Dynamic Soil-structure Interaction Analysis Research Articles

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.

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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.

Dynamic behaviour of coupled soil-structure systems by means of FEM analysis for the seismic risk mitigation of INGV building in Catania (Italy)

Seismic design of new structures, as well as retrofitting and/or improving of existing ones should be definitely considered a multidisciplinary subject, which depends on many factors, such as: local site effects and the dynamic interaction between the foundation soil and the structure. The accurate investigation on the structure and the surrounding soil is the first fundamental step for a realistic evaluation of the structure seismic performance. The present paper deals with the Dynamic Soil Structure Interaction (DSSI) analysis concerning the INGV (National Institute of Geophysics and Volcanology) building in Catania, by means of a FEM 2D modeling. The building is a prestigious masonry structure situated in an area characterized by a high seismic hazard. Several accelerograms scaled at the same PHA, with reference to the estimated seismicity of Catania, have been adopted. Soil properties were carefully investigated by means of static and dynamic in-situ and laboratory tests. Many investigations were also performed on the structure. Equivalent linear visco-elastic constitutive models have been adopted both for the soil and the structure. For considering soil nonlinearity, degraded shear modula ( G ) and increased soil damping ratios ( D ) have been evaluated for all the involved soil layers, according to two different approach es. Firstly, soil nonlinearity has been modeled basing on the EC8 [2003] suggestions; secondly, it has been modeled choosing the values of G and D according to the effective strain levels obtained for each soil layer and for each different input, by means of an iterative sub-routine . The dynamic response of the system has been analyzed in the time and frequency domains. Results are presented in terms of: acceleration amplification factors, Fourier and response spectra, amplification functions and shear forces per floor. The main goals of the paper are: i) to investigate the acceleration profiles along the soil and the structure considering and not considering the DSSI; ii) to investigate the soil filtering effect in terms of predominant frequency considering and not considering the DSSI; iii) to compare the obtained results with the ones given by a simpler 1D free-field soil analysis; iv) to compare the soil amplification factors and the response spectra obtained by 1D and 2D models with that by the Italian technical code [NTC, 2008]; v) to highlight the influence of DSSI in the seismic response of the structure; vi) to evaluate the influence of different modeling of soil nonlinearity on the dynamic response of the soil and structure.

Application of perfectly matched layer to soil-foundation interaction analysis

Despite of the limitation in modeling infinite space, the finite element method (FEM) is one of the most used tools to numerically study the geotechnical problems regarding the capacity of simulating different geometries, conditions and material behaviors. A kind of absorbing layer named perfectly matched layer (PML) has been applied to modeling the radiation damping using FEM, which makes the dynamic analysis of soil-structure interaction more accurate. The PML is capable of absorbing incident waves under any angle and frequency, ensuring them to pass through the model boundaries without reflection. In this context, a new FEM program has been written and the PML formula has been implemented by rewriting the dynamic equation of motion and deriving new properties for the quadrilateral elements. The analysis of soil-foundation interaction by applying the PML is validated by the evaluation of impedance/compliance functions for different ground conditions. The results obtained from the PML model match the extended mesh results, even though the domain is small enough that other types of absorbing boundaries can reflect waves back to the foundation. The mechanism of the wave propagation in the region shows that the forced vibrations can be fully absorbed and damped by the boundaries surrounded by PMLs which is the role of radiation damping in FEM modeling.

Advanced computation methods for soil-structure interaction analysis of structures resting on soft soils

Adopting the most accurate and realistic modelling technique and computation method for treatment of dynamic soil–structure interaction (SSI) effects in seismic analysis and design of structures resting on soft soil deposits is one of the most discussed and challenging issues in the field of seismic design and requalification of different structures. In this study, a comprehensive critical review has been carried out on available and well-known modelling techniques and computation methods for dynamic SSI analysis. Discussing and comparing the advantages and disadvantages of employing each method, in this study, the most precise and reliable modelling technique as well as computation method have been identified and proposed to be employed in studying dynamic SSI analysis of structures resting on soft soil deposits.

Dynamic soil properties for seismic ground response studies in Northeastern India

Stiffness and damping properties of soil are essential parameters for any dynamic soil structure interaction analysis. Often the required stiffness and damping properties are obtained from the empirical curves. This paper presents the stiffness and damping properties of two naturally occurring sandy soils collected from a river bed in a highly active seismic zone in the Himalayan belt. A series of resonant column tests are performed on the soil specimens with relative densities representative of the field and with varying confining pressures. The test results are compared with the available empirical curves. Furthermore, a ground response analysis study is also carried out for a bridge site in the region using both the empirical curves and experimentally obtained curves. It has been observed that the application of empirical modulus and damping curves in ground response prediction often leads to underestimation of the seismic demands on the structures. The established soil curves can thus be utilized in performing seismic ground response studies for the design of new structures or requalification/reassessment of existing structures in the northeastern part of India.

Influence of Height in Simulation of Soil Structure Interaction Problems with Dampers

Abstract In numerical simulation of soil structure interaction problems the presence of dampers in the frame is an advantage yet a special topic to be considered. This paper presents valuable observation on the dynamic soil structure interaction analysis of multi storey frames and considers the effect of height in simulation of soil structure interaction problems. Comparison of these problems has been done by comparing the obtained results from different set up in the software ANSYS. The results of numerical analysis illustrate that it has to be paid more attention when considering the structures not alone but also considering the effect of soil medium.

The near-field method: a modified equivalent linear method for dynamic soil–structure interaction analysis. Part I: Theory and methodology

This paper presents a new direct modeling approach to analyze 3D dynamic SSI systems including building structures resting on shallow spread foundations. The direct method consists of modeling the superstructure and the underlying soil domain. Using a reduced shear modulus and an increased damping ratio resulted from an equivalent linear free-field analysis is a traditional approach for simulating behavior of the soil medium. However, this method is not accurate enough in the vicinity of foundation, or the near-field domain, where the soil experiences large strains and the behavior is highly nonlinear. This research proposes new modulus degradation and damping augmentation curves for using in the near-field zone in order to obtain more accurate results with the equivalent linear method. The mentioned values are presented as functions of dimensionless parameters controlling nonlinear behavior in the near-field zone. This paper summarizes the semi-analytical methodology of the proposed modified equivalent linear procedure. The numerical implementation and examples are given in a companion paper.

The near-field method: a modified equivalent linear method for dynamic soil–structure interaction analysis. Part II: verification and example application

Usually for modeling of soil in a direct soil–structure interaction (SSI) problem, the equivalent linear soil properties are used. However, this approach is not valid in the vicinity of a foundation, where the soil experiences large strains and a high level of nonlinearity because of structural vibrations. The near-field method was developed and described in a companion paper to overcome this limitation. This method considers the effects of large strains and suggests a shear modulus and a damping ratio further modified in the near-field of a foundation. Validity and performance of this approach are evaluated, application examples are explained and the results of a parametric study about the role of soil and structure parameters in the extent of SSI effects on the nonlinear seismic response of structures are presented in this paper. One real existing and five, ten, fifteen and twenty story moment-resisting frame steel buildings with two different site conditions corresponding to firm and soft soils are considered and the responses obtained from the near-field method are compared with the recorded and rigorous responses. Moreover, various SSI modeling techniques are employed to investigate the accuracy and performance of each approach. The results show that the near-field method is a simple yet accurate enough approach for analysis of direct SSI problems.

Finite Element Analysis of DSSI Effects for a Building of Strategic Importance in Catania (Italy)

Structural response to earthquakes has to be definitely considered a multidisciplinary subject, depending on many factors among which local site effects and dynamic interaction between soil, foundations and structures. The present paper deals with the multidisciplinary Dynamic Soil Structure Interaction (DSSI) analysis concerning the INGV building in Catania (Italy) by means of FEM 2D modelling. The building is a masonry structure situated in an area characterized by a high seismic hazard. The dynamic analysis was performed by adopting seven different accelerograms, scaled at the same PHA with reference to the estimated seismicity of the investigated area. Linear visco-elastic constitutive models were adopted for both the soil and the structure; nevertheless, soil non-linearity is taken into account according to EC8, adopting degraded shear modulus and increased damping ratio. The dynamic response of the system was analysed in the time and frequency domains. The main goals of the paper are: i) to investigate the amplification input effects, considering and not considering the DSSI; ii) to highlight the influence of soil layer variation in the coupled system response; iii) to compare the obtained results with the ones given by simpler 1D free-field soil analyses; iv) to compare the acceleration spectra obtained by 1D and 2D analyses with those provided by Italian technical code, NTC08. The performed analyses show the influence of DSSI in the seismic response of the system in terms of PHA and frequency contents.

Evaluation of numerical procedures to determine seismic response of structures under influence of soil-structure interaction

In this study, the accuracy and reliability of fully nonlinear method against equivalent linear method for dynamic analysis of soil-structure interaction is investigated comparing the predicted results of both numerical procedures with the results of experimental shaking table tests. An enhanced numerical soil-structure model has been developed which treats the behaviour of the soil and the structure with equal rigour. The soil-structural model comprises a 15 storey structural model resting on a soft soil inside a laminar soil container. The structural model was analysed under three different conditions: (i) fixed base model performing conventional time history dynamic analysis, (ii) flexible base model (considering full soil-structure interaction) conducting equivalent linear dynamic analysis, and (iii) flexible base model performing fully nonlinear dynamic analysis. The results of the above mentioned three cases in terms of lateral storey deflections and inter-storey drifts are determined and compared with the experimental results of shaking table tests. Comparing the experimental results with the numerical analysis predictions, it is noted that equivalent linear method of dynamic analysis underestimates the inelastic seismic response of mid-rise moment resisting building frames resting on soft soils in comparison to the fully nonlinear dynamic analysis method. Thus, inelastic design procedure, using equivalent linear method, cannot adequately guarantee the structural safety for mid-rise building frames resting on soft soils. However, results obtained from the fully nonlinear method of analysis fit the experimental results reasonably well. Therefore, this method is recommended to be used by practicing engineers.

Dynamic analysis of soil-structure interaction using the neural networks and the support vector machines

An approach to a soil-structure interaction problem is using data-based methods (DBM's) that benefit from developing mathematical models on the experimental data. A mathematical model for the seismic analysis of soil-pile-structure (SPS) systems is built in the neural networks environment based on the existing experimental data. A network consisting of two hidden layers is proved to be the most efficient among other choices. Three sets of data are utilized for training, testing, and validation of the ANN model to avoid over fitting by cross-validation. The accuracy of the neural networks to predict the seismic behavior is enhanced by the parallel vectorial analysis technique of the support vector machines. It is shown that the model can predict the dynamic characteristics and seismic response of the soil-structure system with good accuracy in much less time compared with the finite element method. This research sets out the practical importance of trying to produce more experimental data and using DBM's in solving the complex problem of dynamic analysis of SPS systems in which due to various unknowns, enough accuracy cannot be gained with conventional analytical approaches.

Modeling of radiation damping and transient transmitting boundary

One of the primary obstacles in formulating an accurate yet inexpensive procedure for dynamic soil–structure interaction analysis is the modeling of the unbounded medium beneath the structure. Various available techniques could be classified into a rigorous approach and an approximate approach. The rigorous boundaries are usually formulated in frequency domain, and are computationally demanding owing to the non-local nature of such boundaries and the computation of the boundary terms. The approximate boundaries are formulated directly in the time domain and these are local in space and time. Among the various transmitting boundaries, the extrapolation algorithm has been reported to yield very good results. While removing the shortcomings associated with this boundary, a new formulation of transient transmitting boundary based on an extrapolation algorithm in two-dimensions, has been proposed in this study. A numerical experiment has been selected for the verification of the proposed model with different boundary types including extended mesh, viscous boundary, and the cone model. It has been found that the response predicted on basis of the proposed model compares very well with that of the extended mesh and the cone boundary.

Fully Nonlinear versus Equivalent Linear Computation Method for Seismic Analysis of Midrise Buildings on Soft Soils

AbstractIn this study, the accuracy of a fully nonlinear method against an equivalent linear method for dynamic analysis of soil-structure interaction is investigated comparing the predicted results of both numerical procedures. Three structural models, including 5-story, 10-story, and 15-story buildings, are simulated in conjunction with two soil types with shear-wave velocities less than 600 m/s. The aforementioned frames were analyzed under three different conditions: (1) fixed-base model performing conventional time history dynamic analysis under the influence of earthquake records, (2) flexible-base model (considering full soil-structure interaction) conducting equivalent linear dynamic analysis of soil-structure interaction under seismic loads, and (3) flexible-base model performing fully nonlinear dynamic analysis of soil-structure interaction under the influence of earthquake records. The results of these three cases in terms of average lateral story deflections and interstory drifts are determine...

Dynamic soil-structure interaction analysis for complex soil profiles using unaligned mesh generation and nonlinear modeling approach

Even if numerous studies were dedicated to propose soil-structure interaction analysis methods, most of these methods introduce several assumptions to circumvent the difficulties encountered in modeling and reduce computational efforts. The complex spatial configuration of the soil-foundation interface or the distribution of the soil medium are often simplified using flat-layered soil profiles and, the nonlinearity of the soil medium is generally dealt through an equivalent linear model. However, real soil profiles are featured by complex shapes, inclusion of discontinuities and nonlinear characteristics of soil. Accordingly, this paper presents a soil-structure interaction analysis method considering the characteristics of the structure, soil-structure interface and complex nonlinear distribution of the soil that could not be accurately modeled in previous methods. The proposed method adopts unaligned mesh generation and nonlinear modeling approach to model complex soil profiles. The validity and applicability of the nonlinear soil-structure interaction analysis method are verified through a numerical example.

Dynamic wave soil structure interaction analysis of a two way asymmetric building system DSSIA-3D

In this paper structural response to dynamic loading, which is expressed in terms of displacements of the structure, is studied. A two-way asymmetrical multistory building model is subjected to bi-directional harmonic and earthquake loadings. The time histories of the vertically and horizontal displacements and rotation of the roof are obtained using the scaled boundary finite-element method. The program Dynamic Soil-Structure Interaction Analysis which takes into account the soil-structure interaction effects is applied to study two-way asymmetrical buildings.These results are compared with those of symmetrical buildings. Key words: Dynamic soil structure interaction, scaled boundary finite-element method, displacements, time varying loading.

Explosion‐induced dynamic soil–structure interaction analysis with the coupled Godunov–variational difference approach

AbstractThe paper presents a coupled 2D Godunov–variational difference approach for soil–structure interaction due to a nearby explosion. Owing to the high‐intensity dynamic loads, complex processes take place, including transient separation of the buried structure from the surrounding soil, large deformations of the buried structure including loss of stability, and so on. The approach takes into account the irreversible bulk compaction of the soil medium and is based on the relationships of the shock and rarefaction waves with finite‐difference equations of the shell motion, using a simple iteration method. The model reduces the contact problem to the self‐similar symmetric Riemann problem.The proposed approach is demonstrated by the solution of a buried explosion in the proximity of a lined tunnel buried in soil. The peak contact pressure envelope along the lining was studied. It was found that for an explosion in the proximity of a relatively rigid shell, the maximum value of this envelope is located at some distance from the lining's axis of symmetry. Copyright © 2008 John Wiley & Sons, Ltd.

EFFECTS OF SIDE AND BASE ELEMENTS OF EMBEDDED SPRED FOUNDATIONS ON DYNAMIC SOIL-STRUCTURE INTERACTION AND CONVENTIONAL ESTIMATION METHODS FOR SOIL SPRINGS BY COMPOSING THE IMPEDANCE OF EACH ELEMENT

In this paper, we research a conventional evaluation method of soil springs in the dynamic soil-structure interaction analysis of buildings with embedment foundations. First of all, the bottom element and the side elements are decomposed from the embedment foundation and the dynamic interaction characteristics that each element possesses are examined. The estimation method developed by WEN and Fukuwa(2006) are applied to this examination. Based on the above results, it is mentioned that the soil spring of the embedment foundation which is composed with the impedance of both side and bottom elements is overestimated. Finally, we discuss impedance evaluation methods in the limit strength method and the sway-rocking model with embedment.

A stepwise damping‐solvent extraction method for large‐scale dynamic soil–structure interaction analysis in time domain

AbstractTime‐domain analysis of dynamic soil–structure interaction based on the substructure method plays an increasing role in practical applications as compared with the frequency‐domain analysis. Efficient and accurate modelling of the unbounded soil or rock medium has been a key issue in such an analysis. This paper presents a subregional stepwise damping‐solvent extraction formulation for solving large‐scale dynamic soil–structure problems in the time domain. Accuracy and efficiency of the formulation are evaluated in detail for a classical problem involving a rigid strip foundation embedded in a half‐space. A practical large‐scale soil–structure interaction problem, which represents a high concrete gravity dam subjected to seismic load, is then analysed using the proposed method. Various responses of the dam, including time histories of the crest displacement and acceleration and contours of the peak principal stresses within the dam body, are presented. Comparisons are also made between these results with those obtained using other models for the unbounded medium. Copyright © 2007 John Wiley & Sons, Ltd.

Dynamic soil–structure interaction analysis of buildings by neural networks

In this study, neural networks (NN), which have been widely applied to engineering problems, have been applied to soil–structure interaction (SSI) problems. In the modelling of the NN, the back propagation algorithm has been used. The training and testing sets have been developed by using finite element (SAP2000) package program outcomes. Various analyses have been performed for different height/width ratios of buildings in terms of different soil properties, local site depths, and different shear wave velocities. These effects to the periods, top stories acceleration and displacement have been presented. It is observed that the modelling and analysis stages are minimized, the solution time is quite fast and the NN has shown a satisfactory performance for the solution of SSI problems. The NN results are compared with SAP2000 outcomes and found to be encouraging.