Showing papers on "Soil structure interaction published in 2009"

Role of Initial State, Material Properties, and Confinement Condition on Local and Global Soil-Structure Interface Behavior

Abstract: Difficulty in predicting the transfer of load from a structural element to the surrounding soil has limited the reliability of geotechnical design and performance. The remaining uncertainty in load transfer mechanics is primarily due to the localized nature of the mechanism. This study examines localized soil-structure interaction through a series of monotonic direct interface shear tests. Parameters investigated include relative density, particle angularity, particle hardness, surface roughness, normal stress, and normal stiffness. The soil-structure interface behavior is quantified in terms of the local two-dimensional displacement and strain distributions within the test specimens using particle image velocimetry. In addition, the localized zone of soil adjacent to the structural surface within which shear and volumetric strains occur is quantified. The relative density of the soil, and the relationship between particle characteristics (angularity and hardness) and surface roughness are shown to have the greatest effect on local interface behavior, followed by confining stress and stiffness conditions.

A model for the 3D kinematic interaction analysis of pile groups in layered soils

Abstract: The paper presents a numerical model for the analysis of the soil–structure kinematic interaction of single piles and pile groups embedded in layered soil deposits during seismic actions. A finite element model is considered for the pile group and the soil is assumed to be a Winkler-type medium. The pile–soil–pile interaction and the radiation problem are accounted for by means of elastodynamic Green's functions. Condensation of the problem permits a consistent and straightforward derivation of both the impedance functions and the foundation input motion, which are necessary to perform the inertial soil–structure interaction analyses. The model proposed allows calculating the internal forces induced by soil–pile and pile-to-pile interactions. Comparisons with data available in literature are made to study the convergence and validate the model. An application to a realistic pile foundation is given to demonstrate the potential of the model to catch the dynamic behaviour of the soil–foundation system and the stress resultants in each pile. Copyright © 2009 John Wiley & Sons, Ltd.

Seismic Interferometry of a Soil-Structure Interaction Model with Coupled Horizontal and Rocking Response

Abstract: This article presents a system identification analysis of a soil-structure interaction model with coupled horizontal and rocking response based on a combination of Fourier analysis, wave travel-time analysis, and a relationship between fixed-base, rigid-body, and system frequencies. The study provides insight into the coupling of the structural and soil vibrations useful for interpretation of seismic recordings in structures. The structural model captures one-dimensional shear-wave propagation in the structure. The analysis shows that the system functions with respect to foundation horizontal motion are those of the coupled soil-structure system, which differs from conclusions of earlier studies based on a model without foundation rocking. The energy of the system vibrational response is concentrated around the frequencies of vibration of the system, which depend on the properties of the structure, soil, and foundation. The analysis shows that the structural fundamental fixed-base (uncoupled) frequency f 1 is related to the wave travel time τ (from the base to the top) by f 1=1/(4 τ ) and that accurate measurement of τ , unaffected by soil-structure interaction, can be obtained from impulse response functions, provided that the data are sufficiently broadband. This is an important result for structural health monitoring because it shows that structural parameters unaffected by soil-structure interaction ( τ , as well as f 1 for structures deforming primarily in shear) can be estimated from seismic monitoring data with minimum instrumentation (two horizontal sensors, one at the base and one at the top). This extends the usability of old strong-motion data in buildings, most of which have not been extensively instrumented, and lessons that can be learned for development and validation of structural health monitoring methodologies. The presented results correspond to a model of the north–south response of the Millikan Library in Pasadena, California, which has become a classical case study for soil-structure interaction.

Ground propagation of vibrations from railway vehicles using a finite/infinite-element model of the soil:

Abstract: The aim of this study is to investigate the generation and propagation of ground vibrations induced by railway traffic, more specifically in the case of urban vehicles. The complete vehicle–track–soil model is developed according to an uncoupled approach: the vehicle–track subsystem is first simulated so as to provide the ground forces which, in turn, are applied to the model of the soil. The vehicle–track model is built with the help of the home-made C++ library EasyDyn, dedicated to the simulation of mechanical systems and multi-body applications. The 3-D model of the soil is developed under the commercial finite element code ABAQUS. It consists of a half-sphere of classical elements surrounded by infinite elements in order to account for the unbounded nature of the ground. A particular procedure has been developed in order to properly mesh the domain, especially at the transition between finite and infinite elements. Special care is also taken on conditions with respect to the minimal size of the domain and the maximal element size. On the contrary of the approaches classically found in the literature, the simulation is performed in time domain in place of frequency domain. This choice appears to be more appropriate and more natural in the case of vibrations induced by localized discontinuities of the track, due to the transient nature of the process. Moreover, it is shown that conditions on the domain size can be relieved in the time domain without loss of accuracy. The approach is illustrated by the practical case of vibrations generated by a tramway coming up against rail discontinuities.The vibratory levels obtained with the finite–infinite model of the soil show a good agreement with experimental results.

Simplified BEM/FEM model for dynamic analysis of structures on piles and pile groups in viscoelastic and poroelastic soils

Abstract: A simplified model for the analysis of the dynamic response of structures on piles and pile groups under time harmonic excitation is presented in this paper. It is a coupled boundary element–finite element model able to take into account dynamic pile–soil–pile interaction in a rigorous manner. Piles and pile groups in viscoelastic or poroelastic soils are considered. Two-node cylindrical boundary elements are used to represent the interface between soil and pile. These elements are connected to beam-type finite elements representing the concrete pile which can be connected to a pile cap and to any superstructure modeled by beam elements. The model is rather simple: two-node beam elements along the pile are directly connected to the BE nodes along the soil hole, and the uppermost node to the soil surface and to the FE nodes of any superstructure. Thus, large structures founded on piles in viscoelastic or poroelastic soils can be represented using a reasonable number of unknowns. In order to validate the procedure, single piles and pile groups in viscoelastic and poroelastic soils are analyzed. The obtained results are compared with those obtained by other authors using more complex or less general approaches. There is a good agreement between the present results and those reported in the literature.

Assessment and modeling of embankment participation in the seismic response of integral abutment bridges

Abstract: The dynamic response and seismic performance of bridges may be appreciably affected by numerous contributing factors, with soil–structure interaction being the dominant exogenous influence. The most familiar form is the so-called soil–pile interaction, but embankment–abutment interaction is also documented through field observations and analytical investigations, particularly evident in integral R.C. bridges. Recent studies have shown that this form of interaction may significantly alter the bridge response and should be taken into account during design and assessment, especially in the case of typical highway overcrossings that have abutments supported on earth embankments. In light of this emerging problem and in order to facilitate quantitative estimates of the interaction effects, the question of appropriate modeling and seismic assessment of R.C. integral bridges is the main object of the present paper. Based on already established procedures to account for soil–structure interaction, a new approach is proposed to model the contribution of the embankment, the bent and the abutments to the overall bridge response. Furthermore, the capacity curve of the entire bridge system is evaluated through the implementation of Incremental Dynamic Analysis (IDA), therefore allowing for seismic assessment of the complex superstructure–foundation system with well established displacement based procedures. Using as a benchmark case two typical instrumented U.S. highway bridges located in California, the proposed method is implemented and provided results from this analysis are correlated successfully with available field data. Results obtained from the analysis indicate excessive displacement demands for the entire bridge–embankment system owing to the embankment contribution and the soil degradation under increasing shear strains. Furthermore, seismic performance is strongly related to the central bent deformation capacity, with soil–pile interaction effects being of critical importance.

The effect of foundation embedment on inelastic response of structures

Abstract: In this research, a parametric study is carried out on the effect of soil–structure interaction on the ductility and strength demand of buildings with embedded foundation. Both kinematic interaction (KI) and inertial interaction effects are considered. The sub-structure method is used in which the structure is modeled by a simplified single degree of freedom system with idealized bilinear behavior. Besides, the soil sub-structure is considered as a homogeneous half-space and is modeled by a discrete model based on the concept of cone models. The foundation is modeled as a rigid cylinder embedded in the soil with different embedment ratios. The soil–structure system is then analyzed subjected to a suit of 24 selected accelerograms recorded on alluvium deposits. An extensive parametric study is performed for a wide range of the introduced non-dimensional key parameters, which control the problem. It is concluded that foundation embedment may increase the structural demands for slender buildings especially for the case of relatively soft soils. However, the increase in ductility demands may not be significant for shallow foundations with embedment depth to radius of foundation ratios up to one. Comparing the results with and without inclusion of KI reveals that the rocking input motion due to KI plays the main role in this phenomenon. Copyright © 2008 John Wiley & Sons, Ltd.

Identification of dynamic models of a building structure using multiple earthquake records

Abstract: In this paper, a methodology is presented for the identification of state-space models of a building structure using time histories of the earthquake-induced ground motion and of the corresponding structural responses. From these identified models, modal parameters such as natural frequencies, damping ratios and mode shapes of the structural system can be easily retrieved. The identification methodology is based on the ERA/DC complemented by the OKID algorithm for the identification of the Markov's parameters of the system. Model order is determined using the stabilization diagram. Additional model refinement is performed through a nonlinear minimization of the output error between recorded and reconstructed responses. The building considered in this analysis has 29 accelerometers, located on the basement and at various elevation levels. Three of such accelerometers are placed directly on the ground outside the building and are considered representative of the free-field ground motion. Records of the ground acceleration and of the building response recorded during 10 aftershocks of the 1999 Chi-Chi (Taiwan) earthquake have been used, 9 of which for the identification phase and 1 (the latest aftershock) for validation of the prediction capabilities of the identified models. Different input conditions have been assumed to account for the effects of the flexibility of the foundation and for the soil–foundation–structure interaction. From the analysis of the results, it is concluded that the proposed methodology is quite effective in identifying the modal parameters of the structural system and in predicting its structural response for a future earthquake. Copyright © 2008 John Wiley & Sons, Ltd.

Numerical modeling of centrifuge cyclic lateral pile load experiments

Abstract: To gain insight into the inelastic behavior of piles, the response of a vertical pile embedded in dry sand and subjected to cyclic lateral loading was studied experimentally in centrifuge tests conducted in Laboratoire Central des Ponts et Chaussees. Three types of cyclic loading were applied, two asymmetric and one symmetric with respect to the unloaded pile. An approximately square-root variation of soil stiffness with depth was obtained from indirect in-flight density measurements, laboratory tests on reconstituted samples, and well-established empirical correlations. The tests were simulated using a cyclic nonlinear Winkler spring model, which describes the full range of inelastic phenomena, including separation and re-attachment of the pile from and to the soil. The model consists of three mathematical expressions capable of reproducing a wide variety of monotonic and cyclic experimental p-y curves. The physical meaning of key model parameters is graphically explained and related to soil behavior. Comparisons with the centrifuge test results demonstrate the general validity of the model and its ability to capture several features of pile-soil interaction, including: soil plastification at an early stage of loading, “pinching” behavior due to the formation of a relaxation zone around the upper part of the pile, and stiffness and strength changes due to cyclic loading. A comparison of the p-y curves derived from the test results and the proposed model, as well as those from the classical curves of Reese et al. (1974) for sand, is also presented.

A non‐linear coupled finite element–boundary element model for the prediction of vibrations due to vibratory and impact pile driving

Abstract: This paper presents a non-linear coupled finite element–boundary element approach for the prediction of free field vibrations due to vibratory and impact pile driving. Both the non-linear constitutive behavior of the soil in the vicinity of the pile and the dynamic interaction between the pile and the soil are accounted for. A subdomain approach is used, defining a generalized structure consisting of the pile and a bounded region of soil around the pile, and an unbounded exterior linear soil domain. The soil around the pile may exhibit non-linear constitutive behavior and is modelled with a time-domain finite element method. The dynamic stiffness matrix of the exterior unbounded soil domain is calculated using a boundary element formulation in the frequency domain based on a limited number of modes defined on the interface between the generalized structure and the unbounded soil. The soil–structure interaction forces are evaluated as a convolution of the displacement history and the soil flexibility matrices, which are obtained by an inverse Fourier transformation from the frequency to the time domain. This results in a hybrid frequency–time domain formulation of the non-linear dynamic soil–structure interaction problem, which is solved in the time domain using Newmark's time integration method; the interaction force time history is evaluated using the θ-scheme in order to obtain stable solutions. The proposed hybrid formulation is validated for linear problems of vibratory and impact pile driving, showing very good agreement with the results obtained with a frequency-domain solution. Linear predictions, however, overestimate the free field peak particle velocities as observed in reported field experiments during vibratory and impact pile driving at comparable levels of the transferred energy. This is mainly due to energy dissipation related to plastic deformations in the soil around the pile. Ground vibrations due to vibratory and impact pile driving are, therefore, also computed with a non-linear model where the soil is modelled as an isotropic elastic, perfectly plastic solid, which yields according to the Drucker–Prager failure criterion. This results in lower predicted free field vibrations with respect to linear predictions, which are also in much better agreement with experimental results recorded during vibratory and impact pile driving. Copyright © 2008 John Wiley & Sons, Ltd.

Long-Term Response Prediction of Integral Abutment Bridges

Abstract: The importance of long-term behavior in integral abutment (IA) bridges has long been recognized. This paper presents an analytical, long-term, response prediction methodology using finite-element (FE) models and compares results to measured response. Three instrumented Pennsylvania IA bridges have been continuously monitored since November 2002, November 2003, and September 2004 to capture bridge response. An evaluation of measured responses indicates that bridge movement progresses year to year with long-term response being significant with respect to static predictions. Both two-dimensional and three-dimensional FE models were developed using ANSYS to determine an efficient and accurate analysis level. Seasonal cyclic ambient temperature and equivalent temperature derived from time-dependent strains using the age adjusted effective modulus method were employed as major loads in all FE models. The elastoplastic p-y curve method, classical earth pressure theory, and moment-rotation relationships with parallel unloading paths were used to model hysteretic behavior of soil-pile interaction, soil-abutment interaction, and abutment-to-backwall connection. Predicted soil pressures obtained from all FE models are similar to the measured response. Predicted abutment displacements and corresponding design forces and moments at the end of the analytically simulated 100-year period indicate the significance of long-term behavior that should be considered in IA bridge design.

Dynamic Soil–Structure Interaction of Bridge Substructure Subject to Vessel Impact

Abstract: The paper describes the in situ investigation, site stratigraphy, field monitoring, data reduction, and subsequent time-domain analysis of soil–structure interaction from a full scale vessel impact loading of a bridge pier at the St. George Island Causeway. The in situ investigation included standard penetration testing, electric cone, dilatometer, and pressuremeter testing to identify soil stratigraphy, engineering properties (strength and moduli), and axial and lateral static pile resistance ( T–z , and P–y ). Field instrumentation included soil total stress and pore pressure gauges in front of and behind the pile cap, a fully instrumented pile (strain gauges along length), dynamic load cells to monitor barge impact loads, and accelerometers to monitor pier accelerations, velocities, and displacements. Analyses of the field data reveal significant dynamic forces within the soil–structure system as a result of the duration and magnitude of the loading. Inertia from the piers, cap, and piles provide signi...

Building frame-pile foundation-soil interactive analysis

Abstract: The effect of soil-structure interaction on a simple single storeyed and two bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the three dimensional finite element analysis with realistic assumptions. The members of the superstructure and substructure are descretized using 20 node isoparametric continuum elements while the interface between the soil and pile is modeled using 16 node isoparametric interface elements. Owing to viability in terms of computational resources and memory requirement, the approach of uncoupled analysis is generally preferred to coupled analysis of the system. However, an interactive analysis of the system is presented in this paper where the building frame and pile foundation are considered as a single compatible unit. This study is focused on the interaction between the pile cap and underlying soil. In the parametric study conducted using the coupled analysis, the effect of pile spacing in a pile group and configuration of the pile group is evaluated on the response of superstructure. The responses of the superstructure considered include the displacement at top of the frame and moments in the superstructure columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation used in the study. The percentage variation in the values of displacement obtained using the coupled and uncoupled analysis is found in the range of 4-17 and that for the moment in the range of 3-10. A reasonable agreement is observed in the results obtained using either approach.

Numerical Analysis of a Soil-Steel Bridge Structure

Abstract: This paper presents a numerical analysis of the soil-steel bridge which was also thoroughly tested under real field loads (during backfilling and under static loads). The comparison of results from calculations and field tests is also presented in the paper. Soil-steel structures are built mostly as bridges located on local roads, but also as railway viaducts, as highway bridges, as well as the ecological objects or tunnels (overpasses and underpasses for animals) in recent times. The technology of usage of flexible structures made from corrugated steel plates (CSP) is based on the interaction between shell and surrounding soil (backfill) and also takes into consideration the effect of loads arching in soil. The computation model with interface elements can be used to computer simulation of live loads in such type of bridges instead of extremely expensive and time-consuming experimental tests.

A new type of damper with friction-variable characteristics

Abstract: Professor T. T. Soong is one of the early pioneers in field of earthquake response control of structures. A new type of smart damper, which is based on an Energy Dissipating Restraint (EDR), is presented in this paper. The EDR by Nims and Kelly, which has a triangle hysteretic loop, behaves like an active variable stiffness system (AVS) and possesses the basic characteristics of a linear viscous damper but has difficulty in capturing the output and large stroke simultaneously needed for practical applicataions in engineering structures. In order to overcome this limitation, the friction surface in the original Sumitomo EDR is divided into two parts with low and high friction coefficients in this paper. The results of finite element analysis studies show that the new type of smart friction damper enables large friction force in proportion to relative displacement between two ends of the damper and has a large allowable displacement to fit the demands of engineering applications. However, unlike the EDR by Nims and Kelly, this type of friction variable damper cannot self re-center. However, the lateral stiffness can be used to restore the structure. The nonlinear time history analysis of earthquake response for a structure equipped with the proposed friction variable dampers was carried out using the IDARC computer program. The results indicate that the proposed damper can successfully reduce the earthquake response of a structure.

Dynamics of structure and foundation : a unified approach

Abstract: Preface 1 Dynamic soil structure interaction *1.1 Introduction *1.1.1 The marriage of soil and structure *1.1.2 What does the interaction mean? *1.1.3 It is an expensive analysis do we need to do it? *1.1.4 Different soil models and their coupling to superstructure *1.2 Mathematical modeling of soil & structure *1.2.1 Lagrangian formulation for 2D frames or stick-models *1.2.2 What happens if the raft is flexible? *1.3 A generalised model for dynamic soil structure interaction *1.3.1 Dynamic response of a structure with multi degree of freedom considering the underlying * soil stiffness *1.3.2 Extension of the above theory to system with multi degree of freedom *1.3.3 Estimation of damping ratio for the soil structure system *1.3.4 Formulation of damping ratio for single degree of freedom *1.3.5 Extension of the above theory to systems with multi-degree freedom *1.3.6 Some fallacies in coupling of soil and structure *1.3.7 What makes the structural response attenuate or amplify? *1.4 The art of modelling *1.4.1 Some modelling techniques *1.4.2 To sum it up *1.5 Geotechnical considerations for dynamic soil structure interaction *1.5.1 What parameters do I look for in the soil report? *1.6 Field tests *1.6.1 Block vibration test *1.6.2 Seismic cross hole test *1.6.3 How do I co-relate dynamic shear modulus when I do not have data from the dynamic * soil tests? *1.7 Theoretical co-relation from other soil parameters *1.7.1 Co-relation for sandy and gravelly soil *1.7.2 Co-relation for saturated clay *1.8 Estimation of material damping of soil *1.8.1 Whitman's formula *1.8.2 Hardin' formula *1.8.3 Ishibashi and Zhang's formula *1.9 All things said and done how do we estimate the strain in soil, specially if the strain is large? *1.9.1 Estimation of strain in soil for machine foundation *1.9.2 Estimation of soil strain for earthquake analysis *1.9.3 What do we do if the soil is layered with varying soil property? *1.9.4 Checklist of parameters to be looked in the soil reports *1.10 Epilogue 2. Analysis and design of machine foundations *2.1 Introduction *2.1.1 Case history #1 *2.1.2 Case history #2 *2.2 Different types of foundations *2.2.1 Block foundations resting on soil/piles *2.2.2 How does a block foundation supporting rotating machines differ from a normal * foundation? *2.2.3 Foundation for centrifugal or rotary type of machine: Different theoretical methods * for analysis of block foundation *2.2.4 Analytical methods *2.2.5 Approximate analysis to de-couple equations with non-proportional damping *2.2.6 Alternative formulation of coupled equation of motion for sliding and rocking mode *2.3 Trick to by pass damping - Magnification factor, the key to the problem *2.4 Effect of embedment on foundation *2.4.1 Novak and Beredugo's model *2.4.2 Wolf's model *2.5 Foundation supported on piles *2.5.1 Pile and soil modelled as finite element *2.5.2 Piles modelled as beams supported on elastic springs *2.5.3 Novak's (1974) model for equivalent spring stiffness for piles 1 *2.5.4 Equivalent pile springs in vertical direction *2.5.5 The group effect on the vertical spring and damping value of the piles *2.5.6 Effect of pile cap on the spring and damping stiffness *2.5.7 Equivalent pile springs and damping in the horizontal direction *2.5.8 Equivalent pile springs and damping in rocking motion *2.5.9 Group effect for rotational motion *2.5.10 Model for dynamic response of pile *2.5.11 Dynamic analysis of laterally loaded piles *2.5.12 Partially embedded piles under rocking mode *2.5.13 Group effect of pile *2.5.14 Comparison of results *2.5.15 Practical aspects of design of machine foundations *2.6 Special provisions of IS-code *2.6.1 Recommendations on vibration isolation *2.6.2 Frequency separation *2.6.3 Permissible amplitudes *2.6.4 Permissible stresses *2.6.5 Concrete and its placing *2.6.6 Reinforcements *2.6.7 Cover to concrete *2.7 Analysis and design of machine foundation under impact loading *2.7.1 Introduction *2.7.2 Mathematical model of a hammer foundation *2.8 Design of hammer foundation *2.8.1 Design criteria for hammer foundation *2.8.2 Discussion on the IS-code method of analysis *2.8.3 Check list for analysis of hammer foundation *2.8.4 Other techniques of analysis of Hammer foundation *2.9 Design of eccentrically loaded hammer foundation *2.9.1 Mathematical formulation of anvil placed eccentrically on a foundation *2.9.2 Damped equation of motion with eccentric anvil *2.10 Details of design *2.10.1 Reinforcement detailing *2.10.2 Construction procedure *2.11 Vibration measuring instruments *2.11.1 Some background on vibration measuring instruments and their application *2.11.2 Response due to motion of the support *2.11.3 Vibration pick-ups *2.12 Evaluation of friction damping from energy consideration *2.13 Vibration isolation *2.13.1 Active isolation *2.13.2 Passive isolation *2.13.3 Isolation by trench *2.14 Machine foundation supported on frames *2.14.1 Introduction *2.14.2 Different types of turbines and the generation process *2.14.3 Layout planning *2.14.4 Vibration analysis of turbine foundations *2.15 Dynamic soil-structure interaction model for vibration analysis of turbine foundation *2.16 Computer analysis of turbine foundation based on multi degree of freedom *2.17 Analysis of turbine foundation *2.17.1 The analysis *2.17.2 Calculation of the eigen values *2.17.3 So the ground rule is *2.17.4 Calculation of amplitude *2.17.5 Calculation of moments, shears and torsion *2.17.6 Practical aspects of design of Turbine foundation *2.18 Design of turbine foundation *2.18.1 Check list for turbine foundation design *2.18.2 Spring mounted turbine foundation 3. Analytical and design concepts for earthquake engineering *3.1 Introduction *3.1.1 Why do earthquakes happen in nature? *3.1.2 Essential difference between systems subjected to earthquake and vibration from machine *3.1.3 Some history of major earthquakes around the world *3.1.4 Intensity *3.1.5 Effect of earthquake on soil-foundation system *3.1.6 Liquefaction analysis *3.2 Earthquake analysis *3.2.1 Seismic coefficient method *3.2.2 Response spectrum method *3.2.3 Dynamic analysis under earthquake loading *3.2.4 How do we evaluate the earthquake force? *3.2.5 Earthquake analysis of systems with multidegree of freedom *3.2.6 Modal combination of forces *3.3 Time history analysis under earthquake force *3.3.1 Earthquake analysis of tall chimneys and stack like structure *3.4 Analysis of concrete dams *3.4.1 Earthquake analysis of concrete dam *3.4.2 A method for dynamic analysis of concrete dam *3.5 Analysis of earth dams and embankments *3.5.1 Dynamic earthquake analysis of earth dams *3.5.2 Mononobe's method for analysis of earth dam *3.5.3 Gazetas' method for earth dam analysis *3.5.4 Makadisi and Seed's method for analysis of earth dam *3.5.5 Calculation of seismic force in dam and its stability *3.6 Analysis of earth retaining structures *3.6.1 Earthquake analysis of earth retaining structures *3.6.2 Mononobe's method of analysis of retaining wall *3.6.3 Seed and Whitman's method *3.6.4 Arango's method *3.6.5 Steedman and Zeng's method *3.6.6 Dynamic analysis of RCC retaining wall *3.6.7 Dynamic analysis of cantilever and counterfort retaining wall *3.6.8 Some discussions on the above method *3.6.9 Extension to the generic case of soil at a slope i behind the wall *3.6.10 Dynamic analysis of counterfort retaining wall *3.6.11 Soil sloped at an angle i with horizontal *3.7 Unyielding earth retaining structures *3.7.1 Earthquake Analysis of rigid walls when the soil does not yield *3.7.2 Ostadan's method *3.8 Earthquake analysis of water tanks *3.8.1 Analysis of water tanks under earthquake force *3.8.2 Impulsive time period for non rigid walls *3.8.3 Sloshing time period of the vibrating fluid *3.8.4 Calculation of horizontal seismic force for tank resting on ground *3.8.5 Calculation of base shear for tanks resting on ground *3.8.6 Calculation of bending moment on the tank wall resting on the ground *3.8.7 Calculation of hydrodynamic pressure *3.9 Mathematical model for overhead tanks under earthquake *3.9.1 Earthquake Analysis for overhead tanks *3.9.2 Hydrodynamic pressure on tank wall and base *3.9.3 Hydrodynamic pressure for circular tank *3.9.4 Hydrodynamic pressure for rectangular tank *3.9.5 Effect of vertical ground acceleration *3.9.6 Pressure due to inertia of the wall *3.9.7 Maximum design dynamic pressure *3.10 Practical aspects of earthquake engineering *3.10.1 Epilogue References Subject index

Deformation Factors of Buried Corrugated Structures

Abstract: Buried corrugated structures are subjected to highest stresses during two phases: during backfilling and under service loads. Commonly, deformations during backfilling are more unfavorable for the structure than those that occur under service loads. Typically, service loads will generate several times less deflection than do construction loads falling below the limit of deflection (w) to span (L) of w/L =2%. For the sake of modeling the behavior of corrugated steel structures during backfilling, separate components (i.e., corrugated steel, backfill, road structure) of the soil structure are represented by independent parameters such as deformation module, Poisson's coefficient, and soil unit weight. A steel plate is described in geometric terms. Modeling the deformation of buried corrugated structures with finite element modeling is very difficult because of the complex characteristics of the soil medium during construction of the backfill. An analytical algorithm was used to calculate characteristic defo...

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

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

Seismic History Analysis of Asymmetric Buildings with Soil-Structure Interaction

Abstract: An efficient approximate method that uses the multi-degrees-of-freedom (MDOF) modal equations of motion for the seismic response history analysis of asymmetric elastic buildings with soil–structure interaction (SSI) is presented in this paper. The systems considered are two-way asymmetric shear buildings resting on the surface of an elastic half-space, which are excited by two-directional seismic ground motions. The SSI forces were simulated using frequency-independent soil springs and dashpots. First, the MDOF modal equations of motion for the SSI systems were derived. The modal response histories were obtained by solving the MDOF modal equations of motion using the step-by-step integration method. Subsequently, the seismic response histories of the whole SSI system were determined from the arithmetic summation of the modal response histories. The MDOF modal equations of motion retain the property of nonproportional damping of the original SSI system. The proposed method has the advantages of the convent...