Foundation Interaction Research Articles

杭位置の違いによる群杭の非線形水平地盤抵抗のモデル化

1. Introduction Pile foundation response during earthquakes is strongly affected by nonlinear soil-pile foundation interaction. The damages to pile foundations during the 1995 Hyogo-ken Nanbu Earthquake and the 2011 Tohoku-Chiho Taiheiyo-Oki Earthquake were obviously attributed to nonlinear interaction of soil-pile foundation-superstructure. The dynamic nonlinear behavior of soil around each pile affects lateral load distribution and displacement of each pile. Therefore, shaking table tests were conducted to clarify the dynamic nonlinear behavior of soil around piles, further earthquake response analyses were conducted to simulate the effect of the nonlinear soil-pile interaction system on performance of the superstructure supported by pile group. 2. Outline of shaking table tests 25-pile group foundation model was set up in Toyoura sand deposits within a laminar container. The sand deposits were prepared by air pluviation method in the laminar container. The model piles were acryl cylinder with 12mm in diameter and 400mm long. 25 piles were arranged in squares and pile spacing was 2.0 times pile diameter. The superstructure was modeled as a rigid body. The input waves were seismic waves in notification with random phase of Japan and the Hyogo-ken Nambu earthquake. 3 input acceleration levels were used to investigate the influence of input motion level. Tests with and without the mass of superstructure were conducted to investigate lateral load distribution of each pile. 3. Outline of shaking table tests simulation Two analysis methods were conducted for simulation of tests, one is nonlinear 3D-FEM, and the other is lumped mass model. Two case of Lumped mass model are conducted, one is with soil springs around pile group which were different according to pile arrangements and direction of loading, and is with soil springs without pile group effect. Soil springs were calculated by using nonlinear 3-D FEM, which were modeled appropriately according to the location of pile. 4. Conclusions The concluding remarks of these shaking tests and analytical studies are as follows. (1) In shaking tests, lateral subgrade reaction around piles depends on the location of each pile in pile group and the direction of loading. That of the corner pile is remarkably larger than that of the middle pile. (2) In shaking tests, hysteresis curve of soil spring at the corner pile is found to be asymmetric loop, while that at the middle pile be symmetric loop. (3) In shaking tests, bending moment at each pile head depends on the location of each pile in pile group. That of corner pile head is remarkably larger than that of middle pile head. As the input level of acceleration increase, bending moment at each pile head is equalized. (4) The proposed lumped mass model of the soil-pile foundation system, which consists of beam elements and nonlinear interaction springs considering the location of pile, is verified validation. It is confirmed that this proposed model well represents response of the superstructure supported by pile group.

Macroelement Modeling of SSI Effects on Offshore Wind Turbines Subject to Large Number of Loading Cycles

In this paper, the hypoplastic macroelement formulation proposed by [1] has been modified in order to extend its range of applicability to offshore structures subject to cyclic loads with very high number of cycles, with particular attention to fatigue phenomena and cyclic displacement accumulation. A series of FE analysis has been performed to model the soil–foundation interaction processes of a prototype of offshore wind turbine, for which the geometrical characteristic of the superstructure and foundation, the soil conditions and the predicted environmental (wave and wind) loads were known. The study, carried out in parametric form, has allowed to better understand the role played by the modified cyclic part of the macroelement model in reproducing the shake–down effects as observed in small–scale model tests.

Practical Soil-Shallow Foundation Model for Nonlinear Structural Analysis

Soil-shallow foundation interaction models that are incorporated into most structural analysis programs generally lack accuracy and efficiency or neglect some aspects of foundation behavior. For instance, soil-shallow foundation systems have been observed to show both small and large loops under increasing amplitude load reversals. This paper presents a practical macroelement model for soil-shallow foundation system and its stability under simultaneous horizontal and vertical loads. The model comprises three spring elements: nonlinear horizontal, nonlinear rotational, and linear vertical springs. The proposed macroelement model was verified using experimental test results from large-scale model foundations subjected to small and large cyclic loading cases.

A numerical investigation on soil-concrete foundation interaction

The soil-concrete foundation interaction is one of the complicate job in civil engineering. The theoretical concept and numerical analysis are well supportive in understanding soil-concrete foundation interaction. In this paper, the seismic response of group concrete foundations are evaluated for understanding nonlinear soil behavior. The main objective is, to understand effect of a real earthquake acceleration on morphology of differential settlement of soil at the base of concrete foundation and the overall of the soil foundation. The ABAQUS has been used in numerical simulation, in order to simulate differential settlement of soil due to nonlinear soil-concrete foundation interaction. The models were subjected to similar seismic loading. The seismic data are reported at literature, used in numerical simulation. The results indicated that the differential settlement of soil depends on soil-concrete foundation interaction.

Nonlinear dynamics of matrix-cracked hybrid laminated plates containing carbon nanotube-reinforced composite layers resting on elastic foundations

This paper investigates the nonlinear dynamic response of hybrid laminated plates resting on elastic foundations in thermal environments. The plate consists of conventional fiber-reinforced composite (FRC) layers and carbon nanotube-reinforced composite (CNTRC) layers. Each layer may have matrix cracks, and the damage is described by a refined self-consistent model. The motion equations are based on a higher-order shear deformation theory with a von Karman type of kinematic nonlinearity. The thermal effects are included, and the material properties of both FRC and CNTRC are assumed to be temperature dependent. The plate–foundation interaction is also included. The motion equations are solved by a two-step perturbation technique to determine the dynamic response of matrix-cracked hybrid laminated plates. The boundary condition is assumed to be simply supported with in-plane displacements “movable” or “immovable.” The effects of stiffness reduction due to matrix cracks, the foundation stiffness, the temperature change, the percentage and distribution of carbon nanotubes in CNTRC layers are discussed in detail through a parametric study.

Nonlinear vibration of FGM doubly curved panels resting on elastic foundations in thermal environments

A large amplitude vibration analysis is presented for a shear deformable doubly curved panel made of functionally graded materials (FGMs) resting on elastic foundations in thermal environments. The effective material properties are evaluated using the Mori–Tanaka micromechanics model. The formulations are based on a higher order shear deformation theory and von Kármán strain–displacement relationships. The panel–foundation interaction and thermal effects are also included. The temperature-dependent material properties of FGMs are assumed to be graded in the thickness direction according to a simple power law distribution. The motion equations are solved by a two-step perturbation approach to determine the nonlinear frequencies of the FGM doubly curved panel. The numerical illustrations cover small- and large-amplitude vibration characteristics of FGM doubly curved panels resting on elastic foundations of Pasternak-type. The results obtained from the Mori–Tanaka model are compared with those obtained from the Voigt model. The results confirm that in most cases Voigt model and Mori–Tanaka model have the same accuracy for predicting the vibration characteristics of FGM doubly curved panels. The effects of volume fraction index, temperature variation, foundation stiffness and panel curvature ratio on the nonlinear free vibration behaviors of FGM doubly curved panels are also discussed in detail.

Pile pinning and interaction of adjacent foundations during lateral spreading

Studies recently conducted by the authors and others have demonstrated that relatively simple equivalent-static analysis (ESA) procedures can adequately predict the response of bridge foundations to lateral spreading for design purposes assuming that the lateral spreading displacement demand is known or can be estimated. However, an important aspect of the analysis that remains to be addressed is how to account for the restraining force provided by foundations when the laterally spreading ground does not have a finite, measurable out-of-plane width. This study addresses this problem in the context of two parallel, adjacent bridges crossing the Colorado River in Mexico that were subjected to a broad field of laterally spreading ground during the 2010 Mw 7.2 El Mayor–Cucapah earthquake. Two-dimensional finite element analyses (FEA) are used to quantify the influence that the presence of each bridge had on the lateral spreading demand for the opposite bridge. The results show that the relatively stiff founda...

Effects of Dam–Foundation Contact Conditions on Seismic Performance of Concrete Gravity Dams

This paper presents the effects of dam– foundation contact conditions on seismic performance of concrete gravity dams including base sliding. For illustrative purposes, the Oued Fodda concrete gravity Dam, located in Chlef (northwestern Algeria), is selected as an example and linear as well as nonlinear seismic analyses are performed. In addition, a parametric study based on the friction coefficient is carried out. The Druker–Prager and the multilinear kinematic hardening models are employed in the nonlinear analyses for concrete in the dam and rock in the foundation, respectively. The hydrodynamic pressure of the reservoir water is modeled as added mass using the Westergaard approach. The contact interface in dam–foundation interaction is modeled by contact elements which represent the friction contact. Surface-to-surface contact elements based on the Coulomb’s friction law are used to describe the friction. These contact elements use a target surface and a contact surface to form a contact pair. Depending on the component effects of strong ground motion and maximum friction stress characterizing the dam–foundation contact conditions, sliding displacement may occur at the interface causing instability of the dam. The results show that the base sliding displacement depend on the value of friction coefficient at the interface zone. Besides, the sliding displacement decreases the principal stresses in the dam as well as the base shear stress.

EFFECT OF FOUNDATION FLEXIBILITY ON DYNAMIC BEHAVIOUR OF ASYMMETRIC BUILDING FRAME WITH ISOLATED FOOTING

In general the seismic design of building frame structures the designers will consider only the results of fixed base condition the effect of flexibility is ignored. In post-earthquake study the framed structure reveals that the interaction of soil and foundation plays an important role in damage of the building frame structures. In this regard a literature survey has been done on frame structures supported on various foundations such as isolated, combined, raft & pile foundations. To examine the literature revels the few investigations were done on asymmetric building frame structure is supported on isolated footing. So in this paper is an attempt to the study of dynamic behavior of asymmetric building frame structure is supported on isolated footings. The modeling and analysis is done by using “finite element method software” SAP2000 VERSION 14, by considering the different soil conditions, (soft, medium, hard) different soil parameters (passion’s ratio, young’s modulus, dynamic shear modulus) different height ratio’s, different span ratio’s & fixed base conditions. The response of the building frame structure is obtained in terms of fundamental natural period, lateral displacement and seismic base shear.

Seismic assessment of a monolithic RCC gravity dam including three dimensional dam–foundation–reservoir interaction

In this study, the seismic response of a tall roller compacted concrete gravity dam located in a highly seismic zone is investigated. The response of this monolithic RCC gravity dam is examined by conducting analyses including three dimensional dam–reservoir–foundation interaction. The effect of the foundation/structure moduli ratio, material damping, and bottom absorption and reservoir compressibility on the performance of the dam were investigated. Selection of an optimal downstream slope was discussed based on a simplified stress based assessment method. RCC systems present a different paradigm compared to conventional gravity dams with their monolithic construction and/or wide joint spacing: The importance and necessity of a full 3D analyses for such systems were underlined by comparing the results with two dimensional analyses. For such gravity dams built in relatively narrow canyons, three dimensional analyses should be conducted for seismic safety assessment.

XFEM based seismic potential failure mode analysis of concrete gravity dam–water–foundation systems through incremental dynamic analysis

As revealed by the structural damage of concrete dams (e.g. Hsinfengkiang, Koyna, Sefid-Rud) arising in recent earthquakes, cracking damage would probably occur inside concrete dams when subjected to strong ground motions. This phenomenon is caused by the low tensile resistance of concrete. Research on the cracking damage process and failure modes of concrete gravity dams subjected to strong earthquakes is crucial to a reasonable assessment of the seismic safety of dams. In this paper, the extended finite element method (XFEM) is presented to describe the crack propagation within concrete gravity dams subjected to earthquake loads. Moreover, the interaction between the impounded water and the dam–foundation system is explicitly taken into account by modeling the reservoir water with two-dimensional fluid finite elements in the Lagrangian formulation. In order to validate the proposed algorithm, seismic crack analysis is performed to investigate the failure modes of the Koyna dam–reservoir–foundation system under the 1967 Koyna earthquake. It shows that the cracking damage profile obtained from the proposed XFEM framework agrees well with that reported in the literature. With the validated algorithm, we further apply it to study the potential failure modes of the Guandi concrete gravity dam. Seismic cracking response of concrete gravity dams considering the effects of the dam–reservoir–foundation interaction is obtained through the incremental dynamic analysis (IDA) based XFEM. 40 as-recorded accelerograms with each scaled to 8 increasing intensity levels are selected in this study. Based on the 320 numerical simulation results, typical failure processes and five potential failure modes of concrete gravity dams under the selected database of strong earthquake ground motions are presented.

A new macro-element model encapsulating the dynamic moment–rotation behaviour of raft foundations

The interaction of shallow foundations with the underlying soil during dynamic loading can have both positive and negative effects on the behaviour of the superstructure. Although the negative impacts are generally considered within design codes, seldom is design performed in such a way as to maximise the potential beneficial characteristics. This is, in part, due to the complexity of modelling the soil–structure interaction. Using the data from dynamic centrifuge testing of raft foundations on dry sand, a simple moment–rotation macro-element model has been developed, which has been calibrated and validated against the experimental data. For the prototype tested, the model is capable of accurately predicting the underlying moment–rotation backbone shape and energy dissipation during cyclic loading. Utilising this model within a finite-element model of the structure could potentially allow a coupled analysis of the full soil–foundation–structure system's seismic response in a simplified manner compared to other methods proposed in literature. This permits the beneficial soil–structure interaction characteristics, such as the dissipation of seismic energy, to be reliably included in the design process, resulting in more efficient, cost-effective and safe designs. In this paper the derivation of the model is presented, including details of the calibration process. In addition, an appraisal of the likely resultant error of the model prediction is presented and visual examples of how well the model mimics the experimental data are provided.

Attenuation of ambient vibrations induced in urban buildings

A numerical study of a control system to attenuate the vibrations induced by traffic in buildings is presented herein. Three-dimensional finite-element method numerical models of the structures were built, including the influence of masonry walls and soil–foundation interaction, in order to estimate their dynamic characteristics, as well as time history responses to vibrations induced by the traffic of heavy vehicles. The models were calibrated through correlation with the experimental data obtained with the uncontrolled structure. The description, results and analysis of the extensive experimental measurements constitute a fundamental part of the work and are summarised herein. The responses obtained with the models were used to present alternative solutions to the problem. One of these solutions is composed of prestressed slender steel pipe columns with rubber pads at their tops to be installed in between the floor slabs of the building. The good effectiveness of this solution is demonstrated through numerical simulations.

Thermal postbuckling of nanotube-reinforced composite cylindrical panels resting on elastic foundations

This paper presents an investigation on the thermal postbuckling behavior of nanocomposite cylindrical panels resting on elastic foundations and subjected to a uniform temperature rise. The cylindrical panels are made of carbon nanotube reinforced composite (CNTRC) material with the carbon nanotube reinforcement being distributed along the thickness of the panels either uniformly (UD) or functionally graded (FG). A micromechanical model together with molecular dynamics simulation results is employed to obtain the material properties of the FG-CNTRC panels. The governing equations for the cylindrical panels are based on a higher-order shear deformation theory with a von Kármán-type of kinematic nonlinearity. The panel–foundation interaction and thermal effects are also included. The material properties of CNTRCs are assumed to be temperature-dependent and an iterative scheme is developed to obtain numerical results. The results reveal that the nanotube volume fraction, foundation stiffness, and the panel curvature ratio have a significant effect on the thermal postbuckling behavior of CNTRC cylindrical panels. It is found that in most cases the CNTRC panel with intermediate nanotube volume fraction does not necessarily have intermediate thermal postbuckling strength.

Study of cushioned composite piled raft foundation behaviour under seismic forces

In order to mobilize shallow soil to participate in the interaction of piled raft foundation sufficiently, the concept of piled raft has been modified to new type of foundation named composite piled raft. In the system of composite piled raft, the short piles made of flexible materials were used to strengthen the shallow soft soil, while the long piles made of relatively rigid materials were used to reduce the settlements and the cushion beneath the raft was used to redistribute and adjust the stress ratio of piles to subsoil. Finite element method was applied to study the behaviour of this new type of foundation subjected to seismic forces. This paper focuses on behaviour of various components of foundation system such as long pile, short piles and subsoil under seismic force in subsoil related to Surat city geological condition. A comparative study is done to understand the effect of cushion on axial stresses, shear stresses and shear forces along piles.

Comparison of Results of Analyses the Foundation Slab Calculated by Two FEM Programs

For decades attention has been paid to interaction of foundation structures and subsoil and development of interaction models. Currently there are several software that, can deal with the interaction of foundations and subsoil. The purpose of this paper is to compare resulting deformation of the slab, subsidence of the subsoil, bending moments and contact stress calculated by two different software based on FEM calculations. Calculated deformation of the slab is compared with deformation measured during experiment.

Character Analysis of Balance and Imbalance of Varying Rigidity of Rigid Pile Composite Foundation under Seismic Load

Based on ABAQUS finite element analysis software simulation, the finite element model for dynamic analysis of rigid pile composite foundation and superstructure interaction system is established, which selects the two kinds of models, by simulating the soil dynamic constitutive model, selecting appropriate artificial boundary.The influence of rigid pile composite foundation on balance and imbalance of varying rigidity is analyzed under seismic loads. The result shows that the maximum bending moment and the horizontal displacement of the long pile is much greater than that of the short pile under seismic loads, the long pile of bending moment is larger in the position of stiffness change. By constrast, under the same economic condition, the aseismic performance of of rigid pile composite foundation on balance of varying rigidity is better than that of rigid pile composite foundation on imbalance of varying rigidity.

Effects of foundation soil stiffness on the 3-D modal characteristics and seismic response of a highway bridge

This paper presents the main results of an investigation into the influence of foundation soil stiffness on the modal characteristics and seismic response of a highway bridge with spread foundations. A sensitivity study including six types of soil profiles is first performed to examine the effects of foundation soil stiffness on critical dynamic response parameters of the bridge. 3-D modal characteristics of lateral, vertical, longitudinal and torsional vibrations modes are identified and compared for various soil and rock conditions. The study is then extended to estimate the time history nonlinear seismic response of coupled foundation soil-bridge models utilizing an extension of the Fast Nonlinear Analysis (FNA) algorithm. Two different approaches for modeling soil foundation interaction are considered: a PGA consistent linear soil model and an advanced non linear soil model. Results show, among others, the major influence of soil flexibility effects on the modal characteristics and seismic response behavior of the bridge. Moreover, the results illustrate clearly the importance of soil nonlinearity on coupled foundation soil-bridge response. It follows, from a design perspective, that analytical models used for the seismic analysis of bridge structures should explicitly consider the effects of soil-structure interaction including nonlinear soil behavior.

Postbuckling of FGM cylindrical panels resting on elastic foundations subjected to lateral pressure under heat conduction

A postbuckling analysis is presented for FGM cylindrical panels resting on elastic foundations subjected to lateral pressure under heat conduction. The initial deflections caused by lateral pressure and thermal bending stresses are both taken into account. Material properties of functionally graded materials (FGMs) are assumed to be temperature-dependent, and graded in the thickness direction based on Mori–Tanaka micromechanics model. The formulations are based on a higher order shear deformation theory and von Kármán strain–displacement relationships. The panel–foundation interaction and thermal effects are also included. The governing equations are first deduced to a boundary layer type that includes nonlinear prebuckling deformations and initial geometric imperfections of the panel. These equations are then solved by means of a singular perturbation technique along with a two-step perturbation approach. The effects of volume fraction index, temperature variation, foundation stiffness, as well as panel curvature ratio on the postbuckling behavior of FGM cylindrical panels are discussed in detail.

Nonlinear interaction between wave, breakwater and its loose seabed foundation: A small-scale case

In offshore environment, newly deposited quaternary loose sediments widely exist in the world. Sometimes, coastal engineers cannot avoid choosing these natural loose sediments as the foundation of marine structures. Under this situation, the interaction between ocean wave, marine structures and their loose sand foundation, and the wave-induced pore pressure built-up in loose seabed foundation are the key factors in which coastal engineers would most concern. In this study, the nonlinear interaction mechanism between ocean wave, a composite breakwater and its loose elasto-plastic sand bed foundation is investigated by utilizing a semi-coupled numerical model FSSI-CAS 2D. In the coupled numerical model FSSI-CAS 2D, VARANS equation for wave model, and dynamic Biot׳s equation for soil model are used for the governing equations. The advanced and excellent elasto-plastic constitutive model PZIII proposed by Pastor et al. (1990) is adopted to describe the nonlinear dynamic behavior of loose sand soil under cyclic wave loading. Taking the parameters of Neveda sand determined in the VELACS project funded by NSF as the property parameters for the loose sand bed, a small-scale computational case like the experimental set-up in Mostafa et al. (1999) is taken as a representative case to investigate the wave-structure-loose seabed foundation interaction mechanism. The numerical results indicate that the pore pressure in loose seabed foundation builts up significantly, and the marine structure subsides and tilts under wave loading. The loose sand bed becomes denser and denser due to soil compaction. Parametric studies show that both the wave characteristics and the soil properties can affect the built-up of residual pore pressure in loose seabed foundation.