Modeling of Piled Foundations

1982 ◽  
Vol 22 (05) ◽  
pp. 775-783
Author(s):  
Glenn A. Kriger
Keyword(s):  
Linear Models ◽  
Pile Group ◽  
Group Behavior ◽  
Model Construction ◽  
Single Pile ◽  
Pile Groups ◽  
Model Synthesis ◽  
Construction Methods ◽  
Single Piles ◽  
Piled Foundations

Abstract A comprehensive set of guidelines for constructing linear models of single piles and pile groups for foundations of offshore structures is presented. These models are used as boundary conditions at the base of the superstructure, thus permitting independent analysis of the superstructure from its supporting foundation.This paper is a "how-to" text for piled foundation modeling. It is also of value to those in related disciplines, such as geotechnical specialists, who will gain insight into how their data is applied in analyzing structures supported by piled foundations. Discussions include the behavior and modeling of single piles and pile groups. Construction methods are presented for pile groups. Construction methods are presented for three types of pile models-matrix, springs, and equivalent pile. The advantages and disadvantages of each model type are described. Linear and nonlinear foundation behavior characteristics are treated in depth. Factors that influence the approach to a modeling problem are outlined. Emphasis is placed on providing the problem are outlined. Emphasis is placed on providing the reader with an understanding of the physical behavior of piled foundations and model construction. A step-by-step piled foundations and model construction. A step-by-step procedure for model synthesis is provided in an example. procedure for model synthesis is provided in an example. Introduction In a fixed offshore platform, the steel jacket superstructure and its supporting piled foundation are more conveniently analyzed if treated separately. There are major structural and behavior-al differences between the jacket and foundation, and the two do not lend themselves to similar analytical methods. This paper presents basic techniques for constructing linear models that simulate the foundation behavior at the superstructure/foundation boundary. Use of these models permits independent superstructure analyses. Selection of the model type and its degree of refinement are described from a global overview of the structure, available data, and ramification of analytical results. Construction of the foundation simulation model follows routine procedures using results of an independent foundation analysis. Single Pile Behavior The load-deflection behavior of a single pile crown is of key importance in model construction. Analysis of a pile embedded in soil is extremely difficult because of pile embedded in soil is extremely difficult because of the infinite dimensions, nonhomogeneity, and nonlinearity of the soil. As a practical necessity, the problem usually is simplified by treating the pile as a beam-column supported by nonlinear axial and lateral soil springs. Details of these analytical procedures are beyond the scope of this work, although application of the techniques presented here will require the availability of such an analytical tool. Although this material pertains to single piles, it forms the basis for understanding pertains to single piles, it forms the basis for understanding pile group behavior discussed later. pile group behavior discussed later. Fig. 1 depicts a right-hand orthogonal coordinate system, which is used throughout this paper. Displacements, s, and forces, F, are shown in each of the six degrees of freedom (DOF). The pile behavior is studied by observation of the force(s) required to produce displacement in each of the six DOF while all other displacements are held at zero. Of utmost importance is the effect of coupling-the interaction of forces (and displacements) in different DOF.First consider linear pile behavior, which is characteristic of small-magnitude loadings. Force and displacement are directly proportional; therefore, stiffness (force divided by displacement) remains constant for all values of displacement (Fig. 2).Fig. 3a shows that an axial displacement is produced by an axial force. This axial displacement requires no other forces in each of the remaining five DOF. Therefore, linear axial pile behavior is uncoupled. Similarly, a torsional displacement (Fig. 3b) requires only a torque along the same DOF and therefore is also lineally uncoupled. SPEJ p. 775

Dynamic analysis of laterally loaded pile groups in sand and clay

2002 ◽  
Vol 39 (6) ◽  
pp. 1358-1383 ◽  
Author(s):  
Yasser E Mostafa ◽  
M Hesham El Naggar
Keyword(s):  
Dynamic Loading ◽  
Dynamic Load ◽  
Load Transfer ◽  
Pile Group ◽  
Nonlinear Behaviour ◽  
Single Pile ◽  
Offshore Platforms ◽  
Group Effect ◽  
Pile Groups ◽  
Pile Head

Pile foundations supporting bridge piers, offshore platforms, and marine structures are required to resist not only static loading but also lateral dynamic loading. The static p–y curves are widely used to relate pile deflections to nonlinear soil reactions. The p-multiplier concept is used to account for the group effect by relating the load transfer curves of a pile in a group to the load transfer curves of a single pile. Some studies have examined the validity of the p-multiplier concept for the static and cyclic loading cases. However, the concept of the p-multiplier has not yet been considered for the dynamic loading case, and hence it is undertaken in the current study. An analysis of the dynamic lateral response of pile groups is described. The proposed analysis incorporates the static p–y curve approach and the plane strain assumptions to represent the soil reactions within the framework of a Winkler model. The model accounts for the nonlinear behaviour of the soil, the energy dissipation through the soil, and the pile group effect. The model was validated by analyzing the response of pile groups subjected to lateral Statnamic loading and comparing the results with field measured values. An intensive parametric study was performed employing the proposed analysis, and the results were used to establish dynamic soil reactions for single piles and pile groups for different types of sand and clay under harmonic loading with varying frequencies applied at the pile head. "Dynamic" p-multipliers were established to relate the dynamic load transfer curves of a pile in a group to the dynamic load transfer curves for a single pile. The dynamic p-multipliers were found to vary with the spacing between piles, soil type, peak amplitude of loading, and the angle between the line connecting any two piles and the direction of loading. The study indicated the effect of pile material and geometry, pile installation method, and pile head conditions on the p-multipliers. The calculated p-multipliers compared well with p-multipliers back-calculated from full scale field tests.Key words: lateral, transient loading, nonlinear, pile–soil–pile interaction, p–y curves, Statnamic.

Some Recent Research on the Bearing Capacity of Foundations

1963 ◽  
Vol 1 (1) ◽  
pp. 16-26 ◽  
Author(s):  
George Geoffrey Meyerhof
Keyword(s):  
Bearing Capacity ◽  
Model Tests ◽  
Vertical Load ◽  
Pile Groups ◽  
Free Standing ◽  
Flexible Foundations ◽  
Inclined Loads ◽  
Single Piles ◽  
Piled Foundations

The first part of the paper summarizes the results of recent research on the bearing capacity of spread foundations of various shapes under a central vertical load and outlines the effects of foundation depth, eccentricity and inclination of the load. Simple formulae have been derived for use in practice and their application to the design of rigid and flexible foundations is briefly indicated.The second part of the paper discusses the bearing capacity of single piles under vertical and inclined loads. The bearing capacity of piled foundations and free-standing pile groups is outlined, and the results of model tests on pile groups under central and eccentric loads are briefly analysed in relation to some problems in practice.

Stiffness constants and interaction factors for vertical response of pile groups

1990 ◽  
Vol 27 (6) ◽  
pp. 813-822 ◽  
Author(s):  
Bahaa El Sharnouby ◽  
Milos Novak
Keyword(s):  
Group Analysis ◽  
Pile Group ◽  
Soil Parameters ◽  
Pile Groups ◽  
Continuous Transition ◽  
Interaction Factor ◽  
Wide Range ◽  
Interaction Factors ◽  
New Type ◽  
Single Piles

Stiffness constants and flexibility coefficients of single piles and interaction factors are presented to facilitate the analysis of pile groups subjected to static vertical loads. A continuous transition from friction to end-bearing piles is accounted for. A new type of interaction factor, established from subgroups of five piles, is introduced for end-bearing piles. This interaction factor allows for the stiffening effect of the piles occurring between the two reference piles. This feature improves the accuracy of group analysis for end-bearing piles. Numerical results for axially loaded single piles and pile groups are presented for a wide range of pile and soil parameters. The results are applicable toboth rigid and flexible caps. Key words: piles, pile group, settlement, interaction

Prediction of the horizontal load-displacement curves of pile groups based on the results of single pile tests

2000 ◽  
Vol 37 (5) ◽  
pp. 951-962 ◽  
Author(s):  
António GF de Sousa Coutinho
Keyword(s):  
Pile Group ◽  
Full Scale ◽  
Soil Parameters ◽  
Single Pile ◽  
Horizontal Load ◽  
Pile Groups ◽  
Nonlinear Method ◽  
Pile Test ◽  
Elastic Plastic ◽  
Load Displacement

This paper presents the prediction of horizontal load-displacement curves of pile groups based on the results of single pile tests. Although the same basic model is employed, two different approaches are taken: one assumes soil to be linear elastic-plastic, and the other assumes it to be elastic nonlinear. The model is calibrated on the basis of the results of a full-scale single pile test. Special emphasis is placed on model calibrations, since the success of any prediction method depends on a careful characterization of the soil. Some new approaches for determining the soil parameters are presented. Two methods for predicting load-displacement curves, one from each model approach, are then proposed and discussed. Special emphasis is placed on group efficiency in the elastic-plastic method and on the boundary conditions of the single pile and the pile group in the elastic nonlinear method. Using the soil characteristics from the model calibrations, the load-displacement curves for a given pile group are then predicted. These predictions are compared with the results of a full-scale pile group test carried out at the same site as that of the single pile test. Agreement between the predictions and the test results tends to validate the methods proposed.Key words: displacement predictions, pile groups, model calibration, pile tests.

scholarly journals Experimental Investigation on Efficiency Factor of Pile Groups Regarding Distance of Piles

2019 ◽  
Vol 5 (8) ◽  
pp. 1812-1819
Author(s):  
Mojtaba Pashayan ◽  
Gholam Moradi
Keyword(s):  
Axial Loading ◽  
Pile Group ◽  
Group Behavior ◽  
Efficiency Factor ◽  
Diameter Ratio ◽  
Efficiency Coefficient ◽  
Continuous Change ◽  
Pile Groups ◽  
Shaft Resistance ◽  
The Impact

There are a lot of the parameters which affect pile group behavior in soil. One of these factors is the distance of piles from each other. The impact of distance on pile groups in sand has been investigated through some researches, whereas most of them have not represented an exact estimation according to the continuous change of the distance in sand. Moreover, most of previous investigations have considered two piles as a perfect group. Since two-pile group has the least interaction effect among piles, it cannot suitably demonstrate the influence of spacing. In this lecture, several 4-pile groups modeled with different spacing were subjected to axial loading in laboratory. The pile groups were free-head with length to diameter ratio of 13.5. The piles are designed in a way which the shaft resistance of piles can be completely mobilized through the test. Then, the bearing capacities of pile groups are measured and compared with the single pile's resistance in order to calculate the efficiency coefficient of the groups. It is revealed that the distance is noticeably effective in efficiency factor and this effectiveness, non-linearly decreases by increase of spacing. The results show that the efficiency coefficient is changing between almost 1 and 1.4.

scholarly journals Large-scale model tests of a single pile and two-pile groups for an offshore platform in sand

2021 ◽  
Author(s):  
Aligi Foglia ◽  
Khalid Abdel-Rahman ◽  
Elmar Wisotzki ◽  
Tulio Quiroz ◽  
Martin Achmus
Keyword(s):  
Large Scale ◽  
Load Transfer ◽  
Pile Group ◽  
Scale Model ◽  
Single Pile ◽  
Pile Groups ◽  
Group Efficiency ◽  
Large Scale Model ◽  
Load Tests ◽  
The Given

Estimating pile group efficiency for open-ended steel piles in small group arrangements is a challenging task for designers. This paper reports on the large-scale experimental campaign performed for the BorWin gamma offshore converter platform, which involved single piles and two-pile group systems on a scale of 1:10. The experimental works included installation, dynamic end-of-driving tests, dynamic restrike tests, and static load tests of a single pile and a pair of two-pile groups in densely compacted, artificially prepared homogeneous sand. The CPT profiles and the blow counts confirmed that the foundation systems are comparable to each other. The experimental results of the single pile system were compared with conventional design methods. Such comparison indicated that CPT-based methods and load-transfer methods are applicable at the considered model scale. The bearing capacity prediction obtained via the CAPWAP method is conservative with respect to the static capacity. A consistent setup effect can be detected by analyzing the complete dynamic loading session. The pile group efficiency for the given foundation system was found to be less than 1.0 at both very small and very large soil strains, while it equaled 1.0 at failure.

Flexibility coefficients and interaction factors for pile group analysis

1986 ◽  
Vol 23 (4) ◽  
pp. 441-450 ◽  
Author(s):  
Bahaa El Sharnouby ◽  
Milos Novak
Keyword(s):  
Load Distribution ◽  
Group Analysis ◽  
Vertical Plane ◽  
Ground Surface ◽  
Pile Group ◽  
Lateral Loads ◽  
Pile Groups ◽  
Group Evaluation ◽  
Interaction Factors ◽  
Single Piles

Flexibility coefficients of single piles and interaction factors established for groups of two piles are presented to facilitate analysis of arbitrary pile groups exposed to static horizontal loads. Such an analysis may yield pile group flexibility, stiffness, deflection, and distribution of loads on individual piles. The data given are complete in that they include horizontal translation, rotation in the vertical plane, and cross effects between the two, making it possible to establish complete stiffness and flexibility matrices of pile groups provided with either rigid caps or arbitrarily flexible caps. Homogeneous, parabolic, and linear (Gibson's) soil profiles are considered and the piles may have a free length sticking above the ground surface. The methods of group evaluation based on superposition of interaction factors are reviewed and compared and numerical examples are given. Key words: piles, pile groups, lateral loads, flexibility, stiffness, load distribution.

Cyclic axial behaviour of piles and pile groups in sand

2012 ◽  
Vol 49 (9) ◽  
pp. 1074-1087 ◽  
Author(s):  
Zheming Li ◽  
Malcolm D. Bolton ◽  
Stuart K. Haigh
Keyword(s):  
Axial Load ◽  
Pile Group ◽  
Offshore Structures ◽  
Pile Groups ◽  
Axial Loads ◽  
Bored Pile ◽  
Load Cycling ◽  
Permanent Settlement ◽  
Number Of Cycles ◽  
Piled Foundations

Piled foundations are often subjected to cyclic axial loads. This is particularly true for the piles of offshore structures, which are subjected to rocking motions caused by wind or wave actions, and for those of transport structures, which are subjected to traffic loads. As a result of these cyclic loads, excessive differential or absolute settlements may be induced during the piles’ service life. In the research presented here, centrifuge modelling of single piles and pile groups was conducted to investigate the influence of cyclic axial loads on the performance of piled foundations. The influence of installation method was investigated and it was found that the cyclic response of a pile whose jacked installation was modelled correctly is much stiffer than that of a bored pile. During displacement-controlled axial load cycling, the pile head stiffness reduces with an increasing number of cycles, but at a decreasing rate; during force-controlled axial load cycling, more permanent settlement is accumulated for a bored pile than for a jacked pile. The performance of individual piles in a pile group subjected to cyclic axial loads is similar to that of a single pile, without any evident group effect. Finally, a numerical analysis of axially loaded piles was validated by centrifuge test results. Cyclic stiffness of soil at the base of pre-jacked piles increases dramatically, while at base of jacked piles it remains almost constant.

scholarly journals LOAD-SETTLEMENT BEHAVIOUR OF MODEL PILE GROUPS IN SAND UNDER VERTICAL LOAD

2017 ◽  
Vol 23 (8) ◽  
pp. 1148-1163 ◽  
Author(s):  
Mauricio Martines SALES ◽  
Monica PREZZI ◽  
Rodrigo SALGADO ◽  
Yoon Seok CHOI ◽  
Jintae LEE
Keyword(s):  
Pile Group ◽  
Single Pile ◽  
Load Testing ◽  
Driven Piles ◽  
Pile Groups ◽  
Pile Installation ◽  
Model Pile ◽  
Group Configuration ◽  
Settlement Behaviour ◽  
Good Agreement

Model pile load testing is effective to study the load-settlement behaviour of pile foundations given the con­trolled environment in which the testing is done. This paper reports a testing program in a large calibration chamber involving individual piles and pile groups installed in sand samples of three different densities. Tests on both nondis­placement and driven piles are evaluated to assess the influence of the pile installation process on pile load-settlement response. A method is proposed to predict the load-settlement response of a pile group based on the response of a single pile. The method is shown to produce estimates that are in good agreement with measurements. The influence of pile group configuration, pile spacing, soil density and method of pile installation is discussed.

Geometrical effects on the load transfer mechanism of pile groups: three-dimensional numerical analysis

2018 ◽  
Vol 55 (5) ◽  
pp. 749-757 ◽  
Author(s):  
Yaru Lv ◽  
Dongdong Zhang
Keyword(s):  
Load Transfer ◽  
Three Dimensional ◽  
Bending Moment ◽  
Pile Group ◽  
Transfer Mechanism ◽  
Single Pile ◽  
Pile Groups ◽  
Load Transfer Mechanism ◽  
Side Resistance ◽  
Geometrical Effects

This paper investigates geometrical effects on the load transfer mechanism of off-ground capped pile groups subjected to vertical load by four three-dimensional numerical simulations, including a circular single pile, an X-shaped cross-sectional concrete (XCC) single pile, a 4 × 4 circular pile group, and a 4 × 4 XCC pile group. The ultimate bearing capacities of the XCC and circular piles within pile groups are approximately 0.86 and 0.74 times that of the XCC and circular single piles, respectively. The group efficiency of the XCC pile group is mainly improved by its side resistance. Comparing the XCC pile group to the circular pile group, the increment in side resistance is almost larger than the increment in pile perimeter, indicating that the pile geometry alters the load transfer mechanism via stress concentration and lateral stress arching. A nonuniform load distribution on piles within a capped pile group causes a bending moment along the pile shafts. The bending moment of XCC piles is smaller than that of circular piles because the raft stiffness of an XCC pile group is increased by its larger circumscribing pile diameter.

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