Dynamic Soil-structure Interaction Research Articles

Seismic response of clay-pile-raft-superstructure systems subjected to far-field ground motions

A series of three-dimensional (3D) finite element analyses incorporated with a hyperbolic-hysteretic soil model were performed to investigate the seismic response of pile-raft-superstructure systems constructed on soft clay stratum, focusing on the seismic pile bending moment and superstructural responses. The seismic pile bending moment results suggested that using a lumped mass to represent the superstructure, which has been widely used in many other studies, could only perform well for a relatively low-rise superstructure; on the other hand, the seismic response of superstructure was found to be significantly affected by the soil-structure interaction, and both the detrimental and beneficial effects of dynamic soil-structure interaction were observed. Hence, coupled soil-foundation-superstructure analyses were primarily performed in this study. The influences of peak base acceleration, pile flexural rigidity and the configuration of superstructure on both the pile bending moment and superstructural responses were studied. Furthermore, some correlations were derived to relate the maximum pile bending moment to the influencing factors, which can be used as useful tools for obtaining preliminary and first-order estimates of the maximum pile bending moment for pile-raft-superstructure systems constructed on soft clay deposits.

The effect of foundation flexibility variation on system response of dynamic soil–structure interaction: an analytical solution

A closed-form analytical solution is presented for the dynamic response of a SDOF oscillator, supported by a flexible composite foundation embedded in an elastic half-space, and excited by plane SH waves. The solution is obtained by the wave function expansion method. The solution is verified for the two limiting cases of a rigid–flexible composite foundation and a homogeneous flexible foundation by comparison with published results. The model is used to investigate the effect of the foundation flexibility variation on the system response. The results show that the effect is significant for both foundation response and structural relative response. For a system with larger foundation flexibility variation, the peak of the foundation effective input motion is smaller, while the amplitude of structural relative response less changes. When foundation flexibility variation decreases, system frequency will shift to lower frequency, and the shift value is also highly dependent on the foundation flexibility variation.

Multiple tuned mass damper based vibration mitigation of offshore wind turbine considering soil–structure interaction

The dynamics of jacket supported offshore wind turbine (OWT) in earthquake environment is one of the progressing focuses in the renewable energy field. Soil–structure interaction (SSI) is a fundamental principle to analyze stability and safety of the structure. This study focuses on the performance of the multiple tuned mass damper (MTMD) in minimizing the dynamic responses of the structures objected to seismic loads combined with static wind and wave loads. Response surface methodology (RSM) has been applied to design the MTMD parameters. The analyses have been performed under two different boundary conditions: fixed base (without SSI) and flexible base (with SSI). Two vibration modes of the structure have been suppressed by multi-mode vibration control principle in both cases. The effectiveness of the MTMD in reducing the dynamic response of the structure is presented. The dynamic SSI plays an important role in the seismic behavior of the jacket supported OWT, especially resting on the soft soil deposit. Finally, it shows that excluding the SSI effect could be the reason of overestimating the MTMD performance.

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.

Rocking of Non-symmetric Rigid Blocks in Buildings Considering Effects Associated with Dynamic Soil-Structure Interaction

ABSTRACTA dynamic model for the estimation of the rocking and/or overturning response of a free-standing non-symmetric rigid block considering rotational and horizontal excitation is proposed. The block is situated at different levels of a building with flexible base subjected to earthquakes. Base flexibility introduces the rotational component of the excitation due to dynamic soil-structure interaction (DSSI). The model is used to assess the influence of the dynamic soil-structure interaction on the behavior of the block. An illustrative example of the proposed model for non-symmetric rigid blocks in 5-, 10-, and 15-story buildings located in soft soils considering earthquakes from different seismic sources is presented. Results show that it is important to consider kinematic effects as well as inertial effects of DSSI in the dynamic response of contents. The influence of base flexibility depends on the change of spectral intensities associated to the increase of the building structural period and is larger for higher building levels.

Numerical Modeling of Soil-Pile-Interaction with Near and Far Field Earthquake's Effects

This paper studies Near and Far Field effects of the response of a column-pile to earthquakes considering Dynamic-Soil-Structure-Interaction (DSSI) effects in soft clay (Vs<180 m/s ) and stiff clay (180<Vs<375 m/s). Opensees software that can simulate the dynamic time history analysis is used. Both kinematic and inertial interactions are considered and Finite Element Method (FEM) is used to solve DSSI. The direct method applies to 3D modeling of the layered soil and column-pile. A Pressure Independ Multi Yield Surface Plasticity Model is used to simulate different kinds of clay behavior. Time history seismic analyses provide for the mass and stiffness matrices to evaluate dynamic structural response with and without directivity effects for Near and Far Field earthquakes. Results show that the Multi-Yield-Surface-Kinematic-Plasticity-Model can be used instead of bilinear springs between piles and clay soil, for both Near Field and Far Field earthquakes. In addition, comparing Near and Far Field analyses, acceleration response spectrum at the top of the structure in the Far Field increases with the softness of the soil more than that in the Near field.

Dynamic soil-structure interaction: A three-dimensional numerical approach and its application to the Lotung case study

This paper presents a three-dimensional non-linear finite element (FE) approach to analyse the dynamic soil-structure interaction (SSI) phenomena observed at the Lotung Large-Scale Seismic Test (LSST) site. The numerical study is carried out in the time domain by a commercial FE code, taking into account the non-linear behaviour of soil and the multi-directional nature of real seismic events. The soil response is simulated by an isotropic hardening elasto-plastic hysteretic model (HSsmall) implemented in the material model library of the code. This model allows to describe the non-linear cyclic response ranging from small to large strain amplitudes and to account for the variation of the initial stiffness with depth.In the paper, the FE numerical approach is first validated through a series of parametric analyses simulating simplified cases (i.e. linear visco-elastic structures founded on a homogeneous linear visco-elastic soil deposit) for which analytical solutions exist. Then, it is adopted to back-analyse the behaviour of the 1/4-scale nuclear power plant containment structure constructed at the Lotung LSST site which was shook by several earthquakes of different intensities and frequency contents. The FE results are thus compared to the recorded in-situ free-field and structural motions, highlighting the satisfactory performance of the numerical model in replicating the observed response. The overall outcome of this research proves that nowadays complex dynamic SSI phenomena can be tackled by direct approach, overpassing the strong simplifications of the well-established substructure approaches.

Dynamic vertical impedance of a submarine strip foundation in ocean engineering: Water wave pressure effect

Many papers in the literature present studies of the interaction of sea waves, structures, and soil; however, most of these studies focus on the pore pressures and stresses in the soil around structures. Very little knowledge has been obtained regarding the impedance of a foundation considering the coupling of the water wave pressure effect (WPE) and dynamic soil-structure interaction (DSSI), as classical impedance functions are obtained based on a foundation on an elastic half-space with a stress-free surface. Impedance functions can be used to study the dynamic responses of a structure using the substructure method during the serviceability limit state design. This paper studies the forced vertical vibration of a strip foundation on a poro-elastic seabed with surface subjected to water wave pressures. The strip foundation on the seabed is simultaneously excited by water wave and other external forces at the same frequencies as water waves (with WPE-DSSI coupled). Three new impedance functions for foundations in ocean engineering are defined. Selected results for the new impedance functions are examined based on different water depth, wave height, wave frequency, and poroelastic material. The results show that for a rigid strip foundation in ocean engineering, both its total impedance and effective impedance are displacement dependent.

Dynamic soil structure interaction of bridge piers supported on well foundation

For both steel and RCC Bridges passing rivers or creeks, common practice in many countries is to provide concrete wells to support the bridge girders. For many bridges that are strategically important in terms of defense or trade, it is essential that they remain functional even after a strong earthquake hits the structure. The present state of the art for design of well foundation is still marred with a number of uncertainties where a simplistic pseudo static analysis of its response only prevails, though it is a well-known fact that loads from super structure, character of soil and its stiffness plays an important role in defining its dynamic characteristics. The present paper is thus an attempt to present a dynamic analysis model trying to cater to a number of such deficiencies as cited above and also provide a practical model (amenable to design office application) that can be used to estimate the pier, well and soil's dynamic interaction

Tuned Mass Damper Positioning Effects on the Seismic Response of a Soil-MDOF-Structure System

Tuned mass dampers (TMDs) are effective structural vibration control devices. However, very little research is available on the experimental investigation of TMDs and their performance in systems undergoing dynamic soil-structure interaction. Geotechnical centrifuge tests are conducted to investigate story positioning effects of single and multiple TMDs in a soil-MDOF-structure system. The criteria for optimal story positioning will be established, and it is shown that story positioning influences TMD performance more than the number of TMDs used. Non-optimal story positioning was found to have the potential of reducing damping efficiency, amplifying peak structural response, and inducing lengthier high-intensity motion.

A nonlinear constitutive model for beam elements with cyclic degradation and damage assessment for advanced dynamic analyses of geotechnical problems. Part I: theoretical formulation

Dynamic soil–structure interaction (SSI) represents an interdisciplinary subject characterized by complex geometrical and material nonlinearities affecting both the soil and the structural components of the system under study. In the current practice, SSI problems are often solved using the so-called substructure method based on decomposing the superstructure-foundation-soil system into two subsystems whose response is determined independently. The direct method is a more general procedure to tackle SSI problems which is in principle capable of accounting for both soil and structural nonlinearities. Despite this generality, most of the current computational platforms are specialized either for structural applications or for geotechnical applications. Whereas the formers are capable to accurately reproduce the nonlinear response of the structural elements, they are usually poor in modeling soil nonlinear behaviour especially under earthquake loading. On the other hand, the latter do the reverse: they are advanced in modeling soil response but typically rough in reproducing the behaviour of the structural components of the system. Inevitably, all structures interact with the ground and therefore the need to model material and geometric nonlinearities maybe important both in the ground and structural elements. The variation of the stiffness mismatch between soil and structural elements during ground motions is one of the most influential parameters for the assessment of the kinematic component in SSI problems. The variation of the stiffness ratio is mainly governed by material nonlinearity that can develop in either the soil or the structural parts of the system. This paper presents a nonlinear constitutive model for beam elements that is compatible with performance–based earthquake engineering principles because it is capable to simulate the cyclic degradation of mechanical properties and to assess the damage suffered by the structural system. The proposed model is based on distributed plasticity and can be easily implemented in any computational platform allowing the use of an explicit solver. The article describes the theoretical aspects of the model. Validation and application of the model to the solution of a dynamic soil–structure interaction problem where the nonlinear behaviour of geomaterials is coupled with the inelasticity of structural elements, are presented in a companion paper (Andreotti and Lai in Bull Earthq Eng 2017).

A nonlinear constitutive model for beam elements with cyclic degradation and damage assessment for advanced dynamic analyses of geotechnical problems. Part II: validation and application to a dynamic soil–structure interaction problem

The variation of the stiffness mismatch between soil and structural elements during ground motions is one of the most influential parameters for the assessment of the kinematic component in SSI problems. The variation of the stiffness ratio is mainly governed by material nonlinearity that can develop in either the soil or the structural parts of the system. The direct approach, which is in principle capable of accounting for both soil and structural nonlinearities, provides the “complete solution” to the SSI problem. The implementation of this approach requires the availability of general-purpose computational platforms where the modeling process is very often, particularly time-demanding. Even when using this kind of software, the substructure approach, suitable only if the system behave linearly or weakly nonlinearly, is often preferred over the direct method because it allows to split the model in two parts, simplifying the problem. The nonlinear constitutive model for beam elements presented in the companion paper (Andreotti and Lai in Bull Earthq Eng, 2017, doi:10.1007/s10518-017-0090-1) is conceived to be embedded in computer programs oriented to geotechnical applications to overcome their typical limitations in structural modeling. The proposed constitutive model is capable to simulate the cyclic degradation of stiffness and strength. Furthermore it allows to assess the damage experienced by the structure. Coupling the inelasticity of structural elements with the highly nonlinear behaviour of soils in a computer program specialized for geotechnical applications might hopefully contribute to bridging the gap between geotechnical and structural community when attempting to solve problems of soil–structure interaction. This paper presents the implementation, validation and application of the model to solve a dynamic soil–structure interaction problem by coupling the nonlinear behaviour of ground with the inelasticity of the structural elements.

Impact of climate change on dynamic behavior of offshore wind turbine

ABSTRACTGlobal warming is expected to change the wind and wave patterns at a significant level, which may lead to conditions outside current design criteria of monopile supported offshore wind turbine (OWT). This study examines the impact of climate change on the dynamic behavior and future safety of an OWT founded in clay incorporating dynamic soil–structure interaction. A statistical downscaling model is used to generate the time series of future wind speed and wave height at local level. The responses and fatigue life of OWT are estimated for present and future periods and extent of change in design is investigated at offshore location along the west coast of India. Wind speed, wave height, and wave period data are collected from the buoy deployed by Indian National Centre for Ocean Information Services and the future climate for the next 30 years is simulated using the general circulation model corresponding to Special Report on Emission Scenarios A1B scenario. The OWT is modeled as Euler–Bernoulli beam and soil–structure interaction is incorporated using nonlinear p-y springs. This study shows that changes in design of OWT are needed due to increased responses owing to the effect of climate change. Fatigue life is found to be decreased because of climate change.

Simultaneous Effects of Soil-structure and Masonry Infill-Structure Interactions on Seismic Performance of Steel Frames

In this paper, the effects of dynamic Soil-Structure Interaction (SSI) on seismic performance of steel frames with infill wall were investigated. This study assesses these buildings seismic performance utilizing the static analysis of nonlinear simulated models to obtain the structures response. The investigation was based on structures with design and detailing characteristics representative of 2800 Iranian code. To consider the dynamic soil-structure interaction effect, soil can be modeled with a set of springs and dashpots. The results show soil-structure interaction and presence of infill wall in building can be able to change the seismic performance of frame structures. Dynamic soil-structure interaction increases system flexibility. Increasing the number of column spans in all cases of loading, increases the amount of the base shear and story drift. The analysis results, also, show that reducing the shear wave velocity in soil beneath the structure, causes soil-structure interaction effects on nonlinear structural response become significant.

Computing the modal characteristics of structures considering soil-structure interaction effects

Modal analysis of structures is usually performed based on finite element models where the structures are considered undamped and fixed at their base, disregarding any interaction with the soil. In some cases though, these modeling assumptions may lead to erroneous estimates. This paper presents a finite element-perfectly matched layers model which is used to compute the modal characteristics of a frame structure considering dynamic soil-structure interaction effects. The modal characteristics of the structure are computed with respect to the soil stiffness revealing the key effects of dynamic soil-structure interaction. The analysis shows how soil-structure interaction affects the fundamental as well higher modes of the structure, involving increase in modal damping ratios and engendering complex valued mode shapes.

Soil-Structure Interaction in Transversely Isotropic Layered Media Subjected to Incident Plane SH Waves

The dynamic soil-structure interaction (SSI) for incident plane SH waves is analyzed for a two-dimensional (2D) model of a shear wall on a rigid foundation by using the indirect boundary element method (IBEM). The rigid foundation utilized in this study is embedded in transversely isotropic (TI) soil layers over bedrock. The accuracy of the IBEM method is verified and analyzed by setting a semicylindrical, rigid foundation-shear wall structure system in the single TI soil layer and multiple TI soil layers over bedrock. This study shows that the TI characteristics of the site have a significant impact on the effective input motion and the superstructure response. In a single soil layer, the increase in the shear modulus ratio in the vertical and horizontal directions has a certain degree of amplified action on the effective input motion and the superstructure response. Simultaneously, the corresponding peak frequency of the response increases. In multiple soil layers, the changes in the effective input motion and the superstructure response are also affected by the TI characteristics of the soil layers, and the impact of this effect is related to the sequence of the layers.

Quantifying dynamic soil-structure interaction for railway induced vibrations

Predicting the vibration response of buildings due to excitation from a nearby railway is an important step in ensuring the protection of nearby residents and the integrity of manufacturing processes. It is difficult and expensive to undertake measurement campaigns to determine the dynamic soil-structure interaction, that is, how vibrations propagate from the ground and through the building. Numerical models that encompass the track, soil and building are rarely used due to their computational expense and the required detailed parameter inputs. In practice, vibration attenuation through the foundation, floors and spans is accounted for using generic adjustment factors.In this study, the response of a building to railway induced vibration is investigated. Three different configurations of the railway-soil-building system are modelled using a coupled finite element–boundary element model. The first configuration includes both the railway and a nearby building, the second configuration contains only the railway and surrounding soil; and the final configuration contains a building that is excited by nearby impulses on the soil’s surface. By comparing the vibration levels in each of these configurations at various locations within the building and on the free surface, the magnitude of the interaction between the railway and the building can be investigated. Factors affecting the soil-structure interaction, such as soil type, building geometry, distance between the railway and building, and excitation type (whether train passage or impacts) are explored.The findings of the study support the separation of the source and receiver terms, demonstrating that the railway can be represented by a series of on-soil impacts when characterising the building response, without significant loss of modelling accuracy. This result means that simplified computational models that do not include a detailed railway structure can be employed. It also suggests that the vibration response of the building can be determined by in situ measurements prior to railway construction.

Considering dynamic soil-structure interaction in design of high-speed railway bridges

This article presents preliminary theoretical results on the influence of dynamic soil-structure interaction (SSI) of slab foundations. Impedance functions, representing the dynamic SSI, were obtained from FE-models depicting the soil for a few cases of different geotechnical preconditions. The obtained impedance functions were attached to single-span bridges and HSLM-A analyses were performed. The effect of the impedance functions on the bridge response was studied and compared to the ultimate case of a bridge on rigid supports. The influence of SSI seems to have a significant effect on railway bridges. This study shows that by including this effect in bridge design, the damping ratio of the system is largely increased, giving lower acceleration amplitudes in the bridge, while the natural frequencies are less affected.

Appraisal of nonlinear dynamic soil-structure interaction model for pile foundation supported structure: a probabilistic approach

Appraisal of nonlinear dynamic soil-structure interaction model for pile foundation supported structure: a probabilistic approach