Showing papers on "Soil structure interaction published in 1997"

Seismic design and performance of geosynthetic-reinforced soil structures

Abstract: Seismic design procedures are proposed for geosynthetic-reinforced soil structures. The procedures are based on a pseudo-static limit equilibrium analysis, which considers horizontal acceleration and incorporates a permanent displacement limit. Internal and external stability analyses are conducted to determine the required strength and length of geosynthetic, considering different modes of failure. Parametric studies illustrate the effects of seismic acceleration on the design of reinforced soil structures having different slope angles and soil properties. For vertical slopes at small seismic acceleration, tieback/compound failure dictates the required geosynthetic length. The length required to resist direct sliding increases rapidly as the seismic acceleration increases. This length may become impractical at moderate design accelerations. For such cases, an alternative approach based on a tolerable displacement against direct sliding is proposed for design. The proposed procedures are compared with the...

Piles Subjected to Lateral Soil Movements

Abstract: This paper presents a theoretical procedure for analyzing the lateral response of vertical piles subjected to lateral soil movements. The lateral pile response is computed via a simplified boundary-element analysis, using a specified free-field soil movement profile. For pile groups, the group effect may need to be preassessed via a finite-element analysis. Based on an appropriate assessment of the lateral soil movement, soil Young's modulus and limiting pile-soil contact pressure, the present method can generally give a satisfactory prediction of the pile response, as demonstrated via a study of some model tests and published case histories. For practical convenience, some elastic solutions have been generated using the present boundary-element program and are presented in chart form. These design charts tend to give an upper-bound estimation of the maximum pile bending moment and pile head deflection, although a close estimation may be obtained for small soil movements.

Analysis of Piles Subjected to Embankment Induced Lateral Soil Movements

Abstract: Damage to piles supporting structures, bridge abutments, and utilities can occur as a result of the construction of nearby embankments. This is because the lateral displacements resulting from these construction activities can induce forces and moments in the piles. The resulting stresses can be significant particularly when soft soil deposits are present and the lateral soil displacements are large. This paper describes a simplified numerical procedure based on finite-element method for analyzing the response of single piles to lateral soil movements. The flexural bending of the pile is modeled by beam elements. The complex phenomenon of the pile-soil interaction is modeled by hyperbolic soil springs. A framework for determining the soil parameters for use in the analysis is summarized here. Comparisons are made between the observed behavior of full-scale tests and centrifuge model tests and those computed by the proposed numerical method. Based on parametric studies, empirical design solutions for pile foundation systems at the base of a sloped embankment are presented.

Drained Granular Material Under Cyclic Loading With Temperature-Induced Soil/Structure Interaction

Abstract: This review article is divided into three parts. Firstly, three soil/structure interaction problems are described in which strain is imposed on the soil caused by solar heating of the structures. They are modeled by reference to cyclic ratcheting strains with the help of a simple two-component model comprised of one elastic element and one element of granular material. Possible stable shakedown solutions are described for a bridge and filter bed. In contrast, a tower structure may become progressively less stable with increasing load cycles. Secondly, our experimental results from plane strain biaxial tests on sand under drained cyclic loading conditions are shown to complement the work of others. Results reveal the existence, in strain control experiments, of a unique shakedown stress ratio, S, which is independent of cyclic strain amplitude, but with the associated void ratios being strain-amplitude dependent. At very small strain amplitudes S may decrease. Thirdly, numerical modeling methods are described. These include applications of nonlinear elasticity, and elasto-plasticity including endochronic theory, to predict the behavior of granular materials under cyclic loading. It is concluded that temperature-induced cyclic loadings are of importance in some soil/structure interaction situations, and that reliable predictions can be made in simple cases. Further knowledge and research is needed to fully predict the incremental evolution of fabric change during cyclic stressing and cyclic straining. Either existing models will be required to be modified, or new ones formulated to capture all the features covered in this paper

Implications of spatial variation of ground motion on the seismic response of bridges: case study

Abstract: Linear and nonlinear analytical studies were conducted for evaluating the performance of the southbound separation and overhead bridge at the SR14/I-5 interchange during the Northridge earthquake of January 17, 1994. The analyses are focused on potential implications of the spatial variability of ground motion on the collapse of the structure. The influences of vertical ground motion, soil-structure interaction and nonlinear contact effects at the expansion joints and abutments, are also examined. The parameter studies help to determine some of the causes of collapse and offer insight on the complex seismic behavior of long multi-span concrete bridges.

Failure analysis of underground rc frame subjected to seismic actions

Abstract: 本研究は地中鉄筋コンクリート構造の破壊解析を提示し, 経路依存性を考慮した材料構成モデルに基づき, 地中構造の破壊機構について論ずるものである. 考慮した非線形性は鉄筋コンクリート, 地盤材料および地盤構造間の応力伝達機構である. 主として鉛直荷重を支える部材のせん断破壊に着目し, 破壊に及ぼす地盤の非線形性, 地震入力の違い及び鉛直成分の有無について検討を行った. 保有する耐震性能は地盤と構造自体の非線形性を共に考慮しなければならないことが確認された.

Soil-structure interaction during pile vibratory driving

Abstract: A rational procedure to model the dynamic nonlinear soil structure interaction during pile vibratory driving is presented. The procedure is based on the analysis of the dynamic behavior of a cylinder embedded in a semi-infinite medium. Cylindrical shear waves that propagate away from the vibrated pile are evaluated using a one-dimensional radial discretization of the soil surrounding the pile. Degradation of the skin friction upon cyclic shear stress is evaluated by applying elements of earthquake engineering practice used to assess liquefaction potential. The friction ratio as measured in a CPT test, serves as a correlation parameter to present charts allowing one to estimate the soil degradation and excess pore-pressure buildup. A sample calculation illustrates the importance to account for soil cyclic degradation.

Seismic Analysis and Design for Soil-Pile-Structure Interactions

Abstract: Pile foundations are used extensively to support structures in seismic regions around the world. For years, geotechnical engineers have neglected to consider the interaction soil-pile systems have with superstructures; while civil engineers have ignored the interaction of the foundation with the structure. In order to understand a structure's response to dynamic loads, the complete soil-pile-structure interaction must be analyzed. Thus, centrifuge models, shake table models, and analytical methods are used to explore the interactions among soil, piles, and structures.

Effect of soil consolidation on space frame-raft-soil interaction

Abstract: Nonlinear consolidation analysis using a finite-element formulation based on Biot's consolidation theory has been used to study the time-dependent behavior of three-dimensional (3D) frame structures resting on an elastic or elastic perfectly plastic soil satisfying the Drucker-Prager yield criterion. The effect of soil consolidation on the behavior of a 3D frame-raft-soil mass system is considered. The initial stress method with a modified Newton-Raphson iterative scheme has been used for this study. A coupled finite-infinite element modelization is used for the physical representation of the system. Time history of axial forces and bending moments of the mat foundation and the structural elements (beams and columns) are compared with those of time-independent analysis. The results show that the consolidation of soil increases the internal forces in some elements, so that checking the final forces in the frame by time-independent conventional frame analysis may not be sufficient.

Geotechnical Aspects of Soil — Structure Interaction Design Considerations

Abstract: Marine engineering involves the combination of several skills, including an intimate knowledge of all structural design aspects as well as an awareness of soil and rock mechanics and foundation engineering. Furthermore, a firm understanding of the basic principles of soil-structure interaction is a must. This is most apparent in connection with nonrigid structures such as sheet-pile bulkheads, or other structures where soil pressure distribution at the interface is governed by the deformation or displacement of such structures.

The effect of external confinement and transverse reinforcement on plastic hinges in cast-in-place pile shafts : experimental results

Abstract: This study reports on the testing of cast-in-place pile shafts designed to examine the effect of transverse reinforcement, and the confining effect of soil on the structure's performance. An experimental apparatus was designed for the purpose of simulating the moment pattern in the structure. In two test units, three levels of transverse reinforcement were tested, using California Department of Transportation (Caltrans) design guidelines as baseline design and with no variation in longitudinal reinforcement. The confining effect of soil was tested with simulation on one unit of each pair, while the other unit was tested without any external confinement. It was determined that confinement provided by soil around the pile shaft can substantially enhance the overall ductility capacity of the structure.

Investigation of soil-structure interaction in tied-back walls

Abstract: In this study, behavior of diaphragm walls with prestressed anchors during construction is investigated with numerical analysis and model testing, taking into consideration soil-structure interaction at anchor/soil and wall/soil interfaces. In the first phase of investigations, the load-deformation behavior of an anchor in soil during prestressing is studied with the help of pull-out tests, and the finite element analysis. Based on the evaluation of experimental results and analytical solutions for pull-out tests, conclusions are presented. In the second phase of investigations, the behavior of anchored diaphragm walls, as the excavations in front of the wall proceeds, is studied with model testing and numerical analysis. Based on the evaluation of experimental observations and analytical solutions, conclusions are reached for the behavior of anchored diagphram walls. (A) For the covering abstract see IRRD 898458.

Soil-structure interaction and axial force effect in structural vibration

Abstract: A numerical procedure for dynamic analysis of structures including lateral-torsional coupling, axial force effect and soil-structure interaction is presented in this study. A simple soil-structure system model has been designed for microcomputer applications capable of reflecting both kinematic and inertial soil-foundation interaction as well as the effect of this interaction on the superstructure response. A parametric study focusing on inertial soil-structure interaction is carried out through a simplified nine-degree of freedom building model with different foundation conditions. The inertial soil-structure interaction and axial force effects on a 20-storey building excited by an Australian earthquake is analysed through its top floor displacement time history and envelope values of structural maximum displacement and shear force.

Seismic response of structures on embedded foundations

Abstract: The potential importance of soil structure interaction effects on the seismic response of structures has been long recognized. The nature of the interaction phenomena, including the modification of the seismic waves by the foundation's geometry (kinematic interaction) and the increase in the structure's effective flexibility due to the foundation and the surrounding soil (inertial interaction) have also been detailed in a number of papers. The possibility of having a reduction of the seismic motions for embedded foundations has been, however, a subject of continued controversy. The general topic of soil structure interaction for structures with embedded foundations is revisited in this paper, reviewing the basic concepts with some emphasis on approximate solutions which allow to develop a better feeling for the behavior of the solution.