Pile Moment Research Articles

Influence of local scour on the dynamic response of bridges under barge collisions

The response assessment of bridges crossing navigable waterways under vessel collisions is commonly conducted assuming intact bridge models. However, local scour may occur at bridge foundations, which has been identified as one of the major hydraulic causes of bridge failures. Therefore, it is imperative to consider local scour in the design and analysis of bridges against vessel collisions. Many previous studies have focused on the bridge response under vessel collisions assuming deterministic scour depths with incremental values, without integrating a scour prediction modeling in the analysis. This work investigates the barge-bridge collisions in the presence of scour at pile foundations, by using empirical scour prediction models. The accuracy of each prediction model is evaluated using relevant laboratory test and field measurement records. Finite element (FE) models of a four-span continuous reinforced concrete (RC) bridge and a jumbo hopper barge are developed in LS-DYNA. The current study identifies the correlation between the upstream flow depth and the barge collision location in the analyses. Numerical results illustrate that both scour depth and collision location influence the displacement, shear force, and bending moment response of bridge piles. The struck bridge pier accommodates a considerably increased displacement with an increased scour depth, while the shear force and bending moment are primarily influenced by the collision location. The influence of scour on the barge-pier collision force is marginal. The maximum axial force in soil springs increases considerably with scour depth. The choice of scour prediction model shows a significant impact on the displacement, shear force, bending moment of piles, the displacement of struck pier, and the axial force of soil springs.

Numerical Simulation of Double-row Piles in Deep Foundation Pit Excavation

This paper aims to investigate the stress and deformation characteristics of double-row piles in deep foundation pit excavation by selecting representative strata in the Changchun area. The changes in bending moment, displacement, and earth pressure of double-row piles during the excavation are established using the FALC 3D software. The findings indicate that the deformation of the front pile is larger than that of the back pile, and the earth pressure distribution of the fornt pile deviates from the conventional Rankine earth pressure theory. Moreover, there are noticeable variations in earth pressure at the soil layer interface of the rear pile.

Numerical analysis of horizontal bearing capacity of pile in clay slope

In this study, a series of numerical calculations were performed to investigate the lateral behavior of piles in slopes and in horizontal ground. First, a numerical model is created and then verified by comparing the numerical results with the results of model tests. The numerical results agree well with the results of model tests. Second, numerical calculations of different slopes were conducted to explore the effect of slope angle on the horizontal displacement of pile and bending moment. Then, the effect of slope angle on the foundation stiffness proportional coefficient m is investigated. The stress distribution of soil around the pile and the deformation of pile at different slope angles are also compared. Finally, the p–y curves of the different slope angles are compared. An improved p–y method is proposed to consider the effect of slope angle based on the numerical results. The results show that the bearing capacity of piles decreases with an increase in slope angle. The horizontal displacement of pile nonlinearly decreases along the pile body with the depth of pile. The bending moment of piles increases along the pile body with an increase in pile depth, and until 0.5 times of the pile length, the bending moment reaches the maximum value. As the slope angle increases, the maximum of bending moment tends to decrease. The distance from the slope toe to the pile section has a little influence on the pile bending moment and horizontal displacement. With an increase in slope angle, the horizontal foundation coefficient m gradually decreases.

Numerical Analysis of the Influence of Deep Excavation on Nearby Pile Foundation Building

In this paper, a numerical simulation is used to establish a three-dimensional model, which considers the height of buildings, the relative position between buildings, and foundation pits. These were studied in detail to investigate the changes in settlement of adjacent buildings and the displacement and internal force of piles caused by deep foundation pit excavation. The results indicate that the number of floors in the building, along with the angle and distance between the building and the excavation pit, have a significant impact on the settlement of the building and the deformation and internal force variation in the piles. For example, when D = 0.1 H, with the increase in the number of floors, the increase in the bending moment of pile 1 at the pile shaft is 62.63 kN·m, and the increase in the bending moment at the pile head is 224.72 kN·m. At this point, the maximum horizontal displacement of the pile shaft occurs at approximately 1.27 H. When θ = 45∘, the maximum difference between the maximum and minimum deformations of the building is 9.71 mm. When D ≤ 1.0 H, the majority of the building is in the primary influence range of surface settlement behind the wall, and the building undergoes a combined deformation of ‘upper convex’ and ‘concave’. When D > 1.0 H, the building predominantly resides in the secondary influence range, and the building undergoes a deformation of ‘upper convex’.

Influence of pile length on dynamic performance of monopile wind turbine

The influence of pile configuration on safety of wind turbines has been attracting large amounts of attention recently. On the one side, the cost for the foundation accounts for 35 % of the total cost of monopile supported wind turbines (MWTs). On the other side, the working environment of wind turbines brings complex loads to monopiles. In this paper, a series of wind tunnel tests are performed with scaled model under different ground and operation conditions. The test results show that pile length factor (PLF) affect nacelle displacement and maximum pile moment negatively. Top acceleration confirmed a stationary random vibration. The natural frequency of model MWTs increases 11.6 % (dense ground) and 10.1 % (loose ground) when PLF increase from 0.264 to 0.362. While damping ratio decreases 1.447 % (dense ground) and 1.493 % (loose ground). These test results can be up scaled to estimate prototype's dynamic properties. According to test results, some numerical fitting surfaces including d-Ω-PLF, f-Ω-PLF and ξ-Ω-PLF have been established to check unfavorable working conditions, which can be used to guide the design of piles to support MWTs.

Impact of Tunneling on Adjacent Piles Based on the Kerr Foundation Model Considering the Influence of Lateral Soil

The Kerr foundation model simulates the interaction between piles and soil. Considering the impact of lateral soil displacement on adjacent piles, the lateral displacement and bending moment of the adjacent piles caused by shield tunnel excavation are calculated in detail. Additionally, the reactions of groups of piles are obtained by focusing on the shielding effect of the piles on the soil displacement caused by shield tunnel excavation. The validity of the solutions is verified by comparing the calculated results with the boundary element program GEPAN. Additionally, adjacent pile lateral displacement and bending moment are compared, with and without considering lateral soil effects. Furthermore, this study investigates the influence of various factors, such as soil spring stiffness, pile–tunnel distance, ground loss ratio, and pile diameter on the pile group’s lateral displacement and bending moment. The research findings indicate that increasing the soil spring stiffness or the horizontal distance between the pile and tunnel can reduce the lateral displacement and the bending moment of the pile. On the other hand, as the ground loss ratio gradually increases, the pile lateral displacement and bending moment will also increase. However, when the diameter of the pile grows, the lateral displacement reduces, while the bending moment increases.

Effect of Shield-Tunnel Construction on the Horizontal Response of Adjacent Piles in a Silty Layer

This paper studies the problem of shield tunnels laterally passing through piles based on in situ tests and numerical methods. The effects of vertical load, pile–tunnel distance, and tunnel-cover depth on the horizontal displacement and the bending moment of adjacent piles were investigated. The results show that the shield tunnel induced adjacent pile displacement toward the tunnel side near the tunnel axis, and the soil below and above the tunnel axis constrained the pile, displacing toward the tunnel side. The maximum values of the horizontal displacement and bending moment were at the tunnel axis. The vertical load on the cap had little influence on the horizontal response of the pile. The main influence area induced by shield construction was located within 1.5 times the tunnel diameter. The maximum horizontal displacement and maximum bending moment were reduced by 36–45% and 45–78% on the far pile due to the shading effect induced by the near pile. The tunnel-cover depth had a significant influence on the distribution patterns of the horizontal displacement and the bending moment. The positions of the maximum horizontal displacement and the maximum bending moment moved downward with increases in tunnel-cover depth. The maximum horizontal displacement and bending moment increased with increases in tunnel-cover depth.

Seismic response and failure modes analysis of pile foundations in liquefiable soils using various design criteria

Pile foundations may fail by bending, shear forces and buckling etc., if soil surrounding the pile liquefies during earthquake. In this paper, a detailed 3D numerical model was developed based on the Showa Bridge that collapsed during the Niigata earthquake, estimations have been made of the times that the Showa Bridge collapsed based on a soil and pile seismic response. Then, seismic design criteria of pile foundations corresponding to different failure modes are selected, it is found that the pile of Showa Bridge may have fail by buckling. Furthermore, the effects of the pile flexural rigidity, earthquake type, peak ground acceleration, and degree of soil layer liquefaction on the ground and pile response in liquefiable soil are examined. The peak bending moment of pile and pile top displacement increases with increasing degree of soil layer liquefaction. Finally, evaluates those criteria by comparing and contrasting the results in various conditions. Nonlinear discriminant methods considering the effect of pore pressure distribution can identify different failure modes with higher reliability compared to those obtained by linear theories., and suggested flowchart of evaluating bearing capacity of pile in liquefiable soils was purposed It is recommended that develop a more comprehensive theory of pile foundation failure discrimination.

Evaluation of the dynamic behavior of pile groups considering the kinematic force of the slope using centrifuge model tests

In this study, dynamic centrifugal model tests were performed by installing a pile group on the slope to examine the effect of the kinematic force of the slope on the pile. Based on the results of this experiment, a method for calculating the slope kinematic force applicable to the pile foundation was derived, and the pseudo-static analysis was performed. The results showed that the moment difference from the experiment occurred at the top of the pile by 14-49% in the analysis model without ground kinematic force, but decreased to 3-35% when the ground kinematic force was considered. In particular, in the lead pile, which is most affected by the ground kinematic force, the moment difference was less than 20% when the ground kinematic force was considered, indicating that the pile moment by depth was most appropriately simulated.

Time dependent analysis of lateral bearing capacity of reinforced concrete piles combined with corrosion and scour

This study investigates the effect of chlorine corrosion and flow scour on the lateral bearing capacity of piles. A chloride diffusion model was established to obtain the initial corrosion time of reinforcement based on Fick's second law. The degradation of stiffness after corrosion is represented by a reduction coefficient. The finite difference method is used to solve the deflection differential equation of laterally loaded piles. The maximum scouring depth of piles in cohesive soil and the variation of scouring depth with time are calculated by empirical model. The calculated results from the analytical solution revealed that the pile stiffness decreases with the exposure time. As the time increase, the lateral displacement and shear force decrease on the other hand the bending moment increases. The increase of flow velocity and pile diameter results in the increase of the maximum scour depth around the pile. The bending moment, shear force, and lateral displacement of piles after scour increase significantly compared to the lateral bearing performance of piles before scour.

Numerical Simulation of Piles in a Liquefied Slope Using a Modified Soil–Pile Interface Model

The liquefaction of soil surrounding a pile significantly affects the dynamic interaction between the soil and the pile. In particular, liquefaction of the sloping ground can induce permanent deformation and a bending moment on the pile due to the lateral displacement of the liquefied soil in the downslope direction. However, numerical analysis studies on piles installed in a liquefiable slope have been very limited and have not properly simulated the behavior of the pile. Therefore, a modified soil–pile interface model was proposed, which linearly decreases the interface friction angle with the increase in the excess pore pressure ratio. The proposed model was validated by comparing it with the centrifuge test results of Yoo et al. (2023). Simulation results on the slope crest settlement and the pile-bending moment showed good agreement with the centrifuge test results. A parametric study was conducted by applying the validated model to analyze the effect of slope inclinations and the amplitude of input motions on the slope displacement and the pile moment. The simulation results showed that the slope inclinations affected the area of the sliding mass, causing a larger pile-bending moment with a larger inclination. When the amplitude of the input motion was sufficiently large to trigger the failure of the liquefied slope, the slope displacement and the pile-bending moment did not increase any further.

Effects of Soil–Structure Interaction on Performance of Bridges During Earthquakes. Case Study: Integral Abutment Bridge in Pennsylvania, USA

Bridges are among the most important transportation elements that may be damaged by earthquakes. An integral abutment bridge (IAB) is a bridge linking the superstructure directly to the substructure. As soil piles, abutments, and superstructures act as a combined system to resist lateral loading on the bridge, soil stiffness has a major impact on load distribution. This research attempts to determine how the structure and soil parameters affect the IABs. The parametric study consists of four variables, namely bridge span (short, medium, and large spans were 18.3, 35.4, and 64.5 m, respectively), backfill height/pressure (3.1, 4.6, and 6.1 m, respectively), stiffness of soil mixture backfills (high, intermediate, and low), and soil density around the piles (high, intermediate, and low). Because of the small width–length ratio of the bridge, a 2D model of an IAB with soil springs around the piles and abutments was developed with finite element software. Findings show that the value of the backfill pressure affects girder axial forces and girder bending moments at the IAB. Also, the stiffness of soil mixture backfills is an important factor to change lateral displacements, while less movement is related to high stiffness of soil mixture backfills with intermediate clay around the pile. It is clear that the maximum axial girder moments at the superstructure generally decrease when the stiffness of the soil mixture behind the abutments and around piles increases, similar to pile deflection and abutment displacements. In addition to maximum abutment, the head moment decreases when abutment backfill is dense and increases when piles are located in hard clay, similar to pile moments. Lastly, dense sand backfill behind abutments is recommended since it decreases pile deflections, pile lateral forces, abutment displacements, abutment head moments, and particularly pile bending moments.

Mechanical Property of Lateral Piles for Pile Composite Foundation Loaded by Model Test

Under vertical load, the composite foundation may be damaged due to insufficient lateral restraint capacity. If the lateral restraint pile is added to the edge of the composite foundation, the lateral stability can be effectively enhanced. This new reinforcement scheme is called a combined composite foundation. For the combined composite foundation, the lateral restraint piles will bear a certain force when the composite foundation is loaded, and the force may cause the piles horizontal displacement, instability, or even failure. After preload on the composite foundation, the mechanical behavior of lateral restraint piles will be more sophisticated. To study the mechanical behavior of lateral restraint piles under such condition, a laboratory model test was conducted. The results are suggested as follows: Axial force distribution curves tend to be “S” shape with two peak values at the upper and lower parts, respectively. The negative axial force is distributed at the upper part, and the positive axial force is distributed at the lower part. The bending moment and lateral soil pressure distribution of piles appear with the regularity of “increase-decrease” along the depth. Such a phenomenon is associated with the expansion of a potential slip surface. In accordance with the relative location of the potential slide surface and the piles, the lateral restraint piles can fall into three sections. Different sections get different stresses. The reinforcement scopes have an impact on the stress of different lateral restraint piles. With the increase of the reinforcement scope, the axial force, soil pressure, and bending moment show the regularity of increase. The values of axial force, the lateral soil pressure, and the bending moment increase with load growth and become stable when the load is larger than 60 kN. This is associated with the piles in the composite foundation, which verifies the reinforcement effect to prevent the soil slide and the foundation deformation.

Finite element analysis on dynamic behavior of sheet pile quay wall dredged and improved seaside subsoil using cement deep mixing

Sheet pile wall structures are commonly applied in coastal projects, particularly for the quay wall. This structural type normally is used in places where the ground has a low bearing capacity and is easily penetrable. Many sheet pile quay walls constructed in the past had low front water depth and did not satisfy the requirements of current standards. This issue could be addressed by improving the ground in front of the wall using cement deep mixing (CDM) and then excavating to increase the water depth in front of the wall. This paper numerically evaluated the dynamic behavior of the sheet pile wall after renovation. The numerical model was performed based on the finite element method (FEM) using the PLAXIS 2D program. The study focused on investigating typical parameters of the quay wall improved using the CDM, such as bending moment and displacement of sheet pile and the development of excess pore water pressure (EPWP) in the backfill. These results were compared to those of the quay wall without the CDM to elucidate the advantages of this method. In addition, the influence of some factors on the quay wall behavior, such as earthquake excitation characteristics, CDM area, and CDM strength, was also evaluated. The results demonstrated that the ground improvement using the CDM significantly decreased the bending moment and displacement of the sheet pile wall. The excitation characteristics did not affect the deformed shape of the sheet pile. With the constant CDM depth, the sheet pile displacement decreased with an increase in the improvement width until it reached a limitation. The increasing CDM strength also decreased the displacement of the wall until it raised a certain value. This demonstrated that this method was technically feasible, and it could be considered to study further by experiment before applying in practice.

Numerical analysis of laterally loaded barrette foundation

The effect of soil constitutive models, nonlinearity of the barrette material, loading direction as well as the cross-sectional shape and second moment of inertia on the response the barrette foundation under lateral loading is investigated in this research. The numerical analyses were conducted on a well-documented barrette load test using Plaxis 3D. The investigation results revealed that the response of the barrette is significantly affected by the direction of the applied load and nonlinear behavior of the soil and barrette materials. For rectangular, square, and circular piles with different cross-section areas and same second moment of inertia, the square and circular piles exhibit similar behavior but different from that of the rectangular pile. However, when these piles have the same cross-section area and different second moments of inertia, the behavior of rectangular pile is close to that of square pile when the load is applied along the x direction and is close to that of circular pile shape when the load is applied along the y direction.

Durability life prediction and horizontal bearing characteristics of CFRP composite piles in marine environments

In this paper, the durability life and horizontal bearing characteristics of carbon fiber reinforced polymers (CFRP) composite piles in marine environments are studied. The durability life of CFRP composite piles is divided into the initial corrosion stage of reinforcement and the crack propagation stage of concrete protection layer. The chloride diffusion model and Monte Carlo simulation method are used to predict the initial corrosion time of CFRP composite piles. Based on the thick-walled cylinder theory, the critical corrosion depth of the reinforced steel corresponding to the cracking of concrete protective layer is deduced. The durability life prediction model of crack propagation stage is established. The flexural stiffness reduction factor of CFRP composite piles with different replacement ratios is obtained by conducting the model pile bending tests. The attenuation law of bending stiffness and horizontal bearing characteristics of CFRP composite piles in marine environments are analyzed. The results show that the higher the replacement ratio of CFRP bar, the slower the reduction rate of flexural stiffness of CFRP composite pile is. Under the same buried depth, the pile bending moment and shear force of CFRP composite piles decrease with the increase of CFRP reinforcement replacement ratio. The horizontal displacement of CFRP composite piles increases with the increase of CFRP reinforcement replacement ratio.

Research on Mechanical Characteristics of Slope Reinforcement by Spatial Arc Crown Beam Composite Supporting Structure

To effectively optimize the mechanical behavior of a traditional anti-slide pile and reduce environmental destruction, a new method for slope reinforcement by a spatial arc crown beam composite supporting structure was proposed. First, a numerical model was validated through lab-scale model test data obtained herein, and then a full-scale numerical model was created for an in-depth understanding of the distribution regularity of displacement along the pile, the soil pressure, the crown beam stiffness, and so on. The results demonstrated that: (1) The spatial arc crown beam is simplified to a two-hinged arch, and the maximum value of the bending moment in the arc crown beam is about one-third of the straight crown beam through theoretical calculation. (2) The spatial arc crown beam redistributes the load sharing among different piles, and the extreme bending moment of other piles varies within 10% along the downhill direction except for the piles at the slope foot. (3) Bending moments are close to zero at the pile end, and the anti-slide pile can be simplified as a vertical beam with one end fixed and the other end hinged. (4) The axial force in the spatial arc crown beam is always presented as pressure, so the crown beam can make full utilization of the compression resistance of concrete. (5) The distribution characteristic of soil pressure in front of the pile at the arch foot is different from that in other positions, and the stable soil at the slope foot provides greater soil resistance for anti-piles. (6) As the crown beam stiffness is above five times the reference value, the axial force of the crown beam tends to be stable, and as the crown beam stiffness increases continually, the maximum value of My is −1013.13 kN·m, and the constraining effect of the crown beam is gradually weakened.

Application of a damage constitutive model to pile–slope stability analysis

Piles were regarded as elastic materials in the traditional numerical simulation. The elastic pile would not reflect the damage of the pile in engineering, which would misjudge the reinforcement effect of piles on slopes. The specific objective of this study was to propose a damage constitutive model to replace the traditional elastic constitutive model in the numerical analysis of pile–slope stability. In this study, the pile was simulated by a damage constitutive model, which can reflect the plastic deformation of the pile. The factors of pile position and reinforcement ratio on a slope’s factor of safety (FOS) are investigated by the finite difference method using FLAC3D. The lateral displacement, bending moment, shear force, and soil pressure of balance-reinforced piles are used to study the difference between damage and elastic constitutive models. The results showed that the FOS considering the damage constitutive model could be smaller, approximately 15% less than that considering an elastic constitutive model under specific conditions. Furthermore, the difference between the two evaluation results of the internal force of the same pile can reach about 30%. It was observed that the elastic constitutive model would overestimate the reinforcement effect of the pile on the slope, which will cause potential safety hazards in engineering. This study provides a realistic damage constitutive model for the design and evaluation of slope-stabilizing piles.

Numerical simulation of the experiment on testing a group of piles using different models of soil base

In the paper, the influence of the selected model of the soil environment on the stress-strain state (SSS) of the pile foundation is studied. The following issue sare considered: 1) analysis of the main models of the soil environment, widely used in modeling the interaction of foundations with soil foundations; 2) Numerical modeling of the stress-strain state of the "base – pile foundation" system was performed using foundation models in the form of: variable stiffness coefficients, volume tricelastic and elastic-plastic elements of the soil mass; 3) a comparison of the SSS of a pile foundation obtained by numerical modelingusing various foundation models and verification of the results by comparing with the data of a field experiment of testing a group of piles is given. This study is based on field experiments on testing full-scale piles, conducted by prof. Bartolomey A.A. and colleagues. In the experiment, a groupof 9 piles with a length of 5 m and a section of 30x30 cm was driven into the ground. The piles were combined with a reinforced concrete grillage. Numerical modeling of the stress-strain state of the system "base - pilefoundation" was carried out using the SP "Lira – SAPR 2019".
 It was revealed that the calculated values of longitud in alforces in piles modeled by rod elements, and the interaction with the base of the base stiffness factors simulated by variables give good convergence with the data of experimental studies. The error for all experimental fields in a wide range of loads is up to 20%. When determining the value of the variable stiffness coefficients, it is necessary to refine the miteratively more than 3 times. The disadvantage of modeling the foundation with variable stiffness factors is the difficulty in obtaining the correct values of bending moments in piles. When using a soil foundation model in the form of volumetric elastic finite elements, the error in determining the longitudinal forces in piles is up to 45%, and the use of elastic-plastic volumetric soil elements increases the accuracy of the calculation. After comparing the calculated and actual values of piles ettlement, we observe an excellent correlation of the results in the variant of the numerical model using volumetric elastic-plastic finite soil elements with the Mohr-Coulomb strength criterion. The error is within 0.8 ... 2%. The use of the model of volumetric elastic elements of the soil massif leads to an under estimation of settlement in piles within the range of up to 8%. The model using variable foundation stiffness factors also under estimates settlement in piles by up to 15%.

Dynamic and Residual Pore Water Pressure Response of Hybrid Foundation System Under Combined Action of Wind, Wave and Seismic Loading

The dynamic response characteristics of the innovative marine wind power hybrid foundation under combined action of wind, wave and seismic loading are studied in this article. Taking the monopile foundation as reference group, the shearing strain-volumetric strain coupled pore pressure incremental constitutive model was utilized to simulate the kinetic behavior of seabed’s saturated soil. The pressure distribution and variation characteristics of residual pore water pressure around pile foundation due to the interactions of upper structure, foundation and saturated soil are illustrated. The results indicate that: (a) the cylindrical platform changes the residual pore water pressure and accelerates the pressure accumulation area, which converts from surrounding the monopile to nearby the cylindrical platform; (b) compared to the hybrid foundation, the peak value of residual pore water accumulation of the monopile foundation is smaller only under seismic loading, which is due to that the monopole with smaller stiffness is more vulnerable to deform with soil synergistically; (c) the cylindrical platform structure can significantly reduce the horizontal placement extreme of pile foundation under the action of dynamic load, and can also change the distribution characteristics of bending moment of middle pile of the hybrid foundation. It is manifested by a lower bending moment extreme of the middle pile near the mudline under the action of wind and wave loading, while the seismic loading could increase the bending moment extreme of middle pile near the mudline.