Time-domain Soil-structure Interaction Research Articles

A time-domain soil structure interaction analysis for wave scattering in 3D layered half-space

A direct time-domain Soil Structure Interaction (SSI) model is proposed to analyze the scattering problems in 3D horizontal layered half-space. This model uses the scaling surface based Scaled Boundary Finite Element Method (SBFEM) to simulate the infinite domain. Additionally, it employs a combined approach, merging the Domain Reduction Method (DRM) with ray tracking algorithm to calculate the effective nodal forces of seismic input. Compared to the original SBFEM, the scaling surface based SBFEM overcomes the limitation of scaling requirements, and the acceleration unit-impulse response function computed by this method satisfies the radiation damping of 3D horizontal layered half-space. For the seismic input, seismic waves are introduced to the system through effective nodal forces, which are applied exclusively to a single layer of elements adjacent to the truncated boundary in the near field. Importantly, these forces only depend on the free field motion. The accuracy and applicability of the proposed SSI analysis model in solving scattering problems in 3D horizontal layered half-space are demonstrated through various examples.

Nonlinear time-domain soil-structure interaction analysis of a mid-rise building benchmarked against earthquake recordings: A case study of the BRI's annex building

Performing soil-structure interaction (SSI) analysis under strong shaking scenarios using the direct method is becoming more prevalent in engineering practice. However, given the pronounced nonlinearity in soil, structure, and foundation response, the robustness of current methodologies is open to question, and benchmarking these methodologies against instrumented case histories is needed to identify the strengths and weaknesses in the approach. In this study, a three-dimensional (3D) Nonlinear (NL) Soil-Structure Interaction (SSI) analysis methodology in the time-domain code LS-DYNA is benchmarked against the actual recordings for a mid-rise building. The well-instrumented Building Research Institute (BRI) Annex Building (ANX) in Tsukuba City northeast of Tokyo, Japan, which features an adjacent free-field geotechnical downhole array, is used for this case study. A Finite Element (FE) three-dimensional 3D SSI model of the site, including the BRI ANX building, that considers both material and geometric nonlinearities is first developed. Two events are applied to the model: the 2011 Tohoku-Oki earthquake main shock (Mw9.1), referred to as the Great East Japan Earthquake (GEJE), and the 2002 Southern Ibaraki Prefecture earthquake (Mw4.9), selected from the BRI strong motion network due to the relatively wide amplitudes recorded at the site. The former event induced maximum shear strains in the soil of 1.6%, while the latter event induced maximum shear strains of 0.08%. For both horizontal and vertical components of shakings, the predicted response of the structure and adjacent free-field downhole array are compared with the corresponding recordings. The results show that the structural response is significantly affected by the accuracy of the predicted free-field ground surface response, especially at the structural fundamental period as opposed to the site period. In addition, results indicate that the fixed-base and flexible-base structural models’ responses are substantially different, mainly attributed to the SSI effects that cannot be captured in the fixed-base model. Finally, a comprehensive discussion on the minimum amount of data required to adequately capture nonlinear structural response using the proposed SSI methodology is provided in this case study.

2-D soil-structure interaction in time domain by the SBFEM and two non-linear soil models

Effects of soil-structure interaction (SSI) have proven to be of more importance than to be ignored. Quite a few methods of modeling and analysis exist to anticipate the real behavior of the structure when placed on flexible soil rather than on rigid ground surface. Yet, how to model the soil needs to be inspected carefully since probable deformations of soil may be at times far from predicted. In this study a newly formed approach is inspected to suggest possible solutions to shortcomings of conventional ones, compare two non-linear soil models, and implement strengths of newer methods. The soil-structure system is modeled and analyzed once directly with the UCSD soil model and then compared with non-linear sub-structuring method with the UCD model. Analyzes are performed in the time domain for both cases. The soil is supposed to be comprised of sands with various density values. The Loma-Prieta earthquake record (Loma-Prieta, 1989) is used to carry out time domain analyzes and capture structural responses. The interactional forces exerted to the near-field soil, which account for the interaction between these two media as well as the radiation damping of the infinite half-space, have replaced the earthquake motion and the far-field has accordingly been truncated out. The non-linear near-field soil-structure system has then been dynamically analyzed. Force outputs reveal a decrease when elastoplastic SSI is considered; while displacement amplitudes are found to be greater for cases not involving SSI, or involving elastic SSI. Changing the applied constitutive model for the soil as well as sand density from loose to dense manifests changes in responses. As the soil gets denser, the SSI behavior gets closer to that of the elastic case. Contrary to the sub-structuring method which usually, and conventionally, assumes linear elastic behavior for the soil-structure system, direct modeling may predict non-linear responses of the system and effects of the structure′s being placed upon an inelastic environment.

Nonlinear time-domain soil–structure interaction analysis of embedded reactor structures subjected to earthquake loads

A generalized time-domain method for soil–structure interaction analysis is developed, based upon an extension of the work of the domain reduction method of Bielak et al. The methodology is combined with the use of a simple hysteretic soil model based upon the Ramberg–Osgood formulation and applied to a notional Small Modular Reactor. These benchmark results compare well (with some caveats) with those obtained by using the industry-standard frequency-domain code SASSI. The methodology provides a path forward for investigation of other sources of nonlinearity, including those associated with the use of more physically-realistic material models incorporating pore-pressure effects, gap opening/closing, the effect of nonlinear structural elements, and 3D seismic inputs.

Time-domain soil-structure interaction analysis of nuclear facilities

The Nuclear Regulatory Commission (NRC) regulation 10 CFR Part 50 Appendix S requires consideration of soil-structure interaction (SSI) in nuclear power plant (NPP) analysis and design. Soil-structure interaction analysis for NPPs is routinely carried out using guidance provided in the ASCE Standard 4-98 titled “Seismic Analysis of Safety-Related Nuclear Structures and Commentary”. This Standard, which is currently under revision, provides guidance on linear seismic soil-structure-interaction (SSI) analysis of nuclear facilities using deterministic and probabilistic methods. A new appendix has been added to the forthcoming edition of ASCE Standard 4 to provide guidance for time-domain, nonlinear SSI (NLSSI) analysis. Nonlinear SSI analysis will be needed to simulate material nonlinearity in soil and/or structure, static and dynamic soil pressure effects on deeply embedded structures, local soil failure at the foundation-soil interface, nonlinear coupling of soil and pore fluid, uplift or sliding of the foundation, nonlinear effects of gaps between the surrounding soil and the embedded structure and seismic isolation systems, none of which can be addressed explicitly at present.Appendix B of ASCE Standard 4 provides general guidance for NLSSI analysis but will not provide a methodology for performing the analysis. This paper provides a description of an NLSSI methodology developed for application to nuclear facilities, including NPPs. This methodology is described as series of sequential steps to produce reasonable results using any time-domain numerical code. These steps require some numerical capabilities, such as nonlinear soil constitutive models, which are also described in the paper.

Modeling Using Coupled FEM-SBFEM for Three-Dimensional Seismic SSI in Time Domain

AbstractFor soil-structure interaction (SSI) problems, accurate modeling of the unbounded domain is an important issue. This paper deals with the three-dimensional seismic SSI analysis based on the substructure method by coupling the FEM and the scaled boundary FEM (SBFEM) approaches. The entire analysis is performed in the time domain making the proposed approach capable of dealing with nonlinearity of soil. To verify the developed program, the results from the present analysis are compared with those available in the literature. This verification has been performed for both externally applied dynamic load and seismic load. The effect of boundary conditions on the SSI response is evaluated. The numerical study performed indicates that the SBFEM can act as a computationally efficient boundary when compared with the conventional viscous dashpots. Next, application of the FEM-SBFEM for SSI problems is demonstrated. A dam-foundation interaction analysis is carried out, and the effect of the inhomogeneity of ...

Earthquake Response of Asymmetric Structure Considering Soil-Structure Interaction in Time Domain

A study is carried out on lateral-torsional coupling response considering soil-structure interaction in time domain. Acoording to lateral-torsional coupling vibration equations of soil-asymmetric structure system, the direct integral MATLAB program in time domain were made used method. The parametric research on elastic dynamic response of soil-asymmetric interaction system in time domain was done by directed integral program. By comparing the parameter influence rule in time domain with the result in frequency domain, it verified the feasibility of using time history method to do parametric research. This conclusion can supply references to study the laws how the parameters influence the inelastic seismic response.

Parallel Computation of 3-D Soil-Structure Interaction in Time Domain with a Coupled FEM/SBFEM Approach

This paper introduces a parallel algorithm for the scaled boundary finite element method (SBFEM). The application code is designed to run on clusters of computers, and it enables the analysis of large-scale soil-structure-interaction problems, where an unbounded domain has to fulfill the radiation condition for wave propagation to infinity. The main focus of the paper is on the mathematical description and numerical implementation of the SBFEM. In particular, we describe in detail the algorithm to compute the acceleration unit impulse response matrices used in the SBFEM as well as the solvers for the Riccati and Lyapunov equations. Finally, two test cases validate the new code, illustrating the numerical accuracy of the results and the parallel performances.

Coupled BEM–FEM solutions for direct time domain soil–structure interaction analysis

A coupled BEM–FEM methodology is presented for 3D wave propagation and soil–structure interaction analysis in the direct time domain. The employed boundary element method (BEM) uses a new generation of the Stokes fundamental solutions that utilize the B-Spline family of polynomials. A standard finite element methodology for dynamic analysis along with direct integration in time is coupled to the BEM through a staggered solution approach. Each method provides initial conditions to the other at the beginning of each time step. Formulation and computational aspects of the proposed coupling scheme are discussed. A number of numerical examples are presented for the validation and demonstration of the general nature of the proposed methodology.

Time-domain soil-structure interaction analysis in two-dimensional medium based on analytical frequency-dependent infinite elements

A direct method for soil–structure interaction analysis in two-dimensional medium is presented in time domain, which is based on the transformation of the analytical frequency-dependent dynamic stiffness matrix. The present dynamic stiffness matrix for the far-field region is constructed by assembling stiffness matrices of the analytical frequency-dependent dynamic infinite elements, so that the equation of motion can be analytically transformed into the time-domain equation. An efficient procedure is devised to evaluate the dynamic responses in time domain. Verification of the present formulation is carried out by comparing the compliances for a strip foundation on a homogeneous and layered half-spaces with those obtained by other methods. Numerical analyses are also carried out for the transient responses of an elastic block and tunnel in a homogeneous and a layered half-space. The comparisons with those by other approaches indicate that the proposed time-domain method for soil–structure interaction analysis gives good solutions. Copyright © 2000 John Wiley & Sons, Ltd.

Efficient time-domain soil-structure interaction analysis based on the dynamic stiffness of an unbounded soil : Hayashi, Y; Takahashi, I Earthq Engng Struct DynamV21, N9, Sept 1992, P787–796

Efficient time-domain soil-structure interaction analysis based on the dynamic stiffness of an unbounded soil : Hayashi, Y; Takahashi, I Earthq Engng Struct DynamV21, N9, Sept 1992, P787–796