The Experts below are selected from a list of 1716 Experts worldwide ranked by ideXlab platform
Maosong Huang - One of the best experts on this subject based on the ideXlab platform.
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Axial Capacity degradation of single Piles in soft clay under cyclic loading
Soils and Foundations, 2015Co-Authors: Maosong HuangAbstract:Abstract A kinematic hardening constitutive model with von Mises failure criterion considering cyclic degradation was developed to analyze the cyclic Axial response of single Piles in saturated clay. After validation by comparison against published triAxial test results, this model was applied to a numerical simulation developed for computing the Axial bearing Capacity of a Pile foundation subjected to a cyclic loading. The Axial bearing Capacity degradation of a single Pile under different cyclic load levels and different cyclic load numbers was studied. It was found that the Pile–soil system remains elastic at very low cyclic load levels, and the degradation of Pile Capacity happens when the cyclic load level increases. A higher cyclic load level after more cycles leads to faster degradation. In order to improve the computational efficiency, a simplified analysis method based on a simple nonlinear soil model is presented for the cyclic Axial Capacity degradation of single Piles. The results calculated by this simplified analysis are consistent with those of the numerical simulation. Comparisons with laboratory test data suggest that both the finite element method and the simplified analysis method provide reasonable estimates of the Axial Pile Capacity degradation of a single Pile after cyclic loading.
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Calculations of Axial Pile Capacity under Sustained Cyclic Loading for Offshore Wind Turbine Foundations
GeoCongress 2012, 2012Co-Authors: Maosong Huang, Ying LiuAbstract:In the paper, a finite element analysis procedure is proposed for the calculation of Axial Pile Capacity under sustained cyclic loading for offshore wind turbine foundations. In the numerical simulation, an undrained elastic-plastic model considering the cyclic degradation of clayey soils is adopted, and this model is obtained from data analysis on a series of static and cyclic undrained triAxial tests of saturated soft clay. Based on this model, a number of numerical simulations are conducted by a commercially available finite element software at different cyclic load levels. The ultimate Axial bearing Capacity and Axial stiffness of single Pile resisting Axial cyclic load calculated by the finite element analysis have a good consistency with the model tests data in Poulos (1979), which verifies the reasonability and reliability of the proposed numerical procedure. Afterwards, the Axial bearing capacities of Pile foundation of Shanghai Donghai-bridge offshore wind farm under cyclic load are studied with the application of the proposed numerical method. The proposed method will serve as a useful tool for engineering design.
Paul W Mayne - One of the best experts on this subject based on the ideXlab platform.
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CPTu-based enhanced UniCone method for Pile Capacity
Engineering Geology, 2016Co-Authors: Fawad S. Niazi, Paul W MayneAbstract:Abstract The UniCone direct piezocone method by Eslami and Fellenius (1997) for evaluating the Axial Capacity of Pile foundations is reviewed and improved means of evaluating the soil resistance factors are recommended. This method uses all three piezocone penetration test (CPTu) readings in a soil behavioral type (SBT) classification chart and provides estimations of Axial Pile Capacity for a wide variety of Pile types installed in different assortments of geomaterials. In this paper, the earlier method is improved using a dataset of 153 Pile load tests and CPTu soundings from 52 worldwide sites. An alternative soil classification system using the CPT material index I c is used to provide improved correlations of higher reliability via continuous functions for estimating the side and base Capacity components of driven and jacked Piles, and drilled shafts. An analysis is also included to test the performance of the newly proposed design formulations. Finally, a simplified flowchart is presented for convenient application of the enhanced expressions.
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Enhanced UniCone Expressions for Axial Pile Capacity Evaluation from Piezocone Tests
IFCEE 2015, 2015Co-Authors: Fawad S. Niazi, Paul W MayneAbstract:Using a large database derived from 153 full scale load tests on Axially loaded Pile foundations, a more refined direct cone penetration test (CPT) method of Pile Capacity analysis is developed from the 1997 UniCone approach proposed by Eslami and Fellenius (1997). A larger database permits separation of Pile type and installation method: drilled, augered, jacked, and driven. Also, tension tests are separated from compression load tests. It is found that the original 5-part zonal soil behavior classification by piezocone test (CPTu) can be subdivided into finer categories of soil type. Furthermore, the Pile side coefficient (Cse) linking effective cone resistance (qE = qt - u2) to Pile unit shaft resistance (fp = Cse qE) can be related as a continuous function, rather than just five discrete values. The continuous function for Cse is provided via use of the CPT material index (Ic). A refined definition of the Pile toe resistance (qb = Cte qE-toe) is made where Cte is also expressed as a continuous function of Ic. A case study is presented to demonstrate the improved assessments of the Axial Pile Capacity via the proposed modifications.
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Cone Penetration Test Based Direct Methods for Evaluating Static Axial Capacity of Single Piles
Geotechnical and Geological Engineering, 2013Co-Authors: Fawad S. Niazi, Paul W MayneAbstract:The direct cone penetration test (CPT) based Pile design methods use the measured penetrometer readings by scaling relationships or algorithms in a single-step process to enable the assessment of Pile Capacity components of shaft and base resistance ( f _p and q _b, respectively) for evaluation of full-size pilings. This paper presents a state-of-the-art review of published works that focus on direct CPT evaluation of static Axial Pile Capacity. The review is presented in a chronological order to explicate the evolution over the past six decades of an in situ test based solution for this soil-structure interaction problem. The objective of this study is an attempt to assemble maximum published methods proposed as a result of past investigations in one resource to afford researchers and practitioners with convenient access to the respective design equations and charts. In addition to an all-inclusive summary table and the design charts, a compilation of significant findings and discussions thereof are presented. Furthermore, potential future research directions are indicated, with special emphasis on the optimal use of the modern multi-channel hybrid geophysical-geotechnical seismic CPT to evaluate the complete Axial Pile load–displacement response.
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Drilled Shaft Response in Piedmont Residuum Using Elastic Continuum Analysis and Seismic Piezocone Tests
Deep Foundations and Geotechnical In Situ Testing, 2010Co-Authors: Paul W Mayne, Fawad S. Niazi, David J. WoellerAbstract:The Axial load-displacement-Capacity response of drilled shaft and bored Pile foundations can be evaluated during the analysis and design stage using an elastic continuum framework and results from in-situ testing methods, in particular, the seismic piezocone test (SCPTu). The SCPTu is an optimal and economical means for collection of geotechnical data because the same sounding provides up to five separate measurements with depth: cone tip resistance (qt), sleeve friction (fs), porewater pressure (u2), time rate of consolidation (t50), and shear wave velocity (Vs). Moreover, the SCPTu provides information on soil behavior at both ends of the stress-strain-strength curves, namely the peak strength and geostatic stress state for evaluating Axial Pile Capacity and the small-strain stiffness (Gmax = ρt•Vs2) for the initial soil-Pile deformations. Using a Randolph-type analytical elastic Pile model, the approach can handle either traditional top down compression loading by dead-weight or reaction beam systems, or the more recent Osterberg cell that juxtaposes base and side resistances in opposite directions. A case study involving O-cell tests on a drilled shaft in Piedmont residuum and partially-weathered rock in Atlanta are presented.
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Evaluating Axial Elastic Pile Response from Cone Penetration Tests (The 2009 Michael W. O'Neill Lecture)
DFI Journal - The Journal of the Deep Foundations Institute, 2009Co-Authors: Paul W Mayne, Fawad S. NiaziAbstract:AbstractAxial Pile performance can be rationally evaluated within an elastic continuum framework using field results from seismic piezocone tests (SCPTu). Adopting a versatile Randolph-type elastic Pile model, the approach can be applied to either traditional top down loading using an anchored reaction beam or the newer Osterberg cell that simultaneously pushes the base and shaft in opposite directions. The Axial load distribution within the shaft is also evaluated. For site-specific data at a given site, the SCPTu is an optimal means for collection of subsurface information because it combines penetrometer readings and downhole geophysics in one sounding. The results obtained are at opposite ends of the stress-strain-strength curves, specifically the peak strength for Capacity interpretations and the small-strain stiffness (Emax) for evaluating the initial deformations. Axial Pile Capacity can be analyzed using both direct and indirect CPT methods. As such, the approach allows for a complete representati...
Fawad S. Niazi - One of the best experts on this subject based on the ideXlab platform.
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CPTu-based enhanced UniCone method for Pile Capacity
Engineering Geology, 2016Co-Authors: Fawad S. Niazi, Paul W MayneAbstract:Abstract The UniCone direct piezocone method by Eslami and Fellenius (1997) for evaluating the Axial Capacity of Pile foundations is reviewed and improved means of evaluating the soil resistance factors are recommended. This method uses all three piezocone penetration test (CPTu) readings in a soil behavioral type (SBT) classification chart and provides estimations of Axial Pile Capacity for a wide variety of Pile types installed in different assortments of geomaterials. In this paper, the earlier method is improved using a dataset of 153 Pile load tests and CPTu soundings from 52 worldwide sites. An alternative soil classification system using the CPT material index I c is used to provide improved correlations of higher reliability via continuous functions for estimating the side and base Capacity components of driven and jacked Piles, and drilled shafts. An analysis is also included to test the performance of the newly proposed design formulations. Finally, a simplified flowchart is presented for convenient application of the enhanced expressions.
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Enhanced UniCone Expressions for Axial Pile Capacity Evaluation from Piezocone Tests
IFCEE 2015, 2015Co-Authors: Fawad S. Niazi, Paul W MayneAbstract:Using a large database derived from 153 full scale load tests on Axially loaded Pile foundations, a more refined direct cone penetration test (CPT) method of Pile Capacity analysis is developed from the 1997 UniCone approach proposed by Eslami and Fellenius (1997). A larger database permits separation of Pile type and installation method: drilled, augered, jacked, and driven. Also, tension tests are separated from compression load tests. It is found that the original 5-part zonal soil behavior classification by piezocone test (CPTu) can be subdivided into finer categories of soil type. Furthermore, the Pile side coefficient (Cse) linking effective cone resistance (qE = qt - u2) to Pile unit shaft resistance (fp = Cse qE) can be related as a continuous function, rather than just five discrete values. The continuous function for Cse is provided via use of the CPT material index (Ic). A refined definition of the Pile toe resistance (qb = Cte qE-toe) is made where Cte is also expressed as a continuous function of Ic. A case study is presented to demonstrate the improved assessments of the Axial Pile Capacity via the proposed modifications.
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An Update on Pile-CPTu Direct Correlations
Ports 2013, 2013Co-Authors: Fawad S. NiaziAbstract:The Axial Pile Capacity can be estimated from the cone penetration test (CPT) using either indirect methods or direct methods. The indirect methods employ a dual-phase methodology of estimating the geoparameters for evaluating the shaft and base resistance (fp and qb, respectively) of the Pile Capacity. The direct methods use the penetrometer readings to directly obtain fp and qb. These correlation efforts from the results of Pile and penetrometer testing have resulted in a large variety of design methodologies. The newer multi-channel piezocone test (CPTu) device allows for derivation of more elaborate correlations. To update the Pile design formulations, a quick review of the CPTu-based methods is presented, followed by the results of a comprehensive study, where the most updated and the largest Pile-CPTu database were used. Simplified correlations, based on cone soil classification index (Ic), are presented for fp and qb for different Pile types.
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Cone Penetration Test Based Direct Methods for Evaluating Static Axial Capacity of Single Piles
Geotechnical and Geological Engineering, 2013Co-Authors: Fawad S. Niazi, Paul W MayneAbstract:The direct cone penetration test (CPT) based Pile design methods use the measured penetrometer readings by scaling relationships or algorithms in a single-step process to enable the assessment of Pile Capacity components of shaft and base resistance ( f _p and q _b, respectively) for evaluation of full-size pilings. This paper presents a state-of-the-art review of published works that focus on direct CPT evaluation of static Axial Pile Capacity. The review is presented in a chronological order to explicate the evolution over the past six decades of an in situ test based solution for this soil-structure interaction problem. The objective of this study is an attempt to assemble maximum published methods proposed as a result of past investigations in one resource to afford researchers and practitioners with convenient access to the respective design equations and charts. In addition to an all-inclusive summary table and the design charts, a compilation of significant findings and discussions thereof are presented. Furthermore, potential future research directions are indicated, with special emphasis on the optimal use of the modern multi-channel hybrid geophysical-geotechnical seismic CPT to evaluate the complete Axial Pile load–displacement response.
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Drilled Shaft Response in Piedmont Residuum Using Elastic Continuum Analysis and Seismic Piezocone Tests
Deep Foundations and Geotechnical In Situ Testing, 2010Co-Authors: Paul W Mayne, Fawad S. Niazi, David J. WoellerAbstract:The Axial load-displacement-Capacity response of drilled shaft and bored Pile foundations can be evaluated during the analysis and design stage using an elastic continuum framework and results from in-situ testing methods, in particular, the seismic piezocone test (SCPTu). The SCPTu is an optimal and economical means for collection of geotechnical data because the same sounding provides up to five separate measurements with depth: cone tip resistance (qt), sleeve friction (fs), porewater pressure (u2), time rate of consolidation (t50), and shear wave velocity (Vs). Moreover, the SCPTu provides information on soil behavior at both ends of the stress-strain-strength curves, namely the peak strength and geostatic stress state for evaluating Axial Pile Capacity and the small-strain stiffness (Gmax = ρt•Vs2) for the initial soil-Pile deformations. Using a Randolph-type analytical elastic Pile model, the approach can handle either traditional top down compression loading by dead-weight or reaction beam systems, or the more recent Osterberg cell that juxtaposes base and side resistances in opposite directions. A case study involving O-cell tests on a drilled shaft in Piedmont residuum and partially-weathered rock in Atlanta are presented.
Sudip Basack - One of the best experts on this subject based on the ideXlab platform.
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Piles Subjected to Torsional Cyclic Load: Numerical Analysis
Frontiers in Built Environment, 2019Co-Authors: Sanjay Nimbalkar, Sudip Basack, Piyush Punetha, Mehdi MirzababaeiAbstract:Pile foundations supporting large structures (such as high-rise buildings, oil drilling platforms, bridges etc.) are often subjected to eccentric lateral load (in addition to the vertical loads) due to the action of wind, waves, high speed traffic and ship impacts etc. The eccentric lateral load, which is usually cyclic (repetitive) in nature, induces torsion in the Pile foundation. This paper presents a numerical model based on boundary element approach to study the performance of a single Pile subjected to the torsional cyclic load. The model is initially validated by comparing it with the experimental data available from the literature. Thereafter, the model has been utilised to conduct a parametric study to understand the influence of the torsional cyclic loading parameters on the Axial Pile Capacity. The results indicated that the model is able to capture the degradation in the Axial Pile Capacity due to the torsional cyclic loading with a reasonable accuracy. Moreover, the parametric study showed that the frequency, amplitude and number of cycles play a significant role in the torsional cyclic response of the Pile. The present study is essential for the development of design guidelines for Pile foundations subjected to torsional cyclic load.
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Influence of Relative Pile-Soil Stiffness and Load Eccentricity on Single Pile Response in Sand Under Lateral Cyclic Loading
Geotechnical and Geological Engineering, 2012Co-Authors: Sudip BasackAbstract:The environment prevalent in ocean necessitates the Piles supporting offshore structures to be designed against lateral cyclic loading initiated by wave action, which induces deterioration in the strength and stiffness of the Pile-soil system introducing progressive reduction in the bearing Capacity associated with increased settlement of the Pile foundation. A thorough and detailed review of literature indicates that significant works have already been carried out in the relevant field of investigation. It is a well established phenomenon that the variation of relative Pile-soil stiffness ( K _ rs ) and load eccentricity ( e/D ) significantly affect the response of Piles subjected to lateral static load. However, the influence of lateral cyclic load on Axial response of single Pile in sand, more specifically the effect of K _ rs and e/D on the cyclic behavior, is yet to be investigated. The present work has aimed to bridge up this gap. To carry out numerical analysis (boundary element method), the conventional elastic approach has been used as a guideline with relevant modifications. The model developed has been validated by comparing with available experimental (laboratory model and field tests) results, which indicate the accuracy of the solutions formulated. Thereafter, the methodology is applied successfully to selected parametric studies for understanding the magnitude and pattern of degradation of Axial Pile Capacity induced due to lateral cyclic loading, as well as the influence of K _ rs and e/D on such degradation.
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A boundary element analysis on the influence of Krc and e/d on the performance of cyclically loaded single Pile in clay
Latin American Journal of Solids and Structures, 2010Co-Authors: Sudip BasackAbstract:The environment prevalent in oceans necessitates the Piles supporting offshore structures to be designed against lateral cyclic loading initiated by wave action. Such quasi-static load reversal induces deterioration in the strength and stiffness of the soil-Pile system, introducing progressive reduction in the bearing Capacity associated with increased settlement of the Pile foundation. To understand the effect of lateral cyclic load on Axial response of single Piles in soft clay, a numerical model was previously developed and validated by the author. Using the methodology, further analysis has been carried out to investigate how the variation in relative Pilesoil stiffness and eccentricity effects the degradation of Axial Pile Capacity due to the effect of lateral cyclic load. This paper presents a brief description of the methodology, analysis and interpretations of the theoretical results obtained from the further analysis and the relevant conclusions drawn there
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INFLUENCE OF L/d AND e/d RATIOS ON THE RESPONSE OF CYCLICALLY LOADED SINGLE Pile IN UNIFORM CLAY
2009Co-Authors: Sudip BasackAbstract:The environment prevalent in ocean necessitates the Piles supporting offshore structures to be designed against lateral cyclic loading initiated by wave action. Such quasi-static load reversal induces deterioration in the strength and stiffness of the soil-Pile system introducing progressive reduction in the bearing Capacity associated with increased settlement of the Pile foundation. To understand the effect of lateral cyclic load on Axial response of single Pile in soft clay, a numerical model was previously developed by the author. Using the methodology, further analysis has been carried out to investigate how the variation in relative Pile-soil stiffness and eccentricity affects the degradation of Axial Pile Capacity due to the effect of lateral cyclic load. This paper presents a brief description of the methodology, analysis and interpretations of the theoretical results obtained and the relevant conclusions drawn there from.
Christian Moormann - One of the best experts on this subject based on the ideXlab platform.
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A parametric study of different analytical design methods to determine the Axial bearing Capacity of monoPiles
Geomechanics for Energy and the Environment, 2016Co-Authors: Johannes Labenski, Christian MoormannAbstract:Abstract In Europe many offshore wind power parks have already been realized and more are planned. Often monoPiles are used as foundation for wind power plants. The determination of the Axial Pile Capacity of monoPiles is among the important issues for offshore energy projects. Despite progress made so far in this field, there are still big challenges faced by researchers. Among them is to provide guidance to assist engineers in the selection of an appropriate design method for the soil condition and Pile configuration of interest. First, different state of the art methods (API, Fugro-05, ICP-05, NGI-05 and UWA-05) together with two new methods (HKU-12 and a German approach) to determine the Axial bearing Capacity based on the cone resistance of the soil are presented. Afterwards there is a summary of different approaches to determine the average cone resistance value. Furthermore a sensitivity analysis is carried out to show the influence of the Pile diameter and the cone resistance on the predicted Axial bearing Capacity of the different design methods. In the last part, published field tests are used to compare the presented design methods and to identify their potential for reliable predictions for engineering practice. In addition to existing publications, these comparisons contain the two new design methods to determine the Axial bearing Capacity.
