• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.5
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• pp.1915-1933
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• 2013

In this study, the virtual fixed point analysis and 3D fully modeling analysis for bent pile structures are conducted by considering various influencing factors and the applicability of the virtual fixed point theory is discussed. Also, the optimized column-pile length ratio is analyzed for supplementing virtual fixed point design and examining a more exact behavior of bent pile structures by taking into account the major influencing parameters such as pile length, column and pile diameter, reinforcement ratio and soil conditions. To obtain the detailed information, the settlement and lateral deflection of the virtual fixed point theory are smaller than those of 3D fully modeling analysis. On the other hand, the virtual fixed point analysis overestimates the axial force and bending moment compared with 3D fully modeling analysis. It is shown that the virtual fixed point analysis cannot adequately predict the real behavior of bent pile structures. Therefore, it is necessary that 3D fully modeling analysis is considered for the exact design of bent pile structures. In this study, the emphasis is on quantifying an improved design method (optimized column-pile length ratio) of bent pile structures developed by considering the relation between the column-pile length ratio and allowable lateral deflection criteria. It can be effectively used to perform a more economical and improved design of bent pile structures.

• Structural Engineering and Mechanics
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• v.67 no.4
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• pp.417-425
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• 2018

The main aim of this paper is to investigate the bending of Euler-Bernouilli nano-beams made of bi-directional functionally graded materials (BDFGMs) using Eringen's non-local elasticity theory in the integral form with compare the differential form. To the best of the researchers' knowledge, in the literature, there is no study carried out into integral form of Eringen's non-local elasticity theory for bending analysis of BDFGM Euler-Bernoulli nano-beams with arbitrary functions. Material properties of nano-beam are assumed to change along the thickness and length directions according to arbitrary function. The approximate analytical solutions to the bending analysis of the BDFG nano-beam are derived by using the Rayleigh-Ritz method. The differential form of Eringen's non-local elasticity theory reveals with increasing size effect parameter, the flexibility of the nano-beam decreases, that this is unreasonable. This problem has been resolved in the integral form of the Eringen's model. For all boundary conditions, it is clearly seen that the integral form of Eringen's model predicts the softening effect of the non-local parameter as expected. Finally, the effects of changes of some important parameters such as material length scale, BDFG index on the values of deflection of nano-beam are studied.

• Structural Engineering and Mechanics
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• v.83 no.6
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• pp.757-770
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• 2022

In this paper, the vibration of a moderately thick plate to a moving mass is investigated. Pasternak foundation with a variable subgrade modulus is considered to tackle the shortcomings of Winkler model, and an analytical-numerical solution is proposed based on the eigenfunction expansion method. Parametric studies by using both CPT (Classical Plate Theory) and FSDT (First-Order Shear Deformation Plate Theory) are carried out, and, the differences between them are also highlighted. The obtained results reveal that utilizing FSDT without considering the rotary inertia leads to a smaller deflection in comparison with CPT pertaining to a thin plate, while it demonstrates a greater response for plates of higher thicknesses. Moreover, it is shown that CPT is unable to properly capture the variation of the plate thickness, thereby diminishing the accuracy as the thickness increases. The outcomes also indicate that the presence of a foundation contributes more to the dynamic response of thin plates in comparison to moderately thick plates. Furthermore, the findings suggest that the performance of the moving force approach for a moderately thick plate, in contrast to a thin plate, appears to be acceptable and it even provides a much better estimation in the presence of a foundation.

• Advances in nano research
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• v.12 no.2
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• pp.117-137
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• 2022

Effect of thickness stretching on free vibration, bending and buckling behavior of carbon nanotubes reinforced composite (CNTRC) laminated nanoplates rested on new variable elastic foundation is investigated in this paper using a developed four-unknown quasi-3D higher-order shear deformation theory (HSDT). The key feature of this theoretical formulation is that, in addition to considering the thickness stretching effect, the number of unknowns of the displacement field is reduced to four, and which is more than five in the other models. Two new forms of CNTs reinforcement distribution are proposed and analyzed based on cosine functions. By considering the higher-order nonlocal strain gradient theory, microstructure and length scale influences are included. Variational method is developed to derive the governing equation and Galerkin method is employed to derive an analytical solution of governing equilibrium equations. Two-dimensional variable Winkler elastic foundation is suggested in this study for the first time. A parametric study is executed to determine the impact of the reinforcement patterns, nonlocal parameter, length scale parameter, side-t-thickness ratio and aspect ratio, elastic foundation and various boundary conditions on bending, buckling and free vibration responses of the CNTRC plate.

• Advances in nano research
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• v.12 no.2
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• pp.139-150
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• 2022

This paper presents sets of explicit analytical equations that compute the static displacements of nanobeams by adopting the nonlocal elasticity theory of Eringen within the framework of Euler Bernoulli and Timoshenko beam theories. Castigliano's theorem is applied to an equivalent Virtual Local Beam (VLB) made up of linear elastic material to compute the displacements. The first derivative of the complementary energy of the VLB with respect to a virtual point load provides displacements. The displacements of the VLB are assumed equal to those of the nonlocal beam if nonlocal effects are superposed as additional stress resultants on the VLB. The illustrative equations of displacements are relevant to a few types of loadings combined with a few common boundary conditions. Several equations of displacements, thus derived, matched precisely in similar cases with the equations obtained by other analytical methods found in the literature. Furthermore, magnitudes of maximum displacements are also in excellent agreement with those computed by other numerical methods. These validated the superposition of nonlocal effects on the VLB and the accuracy of the derived equations.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.7
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• pp.3207-3215
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• 2012

In this paper, we study the bending and free vibration analysis of nano plate, using a nonlocal elasticity theory of Eringen with a third-order shear deformation theory. This theory has ability to capture the both small scale effects and quadratic variation of shear strain and consequently shear stress through the plate thickness. Analytical solutions of bending and vibration of a laminated composite nano plate are presented using this theory to illustrate the effect of nonlocal theory on deflection of the nano plates. The relations between nonlocal third-order and local theories are discussed by numerical results. Further, effects of (i) nonlocal parameters, (ii) laminate schemes, (iii) directions of the fiber angle and (iv) number of layers on nondimensional deflections are investigated. In order to validate the present solutions, the reference solutions are used and discussed. The results of anisotropic nano plates using the nonlocal theory may be the benchmark test for the bending analysis.

• Coupled systems mechanics
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• v.7 no.5
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• pp.635-647
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• 2018

Dynamic problems arising from the Euler-Bernoulli beam model with inhomogeneous elastic properties are considered. The method of Green's function and perturbation theory are employed to find the deflection in the beam correct to the first-order. Eigenvalue problems appearing from transverse vibrations of inhomogeneous beams in linear and nonlinear cases are also discussed.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.307-310
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• 1999

In this panel test, the toughness and post-cracking tensile strength of SFRC(Steel Fiber Reinforced Concrete) measured on 24 panels(size; 60cm $\times$ 60cm $\times$ 10cm) which are the basic characteristics than can determine the load bearing capacity of SFRC are investigated. Those values are calculated using load-deflection curves and load-absorbed energy curves. Post-cracking tensile strength of SFRC in this study are determined by yield line theory. From the test results, it is seen that the higher the volume of steel fiber is, the higher the absorbed energy is.

• Advances in Computational Design
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• v.3 no.1
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• pp.1-16
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• 2018

The decaying temperature and dynamic response of a thermoelastic nanobeam subjected to a moving load has been investigated in the context of generalized theory of nonlocal thermoelasticity. The transformed distributions of deflection, temperature, axial displacement and bending moment are obtained by using Laplace transformation. By applying a numerical inversion method, the results of these fields are then inverted and obtained in the physical domain. Also, for a particular two models, numerical results are discussed and presented graphically. Some specific and special results are derived from the current study.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.05a
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• pp.315-319
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• 2004

Static and dynamic responses of micro cantilever beam structures undertaking electrostatic forces are obtained employing Galerkin's method based on Euler beam theory. Variations of static and dynamic responses as well as resonant frequencies are estimated for several sets of beam properties and applied voltages. It is shown that the applied voltage influences the deflection and the modal characteristics significantly. Such information can be usefully employed for the design of MEMS structures.