Showing papers on "Soil structure interaction published in 1990"

Soil-structure interaction effects for laterally excited liquid storage tanks

Abstract: A comprehensive study is made of the effects of soil-structure interaction on the response of liquid containing, upright, circular cylindrical tanks subjected to a horizontal component of ground shaking. A simple, physically motivated method of analysis is employed which elucidates the effects and relative importance of the principal actions involved. Both the impulsive and convective actions of the liquid are examined. The interrelationship of the tank responses to horizontal and rocking actions of the foundation is established, and the well known mechanical model for laterally excited, rigid tanks supported on a non-deformable medium is generalized to permit consideration of the effects of tank and ground flexibilities and base rocking. Critical responses are evaluated for harmonic and seismic excitations over wide ranges of tank proportions and soil stiffnesses, and the results are presented in a form convenient for use in practical applications. In addition to a precise method of analysis, an approximate, hand-computation method is presented with which the effects of the primary parameters may be evaluated readily. The soil-structure interaction effects in the latter approach are provided for by modifying the natural frequency and damping of the tank-liquid system and evaluating its response to the prescribed free-field ground motion considering the tank to be rigidly supported at the base. The requisite modifications may be determined from information presented herein. It is shown that soil-structure interaction may reduce significantly the impulsive components of response but that it has a negligible effect on the convective components.

Soil Response for Pipeline Upheaval Buckling Analyses: Full-Scale Laboratory Tests and Modelling

Abstract: A pipeline is subjected to a compressive load when its thermal expansion is axially restrained. This load can cause the pipeline to buckle when the lateral and axial friction resistances are not sufficient to prevent pipeline movement. The resulting movement will usually be upwards, since this direction has the smallest lateral restraint. The likelihood of this upheaval buckling phenomenon is largely determined by the capability of the soil to resist pipeline movements. Detailed understanding of uplift and axial friction resistance thus contributes to the improvement of reliability and economy of pipeline design against this failure mode. The paper presents the results of a full-scale laboratory test programme on the uplift and axial resistance of a 4 in pipe embedded in saturated soil for a wide range of soil conditions. The soil types include dense and loose sand, remoulded clay and rock. These soils were used for cover conditions ranging from homogeneous to trenched, over depth-to-diameter ratios between 4 and 12. Although most tests were quasi-static, a number of uplift tests specifically studied time-dependencies. All tests were performed under described and well defined conditions and test procedures that approach offshore conditions as closely as possible.

Hyperbolic parameters for compacted soils.

Abstract: Finite element methods are being used more and more during design, in cases involving compacted soil-structure interaction. In general, it is not practical to conduct extensive tests to obtain the compacted soil properties required by the finite element methods during the design phase. Alternatively, if finite element approaches are used for developing design tables, soil properties representative of typical soil types and compaction specifications are required. To provide the needed design soil parameters for a wide variety of soil conditions, laboratory testing is carried out on three soils: a sand, a silt, and a clay. These soils are prepared at density states ranging from loose to 95% of the maximum from the standard compaction tests (American Society for Testing and Materials (ASTM) D698, American Association of State Highway and Transportation Officials (AASHTO) T-99). The tests used to obtain the soil parameters are triaxial compression, isotropic compression, and one-dimensional compression. A consistent set of soil design parameters are obtained by fitting test results to a hyperbolic soil model representing Young’s modulus and bulk modulus as functions of stress.

Deterministic Assessment of Effects of Ground‐Motion Incoherence

Abstract: An approximate deterministic method of analysis is presented for assessing the effects of ground‐motion incoherence and of the associated soil‐structure interaction on the seismic response of structure‐foundation‐soil systems. The free‐field ground motion in this approach is specified by an acceleration history and a spatial incoherence function. Numerical solutions are presented that illustrate the procedure and elucidate the nature and relative importance of the kinematic and inertial interaction effects. The results are shown to be consistent with those obtained in a recent companion study by formal application of the stochastic approach.

Bridge abutments: assessing their influence on earthquake response of meloland road overpass

Abstract: Strong‐motion earthquake data obtained on the Meloland Road Overpass during the 1979 Imperial Valley earthquake are used to examine the suitability of simple models for representing the transverse and vertical stiffnesses of the abutment‐embankment systems on highway bridges. Information on the seismic responses of both the abutment‐embankment systems and the bridge superstructure is obtained by applying techniques of system identification to the strong‐motion records. Analytic models, as developed in a companion paper, that account for the transverse and vertical stiffness characteristics of the bridge abutment systems are used to calculate equivalent abutment stiffnesses for incorporation into finite element models of the Meloland bridge. Predicted earthquake responses of these models are compared to the measured seismic responses and to optimal modal parameters obtained from the system identifications. Results of the various analyses show that the simplified models work quite well in simulating the sti...

Impedances of soil layer with boundary zone

Abstract: When calculating dynamic response of embedded foundations or piles, impedances (stiffness and damping) of the adjacent soil are needed. To account approximately for soil nonlinearity under high strain, contact deficiencies and disturbances caused by foundation installation, a cylindrical annulus of softer soil around the foundation is used. The soil properties in this weakened boundary zone differ from those of the outer zone but both regions are assumed to be homogeneous. The mass of the cylindrical annulus can be either neglected or accounted for. If this mass is considered, a seemingly more accurate approach, wave reflections from the interface between the two media can occur resulting in marked undulations of the impedances with regard to frequency and, possibly, in negative stiffness. It is the purpose of the paper to show that such undulations are unrealistic and that the impedances featuring them can be less suitable for practical application than those obtained neglecting the mass of the inner zone.

A simple boundary element formulation and its application to wavefield excited soil‐structure interaction

Abstract: A simple boundary element formulation which is based directly on the point load solutions for an elastic full-space is presented. It is integrated in a finite element program to calculate dynamic soil-structure interaction problems. The combined boundary and finite element method is applied to structures which are excited by horizontally propagating waves in the soil. For three different types of flexible structure-elastic beams, low and high (square) shear walls-and the corresponding rigid structures the vibration modes and the soil-structure transfer functions have been investigated. The flexible foundations display the same wave pattern as the exciting free-field of the soil, but the amplitudes are reduced with increasing frequency, depending on the stiffness or wave resistance of the structure. Rigid structures show, in part, quite different behaviour, giving free-field reductions caused by kinematic and inertial soil-structure interaction.

A theoretical study of pile heave

Abstract: Installation of a driven pile displaces the soil vertically and radially. The ensuing vertical soil movement causes the uplift or heave of piles already installed in the vicinity. The Paper describes a theoretical study of the vertical soil movement and the pile heave due to the installation of a driven pile in clay. The clay deposit is idealized as a homogeneous isotropic incompressible linear elastic half-space. Pile installation is simulated by the injection of material along the pile axis with a constant intensity. The resulting soil movement is obtained using the source-sink imaging technique. The heave of a pile already installed is obtained from the interaction between the pile and the vertical soil movement. Numerical results are presented showing how the soil movement is affected by the dimensions of the penetrating pile. The pile heave is affected by the ratio of the Young's moduli of the pile and soil, in addition to the pile dimensions and pile spacing. A number of reported case histories are ...

Effect of jackup spud cans on piles

Abstract: This paper describes the determination of lateral soil displacement profiles surrounding a jackup rig spud can penetrating in soft clay. The displacement profiles were inferred from pile moment data obtained from centrifuge tests which modelled a spud can penetrating next to three instrumented piles. A beam-column model which incorporates movable soil supports was employed to infer the soil displacements from the pile moment data. At distances as close as 0.5 spud can radii from the spud can edge, the soil displacements were found to be small. The inferred displacements were found to be consistent with physical measurements within the model.

Response of Finite Depth Seabed to Waves and Caisson Motion

Abstract: The response of a poroelastic seabed to waves and caisson motion is modeled using Biot consolidation theory. The caisson is founded on a rubble bedding layer overlying a seabed of finite depth. Two approximations are employed to solve the boundary-value problem analytically: (1) A boundary layer approximation to decouple pore pressure and soil motion in the Biot equations; and (2) a contact solution approximation for a thin elastic layer to address the mixed-type mud line condition. The analytical solution is verified by comparison with finite element model results and large-scale experiments. The analytical and finite element model estimates of the soil stresses and surface displacements are in good agreement. Experimental and analytical comparisons for pore pressure are in agreement but the displacement comparisons are quite scattered.

Soil‐Structure Interaction in Buildings from Earthquake Records

Abstract: An evaluation of the response of a fourteen story reinforced concrete building to the 1 October 1987 Whittier earthquake and 4 October 1987 aftershock shows significant effects of soil-structure in...

Soil‐structure interaction effects on strong motion accelerograms recorded on instrument shelters

Abstract: The distortions of earthquake ground motions recorded in small instrument shelters as a result of soil-structure interaction effects are investigated by means of a theoretical parametric study. A total of 12 foundation geometries varying in basal radius, embedment depth and extension above the ground surface and a number of soil profiles including uniform and layered soil models were considered. The results obtained show significant amplification and deamplification of the free-field ground motion for sufficiently soft soils (β 20 Hz).

Review of Finite Element Procedures for Earth Retaining Structures

Abstract: : This miscellaneous paper presents a review of previous work in which the finite element method was used to analyze the soil structure interaction of earth retaining structures such as U-frame locks, gravity walls, and basement walls. This method of analysis results in the computation of stresses and displacement for both the structure and the soil backfill. Applications of the procedure have shown the importance of modeling the actual construction process as closely as possible and the use of a nonlinear stress-strain soil model. Additional requirements include modeling the interface between the soil backfills and the wall using interface elements. This paper also includes two recent applications of the finite element method for the analysis of earth retaining structures which are loaded so heavily that a gap develops along the interface between the base of the structure and its foundation. The results are compared to those computed using the conventional force equilibrium method of analysis.

Methods of evaluating the stability and safety of gravity earth-retaining structures founded on rock : phase 2 study

Abstract: : Comparisons between the results of backfill placement analyses using finite element and the conventional equilibrium analyses indicate that conventional analyses are conservative. The finite element analyses indicate that the backfill exerts downward shear loads on the backs of retaining walls. These shear forces have a stabilizing effect on the walls. Shear loading ranged in value from 0.09 to 0.21, depending on the geometrical features and the values of the material parameters involved in the problem. In general, as the wall moves away from the backfill, the lateral forces exerted on the wall by the backfill decrease, and the lateral forces exerted on the front on the wall by the toe-fill increase. Keywords: Soil structure interaction; Soils/pressure; Loads forces; Walls/deformation/displacement; Foundations structures/rock; Soil stabilization; Backfills/stiffness; Shear stresses; Earth fills.

Evaluation of ATC Requirements for Soil‐Structure Interaction Using Data from the 3 March 1985 Chile Earthquake

Abstract: The effect of soil‐structure interaction on building responses is investigated using data from the 3 March 1985 Chile earthquake. Four shear wall buildings located in Vin˜a del Mar, Chile and subjected to strong, long duration, earthquake ground motions during the 3 March 1985 Chile earthquake are studied. Detailed analyses are conducted on one building using available information on soil properties, measured periods, and recorded ground motions. Based on the detailed study, ATC‐3 procedures are used to incorporate soil‐structure interaction effects for three additional buildings. The analyses indicate that soil‐structure interaction is an important consideration for the stiff shear wall buildings located in Vin˜a del Mar, Chile. Reductions in base shear of 10 to 47% were computed; however, roof drift ratios generally were unchanged. For spectra representing US design ground motions (ATC), reductions in base shear are not expected to be as pronounced and roof drift ratios are expected to increase...

Theoretical and Experimental Solutions of Cooling‐Tower‐Soil system

Abstract: In recent years, there have been many papers on dynamic properties of cooling towers. However, the bottoms of the tower shells were assumed as a fixed boundary, or discrete column systems of towers were considered as elastic boundary conditions. In the present paper, tower shells and discrete supports are treated as before. Furthermore, a dynamic model of an infinite soil is developed, and dynamic properties of the whole system of the cooling tower have been calculated. Model tests of free vibrations of cooling towers on different simulated soils are investigated. The numerical and experimental results are in agreement. The results show that the elasticity of the soil reduces the natural frequencies of the cooling tower and the reduced value depends on the stiffness of the soil. Some of the mode shapes of the cooling tower are changed much as compared to a built-in tower.

Hybrid experiments on non‐linear earthquake‐induced soil‐structure interaction

Abstract: Non-linear seismic soil-structure interaction is studied through a hybrid procedure using the pseudo-dynamic testing (PDT) method which is modified to take into account frequency dependence and developed for foundation-soil systems. The numerical scheme used in conventional PDT is improved by introduction of a time-dependent pseudo-forcing function which is derived from frequency-dependent dynamic characteristics of the system by means of Hilbert transformation in the frequency domain. Surface, shallow and caisson foundation models that differed in size and depth of embedment were used. The mechanical characteristics of the systems were determined from static and forced vibration dynamic tests. An amplitude scaling technique was used for three recorded accelerograms.

Theoretical and experimental analysis of soil-pipe interaction at free span shoulders for oscillating pipelines

Abstract: The behaviour of the surface layers of marine sediment under the cyclic loads transmitted by an oscillating submarine pipeline, affects the response of the pipeline as the sediment acts as a restraint and helps to dissipate the work performed by the hydrodynamic forces on the pipe. In this field experimental data is of the utmost importance to calibrate parameters to be used in engineering models, due to the intrinsic difficulty of interpreting and modelling theoretically the reaction from the generally loose surface layers of highly nonlinear constructive nature. After a brief introduction of the main aspects of pipe-soil interaction under dynamic conditions, the following is described: - brief details of the full-scale experimental approach for the simulation of dynamic conditions at free span shoulders - the methodology adopted to interpret the results, in particular to define the local parameters of stiffness and damping given by the bearing soil - some relevant findings, where the limits of the adopted techniques with respect to the goals and potential use of the results are defined.

A large scale experimental study of soil reinforcement interaction part 2

Abstract: Part 1 of this paper (see IRRD 837296) showed agreement between data from a series of large scale direct shear tests with the authors' proposed theory of soil reinforcement with bending stiffness. The present paper compares the theory with published data on instrumented reinforcement in direct shear tests and an instrumented nailed wall in Germany. The authors conclude that, for the design of steep slopes and excavations stabilised by conventional soil nailing, it is best to ignore the potential benefit of reinforcement bending stiffness. This radically simplifies the design calculation and only slightly alters its results. Such an approach is already followed in German standards of soil nailing, for example. It has also been shown that relatively large shear displacements are required to mobilise shear force in the reinforcement, and that failure will usually intervene as soon as the pullout capacity has been reached, but well before the full shear capacity of the reinforcement can be mobilised. The instrumented wall described in the paper provides a good example of this behaviour, agreeing with a comment by C. Plumelle et al that only close to failure and under large deformations is bending stiffness mobilised, giving an additional safety factor. (TRRL) (Author/TRRL)

Design and Testing of a Synthetic Clay Soil

Abstract: A synthetic clay soil mixture was designed and fabricated to comply with similitude requirements set forth in a dynamic scale-model pile group foundation test. The prototype soil was a stiff, fissured, overconsolidated clay soil at the University of Houston Pile Test Facility. The dynamic response of the model soil was determined through testing by resonant column/torsional simple shear methods and by seismic wave velocity tests in the model test bed. The synthetic clay soil was more nearly linear elastic to higher strain levels with less damping than natural clays. The ability of the soil to regain its strength after disturbance was beneficial to the scale-model tests. The design, fabrication, and testing procedures utilized to obtain an appropriate geotechnical material for scale-model soil/structure interaction tests is detailed in this article.