• Earthquakes and Structures
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• v.4 no.3
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• pp.285-297
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• 2013

The effect of soil structure interaction (SSI) on seismic response of a multi-degree-of-freedom structure isolated with a friction pendulum system (FPS) is studied. In the analysis, the soil is considered as an elastic continuum and is modeled using the finite element method. The effect of SSI on response of the structure is evaluated for twenty far-field and twenty near-fault earthquake ground motions. The effect of friction coefficient of sliding material of FPS on SSI is also studied. The results of the study show that the seismic response of the structure increases for majority of the earthquake ground motions due to SSI. The sliding displacement and base shear are underestimated if SSI effects are ignored in the seismic analysis of structures isolated with FPS.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.184-191
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• 2010

This paper proposes the shaking table testing method for replicating the dynamic behavior of soil-structure interaction (SSI) system, without any physical soil model and only using superstructure model. Applying original SSI system to the substructure method produces two substructures; superstructure and soil model corresponding to experimental and numerical substructures, respectively. Interaction force acting on interface between the two substructures is observed from measuring the accelerations of superstructure, and the interface acceleration or velocity, which is the needed motion for replicating the dynamic behavior of original SSI system, is calculated from the numerical substructure reflecting the dynamic soil stiffness of soil model. Superstructure is excited by the shaking table with the motion of interface acceleration or velocity. Analyzing experimental results in time and frequency domains show the applicability the proposed methodologies to the shaking table test considering dynamic soil-structure interaction.

• Ocean Systems Engineering
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• v.9 no.3
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• pp.241-259
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• 2019

This paper presents a fully three-dimensional numerical approach for analyzing deepwater drilling riser-conductor system vortex-induced vibrations (VIV) including nonlinear soil-structure interactions (SSI). The drilling riser-conductor system is modeled as a tensioned beam with linearly distributed tension and is solved by a fully implicit discretization scheme. The fluid field around the riser-conductor system is obtained by Finite-Analytic Navier-Stokes (FANS) code, which numerically solves the unsteady Navier-Stokes equations. The SSI is considered by modeling the lateral soil resistance force according to nonlinear p-y curves. Overset grid method is adopted to mesh the fluid domain. A partitioned fluid-structure interaction (FSI) method is achieved by communication between the fluid solver and riser motion solver. A riser-conductor system VIV simulation without SSI is firstly presented and served as a benchmark case for the subsequent simulations. Two SSI models based on a nonlinear p-y curve are then applied to the VIV simulations. Also, the effects of two key soil properties on the VIV simulations of riser-conductor systems are studied.

• Earthquakes and Structures
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• v.25 no.2
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• pp.79-87
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• 2023

Special moment resisting steel frame structures are now being used commonly in highly seismic regions as seismically reliable structures. However, a very important parameter describing the dynamics of steel structures during earthquake loading, Soil Structure Interaction (SSI), is generally neglected. In this study, the significance of consideration of flexibility of soil in being able to obtain a result closer to reality is asserted. The current paper focuses on calculation of seismic fragility curves special moment resisting steel frame structures under different earthquake loadings for fixed-base and SSI models. The observation of obtained fragility curves lead to the conclusion that the SSI has a considerable effect on component fragility for the steel structures, with its effects decreasing for higher peak ground acceleration. The results show that the structures when considered SSI have a higher probability of exceeding a damage limit state. This observation attests the role of SSI in the accurate study of structural performance.

• Earthquakes and Structures
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• v.17 no.4
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• pp.373-385
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• 2019

In this article, different frequently adopted modeling aspects of linear and nonlinear dynamic soil-structure interaction (SSI) are studied on a pile-supported integral abutment bridge structure using the open-source platform OpenSees (McKenna et al. 2000, Mazzoni et al. 2007, McKenna and Fenves 2008) for a 2D domain. Analyzed approaches are as follows: (i) free field input at the base of fixed base bridge; (ii) SSI input at the base of fixed base bridge; (iii) SSI model with two dimensional quadrilateral soil elements interacting with bridge and incident input motion propagating upwards at model bottom boundary (with and without considering the effect of abutment backfill response); (iv) simplified SSI model by idealizing the interaction between structural and soil elements through nonlinear springs (with and without considering the effect of abutment backfill response). Salient conclusions of this paper include: (i) free-field motions may differ significantly from those computed at the base of the bridge foundations, thus put a significant bias on the inertial component of SSI; (ii) conventional modeling of SSI through series of soil springs and dashpot system seems to stay on the safer side under dynamic conditions when one considers the seismic actions on the structure by considering a fully coupled SSI model; (iii) consideration of abutment-backfill in the SSI model positively affects the general response of the bridge, as a result of large passive resistance that may develop behind the abutments.

• Earthquakes and Structures
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• v.5 no.6
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• pp.679-702
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• 2013

During an earthquake, soils filter and send out the shaking to the building and simultaneously it has the role of bearing the building vibrations and transmitting them back to the ground. In other words, the ground and the building interact with each other. Hence, soil-structure interaction (SSI) is a key parameter that affects the performance of buildings during the earthquakes and is worth to be taken into consideration. Columns are one of the most crucial elements in RC buildings that play an important role in stability of the building and must be able to dissipate energy under seismic loads. Recent earthquakes showed that formation of plastic hinges in columns is still possible as a result of strong ground motion, despite the application of strong column-weak beam concept, as recommended by various design codes. Energy is dissipated through the plastic deformation of specific zones at the end of a member without affecting the rest of the structure. The formation of a plastic hinge in an RC column in regions that experience inelastic actions depends on the column details as well as soil-structure interaction (SSI). In this paper, 854 different scenarios have been analyzed by inelastic time-history analyses to predict the nonlinear behavior of RC columns considering soil-structure interaction (SSI). The effects of axial load, height over depth ratio, main period of soil and structure as well as different characteristics of earthquakes, are evaluated analytically by finite element methods and the results are compared with corresponding experimental data. Findings from this study provide a simple expression to estimate plastic hinge length of RC columns including soil-structure interaction.

• Earthquakes and Structures
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• v.24 no.3
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• pp.155-163
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• 2023

The purpose of this paper is to investigate the coupled effect of SSI and pounding on dynamic responses of unequal height adjacent buildings with insufficiently separation distance subjected to seismic loading. Numerical investigations were conducted to evaluate effect of the pounding coupling SSI on a Reinforced Concrete Frame Structure system constructed on different soil fields. Adjacent buildings with unequal height, including a 9-storey and a 3-storey reinforced concrete structure, were considered in numerical studies. Pounding force response, time-history and root-mean-square (RMS) of displacement and acceleration with different types of soil and separations were presented. The numerical results indicate that insufficient separation could lead to collisions and generate severe pounding force which could result in acceleration and displacement amplifications. SSI has significant influence of the seismic response of the structures, and higher pounding force were induced by floors with stiffer soil. SSI is reasonable neglected for a structure with a dense soil foundation, whereas SSI should be taken into consideration for dynamic analysis, especially for soft soil base.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2005.04a
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• pp.529-537
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• 2005

This paper proposes the shaking table testing method, without any soil specimen only using building model as an experimental part, considering dynamic soil-structure interaction based on the substructure method. The two-layered soil is assumed as a soil model of the entire soil-structure interaction syhstem(SSI) in this paper. Differently from the constant soil stiffness, the frequency-dependent dynamic soil stiffness is approximated for the case of both acceleration and velocity feedback, respectively. The interaction force is observed from measuring the accelerations at superstructure. Using the soil filters corresponding to the approximated dynamic soil stiffness, the shaking table drives the acceleration or velocity, which the needed motion to give the building specimen the SSI effects. Experimental results show the applicability the proposed methodologies to the shaking table test considering dynamic soil-structure interaction.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.04a
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• pp.17-21
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• 1989

SSI2D/3D is a computer program to calculate dynamic stiffness matrix of the foundation for soil-structure-interaction problem in frequency demain. It is written in FORTRAN 77 and applicable to two or three dimensional situations. In this paper the program structure is summarized. Two examples aye shown to demonstrate the possibilities of the Boundary Element Method applied to dynamic problems in infinite domains.

• Earthquakes and Structures
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• v.15 no.3
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• pp.307-317
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• 2018

The current study explores the soil-structure interaction (SSI) effect on the potential seismic damage of mid-rise non-seismically designed reinforced concrete frames retrofitted by Fibre Reinforced Polymer (FRP). An 8-storey reinforced concrete frame poorly-confined due to transverse reinforcement deficiency is selected and then retrofitted by FRP wraps to provide external confinement. The poorly-confined and FRP retrofitted frames with/without SSI are modelled using hysteretic nonlinear elements. Inelastic time history and damage analyses are performed for these frames subjected to different seismic intensities. The results show that the FRP confinement significantly reduces one or two damage levels for the poorly-confined frame. More importantly, the SSI effect is found to increase the potential seismic damage of the retrofitted frame, reducing the effectiveness of FRP retrofitting. This finding, which is contrary to the conventionally beneficial concept of SSI governing for decades in structural and earthquake engineering, is worth taking into account in designing and evaluating retrofitted structures.