• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.4
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• pp.245-253
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• 2020

In this study, natural frequencies are compared using several pile-soil interaction (PSI) models to evaluate the effects of each model on resonance safety checks for a monopile type of wind turbine structure. Base spring, distributed spring, and three-dimensional brick-shell models represented the PSIs in the finite element model. To analyze the effects of the PSI models on a natural frequency, after a stiffness matrix calculation and Winkler-based beam model for base spring and distributed spring models were presented, respectively; natural frequencies from these models were investigated for monopiles with different geometries and soil properties. These results were compared with those from the brick-shell model. The results show that differences in the first natural frequency of the monopiles from each model are small when the small diameter of monopile penetrates hard soil and rock, while the distributed spring model can over-estimate the natural frequency for large monopiles installed in weak soil. Thus, an appropriate PSI model for natural frequency analyses should be adopted by considering soil conditions and structure scale.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.17 no.1
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• pp.41-46
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• 2005

The seismic response characteristics of a port structure were investigated by the earthquake analyses of the structure subjected to high-, low-frequency component, and Uljin earthquakes. In the Fluid-Structure-Soil Interaction(FSSI) analysis, the fluid is modeled by the 4-node quadrilateral element which is a modification of a structural plane element, and the port structure and foundation is modelled by the plane strain element. Since the present method directly models the fluid-structure-soil interaction system using finite element method, it can be easily applied to the dynamic analysis of a 2-D fluid-port-soil system with complex geometry. The results of the seismic coefficient. added mass, and FSSI methods are compared. The results showed that the earthquake with high frequency components more affects the seismic response of the structure than that of low frequency components.

• Structural Engineering and Mechanics
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• v.92 no.1
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• pp.25-52
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• 2024

In the current paper, the various responses of concrete rectangular liquid storage containers under seismic load, each isolated by a lead-rubber bearing subjected to bi-directional earthquake forces are investigated. A parametric study is conducted to investigate the effects of isolation period, yield strength of the isolator and the effects of soil-foundation interaction for non-isolated and base-isolated tanks located on different soil types. In most cases, the value of base shear, base moment, wall displacement and hydrodynamic pressure is reduced by the effect of the isolators whose effective frequency is within the appropriate range. The sloshing displacement is amplified due to seismic isolation of the tanks for both tall and shallow tank configurations. Also, it is found that the seismic isolation technique is more efficient for the more flexible tank. Studying various soil types indicates that, unlike the responses of non-isolated tanks which change drastically for different soil types, the responses of base-isolated structures are less affected. Finally, it is observed that the variation in structural responses is not only related to the superstructure configuration and bearings properties but also depends on the earthquake specifications.

• Structural Engineering and Mechanics
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• v.58 no.5
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• pp.887-903
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• 2016

This study analyses the seismic response of a three-dimensional (3-D) rigid massless square foundation resting or embedded in a viscoelastic soil limited by rigid bedrock. The foundation is subjected to harmonic oblique seismic waves P, SV, SH and R. The key step is the characterization of the soil-foundation interaction by computing the impedance matrix and the input motion matrix. A 3-D frequency boundary element method (BEM) in conjunction with the thin layer method (TLM) is adapted for the seismic analysis of the foundation. The dynamic response of the rigid foundation is solved from the wave equations by taking into account the soil-foundation interaction. The solution is formulated using the frequency BEM with the Green's function obtained from the TLM. This approach has been applied to analyze the effect of soilstructure interaction on the seismic response of the foundation as a function of the kind of incident waves, the angles of incident waves, the wave's frequencies and the embedding of foundation. The parametric results show that the non-vertical incident waves, the embedment of foundation, and the wave's frequencies have important impact on the dynamic response of rigid foundations.

• Geomechanics and Engineering
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• v.2 no.4
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• pp.229-252
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• 2010

In this paper, Soil-Structure Interaction (SSI) effect is investigated using a new and integrated approach. Faster solution of time dependant differential equation of motion is achieved using numerical representation of wavelet theory while dynamic Infinite Elements (IFE) concept is utilized to effectively model the unbounded soil domain. Combination of the wavelet theory with IFE concept lead to a robust, efficient and integrated technique for the solution of complex problems. A direct method for soil-structure interaction analysis in a two dimensional medium is also presented in time domain using the frequency dependent transformation matrix. This matrix which represents the far field region is constructed by assembling stiffness matrices of the frequency dependant infinite elements. It maps the problem into the time domain where the equations of motion are to be solved. Accuracy of results obtained in this study is compared to those obtained by other SSI analysis techniques. It is shown that the solution procedure discussed in this paper is reliable, efficient and less time consuming as compared to other existing concepts and procedures.

• Earthquakes and Structures
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• v.25 no.2
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• pp.99-112
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• 2023

This paper investigates the influences of Soil-Structure Interaction (SSI) on the seismic behavior of two-dimensional reinforced concrete moment-resisting frames subjected to Far-Field Ground Motion (FFGM) and Near-Field Ground Motion (NFGM). For this purpose, the nonlinear modeling of 7, 10, and 15-story reinforced concrete moment resisting frames were developed in Open Systems for Earthquake Engineering Simulation (OpenSees) software. Effects of SSI were studied by simulating Beam on Nonlinear Winkler Foundation (BNWF) and the soil type as homogenous medium-dense. Generally, the building resistance to seismic loads can be explained in terms of Incremental Dynamic Analysis (IDA); therefore, IDA curves are presented in this study. For comparison, the fragility evaluation is subjected to NFGM and FFGM as proposed by Quantification of Building Seismic Performance Factors (FEMA P-695). The seismic performance of Reinforced Concrete (RC) buildings with fixed and flexible foundations was evaluated to assess the probability of collapse. The results of this paper demonstrate that SSI and NFGM have significantly influenced the probability of failure of the RC frames. In particular, the flexible-base RC buildings experience higher Spectral acceleration (Sa) compared to the fixed-base ones subjected to FFGM and NFGM.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.563-580
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• 2012

We modify the formulation of a recently developed absorbing boundary condition (ABC), the perfectly matched discrete layers (PMDL), to incorporate the excitation coming from the exterior such as earthquake waves. The modified formulation indicates that the effect of the exterior excitation can be incorporated into PMDL ABCs (traditionally designed to treat only interior excitation) simply by applying appropriate forces on the nodes connected to the first PMDL layer. Numerical results are presented to clearly illustrate the effectiveness of the proposed method.

• Journal of Ocean Engineering and Technology
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• v.30 no.6
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• pp.505-519
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• 2016

If the seabed is exposed to high waves for a long period, the pore water pressure may be excessive, making the seabed subject to liquefaction. As the water pressure change due to wave action is transmitted to the pore water pressure of the seabed, a phase difference will occur because of the fluid resistance from water permeability. Thus, the effective stress of the seabed will be decreased. If a composite breakwater or other structure with large wave reflection is installed over the seabed, a partial standing wave field is formed, and thus larger wave loading is directly transmitted to the seabed, which considerably influences its stability. To analyze the 3-D dynamic response characteristics of the seabed around a composite breakwater, this study performed a numerical simulation by applying LES-WASS-3D to directly analyze the wave-structure-soil interaction. First, the waveform around the composite breakwater and the pore water pressure in the seabed and rubble mound were compared and verified using the results of existing experiments. In addition, the characteristics of the wave field were analyzed around the composite breakwater, where there was an opening under different incident wave conditions. To analyze the effect of the changed wave field on the 3-D dynamic response of the seabed, the correlation between the wave height distribution and pore water pressure distribution of the seabed was investigated. Finally, the numerical results for the perpendicular phase difference of the pore water pressure were aggregated to understand the characteristics of the 3-D dynamic response of the seabed around the composite breakwater in relation to the water-structure-soil interaction.

• Geomechanics and Engineering
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• v.34 no.5
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• pp.529-545
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• 2023

The coupled soil-pile-structure seismic response is recently in the spotlight of researchers because of its extensive applications in the different fields of engineering such as bridges, offshore platforms, wind turbines, and buildings. In this paper, a simple analytical model is developed to evaluate the dynamic performance of seismically isolated bridges considering triple interactions of soil, piles, and bridges simultaneously. Novel expressions are proposed to present the dynamic behavior of pile groups in inhomogeneous soils with various shear modulus along with depth. Both cohesive and cohesionless soil deposits can be simulated by this analytical model with a generalized function of varied shear modulus along the soil depth belonging to an inhomogeneous stratum. The methodology is discussed in detail and validated by rigorous dynamic solution of 3D continuum modeling, and time history analysis of centrifuge tests. The proposed analytical model accuracy is guaranteed by the acceptable agreement between the experimental/numerical and analytical results. A comparison of the proposed linear model results with nonlinear centrifuge tests showed that during moderate (frequent) earthquakes the relative differences in responses of the superstructure and the pile cap can be ignored. However, during strong excitations, the response calculated in the linear time history analysis is always lower than the real conditions with the nonlinear behavior of the soil-pile-bridge system. The current simple and efficient method provides the accuracy and the least computational costs in comparison to the full three-dimensional analyses.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.361-368
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• 2000

This paper demonstrates how nonlinear soil behavior in a soil-structure interaction system can be realistically incorporated by using a hybrid method in a nonlinear time-domain analysis. The hybrid method employs a general-purpose nonlinear finite element program coupled with a linear SSI program for the unbounded layered soil medium In order to verify the validity and applicability of the hybrid method, nonlinear earthquake response analyses are carried out for the Hualien free-field problem, in which the ground and underground accelerations were measured during several earthquake events, and for a 2-D subway station. It is found that the nonlinear earthquake responses predicted for the Hualien free-field using the hybrid method compare very well with the observed responses whereas the subway station example gives reasonable results.