Showing papers on "Soil structure interaction published in 1994"

Design of piled bridge abutments on soft clay for loading from lateral soil movements

Abstract: Piles supporting bridge abutments on soft clay may be loaded laterally from horizontal soil movements generated by the approach embankment. The design of piles loaded by lateral soil movements is problematic in that existing design approaches are generally inconsistent or show poor correlation with available data. New empirical design charts are presented to allow an assessment of maximum pile bending moment and pile head deflection based on the relative soil-pile stiffness and current loading level. A new analytical approach is also developed on the basis of a simple deformation mechanism. The method accounts for the main features of the problem through an approximate representation of the embankment-soil-pile interaction, and is shown to compare favourably with centrifuge model test data. Recommendations for the design of pile groups for loading from lateral soil movements are also given. Les mouvements horizontaux du sol crees par le remblai sont susceptibles d'engendrer des contraintes laterales dans ...

Non‐Linear Model for Dynamic Axial Pile Response

Abstract: An analysis of pile axial response to transient dynamic loading and to harmonic loading is presented allowing for nonlinear soil behavior, energy dissipation through radiation damping, soil hystere...

Dynamic modeling and response of soil-wall systems

Abstract: Following a brief review of the inaccuracies that may result from the use of a popular model for evaluating the dynamic soil pressures and associated forces induced by ground shaking in a rigid wall retaining an elastic stratum, the sources of the inaccuracies are identified and a modification is proposed which, while retaining the attractiveness of the original model, defines correctly the action of the system. In the proposed modification, the soil stratum is modeled by a series of elastically supported, semiinfinite horizontal bars with distributed mass rather than by massless springs. The concepts involved are introduced by reference to a fixed-based wall retaining a homogeneous elastic stratum, and are then applied to the analysis of more complex soil-wall systems. Both harmonic and transient excitations are considered, and comprehensive numerical solutions are presented that elucidate the actions of the systems examined, and the effects and relative importance of the numerous parameters involved.

Prediction of Observed Bridge Response with Soil-Pile–Structure Interaction

Abstract: A simple integrated procedure to analyze the problem of soil‐pile‐foundation‐superstructure interaction is presented. The procedure combines the available theories for the computation of the dynamic impedances and kinematic‐seismic response factors of pile foundations with a simple six‐degree‐of‐freedom structural model. The procedure is used to predict the response of the Painter Street Bridge located at Rio Dell, California, which was excited by the 1992 Petrolia earthquake. The predicted response with the proposed procedure is in very good agreement with recorded data, and the significance of considering the frequency dependent pile‐foundation impedances in predicting the superstructure response is demonstrated.

Effect of flexibility on impedance functions for circular foundation

Abstract: This paper investigates the effect of foundation rigidity on impedance functions for a circular foundation on a viscoelastic soil medium. In addition to vertical and rocking impedances, the paper also investigates the influence on coupling impedance for horizontal and rocking motions of foundation and horizontal impedance. To generate impedance functions for flexible foundation, a substructure technique is used. For the substructure of the flexible foundation, classical plate theory with neglecting inertial force is employed to obtain the deformation of the foundation due to the interaction stress. For the substructure of the soil medium, the technique, which can deal with wave equations in cylindrical coordinates with arbitrarily prescribed boundary conditions, is employed to obtain the displacement field in the soil medium due to the interaction stresses. Then, with the help of the variational principle, the displacement continuity condition of both substructures is imposed to generate the impedances fo...

Nonlinear Lateral, Rocking, and Torsional Vibration of Rigid Foundations

Abstract: Two- and three-dimensional finite element (FE) analyses are performed to investigate the influence of nonlinear soil behavior on the dynamic response of harmonically excited rigid foundations. Lateral, rocking, and torsional vibration modes are considered. An elasto-viscoplastic constitutive model with kinematic hardening is assumed for the foundation soil, and computations are done implicitly in the time domain. The foundation responses for lateral, rocking, and torsional modes are characterized by increased vibrational amplitudes due to material stiffness degradation. Furthermore, resonance frequencies are created that resemble those observed for vertically oscillating finite-size foundations. Nonlinear soil effects are shown to be dominant over a wide range of excitation frequencies for foundations vibrating in torsional and lateral modes. In contrast, nonlinear soil effects are shown to be dominant over a much narrower range of excitation frequencies for the rocking mode. The methodology presented in this paper is useful for nonlinear vibration and transient soil-structure interaction (SSI) analysis.

Nonlinear soil‐structure interaction in plane frames

Abstract: Study of soil‐structure interaction effect in framed structures necessitates proper physical modelling of the structure, foundation and the soil mass. At the same time, the stress—strain model used for the constitutive relationship of the soil mass must also be realistic. In the present study, a hyperbolic stress—strain model has been used to consider the soil non‐linearity. The interactive behaviour of a five storey, two bay plane frame has been studied in detail and the results are compared with those obtained from a conventional and a linear interactive analysis.

Predicted Behavior of Two Centrifugal Model Soil Walls

Abstract: The finite element method is used to predict the behavior of two centrifugal reinforced soil wall models, one reinforced with a geogrid, the other with a nonwoven geotextile. Comparisons between the observed and calculated behavior indicate good agreement. Sensitivity studies were also performed in order to investigate some of the uncertainties adopted in the numerical modeling. These studies show that in the geotextile‐reinforced model the effect of the intermediate layers that form part of the wrap‐back facing is significant. In the geogrid‐reinforced model, it is found that the interface shear strength between the fill and the reinforcement is an important factor, but the effects of the fill/facing interface shear strength, facing panel continuity, and location of panel connections are relatively less important. The finite element analyses also provide detailed information relating to the soil/structure interaction in these models. The results presented in this paper are considered to be useful in adva...

Soil-Structure Interaction: Numerical Analysis and Modelling

Abstract: This book describes how a number of different methods of analysis and modelling, including the boundary element method, the finite element method, and a range of classical methods, are used to answer some of the questions associated with soil-structure interaction.

Nonlinear model for building-soil systems

Abstract: A finite-element based, numerical analysis methodology has been developed for the nonlinear analysis of building-soil systems. The methodology utilizes a reduced-order, nonlinear continuum model to represent the building, and the soil is represented with a simple nonlinear two-dimensional plane strain finite element. The foundation of the building is idealized as a rigid block and the interface between the soil and the foundation is modeled with an interface contract element. The objectives of the current paper are to provide the theoretical development of the system model, with particular emphasis on the modeling of the foundation-soil contact, and to demonstrate the special-purpose finite-element program that has been developed for nonlinear analysis of the building-soil system. Examples are included that compare the results obtained with the special-purpose program with the results of a general-purpose nonlinear finite-element program.

Analytical modeling of spread footing foundations for seismic analysis of bridges

Abstract: The way bridges respond to seismic excitation may be significantly influenced by the dynamic properties of their foundations. Within current design practice, foundation elements typically are considered as elastic springs, without consideration to material and radiation damping. General foundation models are identified that are suitable for (a) modeling soil-structure interaction for the seismic analysis of bridges, (b) modifying an existing, nonlinear, seismic-bridge-analysis computer program to include a new element capable of representing such models, and (c) conducting a parametric study to assess the effect of the increased energy dissipation mechanisms on the seismic response of bridge substructures. Three different models for spread-footing foundations are identified, applied to a typical two-column bridge bent, and compared with conventional elastic and fixed-base models. Three soil-stiffness values are considered, and two earthquake records, each with two different intensities, were applied to the bent. Maximum values of displacement, plastic-hinge rotation, and cumulative plastic hinge rotations were noted and compared. It was concluded that the use of the spread-footing foundation models can produce an important change in the bridge response to seismic activity when compared with that of the fixed-base model--depending on the frequency content of the earthquake and the stiffness of the soil. The effects of radiation damping were observed to be insignificant for foundations on stiff soil but important for those on soft soil. In addition, the performance of the simpler, damped foundation models was found to be quite similar to that of the more complex models. The models' accuracy was not verified, but the structural response of incorporating them was explored.

Dynamic stability of non-linear shells of revolution under consideration of the fluid-soil-structure interaction

Abstract: The dynamic behaviour of liquid-filled shells of revolution is investigated considering the soil-structure interaction and the fluid--structure interaction, respectively. In the circumferential direction the loads and variables are approximated by Fourier series. The shell is modelled through shell ring elements including non-linear behaviour, coupled with isoparametric continuum ring elements and special infinite elements for the soil and isoparametric pressure ring elements for the fluid. Transient loadings like earthquake excitation and the non-linearities of the shell and the soil require an analysis in the time domain. To reduce the size of the problem, linear parts of the system are condensed by the substructure technique

Explicit stresses under rectangular footings

Abstract: The calculation of stresses under rectangular footings with biaxial bending is carried out by solving the three-equations system that sets up the load and soil stresses equilibrium. When a planar soil stresses distribution is assumed, and the area is in full compression, the just mentioned system is linear and its solution immediate. With increasing eccentricities, some corners of the footing can get detached from the soil, the system becoming nonlinear, and difficulties arise in its resolution. In the paper an analytical alternative to the numerical and graphical solutions is presented, which will lead to obtaining explicit solutions for these stresses and neutral axis location.

Centrifuge modeling of laterally loaded pipelines

Abstract: The state of practice (SOP) for pipeline design in areas where pipelines may move relative to the soil involves considering the pipeline to be made up of discrete segments and the segments to be coupled to the soil via a set of spring/sliders. Much of the theory behind this SOP is derived from other geotechnical applications such as pile/soil interaction. There is little or no physical verification of the mechanisms or the magnitude of forces assumed during pipeline displacement. An experimental model examination of displaced pipelines using the centrifuge modeling technique to create similitude between model and prototype or the actual situation is presented. The SOP, the experimental program, and the results of eight pipeline model tests are presented. The results are discussed, with particular reference to the magnitude of loads transmitted to the pipes and the development of the pipeline/soil interaction. The test results are compared with the loads that would be predicted by the SOP design calculations. The main conclusion is that the SOP formulation appears to be unconservative, predicting loads acting on the pipeline about 50% lower than those measured experimentally.

Dynamic Soil-Structure Interaction Analysis by a Hybrid Method*

Abstract: In this paper, the dynamic interaction between soil and a cooling tower is analysed using a hybrid method that combines a finite element method and a boundary element method. The dynamic behavior of the soil half-space is investigated in detail. The effect of soil-structure interaction on the gust responses of draught column-supported hyperbolic cooling towers is estimated, and a comparison is made between these numerical results and their counterparts obtained under a full-scale test.

Soil-structure interaction analysis of embedded caisson anchor under tension load

Abstract: Capped structural cylinders, vertically embedded in the seafloor, may provide tension capacity for anchorage and bearing capacity for offshore structures. The capacity of such "inverted buckets" to resist combinations of static and cyclic loads may be predicted by reliable computational procedures. This has been demonstrated by model tests and field performance observations. The emphasis in this paper is on the soil-structure interaction and the determination of contact stresses between the embedded cylinder and the inside and outside soil. These stresses are required for the structural design. A 3-dimensional finite element program is used to analyze a one- cylinder unit embedded in soft clay. The anchor is subjected to a cyclic live load corresponding to that for a tension leg platform. In addition to the magnitude and distribution of the control stresses, the results of the analyses show how the anchor pull is shared among the four different kinds of load carrying mechanisms, (1) vertical underpressure under the cylinder top cap, (2) inside and (3) outside shear along the skirt walls, and (4) underpressure under the skirt tip circumference. The load sharing varies with the applied tension load level due to the non-linear soil behaviour, and it is very sensitive to the assumed bulk modulus (or Poisson's ratio) for the undrained soil.

Analytical modeling of foundations for seismic analysis of bridges. final report

Abstract: The response of bridges when subjected to seismic excitation may be significantly influenced by the dynamic properties of their foundations. With current design practice, foundation elements are typically considered as elastic springs without consideration of material and radiation damping. The objectives of this research were to identify general foundation models that are suitable for modeling soil-structure interaction in seismic bridge analysis, to modify an existing nonlinear seismic bridge analysis computer program to include a new element capable of representing such models, and to conduct a parametric study to assess the effect of the increased energy dissipation mechanisms on the response of bridge substructures. For spread footing foundations, three different models were identified and applied to a typical two-column bridge bent. For pile foundations, four models were derived and applied to a five-column bent. The seismic response for each model was compared with conventional elastic and fixed-base models. Several soil stiffness values and earthquake records were considered for analysis. Maximum values of displacement, plastic hinge rotation, and cumulative plastic hinge rotations were noted and compared. It was concluded that the use of the foundation models can produce an important change in the bridge response when compared to that of the fixed-base model, depending on the frequency content of the earthquake and the stiffness of the soil. The effects of radiation damping were observed to be insignificant for foundations on stiff soil, but important for those on soft soil. In addition, the performance of the simpler damped foundation models was found to be quite similar to that of the more complex models.

Soil-structure interaction during preloading of jackup modu's in different soil conditions

Abstract: A new procedure to assess foundation stability of independent leg jackup drilling units during preloading is presented. This procedure allows assessment of the potential for rapid leg penetrations, taking into account changes ins spud can loads due to increase in ballast and shifting of centre of gravity.

User's guide for the incremental construction, soil-structure interaction program SOILSTRUCT with far-field boundary elements

Abstract: This report describes the computer program SOILSTRUCT, a two-dimensional, plane strain, finite element program used in the incremental construction, soil-structure interaction analysis of earth retaining structures. The initial version of the program was developed by Professors G.W. Clough and J.M. Duncan (1969) for use in the analysis of Port Allen and Old River U-frame locks. The program has been enhanced over the last 20 years by Professor Clough and coworkers. In this version of SOILSTRUCT, a substructure method for coupling the boundary element method (BEM) with the finite element method (FEM) is incorporated in order to solve soil-structure interaction problems more accurately and efficiently so that the nonlinear effects can be included in the near field by FEM, while the far field is simulated by BEM. Linear boundary elements based on the Melan fundamental solution are coupled with the QM5 finite elements. SOILSTRUCT has the capability to simulate incremental construction which may include embankment construction or backfilling, dewatering, excavation, installation of a strut or tie back anchor support system, removal of the same system, and the placement of concrete or other construction material. In addition, SOILSTRUCT has the capability to include the modeling of the interface region between the soil backfill and the structure, using interface elements.

Soil-Structure Interaction During Mining Induced Ground Movements

Abstract: Mining induced subsidence can result in significant ground deformation, which is generally non-uniform. Although this deformation occurs slowly with small inertial forces, it often results in substantial damage to residential and light commercial structures. To observe the response of residential foundations due to subsidence deformations, a series of instrumented test foundations was constructed over a longwall coal panel in southern Illinois. The response of both the free-field ground away from the structures, as well as the footings and masonry walls, was monitored prior to, during, and after the passing of the subsidence wave. Overall, the foundations settled nearly 1.5 m, most of which occurred during a 2 week period. For a given specific free-field location, the surface deformed in a cyclic manner, with an initial tensile phase, followed by a compressive phase, and a return to a near zero strain state as the wave passed by. However, the structure experienced a period of tension, followed by a period of compression, and was left in a state of residual tension. Measured horizontal strains in the footing were significantly smaller than those recorded in the free-field ground. This difference in deformation history implies that soil structure interaction effects are present, and suggests the inelastic response of the soil during the cyclic loading affects the structural response.

Vertical and Horizontal Deformations for Foundations on Sand: An Experimental Study

Abstract: A natural scale model is used in order to investigate experimentally the sand soil deformation behavior which accepts loads by shallow foundations. The vertical and horizontal soil displacements were measured. The vertical strains and the footing settlements are broken down into two components: a component due to the reduction of the soil voids and a component due to soil constant volume deformation. The investigation results are presented and evaluated critically.

Earthquake analysis and response of two-level viaducts

Abstract: The nonlinear effects of opening and closing of hinges, restrainers, and abutments must be included in the earthquake analysis of viaducts. In this study, the inelastic system response is compared with the elastic response for comparing the force overstrength ratios with the ductility demands of the viaducts. The parameter study of a typical two-level viaduct shows that the opening and closing of hinges produce discontinuities which alter the system response. The response of viaducts on non-uniform soil site shows that the frames on a stiff soil site provide restraint to the frames on soft soil site, whereas the frames on soft soil site amplify the response of frames on stiff soil site. Upper and lower bound models are established for viaducts subjected to uniform ground motion. The cases investigated demonstrate that it is advisable to perform nonlinear earthquake analysis to estimate the ductility demands in the viaducts. It is important to consider the effects of non-uniform ground motion, particularly for a low velocity ground wave propagation velocity or for the viaducts with significantly different soil profiles at the column supports of adjacent frames.

Implications of soil–structure interaction effects on the NBCC 1990 base shear provisions for high-rise buildings

Abstract: This study is carried out on a site-specific basis for three locations in Canada, namely Ottawa, Vancouver, and Prince Rupert. Soil models are developed to correspond to the soil classifications used to define the foundation factor, F, in the 1990 edition of the National Building Code of Canada (NBCC). Structural models are developed to represent both 20-storey ductile moment-resisting frames and ductile flexural walls. Three initial sets of actual ground motion records are scaled, in the frequency domain, to represent the postulated bedrock motions for each of the three sites. The computer program FLUSH is used to perform the numerical analyses of the various soil–structure systems. Results from the current study indicate that the code F values generally underestimate the site effects associated with the respective soil deposits, but appear to be reasonably adequate, in most cases, when soil–structure interaction effects are taken into consideration. In spite of some deficiencies in the code F values, th...