• Earthquakes and Structures
• /
• v.22 no.5
• /
• pp.447-460
• /
• 2022

In this article, wave propagation in functional gradation plates (FG) resting on an elastic foundation with two parameters is studied using a new quasi-three-dimensional (3D) higher shear deformation theory (HSDT). The new qausi-3D HSOT has only five variables in fields displacement, which means has few numbers of unknowns compared with others quasi-3D. This higher shear deformation theory (HSDT) includes shear deformation and effect stretching with satisfying the boundary conditions of zero traction on the surfaces of the FG plate without the need for shear correction factors. The FG plates are considered to rest on the Winkler layer, which is interconnected with a Pasternak shear layer. The properties of the material graded for the plates are supposed to vary smoothly, with the power and the exponential law, in the z-direction. By based on Hamilton's principle, we derive the governing equations of FG plates resting on an elastic foundation, which are then solved analytically to obtain the dispersion relations. Numerical results are presented in the form of graphs and tables to demonstrate the effectiveness of the current quasi-3D theory and to analyze the effect of the elastic foundation on wave propagation in FG plates.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.8
• /
• pp.753-760
• /
• 2010

In this paper, the lifting analysis of a floating crane with a shipbuilding block is performed. Since floating cranes are operated in ocean waves, six degree-of-freedom motions are considered in the dynamic equations of motions of the floating crane and the block. The boom of the floating crane is considered as an elastic body in the analysis, and is modeled as three dimensional beam based on the finite element formulation. The hydrostatic and hydrodynamic forces by a regular wave are considered as external forces. By solving the equations of motions numerically, the dynamic responses of the floating crane and the block are simulated. The simulation results with different wave directions are compared and the conditions which cause maximum responses are discussed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.29 no.6A
• /
• pp.641-650
• /
• 2009

This paper presents new equations for member forces in concrete floating structures under wave loadings. The currently adopted design equations for wave loadings disregard the effect of mismatch between design wave length and the length of the structure. In most cases, however, additional internal forces occur due to disequilibriating buoyancy caused by the difference between design wave length and the length of the structure. In this study, new design equations considering the influence of the disequlibriating buoyancy is proposed. In addition, finite element solutions are sought to demonstrate the adequacy of the proposed design formulae in estimating the actual internal forces considering the structure as either rigid or flexible. It has been found that member forces are decreased approximately to around 55% for flexible model when compared with the rigid one.

• Coupled systems mechanics
• /
• v.12 no.1
• /
• pp.41-68
• /
• 2023

The present work is concerned with the study of the influence of inhomogeneous initial stresses in a hollow cylinder containing a compressible inviscid fluid on the propagation of axisymmetric longitudinal waves propagating in this cylinder. The study is carried out using the so-called three-dimensional linearized theory of elastic waves in bodies with initial stresses to describe the motion of the cylinder and using the linearized Euler equations to describe the flow of the compressible inviscid fluid. It is assumed that the inhomogeneous initial stresses in the cylinder are caused by the internal pressure of the fluid. To solve the corresponding eigenvalue problem, the discrete-analytic solution method is applied and the corresponding dispersion equation is obtained, which is solved numerically, after which the corresponding dispersion curves are constructed and analyzed. To obtain these dispersion curves, parameters characterizing the magnitude of the internal pressure, the ratio of the sound velocities in the cylinder material and in the fluid, and the ratio of the material densities of the fluid and the cylinder are introduced. Based on these parameters, the influence of the inhomogeneous initial stresses in the cylinder on the dispersion of the above-mentioned waves in the considered hydro-elastic system is investigated. Moreover, based on these results, appropriate conclusions about this influence are drawn. In particular, it is found that the character of the influence depends on the wavelength. Accordingly, the inhomogeneous initial stresses before (after) a certain value of the wavelength lead to a decrease (increase) of the wave propagation velocity in the zeroth and first modes.

• Journal of the Society of Naval Architects of Korea
• /
• v.47 no.3
• /
• pp.421-429
• /
• 2010

In this paper, in order to analyze the dynamic response of a floating crane when it lifts a heavy cargo, the boom of the floating crane is considered as an elastic beam. The boom is divided into elements based on finite element formulation and the floating frame of reference formulation and nodal coordinates are employed to model the boom as a flexible body. As an extension of the previous study, in order to consider spatial motion in waves, the coupled equations of motions of the 6 degree of freedom (DOF) floating crane and 6 DOF cargo are developed based on the flexible multibody system dynamics. The 3 dimensional deformation of the elastic boom is considered with 18 DOF. The dynamic simulation of the floating crane and the cargo is performed under regular wave conditions with various cargo weights. Finally, the effects of the elastic boom on lifting cargo are discussed by comparing the simulation results between the elastic boom and a rigid boom.

• Geomechanics and Engineering
• /
• v.5 no.6
• /
• pp.595-611
• /
• 2013

This paper presents a three-dimensional (3D) integrated numerical model where the wave-induced pore pressures in a porous seabed around breakwater heads were investigated. Unlike previous research, the Navier-Stokes equation is solved with internal wave generation for the flow model, while Biot's dynamic seabed behaviour is considered in the seabed model. With the present model, a parametric study was conducted to examine the effects of wave and soil characteristics and breakwater configuration on the wave-induced pore pressure around breakwater heads. Based on numerical examples, it was found that the wave-induced pore pressures at breakwater heads are greater than that beneath a breakwater. The wave-induced seabed response around breakwater heads become more important with: (i) a longer wave period; (ii) a seabed with higher permeability and degree of saturation; and (iii) larger angle between the incident waves and breakwater. Furthermore, the relative difference of wave-induced pore pressure between fully-dynamic and quasi-static solutions are larger at breakwater heads than that beneath a breakwater.

• Tunnel and Underground Space
• /
• v.23 no.3
• /
• pp.212-218
• /
• 2013

Tuff specimens were thermally treated with predetermined temperatures of 200, 400 and $600^{\circ}C$ to construct specimens simulating weathered tuff rocks. Specific gravity, absorption ratio, elastic wave velocity, uniaxial compressive strength, Brazilian tensile strength, Young's modulus, Poisson's ratio and slake-durability index were measured for pre-heated specimens. Heating of rock specimens entailed the degradation of material properties except for slake-durability index. It was found that correlations among P-wave velocity, uniaxial compressive strength, Brazilian tensile strength, Young's modulus and absorption ratio are high. Regression equations which use the P-wave velocity as an independent variable were presented to evaluate uniaxial compressive strength, Brazilian tensile strength, Young's modulus and absorption ratio.

• Coupled systems mechanics
• /
• v.10 no.1
• /
• pp.39-60
• /
• 2021

The present paper is concerned with the study of nonlinear ultrasonic waves in a magneto thermo (MT) elastic armchair single-walled carbon nanotube (ASWCNT) resting on polymer matrix. The analytical formulation is developed based on Eringen's nonlocal elasticity theory to account small scale effect. After developing the formal solution of the mathematical model consisting of partial differential equations, the frequency equations have been analyzed numerically by using the nonlinear foundations supported by Winkler-Pasternak model. The solution is obtained by ultrasonic wave dispersion relations. Parametric work is carried out to scrutinize the influence of the non local scaling, magneto-mechanical loadings, foundation parameters, various boundary condition and length on the dimensionless frequency of nanotube. It is noticed that the boundary conditions, nonlocal parameter, and tube geometrical parameters have significant effects on dimensionless frequency of nano tubes. The results presented in this study can provide mechanism for the study and design of the nano devices like component of nano oscillators, micro wave absorbing, nano-electron technology and nano-electro- magneto-mechanical systems (NEMMS) that make use of the wave propagation properties of armchair single-walled carbon nanotubes embedded on polymer matrix.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.2 no.2
• /
• pp.77-85
• /
• 1998

Propagation of elastic surface waves in anisotropic media is considered in this study. An analytical technique is proposed to study the scattering of surface waves at the interface between two anisotropic quarter-spaces. The Green's function technique is used to derive a system of equations which can determine the scattering coefficients at the interface. A numerical study is carried out and the trade-offs between the material anisotropy and inhomogeneity are studied.

• Steel and Composite Structures
• /
• v.34 no.4
• /
• pp.599-613
• /
• 2020

In this article, free vibration attributes of double-walled carbon nanotubes based on nonlocal elastic shell model have been investigated. For this purpose, a nonlocal Flügge shell model is established to observe the small scale effect. The wave propagation is employed to frame the governing equations as eigenvalue system. The influence of nonlocal parameter subjected to different end supports has been overtly examined. A suitable choice of material properties and nonlocal parameter been focused to analyze the vibration characteristics. The new set of inner and outer tubes radii investigated in detail against aspect ratio and length. The dominance of boundary conditions via nonlocal parameter is shown graphically. The results generated furnish the evidence regarding applicability of nonlocal shell model and also verified by earlier published literature.