Showing papers on "Soil structure interaction published in 1998"

Lateral loading of a pile in layered soil using the strain wedge model

Abstract: Beam on elastic foundation theory provides an efficient solution for the problem of a laterally loaded pile. The accuracy of such a solution depends upon the characterization of the interaction between the pile and the surrounding soil. A particularly good representation of the soil-pile interaction yields a more realistic solution. While traditional nonlinear "p-y" characterization provides reasonable assessment for a wide range of loaded piles, it has been found that the p-y curve (or the modulus of subgrade reaction) depends on pile properties (width, shape, bending stiffness, and pile-head conditions) as well as soil properties. The strain wedge model allows the assessment of the nonlinear p-y curve response of a laterally loaded pile based on the envisioned relationship between the three-dimensional response of a flexible pile in the soil to its one-dimensional beam on elastic foundation parameters. In addition, the strain wedge model employs stress-strain-strength behavior of the soil as established from the triaxial test and the effective stress condition to evaluate the mobilized soil behavior.

A direct method for analysis of dynamic soil-structure interaction based on interface idea

Abstract: This paper presents a direct finite element method for analysis of dynamic soil-structure interaction based on the large general structure analysis software. The method can simulate not only the absorption of infinite soil to the scattering wave but also the elasticity recovery capacity of the far field media on the boundary. A new input method of wave motion dealing with dynamic soil-structure interaction is also proposed which can be used to exactly simulate seismic wave input with any angle. The accuracy of the methods presented in this paper is demonstrated by the numerical examples.

System identification for evaluating soil–structure interaction effects in buildings from strong motion recordings

Abstract: Parametric system identification is used to evaluate seismic soil–structure interaction effects in buildings. The input–output strong motion data pairs needed for evaluations of flexible- and fixed-base fundamental mode parameters are derived. Recordings of lateral free-field, foundation, and roof motions, as well as foundation rocking, are found to be necessary for direct evaluations of modal parameters for both cases of base fixity. For the common situation of missing free-field or base rocking motions, procedures are developed for estimating the modal parameters that cannot be directly evaluated. The accuracy of these estimation procedures for fundamental mode vibration period and damping is verified for eleven sites with complete instrumentation of the structure, foundation, and free-field. © 1998 John Wiley & Sons, Ltd.

Evaluation of bridge damage data from the Loma Prieta and Northridge, California earthquakes

Abstract: The overall objective of this task was to correlate observed bridge damage resulting from the 1989 Loma Prieta and 1994 Northridge earthquake to the local ground motions, bridge structural characteristics, and repair costs and time. Damage states reported after the earthquakes were investigated and new damage state definitions for concrete bridges were proposed. Bridges were grouped by their structural characteristics and correlation studies were performed to obtain ground motion-damage relationships and ground motion-repair cost ratio relationships. Logistic regression analysis was used to obtain empirical fragility curves. Currently available fragility curves and damage probability matrices were compared to observed damage data and the empirical relationships developed in this study.

Coupled soil-pile-structure interaction analysis under seismic excitation

Abstract: Seismic soil-pile-structure interaction has been an area of limited research, and most of the existing work adopts the conventional approach of soil-structure interaction analyses in which the problem is solved by superposition of kinematic and inertial interaction This multistep approach is often time consuming The present study focuses on a coupled finite element–boundary element type approach, where the entire problem domain is solved in a single pass The problem is cast in the frequency domain and a substructured method of analysis is adopted by interfacing the superstructure and the foundation at the foundation cap level The free-field seismic response is calculated by an equivalent-linear method that is widely used The formulation allows for multiple supports with varying excitations Coupling of the problem allows one to construct transfer functions for various degrees of freedom in the structure including the effects of interaction A number of examples presented in this paper demonstrate the

Effects of foundation embedment during building–soil interaction

Abstract: SUMMARY A numerical solution for evaluating the e⁄ects of foundation embedment on the e⁄ective period and damping and the response of soil—structure systems is presented. A simple system similar to that used in practice to account for inertial interaction e⁄ects is investigated, with the inclusion of kinematic interaction e⁄ects for the important special case of vertically incident shear waves. The e⁄ective period and damping are obtained by establishing an equivalence between the interacting system excited by the foundation input motion and a replacement oscillator excited by the free-field ground motion. In this way, the use of standard free-field response spectra applicable to the e⁄ective period and damping of the system is permitted. Also, an approximate solution for total soil—structure interaction is presented, which indicates that the system period is insensitive to kinematic interaction and the system damping may be expressed as that for inertial interaction but modified by a factor due to kinematic interaction. Results involving both kinematic and inertial e⁄ects are compared with those obtained for no soil—structure interaction and inertial interaction only. The more important parameters involved are identified and their influences are examined over practical ranges of interest. ( 1998 John Wiley & Sons, Ltd.

Seismic Response of Gravity Quay Walls. II: Numerical Modeling

Abstract: It is important to understand the seismic response of quay walls in order to design these structures against earthquake loading. Centrifuge experiments were carried out at Cambridge University on gravity quay walls. In this paper, an effective-stress based, fully coupled finite element code called SWANDYNE is used to simulate the response of gravity quay walls under earthquake loading, and the results are compared with the data from centrifuge tests. It is found from the analysis that the absorbing boundaries used in the centrifuge experiments to simulate the free field condition can be effectively modeled by a new numerical technique. The initial velocity and displacement conditions experienced by the centrifuge model need to be replicated in the numerical analysis. Special slip elements were used at the interface between the quay wall and soil body to improve the numerical predictions. The results of numerical modeling agree reasonably well with experimental data for both dry and saturated tests.

Seismic response of gravity quay walls. i: centrifuge modeling

Abstract: Failure of gravity quay walls induced by earthquakes has been widely observed in the field. This paper studies the behavior of gravity quay walls under earthquake loading using data from three centrifuge tests. Failure modes similar to those observed in the field were replicated in centrifuge tests. It is shown that excess pore pressure generated in the backfill increases both the angle of failure wedge and the horizontal thrust on a retaining wall. Lateral displacement of a gravity retaining wall with dry backfill can be estimated using Newmark's method. However, for a retaining wall with saturated backfill, the presence of excess pore pressure makes it difficult to apply this type of calculation. Cyclic shear stresses and excess pore pressures induced by base shaking can lead to deterioration of soil strength and stiffness, which reduces the fundamental frequencies of wall vibrations. Implications for design are discussed.

Non‐linear dynamic earth dam–foundation interaction using a BE–FE method

Abstract: A general, rigorous, coupled Boundary Element–Finite Element (BE–FE) formulation is presented for non-linear seismic soil–structure interaction in two dimensions. The BE–FE method is applied to investigate the inelastic response of earth dams to transient SV waves. The dam body, consisting of heterogeneous materials modelled with a simple non-linear hysteretic model, is discretized with finite elements, whereas the elastic half-space is discretized with boundary elements. The study focuses on the combined effects of the material non-linearity and foundation flexibility. The results show the significant effect of the foundation flexibility in reducing the response through radiation of energy. For excitations with peak ground accelerations from 0·2gto 0·6g, the crest acceleration amplification ranges from 2·5 to 1·4 and seems to be comparable with field observations and results from other studies. Deamplification increasing with strain is reported at the lower part of the dam. The method is computationally powerful and can be used for efficient non-linear analysis of complex soil–structure systems. The efficiency of the BE–FE method allows further improvements with incorporation of a more advanced constitutive model and consideration of the generation and dissipation of pore-water pressures during the earthquake. © 1998 John Wiley & Sons, Ltd.

Dynamic soil-structure interaction for high-rise buildings

Abstract: The authors analyze vibration impedance function of raft and pill foundations on layered media with 3-D model consisting of spacial beam, columm and panel elements. The paper presents super-structure-foundation-soil 3-D dynamic interaction equations and corresponding program with substructure method. The recults are compared for commonly used frame and frame-shear wall structures on different subsoil, different types of foundation and different input of seismic waves. The results show variation of vibration period of structure, displacement, stresses under consideration of interaction. It can be seen that it is necessary to compile a soil-structure interaction program of dynamic analysis for high-rise buildings.

Summary report of research on permanent ground anchor walls, volume ii: full-scale wall tests and a soil-structure interaction model

Abstract: Research directed toward improving the design and construction of permanent ground anchor walls is presented. The research focused on tiedback soldier beam walls for highway applications. These walls are generally less than 25 ft (7.62 m) high, and they are supported by one or two rows of permanent ground anchors. This volume is part of a four-volume report summarizing the research. It presents the results of research on a ground anchor wall constructed in a medium dense sand, and the development of a numerical model to be implemented in a computer program for the design of soldier beams. Apparent earth pressure diagrams for one-tier and multi-tier walls are developed. Measured bending moments are compared with moments predicted by different design methods. Axial load behavior of the soldier beams is described. The behavior of drilled-in and driven soldier beams is compared. Axial loads, bending moments, wall and ground movements, and anchor loads for each stage of construction are included. A numerical model that combines apparent earth pressure diagrams to describe the pressure on the wall, and soil spring to model the lateral resistance below the bottom of the excavation, is presented.

Effects of soil-structure interaction on nonlinear response of arch dams

Abstract: Summary Effects of two important factors on earthquake response of high arch dams are considered and combined into one program. These factors are: effects of dam-canyon interaction and that of local nonlinearity of the contraction joint opening between the dam monoliths. The substructuring technique is employed, thus the equilibrium iteration involves only the degrees of freedom in nonlinear substructure. For modeling of rock canyon, the discrete parameters are obtained based on a curve fitting, thus allowing the nonlinear dam system to be solved in the time domain. A simplified earthquake input procedure is also used, which takes into account the radiation damping of the infinite canyon while preventing the artificial amplification of the ground motion through the rock mass. Two engineering examples are given to demonstrate the significant effects of the above-mentioned two factors on the response of the structure.

Soil-structure interaction analysis of longitudinal uplift of culverts

Abstract: In response to problems of corrugated metal pipe (CMP) culvert uplift failure caused by unbalanced inlet hydraulic loading, full-scale field testing and numerical analysis were carried out to develop a rational design methodology for CMP inlet tie-downs. This paper describes a series of uplift tests carried out on a 2.44 m diameter CMP under different backfill configurations and a two-dimensional (2D) approach to the analysis of the three-dimensional (3D) problem. This 2D approach used a longitudinal finite element bending analysis with equivalent soil resistance springs generated from plane strain analyses of transverse sections along the CMP length. Comparisons of the test results with the model indicate that the backfill plays a significant role in the uplift restraint process and that the 3D problem may be effectively modeled by linking 2D models. The analyses indicate that the backfill cohesion and stiffness have the greatest effect on the uplift resistance and that the resistance was less sensitive to the soil friction angle and the properties of the soil/CMP interface.

Dynamic soil-structure interaction : current research in China and Switzerland

Abstract: Simple physical models for foundation dynamics the scaled boundary finite-element method - alias consistent infinitesimal finite-element cell method - for unbounded media effects of soil-structured interaction on nonlinear response of arch dams applications of transmitting boundaries to non-linear dynamic analysis of an arch dam-foundation-reservoir system a decoupling numerical simulation of wave motions scattering of plane SH waves by cylindrical surface topography of circular-arc cross-section applications of infinite elements to dynamic soil-structure interaction problems non-reflecting boundary conditions for wave propagation problems and their stability analysis boundary element method for SH waves in elastic half plane with stochastic and heterogeneous properties effects of soil-structure interaction on structural vibration control dynamic soil-structure interaction for high-rise buildings nonlinear dynamic analysis of saturated soil-structure interaction by FEM dynamic soil-structure interaction on layered strata under seismic wave incidence nonlinear SSI-simplification approach, model test verification and parameter studies for seismic and air-blast environment a direct method for analysis of dynamic soil-structure interaction based on interface idea an analytical approach for evaluation of global dynamic impedance of semi-circular dam canyon cut in an elastic half-space a coupling model of FE-BE-IE-IBE for nonlinear layered soil-structure interactions a hybrid procedure of distinct-boundary element for discrete rock dynamic analysis.