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The seismic response of pile-supported offshore structures is strongly affected by the nonlinear behavior of the supporting piles. Nonlinear response of piles is the most important source of potentially nonlinear dynamic response of offshore platforms due to earthquake excitations. It is often necessary to perform dynamic analysis of offshore platforms that accountsfor soil nonlinearity, discontinuity condition at pile soil interfaces, energy dissipation through soil radiation damping and structural non linear behaviors of piles.In this paper, an attempt is made to develop an inexpensive and practical procedure compatible with readily available structural analysis software for estimating the lateral response of flexible piles embedded in layered soil deposits subjected to seismic loading. In the proposed model a BNWF (Beam on Nonlinear Winkler Foundation) approach is used consisting of simple nonlinear springs, dash pots and contact elements. Gapping and caving-in conditions at the pile-soil interfaces are also considered using special interface elements. This model was incorporated into a Finite Element program (ANSYS), which was used to compute the response of laterally excited piles. A linear approach was used for seismic free field ground motion analysis. The computed responses compared well with the Centrifuge test results.This paper deals with the effects of free field ground motion analysis on seismic non linear behavior of embedded piles. Different parts of a BNWF (Beam on Nonlinear Winkler Foundation) model, together with quantitative and qualitative findings and conclusions for dynamic nonlinear response of offshore piles, are discussed and addressed in detail. The proposed BNWF model (only using the existing features of the available general finite element software) could easily be implemented in a more comprehensive model of nonlinear seismic response analysis of pile supported offshore platforms.

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A finite-difference based continuum numerical model is developed for the pile-soil dynamic response during pile driving. The model is capable of simulating the wave propagation analysis along the pile shaft and through the soil media. The pile-soil media, loading and boundary conditions are such that axisymmetric assumption seems to be an optimized choice to substantially reduce the analysis time and effort. The hydrostatic effect of water is also considered on the effective stresses throughout the soil media and at the pilesoil interface. The developed model is used for signal matching analysis of a well-documented driven pile. The results showed very good agreement with field measurements. It is found that the effect of radiation damping significantly changes the pile-soil stiffness due to the hammer blow. The pile tip response shows substantial increase in soil stiffness below and around the pile tip due to driving efforts.

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This paper presents the numerical analysis of seismic soil-pile-superstructure interaction in soft clay using free-field soil analysis and beam on Winkler foundation approach. This model is developed to compute the nonlinear response of single piles under seismic loads, based on one-dimensional finite element formulation. The parameters of the proposed model are calibrated by fitting the experimental data of largescale seismic soil-pile-structure tests which were conducted on shaking table in UC Berkeley. A comparative evaluation of single piles shows that the results obtained from the proposed procedure are in good agreement with the experimental results.

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The pile-raft foundation is a combination of a raft foundation with piles. Pile-raft foundation has been widely designed, assuming all structure loads to be transferred to piles without considering contribution of the load taken by contact surface between raft and soil. Methods of analysis currently used in practice are based upon relatively conservative assumptions of soil behavior or on the less realistic soil-structure interaction. In this study the bearing -settlement behavior of combined pile-raft foundations on medium dense sand was investigated. 1g physical model test was performed on a circular rigid raft underpinned with four model piles. Numerical simulation was also carried out on the model test, using FLAC-3D, to show compatibility of the numerical analysis with the test. The obtained results showed very good accuracy of the numerical method used in this study as long as the applied load does not exceed the working load, while the performance of numerical model was relatively good for the loads beyond working load.

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It has been realized that the raft (mat) foundations are capable of bearing very large loads when they are assisted with a pile
group. The contribution of both raft and piles to carry the surcharge loads is taken into account, considering the stiffness and
strength of involved elements in the system, i.e. piles, raft and surrounding soil. The piles are usually required not to ensure the
overall stability of the foundation but to act as settlement reducers. There is an alternative design in which, the piles are nonconnected
from the raft to reduce the settlement, which are then known to be "settlement reducer non-connected piles" to increase
the system stiffness. In this paper, two and three dimensional finite element analysis of connected and non-connected pile-raft
systems are performed on three case studies including a 12-storey residential building in Iran, a 39-storey twin towers in
Indonesia, and the Messeturm tower, 256m high, in Frankfurt, Germany. The analyses include the investigation of the effect of
different parameters, e.g. piles spacing, embedment length, piling configuration and raft thickness to optimize the design. The role
of each parameter is also investigated. The parametric study results and comparison to a few field measurements indicate that
by concentrating the piles in the central area of the raft foundation the optimum design with the minimum total length of piles is
achieved, which is considered as control parameter for optimum design. This can be considered as a criterion for project cost
efficiency. On the other hand, non-connected piled-raft systems can significantly reduce the settlements and raft internal bending
moments by increasing the subsoil stratum stiffness. Finally, the comparison indicates that simple and faster 2D analysis has
almost similar results to the time consuming and complicated 3D analysis.

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Pile foundations are frequently used in industrial projects in southwest lowlands of Iran. Although high setup of shaft resistance

is usually reported in the area, no reliable formulation or guidelines are available for considering the increased capacity in design

applications. Therefore, the pile design practices are usually not optimized. The main objective of this paper is presenting a site

specific formulation for setup effects of a utility plant in southwest Iran in which a good database of prestressed concrete driven

piles is available. Fajr-II Petrochemical site in PetZone of Mahshahr accommodating a utility plant is selected as the database of

the current study. The setup factor (A) and the reference time (t0) are evaluated through processing of a relatively large database

of this well-supervised piling project. As the main portion of variations of driven piles capacity with time is related to shaft, only

shaft resistance variations are considered in this research. The shaft capacity variations are derived from signal matching analysis

on PDA tests. Reliability of PDA tests has been confirmed through comparing with the static load test results. Influence of driving

the surrounding piles on setup factor is also investigated. The results show that the average setup factor (A) and the reference time

(t0) of 0.30 and 0.01 day, respectively, are proper values for estimating the long term capacity in this region. Evaluation of the

results indicates that driving 8 piles around the test pile has increased the “A” factor average of 40% resultingin increase of the

shaft capacity about 19% in one month and 22% in one year, in comparison with the tested piles with no surrounding piles driven.

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Piles or drilled shafts used in bridge foundation, waterfronts, and high rise buildings are generally subjected to lateral loads. In order to study the effect of concrete pile geometry on the structural behavior in layered soils, several models with different shapes and dimensions for piles and different properties for two soil layers with variable thickness were selected and analyzed using the finite difference method. The performance of piles situated in layered granular soil with different compaction and thicknesses were studied in two cycles of lateral loading and unloading. The applied finite difference procedure is also validated based on experimental and published results. The pile head displacement of different models due to their overall deformation and rotation were calculated under maximum loading. For a comparison of pile head displacement due to their overall deformation and rotation in different models, the "performance index” is defined as the ratio of “displacement due to deformation” to the “total displacement”.

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Three common approaches to determine the axial pile capacity based on static analysis and in-situ tests are presented, compared and evaluated. The Unified Pile Design (UPD), American Petroleum Institute (API) and a SPT based methods were chosen to be validated. The API is a common method to estimate the axial bearing capacity of piles in marine environments, where as the others are currently used by geotechnical engineers. Seventy pile load test records performed in the northern bank of Persian Gulf with SPT profile have been compiled for methods evaluation. In all cases, pile capacities were measured using full scale static compression and/or pull out loading tests. As the loading tests in some cases were in the format of proof test without reaching the plunging or ultimate bearing capacity, for interpretation the results, offset limit load criteria was employed. Three statistical and probability based approaches in the form of a systematic ranking, called Rank Index, RI, were utilized to evaluate the performance of predictive methods. Wasted Capacity Index (WCI) concept was also applied to validate the efficiency of current methods. The evaluations revealed that among these three predictive methods, the UPD is more accurate and cost effective than the others.

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A simplified approach for nonlinear analysis of the load-displacement response of a single pile and a pile group is presented using the load-transfer approach. A hyperbolic model is used to capture the relationship between unit skin friction and pile-soil relative displacement developed at the pile-soil interface and the load-displacement relationship developed at the pile end. As to the nonlinear analysis of the single pile response, a highly effective iterative computer program is developed using the proposed hyperbolic model. Furthermore, determinations of the parameters related to the hyperbolic model of an individual pile in a pile group are obtained considering interactions between piles. Based on the determinations of the parameters presented in the hyperbolic model of an individual pile in a pile group and the proposed iterative computer program developed for the analysis of the single pile response, the conventional load-transfer approach can then be extended to the analysis of the load-settlement response of an arbitrary pile in a pile group. Comparisons of the load-settlement response demonstrate that the proposed method is generally in good agreement with the field-observed behavior and the calculated results derived from other approaches.

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Driven Precast Reinforced Concrete Piles (DPRCP) is extensively used as a foundation for bridges constructed over canals in Egypt in order to avoid the diversion of water canals. The objectives of this research include identifying the main activities of DPRCP execution in the bridge-construction industry in Egypt and the risk factors affecting them. In addition, assessment of the effects of these risk factors on the quality of activities of DPRCP. Four activities are identified in order to execute the process of construction of DPRCP. These activities include: preparing and casting piles, positioning piles and steering the driving machine, handling piles, and driving piles. Thirty one risk factors affecting the DPRCP activities execution are identified. A survey was executed in Egypt concerning probabilities of occurrence of these factors and their impacts on the quality of activities of DPRCP. In addition, a new membership function is introduced to represent the quality of activities and used in a fuzzy model for factors assessment. Results showed that the proposed membership function can be used effectively to assess the quality of activities associated with the construction of DPRCP. A list of risk factors is highlighted to show the most critical risk factors that help in preparing the quality management plan for the upcoming similar projects. The gentile distribution of data obtained for the different activities proved that the investigated risk factors for the DPRCP in this study are significant.

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In this paper, different aspects of the behavior of 2×2 pile groups under liquefaction-induced lateral spreading in a 3-layer soil profile is investigated using large scale 1-g shake table test. Different parameters of the response of soil and piles including time-histories of accelerations, pore water pressures, displacements and bending moments are presented and discussed in the paper. In addition, distribution of lateral forces due to lateral spreading on individual piles of the groups is investigated in detail. The results show that total lateral forces on the piles are influenced by the shadow effect as well as the superstructure mass attached to the pile cap. It was also found that lateral forces exerted on the piles in the lower half of the liquefied layer are significantly larger than those recommended by the design code. Based on the numerical analyses performed, it is shown that the displacement based method is more capable of predicting the pile group behavior in this experiment comparing to the force based method provided that the model parameters are tuned.

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This research examines the behavior of soil-reinforced piles and applied loads based on the analytical method and by using the numerical results of FLAC3D software for comparison with the analytical results. The analysis was based on a method called virtual retaining wall, the following into consideration: an imaginary retaining wall that passes the footing edge the bearing capacity of footing on reinforced soil with piles, which was determined by applying equilibrium between active and passive forces on virtual wall and a pile row that exists beneath the shallow foundation. To calculate the lateral pile resistance here, an analytical equation was then required. The main objective of this paper is to determine the percentage of applied load on pile. Similarly, the effect of adding pile in various positions relative to the present footing (underpinning) was studied in this research. The various parameters of this study included pile length, vertical distance of pile head to shallow footing, pile distance to center of footing and location of the pile. Finally, the findings were compared with the numerical results of FLAC3D and the formerly presented experimental results. Results show that the analytical method, while being close to other methods is more conservative.

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Stabilization of earth slopes with various proposed methods is one of the important concerns of geotechnical engineering. In this practice, despite numerous developments, design conservativeness and high costs of stabilization are the issues yet to be addressed. This paper not only deals with pile location optimization but also studies the effects of the pile length by using line segments slip surface (non-circular). Taking into account the line segments slip surface in stabilization of earth slopes is a new topic which has been addressed in this paper. The line segments slip surface is actual slip surface and for determining the pile location it can lead to the actual length of the pile. The line segments critical slip surface is obtained by using the Alternating Variable Local Gradient (AVLG) optimization method. AVLG is an approach in optimization process and it is based on the Univariate method. The line segments form the initial and critical slip surface. Pile improper installation and inadequate length not only fails to increase the factor of safety, but also reduces it. The analyses are performed using the limit equilibrium (LE) method. Results of these analyses are acceptable and are properly consistent with the results obtained by other researchers.

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In soft soil areas, equal-length piles are often adopted in the retaining system. A decrease in the bending moment value borne by the retaining structure along the pile depth (below the excavation bottom), leads to an inadequate use of the pile bending capacity near the pile bottom. This paper presents retaining systems with long and short pile combinations, in which the long piles ensure integral stability of the excavation while the short piles give full play to bearing the bending moment. For further analysis on pile and bottom heaves deformations and inner-force characteristics, three-dimensional models were built in order to simulate the stage construction of the excavation. The ratio between long and short pile numbers, and the effects on short pile length pile horizontal deformation, pile bending moment and bottom heave are investigated in detail. In the end, a feasible long-short pile combination is established. Obtained results from the simulation data and the field data prove that the long-short pile retaining system is feasible.

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To increase the safety of structures against strong ground motions and their life due to environmental issues on the earth and saving in terms of materials, it is necessary to expand and upgrade seismic resistant systems. However, more cost-effective systems which have sufficient influence on the seismic performance of structures and also more compatibility with the regional conditions, will be more desirable than other systems. One of the seismic resistance systems is seismic isolation. In the event of interest in using the seismic isolation system for a mounted building on piles, the costly construction of piles and isolation equipment shall be provided simultaneously. The seismic isolating using sleeved-piles which is generally used in combination with various damper systems, can help to overcome this issue. In this research a seismic isolator system using sleeved-pile has been studied while considering the damping behavior of the soil-rubber mixture as the only source of damping. To investigate the proposed system, a series of tests including static lateral load test, dynamic free and forced vibration tests, were performed on a model pile in a field laboratory which has been constructed for this purpose. According to results of tests the proposed system has a good deformation ability and damping characteristics, and as a method of seismic isolation is completely efficient.

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In present research, 17 centrifuge tests have been conducted to study the effect of various parameters such as the number of piles, the distance between piles, gradation and thickness of the granular layer on the load-settlement behavior of a pile raft system. The results showed the importance of granular layer to reduce the settlement of non-connected pile raft system when the roles of piles are to reduce the settlement. In other words when the piles have major contribution on the bearing capacity of pile raft system, presence of a granular layer may increase the settlement.

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The paper present the results of various experimental and numerical studies on slopes, small scale physical modeling of slope under surcharge load were performed in loose sand environment. Digital images were captured during the incremental loading from side of model simultaneously. The Particle Image Velocimetry (PIV) and 3D numerical model was applied to investigate the slope under surcharge loading and some of the other important factors that control the performance of piles are investigated. The factors of safety and location of critical failure surfaces of reinforced and unreinforced slopes obtained and compared for various slopes. For homogenous slope, it is found for stabilized slope with piles, the 3D failure surface shape in front of piles is triangle, unlike its conical shape in laterally loaded piles. The paper also studies numerically the effect of soft bound effect, soil properties, pile spacing, pile position and surcharge distance effects on stabilized and none stabilized slopes. The results indicate that the depth of soft soil layer from ground surface and its angles with horizontal direction has importance effect on optimum location of stabilized pile. Studies on pile space effects shows with increasing pile space, arching phenomenon didn’t developed and partial pressure of supported portion transferred to un supported soil portion and the potential failure volume of the slope becomes large.

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Pile penetration and rebound amount measurements during pile driving are important in analysis of penetration and bearing characteristics of piles and for assurance of pile installation quality. Traditional manual measurement of penetration and rebound of piles exposes engineers under unfavorable environment of injury risk and significant vibration and noise. To improve accuracy of pile penetration and rebound measurements and to ensure safety of engineers during pile driving, the close-range photogrammetry approach was implemented. For the track of three-dimensional spatial information of one point on the pile during driving, a series of stereo pair images of the point attached on a pile is required using more than two camera systems at different locations. In this study, two charge coupled device cameras were used to obtain stereo images. Robust measurements and reliable results can be guaranteed by the constrained geometry of close-range photogrammetry. From the field implementation, it was found that the newly developed pile penetration and rebound measurement system is accurate and safe.

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Pile load tests and numerical analysis of a small-scale model pile in unsaturated clayey soil are presented in this paper. A small-scale model pile was simulated to bear a static axial loading in unsaturated soil using finite element method. All parameters used in the finite element method were obtained in laboratory tests, including the direct shear test, interface direct shear test, and filter paper method. The numerical analysis results were compared with the pile load test results. The results show that the general trend of pile load and pile head settlement relationship obtained by the numerical analysis shows a good consistence with the pile load test results. With increasing water content of the soil, the matric suction, dilatancy angle and shear strength decrease, and consequently the ultimate bearing capacity of pile decreases.

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It is vital to control the settlement of ultra-high voltage and long span tower foundation because of the difficult construction and strict deformation control. Based on the thinking of deformation compatibility, the mechanical model of deformation compatibility between pile and soil is established. Relying on the long span tower project Lingzhou–Shaoxing ±800 kV DC transmission lines across the Yangtze River, through checking ultimate bearing capacity of existing pile foundation, it can be obtained that the present design foundation can effectively meet the upper 200–220 t load, but it cannot meet the load requirements about 300 t in the construction. The failures of tower foundation mainly display that piles cut into the soil with penetration type in the early condition. With the load increasing, the shallow soil and infrastructure gradually damage with the whole cap sinking, cushion layer destruction and the surrounding soil uplifting. As a result, tower foundation is unable to withstand the effect of upper overload and the whole tower becomes shear failure. The treatment scheme was proposed that it can improve the cushion thickness and strength combined with grouting consolidation to soil around the piles. Thus, the stability of tower foundation improves significantly and settlement was controlled within the permitted range of below 10 mm, which can meet the structure requirements. The results of numerical simulation based on deformation compatibility between pile and soil coincide well with field measured results.