• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.04a
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• pp.121-128
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• 1999

This paper presents a time domain method for soil-structure interaction analysis for seismic loadings. It is based on the finite element formulation incorporating analytical frequency-dependent infinite elements for the far field soil. The dynamic stiffness matrices of the far field region formulated using the present method in frequency domain can be easily transformed into the corresponding matrices in time domain. At first, the equivalent earthquake forces are evaluated along the interface between the near and the far fields from the free-field response analysis carried out in frequency domain, and the results are transformed into the time domain. An efficient procedure is developed for the convolution integrals to evaluate the interaction force along the interface, which depends on the response on the interface at the past time instances as well as the concurrent instance. Then, the dynamic responses are obtained for the equivalent earthquake force and the interaction force using Newmark direct integration technique. Since the response analysis is carried out in time domain, it can be easily extended to the nonlinear analysis. Example analysis has been carried out to verify the present method in a multi-layered half-space.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.1
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• pp.161-169
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• 1995

One of the most influential factors on estimating the complex modulus by using longitudinal vibration of a rod-type specimen is the accuracy of the approximate models for describing the dynamic behavior of the specimen. Performance of several approximate models is investigated analytically on the basis of the Pochhammer-Chree theory in case of infinite specimen and numerically on the basis of the finite element analysis in case of finite specimen. The frequency range where each model gives good approximation and its accuracy in that range are determined.

• Structural Engineering and Mechanics
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• v.49 no.1
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• pp.1-22
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• 2014

A seismic evaluation is made of the response to horizontal ground shaking of cantilever retaining walls using the finite element model in three dimensional space whose verification is provided analytically through the modal analysis technique in case of the assumptions of fixed base, complete bonding behavior at the wall-soil interface, and elastic behavior of soil. Thanks to the versatility of the finite element model, the retained medium is then idealized as a uniform, elastoplastic stratum of constant thickness and semi-infinite extent in the horizontal direction considering debonding behavior at the interface in order to perform comprehensive soil-structure interaction (SSI) analyses. The parameters varied include the flexibility of the wall, the properties of the soil medium, and the characteristics of the ground motion. Two different finite element models corresponding with flexible and rigid wall configurations are studied for six different soil types under the effects of two different ground motions. The response quantities examined incorporate the lateral displacements of the wall relative to the moving base and the stresses in the wall in all directions. The results show that the wall flexibility and soil properties have a major effect on seismic behavior of cantilever retaining walls and should be considered in design criteria of cantilever walls. Furthermore, the results of the numerical investigations are expected to be useful for the better understanding and the optimization of seismic design of this particular type of retaining structure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.2
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• pp.207-216
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• 2003

In this paper, the finite element method for the elastodynamic axisymmetric fracture analysis is presented in matrix form through the application of the Galerkin method to the time integral equations of motion with no inertia forces. Isoparametric quadratic quadrilateral element and triangular crack tip singular elements with one-quarter node are used in the mesh division of the finite element model. To show the validity and accuracy of the proposed method, the infinite elastic medium with the penny shaped crack is solved first and compared with the analytical solution and the numerical results by the finite difference method and the boundary element method existing in the published literatures, and then the dynamic stress intensity factors of solid and hollow cylinders of finite dimensions haying penny-shaped cracks and internal and external circumferential tracks are computed in detail.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.471-482
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• 2016

In this study, we focused on a speed-up of KIESSI-3D program, which is based on FE-IE techniques, by introducing a p-version dynamic infinite element method. In order to evaluate performance of the KIESSI-3D, numerical analyses for eight real-scale SSI problems are carried out. We considered three types of KIESSI-3D numerical models whose radii of near-field soil region($r_0$)are 1.2, 1.5, and 3.0 times of basemat radius of structure(R). In addition, SSI analyses using the SASSI2010 program are carried out used for comparison of accuracy and runtime against those of the KIESSI-3D. Numerical results show that the KIESSI-3D model of $r_0=1.2R$ is enough to give accurate solution. In view of the computing speed, the new KIESSI-3D was up to 25 times faster than the old KIESSI-3D.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.5
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• pp.521-532
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• 2007

Elastic wave propagations in the semi-infinite transversely isotropic cylinder under various kinds of longitudinal impact loads are analyzed using the axisymmetric finite element method and Houbolt time-integration scheme. For which the finite element program is newly constructed and verified through the comparison of present numerical results with those by other researchers. E-type glass-epoxy composite cylinders with different fiber volume fractions are adopted and studied in detail with dynamic responses of the isotropic cylinder. Three dimensional wave motions are given in graphic form to show the realistic view of the wave propagation. Nondimensionalized dynamic characteristic variables which relate the size of finite element mesh, the time step, and the wave speed are presented for obtaining accurate and stable numerical results.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.971-977
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• 2005

Power Flow Analysis (PFA) is developed for the effective predictions of frequency-averaged vibrational response in medium-to-high frequency ranges. In PFA, the power coefficients of semi-infinite structure and for-field energy density are used to predict the vibrational responses of structures. Generally, at high frequencies, PFA can predict narrow-band frequency-averaged vibrational responses of built-up structures. However, in low- to medium frequency ranges, the dynamic responses obtained by PFA represent broad-band frequency-averaged vibrational energy densities. For the prediction of vibrational response variance in Power Flow Finite Element Method (PFFEM), the variances of input power and joint element matrix describing structural coupling relationship are derived. Finally, for the validity of developed formulation, numerical examples for two co-planer plates are performed and the vibrational response variance of the structure are compared with the results of classical and PFFEM solutions.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.427-434
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• 2000

This paper presents a computer program for a 2-D fluid-structure-soil interaction analysis. With this computer program the fluid can be modeled by a spurious free 4-node displacement-based fluid element which uses rotational penalty and mass projection technique in conjunction with the one point reduced integration scheme to remove the spurious zero energy modes. The structure and near field soil are discretized by the standard finite elements while the unbounded far field soil are discretized by the standard finite elements while the unbounded far field soil is represented by the frequency dependent dynamic infinite elements. Sine this method models directly the fluid-structure-soil system it can be applied to the dynamci analysis of 2-D liquid storage structure with complex geometry. For the purpose of verification dynamic analyses for tanks on a rigid foundation and on compliant embankment are carried out. Comparison of the present results with those by ANSYS program shows good agreement.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.241-246
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• 1996

A new solution for the dynamic analysis of as asphalt concrete pavements under moving loads has been developed. The asphalt concrete pavement can be modeled in elastic or viscoelastic medium of multi-layered structure. The subgrade can be modeled as either a rigid base or a semi-infinite halfspace. The loads may be constant or arbitrary circular loads into one direction. The method utilizes the Complex Response Method of transient analysis with a continuum solution in the horizontal direction and a finite-element solution in the vertical direction. This proposed method incorporates such important factors as wave propagation, inertia and damping effects of the medium as well as frequency-dependent asphalt concrete properties. The proposed method has been validted with the full-scale field truck test, which was conducted on instrumented asphalt concrete section on a test track at PACCAR Technical Center in Mount Vernon, Washington. Comparison with field strain data from full-scale pavement tests has shown excellent agreement. Theoretical results have shown that the effect of vehicle speed is significant and that it is in part due to the frequency-dependent

• International Journal of Highway Engineering
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• v.10 no.4
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• pp.213-224
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• 2008

Flexible pavement responses to vehicular loading, such as critical stresses and strains, in each pavement layer, could be predicted by the multilayered elastic analysis. However, multilayered elastic theory suffers from major drawbacks including spatial dimension of a numerical model, material properties considered in the analysis, boundary conditions, and ill-presentation of tire-pavement contact shape and stresses. To overcome these shortcomings, three-dimensional finite element (3D FE) models are developed and numerical analyses are conducted to calculate pavement responses to moving load in this study. This paper introduces a methodology for an effective 3D FE to simulate flexible pavement structure. It also discusses the mesh development and boundary condition analysis. Sensitivity analyses of flexible pavement response to loading are conducted. The infinite boundary conditions and time-dependent history of calculated pavement responses are considered in the analysis. This study found that the outcome of 3D FE implicit dynamic analysis of flexible pavement that utilizes appropriate boundary conditions, continuous moving load, viscoelastic hot-mix asphalt model is comparable to field measurements.