Dynamic Soil-structure Interaction Analysis Research Articles

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.

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.

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.

Physics-Informed Optimization for Dynamic Soil–Structure Interaction Analysis of a Pile Partially Embedded in Nonlayered Soils

This study proposes a novel physics-informed optimization approach to account for nonlayered soil conditions for the dynamic soil–structure interaction analysis that is critical for structural health monitoring involving soil–structure interaction. This approach can estimate soil properties based on a few measurements and then predict the natural frequency of structures, a key element that has been very often utilized for structural health monitoring and evaluation. A case study for frequency-based bridge scour detection has been presented for the demonstration of this approach, where a bridge pile is partially embedded in complex nonlayered soils. With this case study, we show that the nonlinear frequency–scour depth relationship can be accurately estimated using 2–4 measured data points, which is in favor of situations where conducting a field test is difficult or the demand for conducting field measurements needs to be reduced. The impact of errors resulting from measurement uncertainty on the performance of this approach is found to be insignificant. This physics-informed optimization approach thus can help analyze dynamic responses of engineering structures in complex nonlayered soil conditions involving soil–structure interaction.

Effect of offset between beam outside and neutral surfaces on dynamic soil-structure interactions

In finite element analyses of the dynamic soil-structure interaction (SSI), structures are often modelled as beam or shell elements in structural mechanics, while the soil requires discretization using solid elements in solid mechanics. The beam and shell elements are coupled with the solid elements on their outer surfaces, while the mechanical behaviour of the beam and shell elements are usually represented by variables defined at their neutral surfaces. The offset between the beam outer surface and the neutral surface in several dynamic SSI analyses is often ignored, which can cause large errors in the coupling analysis of solid and structural mechanics. This paper investigates the effect of the offset between the beam outer surface and neutral surface on the dynamic SSIs. First, the coupling conditions between the beam and the solid considering the offset between the beam outer surface and the neutral surface are deduced. In this process, the tangential interaction stress on the beam outer surface is transformed into an axial force and a moment acting on the beam neutral surface, and the tangential displacement on the beam outer surface is related to the axial displacement at the beam neutral surface as well as the cross-section rotation angle. Then, the coupling condition is implemented in the finite element analysis by modifying the mass and stiffness matrices of the beam element. The offset effects between beam outer surfaces and neutral surfaces on dynamic SSIs are finally discussed in detail through the seismic responses of a retaining wall, subway station and tunnel.

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.

A simplified model of layered soil for analyzing vertical vibration of loaded foundations

Numerous physical models using frequency-independent elements have been developed to reproduce impedance functions for the purposes of time-domain soil–foundation interaction analysis. Most of the models have been developed to simulate homogeneous soils. However, the physical models developed in past research for layered soils are mostly focused on surface foundations only. Accordingly, this study proposes a representative simplified model to simulate the three-dimensional layered soil for square foundations embedded in a non-uniform layer, overlying a uniform half-space, subjected to vertical forced vibrations. The non-uniform layer has shear-wave velocities linearly varying with depth. Non-dimensional charts are presented to determine the model parameters as per foundation embedment ratios, layer depth ratios, and shear-wave velocity ratios of layered soil. The capability of the proposed model is demonstrated through the analysis of frequency-response curves of the foundation to a constant-force type oscillator in the frequency domain and of the displacement history of the foundation to a non-periodic loading in the time domain. The proposed model is found to give results consistent with those obtained from a dynamic soil-structure interaction analysis program. The proposed model may be of practical value for analysis of dynamically loaded foundations.

Analytical solution of seismic displacement of foundations next to slope by cone model

ABSTRACT An important challenge in dynamic soil–structure interaction analysis is the soil profile modelling. The cone model can model the soil and foundation in SSI problems. The cone model works well in low and intermediate frequency ranges such as machine vibrations and earthquakes. In the present study, the dynamic behaviour of a rigid disk next to slope will be determined by cone model. Cone frustums are used to determine how waves propagate below the foundation. The proposed method is able to determine the dynamic behaviour of a disk in various distances next to slope. The soil is assumed as one layer. The presented model is a new analytical model which is capable to estimate the foundations stiffness next to slope in a simple way. Results of the proposed method are verified with experimental and analytical results of other researchers which is in good agreement.

A systematic modeling approach for layered soil considering horizontal and rotational foundation vibrations

Several simplified models have been developed to simulate unbound soil for dynamic soil-structure interaction analysis in time domain. However, the existing models may have critical limitations for general applications. This study presents an approach to systematically generate lumped-parameter models with frequency-independent coefficients to represent the dynamic stiffness of rigid foundations in layered soil undergoing horizontal and rotational vibration. The components of the proposed model are determined from modularized units using a computational procedure, which simulates the coupling between the horizontal and rotational motion. This study applies the proposed model to simulate a non-uniform layered half-space and a uniform stratum on rigid rock. For surface and embedded foundations, the dynamic responses calculated by the proposed model agree well with theoretical solutions and computer program results. For embedded cylindrical foundations, the proposed model performs better and uses fewer parameters than an existing lumped-parameter model to simulate a soil layer on rock. Thus, the proposed systematic modeling approach shows a higher degree of adaptivity than traditional methods to generate simplified models for the simulation of layered soil considering coupled horizontal and rotational motion.

Microtremor measurements and 3D dynamic soil–structure interaction analysis for a historical masonry arch bridge under the effects of near- and far-fault earthquakes

For rational solutions against seismic excitations of masonry bridges, the capability of 3D soil–structure interaction (SSI) modeling with experimental evidence has been insufficiently researched up to now. This is also valid for the effects of near- and far-fault earthquakes. Hence, the spectral responses measured by microtremors have been compared with the ones of 3D SSI analysis under the effects of near- and far-fault earthquakes for a historical masonry arch bridge in this article. The 3D SSI modeling of bridge and substructure soil was built with elastic finite element model using solid element and viscous boundary. The SSI analysis has been performed by direct approach using time-history analysis. The earthquake motions (near fault, far fault) were selected in accordance with the tectonic setting of the bridge’s region. From the study, it is possible to confirm that microtremors are able to detect spectral responses of the bridge by the presence of SSI influences. By the evidence of amplifications and soil–structure resonance, the microtremor measurements experimentally promise that: (i) the bridge can be adequately identified by SSI analysis compared to fixed base, (ii) the elastic model can satisfactorily provide information about the bridge’s responses (amplitudes, spectral response, stress distribution) under earthquake effect, and (iii) the far-fault motion especially due to SSI modeling is significant for the seismic responses. The study indicates that regarding the SSI influences into seismic computation has become quite efficient for determination of a possibility of various adverse effects (high displacements, critical stresses, resonance). Moreover, diagnosing the historical bridge well as a result of microtremors together with SSI modeling strongly proposes protection of the bridge with an appropriate retrofitting.

Dynamic soil-structure interaction analyses of two important structures affected by liquefaction during the Canterbury earthquake sequence

The 2010–2011 Canterbury earthquake sequence produced significant damage in Christchurch. Much of the observed damage was related to soil liquefaction. The availability of building information, performance observations, survey data, geotechnical data, and ground motions recordings in Christchurch produced several well-documented case histories that provide insights to liquefaction-induced building settlement. Two case histories of important structures built atop fluvial soil deposits with sand and gravel layers are analyzed. One building was the third tallest building in Christchurch before the earthquakes, and the other building is an architectural landmark. Both structures were sited near the Avon River in zones of minor-to-moderate lateral spreading. Nonlinear dynamic soil-structure-interaction effective stress analyses are performed using the program FLAC with the PM4Sand constitutive model calibrated with laboratory tests or established simplified liquefaction procedures. The results show good agreement between observed and calculated responses of the ground and structure for the Canterbury earthquake sequence. Dynamic analysis identified several potential mechanisms contributing to the observed performance. Its use is encouraged to estimate shear-induced liquefaction building settlement.

Effect of raft thickness and soil modulus on frequency and amplitude of building frame

The paper presents the limited study on the evaluation of the response of the dynamic soil structure interaction analysis of a two storeyed building frame resting on raft foundation using finite element method. The components of the building frame such as beams, columns and slabs along with the raft are modeled using 20 noded isoparametric continuum elements. The soil surrounding the foundation is modeled in the simplified manner using discrete independent springs. The interface of soil and raft has been accounted for by incorporating 16 node interface elements in the modeling. Further, the components of the superstructure and substructure are treated to behave in the linear elastic manner whereas the soil media is idealized to behave in the non-linear manner. The effect of raft thickness and soil modulus is evaluated on the dynamic response of the frame. The response is considered in terms of the frequency and amplitude. The result indicates that the dynamic loading and SSI has a considerable effect on the response of the structure.

Nonlinear dynamic soil structure interaction in adjacent basement

This research was conducted to analyze the lateral dynamic pressure distribution on the basement walls and amplification of earthquake motion on the surface using the finite element method Midas GTS-NX. Dynamic soil-structure interaction analysis was carried out by using a sensitivity program to influence soil conditions, earthquake acceleration in bedrock, basement depth, bedrock depth and stiffness of the basement structure with a distance between basements of 15,0 m. From this study, the lateral pressure distribution of the dynamic soil reaches the maximum at the base of the basement with an increase in pressure that is almost linear in soft and nonlinear soil conditions in medium and hard soil conditions. The greatest increase in gradient occurs at a depth of four per five basement walls measured from the surface to the bottom of the basement. The analysis shows that the dynamic lateral pressure distribution has a maximum value at the top end of the basement and tends to shrink to the bottom of the basement.

Dynamic soil-structure interaction analyses considering directionality effects

The paper investigates directionality effects of ground motions in the context of dynamic soil-structure interaction (DSSI) analyses. The problem addressed corresponds to a nonlinear soil deposit, overlaying firm ground, where the input motion was derived from an acceleration time history recorded at a rock outcrop. A simplified procedure is proposed to incorporate directionality effects. The main objective is to identify in advance the incidence angle producing the maximum response of a structure for a given earthquake. Results from the simplified procedure were evaluated by comparison with what is called here the complete rotational approach, where the behaviour of the structure, as a function of the incidence angle of the input motion, is derived through a large number of nonlinear dynamic soil-structure interaction analyses. The obtained results show the importance of considering directionality effects in DSSI analyses. The maximum response of the system was reasonably captured with the simplified approach.

Evaluation of Winkler Model and Pasternak Model for Dynamic Soil-Structure Interaction Analysis of Structures Partially Embedded in Soils

AbstractThis paper reports a comprehensive study including detailed experimental, theoretical, and numerical analyses to evaluate the performance of two predominant soil-structure interaction model...

Optimum lateral extent of soil domain for dynamic SSI analysis of RC framed buildings on pile foundations

This article describes a novel approach for deciding optimal horizontal extent of soil domain to be used for finite element based numerical dynamic soil structure interaction (SSI) studies. SSI model for a 12 storied building frame, supported on pile foundation-soil system, is developed in the finite element based software framework, OpenSEES. Three different structure-foundation configurations are analyzed under different ground motion characteristics. Lateral extent of soil domain, along with the soil properties, were varied exhaustively for a particular structural configuration. Based on the reduction in the variation of acceleration response at different locations in the SSI system (quantified by normalized root mean square error, NRMSE), the optimum lateral extent of the soil domain is prescribed for various structural widths, soil types and peak ground acceleration levels of ground motion. Compared to the past studies, error estimation analysis shows that the relationships prescribed in the present study are credible and more inclusive of the various factors that influence SSI. These relationships can be readily applied for deciding upon the lateral extent of the soil domain for conducting precise SSI analysis with reduced computational time.

Liquefaction-induced settlements of residential buildings subjected to induced earthquakes

The paper evaluates the dynamic performance of existing residential houses affected by gas-extraction-induced earthquakes in an area of low tectonic seismicity where structures have not been designed against earthquake loading. The foundation consists of narrow spread footings (width, B < 0.7 m), while the seismic demand is characterized by low intensity. Nonlinear, effective stress, fully coupled, dynamic soil-structure interaction analyses were performed to develop estimates of liquefaction-induced settlements for buildings on narrow spread footings, founded in a range of soil conditions, with ground motions and structural characteristics that are typically encountered in the study area. The results verify patterns observed in recent studies for slab foundations and shed light on new mechanisms. For the low magnitude earthquakes considered in this study, the total foundation settlements were found to be relatively limited, although simplified liquefaction triggering calculations would sometimes predict low factors of safety against liquefaction. A simplified equation was developed from regression of the numerical analyses results to derive estimates of liquefaction-induced settlements for residential buildings that was adopted in the latest update of the relevant seismic building code.

Ground Improvement Design and Construction for Seattle's Elliott Bay Seawall Replacement and Retrofit

The Elliott Bay Seawall in Seattle, Washington, was constructed in the early 1900s over soft/loose non-engineered and liquefaction susceptible fill, estuary, and beach deposits. The fill includes wood from historic waterfront sawmills and debris from the 1889 Great Seattle Fire. After the 2001 Nisqually earthquake, an evaluation of the seawall condition and seismic vulnerability determined that it had undergone significant deterioration and was susceptible to collapse for a 100-year earthquake. This evaluation led to design and replacement/retrofit of 1,130 meters (3,700 feet) of seawall. The new seawall includes an improved soil mass constructed of a cellular arrangement of jet-grout columns that supports a seawall superstructure and provides all seismic lateral restraint. The improved soil mass seismic performance criteria are based on allowable seawall displacement for three earthquake ground motion levels. Final improved soil mass design utilized non-linear dynamic soil-structure interaction analyses. To meet performance criteria, improved soil mass widths range between 7.9 and 18.3 meters (26 and 60 feet), ground improvement area replacement ranges between 50 and 64 percent, and jet-grout soil-cement unconfined compressive strength ranges between 0.86 and 2.76 MPa (125 and 400 psi), depending on the soil type. Improved soil mass construction issues included equipment selection, limited space, spoils handling, wood debris, and obstructions (e.g., buried utilities, piles, and temporary shoring). Lessons learned included: (1) jet grouting was the best construction method given the utilities and thousands of piles beneath the site, (2) early obstructions identification and contingency plans are critical to maintain production, and (3) an understanding of space requirements for all construction activities is required for safe and productive working conditions.

Dynamic soil-structure interaction analysis in time domain based on a modified version of perfectly matched discrete layers

Abstract Analysis of soil-structure interaction is commonly conducted by dividing the infinite domain of the soil into two domains: interior and exterior domains. The interior domain is bounded in a small region, while the exterior domain is replaced by artificial boundary conditions. The choice of artificial boundary conditions is a critical issue in the analysis of soil-structure interaction problems. Perfectly matched discrete layer (PMDL) has been proved as a good approach for modeling the exterior domain. In this study, a modified version of the PMDLs, i.e. PMDLs with analytical wavelengths (AW-PMDLs), is used in the soil-structure interaction analysis in time domain, which essentially can be regarded as an extension of the analysis in frequency domain, being previously proven to be effective. Numerical verifications are implemented. The results demonstrate that the proposed method performs well in the analysis of soil-structure interaction problems in time domain.

Influence of soil-structure interaction on the dynamic response of continuous and integral bridge subjected to moving loads

ABSTRACT In this paper, the effects of high-speed moving train loads over a non-prismatic continuous and integral bridge are investigated, in which the dynamic soil-structure interaction (SSI) analysis is comprehensively considered. Initially, a complete-pile model and an equivalent spring model of the continuous bridge are analyzed and compared. Two complex cases of track loading for the complete-pile model Case-I (C-I): one train moving on the single track, and Case-II (C-II): two trains moving on both the tracks entering at same instant but in opposite direction), under the CRH3 train loading, are studied. The variations in dynamic responses of the bridge for these cases confirm the influence of soil-structure interaction. C-II represents higher vertical displacement and acceleration bridge response compared to the C-I for both, continuous and integral bridge. It is proposed to analyze a detailed 3D model under critical loading condition for acquiring an accurate vertical dynamic response of bridge structure.