• Title/Summary/Keyword: variable foundation

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Wave propagation in FG polymer composite nanoplates embedded in variable elastic medium

  • Ahmed Kadiri;Mohamed Bendaida;Amina Attia;Mohammed Balubaid;S. R. Mahmoud;Abdelmoumen Anis Bousahla;Abdeldjebbar Tounsi;Fouad Bourada;Abdelouahed Tounsi
    • Advances in nano research
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    • v.17 no.3
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    • pp.235-248
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    • 2024
  • This study explores the transmission of waves through polymer composite nanoplates situated on varying elastic foundations. The reinforcement of these nanoplates is assured by graphene nanoplatelets (GNP). Furthermore, the material's behavior is assessed using the Halpin-Tsai model, while the precise representations of stress and strain effects are ensured by the four variables higher order shear deformation theory. The equations of motion are obtained and resolved through the application of Hamilton's principle and the trial function. The study examines how different factors, like the nonlocal parameter, strain gradient parameter, weight fraction, and variable elastic foundations affect the outcomes of wave propagation in nanoplates. This thorough investigation offers valuable insights into the difficult behavior of wave dynamics in nanoplates, this has led to substantial advancements in engineering applications for the future.

The Effects of Parenting Attitudes on Peer Attachment in Early Adolescents : Focusing on Moderating Effects of Gender in Convergence Era (부모의 양육태도가 초기 청소년의 또래애착에 미치는 영향 : 융복합 시대에 성별 조절효과를 중심으로)

  • Lee, Eun-Hee;Yang, Yi-Jung
    • Journal of Convergence for Information Technology
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    • v.8 no.2
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    • pp.37-44
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    • 2018
  • This study examined the moderating effects of gender on the influences of parental parenting attitudes on peer attachment in early adolescents. Data analysis was conducted over 1,912 respondents who met the purpose of this study among Korean Youth Panel KCYPS 7th year data of 1st grade in elementary school. The research methods examined the influence of variables on dependent variable, with difference of gender influences. As a result, it was found that gender, the control variable, and overall grade satisfaction affected peer attachment. Second, positive and negative parenting attitudes have confirmed positive and negative effects on peer attachment. Third, moderating effect was confirmed as parenting attitudes by gender show the difference of impact on peer attachment. Therefore, this study suggest to apply it to practical and theoretical implications and basic data for the program development to improve youth peer relations.

Reliability-Based Design of Shallow Foundations Considering The Probability Distribution Types of Random Variables (확률변수의 분포특성을 고려한 얕은기초 신뢰성 설계)

  • Kim, Chang-Dong;Kim, Soo-Il;Lee, Jun-Hwan;Kim, Byung-Il
    • Journal of the Korean Geotechnical Society
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    • v.24 no.1
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    • pp.119-130
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    • 2008
  • Uncertainties in physical and engineering parameters for the design of shallow foundations arise from various aspects such as inherent variability and measurement error. This paper aims at investigating and reducing uncertainty from deterministic method by using the reliability-based design of shallow foundations accounting for the variation of various design parameters. A probability distribution type and statistics of random variables such as unit weight, cohesion, infernal friction angle and Young's modulus in geotechnical engineering are suggested to calculate the ultimate bearing capacities and immediate settlements of foundations. Reliability index and probability of failure are estimated based on the distribution types of random variables. Widths of foundation are calculated at target reliability index and probability of failure. It is found that application and analysis of the best-fit distribution type for each random variables are more effective than adoption of the normal distribution type in optimizing the reliability-based design of shallow foundations.

Dynamics of graphene-nanoplatelets reinforced composite nanoplates including different boundary conditions

  • Karami, Behrouz;Shahsavari, Davood;Ordookhani, Ali;Gheisari, Parastoo;Li, Li;Eyvazian, Arameh
    • Steel and Composite Structures
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    • v.36 no.6
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    • pp.689-702
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    • 2020
  • The current study deals with the size-dependent free vibration analysis of graphene nanoplatelets (GNPs) reinforced polymer nanocomposite plates resting on Pasternak elastic foundation containing different boundary conditions. Based on a four variable refined shear deformation plate theory, which considers shear deformation effect, in conjunction with the Eringen nonlocal elasticity theory, which contains size-dependency inside nanostructures, the equations of motion are established through Hamilton's principle. Moreover, the effective material properties are estimated via the Halpin-Tsai model as well as the rule of mixture. Galerkin's mathematical formulation is utilized to solve the equations of motion for the vibrational problem with different boundary conditions. Parametrical examples demonstrate the influences of nonlocal parameter, total number of layers, weight fraction and geometry of GNPs, elastic foundation parameter, and boundary conditions on the frequency characteristic of the GNPs reinforced nanoplates in detail.

Theoretical investigation on vibration frequency of sandwich plate with PFRC core and piezomagnetic face sheets under variable in-plane load

  • Arani, Ali Ghorbanpour;Maraghi, Zahra Khoddami;Ferasatmanesh, Maryam
    • Structural Engineering and Mechanics
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    • v.63 no.1
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    • pp.65-76
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    • 2017
  • This research investigated the vibration frequency of sandwich plate made of piezoelectric fiber reinforced composite core (PFRC) and face sheets of piezomagnetic materials. The effective electroelastic constants for PFRC materials are obtained by the micromechanical approach. The resting medium of sandwich plate is modeled by Pasternak foundation including normal and shear modulus. Besides, sandwich plate is subjected to linearly varying normal stresses that change by load factor. The coupled equations of motion are derived using first order shear deformation theory (FSDT) and energy method. These equations are solved by differential quadrature method (DQM) for simply supported boundary condition. A detailed numerical study is carried out based on piezoelectricity theory to indicate the significant effect of load factor, volume fraction of fibers, modulus of elastic foundation, core-to-face sheet thickness ratio and composite materials on dimensionless frequency of sandwich plate. These findings can be used to aerospace, building and automotive industries.

Vibration Analysis of Smart Embedded Shear Deformable Nonhomogeneous Piezoelectric Nanoscale Beams based on Nonlocal Elasticity Theory

  • Ebrahimi, Farzad;Barati, Mohammad Reza;Zenkour, Ashraf M.
    • International Journal of Aeronautical and Space Sciences
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    • v.18 no.2
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    • pp.255-269
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    • 2017
  • Free vibration analysis is presented for a simply-supported, functionally graded piezoelectric (FGP) nanobeam embedded on elastic foundation in the framework of third order parabolic shear deformation beam theory. Effective electro-mechanical properties of FGP nanobeam are supposed to be variable throughout the thickness based on power-law model. To incorporate the small size effects into the local model, Eringen's nonlocal elasticity theory is adopted. Analytical solution is implemented to solve the size-dependent buckling analysis of FGP nanobeams based upon a higher order shear deformation beam theory where coupled equations obtained using Hamilton's principle exist for such beams. Some numerical results for natural frequencies of the FGP nanobeams are prepared, which include the influences of elastic coefficients of foundation, electric voltage, material and geometrical parameters and mode number. This study is motivated by the absence of articles in the technical literature and provides beneficial results for accurate FGP structures design.

A novel nonlocal refined plate theory for stability response of orthotropic single-layer graphene sheet resting on elastic medium

  • Yazid, Miloud;Heireche, Houari;Tounsi, Abdelouahed;Bousahla, Abdelmoumen Anis;Houari, Mohammed Sid Ahmed
    • Smart Structures and Systems
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    • v.21 no.1
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    • pp.15-25
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    • 2018
  • This work presents the buckling investigation of embedded orthotropic nanoplates such as graphene by employing a new refined plate theory and nonlocal small-scale effects. The elastic foundation is modeled as two-parameter Pasternak foundation. The proposed two-variable refined plate theory takes account of transverse shear influences and parabolic variation of the transverse shear strains within the thickness of the plate by introducing undetermined integral terms, hence it is unnecessary to use shear correction factors. Nonlocal governing equations for the single layered graphene sheet are obtained from the principle of virtual displacements. The proposed theory is compared with other plate theories. Analytical solutions for buckling loads are obtained for single-layered graphene sheets with isotropic and orthotropic properties. The results presented in this study may provide useful guidance for design of orthotropic graphene based nanodevices that make use of the buckling properties of orthotropic nanoplates.

Distortional buckling of I-steel concrete composite beams in negative moment area

  • Zhou, Wangbao;Li, Shujin;Huang, Zhi;Jiang, Lizhong
    • Steel and Composite Structures
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    • v.20 no.1
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    • pp.57-70
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    • 2016
  • The predominant type of buckling that I-steel concrete composite beams experience in the negative moment area is distortional buckling. The key factors that affect distortional buckling are the torsional and lateral restraints by the bottom flange. This study thoroughly investigates the equivalent lateral and torsional restraint stiffnesses of the bottom flange of an I-steel concrete composite beam under negative moments. The results show a coupling effect between the applied forces and the lateral and torsional restraint stiffnesses of the bottom flange. A formula is proposed to calculate the critical buckling stress of the I-steel concrete composite beams under negative moments by considering the lateral and torsional restraint stiffnesses of the bottom flange. The proposed method is shown to better predict the critical bending moment of the I-steel composite beams. This article introduces an improved method to calculate the elastic foundation beams, which takes into account the lateral and torsional restraint stiffnesses of the bottom flange and considers the coupling effect between them. The results show a close match in results from the calculation method proposed in this paper and the ANSYS finite element method, which validates the proposed calculation method. The proposed calculation method provides a theoretical basis for further research on distortional buckling and the ultimate resistance of I-steel concrete composite beams under a variable axial force.

Nonlinear bending analysis of porous FG thick annular/circular nanoplate based on modified couple stress and two-variable shear deformation theory using GDQM

  • Sadoughifar, Amirmahmoud;Farhatnia, Fatemeh;Izadinia, Mohsen;Talaeitaba, Sayed Behzad
    • Steel and Composite Structures
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    • v.33 no.2
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    • pp.307-318
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    • 2019
  • This is the first attempt to consider the nonlinear bending analysis of porous functionally graded (FG) thick annular and circular nanoplates resting on Kerr foundation. The size effects are captured based on modified couple stress theory (MCST). The material properties of the porous FG nanostructure are assumed to vary smoothly through the thickness according to a power law distribution of the volume fraction of the constituent materials. The elastic medium is modeled by Kerr elastic foundation which consists of two spring layers and one shear layer. The governing equations are extracted based on Hamilton's principle and two variables refined plate theory. Utilizing generalized differential quadrature method (GDQM), the nonlinear static behavior of the nanostructure is obtained under different boundary conditions. The effects of various parameters such as material length scale parameter, boundary conditions, and geometrical parameters of the nanoplate, elastic medium constants, porosity and FG index are shown on the nonlinear deflection of the annular and circular nanoplates. The results indicate that with increasing the material length scale parameter, the nonlinear deflection is decreased. In addition, the dimensionless nonlinear deflection of the porous annular nanoplate is diminished with the increase of porosity parameter. It is hoped that the present work may provide a benchmark in the study of nonlinear static behavior of porous nanoplates.

In-plane varying bending force effects on wave dispersion characteristics of single-layered graphene sheets

  • Cao, Yan;Selmi, Abdellatif;Tohfenamarvar, Rasoul;Zandi, Yousef;Kasehchi, Ehsan;Assilzahed, Hamid
    • Advances in nano research
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    • v.10 no.2
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    • pp.101-114
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    • 2021
  • An analytical investigation has been performed on the mechanical performance of waves propagated in a Single-Layered Graphene Sheet (SLGS) when an In-plane Varying Bending (IVB) load is interacted. It has been supposed that the Graphene Sheet (GS) is located on an elastic medium. Employing a two-parameter elastic foundation, the effects of elastic substrate on the GS behavior are modeled. Besides, the kinematic equations are derived by the means of a trigonometric two-variable refined plate theory. Moreover, in order to indicate the size-dependency of the SLGS, a Nonlocal Strain Gradient Theory (NSGT) was considered. The nonlocal governing differential equations are achieved in the framework of Hamilton's Principle (HP). Also, an analytical approach was used to detect the unknowns of the final eigenvalue equation. Finally, the effects of each parameters using some dispersion charts were determined.