• Structural Engineering and Mechanics
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• 제20권5호
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• pp.575-587
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• 2005

Using the nonlinear load transfer function for pile side soil and the linear load transfer function for pile end soil, a combined approach of the incremental load transfer matrix method and the approximate differential equation solution method is presented for the nonlinear analysis of interaction between flexible pile group and soil. The proposed method provides an effective approach for the solution of the nonlinear interaction between flexible pile group under rigid platform and surrounding soil. To verify the accuracy of the proposed method, a static load test for a nine-pile group under a rigid platform is carried out. The finite element analysis is also conducted for comparison purposes. It is found that the results from the proposed method match very well with those from the experimental test and are better in comparison with the finite element method.

• 한국지반환경공학회 논문집
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• 제13권3호
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• pp.85-90
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• 2012

본 논문은 ABAQUS 유한 요소 프로그램을 사용하여 다층지반(화강풍화토-점토-화강풍화토)에서의 외말뚝과 군말뚝의 횡하중에 대한 영향을 설명한다. 본 연구에서의 변수는 캡이 없는 외말뚝과 캡이 있는 군말뚝으로, 파일의 직경은 0.5m, 길이는 10m인 말뚝을 사용하였다. 수치 해석은 말뚝의 간격을 (s=3D, 4D, 5D) 변화시켜 외말뚝과 군말뚝의 거동을 비교하기 위하여 수행되었다. $1{\times}3$군말뚝(leading pile, middle pile, trail pile)은 각각의 말뚝의 저항분포와 수평저항력을 조사하기 위하여 선정되었다. 점토의 해석모델은 Druker-Prager 구성관계를 이용하였고, 화강풍화토의 물성치는 기존의 논문을 사용하였으며, 말뚝은 탄성 원형 콘크리트로 모델링하였다. 해석 결과, 말뚝의 간격이 넓어짐에 따라 P-multiplier의 값이 leading pile의 영향을 덜 받는 것으로 나타났다. 또한, 단층지반이 다층지반에 비해 수평저항력이 약 4~20% 크게 작용하는 것으로 나타났다.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
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• pp.443-450
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• 2000

In this study a numerical method for soil-pile interaction analysis buried in multi-layered half planes is presented in frequency domain using FE-BE coupling. The total soil-pile interaction system is divided into two parts so called far field and near field beam elements are used for modeling a pile and coupled with plain strain elements for soil modeling. Boundary element formulation using the multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered dynamic fundamental solution is adopted to the far field and coupled with near field modeled by finite elements. In order to verify the proposed soil-pile interaction analysis method the dynamic responses of a pile on multi-layered half-planes are performed and compared with experiment results. Through this developed method the dynamic response analysis of a pile buried in multi-layered half planes can be calculated effectively in frequency domain.

• Coupled systems mechanics
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• 제1권4호
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• pp.381-395
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• 2012

Dynamic response of Pile Supported Structures is highly depended on Soil Pile Structure Interaction. In this paper, by comparison of experimental and numerical dynamic responses of a prototype jacket offshore platform for both hinge based and pile supported boundary conditions, effect of soil-pile-structure interaction on dynamic characteristics of this platform is studied. Jacket and deck of a prototype platform is installed on a hinge-based case first and then platform is installed on eight skirt piles embedded on continuum monolayer sand. Dynamic characteristics of platform in term of natural frequencies, mode shapes and modal damping are compared for both cases. Effects of adding and removing vertical bracing members in top bay of jacket on dynamic characteristics of platform for both boundary conditions are also studied. Numerical simulation of responses for the studied platform is also performed for both mentioned cases using capability of ABAQUS and SACS software. The 3D model using ABAQUS software is created using solid elements for soil and beam elements for jacket, deck and pile members. Mohr-Coulomb failure criterion and pile-soil interface element are used for considering nonlinear pile soil structure interaction. Simplified modeling of soil-pile-structure interaction effect is also studied using SACS software. It is observed that dynamic characteristics of the system changes significantly due to soil-pile-structure interaction. Meanwhile, both of complex and simplified (ABAQUS and SACS, respectively) models can predict this effect accurately for such platforms subjected to dynamic loading in small range of deformation.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1999년도 봄 학술발표회 논문집
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• pp.259-266
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• 1999

In case that pile cap is in direct contact with underlying soil, the bearing mechanism for pile groups, including direct bearing effect of cap and its induced influence on pile-soil-cap interaction, should be properly considered. In this paper, the effects of pile caps on behaviors of pile groups in sandy soils were investigated by model tests, which consist of tests on 3 by 3 pile groups with/without contact on subsoil, single pile with/without contact and cap as a shallow foundation. Also, the influences of pile spacing in group piles on contact effects were investigated. The test results showed that the load carrying capacity of pile cap was large enough not to be ignored. However, the interaction effects due to contact between cap and subsoils were not revealed obviously in working load range. And in the design of pile groups, the bearing effect of pile cap when contacted with subsoils, can be reflected by simply summing up load settlement behaviors of each cap and group piles without contact.

• Geomechanics and Engineering
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• 제31권2호
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• pp.209-222
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• 2022

Finite element analyses using coupled Eulerian-Lagrangian technique are performed to investigate the effect of soil conditions on plugging of open-ended piles in sands. Results from numerical simulations are compared against the data from field load tests on three open-ended piles and show very good agreement. A parametric study focusing on determination of the coefficient of lateral earth pressure (K) in soil plug after pile driving are then performed for various soil densities, end-bearing conditions, and layering conditions. Results from the parametric study suggest that the K value in the soil plug - and hence the degree of soil plugging - increases with increasing soil densities. The analysis results further show that the K value within the soil plug can reach about 63 to 71% of the coefficient of passive earth pressure after pile driving. For layered soil profiles, the greater K values are achieved after pile driving when the denser soil layer is present near the pile base regardless of number of soil layers. This study provides comprehensive numerical and experimental data that can be used to develop advanced theory for analysis and design of open-ended pipe piles, especially for estimation of inner shaft resistance after pile driving.

• 한국터널지하공간학회 논문집
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• 제14권4호
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• pp.337-356
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• 2012

본 연구에서는 3차원 유한요소해석을 실시하여 사용 중인 단독말뚝 및 군말뚝의 측면에서 실시된 터널굴착에 의한 말뚝의 거동을 분석하였다. 수치해석에서는 터널굴착으로 유발된 말뚝-지반 경계면에서의 전단응력전이를 미끄러짐(slip)을 고려할 수 있는 접촉요소(interface element)를 이용하여 분석하였다. 본 연구는 말뚝-지반경계면에서의 전단응력, 말뚝의 축력 및 지반 및 말뚝의 변형에 대한 분석을 포함한다. 탄성이론에 근거한 기존의 연구는 말뚝의 거동에 영향을 미치는 주요인자들을 적절히 고려하지 못하여 말뚝의 거동을 명확하게 분석할 수 없는 것으로 나타났다. 터널굴착으로 유발된 말뚝-지반 사이에서의 전단응력전이로 인하여 말뚝인접 지반의 전단응력 및 말뚝의 축력분포가 크게 변하는 것으로 나타났는데, 터널 springline 상부에서는 하향의 마찰력이 발생하였으며, 그 하부에서는 상향의 저항력이 발현되어 말뚝에는 압축력이 발생하였다. 경계면에서의 전단응력 발현정도는 말뚝-지반의 상호거동에 가장 큰 영향을 미치는 것으로 분석되었다. 군말뚝의 축력분포에 대한 분석결과 단독말뚝에 비해 터널굴착의 영향을 덜 받는 것으로 나타났다. 터널굴착으로 유발된 말뚝의 침하와 관련된 말뚝의 겉보기 지지력 감소는 크지 않은 것으로 분석되었다.

• Structural Engineering and Mechanics
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• 제49권1호
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• pp.95-110
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• 2014

The study deals with physical modeling of space frame-pile foundation and soil system using finite element models. The superstructure frame is analyzed using complete three-dimensional finite element method where the component of the frame such as slab, beam and columns are descretized using 20 node isoparametric continuum elements. Initially, the frame is analyzed assuming the fixed column bases. Later the pile foundation is worked out separately wherein the simplified models of finite elements such as beam and plate element are used for pile and pile cap, respectively. The non-linear behaviour of soil mass is incorporated by idealizing the soil as non-linear springs using p-y curve along the lines similar to that by Georgiadis et al. (1992). For analysis of pile foundation, the non-linearity of soil via p-y curve approach is incorporated using the incremental approach. The interaction analysis is conducted for the parametric study. The non-linearity of soil is further incorporated using iterative approach, i.e., secant modulus approach, in the interaction analysis. The effect the various parameters of the pile foundation such as spacing in a group and configuration of the pile group is evaluated on the response of superstructure owing to non-linearity of the soil. The response included the displacement at the top of the frame and bending moment in columns. The non-linearity of soil increases the top displacement in the range of 7.8%-16.7%. However, its effect is found very marginal on the absolute maximum moment in columns. The hogging moment decreases by 0.005% while sagging moment increases by 0.02%.

• Coupled systems mechanics
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• 제1권1호
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• pp.1-7
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• 2012

The problem of laterally loaded piles is particularly a complex soil-structure interaction problem. The flexural stresses developed due to the combined action of axial load and bending moment must be evaluated in a realistic and rational manner for safe and economical design of pile foundation. The paper reports the finite element analysis of pile groups. For this purpose simplified models along the lines similar to that suggested by Desai et al. (1981) are used for idealizing various elements of the foundation system. The pile is idealized one dimensional beam element, pile cap as two dimensional plate element and the soil as independent closely spaced linearly elastic springs. The analysis takes into consideration the effect of interaction between pile cap and soil underlying it. The pile group is considered to have been embedded in cohesive soil. The parametric study is carried out to examine the effect of pile spacing, pile diameter, number of piles and arrangement of pile on the responses of pile group. The responses considered include the displacement at top of pile group and bending moment in piles. The results obtained using the simplified approach of the F.E. analysis are further compared with the results of the complete 3-D F.E. analysis published earlier and fair agreement is observed in the either result.

• Interaction and multiscale mechanics
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• 제3권1호
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• pp.55-79
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• 2010

The effect of soil-structure interaction on a single-storey, two-bay space frame resting on a pile group embedded in the cohesive soil (clay) with flexible cap is examined in this paper. For this purpose, a more rational approach is resorted to using the finite element analysis with realistic assumptions. Initially, a 3-D FEA is carried out independently for the frame on the premise of fixed column bases in which members of the superstructure are discretized using the 20-node isoparametric continuum elements. Later, a model is worked out separately for the pile foundation, by using the beam elements, plate elements and spring elements to model the pile, pile cap and soil, respectively. The stiffness obtained for the foundation is used in the interaction analysis of the frame to quantify the effect of soil-structure interaction on the response of the superstructure. In the parametric study using the substructure approach (uncoupled analysis), the effects of pile spacing, pile configuration, and pile diameter of the pile group on the response of superstructure are evaluated. The responses of the superstructure considered include the displacement at top of the frame and moments in the columns. The effect of soil-structure interaction is found to be quite significant for the type of foundation considered in the study. Fair agreement is observed between the results obtained herein using the simplified models for the pile foundation and those existing in the literature based on a complete three dimensional analysis of the building frame - pile foundation - soil system.