Soil-structure Interaction Analysis Research Articles

Time-dependent soil–structure interaction analysis using a macro-element foundation model

The delayed settlement of foundations due to soil consolidation, creep or particle breakage can alter the internal load distribution and differential settlements in a superstructure through soil–structure interaction (SSI). The study introduces a novel methodology to simulate time-dependent SSI that overcomes the complexity of incorporating the time-dependent behaviour of foundations into routine SSI analysis. The proposed approach represents the superstructure as a condensed stiffness matrix, and replaces the foundations and underlying soils with macro-element foundation models that encapsulate the foundation–soil interaction into load–displacement relationships derived from constitutive models. To examine the performance of the proposed method, a macro-element model for time-dependent analysis of shallow foundations on sand was integrated with structural analysis to simulate two tests performed in a geotechnical centrifuge on a 3D-printed aluminium framed structure supported by footings on sand. The simulated responses of the superstructure and foundations were found to agree well with those observed in the centrifuge tests. Parametric analyses were conducted to investigate the effect of loading history, load level on the superstructure, and creep tendency of soil on post-construction load redistribution and differential settlements. The findings suggest that creep of foundations on sand facilitates load redistribution in the structure from heavily loaded sections to lightly loaded sections. Moreover, post-construction load redistribution depends on the differential creep between footings and should be considered for structures that are quickly constructed or at high levels of strength mobilisation (low factor of safety). Overall, the study highlights the potential of the proposed methodology in analysing the time-dependent SSI and its applicability in practical SSI analysis.

Soil-structure interaction analysis using subgrade reaction modulus in raft design

This paper presents an analysis of raft foundation behavior and settlement estimation. Soil-structure interaction is incorporated into the studied models through the parameter k (modulus of the subgrade reaction). However, k is limited in applicability due to its lack of intrinsic connection with the soil. The rigidity of the foundation, superstructure, and their projection within the plant, all impact the k parameter, resulting in further constraints. Despite these limitations, integrating k into the analysis can lead to less conservative designs and viable raft foundation solutions that might otherwise be discarded. As a foundational parameter, the modulus of subgrade reaction is evaluated using theoretical expressions, tables, correlations, and empirical studies. This paper aims to present an assessment of the modulus of subgrade reaction and its distribution beneath the raft plate. The evaluation involves theoretical expressions and an indirect method to explore the potential benefits of employing different k values across distinct regions of the plate. The findings reveal a uniform distribution of modulus of subgrade reaction values, leading to the conclusion that incorporating an average of this parameter value in the plate's design analysis can yield satisfactory results. In conclusion, this research contributes to understanding raft foundation behavior in concrete structures by emphasizing the significance of soil-structure interaction through the incorporation of the subgrade reaction parameter k. By addressing the limitations and demonstrating its applicability, this paper encourages a safe, more efficient, and less conservative approach to raft foundation design.

Large‐scale seismic soil–structure interaction analysis via efficient finite element modeling and multi‐GPU parallel explicit algorithm

AbstractAs urban population increases, integrated underground–aboveground complexes are being constructed at growing paces in major cities. The seismic analysis of such complexes is crucial for the safety and functionality in the threat of potential earthquake disasters. However, fine‐grained numerical modeling and analysis of such large and complex structures are still inefficient due to the consideration of the soil–structure interaction (SSI). To address this challenge, an efficient approach for numerical modeling of large‐scale seismic SSI analysis is presented in this paper to overcome the limitations of existing finite element analysis (FEA) software. Moreover, a multi‐graphic processing unit (GPU) parallel explicit algorithm is implemented for the nonlinear dynamic SSI problems to further increase the computational efficiency. A large underground–aboveground complex project in China is used as an example to demonstrate the capability of the integrated method. The accuracy and reliability of the multi‐GPU parallel explicit finite element algorithm for SSI analysis (GFEA‐SSIA) are verified through a comparative analysis of the linear‐elastic and nonlinear dynamic response of the building calculated by GFEA‐SSIA and common FEA software. Finally, the structural response and structural damage of the underground–aboveground complex are analyzed under multidirectional seismic motions, and the damage distributions of the structures are provided.

Time-domain instability mechanism for artificial boundary condition of semi-infinite medium described by discrete rational approximation

The use of discrete rational approximation functions to represent foundation dynamic impedance plays a crucial role in the time-domain analysis of soil-structure interaction regarding artificial boundary. In modeling, the rational approximation functions need to be transformed into time-domain recursive models for incorporation into time-history analysis. However, this method also suffers from uncertainties in parameter identification and instability in time-domain analysis when the time-domain recursive models of soil are coupled with upper structure. The stability issue in artificial boundary coupled time-domain computation has not been effectively addressed. This paper establishes the closed-loop transfer function of the coupled system and analyzes the causes of instability in the coupled system based on gain margin analysis. Different numerical simulations demonstrate that the major cause of artificial boundary system instability is the description errors of discrete rational approximation functions beyond the fitting frequency range.

Machine learning-based soil–structure interaction analysis of laterally loaded piles through physics-informed neural networks

Machine learning-based soil–structure interaction analysis of laterally loaded piles through physics-informed neural networks

Time domain modeling of elastic waves using a stress-based unsplit-field perfectly matched layer with enhanced numerical stability

A stress-based unsplit-field perfectly matched layer (PML) method with enhanced numerical stability is proposed to simulate elastic waves in heterogeneous unbounded domains. The proposed PML method attenuates the waves by forcing the satisfaction of mixed-field equations constructed using a complex coordinate stretching in the frequency domain. Unlike other unsplit-field PMLs, which introduce coordinate stretching before combining the constitutive and compatibility equations, the proposed method first combines the two equations and then stretches the resulting equation. The stretched equation is converted back to the time domain using the inverse Fourier transform to yield transient elastic wave equations in the PML-truncated domain. Semi-discrete equations of motion for displacement and stresses were obtained using standard Lagrange-family finite elements. In a series of numerical examples involving semi-infinite elastic media, the accuracy of the wave solutions calculated using the proposed PML method was evaluated using a displacement L2-norm, a normalized L2-error, and an energy norm. The examples further validated the wave absorption performance of the PML and evaluated the long-term stability of solutions utilizing the Ricker pulse excitation with various central frequencies. The numerical experiments indicate that the solutions obtained using the proposed PML are significantly more stable than those obtained using the existing strain-based unsplit-field PMLs. The proposed method is particularly useful for applications requiring explicit time integration of semi-discrete equations of motion because the mass matrix can be diagonalized. The PML method and its associated solution strategies can be applied to various engineering problems, such as soil-structure interaction analysis, monitoring of structures, and geophysical probing.

Assessment of liquefaction effects on dynamic soil-structure interaction for the 1908 Messina and Reggio Calabria scenario earthquake

Earthquake-induced liquefaction can significantly modify the dynamic response of a soil deposit and interacting structures. In this study, dynamic soil-structure interaction analyses have been performed for a strategic building resting on liquefiable soil. The structure, located in the city of Messina (Sicily, Italy), was built after the strong earthquake of 1908 that caused severe ground shaking and also liquefaction phenomena. Numerical analyses have been conducted with the finite element code PLAXIS3D that adopts the UBC3D-PLM model to simulate the seismic response of liquefiable soils. The advanced UBC3D-PLM model has been calibrated by means of the simulation of cyclic direct simple shear tests (CDSS) using PLAXIS3D software. The seismic behaviour of the soil-structure system on liquefiable soil has been analysed in terms of liquefaction potential, accelerations, response spectra and displacements under three seismograms of the 1908 earthquake. Findings of this study can be of great significance and interest for the prevention and mitigation of seismic liquefaction hazards in areas with high seismic risk.

Site Specific Non-Linear Ground Response Analysis and Soil Structure Interaction Study of Newly Constructed Dharahara Tower

This study investigates the seismic performance of the recently reconstructed Dharahara tower, a historically significant monument in Nepal that has experienced damage in past earthquakes and was completely destroyed in the recent Gorkha earthquake. Ground Response Analysis (GRA) and Soil-Structure Interaction (SSI) investigations are conducted to assess its structural behavior. GRA includes free field and structure-influenced analyses, with subsequent comparative assessment. Additionally, 3D non-linear finite element analysis is employed to derive equivalent spring constants representing soil and foundation characteristics, which are incorporated into the SSI analysis. These computed spring constants are used to model support conditions, allowing for an evaluation of the super-structural response. The study also employs non-linear dynamic analysis to compare structural responses between fix-based and spring-based models. The results indicate that the presence of the structure significantly influences surface wave motion amplification in GRA, resulting in peak ground accelerations (PGAs) that exhibit de-amplification in the free field and amplification in the presence of the structure. Furthermore, the introduction of an equivalent spring system in the soil-structure model changes the system's vibration period and damping characteristics, leading to enhanced dynamic response compared to the fixed-base model.

Dynamic soil-structure interaction analysis for base-isolated nuclear island building based on the method of external source wave motion

Soil-structure interaction (SSI) is crucial to the dynamic response of nuclear power plants (NPPs), and should be properly considered when analysing the seismic isolation performance of base-isolated NPPs. In this study, a three-dimensional numerical simulation program is developed for the time-domain dynamic analysis of base-isolated NPPs considering SSI effects. The seismic input is realised using the method of external source wave motion, and the nonlinear behavior of isolators is fully considered. Using this program, the SSI effects of the base-isolated nuclear island building under different sites are analysed and compared, including the acceleration, displacement, and floor response spectra. The numerical results show that the SSI effects change the spectral characteristics of the actual seismic input. When the shear wave velocity of the site is relatively large, the SSI effects can increase the dynamic response of base-isolated NPPs. Additionally, the isolation performance of the base-isolated NPPs is weakened when SSI effects are considered, and with a decrease in the shear wave velocity of the site, the isolation capacity is further reduced. The influence of the SSI effects should be fully considered in the base isolation design of NPPs.

Soil–Structure Interaction Analysis Using the Finite Element Method in Thin-Walled Steel Pipes Buried under Haul Roads

This paper addresses the challenges associated with steel pipes used for transporting liquid fluids within buried sections of mining facilities, specifically in areas with heavy mining vehicles. While existing design standards, such as AW-WA M11, and manufacturer recommendations largely consider loads from vehicles like the AASHTO HS20 or Cooper E-80, both weighing below 35 tons, these guidelines inadequately represent the actual loads experienced on certain mining roads, notably those accommodating heavy vehicles, like haul roads. The research presented here focuses on the interaction between soil and buried steel pipes under the substantial loads exerted by mining vehicles with a maximum gross load of up to 612 tons, inclusive of hauled material weight. Utilizing a parametric study with the finite element method, the paper identifies critical variables influencing efforts and deflections calculations in these facilities. The analysis of 108 models, varying parameters related to trench pipe installation conditions, offers insights that empower designers to refine soil trench parameters in mining facilities, mitigating pipe failures and optimizing installation costs. Ultimately, the key influential variables affecting pipe deflection and stress are identified as the trench backfill height and the elasticity modulus of the trench lateral fill.

A new equivalent acceleration-based non-uniform response spectrum method for efficient seismic SSI analysis

A complex multiple-support response spectrum (CMSRS) method with a concise and universal expression is required to estimate the seismic responses of soil–structure interaction (SSI) systems under non-uniform seismic excitations to replace existing complex methods. This paper introduces and defines a new concept called equivalent acceleration of boundary load (EABL) that converts widely used equivalent loads into equivalent accelerations, and further develops an efficient CMSRS-EABL method for the seismic analysis of the SSI system. First, EABL offers three main benefits: it simplifies the expressions without sacrificing precision, extends the applicable scope of viscous-spring artificial boundary (VSAB) to all stress-type artificial boundaries, and presents dynamic equations in a familiar form. Subsequently, the CMSRS–EABL formula was successfully deduced based on the equivalent simplified dynamic equations. This formula significantly simplifies the traditional method by reducing the effective modal participation factors, mean-square-roots, and cross-correlation coefficients by 4, 5 and 15 items, respectively. Finally, a rectangular construction surrounded by a VSAB–soil combination was used as an example to illustrate the convenience of the developed CMSRS–EABL method and verify its precision. The results indicate that the proposed method is characterized by greater simplicity and ingenuity, and it is capable of high precision similar to that of the conventional methods. We believe this method will be of significant benefit in evaluating the anti-seismic performance of deeply buried and long-standing structures.

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.

Soil-structure interaction of nuclear power plant

Nuclear power plants are special facilities with large foundation designs, located in areas with good geology. However, in areas where seismic loads need to be considered, analyzing the soilstructure interaction of nuclear power plants is essential. Nonlinear analyses of soil-structure interaction can be performed in the time domain or frequency domain. Time domain analysis has the advantage of easily incorporating nonlinear material models or geometric nonlinearity. However, this method is limited by the boundary conditions of the geological region near the structure, as current analysis methods assume vertically propagating seismic waves towards the structure. This assumption is made to limit the errors that finite element methods can introduce at the boundaries. This paper presents a new computational method that combines finite element method and boundary element method, in which the propagation of seismic waves towards the structure can be considered at a predetermined angle. The paper analyzes the impact of wave propagation on the response spectrum of the Kashiwazaki-Kariwa Nuclear Power Plant Unit 7. The results of the analysis show that the new computational method can consider the influence of the angle of incoming wave on the soil-structure interaction analysis.

Seismic Response of RC Frame Buildings: Theoretical Formulation and Modeling with Soil-Structure Interaction Analysis

"Seismic Response of RC Frame Buildings: Theoretical Formulation and Modeling with Soil- Structure Interaction Analysis," offers a comprehensive exploration of the seismic response of reinforced concrete (RC) framed structures, with particular emphasis on soil flexibility. Through a meticulous response spectrum analysis, the study delves into the influence of soil flexibility on buildings of varying heights, ranging from five to nine storeys, considering both fixed and flexible support conditions across diverse soil types. The research draws the following significant conclusions: Significance of Soil-Structure Interaction (SSI): Incorporating soil-structure interaction (SSI) into the analysis leads to a noteworthy extension of the natural time period of the structure. This parameter stands as a linchpin in grasping the lateral response of framed structures, underlining its pivotal role in the precision of seismic design calculations. Soil Flexibility and Amplified Base Shear: Enhanced soil flexibility is found to correlate with a proportional increase in base shear. This phenomenon is most pronounced in soft soil conditions, where base shear experiences substantial escalation, particularly in taller buildings. Roof Displacement as a Performance Indicator: Roof displacement, a crucial indicator of structural performance, exhibits an upward trajectory owing to the cumulative effects of SSI. Notably, soft soils manifest higher roof displacements, with these variations becoming more pronounced as the building's height increases. The insights garnered from this analysis underscore the profound influence of SSI on a building's seismic response. Furthermore, the study highlights that advancements in finite element methods (FEM) and computer technology have significantly facilitated the integration of SSI into structural analysis. Therefore, it is imperative to harness these advancements fully to enhance our comprehension of structural behavior and to promote the adoption of secure construction practices in seismic-prone regions.

Time-domain deconvolution procedure for elastoplastic materials: Application to the Treasure Island site during the 1989 Loma Prieta earthquake

When dynamic soil-structure interaction (DSSI) analyses are performed, e.g. using the finite element (FE) method, the input signal is required at the base of the model. Nevertheless, acceleration records are usually available at the surface and, therefore, the desired motion must be deconvolved to the base. The latter is usually performed through the solution of one-dimensional propagation of shear waves in an elastic medium, in the frequency domain. Herein, nonlinear behavior is generally incorporated through the equivalent-linear method, by iteratively reducing the stiffness and increasing the critical damping ratio as a function of the maximum strains attained in each iteration. However, if complex material models are adopted to characterize the soil, the input motion derived with the equivalent linear method will not be compatible due to the simplified approach used to represent the nonlinear behavior. In this article, the use of a procedure to perform a time-domain deconvolution in non-linear elastoplastic materials is demonstrated. The goal is to generate input accelerograms at the base of a FE model to perform DSSI analyses. The procedure is based on the iterative modification of the motion at the base according to the relative differences between the propagated and target surface spectra. To illustrate the use of the methodology, it was applied to a FE model of the Treasure Island site (San Francisco, US), to derive the required motion at the base from a record of the Loma Prieta earthquake.•This article provides a useful guideline to optimize the use of the deconvolution procedure to derive input motions for dynamic FE analyses considering nonlinear elastoplastic materials.

The state of practice in soil-structure interaction modelling in New Zealand

The current state of practice in soil-structure interaction (SSI) modelling in New Zealand was investigated through an industry-wide questionnaire. This used a mixed methods, sequential explanatory research design involving the collection of quantitative and qualitative questionnaire data, as well as follow-up focus groups. Several statistically significant relationships were observed for SSI modelling approaches between different engineering fields, company sizes, and years of experience. The key findings from this study suggest that there is no consensus on the best SSI analysis methods, modelling strategies, or guidelines to be used. Overall, fixed base analysis remains the most popular method across all company sizes and number of years of industry experience. Engineers from large companies reported higher consideration for SSI modelling and use of performance-based design for design projects, which perhaps reflects the scale and complexity of projects carried out in those companies. However when SSI is considered, analyses are typically limited to nonlinear vertical springs under the foundation as part of a dynamic analysis. Use of SSI for buildings is typically limited to seismic assessments and complex or otherwise high importance structures. However, bridge engineers routinely used pushover analyses with linear and nonlinear springs and dynamic analyses with nonlinear springs, in contrast with the rest of the industry. There is further room to improve on the quality of communication and interaction between structural and geotechnical engineers. A lack of specific guidance on when SSI should be considered was reported, alongside broader training issues to ensure that structural and geotechnical engineers fundamentally understand the requirements and input/output needs of each role.

Implementation of a coupled FEM-SBFEM for soil-structure interaction analysis of large-scale 3D base-isolated nuclear structures

Accurately simulating the radiation damping of an infinite domain is a crucial issue for reasonably and effectively evaluating the isolation effect of three-dimensional (3D) base-isolated nuclear structures considering soil-structure interaction (SSI). The scaled boundary finite element method (SBFEM) has excellent advantages that enable it to precisely fulfil the radiation conditions. In this study, the finite element method (FEM) and SBFEM were combined to develop a coupled FEM-SBFEM technology. The structure and finite domain were discretized using FEM, and the infinite soil was realised using SBFEM. A complete and efficient calculation procedure for SSI analysis was developed based on the coupled FEM-SBFEM, improving the calculation efficiency through parallel programming. The accuracy of the developed procedure was verified using a numerical example. Furthermore, the dynamic response of a large-scale refined 3D base-isolated reactor building considering SSI was analysed using the proposed method. The results demonstrate that the 3D base isolation technology has excellent isolation performance. Additionally, we compared the response results of the proposed coupled FEM-SBFEM and direct method. The proposed procedure has broad engineering applicability and can be used for seismic SSI analysis of large-scale nuclear structures while maintaining high computational accuracy and stability.

An efficient numerical algorithm for solving the dynamic impedance function of arbitrary-shaped foundations in layered soil

In soil–structure interaction analysis, the dynamic impedance solution can be obtained using Green's function based on frequency dependence. To satisfy the mixed boundary conditions of the ground–ground interface, the interface should be frequently divided into several evenly spaced sub-elements instead of finite elements. Generally, the accuracy increases and the computational efficiency decreases with an increase in the number of sub-elements. To obtain reliable solutions and improve efficiency, a numerical algorithm for solving the dynamic impedance function of arbitrary-shaped foundations in layered soil was investigated. Based on the wave propagation equation of a horizontally layered half space, the relationship between the number and radius of sub-disk elements and their dynamic impedance matrix was derived using the high-precision method of solving Green's function for the individual sub-disk elements. The derived equation provides an efficient and accurate method to calculate the dynamic impedance of rigid layered foundations and was verified based on numerical examples. The numerical examples revealed that the proposed method reproduced the results in the literature. With the given accuracy, this method reduces the calculation time and improves the calculation efficiency. This proposed high-precision method for solving the foundation dynamic response is well suited to practical engineering applications.

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.

The influence of boundary conditions on nonlinear time domain site response analysis using LS-DYNA

The dynamic response of nuclear power plants and other critical infrastructure under seismic conditions is a major issue, and the earthquake-resistant capacity design of such facilities and their interior equipment should be based on prediction of dynamic response. Therefore, field geological investigations and corresponding site response analyses facilitate the evaluation of seismic site effects for the entire construction process, including site selection and detailed design. During site response analysis, soil parameters are usually obtained from laboratory tests using specimens retrieved from boreholes or from empirical equations. Conventional site response analysis software assumes horizontal layering in a 1D soil model, though the actual conditions of underground stratification are far more complicated. Some research efforts have undertaken 3D site response and soil-structure interaction analysis using LS-DYNA; however, the influence of different boundary conditions in these studies has been rarely discussed. The research reported on in this paper utilized LS-DYNA to perform nonlinear time-domain site response analysis and evaluated the difference between 1D and 3D model results. The results of both 1D and 3D site response analyses conducted using LS-DYNA were comparable to those of traditional approaches using a constrained boundary. The 3D models that adopt a non-reflective boundary condition can be affected by energy attenuation near the model boundary, causing a significant difference in the results. We suggest that the constructed model should have an area of at least 600 m × 600 m (plan view) to ensure accuracy in a 200 m × 200 m area in the center of the 3D simulation model using non-reflecting boundary conditions. Furthermore, four soil profile from real sites have been verified that the suggestion is also applicable in multilayered scenario.