Dynamic Soil-structure Interaction Research Articles

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.

Dynamic soil-structure interaction models for fragility characterisation of buildings with shallow foundations

Dynamic Soil–Structure Interaction (SSI), involving the coupling of structure, foundation and soil, is a crucial and challenging problem, especially when soil nonlinearity plays an important role. This paper shows the impact of adopting different SSI models on the assessment of seismic fragility functions. The linear substructure approach is initially adopted by implementing two different models, the first of which is one-dimensional and includes, between the foundation node and the ground, a translational elastic spring and a dashpot, whose stiffness and viscous damping are retrieved from the real and imaginary parts of the dynamic impedance at the first natural frequency of the structure. The second and more refined model is a Lumped-Parameter Model (LPM) accounting for frequency dependence of the impedance. In order to explore the sensitivity of fragility functions to the linearity assumption, an additional approach, including soil nonlinearities, is employed. A nonlinear footing macro-element is adopted to model the near-field behaviour by condensing the entire soil-foundation system into a single nonlinear element at the base of the superstructure. Energy dissipation through radiation damping is also accounted for. The superstructure response is simulated in all approaches as a simple nonlinear single-degree-of-freedom (SDOF) system. The comparison between the adopted approaches is evaluated in terms of their effects on the characterisation of fragility functions for unreinforced masonry buildings (URM) on shallow foundations.

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.

Boundary element analysis of dynamic interaction of anisotropic elastic half-space and structure under impact load

In this paper, a direct boundary element formulation for numerical modelling of threedimensional dynamic soil-structure interaction is briefly described. Formulation is applicable to problems involving isotropic and anisotropic elastic materials. It is based on the Laplace domain regularized boundary integral equations for the displacements under assumption of vanishing initial conditions and zero body forces. Mixed boundary elements are employed for the spatial discretization of the boundary integral equations. Subdomain technique is used to tackle problems involving piecewise homogeneous material properties. The described formulation is employed for the boundary element analysis of dynamic soil-structure interaction problem involving a structure which contains a cavity with a complex geometrical form. Soil is represented by a transversely isotropic elastic half-space. Effect of material anisotropy of half-space on the transient response of the embedded structure is assessed. It is observed that the shear modulus anisotropy have substantial impact on the displacements response. Influence of the Young’s modulus in the plane of isotropy is lesser but still pronounced.

Experimental investigation of the seismic effects during blasting works

The interested part of dynamic analysis is the blasting work effects propagation through soil. This type of the dynamic load can be significant when the soil structure dynamic interaction hasn´t favourable conditions. It can cause structural failures on buildings. The main aim of the paper is to investigate how we can estimate the magnitudes of the seismic waves during blasting works. The results are based on experimental studies.

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...

Experimental Assessment of the Effect of Vertical Earthquake Motion on Underground Metro Station

This paper presents experimental assessment of the effect of the ratio of vertical to horizontal peak ground acceleration (RVH) on underground metro station. An atrium-style metro station embedded in artificial soil subjected to earthquake loading is examined through shaking table tests. The experimental results for three different RVH, including soil acceleration, soil-structure acceleration difference, dynamic soil normal stress (DSNS), and structural dynamic strain, are presented and the results are compared with the case of horizontal-only excitation. It is found that for an atrium-style metro station, the differences in horizontal acceleration amplitude between the structure and the adjacent soil rise with increasing RVH, which are different at different depths. The most significant differences occur at the depth of the ceiling slab. It is also observed that both the amplitude and distribution of peak DSNS have obvious differences between the left and right side walls at all levels. It is therefore concluded that the RVH has a significant influence on dynamic soil-structure interaction. It is believed that under extreme earthquake loading, such as near fault zones, RVH is a parameter of paramount importance and should be accounted for in the seismic analyses and seismic performance assessments of underground structures, especially for those with zero or near-zero buried depth, such as atrium-style metro stations.

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.

Seismic wave input method for three-dimensional soil-structure dynamic interaction analysis based on the substructure of artificial boundaries

The method of inputting the seismic wave determines the accuracy of the simulation of soil-structure dynamic interaction. The wave method is a commonly used approach for seismic wave input, which converts the incident wave into equivalent loads on the cutoff boundaries. The wave method has high precision, but the implementation is complicated, especially for three-dimensional models. By deducing another form of equivalent input seismic loads in the finite element model, a new seismic wave input method is proposed. In the new method, by imposing the displacements of the free wave field on the nodes of the substructure composed of elements that contain artificial boundaries, the equivalent input seismic loads are obtained through dynamic analysis of the substructure. Subsequently, the equivalent input seismic loads are imposed on the artificial boundary nodes to complete the seismic wave input and perform seismic analysis of the soil-structure dynamic interaction model. Compared with the wave method, the new method is simplified by avoiding the complex processes of calculating the equivalent input seismic loads. The validity of the new method is verified by the dynamic analysis numerical examples of the homogeneous and layered half space under vertical and oblique incident seismic waves.

Assessment of dynamic soil-structure interaction effects for tall buildings: A 3D numerical approach

Soil-structure interaction (SSI) phenomena are typically studied in the frequency-domain using the substructure approach, involving several simplifications. In this study, SSI effects for a 20-storey building are studied numerically performing time-domain 3D non-linear dynamic analyses, using an elastoplastic nonlinear constitutive model for the soil. Three foundation systems - a relatively shallow, a deeply embedded and a pile foundation - and two soil profiles are investigated and compared. Specifically, relative merits of site amplification, kinematic interaction and inertial interaction are isolated, and the role of foundation deformability and local stratigraphy is highlighted. To isolate such features, the results of the complete 3D models are compared with those provided by 3D numerical analyses of the sole building, of the foundation-soil systems and of the free-field soil deposit.Numerical results show that, for tall buildings, an increase in foundation deformability leads to a decrease of the maximum base shear force (seismic demand), to a higher rigid rotation of the foundation, but not to appreciably higher displacements of the structure. Moreover, possible situations where a (decoupled) substructure approach can lead to a misinterpretation of SSI phenomena are highlighted, as in the case of deep foundations crossing very soft soil layers.In addition, the use of embedded pile elements was proven to be an effective strategy in reducing the computational cost when performing complex 3D simulations of dynamic SSI problems.

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.

Nonlinear assessment of offshore steel trestle subjected to wave and current loads

ABSTRACT Offshore steel trestles (OSTs) are commonly used to construct sea-crossing bridges. Presuming OSTs to be elastic to hydrodynamic hazards during their service lifetime is economically unacceptable due to their use as a temporary facility. In order to enhance operational safety and also reduce building costs, a nonlinear analysis framework is developed based on pushover approach and is applied to assess the nonlinear response of OSTs subjected to wave and current loads. The framework yields a nonlinear response curve that supplies structural nonlinear behaviors, capacities and plasticity development as functions of wave height. The dynamic amplification, current speed, loading direction, marine growth and soil-structure interaction (SSI) on the nonlinear response of the example OST under wave and current loads are then investigated. The results show that the structurally vulnerable positions of OST are located at the bottom of the piles and the joints connecting the brace to the pile.

Dynamic soil structure interaction model for beams on viscoelastic foundations subjected to oscillatory and moving loads

A new method for dynamic analysis of Euler-Bernoulli beams resting on multi-layered viscoelastic soil is presented. The governing differential equations for beam and soil displacements are obtained using the extended Hamilton’s principle, and these equations are solved using one-dimensional finite element method and analytical solutions. An iterative solution algorithm is used in conjunction with an implicit time integration scheme to obtain beam and soil responses as functions of time. The developed model resembles the traditional two-parameter spring foundation model but the analysis shows that the traditional foundation spring parameters cannot be prescribed a priori but determined as part of the solution. The model produces accurate beam response as illustrated by comparisons with equivalent two-dimensional finite element analysis. A few problems are analyzed that illustrate the novel features of the dynamic foundation model.

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.

Development of a reverse genetics system for snakehead vesiculovirus

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.

Vibration soil isolation analysis based on a 3-D frequency domain Direct Boundary Element implementation: GPGPU acceleration

A Direct Boundary Element implementation was accelerated by using General Purpose Graphics Processing Units (GPGPUs) to improve the performance in analysis of soil vibration isolation with trenches. The Boundary Element formulation is based on the 3D full space stationary fundamental (visco)elastic solutions. In this stationary Dynamic Soil-Structure Interaction (DSSI) problem, the soil is externally excited generating a propagation wave field. This resulting field induces vibrations on structures in the surrounding soil. Aiming to reduce the time required to calculate the vibration soil behavior, a code was developed with CUDA C++ and OpenMP to explore the capabilities provided by GPUs and multi-core CPUs. The performance analysis is conducted by comparing codes in two modes: one uses exclusively CPU and the other is GPU-accelerated. The implementation presents the vibration reduction as well as comparisons of computation time and speedup for two groups of CPU and GPU. The speedup ratios range from 8 to 60 comparing to the sequential version.