented. It is seen that with increasing load, the displacement of USFG beam under force loads is more than for the other states. Moreover it can be seen that the nonlinear to linear natural frequency ratio decreases with increasing aspect ratio (h/L) for UD, USFG and SFG beam. Also, it is shown that at the specified value of (h/L), the natural frequency ratio increases with the increasing the values amplitude of waviness while the dimensionless nonlinear to linear maximum deflection decreases. Moreover, with considering the amplitude of waviness, the stiffness of Euler-Bernoulli beam model reinforced by FG-CNT increases. It is concluded that the R parameter increases with increasing of volume fraction while the rate of this parameter decreases. Thus one can be obtained the optimum value of FG-CNT volume fraction to prevent from resonance phenomenon.

Nonlinear first ply failure analysis of composite skewed hypar shells using FEM

  • Ghosh, Arghya;Chakravorty, Dipankar
    • Structural Engineering and Mechanics
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    • v.68 no.1
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    • pp.81-94
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    • 2018
  • This paper uses the finite element method (FEM) considering geometrically nonlinear strains to study the first ply failure of laminated composite skewed hypar shell roofs through well-established failure criteria along with the serviceability criterion of deflection. Apart from validating the approach through solution of benchmark problems, skewed hypars with different practical parametric variations are studied for failure loads and tendencies. First ply failure zones are also identified to suggest design and non-destructive monitoring guidelines to the practising engineers. Recommendation tables regarding the design approaches to be adopted in specific cases and factor of safety values needed to be imposed on first ply failure load values for varying shell curvatures are also suggested in this paper. Providing practical inputs to design engineers is the main achievement of the present study.

Analysis of Switched Reluctance Motors using Parameters obtained by Finite Element Method (유한요소법으로 계산한 파라메타를 이용한 스위치드 릴럭턴스 모타의 해석)

  • Lee, Joon-Ho;Lee, Sang-Ho;Lee, Ki-Sik
    • Proceedings of the KIEE Conference
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    • pp.47-50
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    • 1997
  • The FEM(Finite Element Method) can be used to analysis SRM(Switched Reluctance Motor) as it can account for the salient pole geometry of the stator and rotor and the nonlinear properties of the magnetic materials. However, FEM requirers a lot of computer memory and computing time because, the kind of SRM drivers is verity and the switching strategies are various for one SRM driver. In this paper we proposed the method of analysis of a SRM which results are similar to FEM and has very short computing time. The Inductance and torque for each phase current at each rotor position are calculated by using two-dimensional nonlinear FEM analysis. Using the look-up table of inductance and torque and the voltage equations of SRM we obtained the phase current and torque. To verify proposed algorithm, 3 phase 6/4 SRM is analysed and found a good agreement with FEM results. And computing time is about 1/1600 of the FEM analysis.

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Analysis of Signal Propagation in Nonlinear Optical Fiber using SS-FEM with Sparse Matrix (희귀행렬 SS-FEM에 의한 비선형 광섬유의 전송신호 해석)

  • Jeong, Baek-Ho;Lee, Ho-Jun
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.49 no.1
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    • pp.52-58
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    • 2000
  • Signal propagation in nonlinear optical fiber is analyzed numerically by using SS-FEM (Split-Step Finite Element Method). By adopting cubic element function in FEM, soliton equation of which exact solution was well known, has been solved. Also, accuracy of numerical results and computing times are compared with those of Fourier method, and we have found that solution obtained from using FEM was very relatively accurate. Especially, to reduce CPU time in matrix computation in each step, the matrix imposed by the boundary condition is approximated as a sparse matrix. As a result, computation time was shortened even with the same or better accuracy when compared to those of the conventional FEM and Fourier method.

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수직방향 집중하중 상태의 외팔보 거동에 대한 선형 및 비선형적 해석 비교

  • Go, Jeong-U;Bin, Yeong-Bin
    • Proceeding of EDISON Challenge
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    • pp.239-245
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    • 2015
  • In this paper, to examine the difference between the linear and non-linear static, dynamic analysis for a structure, a cantilevered beam was used. Then, an external transverse static and dynamic loads were applied at the free end of the beam. Classical theories were used for the linear analysis and the EDISON CSD solver, co-rotational dynamic FEM program, was used for nonlinear analysis. In the static analysis, effects of the load for the beam deflection were observed in the linear and nonlinear analysis. Then, normalized displacement of tip of the beam was predicted for different frequency ration and a significant difference was obtained in the vicinity of the resonant frequency. In addition, effects of frequency and time for the beam deflection were investigated to find the frequency delay.

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Metal forming analysis using meshfree-enriched finite element method and mortar contact algorithm

  • Hu, Wei;Wu, C.T.
    • Interaction and multiscale mechanics
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    • v.6 no.2
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    • pp.237-255
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    • 2013
  • In this paper, a meshfree-enriched finite element method (ME-FEM) is introduced for the large deformation analysis of nonlinear path-dependent problems involving contact. In linear ME-FEM, the element formulation is established by introducing a meshfree convex approximation into the linear triangular element in 2D and linear tetrahedron element in 3D along with an enriched meshfree node. In nonlinear formulation, the area-weighted smoothing scheme for deformation gradient is then developed in conjunction with the meshfree-enriched element interpolation functions to yield a discrete divergence-free property at the integration points, which is essential to enhance the stress calculation in the stage of plastic deformation. A modified variational formulation using the smoothed deformation gradient is developed for path-dependent material analysis. In the industrial metal forming problems, the mortar contact algorithm is implemented in the explicit formulation. Since the meshfree-enriched element shape functions are constructed using the meshfree convex approximation, they pose the desired Kronecker-delta property at the element edge thus requires no special treatments in the enforcement of essential boundary condition as well as the contact conditions. As a result, this approach can be easily incorporated into a conventional displacement-based finite element code. Two elasto-plastic problems are studied and the numerical results indicated that ME-FEM is capable of delivering a volumetric locking-free and pressure oscillation-free solutions for the large deformation problems in metal forming analysis.