Showing papers on "Soil structure interaction published in 1982"

Seismic response of end-bearing piles

Abstract: A very simple analysis of dynamic soil-pile-supported mass interaction is presented as an aid to understanding pile foundations behaviour during earthquakes. The equilibrium equations of the soil and pile movements during seismic motions are established and the response of the soil-pile system is obtained as a function of the existing frequency; for simplicity the analysis was based on Winkler's model although the same procedure can be applied using a more refined model. The effect of the supported mass is studied, the natural frequency of the system is obtained, and some practical design considerations are presented. A method for considering group effects is also presented.

Three-dimensional hybrid modelling of soil-structure interaction

Abstract: A three-dimensional hybrid model for the analysis of soil-structure interaction under dynamic conditions is developed which takes advantage of the desirable features of the finite element and substructure methods and which minimizes their undesirable features. The modelling is achieved by partitioning the total soil-structure system into a near-field and a far-field with a hemispherical interface. The near-field, which consists of the structure to be analysed and a finite region of soil around it, is modelled by finite elements. The semi-infinite far-field is modelled by distributed impedance functions at the interface which are determined by system identification methods. Numerical results indicate that the proposed model makes possible realistic and economical assessment of three-dimensional soil-structure interaction for both surface and embedded structures.

Mechanics of Three-Dimensional Soil-Structure Interaction

Abstract: A finite element procedure for the general problem of three-dimensional soil-structure interaction involving nonlinearities caused by material behavior, geometrical changes, and interface behavior is presented. The formulation is based on the updated Lagrangian or approximate Eulerian approach with appropriate provision for constitutive laws. Consideration is given to the mathematical and experimental aspects related to the important topic of development and adoption of a constitutive law for the geologic medium. development and use of an interface element to describe the three-dimensional interface behavior are described. The influence of cracking and tensile stress conditions in the soil and interfaces is allowed for by using the stress transfer approach. The procedure is verified by comparing predictions with observation of a structure (tool) pushed in the soil in a special soil-bin test facility.

Performance and analysis of a long-span culvert

Abstract: A low-profile-arch long-span corrugated-steel culvert was installed in Pennsylvania as a bridge-replacement structure. The Republic Steel Company maxispan design was used. Instrumentation was installed in the soil and on the structure to monitor performance during construction. Field and laboratory soil property tests were conducted to characterize the soil behavior. Predictions from finite-element computer analyses were compared with the field results. From this and previous research, a number of conclusions were drawn. The choice of soil model had its most significant influence on the culvert deformation and bending-stress predictions. Overburden-dependent and linear-elastic soil models were shown to be unsatisfactory. Effects of construction procedures are difficult to predict accurately. Further study is needed to evaluate the importance of factors such as compaction-induced deformation, soil-culvert interface conditions, culvert wall yielding, and wall buckling. Seam slip rather than bending flexibility is needed to develop positive arching and hence further study is warranted. A particularly important observation was that special features like compaction wings appear to be both unnecessary and undesirable. (Author)

Predicting performance of buried conduits

Abstract: The capabilities of finite element computer codes FINLIN, CANDE, SSTIP and NLSSIP were evaluated CANDE was judged to be the best over-all code for predicting performance of buried conduits A number of improvements to this code were made Example solutions are given to illustrate the effects of conduit stiffness, interface slippage, and soil properties on conduit performance It was found that conventional concepts of soil "arching" are misleading; that slippage at the soil-conduit interface strongly affect the response; and that soil behavior plays the most crucial role in conntrolling performance It was concluded that the Duncan-Chang hyperbolic model is a satisfactory representation of nonlinear soil behavior for routine studies of conduit response Further use of equivalent elastic, overburden dependent, or default values in the extended Hardin soil models is not recommended For prediction purposes, especially to investigate the effects of soil compaction and of localized shear failures, a plasticity model of soil behavior is needed Duncan's (1979) SCI procedure for design of long-span metal culverts with shallow cover was also investigated The procedure provided good estimations of maximum thrust for the problems investigated in this study; however, agreement in both the magnitude of the bending moment and in the form of the bending moment equation was found to be poor, and the proposed safety factor to guard against plastic hinging in the conduit wall is considered to be overly conservative (FHWA)

Nonlinear Pile Behavior in Integral Abutment Bridges: Part 1

Abstract: The highway departments of all fifty states were contacted to find the extent of application of integral abutment bridges, to survey the different guidelines used for analysis and design of integral abutment bridges, and to assess the performance of such bridges through the years. The variation in design assumptions and length limitations among the various states in their approach to the use of integral abutments is discussed. The problems associated with lateral displacements at the abutment, and the solutions developed by the different states for most of the ill effects of abutment movements are summarized in the report. An algorithm based on a state-of-the-art nonlinear finite element procedure was developed and used to study piling stresses and pile-soil interaction in integral abutment bridges. The finite element idealization consists of beam-column elements with geometric and material nonlinearities for the pile and nonlinear springs for the soil. An idealized soil model (modified Ramberg-Osgood model) was introduced in this investigation to obtain the tangent stiffness of the nonlinear spring elements. Several numerical examples are presented in order to establish the reliability of the finite element model and the computer software developed. Three problems with analytical solutions were first solved and compared with theoretical solutions. A 40 ft H pile (HP 10 X 42) in six typical Iowa soils was then analyzed by first applying a horizontal displacement (to simulate bridge motion) and no rotation at the top and then applying a vertical load V incrementally until failure occurred. Based on the numerical results, the failure mechanisms were generalized to be of two types: (a) lateral type failure and (b) vertical type failure. It appears that most piles in Iowa soils (sand, soft clay and stiff clay) failed when the applied vertical load reached the ultimate soil frictional resistance (vertical type failure). In very stiff clays, however, the lateral type failure occurs before vertical type failure because the soil is sufficiently stiff to force a plastic hinge to form in the pile as the specified lateral displacement is applied. Preliminary results from this investigation showed that the vertical load-carrying capacity of H piles is not significantly affected by lateral displacements of 2 inches in soft clay, stiff clay, loose sand, medium sand and dense sand. However, in very stiff clay (average blow count of 50 from standard penetration tests), it was found that the vertical load carrying capacity of the H pile is reduced by about 50 percent for 2 inches of lateral displacement and by about 20 percent for lateral displacement of 1 inch. On the basis of the preliminary results of this investigation, the 265-feet length limitation in Iowa for integral abutment concrete bridges appears to be very conservative.

Uncertainty in soil-structure interaction analysis arising from differences in analytical techniques

Abstract: This study addresses uncertainties arising from variations in different modeling approaches to soil-structure interaction of massive structures at a nuclear power plant. To perform a comprehensive systems analysis, it is necessary to quantify, for each phase of the traditional analysis procedure, both the realistic seismic response and the uncertainties associated with them. In this study two linear soil-structure interaction techniques were used to analyze the Zion, Illinois nuclear power plant: a direct method using the FLUSH computer program and a substructure approach using the CLASSI family of computer programs. In-structure response from two earthquakes, one real and one synthetic, was compared. Structure configurations from relatively simple to complicated multi-structure cases were analyzed. The resulting variations help quantify uncertainty in structure response due to analysis procedures.

Effects of frictional slippage of soil-structure interfaces of buried culverts (abridgment)

Abstract: A simple friction-contact interface element is used to simulate frictional slippage, separation, and rebonding along a soil-structure interface. The application is to a long-span buried culvert with incremental soil layering and it is solved by the finite-element method. It is concluded that interface elements, which permit relative slippage between soil and structure, are necessary in order that the predicted structure deformations conform with experimental data. (Author)

Simplified Dynamic Analysis of Buildings with Basements

Abstract: The effects of basements on the dynamic soil-structure interaction of buildings are investigated and simplified models in which each interaction force is represented by a set of spring and dashpot in parallel are proposed. The frequency independent stiffness and damping coefficients to be used in the simplified models are obtained from transient analyses by comparing the average work done and the average rate of energy dissipated by the interaction forces in a more accurate lumped parameter model and the simplified model. To take into account the inertial resistance of the soil against the basement walls, virtual masses are added to the basement floors to obtain more accurate shear forces acting on the flexible basement columns. Using the proposed simplified models, the influence of the number of basements on the structure-foundation system is investigated.

Seismic Site and Soil-Structure Interaction Analysis

Abstract: The relationship between free-field motions and interaction motions is discussed. Conclusions are reached regarding the likely spatial and temporal variations of free-field motions at shallow depth. Several finite element methods for soil-structure analysis are discussed including the Flexible Volume Method. This method, which employs substructuring, makes it possible to obtain solutions to a broad range of three-dimensional soilstructure and structure-soil-structure interaction problems.

Response of corrugated-metal arches to soil loads

Abstract: To enable prediction of the response of systems with corrugated-metal arches and compacted soil bridges to soil loading above crown level, graphs were developed from a large number of finite-element analyses. The graphs are based on analysis of a flexible arch in the form of a half ellipse supported on either side by typical footings. They facilitate prediction of response parameters as the fill is placed and compacted in layers above the crown level. The material surrounding the arch is considered homogenous in terms of elastic modulus and Poisson's ratio. Although the graphs are based on linear analysis, important nonlinear effects may be taken into account by application of the graphs in a stepwise manner. Comparison of predicted response with that from a specific finite-element analysis of a field structure suggests that the errors introduced by idealizations associated with the graphical approach may be insignificant for many projects. In addition, comparisons of predictions with field measurements show encouraging results. (Author)

Nonlinear soil-structure interaction analysis of SIMQUAKE II. Final report

Abstract: This report describes an analytic method for modeling of soil-structure interaction (SSI) for nuclear power plants in earthquakes and discusses its application to SSI analyses of SIMQUAKE II The method is general and can be used to simulate a three-dimensional structural geometry, nonlinear site characteristics and arbitrary input ground shaking The analytic approach uses the soil island concept to reduce SSI models to manageable size and cost Nonlinear constitutive behavior of the soil is represented by the nonlinear, kinematic cap model In addition, a debonding-rebonding soil-structure interface model is utilized to represent nonlinear effects which singificantly alter structural response in the SIMQUAKE tests STEALTH, an explicit finite difference code, is used to perform the dynamic, soil-structure interaction analyses Several two-dimensional posttest SSI analyses of model containment structures in SIMQUAKE II are performed and results compared with measured data These analyses qualify the analytic method They also show the importance of including debonding-rebonding at the soil-structure interface Sensitivity of structural response to compaction characteristics of backfill material is indicated

Soil - structure interaction - general report

Abstract: This general report has two objectives: (i) to review some of the more significant developments in the area of soil structure interaction analysis since 1977. (Ii) to review the papers presented to this session. Attention in the first section will be concentrated on methods and applications of analytical techniques to problems involving static loading. Excluded from consideration will be problems involving dynamic loading and problems related to rock mechanics. Soil structure interaction will be interpreted in the widest sense, and will cover problems ranging from loading over portion of a soil mass to problems involving interaction between the soil, the foundation and the superstructure.