Soil Structure Interaction

To estimate soil-structure interaction (SSI) effects in two instrumented buildings different models are explored. Both system identification and analytical methods are used to calculate stiffnesses and frequencies associated with SSI effects. The later include procedures from the Mexico City building code as well as commercial software by mean of which piles group effects are also considered. Experimental data from two of the most significant and recent earthquakes recorded in the buildings are analyzed and comparisons suggest interesting conclusions about analytical considerations and actual behavior of the buildings and theirs foundations.

The interaction among structures, their foundations and the soil medium below the foundations alter the actual behaviour of the structure considerably than what is obtained from the consideration of the structure alone. Thus, a reasonably accurate model for the soil-foundation-structure interaction system with computational validity, efficiency and accuracy is needed in improved design of important structures. The present study makes an attempt to gather the possible alternative models available in the literature for this purpose. Emphasis has been given on the physical modeling of the soil media, since it appears that the modeling of the structure is rather straightforward. The strengths and limitations of the models described in a single paper may be of help to the civil engineers to choose a suitable one for their study and design.

The scope of the paper is to present some aspects of the development of a "macro-element" for dynamic soil-structure interaction analyses of shallow foundations. Initially the concept of "macro-element" is introduced and is illustrated with the aid of a very simple example originating from structural engineering. Then the link is made with the modeling of the dynamic response of shallow

The effects of the foundation compliance on the dynamic response of yielding systems are evaluated using rigorous dimensional analysis. To this end, a soil-foundation-structure system is subjected to strong ground motion and its seismic response is determined in terms of dimensionless parameters. The seismic demand of the system is calculated as a function of meaningful engineering parameters, such as the yielding acceleration and yielding displacement of the structure, the system mass and damping, as well as the dynamic characteristics of the foundation. It is proved that the seismic demand is strongly dependent on the foundation to excitation pulse predominant frequency ratio. For large values of yielding acceleration, the demand depends strongly on the yielding displacement and the mass. Moreover, there is a strength range where an increase in strength results in an increase in displacements -a counter intuitive situation. The larger the yielding displacement, the larger the seismic demand. Furthermore, the larger the foundation soil mass, the larger the seismic demand. Finally, an application of the procedure on an actual structure proves that soil-foundation-structure interaction (SFSI) is not always beneficial for the structure.

The Tower of Pisa survived several strong earthquakes undamaged over the last 650 years, despite its leaning and limited strength and ductility. No credible explanation for its remarkable seismic performance exists to date. A reassessment of this unique case history in light of new seismological, geological, structural, and geotechnical information is reported, aiming to address this question. The following topics are discussed: (1) dynamic structural identification based on recorded earthquake data; (2) geophysical site characterization using a two-dimensional array; (3) seismic hazard and site response analysis considering horizontal and vertical motions; and (4) soil-structure interaction (SSI) analysis calibrated using lab and field data. A substantial shift in natural period, from about 0.35 s to over 1 s (a threefold increase, the largest known for a building of that height) caused by SSI, a wave parameter (1/ σ) of about 0.3, and a minor effect of vertical ground motion are i...

This paper presents a general 2.5D coupled finite element-boundary element methodology for the computation of the dynamic interaction between a layered soil and structures with a longitudinally invariant geometry, such as railway tracks, roads, tunnels, dams, and pipelines. The classical 2.5D finite element method is combined with a novel 2.5D boundary element method. A regularized 2.5D boundary integral equation is derived that avoids the evaluation of singular traction integrals. The 2.5D Green's functions of a layered halfspace, computed with the direct stiffness method, are used in a boundary element method formulation. This avoids meshing of the free surface and the layer interfaces with boundary elements and effectively reduces the computational efforts and storage requirements. The proposed technique is applied to four examples: a road on the surface of a halfspace, a tunnel embedded in a layered halfspace, a dike on a halfspace and a vibration isolating screen in the soil.

In this paper a typical soil–structure interaction problem is considered, the case of a vertical pile installed in sand and submitted to an axial compression loading. Results from two full scale pile tests are analysed and the tests are reproduced by numerical simulations via finite ...

Piles are extensively used as a means of slope stabilization. Despite the rapid advances in computing and software power, the design of such piles may still include a high degree of conservatism, stemming from the use of simplified, easy-to-apply methodologies. This paper develops a hybrid method for designing slope-stabilizing piles, combining the accuracy of rigorous three-dimensional (3D) finiteelement (FE) simulation with the simplicity of widely accepted analytical techniques. It consists of two steps: (1) evaluation of the lateral resisting force (RF) needed to increase the safety factor of the precarious slope to the desired value, and (2) estimation of the optimum pile configuration that offers the required RF for a prescribed deformation level. The first step utilizes the results of conventional slope-stability analysis. A novel approach is proposed for the second step. This consists of decoupling the slope geometry from the computation of pile lateral capacity, which allows numerical simulation of only a limited region of soil around the piles. A comprehensive validation is presented against published experimental, field, and theoretical results from fully coupled 3D nonlinear FE analyses. The proposed method provides a useful, computationally efficient tool for parametric analyses and design of slope-stabilizing piles.

In the conventional design, buildings are generally considered to be fixed at their bases. In reality, flexibility of the supporting soil medium allows some movement of the foundation. This decreases the overall stiffness of the building frames resulting in a subsequent increase in the natural periods of the system and the overall response is altered. The present study considers low-rise building frames resting on shallow foundations, viz. isolated and grid foundation. Influence of soil-structure interaction on elastic and inelastic range responses of such building frames due to seismic excitations has been examined in details. Representative acceleration-time histories such as artificially generated earthquake history compatible with design spectrum, ground motion recorded during real earthquake and idealized near-fault ground motion, have been used to analyze the response. Variation in response due to different influential parameters regulating the effect of soil-flexibility is presented and interpreted physically. The study shows that the effect of soil-structure interaction may considerably increase such response at least for low-rise stiff structural system. q

The aim of this study is to investigate the effect of thickness and width of tie beams on footings under eccentric loading. The chosen model contains 16 footings connected with tie beams. However the effect of thickness and width of tie beams on vertical and horizontal displacement as well as the contact pressure, moment and shear have been investigated. The footing dimensions are (2.0*2.0) m for corner footings, (2.50*2.50) m for edge footings and (3.0*3.0) m for middle footings). The model contains three critical footings with dimensions as follows:-(2.50 * 1.50) m, (2.0 * 1.0) and (1.0 * 1. 0) m respectively. Isolated footings have fixed depth (D) =0.5m connected with tie beams with variable width (b=0.6D, 0.7D, 0.8D, 0.9D and 1.0D) m and thickness (h=1.0D, 1.5D, 2.0D and 2.5D). A finite element package of the PLAXIS 3D-foundation version 15 has been used to simulate theoretically the model. All of the above assumptions have used with variable depth of footing (Df =0.0D, 0.5D, 1.0D and 1.5D). For eccentric loading it was found that the vertical displacement (settlement) and horizontal displacement under footings connected with tie beams decreases with increasing the thickness and width of tie beams by about (20 to 40)%. The settlement becomes almost uniform along axis and increasing the thickness and width of tie beam decrease the differential settlement. Also it was found that the values of the total normal stress (contact pressure) decrease with increasing width of tie beam and tie beam thickness by about (30 to 40)%. It was also found the bending moment as well as shear force values decrease with increasing the thickness and width of tie beams by about (30 to 40)%.

A new method for nonlinear analysis of Euler-Bernoulli beams resting on heterogeneous, multilayered soil is presented. The governing differential equations for beam and soil displacements are obtained using the principle of virtual work, and these equations are solved using one-dimensional finite-element and finite-difference methods. Using the analysis, beam displacements can be obtained as a nonlinear function of applied loads if the beam and soil geometry and properties are known. The distinct feature of the analysis is that beam responses with accuracy comparable with those obtained from equivalent two-dimensional finite-element analysis are obtained within seconds. Examples illustrate how the proposed method can be applied in practice to obtain beam displacements in soil deposits that are characterized with nonlinear stress-strain relationships, have multiple layers, and have a modulus varying spatially within each soil layer. Parametric studies are performed that highlight the effects of soil layering and nonlinearity on the beam response.

— This study aims to investigate the effect of tie beam dimensions (length and height) connecting two isolated footings on the vertical displacement in Y-direction (settlement) and horizontal displacement in both X and Z directions. In the present study, a finite element package of a PLAXIS 3D version 1.1.3.16 (a finite element code for soil and rock analysis) has been used to investigate the behavior of two isolated footings of different dimensions connected with tie beam. The dimensions of left footing are fixed LL= (1.0 X 1.0B) and the right footing dimensions are variable LR= (1.0 X 1.0B), (1.0 X 1.5B) and (1.0 X 2.0B). The width of the two footings is fixed (B=1.0m). The thicknesses of the two footings are variable (t=0.3B, 0.4B, 0.5B and 0.6B). The tie beam between footings has variable lengths (Ltie =0.5B, 1.0B, 1.5B and 2.0B). The height of the tie beams is variable (h=1.0t, 1.5t, 2.0t and 2.5t) and the width of tie beam is fixed (b=0.25m). All of the above assumptions have done with variable effect of depth of footing (df =0.0B, 0.5B, 1.0B and 1.5B). In addition, the angle of internal friction in sandy soil has been taken (Ø=30°, 35°, 40°and 45°). However, cohesion for clayey soil has been taken as (ϲ=10, 15, 20 and 25) KN/m2. It was found that the vertical displacement in Y-direction (settlement) and horizontal displacement in both X and Z directions increases with increasing the length of tie beam. Also, the vertical displacement in Y-direction (settlement) and horizontal displacement in both X and Z directions decreases with increasing the angle of internal friction in sandy soil as well as cohesion in clayey soil. The vertical displacement in Y-direction (settlement) and horizontal in X and Z directions decreases with increasing the height of tie beam. Increasing the depth of footings leads to decreasing the vertical displacement in Y-direction (settlement) as well horizontal in X and Z directions.

Micropiles are being applied in foundation rehabilitation projects to enhance the pullout capacity of the existing foundation system and minimize the vertical deflection of the structures. Consequently, the pullout load-displacement behavior is important for the design of micropiles used for the rehabilitation of foundations subjected to pullout. In this paper, we present and evaluate analytical relationships for micropile pullout load-displacement behavior, which explicitly considers the micropile-soil interaction. The analytical relationships are kept simple and accessible to designers by assuming the micropile-soil interface to be elastoplastic. The model parameters are combined into scaling factors and a normalization factor that are found to significantly influence micropile load-displacement behavior. The closed-form analytical relationships are used to study the effect of model parameters on the predicted micropile yield behavior. The micropile load transfer behavior calculated by the model is discussed. The model is shown to replicate the field measured load-displacement curves for two cases. A variety of cases are analyzed to study the effect of grout pressure on micropile-soil interface parameters.

Ovaling deformations develop when waves propagate perpendicular to the tunnel axis. Two analytical solutions are used for estimating the ovaling deformations and forces in circular tunnels due to soil-structure interaction under seismic loading. In this paper, these two closed form solutions will be described briefly, and then a comparison between these methods will be made by changing the ground parameters. Differences between the results of these two methods in calculating the magnitudes of thrust on tunnel lining are significant. For verifying the results of these two closed form solutions, numerical analyses were performed using finite element code (ABAQUS program). These analyses show that the two closed form solutions provide the same results only for full- slip condition.

The interaction among structures, their foundations and the soil medium below the foundations alter the actual behaviour of the structure considerably than what is obtained from the consideration of the structure alone. Thus, a reasonably accurate model for the soil-foundation-structure interaction system with computational validity, efficiency and accuracy is needed in improved design of important structures. The present study makes an attempt to gather the possible alternative models available in the literature for this purpose. Emphasis has been given on the physical modeling of the soil media, since it appears that the modeling of the structure is rather straightforward. The strengths and limitations of the models described in a single paper may be of help to the civil engineers to choose a suitable one for their study and design.

Field and laboratory observations of seismic settlements of shallow foundations on granular soils that are not attributable to changes in density or liquefaction are explained in terms of seismic degradation of bearing capacity. Limit analysis using a Coulomb-type mechanism including inertial forces in the soil and on the footing gives expressions for seismic bearing capacity factors that are directly related to their static counterparts. Comparison of the two depicts dearly the rapid deterioration of the overall foundation capacity with increasing acceleration. Such periodic inertial fluidizafion causes finite settlements that are possible even in moderate earthquakes. Reduction in foundation capacity is due to both the seismic degradation of soil strength and the lateral inertial forces transmitted by shear to the foundation through the structure and any surcharge. A straightforward slidingblock procedure with examples is also presented for computing these settlements due to loss of bearing capacity for short time periods. This approach also leads to a design procedure for footings based on limiting seismic settlements to a prescribed value.

Classical analysis of seismic soil-structure interaction phenomena for the design of civil engineering structures and lifelines are based on two simplifying assumptions~: lateral homogeneity of the soil underneath the foundation and representation of the ground motion (free field) as a pulse train of vertically or obliquely incident plane waves. For large structures founded on flexible spread footings, these hypotheses are not valid any longer. Furthermore, data recorded after the installation of dense seismograph arrays have shown that seismic ground motions can have a strong spatial variability, even over short distances and irrespective of deterministic wave passage effects. We develop in this thesis some theoretical tools for the modelization and numerical analysis of the influence of the free field and soil spatial varibilities on the structural response. A probabilistic approach is chosen, and the structural response of interest is given by an integral formulation which considers these two aspects simultaneously. Relevancy of numerical implementations are enhanced by introducing a spectral reduction of the random dimension of the fluctuating part - large or small - of the uncertain soil mechanical parameters through its Karhunen-Loeve expansion. This technique is applied to the free field as well. The numerical results obtained for various realistic cases display some specific features whose consideration seems essential in the process of industrial design. Notably, some usefull trends and sensitivity of the structural response with the free field and soil spatial variabilities are derived.

In this paper, the economical and structural efficiency of friction pendulum bearings (FPB) for retrofitting typical seismically vulnerable bridges in the State of Illinois is studied. For this purpose, a bridge was carefully selected by the Illinois Department of Transportation (IDOT) to represent typical seismically vulnerable bridges commonly used in the State of Illinois. A comprehensive structural model of the bridge was first constructed for seismic analysis. An iterative multi-mode response spectrum (MMRS) analysis of the bridge was then conducted to account for the nonlinear behavior of the bridge components and soil-bridge interaction. The calculated seismic demands were compared with the estimated capacities of the bridge components to determine those that need to be retrofitted. It was found that the bearings, wingwalls and pier foundations of the considered typical bridge need to be retrofitted.

A comprehensive study carried out to assess the seismic response of a 59-span bridge using a refined inelastic modeling approach and considering Soil-Structure Interaction (SSI) is summarized in this paper. The focus is on describing the methodology adopted to idealize the bridge and its foundation system, while only highlights from the extensive elastic and inelastic analyses are presented. The bridge represents a typical case of vulnerable complex bridges since it was built in the early seventies with minimal seismic design requirements at a distance of about 5 km from a major fault. The SSI analysis is significant in this study due to the length of the bridge, the massive and stiff foundation, and the relatively soft deep soil of the site. A series of three-dimensional dynamic response simulations of the entire bridge are conducted using several analysis tools to verify the developed analytical models. The performance-based assessment study employs 144 site-specific input ground motions representing three seismic scenarios, corresponding to 500, 1000 and 2500 years return periods, to identify areas of vulnerability in the 2164-meter bridge at various hazard levels. It is concluded that the seismic response of the bridge at the 500 years ground motions does not meet today's standards, while the demands under the effect of the 1000 years ground motions almost exceed the capacity of most bridge components. The demands significantly increase under the effect of the 2500 years earthquake scenario and considerably exceed the collapse limit states. The results clearly reflect the benefit of retrofitting different bridge components to mitigate the anticipated seismic risk. The presented assessment study contributes to improve public safety by exploiting the most recent research outcomes in predicting the seismic response of complex highway bridges, which are essential for developing reliable and cost-effective retrofit strategies.

A shake-table series of experiments has provided valuable data for liquefaction-induced lateral spreading effects on pile foundations. In this paper, this data is employed to estimate peak soil pressure on single piles embedded in a laterally spreading liquefied layer, and to calibrate a nonlinear elasto-plastic computational model, within the open framework for simulation OpenSees. On this basis, a user interface

Al-Madinah City is the second holiest city in the Muslim world. Millions of visitors densely populate the city center around the Grand AlHaram Mosque most of the year. The recent seismic activity experienced near Al-Madinah city in 2009 triggered researchers and engineers to examine and improve building safety and structural seismic resistance. Owing to the seismic activities of the region and the geological nature of Al-Madinah, which comprises volcanic basaltic rocks surrounding clay rich agriculture land, piled-raft foundation was the design choice for many buildings including the Grand Mosque first extension project. The supporting piles extend deep into the basaltic stratum up to 50 m in some locations.The behavior of the piled raft foundation under earthquake loading would influence the seismic performance of the supported structure. Based on observations during past seismic events, it was suggested that the lateral inertial force of the building is supported by frictional resistance beneath the raft as well as piles shaft resistance. Moreover, the raft could potentially experience excessive settlement. As a result, the ratio of the load carried by the raft to the total structural load could increase after the earthquake event. The case study presented in this paper investigates the seismic performance of the piled raft foundation of a selected building in the city center. The seismic response of the piled raft foundation is analyzed using three-dimensional finite element model employing the computer program Plaxis 3D. The foundation response during the earthquakes is investigated. The result has shown that the piled raft configuration has better lateral resistance to the seismic loading than the piled cap configuration. The results also has shown that reducing the piles length by 20% has increased the resistance to lateral shaking and reduced the horizontal response of the piled-raft foundation. ABSTRAIT La ville d'Al-Madinah est la deuxième ville la plus sainte du monde musulman. Des millions de visiteurs densément peuplent le centre-ville autour de la Grande mosquée (AlHaram) la plupart de l'année. L'activité sismique récente menée près de la ville d'Al-Madinah en 2009 a déclenché des chercheurs et des ingénieurs pour examiner et améliorer la sécurité des bâtiments et la résistance sismique structurale. En raison des activités sismiques de la région et de la nature géologique d'Al-Madinah, qui comprend des roches basaltiques volcaniques entourant une terre agricole riche en argile, la base de poteaux-radeaux a été choisie pour de nombreux bâtiments, y compris le projet de première extension de la Grande Mosquée. Les pieux de soutien s'étendent profondément dans la strate basaltique, jusqu'à 50 m dans certains endroits. Le comportement de la base de radeau empilée sous le chargement du tremblement de terre influencerait la performance sismique de la structure supportée. Sur la base des observations effectuées lors des événements sismiques passés, il a été suggéré que la force d'inertie latérale du bâtiment est soutenue par une résistance à la friction sous le radeau ainsi que la résistance de l'arbre des pieux. En outre, le radeau pourrait potentiellement avoir un règlement excessif. En conséquence, le rapport de la charge portée par le radeau à la charge structurelle totale pourrait augmenter après l'événement sismique. L'étude de cas présentée dans cet article étudie la performance sismique de la base de radeaux empilés d'un bâtiment sélectionné dans le centre-ville. La réponse sismique de la base de radeau empilée est analysée à l'aide d'un modèle à éléments finis tridimensionnels utilisant le programme informatique Plaxis 3D. La réponse de la fondation lors des tremblements de terre de conception est étudiée. Le résultat a montré que la configuration de radeau empilée a une meilleure résistance latérale au chargement sismique que la configuration de capuchon empilée.

Piles have been traditionally designed to ensure the transfer of the whole structural load to the soil in which they are embedded. It is now largely accepted that this way of doing is unduly conservative, especially in those cases in which an unpiled raft is sufficient to guarantee a satisfactory safety level. Nevertheless, it is still very common in the daily practice, sometimes for the restrictions imposed by local codes and regulations. Much research efforts have been dedicated to a more rational design of piled foundations, essentially based on a proper collaboration among raft and piles not only for increasing the overall stiffness of an unpiled raft but, if required, also for increasing its capacity, for controlling differential settlements, for reducing the state of stress into the raft. With no claim to cover any single aspects, some design options will be presented, providing some insight into a rational approach to piled raft design.

A critical review of past earthquakes reveals damage/failure of important lifeline facilities like elevated water tanks in recurrence, leading to serious hazards even after the event. In the context of such hazards indicating deficiencies in the existing seismic design strategy of such structures, dynamic characteristics of elevated tanks supported by cylindrical shaft (shaft staging) are comprehensively studied in the first part of present investigation. The same is made through analytical formulations developed and validated by rigorous finite element analysis and small-scale experimentation. Subsequent examination on seismic response of representative tanks indicates that the columns of the frame-supported tanks (tanks with frame staging) and the wall of the shaft-staging of such reinforced concrete (R/C ) tanks are susceptible to tension, particularly at tank empty condition. Such possibility seems to be further aggravated if the effect of soil-structure interaction (SSI) is ignored in design. Identifying the deficiencies in current design, simple design procedure of such elevated tanks utilizing the formulations developed is proposed. Torsional vulnerability of shaft-supported elevated water tanks is also identified to be marginal as opposed to the same for frame supported ones.

The development and extension of large cities creates a need for multiple shallow tunnels in the soft ground of building areas. Prediction of the ground settlement caused by the tunnel excavation is a major engineering challenge. A numerical simulation using a ®nite element method was implemented in the aim of developing a procedure to predict the movement induced by shield tunnelling in soft soil. This study describes a two-dimensional modelling and compares two procedures. The ®rst procedure is done in a simple way (called``decon®nement modelling'') simulating the excavation using a stress decrease vector exerted on the excavation boundary (inside the tunnel) described by a stress release scalar parameter l (named the``decon®nement factor''). The second procedure is composed of a complete stage of modelling (called``phase modelling'') taking into account dierent phases which simulate the dierent kinds of interactions between the tunnel and the soil (decon®nement, lining installation, pore pressure applied on the lining, and weight of the lining). Using a shallow lined tunnel with homogeneous soil conditions, the two procedures are analysed and compared. Then, the second modelling procedure is applied to the case of the metro of Lyon where ®eld data have been obtained. Observations of the results and comparison with the experimental data demonstrate that the proposed modelling is adequate for the analyses of settlement induced by tunnelling in soft soil. #

This paper describes the design, fabrication and commissioning of a single axis laminar shear box for use in seismic soil-structure interaction studies. A laminar shear box is a flexible container that can be placed on a shaking table to simulate vertical shear-wave propagation during earthquakes through a soil layer of finite thickness. The laminar shear box described in this paper was designed to overcome the base shear limitations of a small shaking table at The University of Western Ontario. The design details of the box are provided in addition to results of dynamic tests performed to commission the box. A synthetic clay comprising sodium bentonite mixed with diluted glycerin was used as the model soil and 1-G similitude theory was employed to maintain model to prototype similarity. The model soil was compacted into the container in lifts to achieve soil stiffness that increased with depth. A series of shaking table tests and numerical analyses that were performed to study the performance of the laminar box and non-linear seismic behavior of the model clay are described. The results of this study show that the laminar box does not impose significant boundary effects and is able to maintain 1-D soil column behavior. In addition, the dynamic behavior of the model clay during scaled model tests was found to be consistent with the behavior measured during cyclic laboratory tests.

The two papers describe trends of the apparent system periods, , and damping factors, , in recorded response of 56T 0 buildings (A1 to A45, and B1 to B14 in of part II) to 15 California earthquakes. The building, foundation, and soil are viewed as an equivalent linear system, excited by horizontal ground motion. Only inertial interaction is considered as ''the more important effect for foundations without large, rigid base slabs or deep embedment'' (by allowing one translation and rocking of the foundation). The kinematic interaction (modification of the free-field motion by the foundation in absence of inertial forces) is neglected as ''second order.'' Rocking and torsional excitation components of the incident motion, differential motions of extended foundations, warping of flexible foundations, and nonlinear soil response due to soilstructure interaction (SSI) are not mentioned. The papers aim to verify the ''simplified analytical procedures similar to those in the BSSC and ATC codes.'' This discussion (1) requests some clarifications; (2) suggests that time-dependent changes in (caused by nonlinear response of soil during SSI) should T have been included in the analysis; and (3) comments on the conditions when kinematic SSI should not be neglected.

The paper describes a new approach and its practical implementation for the analysis of the inelastic dynamic response of bridges with soil-structure interaction using multiple analysis platforms. The development is presented through an application test bed; the Meloland Road Over-crossing (MRO) bridge. The structure was heavily instrumented and has been shaken several times by significant earthquakes, rendering it an ideal

Soil-structure interaction (SSI) Performance-based design (PBD) Seismic design of buildings Underground stories Uniform hazard spectrum (UHS) Ground response analysis a b s t r a c t This paper investigates the seismic performance of moment-resisting frame steel buildings with multiple underground stories resting on shallow foundations. A parametric study that involved evaluating the nonlinear seismic response of five, ten and fifteen story moment-resisting frame steel buildings resting on flexible ground surface, and buildings having one, three and five underground stories was performed. The buildings were assumed to be founded on shallow foundations. Two site conditions were considered: soil class C and soil class E, corresponding to firm and soft soil deposits, respectively. Vancouver seismic hazard has been considered for this study. Synthetic earthquake records compatible with Vancouver uniform hazard spectrum (UHS), as specified by the National Building Code of Canada (NBCC) 2005, have been used as input motion. It was found that soil-structure interaction (SSI) can greatly affect the seismic performance of buildings in terms of the seismic storey shear and moment demand, and the deformations of their structural components. Although most building codes postulate that SSI effects generally decrease the force demand on buildings, but increase the deformation demand, it was found that, for some of the cases considered, SSI effects increased both the force and deformation demand on the buildings. The SSI effects generally depend on the stiffness of the foundation and the number of underground stories. SSI effects are significant for soft soil conditions and negligible for stiff soil conditions. It was also found that SSI effects are significant for buildings resting on flexible ground surface with no underground stories, and gradually decrease with the increase of the number of underground stories.

The aim of this paper is to evaluate the influence of negative skin friction in pile foundations. Three dimensional nonlinear analyses for a single pile and pile groups were carried out for a specific case and some case studies as well. Contrary to simplified conventional analysis in which the predictions are usually overestimated and could be considered as an upper limit, it was found that the dragload of a pile in a group depends on the surface load, the pile configuration, the pile position in a group, the ultimate skin friction and the interface stiffness. It has been demonstrated that for fixed-head friction pile groups the dragload group effect is significantly greater than in the case of free-head end-bearing pile groups. Moreover, predictions for internal piles have shown considerably smaller dragloads for fixed-head piles, which is in accordance with experimental findings. It has also been demonstrated that when the construction of an embankment precedes the application of the foundation working load, the effect of negative skin friction is considerably smaller than in the reverse case.

This paper is concerned with the soil and water behaviour of elevated concrete water tank under seismic load. An artificial seismic excitation has been generated according to Gasparini and Vanmarcke approach, at the bedrock, and then consideration of the seismic excitation based on one dimension nonlinear local site has been carried out. Seven cases are chosen to make comparisons with direct nonlinear dynamic analysis, mechanical models with and without soil structure interaction (SSI) for single degree of freedom (SDOF), two degree of freedom (2DOF), and finite elements method (FEM) models. The analysis is based on superposition modal dynamic analysis. SSI and fluid structure interaction (FSI) have been accounted using direct approach and added mass approach respectively. The results show that a significant effects obtained in shear force, overturning moment and axial force at the base of elevated tank.

In this paper, a new double diaphragm shock tube facility for studying the structural response of a circular plate resting on soil, when subjected to a shock wave, is described. The present shock tube has been designed in the framework of a more extensive research program aimed at the investigation of underground tunnel lining under blast and fire conditions. The innovative features of the facility are an endchamber conceived to investigate soil-structure interaction and a burner equipment to heat the specimen in order to study to what extent thermal damage can affect the transmitted and reflected pressure wave as well as the structural response. Details of the shock tube design, construction and test procedure operations are discussed in the paper. Particular emphasis is placed on the principles that have driven the experimental equipment design choices. Numerical simulations have been performed to assess the ideal shock tube performance in terms of reflected pressure and test time duration as 2 well as to evaluate how far the fire testing situation actually is from that normally used in tunnel design.

Soil is a material dependent on the load history. The load history has a significant influence on stress distribution in the ground beneath the footing and the settlement of a foundation. In the paper the load history has been considered as the sequence of loading the ground with two strip footings. Differences in the distributions of stresses in the ground as well as the settlements of footings have been shown. Nonlinear loadsettlement relationship does not allow the application of the principle of superposition.

The study investigates the response of shallow foundations subjected to strong earthquake shaking. Nonlinear soil-foundation effects associated with large deformations due to base uplifting and soil failure are examined in comparison with the conventional linear approach. Soil behavior is represented with the elastoplastic Mohr-Coulomb model. The interplay between foundation uplifting and soil failure of the bearing capacity type is elucidated under static and dynamic conditions.

This paper presents the problem definition of the benchmark structural control problem for the seismically excited highway bridge. The benchmark problem is based on the newly constructed 91/5 highway over-crossing in southern California. The goal of this benchmark effort is to develop a standardized model of a highway bridge using which competing control strategies, including devices, algorithms and sensors, can be evaluated comparatively. To achieve this goal, a 3D finite-element model is developed in MATLAB to represent the complex behavior of the full-scale highway over-crossing. The nonlinear behavior of center columns and isolation bearings is considered in formulating the bilinear force–deformation relationship. The effect of soil–structure interaction is considered by modeling the interaction by equivalent spring and dashpot. The ground motions are considered to be applied simultaneously in two directions. A MATLAB-based nonlinear structural analysis tool has been developed and made available for nonlinear dynamic analysis. Control devices are assumed to be installed between the deck and the end abutments of the bridge. Evaluation criteria and control constraints are specified for the design of controllers. Passive, semi-active and active devices and algorithms can be used to study the benchmark model. The participants in this benchmark study are required to define their control devices, sensors and control algorithms, evaluate and report the results of their proposed control strategies. Copyright © 2009 John Wiley & Sons, Ltd.

For a class of civil engineering structures, that can be accurately represented by 'coupled shear walls' (CSWs), a discrete model for the analysis of the dynamic interaction with the underlying soil is proposed. The CSWs, with one or more rows of openings, rest on a rigid foundation embedded in the elastic or viscoelastic half-space. A hierarchical finite element model based on an equivalent continuum approach is adopted for the structure. A frequency-domain boundary element method is used to represent the half-space. Finally, the set of equations governing the response of the coupled soil-structure system to harmonic lateral loads acting on the structure is also given. The frequency deviation effect with respect to the fixed-base structure and the effects of radiation and material damping in the soil are presented for different characteristics of the structure and different soil properties.

L’utilisation de la methode des elements finis dans le domaine geotechnique est tres courante, pour des grands projets. On peut realiser des analyses par elements finis afin de verifier la stabilite d’un ouvrage en interaction avec son environnement, de controler les valeurs de deplacements admissibles et d’aider au dimensionnement des structures. L’etude consiste a mettre un modele numerique pour notre projet, qui concerne l’interaction sol avec differents ouvrages places dans un site urbain. Les ouvrages concernes sont : un tunnel, un bâtiment et une excavation. L’etude parametrique montre l’effet des parametres de calcul et des parametres geotechniques sur les resultats. Pour atteindre l’objectif vise, le travail sera divise en quatre chapitres. Apres une etude bibliographique sur l’interaction sol-structures, ce travail se compose de trois autres chapitres : Tout d'abord, un bref apercu de la methode des elements finis concerne l’historique, les concepts de base et l’utilisa...

A numerical prediction model for road traffic induced vibrations is developed. Dynamic soilstructure interaction at the source and the structure is accounted for. The first objective is to present the essential elements of the numerical prediction model. Secondly, experimental data will be used for the validation of the numerical model. Therefore, vibration measurements in and near a single family dwelling are performed during the passage of a truck at different speeds on an uneven concrete road with joints and on an artificial profile. The third objective is to present the ongoing research in the modelling of the single family dwelling.

Some structures may be very massive and may have to be located on relatively soft soil. In such cases, the soil adjacent to the structure behaves in a non-linear fashion and affects the response of the structure to the dynamic loading. An approximate hybrid approach to analyse soil -structure systems accounting for soil non-linearities has been developed in this paper. The approach combines the consistent infinitesimal finite-element cell method (CIFECM) and the finite-element method (FEM). The CIFECM is employed to model the non-linear (near-field) zone of the soil supporting the structure as a series of bounded media. The material properties of the bounded media are selected so that they are compatible with the average effective strains over the whole bounded medium during the excitation. The linear zone of soil away from the foundation, the far-field, is modelled as an unbounded medium using the CIFECM for unbounded media. The structure itself is represented by the FEM. The proposed method is used to model the dynamic response of a one-mass structure and a TV-tower supported on a homogenous stratum and excited by an earthquake. It was found that the secondary soil non-linearity might increase or decrease the base forces of tall slender structures depending on the type of structure, frequency content of the input motion and the dynamic properties of the near-field soil. q

Excavation works in urban areas require a preliminary risk damage assessment. In historical cities, the prediction of building response to settlements is necessary to reduce the risk of damage of the architectural heritage. The current method used to predict the building damage due to ground deformations is the Limiting Tensile Strain Method (LTSM). In this approach the building is modelled

In this work, a macroelement for shallow foundations on sands has been developed based on the theory of hypoplasticity. The incrementally nonlinear constitutive equations of the macromodel are defined in terms of generalized forces and displacements and are constructed based on the general approach proposed by Niemunis (Extended Hypoplastic Models for Soils. Habilitation Thesis, Bochum University, 2002). A suitable vectorial internal variable—mimicking the concept of intergranular strain introduced by Niemunis and Herle (Mech Cohes Frict Mater 2:279–299, 1997) for continuum hypoplasticity—is employed to provide the model sufficient memory of past displacement history to be able to reproduce the observed behavior under cyclic loading paths. As compared to similar macroelements formulated within the framework of the theory of elastoplasticity, the proposed approach has the advantage of a much simpler mathematical structure, which allows a straightforward implementation in existing structural analysis FE codes. The model performance has then been evaluated by comparing the model predictions with available experimental results from a series of small-scale model tests reported by Nova and Montrasio (Géotechnique 41:243–256, 1991). Overall, the model captures reasonably well the observed response under nonproportional, complex loading paths. A series of simulations reproducing the tests performed by di Prisco et al. (Shallow footing under cyclic loading: experimental behaviour and constitutive modelling. Patron, Bologna, 2003) has also demonstrated the potential of the proposed model to simulate the observed behavior of footings under cyclic loading paths, at least from a qualitative point of view.

This paper presents the problem definition of the benchmark structural control problem for the seismically excited highway bridge. The benchmark problem is based on the newly constructed 91/5 highway over-crossing in Southern California. The goal of this effort is to develop a standardized model of a highway bridge using which competing control strategies, including devices, algorithms and sensors, can be evaluated comparatively. To achieve this goal, a 3-D finite-element model is developed in MATLAB to represent the complex behavior of the full-scale highway crossing. The nonlinear behavior of center columns and isolation bearings are considered in formulating the bilinear force-deformation relationship. The effect of soil-structure interaction is considered by modeling the interaction by equivalent spring and dashpot. The ground motions are considered to be applied simultaneously in two directions. A MATLAB based nonlinear structural analysis tool has been developed and made available for nonlinear dynamic analysis. Control devices are assumed to be installed between the deck and the end-abutments of the bridge. Evaluation criteria and control constraints are specified for the design of controllers. Passive, semi-active and active devices and algorithms can be used to study the benchmark model. Participants in this benchmark study are required to define their control devices, sensors, and control algorithms, evaluate and report the results of their proposed control strategies.