Jae-Min Kim

Dynamic Infinite Elements for Soil-Structure Interaction Analysis in a Layered Soil Medium

This paper presents dynamic infinite element formulations which have been developed for soil-structure interaction analysis both in frequency and in time domains by the present authors and our colleagues during the past twenty years. Axisymmetric, 2D and 3D layered half-space soil media were considered in the developments. The displacement shape functions of the infinite elements were established using approximate expressions of analytical solutions in frequency domain to represent the characteristics of multiple waves propagating into the unbounded outer domain of the media. The shape functions were determined in terms of the excitation frequency as well as the spatial and material characteristics of the far-field soil region. Thereby the element mass and stiffness matrices become frequency dependent. As far as time domain analysis, the shape functions were further simplified to obtain closed-form frequency-dependent mass and stiffness matrices, which can analytically be transformed into time domain terms by a continuous Fourier transform. The proposed infinite elements were verified using benchmark examples, which showed that the present formulations are very effective for the soil-structure interaction analysis either in frequency or in time domain. Example applications to actual soil-structure interaction problems are also given to demonstrate the capability and versatility of the present methodology. kg]Key Words

Large-scale 3D SSI Analysis using KIESSI-3D Program

Abstract The soil-structure interaction(SSI) effect should be considered to accurately assess the seismic response of structure constructed on soft soil site other than the hard bedrock. Recently, the demand of SSI analysis has increased due to strengthening of the regulatory guidelines of nuclear power plant such as the USNRC SRP 3.7.2. In this study an accuracy and running time of the KIESSI-3D program for large-scale 3D SSI analysis were investigated. The seismic SSI analysis using the KIESSI-3D program was performed for several examples of large-scale three-dimensional soil-structure interaction system. The analysis results were compared with those of the ACS/SASSI program. Good agreements in transfer functions at selected locations showd that KIESSI-3D yields accurate solution for large-scale SSI problem. Moreover, it was found that running speed of the KIESSI-3D for large-scale 3D SSI analysis is much faster than that of the ACS/SASSI about 30～2000 times. Keywords :KIESSI-3D, soil-structure interaction, dynamic infinite element, PARDISO, seismic design

Verification of Linear FE Model for Nonlinear SSI Analysis by Boundary Reaction Method

Abstract In this paper, a coupling scheme for applying finite element analysis(FEA) programs, such as, LS-DYNA and MIDAS/Civil, to a nonlinear soil structure interaction analysis by the boundary reaction method(BRM) is presented. With the FEA programs, the structure and soil media are discretized by linear or nonlinear finite elements. To absorb the outgoing elastic waves to unbounded soil region as much as possible, the PML elements and viscous-spring elements are used at the outer FE boundary, in the LS-DYNA model and in MIDAS/Civil model, respectively. It is also assumed that all the nonlinear elements in the problem are limited to structural region. In this study, the boundary reaction forces for the use in the BRM are calculated using the KIESSI-3D program by solving soil-foundation interaction problem subjected to incident seismic waves. The effectiveness of the proposed approach is demonstrated with a linear SSI seismic analysis problem by comparing the BRM solution with the conventional SSI solution. Numerical comparison indicates that the BRM can effectively be applied to a nonlinear soil-structure analysis if motions at the foundation obtained by the BRM for a linear SSI problem excluding the nonlinear structure is conservative.

Seismic Response Analysis for Three Dimensional Soil-structure Interaction System using Dynamic Infinite Elements

This paper presents a seismic analysis technique for a 3D soil-structure interaction system in a frequency domain, based on the finite element formulation incorporating frequency-dependent infinite elements for the far field soil region. Earthquake input motions are regarded as traveling P, SV and SH waves which are incident vertically from the far-field soil region, and then equivalent earthquake forces are calculated using impedances of infinite soil by dynamic infinite elements and traction and displacement from free field response analysis. For verification and application, seismic response analyses are carried out for a multi-layered soil medium without structure and a typical nuclear power plant in consideration of soil-structure interaction. The results are compared with the free field response using a one-dimensional analytic solution, and a dynamic response of an example structure from another SSI package.