• Title/Summary/Keyword: distinct boundary conditions

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Stability and instability in responses of a concrete disk with non-classical boundary conditions

  • Lian Xue;Mostafa Habibi;Chaohai Ou
    • Advances in concrete construction
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    • v.18 no.5
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    • pp.355-368
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    • 2024
  • This paper conducts an in-depth investigation into the stability and instability responses of a nanocomposite-reinforced concrete disk, analyzed under unconventional boundary conditions. The study centers on the dynamic behavior and critical buckling features, influenced by the integration of nanomaterials into the concrete matrix. By employing both analytical techniques and numerical simulations, the research assesses the impact of nanocomposite reinforcement on the disk's structural performance across a range of loading scenarios. The non-classical boundary conditions, characterized by atypical constraints and support systems distinct from standard fixed or simply supported conditions, are shown to play a pivotal role in determining the disk's critical load and stability thresholds. Such boundary conditions, which frequently arise in practical applications, significantly influence the disk's stability and load-bearing capacity. The paper also delves into the material properties of the nanocomposites, highlighting their improved stiffness, toughness, and mechanical performance, which contribute to enhancing the structure's overall strength. Through a parametric study, the research thoroughly examines the effects of variables such as nanomaterial volume fraction, disk geometry, and boundary support type. The results indicate a complex interaction between reinforcement, geometry, and boundary conditions, which may lead to instability in specific configurations. This investigation provides valuable insights for optimizing the design of nanocomposite-reinforced concrete structures and offers recommendations for enhancing their structural stability and integrity in practical applications. The findings advance the understanding of the mechanical behavior of nanocomposite materials under non-standard boundary conditions.

Nonlinear Displacement Discontinuity Model for Generalized Rayleigh Wave in Contact Interface

  • Kim, No-Hyu;Yang, Seung-Yong
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.6
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    • pp.582-590
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    • 2007
  • Imperfectly jointed interface serves as mechanical waveguide for elastic waves and gives rise to two distinct kinds of guided wave propagating along the interface. Contact acoustic nonlinearity (CAN) is known to plays major role in the generation of these interface waves called generalized Rayleigh waves in non-welded interface. Closed crack is modeled as non-welded interface that has nonlinear discontinuity condition in displacement across its boundary. Mathematical analysis of boundary conditions and wave equation is conducted to investigate the dispersive characteristics of the interface waves. Existence of the generalized Rayleigh wave(interface wave) in nonlinear contact interface is verified in theory where the dispersion equation for the interface wave is formulated and analyzed. It reveals that the interface waves have two distinct modes and that the phase velocity of anti-symmetric wave mode is highly dependent on contact conditions represented by linear and nonlinear dimensionless specific stiffness.

A Study on Distinct Element Modelling of Dilatant Rock Joints (팽창성 암석절리의 개별요소 모델링에 관한 연구)

  • 장석부;문현구
    • Tunnel and Underground Space
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    • v.5 no.1
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    • pp.1-10
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    • 1995
  • The behavior of a jointed rock mass depends mainly on the geometrical and mechanical properties of joints. The failure mode of a rock mass and kinematics of rock blocks are governed by the orientation, spacing, and persistence of joints. The mechanical properties such as dilation angle, shear strength, maximum closure, strength of asperities and friction coeffiient play important roles on the stability and deformation of the rock mass. The normal and shear behaviour of a joint are coupled due to dilation, and the joint deformation depends also on the boundary conditions such as stiffness conditons. In this paper, the joint constitutive law including the dilatant behaviour of a joint is numerically modelled using the edge-to-edge contact logic in distinct element method. Also, presented is the method to quantify the input parameters used in the joint law. The results from uniaxial compression and direct shear tests using the numeical model of the single joint were compared to the analytic results from them. The boundary effect on the behaviour of a joint is verified by comparing the results of direct shear test under constant stress boundary condition with those under constant stiffness boundary condition. The numerical model developed is applied to a complex jointed rock mass to examine its performance and to evaluate the effect of joint dilation on tunnel stability.

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ANALYSIS OF TWOPHASE FLOW MODEL EQUATIONS

  • Jin, Hyeonseong
    • Honam Mathematical Journal
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    • v.36 no.1
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    • pp.11-27
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    • 2014
  • In this paper, we propose closures for multi-phase flow models, which satisfy boundary conditions and conservation constraints. The models governing the evolution of the fluid mixing are derived by applying an ensemble averaging procedure to the microphysical equations characterized by distinct phases. We consider compressible multi species multi-phase flow with surface tension and transport.

Investigating vibrational behavior of graphene sheets under linearly varying in-plane bending load based on the nonlocal strain gradient theory

  • Shariati, Ali;Barati, Mohammad Reza;Ebrahimi, Farzad;Singhal, Abhinav;Toghroli, Ali
    • Advances in nano research
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    • v.8 no.4
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    • pp.265-276
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    • 2020
  • A study that primarily focuses on nonlocal strain gradient plate model for the sole purpose of vibration examination, for graphene sheets under linearly variable in-plane mechanical loads. To study a better or more precise examination on graphene sheets, a new advance model was conducted which carries two scale parameters that happen to be related to the nonlocal as well as the strain gradient influences. Through the usage of two-variable shear deformation plate approach, that does not require the inclusion of shear correction factors, the graphene sheet is designed. Based on Hamilton's principle, fundamental expressions in regard to a nonlocal strain gradient graphene sheet on elastic half-space is originated. A Galerkin's technique is applied to resolve the fundamental expressions for distinct boundary conditions. Influence of distinct factors which can be in-plane loading, length scale parameter, load factor, elastic foundation, boundary conditions, and nonlocal parameter on vibration properties of the graphene sheets then undergo investigation.

Influence of geometry and loading conditions on the dynamics of martensitic fronts

  • Berezovski, Arkadi
    • Smart Structures and Systems
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    • v.4 no.2
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    • pp.123-135
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    • 2008
  • Damping capacity of SMA damping devices is simulated numerically under distinct geometry and loading conditions. Two-dimensional numerical simulations are performed on the basis of a phenomenological model of dynamics of martensite-austenite phase boundaries. Results of the simulations predict the time delay and the value of the stress transferred to other parts of a construction by a damper device.

SORET AND CHEMICAL REACTION EFFECTS ON THE RADIATIVE MHD FLOW FROM AN INFINITE VERTICAL POROUS PLATE

  • MALAPATI, VENKATESWARLU;DASARI, VENKATA LAKSHMI
    • Journal of the Korean Society for Industrial and Applied Mathematics
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    • v.21 no.1
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    • pp.39-61
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    • 2017
  • In this present article, we analyzed the heat and mass transfer characteristics of the nonlinear unsteady radiative MHD flow of a viscous, incompressible and electrically conducting fluid past an infinite vertical porous plate under the influence of Soret and chemical reaction effects. The effect of physical parameters are accounted for two distinct types of thermal boundary conditions namely prescribed uniform wall temperature thermal boundary condition and prescribed heat flux thermal boundary condition. Based on the flow nature, the dimensionless flow governing equations are resolved to harmonic and non harmonic parts. In particular skin friction coefficient, Nusselt number and Sherwood number are found to evolve into their steady state case in the large time limit. Parametric study of the solutions are conducted and discussed.

Geometric optimization of the D-shape gallery openings on high arch dams against strong ground motions

  • Murat Cavuslu;Tuna Ulger;Berna Aksoy
    • Structural Engineering and Mechanics
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    • v.92 no.5
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    • pp.433-452
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    • 2024
  • Arch dams are often preferred in narrow, high valleys due to their distinctively high and curved geometries, making them particularly effective for water retention. Consequently, assessing the seismic performance of these critical structures is essential. The presence of gallery openings within arch dams further heightens research interest, especially in regions of high seismic activity. This study presents a detailed three-dimensional (3D) numerical failure analysis of the Ermenek Dam, one of Turkey's largest arch dams. Using the finite-difference method, a 3D model is constructed, incorporating four distinct D-shaped gallery openings within the dam body. These openings are integrated into the model using specialized FLAC3D fish functions. To enhance simulation accuracy, the foundation is proportionally extended along the dam's base and sides. The Burgers creep material model is applied to assess both creep behavior and seismic response within the concrete body and foundation. Non-reflecting boundary conditions are imposed on the model boundaries to create realistic constraints. Numerical analyses are conducted on various gallery dimensions, evaluating 28 distinct geometries under ten different strong ground motions. The seismic analysis results indicate that damage may occur within the dam body when gallery height exceeds twice its width. Therefore, careful consideration of the geometrical dimensions of gallery openings is highly recommended during the modeling and analysis of arch dams.

Two-dimensional rod theory for approximate analysis of building structures

  • Takabatake, Hideo
    • Earthquakes and Structures
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    • v.1 no.1
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    • pp.1-19
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    • 2010
  • It has been known that one-dimensional rod theory is very effective as a simplified analytical approach to large scale or complicated structures such as high-rise buildings, in preliminary design stages. It replaces an original structure by a one-dimensional rod which has an equivalent stiffness in terms of global properties. If the structure is composed of distinct constituents of different stiffness such as coupled walls with opening, structural behavior is significantly governed by the local variation of stiffness. This paper proposes an extended version of the rod theory which accounts for the two-dimensional local variation of structural stiffness; viz, variation in the transverse direction as well as longitudinal stiffness distribution. The governing equation for the two-dimensional rod theory is formulated from Hamilton's principle by making use of a displacement function which satisfies continuity conditions across the boundary between the distinct structural components in the transverse direction. Validity of the proposed theory is confirmed by comparison with numerical results of computational tools in the cases of static, free vibration and forced vibration problems for various structures.

Stability of the Grain Configurations of Thin Films-a Model for Agglomeration (박막내 결정립 배열의 열적 불안정성1)-응집 모델)

  • Na, Jong-Ju;Park, Jung-Geun
    • 연구논문집
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    • s.27
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    • pp.183-200
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    • 1997
  • We have calculated the energy of three distinct grain configurations, namely completely connected, partially connected and unconnected configurations, evolving during a spheroidization of polycrystalline thin film by extending a geometrical model due to Miller et al. to the case of spheroidization at both the surface and film-substrate interface. "Stabilitl" diagram defining a stable region of each grain configuration has been established in terms of the ratio of grain size to film thickness vs. equilibrium wetting or dihedral angles at various interface energy conditions. The occurrence of spheroidization at the film-substrate interface significantly enlarges the stable region of unconnected grain configuration thereby greatly facilitating the occurrence of agglomeration. Complete separation of grain boundary is increasingly difficult with a reduction of equilibrium wetting angle. The condition for the occurrence of agglomeration differs depending on the equilibrium wetting or dihedral angles. The agglomeration occurs, at low equilibrium angles, via partially connected configuration containing stable holes centered at grain boundary vertices, whereas it occurs directly via completely connected configuration at large equilibrium angles except for the case having small surface and/or film-substrate interface energy. The initiation condition of agglomeration is defined by the equilibrium boundary condition between the partially connected and unconnected configurations for the former case, whereas it can, for the latter case, largely deviate from the equilibrium boundary condition between the completely connected and unconnected configurations because of the presence of a finite energy barrier to overcome to reach the unconnected grain configuration.

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