• Title/Summary/Keyword: numerical formulation

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Theoretical formulation for vehicle-bridge interaction analysis based on perturbation method

  • Tan, Yongchao;Cao, Liang;Li, Jiang
    • Structural Engineering and Mechanics
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    • v.82 no.2
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    • pp.191-204
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    • 2022
  • A three-mass vehicle model including one rigid mass and two unsprung masses is adopted to predict the vehicle-bridge interaction (VBI) and to establish the nonlinear coupled governing equations. To overcome the numerical instability and large computation problems concerning the vehicle-bridge system, the perturbation method is used to convert the nonlinear coupled governing equations into a set of linear uncoupled equations. Formulas for bridge's natural frequencies considering both the VBI and the dynamic responses of bridge and vehicle are proposed. Compared with the numerical results obtained by the Newmark-β method, the theoretical solutions for natural frequencies and dynamic responses are validated. The effects of the important factors of unsprung mass, vehicle damping, surface irregularity on the natural frequencies and dynamic responses of bridge and vehicle are discussed, based on the theoretical solutions.

Easy function for solving linear elasticity problems

  • Rezaiee-Pajand, Mohammad;Karimipour, Arash
    • Structural Engineering and Mechanics
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    • v.81 no.3
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    • pp.335-348
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    • 2022
  • It is well known that after finding the displacement in the structural mechanics, strain and stress can be obtained in the straight-forward process. The main purpose of this paper is to unify the displacement functions for solving the solid body. By performing mathematical operations, three sets of these key relationships are found in this paper. All of them are written in the Cartesian Coordinates and in terms of a simple function. Both analytical and numerical approaches are utilized to validate the correctness of the presented formulations. Since all required conditions for the bodies with self-equilibrated loadings are satisfied accurately, the authors' relations can solve these kinds of problems. This fact is studied in-depth by solving some numerical examples. It is found that a very simple function can be used for each formulation instead of ten different and complex displacement potentials defined by previous studies.

Semi-numerical simulation for effects of different loadings on vibration behavior of 2D systems

  • Rao, Li;Lin, Chao;Zhang, Chenglin
    • Structural Engineering and Mechanics
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    • v.81 no.3
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    • pp.259-266
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    • 2022
  • Based upon differential quadrature method (DQM) and nonlocal strain gradient theory (NSGT), an investigation on the free vibrations of 2D plate systems with nano-dimensions has been provided taking into account the effects of different mechanical loadings. In order to capture different mechanical loadings, a general form of variable compressive load applied in the axial direction of the plate system has been introduced. The studied plate has been constructed from two types of particles which results in graded material properties and nanoscale pores. The established formulation for the plate is in the context of a novel shear deformable model and the equations have been solved via a semi-numerical trend. Presented results indicate the prominence of material composition, nonlocal coefficient, strain gradient coefficient and boundary conditions on vibrational frequencies of nano-size plate.

Artificial Resort Beach Development and Numerical Analysis (인공휴양해변개발과 수치실험분석)

  • Lee, Joong Woo;Jeong, Myoeng Seon
    • Journal of Korean Port Research
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    • v.4 no.1
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    • pp.21-31
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    • 1990
  • The application of computer model to the port and harbor development is categorized in the field of port development policy, economic analysis and evaluation, civil engineering analysis, hydrodynamic analysis, evaluation of social and natural environment effect, etc. The study in this paper, however, is limited to hydrodynamic analysis, especially the analysis of water wave propagation and response to the shore structure due to the construction and implementation of shore boundary, the mathematical formulation of the numerical model is established systematically based on the hybrid Element Method and applied to solving the wave refraction, diffraction and radiation problems for a circular basin, the artificial beach or lagoon in terms of coastal zone development.

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AN IMPROVED ALTERNATIVE WENO SCHEMES WITH PERTURBATIONAL TERMS FOR THE HYPERBOLIC CONSERVATION LAWS

  • KUNMIN SUNG;YOUNGSOO HA;MYUNGJOO KANG
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.27 no.4
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    • pp.207-231
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    • 2023
  • This paper aims to improve the alternative formulation of the fifth- and sixth-order accurate weighted essentially non-oscillatory (AWENO) finite difference schemes. The first is to derive the AWENO scheme with sixth-order accuracy in the smooth region of the solution. Second, a new weighted polynomial functions combining the perturbed forms with conserved variable to the AWENO is constructed; the new form of tunable functions are invented to maintain non-oscillatory property. Detailed numerical experiments are presented to illustrate the behavior of the new perturbational AWENO schemes. The performance of the present scheme is evaluated in terms of accuracy and resolution of discontinuities using a variety of one and two-dimensional test cases. We show that the resulted perturbational AWENO schemes can achieve fifth- and sixth-order accuracy in smooth regions while reducing numerical dissipation significantly near singularities.

Time varying LQR-based optimal control of geometrically exact Reissner's beam model

  • Suljo Ljukovac;Adnan Ibrahimbegovic;Maida Cohodar-Husic
    • Coupled systems mechanics
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    • v.13 no.1
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    • pp.73-93
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    • 2024
  • In this work, we propose combining an advanced optimal control algorithm with a geometrically exact beam model. For simplicity, the 2D Reissner beam model is chosen to represent large displacements and rotations. The difficulty pertains to the nonlinear nature of beam kinematics affecting the tangent stiffness matrix, making it non-constant, which compromises direct use of optimal control methods for linear problems. Thus, we seek to accommodate a time varying control using linear-quadratic regulator (LQR) algorithm with the proposed geometrically nonlinear beam model. We provide a detailed theoretical formulation and its numerical implementation in a variational format form. Several illustrative numerical examples are provided to confirm an excellent performance of the proposed methodology.

Nonlinear Analysis of Reinforced Concrete Shells(II) (철근(鐵筋)콘크리트 쉘구조(構造)의 비선형(非線型) 해석(解析)(II))

  • Kim, Woon Hak;Shin, Hyun Mock;Shin, Hyun Mook
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.11 no.1
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    • pp.79-87
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    • 1991
  • An efficient numerical procedure for material and geometric nonlinear analysis of reinforced concrete shells under monotonically increasing loads through their elastic, inelastic and ultimate load ranges is developed by using the finite element method. The 8-node Serendipity isoparametric element developed by the degeneration approach including the transverse shear deformation is used. A layered approach is used to represent the steel reinforcement and to discretize the concrete behavior through the thickness. The total Lagrangian formulation based upon the simplified Von Karman strain expressions is used to take into account the geometric nonlinearity of the structure. The material nonlinearities are taken into account by comprising the tension, compression, and shear models of cracked concrete and a model for reinforcement in the concrete; and also a so-called smeared crack model is incorporated. The steel reinforcement is assumed to be in a uniaxial stress state and is modelled as a smeared layer of equivalent thickness. This method will be verified a useful tool to account for geometric and material nonlinearities in detailed analysis of reinforced concrete concrete shells of general form through numerical examples of the sequential paper( ).

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Bending analysis of functionally graded thick plates with in-plane stiffness variation

  • Mazari, Ali;Attia, Amina;Sekkal, Mohamed;Kaci, Abdelhakim;Tounsi, Abdelouahed;Bousahla, Abdelmoumen Anis;Mahmoud, S.R.
    • Structural Engineering and Mechanics
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    • v.68 no.4
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    • pp.409-421
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    • 2018
  • In the present paper, functionally graded (FG) materials are presented to investigate the bending analysis of simply supported plates. It is assumed that the material properties of the plate vary through their length according to the power-law form. The displacement field of the present model is selected based on quasi-3D hyperbolic shear deformation theory. By splitting the deflection into bending, shear and stretching parts, the number of unknowns and equations of motion of the present formulation is reduced and hence makes them simple to use. Governing equations are derived from the principle of virtual displacements. Numerical results for deflections and stresses of powerly graded plates under simply supported boundary conditions are presented. The accuracy of the present formulation is demonstrated by comparing the computed results with those available in the literature. As conclusion, this theory is as accurate as other shear deformation theories and so it becomes more attractive due to smaller number of unknowns. Some numerical results are provided to examine the effects of the material gradation, shear deformation on the static behavior of FG plates with variation of material stiffness through their length.

Free-surface Boundary Condition in Time-domain Elastic Wave Modeling Using Displacement-based Finite-difference Method (시간영역 변위근사 유한차분법의 자유면 경계조건)

  • Min Dong-Joo;Yoo Hai Soo
    • Geophysics and Geophysical Exploration
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    • v.6 no.2
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    • pp.77-86
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    • 2003
  • We designed a new time-domain, finite-difference, elastic wave modeling technique, based on a displacement formulation. which yields nearly correct solutions to Lamb's problem. Unlike the conventional, displacement-based, finite-difference method using a node-based grid set (where both displacements and material properties such as density and Lame constants are assigned to nodal points), in our new finite-difference method, we use a cell-based grid set (where displacements are still defined at nodal points but material properties within cells). In the case of using the cell-based grid set, stress-free conditions at the free surface are naturally described by the changes in the material properties without any additional free-surface boundary condition. Through numerical tests, we confirmed that the new second-order finite differences formulated in the cell-based grid let generate numerical solutions compatible with analytic solutions unlike the old second-order finite-differences formulated in the node-based grid set.

Formulation of Fully Coupled THM Behavior in Unsaturated Soil (불포화지반에 대한 열-수리-역학 거동의 수식화)

  • Shin, Ho-Sung
    • Journal of the Korean Geotechnical Society
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    • v.27 no.3
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    • pp.75-83
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    • 2011
  • Emerging issues related with fully coupled Thermo-Hydro-Mechanical (THM) behavior of unsaturated soil demand the development of a numerical tool in diverse geo-mechanical and geo-environmental areas. This paper presents general governing equations for coupled THM processes in unsaturated porous media. Coupled partial differential equations are derived from three mass balances equations (solid, water, and air), energy balance equation, and force equilibrium equation. With Galerkin formulation and time integration of these governing equations, finite element code is developed to find nonlinear solution of four main variables (displacement-u, gas pressure-$P_g$), liquid pressure-$P_1$), and temperature-T) using Newton's iterative scheme. Three cases of numerical simulations are conducted and discussed: one-dimensional drainage experiments (u-$P_g-P_1$), thermal consolidation (u-$P_1$-T), and effect of pile on surrounding soil due to surface temperature variation (u-$P_1$-T).