Seismic soil-structure interaction (pile foundations)

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Seismic Soil Structure Interaction Effects on RC Bare Frames Resting on Pile-Grid Foundation

Seismic Soil Structure Interaction Effects on RC Bare Frames Resting on Pile-Grid Foundation

To study the seismic soil structure interaction, building frames of 4, 6 and 8 storey was modeled in Ansys software. 3D models of square frame with 3 bays in both X and Y directions are modelled. The storey height and length of each bay of all building frames were chosen as 3m and 5m respectively which is reasonable for a residential building. The thickness of floor slab and roof were taken as 100mm. beam and column dimensions were as given in table 1. The grid dimensions and pile dimensions were calculated according to the axial load they have to carry. Square Pile of 550mm side dimension and 20m length, and grid beam with 1m width and 500mm depth were considered for the analysis (fig 2). The materials considered for design were M30 and Fe 415 steel.
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Seismic soil-structure interaction analysis of deeply embedded smrs and associated challenges,

Seismic soil-structure interaction analysis of deeply embedded smrs and associated challenges,

The nuclear power plant structures, systems, and components (SSCs) important to safety must be designed to withstand the effects of the Safe Shutdown Earthquake ground motion. The design evaluation of these SSCs should take into account seismic soil-structure interaction (SSI) effects. The established SSI analysis methodologies are used primarily for the current generation of large LWRs whose structures are founded on or near the ground surface. Influenced by benefits such as enhanced protection from missiles and aircraft impact and potential reduction in seismic demands, several SMR designs propose to bury or deeply embed major plant structures below grade, which presents new technical challenges with respect to the seismic design and analysis of these structures. Figure 1 illustrates typical embedment depths for large LWRs and SMRs. In this paper, some key technical issues pertaining to the seismic SSI analysis of deeply embedded nuclear structures are addressed and related guidance provided in the recent DSRS for an SMR design is illustrated.
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Seismic soil-structure interaction of a nuclear building: Comparison of two different methods

Seismic soil-structure interaction of a nuclear building: Comparison of two different methods

This paper presents the computation of response spectra for a nuclear building, including seismic soil- structure interaction (SSI), using two different methods. To do so, established computer programs like the SASSI computer code and ABAQUS with Infinite Elements are used. The SASSI computer code is based on the Thin Layer Method developed by Lysmer et al. (1981) as a method for computations in the fre- quency domain. The calculations here are realized with the enhanced efficient SASSI 2010 by Ostadan et al. (2012). Another method, known as the Lysmer damper and also developed by Lysmer and Kuhlemeyer in 1969, is implemented in ABAQUS and called Infinite Elements. These elements contain values for the boundary damping effect. Considering linear elastic material behavior close to the bounda- ry, both methods transmitted and absorbed all normally incoming plane body waves.
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Seismic soil structure interaction

Seismic soil structure interaction

The boundary element method has been used to model the far-field soil which has been shown to be very effective for a surface foundation or an embedded foundation in a linearly elastic h[r]

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Effect of Soil Structure Interaction on Seismic Response of Bridges with Pile Foundations

Effect of Soil Structure Interaction on Seismic Response of Bridges with Pile Foundations

The main aim of the present study is to investigate the effect of soil structure interaction on RC bridges with pile foundation located in soft and medium soil during earthquake. To investigate this a 4 span continues bridge having span length 30m was modelled using finite element software SAP2000. Total 6 bridge configuration was selected with same span length. The set of 11 ground motions recorded on soft and medium soil where selected from PEER data base. Seismic analysis was performed for the 6 model bridges as described in previous sections.
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Effect of Soil-Structure Interaction in Seismic Analysis of Framed Structures using Ansys

Effect of Soil-Structure Interaction in Seismic Analysis of Framed Structures using Ansys

structure interaction. Piled-raft foundations for important high-rise buildings have proved to be a valuable alternative to conventional pile foundations or mat foundations. The concept of using piled raft foundation is that the combined foundation is able to support the applied axial loading with an appropriate factor of safety and that the settlement of the combined foundation at working load is tolerable. Pile raft foundation behavior is evaluated with many researches and the effect of pile length; pile distance, pile arrangement and cap thickness are determined under vertical or horizontal static and dynamic loading. In the present paper the influence of pile length configurations on behavior of multi-storied are evaluated under vertical loading. In practice, the foundation loads from structural analysis are obtained without allowance for soil settlements and the foundation settlements are estimated assuming a perfectly flexible structure. However, the stiffness of the structure can restrain the displacements of the foundations and even tiny differential settlements of the foundations will also alter forces of the structural members. Hence, the interaction among structures, their foundations and the soil medium below the foundations alter the actual behaviour of the structure considerably than what is obtained from the consideration of the structure alone. In this work, analysis of pile soil structure interaction has been studied by finite element software ANSYS 11. The soil structure interact ion has been found to be significantly affecting the performance of structure and it is discussed in this paper.
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Comparative Study on Seismic Analysis of Soil Structure Interaction with Various Soil Properties by Varying Floor Levels

Comparative Study on Seismic Analysis of Soil Structure Interaction with Various Soil Properties by Varying Floor Levels

[13] Gazetas, G. and Mylonakis, G. (1998). “Seismic soil- structure interaction: New evidence and emerging issues”, State of the Art Paper, Geotechnical Earthquake Engineering and Soil Dynamics Gee-Institute ASCE Conference, Seattle, August 3- 6, 1998, Vol. II, pp. 1116-l 174.

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Brief study on Soil-Structure interaction on the Seismic response of base isolated in High- Rise buildings

Brief study on Soil-Structure interaction on the Seismic response of base isolated in High- Rise buildings

During the last quarter of the 20th century, the importance of dynamic soil-structure interaction for several structures founded on soft soils was well recognized. If not accounted for in analysis, the accuracy in assessing structural safety in the face of earthquakes cannot be accounted for adequately. For this reason, seismic soil-structure interaction analysis has become a major topic in earthquake engineering. In Earthquake Engineering when the soil medium is relatively soft, the dynamic interaction between the superstructure, its foundation, and the soil medium may become important. During the shaking of an Earthquake, seismic waves are transmitted through the soil from fault rupture to a structure of interest. The wave motion of the soil excites the structure which in turn modifies the input motion by its movement relative to the ground. These interaction phenomena will be called "so il fo undatio n -sup er structure interactio n" or simp ly "so il structure interaction". Depending upon the material properties of the soil medium, the source of dynamic excitation and the particular type of foundation considered, the response of the structural system can be quite different from the case where the supporting system
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SEISMIC ANALYSIS OF STRUCTURE WITH VERTICAL IRREGULARITIES USING SOIL STRUCTURE INTERACTION

SEISMIC ANALYSIS OF STRUCTURE WITH VERTICAL IRREGULARITIES USING SOIL STRUCTURE INTERACTION

A seismic soil-structure interaction analysis evaluates the collective response of the structure, the foundation and the geologic media underlying and surrounding the foundation, to a specified free-field ground motion. The term free-field refers to motions that are not affected by structural vibrations or the scattering of waves at and around the foundation. SSI effects are absent for the theoretical condition of a rigid foundation supported on rigid soil. Accordingly, SSI accounts for the difference between the actual response of the structure and the response of the theoretical, rigid base condition.
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Seismic Analyses of Base Isolated Nuclear Power Plant Considering Soil-Structure Interaction

Seismic Analyses of Base Isolated Nuclear Power Plant Considering Soil-Structure Interaction

and guidelines in many countries, allows modeling of the inelastic behavior of structural systems. The frequency dependency of soil-structure impedance characteristics is usually considered in a numerical method performed in the frequency domain, whereas the nonlinearity of super structures is normally reflected in the time domain because the inelastic bilinear behavior of materials and structural members strongly depends on the stress or force-displacement path being integrated stepwise. Even the technical background is not seemed strong, a variety of methods considering the frequency-dependent impedance functions in time-history analysis have been proposed. Those procedures having the terminologies of multi-step or hybrid frequency time domain restrain the full use of frequency-dependent impedance capacity to consider inelastic behavior in the super-structure [1, 2, 3]. The equations of motion assumed to linear or equivalent linear system for a certain reference model is usually solved in frequency domain and nonlinear effects in the time domain are evaluated and treated as pseudo-forces. Depending on the degree of nonlinearity of the SSI system, the procedures may require large iteration works sometimes causing divergence. Another method of hybrid-time-frequency domain approach was also developed in 1998 [4]. Soil is represented using frequency-independent springs, dashpots, and possibly masses, and the equation of motion defined in the time domain is solved considering nonlinearity in SSI system. The feature of this method is available to analyze the non-linear SSI system with a rapid convergence
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Soil-Structure   Interaction Analysis Of RBMK-1000 MW Type NPP For Seismic Event

Soil-Structure Interaction Analysis Of RBMK-1000 MW Type NPP For Seismic Event

The floor response spectra generated with the soil supported model can be used for seismic evaluation of the equipment and commodities in the Reactor Building. Seismic[r]

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Advancing seismic probabilistic risk assessment to include nonlinear soil-structure interaction

Advancing seismic probabilistic risk assessment to include nonlinear soil-structure interaction

The earthquake ground motions for response history analyses are based on the seismic hazard at the site of a WUS NPP site. Panel a of Figure 2 presents the seismic hazard curve used for this study in terms of the horizontal peak ground acceleration (PGA) and associated mean annual frequency of exceedance (MAFE). A reference earthquake is defined for the seismic fragility evaluation in the SPRA process. This earthquake is defined as the uniform hazard spectrum (UHS) with a 10,000-year return period (MAFE of 1.0E-04), which corresponds to a horizontal PGA of 0.4g. Panel b of Figure 3 presents the 5% damped UHS corresponding to the horizontal and vertical directions. As a simplification for this study, the shape of the UHS is considered to be invariant within the MAFE range of interest. A suite of thirty sets of ground motion records (three components each) spectrally matched to the reference earthquake UHS are selected for this study. The horizontal ground motion records account for variability of the spectral acceleration in any arbitrary direction about the geometric mean of the two horizontal components.
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Static and Seismic Soil Culvert Interaction

Static and Seismic Soil Culvert Interaction

Settlements of the soil surface and the foundations were measured using LVDT1, LVDT2 and LVDT3 supported by cross bars and extending downward to pads placed either on the sand surface or the foundation surface. In case A (sand only) of all four tests, three LVDTs were used to measure the soil surface settlements, while in cases B, C, and D, LVDT2 was used to measure the settlement of the foundations. Measurements of the LVDTs were recorded during increasing the accelerations of the centrifuge “spin up” from 1g to 60g and then during the shaking. The largest settlement measured during each case occurred through the spinning from 1g to 60g, while the residual settlement measured from the displacement time history recorded during each shaking was generally small. The “spin up” settlement curves from 1g to 60g for the Free and Structure Fields for all tests are presented in Figures 4.1 and 4.2, as a function of the spin up time at model scale. Each relation shows a number of steps, and each step represents 10g increase in the acceleration during the spin up. A large amount of settlement data during shaking was recorded and these show typical shapes and results. Therefore, only the results for the displacement time history of shakings in Test 1, for cases A and C are shown in Figures 4.3 and 4.4 at prototype scale and the reminder are presented in Appendix (B).
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Soil Structure Interaction Of Plan Irregular RC Structures In Seismic Zone-5

Soil Structure Interaction Of Plan Irregular RC Structures In Seismic Zone-5

In the present study to account the effect of support settlement modulus of sub grade reaction(ks) is considered in modeling of buildings of height G+7 RCC structures having material properties M30 grade for concrete and Fe415 for reinforcing steel and structure dimensions height is 26m from the foundation or footing top, three different support conditions are considered having modulus of sub grade reaction value ks =10,000kN/m 3 , ks =20,000kN/m 3 , ks =40,000kN/m 3 and fixed base and foundation depth is considered as 2m below the ground level structures are modeled using STAAD.Pro in seismic zone V as per IS 1893-2002 and the plan irregular shapes considered are rectangular, L and T, It is observed that higher the modulus of sub grade reaction value (ks) lesser will be seismic effect on structures.
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Effect of Seismic Pounding on Adjacent Blocks of Unsymmetrical Buildings Considering Soil-Structure Interaction

Effect of Seismic Pounding on Adjacent Blocks of Unsymmetrical Buildings Considering Soil-Structure Interaction

[2] A.M.Rahman, A.J.Carr and P.J.Moss “seismic pounding of a case of adjacent multiple - story buildings of differing total heights considering soil flexibility effects” Bulletin of the New Zealand society for earthquake engineering. Vol.31,No.1 March 2001 [3] Mr. Magade S.B. and Prof. Patankar J.P. “ Effect of Soil

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Effect of Soil Structure Interaction on Buildings with Stiffness Irregularity under Seismic Load

Effect of Soil Structure Interaction on Buildings with Stiffness Irregularity under Seismic Load

1. Fron chart 1, found that natural period of structure increases for building with stiffness irregularity. Rate is higher for model (2) with soft soil, it is increase 43.93% w.r.t regular building with fixed support condition.

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Deconvolution and Soil Structure Interaction with ProMiss3D  Software Based on Seismic Recordings on Hualien Array

Deconvolution and Soil Structure Interaction with ProMiss3D Software Based on Seismic Recordings on Hualien Array

• the study of the local problems where local balance is checked on each substructure, independently on the others and without taking into account the interface connections. For each subdomain, the equation of the dynamic problem under the effect of seismic incidental fields is solved by taking into account external forces and internal forces acting on the considered substructure;

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Soil Structure Interaction Model and Variability of Parameters in Seismic Analysis of Nuclear Island Connected Building

Soil Structure Interaction Model and Variability of Parameters in Seismic Analysis of Nuclear Island Connected Building

In case of the site under consideration, the initial geo-technical investigations indicated a shear wave velocity of rock as low as 800 m/s which, on confirmatory tests, went up to 2600 m/s. Hence, a wide range of soil parameters is considered in the analyses. The best estimate of low strain shear modulus of the founding medium is 47500 MPa. This is the base value for the analyses (1.0K). In absence of sufficient soil data, the coefficient of variation is taken as 1.0. Hence, a range analysis is performed with shear modulus values of 23750 MPa (0.5K) and 95000 MPa (2.0K). Also, a lower end value of 0.15K is considered for academic purpose to study the variation of results at lower K values.
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Seismic Ground Motion Incoherency Effects on Soil-Structure  Interaction Response of NPP Building Structures

Seismic Ground Motion Incoherency Effects on Soil-Structure Interaction Response of NPP Building Structures

The paper illustrates the effects of ground motion incoherency on seismic SSI responses of a typical axisymmetric nuclear reactor building and two industrial buildings with significant mass eccentricities. To incorporate the motion incoherency effects on SSI response we used both stochastic and deterministic approaches (Ghiocel, 2005, 2006, Ostadan, 2005, 2006, Ostadan and Ghiocel, 2007). In this study two the plane-wave coherency models are used: i) the Luco-Wong coherency model (Luco and Wong, 1986) and, ii) the Abrahamson incoherency model (Abrahamson, 2005). The motion incoherency approaches are comparatively applied for coherent and incoherent seismic input motions to illustrate the effects of motion incoherency on SSI response. The SSI coupling responses of structures are primarily examined to illustrate the additional rocking and torsional motion effects due to the motion incoherency. The SSI results in terms of transfer functions, acceleration response spectra and structural forces are obtained to study the motion incoherency effects. The study shows that incoherency effects are significant in the high-frequency ranges and much less significant for the low frequency responses. SEISMIC MOTION INCOHERENCY MODELING
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Evaluation of Seismic Behavior of Steel Moment Resisting Frames Considering Nonlinear Soil-structure Interaction

Evaluation of Seismic Behavior of Steel Moment Resisting Frames Considering Nonlinear Soil-structure Interaction

SSI are overestimated and at the upper stories have no meaningful different with the responses obtained from the situation with considering SSI. Also, it is observed that the effects of considering the SSI in low-rise structures on stiff and soft soil, are negligible at all stories and it is not necessary to consider (as much as 10~15% in 3 and 6-storey structures). The reduction in maximum variation is about 40% in high-rise structures (18 and 20-storey). The results indicate that about 33% increase in fundamental period in high-rise structures constructed on soft soil in comparison with fixed-base conditions. These case studies confirm that the SSI effects should be taken into account and it is important to consider during structural analysis and design especially in high-rise structures.
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