In order to improve the reliability of the design and calculation of single piles under the combined vertical and lateral loads, the solutions were presented based on the subgrade reaction method, in which the ultimat...In order to improve the reliability of the design and calculation of single piles under the combined vertical and lateral loads, the solutions were presented based on the subgrade reaction method, in which the ultimate soil resistance was considered and the coefficient of subgrade reaction was assumed to be a constant. The corresponding computational program was developed using FORTRAN language. A comparison between the obtained solutions and the model test results was made to show the validity of the obtained solutions. The calculation results indicate that both the maximum lateral displacement and bending moment increase with the increase of the vertical and lateral loads and the pile length above ground, while decrease as the pile stiffness, the coefficient of subgrade reaction and the yielding displacement of soil increase. It is also shown that the pile head condition controls the pile responses and the vertical load may cause the instability problem to the pile. In general, the proposed method can be employed to calculate the pile responses independent of the magnitude of the pile deflection.展开更多
The pile group with elevated cap is widely used as foundation of offshore structures such as turbines, power transmission towers and bridge piers, and understanding its behavior under cyclic lateral loads induced by w...The pile group with elevated cap is widely used as foundation of offshore structures such as turbines, power transmission towers and bridge piers, and understanding its behavior under cyclic lateral loads induced by waves, tide water and winds, is of great importance to designing. A large-scale model test on 3×3 pile group with elevated cap subjected to cyclic lateral loads was performed in saturated silts. The preparation and implementation of the test is presented. Steel pipes with the outer diameter of 114 mm, thickness of 4.5 mm, and length of 6 m were employed as model piles. The pile group was cyclic loaded in a multi-stage sequence with the lateral displacement controlled. In addition, a single pile test was also conducted at the same site for comparison. The displacement of the pile cap, the internal forces of individual piles, and the horizontal stiffness of the pile group are presented and discussed in detail. The results indicate that the lateral cyclic loads have a greater impact on pile group than that on a single pile, and give rise to the significant plastic strain in the soil around piles. The lateral loads carried by each row of piles within the group would be redistributed with loading cycles. The lateral stiffness of the pile group decreases gradually with cycles and broadly presents three different degradation patterns in the test. Significant axial forces were measured out in some piles within the group, owing to the strong restraint provided by the cap, and finally lead to a large settlement of the pile group. These findings can be referred for foundation designing of offshore structures.展开更多
Although the load applied to pile foundations is usually a combination of vertical and lateral components,there have been few investigations on the behavior of piles subjected to combined loadings.Those few studies le...Although the load applied to pile foundations is usually a combination of vertical and lateral components,there have been few investigations on the behavior of piles subjected to combined loadings.Those few studies led to inconsistent results with regard to the effects of vertical loads on the lateral response of piles.A series of three-dimensional(3D) finite differences analyses is conducted to evaluate the influence of vertical loads on the lateral performance of pile foundations.Three idealized sandy and clayey soil profiles are considered:a homogeneous soil layer,a layer with modulus proportional to depth,and two-layered strata.The pile material is modeled as linearly elastic,while the soil is idealized using the Mohr-Coulomb constitutive model with a non-associated flow rule.In order to confirm the findings of this study,soils in some cases are further modeled using more sophisticated models(i.e.CYsoil model for sandy soils and modified Cam-Clay(MCC) model for clayey soils).Numerical results showed that the lateral resistance of the piles does not appear to vary considerably with the vertical load in sandy soil especially at the loosest state.However,the presence of a vertical load on a pile embedded in homogeneous or inhomogeneous clay is detrimental to its lateral capacity,and it is unconservative to design piles in clays assuming that there is no interaction between vertical and lateral loads.Moreover,the current results indicate that the effect of vertical loads on the lateral response of piles embedded in twolayered strata depends on the characteristics of soil not only surrounding the piles but also located beneath their tips.展开更多
In 2023,pivotal advancements in artificial intelligence(AI)have significantly experienced.With that in mind,traditional methodologies,notably the p-y approach,have struggled to accurately model the complex,nonlinear s...In 2023,pivotal advancements in artificial intelligence(AI)have significantly experienced.With that in mind,traditional methodologies,notably the p-y approach,have struggled to accurately model the complex,nonlinear soil-structure interactions of laterally loaded large-diameter drilled shafts.This study undertakes a rigorous evaluation of machine learning(ML)and deep learning(DL)techniques,offering a comprehensive review of their application in addressing this geotechnical challenge.A thorough review and comparative analysis have been carried out to investigate various AI models such as artificial neural networks(ANNs),relevance vector machines(RVMs),and least squares support vector machines(LSSVMs).It was found that despite ML approaches outperforming classic methods in predicting the lateral behavior of piles,their‘black box'nature and reliance only on a data-driven approach made their results showcase statistical robustness rather than clear geotechnical insights,a fact underscored by the mathematical equations derived from these studies.Furthermore,the research identified a gap in the availability of drilled shaft datasets,limiting the extendibility of current findings to large-diameter piles.An extensive dataset,compiled from a series of lateral loading tests on free-head drilled shaft with varying properties and geometries,was introduced to bridge this gap.The paper concluded with a direction for future research,proposes the integration of physics-informed neural networks(PINNs),combining data-driven models with fundamental geotechnical principles to improve both the interpretability and predictive accuracy of AI applications in geotechnical engineering,marking a novel contribution to the field.展开更多
Response surface method is used to study the reliability analysis of laterally loaded piles in sloping ground. A development load-displacement （p-y） curve for laterally loaded pile response in sloping ground is used...Response surface method is used to study the reliability analysis of laterally loaded piles in sloping ground. A development load-displacement （p-y） curve for laterally loaded pile response in sloping ground is used to model the pile-soil system, both the pile head displacement and the maximum bending moment of the piles are used as the performance criteria in this study. The reliability analysis method of the laterally loaded pile in sloping ground under the pile head displacement and the maximum bending moment failure modes is proposed, which is in good agreement with the Monte Carlo method. The influences on the probability index of failure by a number of parameters are discussed. It is shown that the variability of pile head displacement increases with the increase in the coefficients of variation of ultimate bearing capacity factor （Npu）, secant elastic modulus at 50%（E50） and level load （H）. A negative correlation between Npu and non-dimensional factor （λ） leads to less spread out probability density function （PDF） of the pile head displacement;in contrast, a positive correlation between Npu andλgives a great variation in the PDF of pile head displacement. As for bearing capacity factor on ground surface （Npo） and λ, both negative and positive correlations between them give a great variation in the PDF of pile head displacement, and a negative correlation will obviously increase the variability of the response.展开更多
In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogene...In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogeneous, semi-infinite isotropic medium. A comparison was made between model test results and the obtained solutions to show their validity. The calculation results indicate that the horizontal displacement and bending moment of the pile increase with increases of the axial and lateral loads. The maximum horizontal displacement and bending moment decrease by 37.9% and 13.9%, respectively, when the elastic modulus of soil increases from 4 MPa to 20 MPa. The Poisson ratio of soil plays a marginal role in pile responses. There is a critical pile length under the ground, beyond which the pile behaves as though it was infinitely long. The presented solutions can make allowance for the continuous nature of soil, and if condition permits, they can approach exact ones.展开更多
Monotonic lateral load model tests were carried out on steel skirted suction caissons embedded in the saturated medium sand to study the bearing capacity. A three-dimensional continuum finite element model was develop...Monotonic lateral load model tests were carried out on steel skirted suction caissons embedded in the saturated medium sand to study the bearing capacity. A three-dimensional continuum finite element model was developed with Z_SOIL software. The numerical model was calibrated against experimental results. Soil deformation and earth pressures on skirted caissons were investigated by using the finite element model to extend the model tests. It shows that the ＂skirted＂ structure can significantly increase the lateral capacity and limit the deflection, especially suitable for offshore wind turbines, compared with regular suction caissons without the ＂skirted＂ at the same load level. In addition, appropriate determination of rotation centers plays a crucial role in calculating the lateral capacity by using the analytical method. It was also found that the rotation center is related to dimensions of skirted suction caissons and loading process, i.e. the rotation center moves upwards with the increase of the ＂skirted＂ width and length; moreover, the rotation center moves downwards with the increase of loading and keeps constant when all the sand along the caisson＇s wall yields. It is so complex that we cannot simply determine its position like the regular suction caisson commonly with a specified position to the length ratio of the caisson.展开更多
Construction of seaside and underground wall bracing often uses stiffened deep cement mixed columns （SDCM）. This research investigates methods used to improve the level of bearing capacity of these SDCM when subject...Construction of seaside and underground wall bracing often uses stiffened deep cement mixed columns （SDCM）. This research investigates methods used to improve the level of bearing capacity of these SDCM when subjected to cyclic lateral loading via various types of stiffer cores. Eight piles, two deep cement mixed piles and six stiffened deep cement mixing piles with three different types of cores, H shape cross section prestressed concrete, steel pipe, and H-beam steel, were embedded though soft clay into medium-hard clay on site in Thailand. Cyclic horizontal loading was gradually applied until pile failure and the hysteresis loops of lateral load vs. lateral deformation were recorded. The lateral carrying capacities of the SDCM piles with an H-beam steel core increased by 3-4 times that of the DCM piles. This field research clearly shows that using H-beam steel as a stiffer core for SDCM piles is the best method to improve its lateral carrying capacity, ductility and energy dissipation capacity.展开更多
The seismic capacity curves of three types of buildings including frame,frame-shear wall and shear wall ob- tained by pushover analysis under different lateral load patterns are compared with those from nonlinear time...The seismic capacity curves of three types of buildings including frame,frame-shear wall and shear wall ob- tained by pushover analysis under different lateral load patterns are compared with those from nonlinear time history analy- sis.Based on the numerical results obtained a two-phase load pattern:an inverted triangle(first mode)load pattern until the base shear force reaches β times its maximum value,V_(max)followed by a(x/H)~α form,here β and α being some coeffi- cients depending on the type of the structures considered,is proposed in the paper,which can provide excellent approxima- tion of the seismic capacity curve for low-to-mid-rise shear type buildings.Furthermore,it is shown both the two-phase load pattern proposed and the invariant uniform pattern can be used for low-to-mid-rise shear-bending type and low-rise bending type of buildings.No suitable load patterns have been found for high-rise buildings.展开更多
A developed stereo particle image velocimetry(stereo-PIV) system was proposed to measure three-dimensional(3D) soil deformation around a laterally loaded pile in sand.The stereo-PIV technique extended 2D measurement t...A developed stereo particle image velocimetry(stereo-PIV) system was proposed to measure three-dimensional(3D) soil deformation around a laterally loaded pile in sand.The stereo-PIV technique extended 2D measurement to 3D based on a binocular vision model,where two cameras with a well geometrical setting were utilized to image the same object simultaneously.This system utilized two open software packages and some simple programs in MATLAB,which can easily be adjusted to meet user needs at a low cost.The failure planes form an angle with the horizontal line,which are measured at 27°-29°,approximately three-fourths of the frictional angle of soil.The edge of the strain wedge formed in front of the pile is an arc,which is slightly different from the straight line reported in the literature.The active and passive influence zones are about twice and six times of the diameter of the pile,respectively.The test demonstrates the good performance and feasibility of this stereo-PIV system for more advanced geotechnical testing.展开更多
The scrap tire rubber pad(STRP)made by natural or synthetic rubber and high strength reinforcing cords exhibits substantial vertical stiffness and horizontal flexibility,and these properties can be regarded as suitabl...The scrap tire rubber pad(STRP)made by natural or synthetic rubber and high strength reinforcing cords exhibits substantial vertical stiffness and horizontal flexibility,and these properties can be regarded as suitable for seismic isolators for structures.The use of environmentally burdensome scrap tires as STRP isolators might be convenient as an efficient and low-cost solution for the implementation of aseismic design philosophy for low-to-medium rise buildings,especially in developing countries.Finite element analyses of unbonded square and strip-shaped STRP isolators subjected to a combination of axial and lateral loads are conducted to investigate its lateral deformation performance under seismic loading.The rubber of the isolator is modelled with Mooney-Rivlin hyperelastic and Prony viscoelastic materials,including the Mullins material damage effect.The influence of the length-to-width ratio and bearing height on the isolator performance is assessed in terms of the force-displacement relationship,horizontal stiffness,damping,and isolation periods.It is shown that the dependence of stiffness on the length-to-width ratio is significant in the longitudinal direction and minor in the transverse direction.The STRP isolators following the proposed design criteria are shown to satisfy the performance requirement at different levels of seismic demand specified by the ASCE/SEI 7-2010 seismic provisions.展开更多
An empirical approach has been developed to analyze the nonlinear response of a pile group with arbitrarily distributed piles subjected to combined lateral and torsional loading.In this approach,the concept of instant...An empirical approach has been developed to analyze the nonlinear response of a pile group with arbitrarily distributed piles subjected to combined lateral and torsional loading.In this approach,the concept of instantaneous twist center is applied to analyze the displacement relationship of pile heads and establish the static equilibrium equations of the pile cap.The horizontal interaction among the individual piles is considered through the generalized p-multiplier.The coupling effect of lateral resistance on the torsional resistance of each pile is quantified using an empirical factorβ;the lateral and torsional nonlinear responses of individual piles are modeled by p-y andτ-θcurves,respectively.The proposed approach not only captures the most significant aspect of the group effect and coupling effect in a pile group subjected to combined lateral and torsional loading,but also automatically updates p-multipliers of individual piles based on pile cap displacements.The proposed approach was verified using results of model tests on pile groups subjected to lateral loading,torsional loading,and combined lateral and torsional loading,separately.In general,the pile cap response and the transfer of applied loads in the pile groups agree well with the test results.展开更多
The dynamic response and energy absorption performance of foam-filled tubes under lateral external blast loading were investigated experimentally and numerically.A series of blast tests for the foam-filled tubes with ...The dynamic response and energy absorption performance of foam-filled tubes under lateral external blast loading were investigated experimentally and numerically.A series of blast tests for the foam-filled tubes with different geometric parameters were carried out by the use of the ballistic pendulum system.Experimental results were compared with the numerical simulation results employing the software ABAQUS.The results showed that the finite element(FE)analysis was in good agreement with the experimental data.The effects of the diameter and wall thickness of the outer tube,the TNT explosive charge mass,and the standoff distance on the deformation modes,the blast resistance,and the energy absorption performance of the foam-filled tubes were investigated.Three deformation modes of the foam-filled tubes were observed under the lateral external blast loading,including local plastic deformation,large plastic deformation with an elliptic shape,and the tearing of the outer tube.The result revealed that the introduction of the foam core played a vital role in the deflection and energy absorption capacity of the structure.This study provided effective guidelines for designing foam-filled tubes with high energy absorption efficiency.展开更多
The existing studies have primarily focused on the effect of cyclic load characteristics(namely,cyclic load ratio and amplitude ratio)on cyclic lateral response of monopiles in sand,with little attention paid to the e...The existing studies have primarily focused on the effect of cyclic load characteristics(namely,cyclic load ratio and amplitude ratio)on cyclic lateral response of monopiles in sand,with little attention paid to the effect of pile−soil relative stiffness(K_(R)).This paper presents a series of 1-g cyclic tests aimed at improving understanding of the cyclic lateral responses of monopiles under different pile−soil systems.These systems are arranged by two model piles with different stiffness,including four different slenderness ratios(pile embedded length,L,normalized by diameter,D)under medium dense sand.The K_(R)-values are calculated by a previously proposed method considering the real soil stress level.The test results show that the lateral accumulation displacement increases significantly with the increment of the K_(R)-value,while the cyclic secant stiffness performs inversely.The maximum pile bending moment increases with the cycle number for the rigid pile−soil system,but shows a decreasing trend in the flexible system.For an uppermost concern,an empirical model is proposed to predict the accumulated displacement of arbitrary pile−soil systems by combining the results from this study with those from previous experimental investigations.The validity of the proposed model is demonstrated by 1-g and centrifuge tests.展开更多
This research investigates the behavior of a 2×2 pile group under two-directional lateral loads in addition to the vertical load.Through three-dimensional numerical modeling based on Flac 3D software,the study ex...This research investigates the behavior of a 2×2 pile group under two-directional lateral loads in addition to the vertical load.Through three-dimensional numerical modeling based on Flac 3D software,the study examines the total bearing capacity and efficiency coefficient of the pile group,considering factors such as the angle of lateral load,relative pile spacing,and relative stiffness of the pile-soil system.The findings highlight the significance of these factors in understanding and predicting the response of pile groups to changing lateral load directions.The results reveal that increasing the angle of the lateral load from 0°to 45°enhances both the maximum total lateral load and the efficiency coefficient of the pile group.When the relative stiffness of the pile-soil system significantly increases,soil stiffening occurs and reducing the relative spacing of the piles from 7 to 3 times the diameter of the piles diminishes the influence of the pile group.Consequently,the response of the pile group to lateral loads becomes more linear,with only a slight alteration in the maximum total lateral load and the efficiency coefficient when the lateral load is angled from 0°to 45°.Conversely,increasing the relative distance between the piles,specifically from 3 to 7 times the diameter of the piles,amplifies the influence of the pile group.Both the maximum total lateral load and the efficiency coefficient of the pile group exhibit an observed increase.These provide insights for designing pile groups and optimizing their performance under lateral loading conditions.展开更多
The capability of piles to withstand horizontal loads is a major design issue.The current research work aims to investigate numerically the responses of laterally loaded piles at working load employing the concept of ...The capability of piles to withstand horizontal loads is a major design issue.The current research work aims to investigate numerically the responses of laterally loaded piles at working load employing the concept of a beam-on-Winkler-foundation model.The governing differential equation for a laterally loaded pile on elastic subgrade is derived.Based on LegendreGalerkin method and Runge-Kutta formulas of order four and five,the flexural equation of long piles embedded in homogeneous sandy soils with modulus of subgrade reaction linearly variable with depth is solved for both free-and fixed-headed piles.Mathematica,as one of the world’s leading computational software,was employed for the implementation of solutions.The proposed numerical techniques provide the responses for the entire pile length under the applied lateral load.The utilized numerical approaches are validated against experimental and analytical results of previously published works showing a more accurate estimation of the response of laterally loaded piles.Therefore,the proposed approaches can maintain both mathematical simplicity and comparable accuracy with the experimental results.展开更多
In views of the limitations of the existing methods for calculating the pile foundation capacity, a back analysis approach of the m-value is introduced. In order to consider the sensitivity of pile behavior to the m-v...In views of the limitations of the existing methods for calculating the pile foundation capacity, a back analysis approach of the m-value is introduced. In order to consider the sensitivity of pile behavior to the m-value,the relationships between the applied horizontal loads at pile head and the corresponding m-value along with the pile stiffness changes are studied. Based on statistics data from the extensive in-situ tests, the back analysis results suggest an exponential expression for the m-value in various soil conditions and horizontal displacements at pile head. This method is capable of providing an accurate m-value in calculating the pile responses under lateral loads.展开更多
Experiments about working mechanism and mechanical characteristics of the DX model pile foundation under lateral dynamic and static loading were conducted by using a model system of the dynamic frozen soil-pile intera...Experiments about working mechanism and mechanical characteristics of the DX model pile foundation under lateral dynamic and static loading were conducted by using a model system of the dynamic frozen soil-pile interaction. The horizontal displacement-force relationship of the pile head and bending moment distribution along the body in frozen soils of different temperatures were discussed. According to test results, both the horizontal disp!acement-force relationship of the DX pile head and bending moment distribution of the DX pile body are smaller than that of equal-diameter piles under same lateral loads. The piles with different plate positions show different displacements and bending moments. This phenomenon is mainly related to the soil temperature and bearing plates locations. Thus, dynamic response analysis of the pile foundation should be taken into account.展开更多
In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform...In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform lateral load simulated using a gasbag.The investigation involved the performance of light frame wood structure after it experienced the repeated cyclic lateral wind load as well as the performance of the structure under the ultimate lateral load.Then,the study verified that light frame wood structure can resist repeated cyclic wind loads without observable degradation in stiffness during the anticipated serve life,and recommended shear wall percent drift restriction for lateral wind load design of wood structure in serviceability limit states is 1/400 drift,and in ultimate limit states is 1/80 drift.The conclusions of this paper can be benefit for the engineering practice of the light frame wood structures in high wind load regions.展开更多
A finite element method based program has been developed to perform the static nonlinear analysis of pile group with six different configurations subjected to lateral loads. The pile has been assumed to remain elastic...A finite element method based program has been developed to perform the static nonlinear analysis of pile group with six different configurations subjected to lateral loads. The pile has been assumed to remain elastic all the time whereas the soil has been assumed to undergo plastic yielding following von Mises yield criterion. The formulation of elasto-plastic analysis following von Mises yield criterion has been explained. The effect of Drucker-Prager and Mohr Coulomb yield criteria on the response of pile group is also investigated. The whole analysis is based on incremental load application. The external load is applied in small increments and the stresses are initially computed assuming elastic constitutive relation. Significant effect of soil nonlinearity is observed at smaller pile spacing which reduces with increase in spacing.展开更多
基金Foundation item： Projects（50708093, 50808159） supported by the National Natural Science Foundation of China
文摘In order to improve the reliability of the design and calculation of single piles under the combined vertical and lateral loads, the solutions were presented based on the subgrade reaction method, in which the ultimate soil resistance was considered and the coefficient of subgrade reaction was assumed to be a constant. The corresponding computational program was developed using FORTRAN language. A comparison between the obtained solutions and the model test results was made to show the validity of the obtained solutions. The calculation results indicate that both the maximum lateral displacement and bending moment increase with the increase of the vertical and lateral loads and the pile length above ground, while decrease as the pile stiffness, the coefficient of subgrade reaction and the yielding displacement of soil increase. It is also shown that the pile head condition controls the pile responses and the vertical load may cause the instability problem to the pile. In general, the proposed method can be employed to calculate the pile responses independent of the magnitude of the pile deflection.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.51225804 and U1234204)the Zhejiang Electric Power Design Institute
文摘The pile group with elevated cap is widely used as foundation of offshore structures such as turbines, power transmission towers and bridge piers, and understanding its behavior under cyclic lateral loads induced by waves, tide water and winds, is of great importance to designing. A large-scale model test on 3×3 pile group with elevated cap subjected to cyclic lateral loads was performed in saturated silts. The preparation and implementation of the test is presented. Steel pipes with the outer diameter of 114 mm, thickness of 4.5 mm, and length of 6 m were employed as model piles. The pile group was cyclic loaded in a multi-stage sequence with the lateral displacement controlled. In addition, a single pile test was also conducted at the same site for comparison. The displacement of the pile cap, the internal forces of individual piles, and the horizontal stiffness of the pile group are presented and discussed in detail. The results indicate that the lateral cyclic loads have a greater impact on pile group than that on a single pile, and give rise to the significant plastic strain in the soil around piles. The lateral loads carried by each row of piles within the group would be redistributed with loading cycles. The lateral stiffness of the pile group decreases gradually with cycles and broadly presents three different degradation patterns in the test. Significant axial forces were measured out in some piles within the group, owing to the strong restraint provided by the cap, and finally lead to a large settlement of the pile group. These findings can be referred for foundation designing of offshore structures.
文摘Although the load applied to pile foundations is usually a combination of vertical and lateral components,there have been few investigations on the behavior of piles subjected to combined loadings.Those few studies led to inconsistent results with regard to the effects of vertical loads on the lateral response of piles.A series of three-dimensional(3D) finite differences analyses is conducted to evaluate the influence of vertical loads on the lateral performance of pile foundations.Three idealized sandy and clayey soil profiles are considered:a homogeneous soil layer,a layer with modulus proportional to depth,and two-layered strata.The pile material is modeled as linearly elastic,while the soil is idealized using the Mohr-Coulomb constitutive model with a non-associated flow rule.In order to confirm the findings of this study,soils in some cases are further modeled using more sophisticated models(i.e.CYsoil model for sandy soils and modified Cam-Clay(MCC) model for clayey soils).Numerical results showed that the lateral resistance of the piles does not appear to vary considerably with the vertical load in sandy soil especially at the loosest state.However,the presence of a vertical load on a pile embedded in homogeneous or inhomogeneous clay is detrimental to its lateral capacity,and it is unconservative to design piles in clays assuming that there is no interaction between vertical and lateral loads.Moreover,the current results indicate that the effect of vertical loads on the lateral response of piles embedded in twolayered strata depends on the characteristics of soil not only surrounding the piles but also located beneath their tips.
基金supported by Prince Sultan University(Grant No.PSU-CE-TECH-135,2023).
文摘In 2023,pivotal advancements in artificial intelligence(AI)have significantly experienced.With that in mind,traditional methodologies,notably the p-y approach,have struggled to accurately model the complex,nonlinear soil-structure interactions of laterally loaded large-diameter drilled shafts.This study undertakes a rigorous evaluation of machine learning(ML)and deep learning(DL)techniques,offering a comprehensive review of their application in addressing this geotechnical challenge.A thorough review and comparative analysis have been carried out to investigate various AI models such as artificial neural networks(ANNs),relevance vector machines(RVMs),and least squares support vector machines(LSSVMs).It was found that despite ML approaches outperforming classic methods in predicting the lateral behavior of piles,their‘black box'nature and reliance only on a data-driven approach made their results showcase statistical robustness rather than clear geotechnical insights,a fact underscored by the mathematical equations derived from these studies.Furthermore,the research identified a gap in the availability of drilled shaft datasets,limiting the extendibility of current findings to large-diameter piles.An extensive dataset,compiled from a series of lateral loading tests on free-head drilled shaft with varying properties and geometries,was introduced to bridge this gap.The paper concluded with a direction for future research,proposes the integration of physics-informed neural networks(PINNs),combining data-driven models with fundamental geotechnical principles to improve both the interpretability and predictive accuracy of AI applications in geotechnical engineering,marking a novel contribution to the field.
基金Projects(5147847951322403)supported by the National Natural Science Foundation of China+3 种基金Project(2015CX005)supported by Innovation Driven Plan of Central South University,ChinaProject(14JJ4003)supported by Hunan Provincial Natural Science Foundation,ChinaProject(SKLGP2014K008)supported by Opening Fund of State Key Laboratory of Geohazard Prevention and Geoenvironment Protection,Chengdu University of Technology,ChinaProject(2015CB060200)supported by the National Basic Research Program of China
文摘Response surface method is used to study the reliability analysis of laterally loaded piles in sloping ground. A development load-displacement （p-y） curve for laterally loaded pile response in sloping ground is used to model the pile-soil system, both the pile head displacement and the maximum bending moment of the piles are used as the performance criteria in this study. The reliability analysis method of the laterally loaded pile in sloping ground under the pile head displacement and the maximum bending moment failure modes is proposed, which is in good agreement with the Monte Carlo method. The influences on the probability index of failure by a number of parameters are discussed. It is shown that the variability of pile head displacement increases with the increase in the coefficients of variation of ultimate bearing capacity factor （Npu）, secant elastic modulus at 50%（E50） and level load （H）. A negative correlation between Npu and non-dimensional factor （λ） leads to less spread out probability density function （PDF） of the pile head displacement;in contrast, a positive correlation between Npu andλgives a great variation in the PDF of pile head displacement. As for bearing capacity factor on ground surface （Npo） and λ, both negative and positive correlations between them give a great variation in the PDF of pile head displacement, and a negative correlation will obviously increase the variability of the response.
基金Projects(50708093,51208409)supported by the National Natural Science Foundation of ChinaProject(DB01129)supported by the Talent Foundation of Xi’an University of Architecture and Technology,China
文摘In order to improve the design level of partially embedded single piles under simultaneous axial and lateral loads, the differential solutions were deduced, in which the soil was treated as an ideal, elastic, homogeneous, semi-infinite isotropic medium. A comparison was made between model test results and the obtained solutions to show their validity. The calculation results indicate that the horizontal displacement and bending moment of the pile increase with increases of the axial and lateral loads. The maximum horizontal displacement and bending moment decrease by 37.9% and 13.9%, respectively, when the elastic modulus of soil increases from 4 MPa to 20 MPa. The Poisson ratio of soil plays a marginal role in pile responses. There is a critical pile length under the ground, beyond which the pile behaves as though it was infinitely long. The presented solutions can make allowance for the continuous nature of soil, and if condition permits, they can approach exact ones.
基金financially supported by the National Natural Science Foundation of China(Grant No.51078227)Shandong Natural Science Foundation(Grant No.ZR2009FM003)
文摘Monotonic lateral load model tests were carried out on steel skirted suction caissons embedded in the saturated medium sand to study the bearing capacity. A three-dimensional continuum finite element model was developed with Z_SOIL software. The numerical model was calibrated against experimental results. Soil deformation and earth pressures on skirted caissons were investigated by using the finite element model to extend the model tests. It shows that the ＂skirted＂ structure can significantly increase the lateral capacity and limit the deflection, especially suitable for offshore wind turbines, compared with regular suction caissons without the ＂skirted＂ at the same load level. In addition, appropriate determination of rotation centers plays a crucial role in calculating the lateral capacity by using the analytical method. It was also found that the rotation center is related to dimensions of skirted suction caissons and loading process, i.e. the rotation center moves upwards with the increase of the ＂skirted＂ width and length; moreover, the rotation center moves downwards with the increase of loading and keeps constant when all the sand along the caisson＇s wall yields. It is so complex that we cannot simply determine its position like the regular suction caisson commonly with a specified position to the length ratio of the caisson.
基金the Thailand Research Fund (TRF) for their financial support to this study
文摘Construction of seaside and underground wall bracing often uses stiffened deep cement mixed columns （SDCM）. This research investigates methods used to improve the level of bearing capacity of these SDCM when subjected to cyclic lateral loading via various types of stiffer cores. Eight piles, two deep cement mixed piles and six stiffened deep cement mixing piles with three different types of cores, H shape cross section prestressed concrete, steel pipe, and H-beam steel, were embedded though soft clay into medium-hard clay on site in Thailand. Cyclic horizontal loading was gradually applied until pile failure and the hysteresis loops of lateral load vs. lateral deformation were recorded. The lateral carrying capacities of the SDCM piles with an H-beam steel core increased by 3-4 times that of the DCM piles. This field research clearly shows that using H-beam steel as a stiffer core for SDCM piles is the best method to improve its lateral carrying capacity, ductility and energy dissipation capacity.
文摘The seismic capacity curves of three types of buildings including frame,frame-shear wall and shear wall ob- tained by pushover analysis under different lateral load patterns are compared with those from nonlinear time history analy- sis.Based on the numerical results obtained a two-phase load pattern:an inverted triangle(first mode)load pattern until the base shear force reaches β times its maximum value,V_(max)followed by a(x/H)~α form,here β and α being some coeffi- cients depending on the type of the structures considered,is proposed in the paper,which can provide excellent approxima- tion of the seismic capacity curve for low-to-mid-rise shear type buildings.Furthermore,it is shown both the two-phase load pattern proposed and the invariant uniform pattern can be used for low-to-mid-rise shear-bending type and low-rise bending type of buildings.No suitable load patterns have been found for high-rise buildings.
基金Project(104244) supported by the Natural Sciences and Engineering Research Council of Canada
文摘A developed stereo particle image velocimetry(stereo-PIV) system was proposed to measure three-dimensional(3D) soil deformation around a laterally loaded pile in sand.The stereo-PIV technique extended 2D measurement to 3D based on a binocular vision model,where two cameras with a well geometrical setting were utilized to image the same object simultaneously.This system utilized two open software packages and some simple programs in MATLAB,which can easily be adjusted to meet user needs at a low cost.The failure planes form an angle with the horizontal line,which are measured at 27°-29°,approximately three-fourths of the frictional angle of soil.The edge of the strain wedge formed in front of the pile is an arc,which is slightly different from the straight line reported in the literature.The active and passive influence zones are about twice and six times of the diameter of the pile,respectively.The test demonstrates the good performance and feasibility of this stereo-PIV system for more advanced geotechnical testing.
文摘The scrap tire rubber pad(STRP)made by natural or synthetic rubber and high strength reinforcing cords exhibits substantial vertical stiffness and horizontal flexibility,and these properties can be regarded as suitable for seismic isolators for structures.The use of environmentally burdensome scrap tires as STRP isolators might be convenient as an efficient and low-cost solution for the implementation of aseismic design philosophy for low-to-medium rise buildings,especially in developing countries.Finite element analyses of unbonded square and strip-shaped STRP isolators subjected to a combination of axial and lateral loads are conducted to investigate its lateral deformation performance under seismic loading.The rubber of the isolator is modelled with Mooney-Rivlin hyperelastic and Prony viscoelastic materials,including the Mullins material damage effect.The influence of the length-to-width ratio and bearing height on the isolator performance is assessed in terms of the force-displacement relationship,horizontal stiffness,damping,and isolation periods.It is shown that the dependence of stiffness on the length-to-width ratio is significant in the longitudinal direction and minor in the transverse direction.The STRP isolators following the proposed design criteria are shown to satisfy the performance requirement at different levels of seismic demand specified by the ASCE/SEI 7-2010 seismic provisions.
基金Project supported by the National Natural Science Foundation of China(Nos.50809060 and 51579218)the Fundamental Research Funds for the Central Universities,China(No.2011QNA4013)。
文摘An empirical approach has been developed to analyze the nonlinear response of a pile group with arbitrarily distributed piles subjected to combined lateral and torsional loading.In this approach,the concept of instantaneous twist center is applied to analyze the displacement relationship of pile heads and establish the static equilibrium equations of the pile cap.The horizontal interaction among the individual piles is considered through the generalized p-multiplier.The coupling effect of lateral resistance on the torsional resistance of each pile is quantified using an empirical factorβ;the lateral and torsional nonlinear responses of individual piles are modeled by p-y andτ-θcurves,respectively.The proposed approach not only captures the most significant aspect of the group effect and coupling effect in a pile group subjected to combined lateral and torsional loading,but also automatically updates p-multipliers of individual piles based on pile cap displacements.The proposed approach was verified using results of model tests on pile groups subjected to lateral loading,torsional loading,and combined lateral and torsional loading,separately.In general,the pile cap response and the transfer of applied loads in the pile groups agree well with the test results.
基金the National Natural Science Foundation of China(11772216,12072219 and 11902215)。
文摘The dynamic response and energy absorption performance of foam-filled tubes under lateral external blast loading were investigated experimentally and numerically.A series of blast tests for the foam-filled tubes with different geometric parameters were carried out by the use of the ballistic pendulum system.Experimental results were compared with the numerical simulation results employing the software ABAQUS.The results showed that the finite element(FE)analysis was in good agreement with the experimental data.The effects of the diameter and wall thickness of the outer tube,the TNT explosive charge mass,and the standoff distance on the deformation modes,the blast resistance,and the energy absorption performance of the foam-filled tubes were investigated.Three deformation modes of the foam-filled tubes were observed under the lateral external blast loading,including local plastic deformation,large plastic deformation with an elliptic shape,and the tearing of the outer tube.The result revealed that the introduction of the foam core played a vital role in the deflection and energy absorption capacity of the structure.This study provided effective guidelines for designing foam-filled tubes with high energy absorption efficiency.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.51808112,51878160,and 52078128)the Natural Science Foundation of Jiangsu Province(Grant No.BK20180155).
文摘The existing studies have primarily focused on the effect of cyclic load characteristics(namely,cyclic load ratio and amplitude ratio)on cyclic lateral response of monopiles in sand,with little attention paid to the effect of pile−soil relative stiffness(K_(R)).This paper presents a series of 1-g cyclic tests aimed at improving understanding of the cyclic lateral responses of monopiles under different pile−soil systems.These systems are arranged by two model piles with different stiffness,including four different slenderness ratios(pile embedded length,L,normalized by diameter,D)under medium dense sand.The K_(R)-values are calculated by a previously proposed method considering the real soil stress level.The test results show that the lateral accumulation displacement increases significantly with the increment of the K_(R)-value,while the cyclic secant stiffness performs inversely.The maximum pile bending moment increases with the cycle number for the rigid pile−soil system,but shows a decreasing trend in the flexible system.For an uppermost concern,an empirical model is proposed to predict the accumulated displacement of arbitrary pile−soil systems by combining the results from this study with those from previous experimental investigations.The validity of the proposed model is demonstrated by 1-g and centrifuge tests.
文摘This research investigates the behavior of a 2×2 pile group under two-directional lateral loads in addition to the vertical load.Through three-dimensional numerical modeling based on Flac 3D software,the study examines the total bearing capacity and efficiency coefficient of the pile group,considering factors such as the angle of lateral load,relative pile spacing,and relative stiffness of the pile-soil system.The findings highlight the significance of these factors in understanding and predicting the response of pile groups to changing lateral load directions.The results reveal that increasing the angle of the lateral load from 0°to 45°enhances both the maximum total lateral load and the efficiency coefficient of the pile group.When the relative stiffness of the pile-soil system significantly increases,soil stiffening occurs and reducing the relative spacing of the piles from 7 to 3 times the diameter of the piles diminishes the influence of the pile group.Consequently,the response of the pile group to lateral loads becomes more linear,with only a slight alteration in the maximum total lateral load and the efficiency coefficient when the lateral load is angled from 0°to 45°.Conversely,increasing the relative distance between the piles,specifically from 3 to 7 times the diameter of the piles,amplifies the influence of the pile group.Both the maximum total lateral load and the efficiency coefficient of the pile group exhibit an observed increase.These provide insights for designing pile groups and optimizing their performance under lateral loading conditions.
文摘The capability of piles to withstand horizontal loads is a major design issue.The current research work aims to investigate numerically the responses of laterally loaded piles at working load employing the concept of a beam-on-Winkler-foundation model.The governing differential equation for a laterally loaded pile on elastic subgrade is derived.Based on LegendreGalerkin method and Runge-Kutta formulas of order four and five,the flexural equation of long piles embedded in homogeneous sandy soils with modulus of subgrade reaction linearly variable with depth is solved for both free-and fixed-headed piles.Mathematica,as one of the world’s leading computational software,was employed for the implementation of solutions.The proposed numerical techniques provide the responses for the entire pile length under the applied lateral load.The utilized numerical approaches are validated against experimental and analytical results of previously published works showing a more accurate estimation of the response of laterally loaded piles.Therefore,the proposed approaches can maintain both mathematical simplicity and comparable accuracy with the experimental results.
文摘In views of the limitations of the existing methods for calculating the pile foundation capacity, a back analysis approach of the m-value is introduced. In order to consider the sensitivity of pile behavior to the m-value,the relationships between the applied horizontal loads at pile head and the corresponding m-value along with the pile stiffness changes are studied. Based on statistics data from the extensive in-situ tests, the back analysis results suggest an exponential expression for the m-value in various soil conditions and horizontal displacements at pile head. This method is capable of providing an accurate m-value in calculating the pile responses under lateral loads.
基金supported by the Fundamental Research Funds for the Central Universities of China (Grant No.2011JBM269)the State Key Development Programof Basic Research of China (973 Project No.2012CB026104)the College Students Technology Innovation Experiment project in Beijing Jiaotong University
文摘Experiments about working mechanism and mechanical characteristics of the DX model pile foundation under lateral dynamic and static loading were conducted by using a model system of the dynamic frozen soil-pile interaction. The horizontal displacement-force relationship of the pile head and bending moment distribution along the body in frozen soils of different temperatures were discussed. According to test results, both the horizontal disp!acement-force relationship of the DX pile head and bending moment distribution of the DX pile body are smaller than that of equal-diameter piles under same lateral loads. The piles with different plate positions show different displacements and bending moments. This phenomenon is mainly related to the soil temperature and bearing plates locations. Thus, dynamic response analysis of the pile foundation should be taken into account.
基金Sponsored by the National Natural Science Foundation of China(Grant No. 50508012)
文摘In order to obtain a deeper understanding of the behavior of the structure under high wind load,this paper conducted an experimental study on a full-scale L-shaped single story light frame wood house under the uniform lateral load simulated using a gasbag.The investigation involved the performance of light frame wood structure after it experienced the repeated cyclic lateral wind load as well as the performance of the structure under the ultimate lateral load.Then,the study verified that light frame wood structure can resist repeated cyclic wind loads without observable degradation in stiffness during the anticipated serve life,and recommended shear wall percent drift restriction for lateral wind load design of wood structure in serviceability limit states is 1/400 drift,and in ultimate limit states is 1/80 drift.The conclusions of this paper can be benefit for the engineering practice of the light frame wood structures in high wind load regions.
文摘A finite element method based program has been developed to perform the static nonlinear analysis of pile group with six different configurations subjected to lateral loads. The pile has been assumed to remain elastic all the time whereas the soil has been assumed to undergo plastic yielding following von Mises yield criterion. The formulation of elasto-plastic analysis following von Mises yield criterion has been explained. The effect of Drucker-Prager and Mohr Coulomb yield criteria on the response of pile group is also investigated. The whole analysis is based on incremental load application. The external load is applied in small increments and the stresses are initially computed assuming elastic constitutive relation. Significant effect of soil nonlinearity is observed at smaller pile spacing which reduces with increase in spacing.
