Dynamic Soil-structure Interaction Research Articles

Scaled Boundary Perfectly Matched Layer (SBPML): A novel 3D time-domain artificial boundary method for wave problem in general-shaped and heterogeneous infinite domain

Artificial boundary method is widely used in the numerical modeling of unbounded wave problem. However, the accurate modeling of truncated infinite domain with general geometry and heterogeneous materials is still a challenging task, especially for direct time-domain analysis in three dimensions (3D). In this paper, a novel 3D time-domain artificial boundary method, called Scaled Boundary Perfectly Matched Layer (SBPML), is proposed. This method is a generalization of the Perfectly Matched Layer (PML) based on a scaled boundary coordinates transformation inspired by the Scaled Boundary Finite Element Method (SBFEM), which is capable of using artificial boundary of general geometry (not necessarily convex) and considering plane physical surfaces and interfaces extending to infinity in the truncated infinite domain. Local scaled boundary coordinates are firstly introduced on the element-level into the truncated infinite domain to describe general geometry properties of the infinite domain. Then, a complex stretching function from PML is applied to radial direction of the local scaled boundary coordinates to map the physical space onto the complex space, resulting in a SBPML domain. The spatial discretization of the SBPML domain produces semi-discrete mixed displacement–stress​ unsplit-field formulations of third orders in time. The order of the obtained formulation can be reduced by one, enabling a seamless coupling with the standard displacement-based finite element formulation of the interior domain. The coupled system can be solved by an explicit time integration algorithm efficiently. The validation of the SBPML is demonstrated through several benchmark tests, including wave problems in unbounded domains with general geometries and heterogeneous material properties. Furthermore, the application of the SBPML in dynamic soil–structure interaction (SSI) is demonstrated using two engineering problems, including an impact analysis of soft rock-nuclear island system and a vibration analysis of soil-lined tunnel system.

Boundary element model for the analysis of the dynamic response of the Soria arch dam and experimental validation from ambient vibration tests

This paper presents a 3D boundary element time–harmonic model for the analysis of the dynamic behavior, under low-level vibrations, of the Soria arch dam (Gran Canaria, Spain). The model takes into account dynamic Soil–Structure Interaction (DSSI), Fluid–Structure Interaction (FSI) and the actual geometry of dam wall and reservoir. The rock and the dam wall are considered as viscoelastic regions, and the water in the reservoir is modeled as an inviscid fluid. The influence of DSSI, FSI, height of the water in the reservoir, accuracy of the geometric modeling of the canyon, and type of transmitting boundary conditions at the truncated end of the reservoir, are evaluated. DSSI and FSI have a significant influence on the dynamic response of the dam, and the accurate representation of the geometry of the canyon is relevant for the correct estimation of the modal shapes. Ambient vibrations tests were also performed, from which the first and third modes could be clearly identified. The comparison between the experimental and numerical natural frequencies and mode shapes suggests that the proposed complete numerical model is able to capture the dynamic response and can be used for the structural health monitoring of the wall of this dam.

Dynamic Soil Structure Interaction of a High-Rise Building Resting over a Finned Pile Mat

High-rise building safety is generally supported by pile-mat systems. They must be sturdy enough to withstand potential lateral loads brought on by earthquakes, wind, dredging, and machine vibrations, in addition to increased axial loads. An innovative piled-mat foundation system is required to deal with these impacts because standard pile foundation systems only have lateral capacities that are 10% of their axial capacities. This study aims to reduce the damage caused by seismic impacts on high-rise buildings using shear walls supported by piled mats, thereby minimizing vibrations within the structure. Compared with conventional pile systems, the finned-pile foundation is a proven method that can withstand a 65% to 80% higher lateral load; hence, a series of SSI analyses were performed on a 25-story high-rise building, with the shear wall resting on a finned-pile mat (FP-Mat), under a far-field earthquake excitation, using ABAQUS software. The seismic responses were studied by performing a time–history analysis on the FP-Mat, with varying fin-lengths (Lf) of 0.2Lp, 0.4Lp, 0.6Lp, and 0.8Lp, which was compared with an analysis of a conventional piled-mat (RP-Mat). The seismic responses for RP-Mat and FP-Mats were studied with peak-acceleration, maximum horizontal displacement, and inter-story drifts acting as the damage parameters. The provision of FP-Mats significantly reduced the vibrations and seismic effects on the building, and as the fin-length increased, the vibrations and seismic effects reduced further. The drifting bound was also reduced as the fin-length increased. The optimum fin-length for FP-Mats is suggested to be 0.6Lp in terms of seismic performance and construction efficiency. This study helps one understand the seismic behaviors of high-rise buildings resting on finned pile mats.

Surrogate model based on ANN for the evaluation of the fundamental frequency of offshore wind turbines supported on jackets

The design of the support structure of offshore wind turbines (OWT) requires the dynamic characterization of the complete structural system, including the soil-foundation subsystem. To minimize resonance phenomena, the structural natural frequencies should be sufficiently apart from those that characterize the different loads. The obtention of natural frequencies can be a computationally expensive procedure, more so if dynamic soil-structure interaction (SSI) phenomena are included. In order to reduce the computational cost, a surrogate model based on Artificial Neural Networks (ANN) is proposed to estimate the fundamental frequency of the assembly formed by the wind turbine, the jacket support structure and the pile foundation. The training dataset is obtained by a finite element substructuring approach in which the dynamic SSI is incorporated through impedance functions obtained from a continuous model. The ability of the proposed ANN-based surrogate model to reproduce the influence that the main variables of the problem have on the fundamental frequency in a sufficiently precise way is shown by comparing its predictions and the results of the finite elements model for new configurations. The high accuracy and significant computational cost reduction justify the use of the surrogate model in applications where a large number of evaluations is required.

Parametric Analysis on the Effect of Dynamic Interaction between Nonlinear Soil and Reinforced Concrete Frame

The effect of dynamic soil–structure interaction on the seismic demand of a reinforced concrete frame is of great significance to seismic design, retrofit, and damage evaluation. To investigate the degree of influence of the consideration of the soil–structure interaction on the structural seismic response, an efficient numerical model considering the nonlinearities of both a reinforced concrete frame and soil was developed and validated against a shaking table test. Subsequently, detailed parametric analyses on the dynamic soil–structure interaction effect were conducted, where the influences of the length and diameter of the pile, span number and frequency of the structure, soil property, and natural uncertainty of the seismic record were investigated. The research results indicate that the base shear of the pile-supported reinforced concrete frame generally increases with a larger pile length and pile diameter. The influence of the span number and pile diameter on the soil–structure interaction effect is up to 40% in some cases while that of the pile length is within 10% in general. Consideration of the soil–structure interaction can also considerably increase the structural base shear in certain cases and the growth can be greater than 30%. The dynamic soil–structure interaction effect predominantly depends on the structure frequency, spectral characteristic and peak acceleration of the seismic record, and soil shear wave velocity while the influence of the pile diameter and number of spans cannot be neglected in some cases.

Seismic response of shield tunnel structure embedded in soil deposit with liquefiable interlayer

Shield tunnels are widely in used urban areas and could be constructed in fully or partially liquefiable soil deposits and are thus susceptible to damage during earthquake events. In this paper, a two-dimensional saturated soil-structure dynamic interaction model is developed for shield tunnel lining structures. The model accounts for the nonlinear mechanical behaviors of the shield tunnel segments and joints. It also accounts for the soil nonlinear behavior by employing plasticity models (i.e., PM4Sand and PM4silt for sand and plastic silt/clay, respectively). The seismic response of the shield tunnel structure in soil deposit with liquefiable interlayer as well as the interaction mechanism between the liquefiable soil layer and the tunnel are investigated. The obtained results demonstrate that the sand dilatancy and cyclic mobility behaviors under undrained loading conditions govern the seismic site response and that the presence of tunnel structure changes the site acceleration response and degree of soil liquefaction. It is also found that internal forces and deformations of the tunnel segment joint around the foot and shoulder are significantly larger than that in the rest of joint positions. Therefore, particular attention should be paid to potential damage of joint bolts around the foot and shoulder in a liquefiable soil deposit.

Reduced T-shaped soil domain for nonlinear dynamic soil-bridge interaction analysis

The one-directional three-component wave propagation in a T-shaped soil domain (1DT-3C) is a numerical modeling technique, in a finite element scheme, to investigate dynamic soil-structure interaction (SSI) coupled with seismic site effects, under the assumption of vertical propagation of three-component seismic motion along a horizontal multilayered soil. A three-dimensional elasto-plastic model is adopted for soils, characterized using their shear modulus reduction curve.In this research, the 1DT-3C wave propagation modeling technique is proposed as an efficient tool for bridge design to take into account directly the spatial variability of seismic loading. This approach, in the preliminary phase of bridge study and design, allows the reduction of the soil domain and the easier definition of boundary conditions, using geotechnical parameters obtained with only one borehole investigation for each pier. This leads to a gain in modeling and computational time.

Dynamic response of driven end-bearing piles and a pile group in soft clay: an experimental validation study

This paper presents novel measurement data on the dynamic soil–structure interaction of an end-bearing pile foundation. The purpose is to assess the ability to predict the foundation impedances based on the small-strain properties of the soil obtained from site investigations. Measurements were performed in two stages of construction, allowing to assess interaction between the piles through the soil. First, single pile impedances and interaction factors between the piles were experimentally obtained for the four piles when they were free to move at the surface. Second, the impedances of the square pile group were measured after casting a concrete pile cap. The piles were additionally instrumented with accelerometers at depth along the centerline of each pile, allowing to illustrate the global behaviour of the piles within the soil. Numerical predictions based solely on information of the small-strain soil properties obtained from extensive site investigations are compared to the experimental results. The impedances of the individual piles are overestimated compared to the measurements, while the interaction factors show a better agreement. The pile group impedances are better captured than the individual ones, using the same soil model. The pile–soil–pile interaction is clearly manifested in the experimental results by pronounced peaks in the pile group vertical impedance, validating results from previous numerical studies.

Equivalent dynamic stiffnesses and 3D wave propagations of a transversely isotropic elastic ground in rocking and torsional interactions with a harmonically loaded rigid foundation

An advanced theoretical formulation along with a robust numerical evaluation method are employed to study the 3 D wave propagations and equivalent dynamic stiffnesses of a transversely isotropic elastic ground in rocking and torsional interactions with a harmonically loaded rigid foundation. Using appropriate dynamic Green’s functions presented in the literature, the rocking and torsional harmonic oscillations of the foundation are formulated analytically in terms of several Fredholm integral equations of the second kind. Then the dynamic stiffnesses and flexibilities are presented analytically for rocking and torsional oscillations. To validate the analytical results, they are reduced to two simpler cases reported in the literature: the static problem and the case of isotropic materials. The semi-infinite integrals appeared in the solutions are evaluated numerically by utilizing the contour integration and residue theorem along with several commands of the Mathematica software. A complete discussion on the elastic wave propagations due to oscillations of the foundation are presented and a detailed comparison is performed between different waves propagate within the half-space and full-space elastic grounds including the P, SV, SH and the Rayleigh waves. Our results showed that due to rocking oscillation of the foundation, the Rayleigh wave does not propagate in the full-space medium but it propagates in the half-space medium. However due to torsional oscillation, the Rayleigh wave does not propagate neither in the full-space nor in the half-space elastic medium. In addition, due to rocking oscillation, the body waves including P, SV and SH propagate within both half-space and full-space elastic mediums; but due to torsional oscillation, only SH-wave propagates within both full-space and half-space elastic mediums. In some tables, numerical values and mathematical formulas for the dimensionless wave numbers and wave velocities are provided for the P, SV, SH and the Rayleigh waves. The Gaussian quadrature method is implemented for definite integrals appeared in the dynamic stiffnesses. Some graphical figures are provided to represent the dimensionless rocking and torsional dynamic stiffnesses and flexibilities versus the dimensionless frequency for different transversely isotropic materials. The effects of anisotropy of materials and the frequency of excitations on the responses are discussed. The results presented in this paper including the dynamic stiffnesses and wave propagations have direct applications in dynamic soil-structure interaction analyses in civil engineering.

Evaluation of dynamic soil-structure interaction effects in buildings with underground stories using 1 g physical experimentation in a transparent shear laminar box

This article presents a study of the Dynamic Soil-Structure Interaction (DSSI) using physical reduced–scale models of a building under different configurations of above-ground and underground stories. Each model was tested in a laminar shear box with a transparent front side. This characteristic of the device makes it possible to visualize the soil particles during the test and acquire data from the soil-structure interaction in a direct and spatially continuous way. A shaking table, an array of 3 high–speed and high–resolution cameras and a tactile dynamic pressure sensor were used. Ricker wavelets, with a wide range of frequencies and amplitudes, were used to evaluate the transfer functions in the system and the seismic response of model. Kinematic interaction effects were evaluated using the Digital Image Correlation (DIC) technique. It is verified that the experimental system allows a detailed tracking of the dynamic interaction between the building and the surrounding soil. The results show the direct relationship between the frequency content of the input wavelet and the dynamic pressure distribution acting on the underground levels, and the increase of the building’s first vibrating period. In addition, it was found that the distribution and magnitude of the lateral soil thrust is dominated by the superstructure vibration, and not the ground movement. This relationship becomes more important as the slenderness of the building increases, i.e., as the rocking mode of vibration becomes more significant. Additionally, in the case of buildings with basements, our results suggest that the combination of the increased confinement, the interaction of the foundation in terms of motion compatibility and the vibrations transferred from the superstructure to the ground produces an invariable reduction in effective base motion, suggesting that neglecting the effects of DSSI would be a conservative assumption.

Dynamic Soil–Structure Interaction Effects in Buildings Founded on Vertical Reinforcement Elements

Pile foundation is an effective technique to support buildings in the presence of soft soil and seismic areas. More recently, the rigid inclusions system has also been utilized for founding buildings. Both systems increase the bearing capacity of the soil and allow reducing the total and differential settlements in the structure. However, the study of these systems in a complete and accurate way implies the consideration of the soil–structure interaction (SSI). In order to investigate the impact of different pile toe conditions (including the placement on hard soil, an anchorage and floating piles) in the response of mid-rise buildings, numerical models with a 5-storey frame building founded on the inclusions system (soil–inclusion–platform–structure) are analyzed and compared with the pile system (soil–pile–structure). Fully coupled finite difference numerical models were developed using Flac 3D. The influence of the dynamic characteristics of the structure was considered analyzing buildings with different heights (3 storeys to 7 storeys). The linear elastic perfectly plastic model with a Mohr–Coulomb failure criterion is used to represent the behavior of the soil. Values of the maximum lateral displacements, of the inter-storey drifts and of the shear forces distribution in the buildings, as well as the rocking of the foundation, are presented. Concerning the foundations, efforts and displacements are compared for the different systems. The results show that the type of support condition influences the seismic response of the building and the efforts and displacements in the rigid elements, depending on the foundation system. The efforts at the toe level in the rigid elements are highly influenced by the support conditions, but there is only a slight influence from the head connection.

Improved soil–structure interaction model considering time-lag effect

An important aspect of soil– structure interaction analysis is establishing a high-precision conversion relationship between the dynamic impedance in the frequency domain and impulse response function in the time domain. Accordingly, an improved Nakamura model was developed in this study to convert dynamic impedance to an impulse response function. The causes and distribution rules of repeated phase angles were investigated based on the traveling time-lag effect, rendering the improved method more robust. In addition, the impulse response function and interaction force can achieve high fitting accuracy by stripping the singular term from the conventional term. In this study, the time-domain impulse response function and interaction force were derived based on the force–displacement relationship. Further, the accuracy and stability of the improved method were verified using a semi-infinite bar on an elastic foundation. Then, the effects of frequency interval, maximum frequency, and shape of the coefficient matrix on the impulse response function and interaction force were studied by considering the analytical solution of a spherical cavity embedded in full space as an example. Finally, two interaction systems were used to verify the applicability of the improved method in analyzing the soil–structure dynamic interaction.

Seismic response of large offshore wind turbines on monopile foundations including dynamic soil–structure interaction

This paper presents the results of a study on the dynamic and seismic response of the support structures of three reference Offshore Wind Turbines (OWT) of increasing rated power, founded to the seabed through monopile foundations. Thus, the structural behaviour of the NREL 5 MW, IEA Wind 10 MW and IEA Wind 15 MW reference OWTs under seismic input is analysed. To do so, a model based on the aero-hydro-servo-elastic OpenFAST open-software code, modified to include dynamic Soil–Structure Interaction (SSI) and input ground motion, is employed. Dynamic SSI phenomena are incorporated through lumped parameter models fitted to the impedances computed using an advanced boundary elements–finite elements model of the soil–foundation system in which the monopile is discretized as a steel pipe buried in the unbounded seabed. The fore–aft and side-to-side responses of the systems are computed under power production, parked and emergency shutdown operating conditions considering different earthquakes and arrival times. It is found that even low and moderate intensity earthquakes can produce significant increases in the structural demands of large OWTs. There exists a clear tendency for SSI to be beneficial when the size of the OWT increases.

Dynamic analysis of eccentrically loaded rigid strip foundation on layered transversely isotropic poroelastic media

This paper presents an analytical method for analyzing vertical and rocking motions of a rigid strip foundation on layered transversely isotropic poroelastic media. The extended precise integration method is employed to obtain the plain strain dynamic responses of layered poroelastic media due to the reaction force from the rigid strip. Then, the contact stresses for dynamic soil-structure interactions (SSI) are modelled by the Bessel series expansions, and a set of linear equations can be developed from the dual integral equations of mixed boundary value problems. The explicit expressions for the contact stresses are further obtained by solving these linear equations. Finally, the presented method is verified, and numerical examples are provided to demonstrate the effects of stratifications, transverse isotropy and permeability of media on the dynamic responses of eccentrically loaded rigid strip foundation.

Dynamic Analysis and Modeling Movement Transmission of Soil Construction Interaction

This paper defines the dynamic analysis and geometric demonstration of movement transmission and the dynamic soil-structure interaction using two different approaches: the finite component process and the limit component approach (EM). This mathematical process is an influential geometric approach right for dynamic tasks. In this item, we used very advanced and effective computer geometric converter approaches to study multifaceted difficulties. The fractional difference equation leading the motion is outcoming and resolved by EM. The influence of 3 dimensions on the movement transmission imitation (1D and 2D) has a conversed captivating effect, dependent on the different finite components kinds (triangles, rectangles, tall degree components). Geometric modeling of stifling is too discussed (Rayleigh checking). The finite component technique then treats a model of movement transmission owing to the vibration of a foundation. The limit component technique's capacities are remembered, and outcomes found through 2D and 3D mockups are planned. Numerous cases of dynamic soil-structure interaction (building, tunnel) are formerly pickled. The outcomes of these properties are discussed here.

Comparative nonlinear soil-structure interaction analyses using macro-element and soil-block modelling approaches

In dynamic soil-structure interaction problems, involving the coupling of structure, foundation and soil, the use of a nonlinear macro-element modelling approach may result particularly advantageous not only to consider nonlinear effects and thus avoid the introduction of possible bias in seismic risk assessment analyses, especially when ground motion intensity levels are high, but also to greatly reduce the heavy computational effort required by 3D finite element soil-block models. In this work, a footing macro-element that models the soil nonlinear behaviour at near-field, as well as the far-field dynamic impedance and energy dissipation through radiation damping, is verified against results obtained from the analysis with OpenSees of a 3D nonlinear soil-block model, itself verified through cross-checks and cross-modelling efforts with equivalent-linear analyses in STRATA and nonlinear analyses in DEEPSOIL. Considering two soil profiles of different complexity and two records of different intensity, one of which leads to extensive soil nonlinearity, the soil-block is verified first. Then, the macro-element model, available in SeismoStruct, is verified against the soil-block model in terms of structural response of a single-degree-of-freedom (SDOF) system as well as near-field soil-footing behaviour.

Seismic behaviour of high-rise frame-core tube structures considering dynamic soil–structure interaction

As the population grows and land prices rise, high-rise buildings are becoming more and more common and popular in urban cities. The traditional high-rise building design method generally assumes the structure is fixed at the base because the influence of soil–structure interaction is considered to be beneficial to the response of structures under the earthquake excitation. However, recent earthquakes and studies indicated that SSI may exert detrimental effects on commonly used structural systems. In this study, a numerical soil–structure model is established in Abaqus software to explore the impacts of SSI on high-rise frame-core tube structures. The seismic response of frame-core tube structures with various structural heights, height–width ratios, foundation types and soil types is studied. The numerical simulation results including maximum lateral deflections, foundation rocking, inter-storey drifts and base shears of rigid-base and flexible-base buildings are discussed and compared. The results reveal the lateral displacement and inter-storey drifts of the superstructure can be amplified when SSI is taken into account, while the base shears are not necessarily reduced. Increasing the stiffness of the foundation and the subsoil can generally increase the seismic demand of structures. It has been concluded that it is neither safe nor economical to consider only the beneficial effects of SSI or to ignore them in structural design practice.

Numerical simulation of the near-fault spontaneous rupture and its influence on dynamic soil-structure interaction

Based on the sub-model technology and the secondary development of the user subroutine in the finite element software ABAQUS, a numerical simulation method to model the dynamic process of near-fault spontaneous rupture is established and verified. The physical nature of near-fault spontaneous rupture is revealed by the proposed numerical simulation method. In addition, the influence of near-fault pulse-type ground motion on the dynamic soil-structure interaction (DSSI) is investigated, which is compared with that of the far-fault ground motion. The results indicate that the acceleration of near-fault ground motion has rich low-frequency components, and the peak vertical acceleration approximately is 1.5 times greater than peak horizontal acceleration, which usually is 2/3 as seismic codes deal with the far-fault ground motion. Finally, it is observed that the distributions of responses of the superstructure and the soil foundation under near-fault ground motion and far-fault ground motion are similar with each other. The responses under near-fault ground motion can be 254.5% greater than that under far-fault ground motion, which means that the near-fault ground motion is more destructive to the structure.

Effect of Embedded Basement Stories on Seismic Response of Low-Rise Building Frames Considering SSI via Small Shaking Table Tests

The dynamic soil-structure interaction is a combination of phenomena caused by the flexibility of soil foundation in structure response. The structure response may be changed by embedded basement stories. Thus, this study seeks to assess the dynamic response of seven-story concrete frame type buildings without a basement, one basement story, and two basement stories, considering fixed and flexible bases. For this purpose, the experimental tests on the small shaking table were executed with a small scaling coefficient of 1:50. Consequently, three scaled models of steel skeleton structures with variable embedded depths have been constructed with fixed and flexible bases. These models are exposed to three seismic input motions: Northridge (1994), Kobe (1995), and Chi-Chi (1999) at the base of the structure as a fixed base and the bedrock level in the soil structure system as a flexible base. The finite element technique is carried out for scaled and real models. Both the scaled and real numerical models are in good agreement with the obtained experimental observations with reasonable accuracy. It is concluded that the lateral deflections are overestimated by excluding embedded depths of structural elements. In the flexible prototype model, the lateral deflections of the superstructure with embedded depths (3 m, 6 m) decrease compared with no embedded depth, in which the maximum reduction percentages of 7-story with embedded depths 3 m and 6 m at the roof floor level are 21% and 42% compared with no embedded depth, respectively, under Northridge earthquake. Otherwise, ignoring the SSI effects (fixed base case), the lateral displacements are underestimated compared with the flexible base. The maximum amplification percentages at the roof floor level between flexible and fixed bases models with variable embedded depths are 35%, 37%, and 65% under Northridge, Kobe, and Chi-Chi earthquakes, respectively. The amplification and reduction percentages may be high or low, mainly depending on soil condition (fixed, flexible), variable embedded depths, characteristics of seismic motion, travel pass, and source of seismic motion. These items are summarized as the frequency domain of the coupled system compared with the frequency domain of the earthquake motion.

Dynamic soil-structure interaction between retaining walls, retaining soil and retained structures

Dynamic soil-structure interaction between retaining walls, retaining soil and retained structures