Search

The load transfer mechanism of laterally loaded pile groups is very complicated, and the analysis method is affected by many factors. This paper presents a field test study on lateral responses of large diameter cast-in-place isolated single piles with free head and pile groups with fixed head to investigate the pile group effect. Boreholes are drilled, and relevant field and laboratory tests are carried out to obtain main physical mechanical parameters and the soil profile of the site. Results of lateral loads, lateral displacements and bending moments measured in the field are reported and discussed. A group efficiency factor-based calculation method applicable to laterally loaded pile groups is derived according to a series of full scale and centrifuge tests. An existing group efficiency factor-based calculation method is compared with the proposed method. And three other measured test results are used to verify the calculated results. The comparison results show that the proposed method provides good predictions of load–displacement responses of pile groups. [ABSTRACT FROM AUTHOR]

In general, pile foundations are utilized to support structures like tall buildings, bridges, and transmission towers, which are frequently subjected to lateral stresses initiated by wind, action of waves, earthquakes, or traffic loads. Several high-rise structures, highway and railroad overpasses, as well as transmission towers, are constructed near slopes and rely on pile foundations for support. Due to the effects of wind and waves, pile foundations are continuously subjected to cyclic loads. For piles supporting tall buildings, transmission towers, offshore structures, or infrastructure in seismic zones, 1-way or 2-way cyclic lateral loads are commonly applied. Therefore, while designing pile foundations, it is essential to understand how piles behave laterally when they are located near a sloping crest. One of the primary challenges in ensuring the efficient functioning of the superstructure is analyzing how the soil and foundations respond when exposed to long-term lateral loads, such as wind, over an extended period on the piles of offshore platforms. Because of the presence of slope, the pile's lateral load capacity decreased due to the reduced ability of the soil to provide passive resistance. This paper presents small-scale 1-g model tests conducted on the sand to assess the loss of pile's lateral capacity when subjected to 100 cycles under 1 and 2-way cyclic loading. The Relative Density (60%) and varying slopes (Horizontal ground, 1V:3H) with varying spacing (5D and 7D) and aspect ratios (L/D) of 25 and 40 were implemented in this study. Cyclic lateral load tests were performed for sloping as well as horizontal ground. A major reduction in lateral capacity, exceeding 60%, was observed due to the application of cyclic loading. Moreover, the transition from horizontal ground (HG) to sloping ground (SG) decreased the maximum bending moment by 25–40%. This study exemplifies the piles' behaviour when subjected to cyclic lateral loading while resting on a sloping crest, which represents a critical scenario in pile foundation design. [ABSTRACT FROM AUTHOR]

In this study, numerical analyses of connected and disconnected piled-raft foundations (PRFs) comprising a single pile, 2 × 1, 3 × 1, 2 × 2, 3 × 2, 3 × 3 and 5 × 5 pile groups subjected to different lateral loads, with a constant vertical load, have been carried out by three-dimensional finite-element analysis. Results from the analysis have been validated with reported field studies considering vertical load and reported experimental studies considering lateral load. The reported multilayered sub-soil profile has been considered for the analysis. Parametric studies in terms of the effect of variation in pile length (L/d = 20, 30, 39), spacing of piles in the pile group (S/d = 3, 5, 6), number of piles, thickness of raft (0.5, 1.2 and 2 m), variation of axial force, excess pore water pressure, bending moment and shear force along the depth of the piles for connected and disconnected PRFs have been discussed for a time period of 20 years. The horizontal connected piled-raft coefficients have been determined corresponding to the lateral deflections. A generalised equation has been predicted for the horizontal connected PRF coefficient. [ABSTRACT FROM AUTHOR]

In this paper, an experimental, numerical and analytical study is conducted on a 2 × 1 bored pile group on saturated sand under combined loading. Initially, a single-degree-of-freedom system founded on the pile group is tested at the ETH Zurich drum centrifuge under vertical, lateral and pushover loading, gaining insights and deriving benchmark results for validation of finite-element (FE) models. The latter account for non-linear soil–pile interaction, using hypoplasticity for sand and appropriate modelling of interfaces and pile response. Combining centrifuge and FE modelling, the governing resistance mechanisms are identified and quantified. The transition from model to prototype scale is achieved after careful consideration of scale effects. The concrete damaged plasticity model is employed to model the non-linear response of the reinforced concrete (RC) piles, accounting for axial load dependency of bending moment capacity. The prototype problem is studied parametrically, deriving failure envelopes for different levels of vertical loading. Distinguishable failure modes are identified, and the contribution of different resistance mechanisms is quantified. Finally, analytical failure envelopes are derived based on limit equilibrium, expanding Broms' theory to pile groups under combined loading. Accounting for the axial load dependency of RC bending moment capacity, the proposed closed-form solutions provide a useful design tool for engineering practice. [ABSTRACT FROM AUTHOR]

Pile response in unsaturated soils is an area of interest due to its prevalence in real-world scenarios. Significant differences exist in the lateral behavior of single piles in partially saturated soils due to increased soil stiffness. In this study, a single pile was monotonically loaded laterally to investigate the performance of piles in soils with variable water table levels. Pile head lateral response showed that a mix of unsaturated-saturated soil led to an increase in lateral loads on the pile at a similar displacement compared with the fully saturated or dry soil conditions. The lateral response of the pile was obtained based on the curvature data from the strain gauges. A derivative method was used to generate the shear force and lateral resistance along the pile length based on finite differences at the seven strain gauge locations, thereby eliminating errors associated with curve fitting. Various lateral response plots, such as the normalized p-y curves, M-y curves, and maximum bending moment response plots, were used to assess the response to lateral load. Further, the effect of two different loading rates were assessed on the fully saturated and unsaturated-saturated soil, and the range of loading rates evaluated had minimal influence on the pile lateral response. Results indicated that considering the influence of the unsaturated soil could increase lateral resistance under similar lateral displacements. However, there is a risk of inducing large pile bending moments, potentially leading to pile flexural failure if the pile plastic moment is reached. [ABSTRACT FROM AUTHOR]

Cracks develop in concrete piles under lateral static loading as the tensile stress exceeds the concrete strength, causing a decrease in the pile's flexural rigidity and influencing the load–deflection behavior. This paper presents a three-dimensional finite-element analysis (FEA) performed by PLAXIS 3D (version 2021) to investigate the impact of concrete cracking on the load–deflection behavior of laterally loaded piles in rock mass. Two FEA models were established to assess the influence of concrete cracking on load–deflection behavior. In the first model, nonlinear rock mass behavior was coupled with linear pile behavior (FEANL), while in the second model, nonlinear rock mass behavior was coupled with nonlinear pile behavior (FEANN). The three-dimensional (3D) FEA models were verified with a full-scale test case study for a deep-water pile foundation. The FEANN yields a more accurate simulation of measured deflection than the FEANL. A single run of the FEANN typically requires an entire day of computational time. Thus, a simplified approach was proposed to minimize the computational time process by incorporating the relationship of the change in pile flexural rigidity versus the bending moment (EI–M) into FEANL. In addition, the available EI–M relationships in the literature, such as the American Concrete Institute (ACI) method and beam theory, were evaluated by the EI–M relationship derived from the FEANN. The beam theory yields a lower estimate of pile flexural rigidity than the ACI method. The predicted deflection obtained through the simplified approach exhibits good agreement with the measured deflection utilizing the EI–M relationship derived from the FEANN. On the other hand, the EI–M relationship obtained from the beam theory overestimates the deflection compared to those obtained from the EI–M relationships of the ACI method and FEANN. [ABSTRACT FROM AUTHOR]

Excavation of foundation pits can cause deformation and differential settlement to nearby pipe gallery structures, potentially resulting in significant issues such as seepage and structural damage. Based on a deep foundation pit construction project for a residential building plot adjacent to the Wuhan-Jiujiang utility tunnel, a three-dimensional finite element analysis model with cement-soil mixed wall (SMW) and trench cutting remixing deep wall (TRD)-drilled pile is established to study the impact of the excavation process on the utility tunnel. The results indicate that as the foundation pit excavation depth increases, the lateral deformation of the drilled pile support structure shows an initial increase followed by a subsequent decrease, and the maximum lateral deformation occurs at the point approximately one-third from the bottom of the foundation pit. Besides, the surface settlement exhibits an initial increase, followed by a subsequent decrease and eventual stabilization. The deformation of the utility tunnel structure causing by excavation is always within specified limit of 15 mm. Compared to the structure before excavation, the maximum values of axial force, shear force, and bending moment of the utility tunnel increases by 0.09%, 0.14%, and 4.88%, respectively. The stress variation is small, which satisfies the safety requirements for its usage, the feasibility of the TRD-drilled pile support structure is demonstrated. This study can serve as a reference for safety assessment of comparable engineering projects. [ABSTRACT FROM AUTHOR]

In this article, a nonlinear static analysis model of a bridge pile foundation is established using numerical simulation, and the correctness of the model is verified via experiments. Then, the damage characteristics and mechanical behaviors of bridge pile foundations in cold regions under lateral loads are investigated based on the validated analysis model. The results showed that the impact of soil freeze–thaw cycles on the lateral performance of the pile–soil system is more pronounced in seasonally frozen regions compared with permafrost regions. Specifically, as the number of soil freeze–thaw cycles increases, there is a tendency for the lateral load capacity of the pile–soil system to decrease initially and then stabilize. It is worth noting that soil freeze–thaw cycles significantly influence both the stiffness and deformation capacity of the pile–soil system, with these parameters exhibiting a decreasing trend followed by stabilization as the number of freeze–thaw cycles increases. However, it has little effect on the shear force and bending moment of the pile foundation. [ABSTRACT FROM AUTHOR]

Pile foundations may be subjected to a combination of vertical and lateral loads that are commonly not applied simultaneously. Model tests of six instrumented single piles embedded in remolded loess, in which self-developed equipment was used to carry out different loading sequences of vertical and lateral loads, were performed. The test results indicate that the preapplied lateral load can cause a decrease in the average skin friction of the pile shaft within 13 times the pile diameter below the ground surface, as well as an increase in the pile end resistance. The settlement of the pile top increases with the increase in the preapplied lateral load, and its rate of change increases with increasing vertical load and increasing preapplied lateral load. With the increase in the preapplied vertical load, both the horizontal displacement of the pile at the measuring point and the maximum bending moment of the pile shaft decrease. The location of the maximum bending moment of the pile shaft is between 2 and 4 times the pile diameter below the ground surface, which approaches the ground surface when the preapplied vertical load increases. The preapplied vertical load can increase the ultimate horizontal bearing capacity of the pile. [ABSTRACT FROM AUTHOR]

A screw micropile is a multi-sectional pile typically consisting of a smooth segment at the top, a threaded segment in the middle and a tapered segment at the bottom. Although the axial behavior of this pile type has lately been studied, response to lateral loading and contribution of the threads to lateral capacities are yet to be investigated. To facilitate the design of this pile type for applications where wind or seismic loads are concerned, there is a necessity to examine the lateral behavior and capacities of screw micropiles and effect of the threads on the lateral capacities. Hence, lateral load field test programs were carried out on six types of screw micropiles at two cohesive soil sites and a cohesionless soil site. Selected piles were instrumented with bending moment strain gauges along the pile shaft. A geotechnical site investigation was carried out at each site to obtain soil profiles and properties. The lateral load versus displacement curves and the bending moment distribution were obtained. The lateral capacity and failure mode of the piles were determined from existing methods and analysis of the field test results. The lateral capacities of the piles were estimated using the Broms method without considering the effects of the thread. The estimated and measured lateral capacities were in a good agreement. This suggested that the effects of the threads on the lateral capacities were minimal. In addition, the effects of the tapered segments on the lateral response of the piles were negligible. This research was the first one for screw micropiles subjected to lateral loading and the outcome may support the engineering of the piles and further studies on soil-screw micropile interaction. [ABSTRACT FROM AUTHOR]

Nonplanar reinforced concrete (RC) core walls form the backbone of millions of mid- and high-rise buildings, resisting both gravity and lateral loads from wind and earthquakes. The latter inevitably induces torsional demands, even in the case of full plan-wise symmetric structures, which add to bending, shear, and axial deformations. Unfortunately, current international building codes are not applicable for the design of nonplanar sections governed by warping torsion rather than circulatory torsion. This lack of information and guidance in building codes has resulted in a very limited number of structures being designed to account for warping stresses, even though the latter can be of a similar order of magnitude to bending stresses and, therefore, of major significance. A simple procedure is herein presented to estimate the ultimate warping moment and ultimate torque of nonplanar RC sections based on "warping-equivalent" ultimate bending moments from sectional analysis. A circular and bilinear bending moment-torque interaction relationship is proposed and compared to the existing, albeit limited, experimental and numerical results available in the literature. [ABSTRACT FROM AUTHOR]

Axial forces are generated in the plates of ADAS-yielding dampers when subjected to lateral loading due to their boundary conditions. This on one hand can lead to an increase in strain level of the plates and accelerate the damage process, while on the other hand, the interaction of the bending moment with the tensile axial force leads to increasing strength, which is undesirable in the performance of ductile members. In this paper, a modified ADAS device (MADAS) is introduced to prevent undesirable interaction of axial forces, and its cyclic behavior is evaluated both experimentally and numerically. To this end, in the first step, two test specimens with different number of connection pins were prepared and subjected to cyclic loading in a rigid frame. Experimental and numerical results have shown that due to the removal of the constraint in the vertical direction, the level of forces produced by the damper is almost constant and the X-shaped plates have been able to tolerate significant number of cycles before crack initiation. Afterwards, the cyclic performance of ADAS and MADAS dampers was numerically compared individually and also when placed in the frame. Furthermore, in the frame equipped with ADAS damper, the increase in the level of forces produced by the damper led to the buckling of the braces, while the level of generated forces was totally in the expected range in the frame equipped with MADAS damper. [ABSTRACT FROM AUTHOR]

Monopile foundations are extensively utilized in the rapidly expanding offshore wind power industry, and the stability of these foundations has become a crucial factor for ensuring the safety of offshore wind power projects. Such foundations are subjected to a myriad of complex environmental loads during their operational lifespan. Whilst current research predominantly concentrates on the effects of wind, wave, and current loads on monopile stability in extreme environments, it is imperative to consider the potential influence of unexpected submarine landslide loads. In this study, we provide a comprehensive overview of wind, wave, current, and submarine landslide loads on monopile foundations in extreme environments. Subsequently, we establish a finite element model for analyzing the stability of monopiles under complex lateral loads, and validate the accuracy of the model by comparing it with the previous numerical findings. A case study is performed with reference to the Xiangshui Wind Farm project to analyze the effects of varying submarine landslide densities, velocities, impact heights, and seabed sediment strengths on pile head horizontal displacement, pile rotation at the mudline, and maximum bending moment. The findings indicate that the increase in submarine landslide density, velocity, and impact height leads to an increase in horizontal displacement at the pile head, pile rotation at the mudline, and maximum bending moments, and a horizontal failure mode is observed in seabed sediments. Furthermore, under the same load conditions, a decrease in seabed sediment strength and internal friction angle triggers instability in monopiles, with a noteworthy transition from horizontal failure to deep-seated seabed sediment failure. Finally, we propose a criterion for monopile instability under diverse loading conditions. [ABSTRACT FROM AUTHOR]

The hydrocarbon transportation industry uses extensive pipeline networks subject to complex loading conditions. The finite element analysis (FEA) has proven to be effective in simulating the deformation behavior in these pipelines, which assists in the assessment of their integrity and risks. In this work, a model developed using finite elements is proposed to analyze the behavior of API 5L Gr B carbon steel pipes, subject to internal pressure and lateral loads. The model is validated through uniaxial tensile and four-point bending tests. In addition, parametric analysis is carried out considering variables such as diameter, lateral load, and distance between supports. The objective is to identify which one of these variables has the most influence in the unit strain. The results indicate that the unit strain obtained from the numerical model agrees with the experimental tests. Furthermore, it is concluded that the diameter is the influential parameter. [ABSTRACT FROM AUTHOR]

Copyright of DYNA - Ingeniería e Industria is the property of Publicaciones Dyna SL and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Seismic design of prestressed concrete piles requires transverse spiral reinforcement to be proportioned to confine and thus retain an intact concrete core during inelastic rotation cycles. Prescriptive provisions of the International Building Code require a prescriptive minimum volumetric ratio of confinement reinforcement relative to the pile cross section and a minimum in-ground depth to which the confinement reinforcement must extend. This study seeks to determine a practical maximum depth to maximum in-ground bending moment for 12, 14, and 16 in. (300, 360, and 410 mm) prestressed concrete piles subjected to displacement consistent with lateral seismic loads. A commercially available lateral analysis software was used to conduct a parametric analytical study of square and octagonal piles embedded in substantially varied soil conditions. Piles were modeled to remain elastic. Depth to maximum in-ground moment was recorded. Maximum depth values for each pile type were reported. Analysis of results indicates that prescriptive depth requirements may be overly conservative for 12 and 14 in. square piles in nonliquefiable soils. It was concluded that a reduction could be made to the code-prescribed depth of ductile reinforcement for some pile types in nonliquefiable conditions. [ABSTRACT FROM AUTHOR]

Using a monopile foundation due to a reliable and simple technology has a wide application in engineering structures. This paper investigates numerically the performance of an offshore wind turbine with a monopile foundation equipped with a restriction plate at a middle inside height of the monopile under the wind, wave, and seismic loadings. Different parameters, including wind velocity, wave period, wave height, soil characteristics, and combination of loadings, are considered in nonlinear finite element dynamic analyses. Results are given in terms of the distribution of displacement and bending moment over the turbine height and frequencies. The results reveal that by increasing the wind velocity, the responses of the tower increase, and the wind load acting on the hub has the most important effect on the turbine behavior rather than the wind load acting on the tower body. Furthermore, the values of maximum displacement and bending moment under wind and wave loading decrease with the increase of the shear strength of the soil, whereas the responses of the tower under earthquake loading increase. Generally, it is necessary to consider the effect of a combination of wind, wave, and earthquake loadings on the design of the turbine tower. [ABSTRACT FROM AUTHOR]

Typical concentrically braced frames (CBFs), such as cross-braced (X-braced) frames, are commonly used to provide resistance against lateral loads. These systems are prone to buckling under compression, resulting in instability before reaching the yield strength. In other words, this bracing system exhibits an asymmetric behavior in tension and compression that undermines its energy dissipation capacity during excitation and leads to substantial damage to the structural and non-structural members. In an attempt to improve these shortcomings, this study introduces the novel quasi-X-braced frames. The stiffness and stability of the quasi-X-braced steel moment frames were evaluated by novel analytical and numerical methods. Drawing on strain energy concepts and Castigliano's theorem, this study presents an accurate analytical formulation for the lateral elastic stiffness of two-dimensional single-span and one-story quasi-X-braced steel moment frames (QXB-MFs). In this regard, all effective parameters, including the axial and shear loads and bending moments of all members, were taken into account. The proposed relation was validated with results from different cases using OpenSees. The error between the elastic stiffness results of the developed relation and the finite element numerical analysis was found to be negligible. Also, the seismic performance of QXB-MF systems was investigated according to the FEMA P695 methodology for near-field and far-field ground motion records compared with the intermediate moment frame. The results showed that using quasi-X braces in the intermediate moment frame improves the seismic performance of this system. [ABSTRACT FROM AUTHOR]

Pile-soil interaction is one of the most critical factors in evaluating foundations' static and seismic responses. During an earthquake, piles can become subject to stress caused by the surrounding soil and structure movement. To design a suitable seismic pile foundation, in addition to considering the effect of the structure on the pile (inertial interaction), the impact of the soil that applies to the pile (kinematic interaction) must be considered. Therefore, dynamic analysis of piles simultaneously exposed to both vertical and horizontal loads is one of the most essential subjects in geotechnical engineering. The present study evaluated various approaches proposed in the literature to determine the inertial and kinematic loads applied to the pile. Also, based on the results of the centrifuge test, the best method that could correctly predict the combined effect of these two loads on the pile response was presented. The results indicated that precise determination of the maximum lateral force exerted on the pile-soil-superstructure system plays a crucial role in the reliability of the theoretical methods employed to calculate the maximum bending moment of the pile. Also, if the appropriate theoretical approach is used, the accuracy can be similar to the 3D finite element analysis results. [ABSTRACT FROM AUTHOR]

Pile foundations near the crest of a slope are often required to resist lateral loads. In the present study, the effect of slope inclination and edge distance from crest of clayey slope on ultimate lateral pile capacity has been investigated using PLAXIS 3D. From the obtained results, the hyperbolic p-y relationship has been established for different edge distances. For the case of pile located at crest, the increase of slope inclination from 0° to 30°, the ultimate lateral pile capacity decreased by 14.5 and 16.9% for undrained cohesion of 50 and 100 kPa, respectively. For the slope angle 30°, increase in the crest distance from 0 to 7 times pile diameter resulted increment in the ultimate lateral pile capacity by 16.7 and 20.4% for undrained cohesion of 50 and 100 kPa, respectively. The maximum normalized bending moment increased with increase in the ground slope angle. Marginal reduction in the maximum normalized bending moment has been noticed with increase in the edge distance. [ABSTRACT FROM AUTHOR]

A counterfort–relief shelf composite retaining wall is capable of reducing lateral earth pressure. With its relief shelf and T-shape variable section beam as tension member, this wall is effective for high fill slope engineering; however, research on this type of retaining wall is limited. Moreover, investigating the lateral earth pressure distribution law and the mechanical and deformation characteristics of this composite structure is necessary. In this study, three models (a counterfort structure, structure with short relief shelves, and structure with long relief shelves) were tested. Moreover, lateral earth pressure, bending stress, and structural displacement were measured. The measurements revealed that the lateral earth pressure, bending stress in the buttress, and displacement of composite structures were less than those of the counterfort retaining wall under the same conditions. The present study reveals that relief shelves can reduce the total lateral force, maximum bending moment, and maximum displacement at the top of the structure by 33%, 30%, and 33%, respectively, compared with those of the counterfort wall. The lateral earth pressure acting on the structure with long relief shelves is significantly lower than that on the structure with short relief shelves. However, in terms of bending stress and displacement, the difference is not evident. The lateral earth pressure under each relief shelf starts from zero and follows a certain distribution law. Although the relief shelf can reduce the magnitude of lateral earth pressure, it raises the point of application of the total lateral force. Thus, the length and position of the relief shelf are important governing factors of the bending moment of a composite structure. Due to variations in the bending moments derived from the tests, theoretical lateral earth pressures, and calculated bending stresses in the buttress, this study hypothesizes that a certain force is exerted on the lower part of the unloading zone, thus requiring further research. The displacement curve of the composite retaining wall is similar to that of the counterfort retaining wall; it conforms to the bending deformation of the cantilever beam. [ABSTRACT FROM AUTHOR]

The pile-supported wharf (PSW) is one of the most common structures in harbor engineering. To investigate the dynamic response characteristics of the PSW, a quasi-static model test of a PSW–ground system under cyclic lateral loading is conducted. The deformation and damage processes of piles and the sand stratum are observed and obtained. The hysteresis characteristics of the PSW–ground system and the response characteristics of piles are systematically explored. The strain energy of the pile group on the sloping ground is calculated and analyzed. The results show that there are two peak bending moments on the pile, and the maximum one occurs at the pile top. The pile embedded depth and the loading direction strongly affect the strain energy distribution of the pile group. Under downslope direction loading, the center piles have the largest strain energy percentage. The strain energy extends from the center piles to the outside piles with the increase in loading displacement amplitude. The test results indicate that the landside pile and center pile should be strengthened during seismic design. [ABSTRACT FROM AUTHOR]

The m-method is a commonly used method to calculate the internal force and deformation of pile foundations under lateral loads. However, for squeezed branch piles, the increase in the load-bearing plate leads to changes in the pile section and the generation of a resistance bending moment under loading, which means the load–displacement relationship at the load-bearing plate will no longer satisfy the linear relationship. In this paper, a hyperbolic load transfer model is established to describe the nonlinear relationship between the soil resistance and lateral displacement at the branch of the pile, and the m-method is used for the straight section of the pile. Laboratory model tests are used to verify the correlation between theory and experimentation. The results show that the theory is consistent with the measured curve. On the basis of the theoretical calculation, the influence of the bearing plate and pile body parameters on the force of the squeezed branch pile is analyzed. The research shows that that the bearing capacity of the squeezed branch pile is improved by increasing the plate's diameter, placing the plate closer to the ground, and ensuring that the pile top is embedded. The theoretical calculation method established in this paper can correctly and accurately reflect the bearing capacity characteristics of squeezed branch piles under horizontal loads, and it is more safe than performing measurements. Additionally, it can be applied to squeezed branch piles with different plate diameters, plate positions, plate section forms, and plate quantities as well as for piles with different boundary conditions and soil conditions. Moreover, it can also be applied to other pile shapes. This method is of significance for the analysis of the bearing characteristics of piles with variable sections under lateral loads. [ABSTRACT FROM AUTHOR]

A new practical formulation of the load-transfer P-Y curves to analyze the load–deflection response of a single pile under lateral loads is proposed in this paper. Parameters of the P-Y curves, namely the lateral reaction modulus and the lateral soil resistance, were correlated to the pre-bored pressuremeter (PMT) data as well as to the pile/soil stiffness ratio. A total of 16 full-scale monotonic lateral loading tests carried out in six experimental sites in France, representing a variety of soil conditions, were interpreted focused on the construction of the experimental P-Y curves along the test pile. For practical purposes, a methodology of construction of the P-Y curves was proposed. Moreover, the paper highlights the new concept of the critical deflection, which is the threshold of the nonlinear pile/soil response, as well as a classification of piles based on the pile/soil stiffness ratio. The process of validation of the proposed P-Y curve-based method was undertaken by comparing the predicted load–deflection curves to the experimental curves of several test piles within a medium-sized database, and a very good predictive capability was noticed. At last, the concept of the normalized load–deflection curve was introduced to estimate the pile deflection during a preliminary stage of pile design. [ABSTRACT FROM AUTHOR]

Helical piles are a new type of pile that has good application prospects, and researchers have carried out an in-depth investigation into their vertical uplift and compressive bearing capacity. However, there is relatively little research on the dynamic bearing characteristics of helical piles. Therefore, the lateral vibration of a helical pile embedded in the viscoelastic foundation is systematically studied in this article. Utilizing the equivalent stiffness method to transform a helical pile into a cylindrical pile of special diameter, the lateral vibration model of the helical pile considering shear deformation is established based on the Winkler foundation model and the Timoshenko beam theory. The analytical solutions for the lateral dynamic displacement, bending moment, and shear force of the helical pile are strictly derived, and the rationality of the present solutions is also verified by comparing them with existing solutions. Based on the present solutions, a parametric study is carried out to investigate the influence of the pile and soil properties on the lateral dynamic response of the helical pile. It is found that the load excitation frequency and pile–soil stiffness ratio have a significant influence on the lateral dynamic displacement, bending moment, and shear force of the helical pile with space and time response. [ABSTRACT FROM AUTHOR]

Euler beam theory is always used for soil–pile analysis; however, its use is questionable for laterally loaded large-diameter monopiles. In this paper, the solution on the static impedances of monopiles under a combination of axial and horizontal loads was proposed based on three-dimensional continuous medium theory and Timoshenko beam theory. From the analysis results, the use of the Euler–Bernoulli beam theory leads to larger pile-head impedances, and the feature is more significant with lower aspect ratios and stronger pile-bottom constraints. The difference in the impedance from two theories may be up to 10%–43%. Consequently, Timoshenko beam theory is more appropriate for large-diameter monopiles, especially for monopiles with strong bottom constraints (such as rock-socketed monopiles). Meanwhile, the shear force and bending moment at the pile bottom have a considerable effect on the static impedances of large-diameter short monopiles, and only a consideration of the impedance contribution from the soil around the pile is insufficient. Furthermore, both the deflection and the bending moment of the pile increase due to the second-order effect of axial force, but the effect of the axial force on the impedance can be neglected for practical monopile designs. A simple and efficient approach to evaluate the impedance of large-diameter monopiles is desirable for designers, thus a simplified empirical equation for the pile-head static impedance was proposed for ease in calculating each component of static impedances for the large-diameter monopiles of offshore wind turbines (OWTs). [ABSTRACT FROM AUTHOR]

Thermally induced ratcheting of a thermo-active pile is the accumulation of net and irreversible pile head displacement upon heating–cooling cycles. Although this kind of phenomenon has been observed in vertically loaded piles in sand, it is unknown whether this exists in laterally loaded cases, and also what underlying mechanisms occur under the thermomechanical flexural soil–pile interaction. This study presents a series of centrifuge tests and finite-element simulations of the thermomechanical behaviour of a laterally loaded thermo-active pile in sand. A new model reinforced concrete (RC) was used in the centrifuge tests to mimic the thermal and mechanical properties of a prototype RC pile realistically. Ratcheting was evident in laterally loaded piles and its extent was more significant when the working horizontal load was higher. The ratcheting phenomenon was attributed to the accumulation of soil plastic strain due to the cyclic mechanical loading induced by pile thermal horizontal expansion and contraction, soil dilation upon soil–pile interface shearing and creep. The additional bending moment induced by the thermal action did not induce yielding within the pile. A subsequent numerical sensitivity study suggested that ignoring the softening behaviour of the sand would lead to underestimation of the magnitude of the accumulative thermally induced pile head lateral displacement. [ABSTRACT FROM AUTHOR]

Monopiles are the favored foundation type for offshore wind turbines due to a relatively simple design and installation process. This paper investigates using coupled three-dimensional finite-element analysis the load-deformation behavior of extra-large (XL) and extra-extra-large (XXL) monopiles in low-shear strength overconsolidated kaolin clay subjected to monotonic lateral loading at varying load eccentricities. The subloading tij constitutive model, robustly calibrated using data from centrifuge tests carried out by the authors, has been adopted in these analyses. For the 16 cases analyzed, a detailed discussion is provided on the behavior of XL/XXL monopiles, including their mode of deformation, lateral capacity, deflection, rotational stiffness, bending moment and shear force, and the response of the clay in terms of soil resistance and excess pore pressure. It is also demonstrated that the p-y method is inaccurate in designing monopiles in this size range. [ABSTRACT FROM AUTHOR]

For the consideration of required elevation, pile shafts are partially buried in the soil stratum and partially exposed above the ground surface, known as high-rise pile group (HRPG). The HRPG is extensively used in the construction of infrastructures and is usually adjacent the slope. It is frequently subjected to high lateral loads from the superstructure, leading to considerable displacement and bending moment. To alleviate the deformation and internal force of HRPG, a batter pile is employed, forming the high-rise batter pile group (HRBPG). A numerical simulation is conducted to observe the response of HRPG foundation subjected to downwards lateral load adjacent slope. The effects of slope angle, cap elevation, and lateral loading magnitude are determined. Results of HRBPG are compared with traditional high-rise vertical pile group (HRVPG). Conclusions can be drawn as follows. (1) The slope has significant effect on the displacement and bending moment of HRPG, so it should be considered in the design process. The displacement and bending moment of pile shaft increase gradually with the slope angle (0°–30°) and then they have a sharp growth (45°–60°). (2) With the rise of cap elevation, the displacement increases dramatically, whereas the bending moment rises and then falls. The displacement is highly sensitive under lateral loading with a high cap elevation; the higher the elevation is, the greater the displacement will be. Special attention should be paid when a high pile cap is adopted under large lateral loading. The displacement and bending moment of HRBPG are considerably smaller than those of HRVPG at a high pile cap elevation. (3) The displacement and bending moment are relatively small when a diminutive lateral loading is performed; however, they have a sharp growth under large lateral loading. The larger the load is, the greater the bending moment and displacement will be. (4) The displacement of the leading pile is slightly larger than that of the trailing pile, whereas the bending moment of the rear pile is larger than that of the leading pile. The pile shaft displacement above the ground surface is considerably larger than that below. The maximum bending moment occurs at the pile head, and the pile toe has minuscule bending moment. (5) The use of batter pile is beneficial for reducing the displacement and bending moment, whereas the slope and lateral loading are detrimental. [ABSTRACT FROM AUTHOR]

A systematic study into the behavior of reinforced semi-rigid piles in response to lateral monotonic and cyclic loading in clay was performed with centrifuge modeling tests (100×g). The aim was to investigate the pile–soil interaction mechanism of reinforced semi-rigid piles and to give some generally applicable design advice for reinforcing semi-rigid piles with cement-improved soil. For monotonic loading, the overall load–deflection behavior, profile of bending moment, net soil pressure and pile deflection have been fully studied, in addition to the p–y curves and excess pore pressure response of reinforced and unreinforced piles. It is found that shallow cement-improved soil reinforcement can greatly improve the lateral capacity of piles. In addition, a hyperbolic tangent model was proposed to fit the p–y curves obtained from monotonic tests for reinforced and unreinforced piles. For cyclic loading, it was found that compared with unreinforced piles, reinforced semi-rigid piles reduce the accumulation of pile deflection and the degradation of stiffness. The trends of the cyclic bending moment and cyclic p–y curves are also revealed. A series of supplementary finite element analyses were conducted to study the effects of reinforcement parameters (reinforced width, reinforced depth and strength of cement-improved soil) on lateral pile capacity. It is suggested that shallow reinforcement with a reinforced width of 5D and a reinforced depth above the rotation point of a semi-rigid pile is both economical and practical. [ABSTRACT FROM AUTHOR]

In this study, the monotonic and cyclic behavior of an offshore wind turbine with a monopile foundation installed in a sand layer were evaluated in the centrifuge. A simplified offshore wind turbine was modeled, and the lateral load was applied to the tower under displacement control. The monotonic loading test evaluated ultimate lateral load capacity and bending moment profiles under different loading levels. During cyclic loading, variations of moment-rotation responses, cyclic stiffness, and bending moments along the pile were observed. The initial rotational stiffness of the monopile decreased as the loading level increased. In the fatigue limit state (FLS) and service limit state (SLS) loading conditions, no noticeable variation in stiffness was observed with the number of cycles. However, in the ultimate limit state (ULS), the stiffness of the monopile increased during the first few cycles, followed by a decreasing rate of increase, and reached a certain value. The loading rate had a weakening effect on the monopile–soil interaction, which was supported by the bending moments induced in the monopile. [ABSTRACT FROM AUTHOR]

Structural engineers should appropriately design concrete structures to resist lateral loads. Determining the adequate system for resisting the expected lateral loads is important to control the building drift. Choosing the appropriate system is usually conducted assuming the predicted forces are applied to completed concrete buildings at one step which is commonly known as ordinary analysis (OA). Nevertheless, these structures are constructed sequentially which requires using staged analysis (SA) instead of OA. In this paper, a comprehensive numerical model for SA of concrete buildings, which accounts for time dependent effects, is utilized using a well-validated commercial software. Six reinforced concrete buildings with 10 and 20 storeys are analyzed using the developed model. Three various structural systems are considered (Rigid Frame (RF), Shear Wall (SW), and Wall Frame (WF). A comparison is conducted between the displacements and internal forces in beams and slabs obtained from the SA and OA. For a 10-storeys RF building, maximum bending moment from SA is 29.9% higher than that from OA. The same conclusion was observed for the maximum shearing force with a percentage of 19.6%. Moreover, maximum bending moments and shearing forces from SA for the 20-storeys RF building are, respectively, 35.0% and 23.5% larger than those from OA. The RF and WF systems provided the minimum difference in differential displacement between the OA and SA analyses. The RF system produced the least differences in internal forces from OA and SA for all studied buildings. [ABSTRACT FROM AUTHOR]

The response characteristics of large-diameter monopiles under lateral loads obviously differ from those of traditional small-diameter piles. To investigate the failure mechanism and soil resistance of laterally-loaded large-diameter monopiles, a series of finite element analyses of monopiles in soft clay were conducted. From the analysis results, an additional rotational soil flow can be observed in the large-diameter soil-monopile system, but there is only a slight difference (approximately 2–6%) in the bearing capacity of monopiles when the p–y method is utilized with and without rotational soil flow. Consequently, the consideration of the wedge-full-flow mechanism is sufficiently accurate for the monopile design of offshore wind turbines. Moreover, the base shear force and bending moment have an important influence on the lateral behaviour of large-diameter monopiles, and ignoring these additional base resistance components can greatly underestimate (even up to − 30%) the lateral bearing capability and lateral stiffness of semi-rigid and rigid large-diameter monopiles. Modal analysis of the 5 MW wind turbine also shows that this ignorance can lead to an underestimation (nearly 13.0%) of the structure's natural frequency. To consider the contributions of the additional base resistances to the lateral stiffness and bearing capacity, we developed two new T–u and M–φ springs to expand the current p–y method. [ABSTRACT FROM AUTHOR]

The p–y method as a simplified analysis tool has been widely used to analyze the behavior of laterally loaded piles. This paper develops a novel cyclic p–y elastoplastic model within the framework of the single-surface bounding surface theory. The model can capture the soil stiffness degradation during cyclic loading by incorporating the cumulative plastic displacement to an interpolation function of the elastoplastic resistance coefficient. The model is relatively simple with only four parameters that can be determined from standard soil properties and stress–strain responses measured in direct simple shear tests. The performance of developed model is validated by predicting the cyclic lateral response of piles installed in soft clay during field and centrifuge tests published in the literature. The model can reliably simulate monotonic and cyclic responses of piles under different lateral loading patterns, and capture main characteristics of the pile-head load–displacement curve, such as nonlinearity, hysteresis, displacement accumulation, and stiffness degradation. It can also predict the evolution of the lateral deflection and sectional bending moment along the pile during cyclic loading. [ABSTRACT FROM AUTHOR]

In this study, a series of centrifuge tests are performed to investigate the ultimate lateral capacity of a pile group for offshore wind turbines. The validated Finite element models (FEMs) are established. The rotation center and the maximum bending moment occur at 9 D and 3 D of the pile length. A sensitivity study is performed by considering the soil parameters through numerical tests. The internal friction angle is the most influential factor by introducing 32% change in lateral capacity. The key factors of pile number, pile diameter, loading height, and pile spacing are investigated in the following parametric study. Increasing the pile number and the pile diameter is effective for enhancing the lateral capacity. In contrast, a larger eccentricity has a negative effect on the foundation stability. The failure mode of the pile group foundation tends to change from strain softening to strain hardening when the loading height reaches a threshold magnitude. The p-multiplier is calculated to demonstrate the shadowing effect in a pile group foundation. An optimal design method is proposed by integrating the pile number and the pile spacing factors. This study provides some instructions for the application of pile group foundations in the offshore wind industry. [ABSTRACT FROM AUTHOR]

Wind turbines' participation in frequency response is known to improve the frequency stability of power systems, but it can also have a negative impact on the fatigue load of wind turbines. The objective of this paper is to investigate the effect of frequency response on the fatigue loads experienced by various components of a wind turbine, including the low-speed shaft, tower, and blade. To achieve this goal, the authors develop a model of a variable speed horizontal-axis wind turbine based on a doubly fed induction generator. They derive explicit analytical equations of low-speed shaft torque, tower bending moment, and blade bending moment to describe the fluctuations of torque and moment related to the operating states of wind turbines, such as generator torque, rotor speed, and pitch angle, under frequency response. These equations allow for the evaluation of the impact of frequency response on torque and moment changes and fatigue load. Spectral density analysis and modal analysis are used to further analyze the analytical equations, examining the influence of frequency response on different operating conditions of wind turbines and determining the mechanism by which frequency response affects fatigue load qualitatively and quantitatively. The authors use the FAST V8 Code based on the NREL offshore 5-MW baseline wind turbine to demonstrate the effectiveness of the proposed analysis method in evaluating fatigue loads affected by frequency response. The results show that the fatigue load on the low-speed shaft and the lateral side of the tower will significantly increase due to wind turbine participation in frequency response. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This study aims to investigate the response of flexible piles in the course of cyclic and post-cyclic lateral loadings for different loading scenarios including cyclic loading pattern, loading frequency, and also amplitude. For this purpose, an experimental program has been organized and a series of tests were conducted on a model pile embedded in dry sand. Experimental p–y curves derived from bending moment profiles for different loading patterns, namely symmetric two-way, asymmetric two-way, full one-way, and one-way patterns without complete unloading were studied. The results indicate that the stiffness is highly dependent on the cyclic loading pattern, and the two-way cyclic loading was found to increase the lateral force and soil stiffness more than any other factor. Also, compared to the monotonic loading, the residual force induced by one-way loading and one-way loading without complete unloading causes the lateral bearing capacity to decrease significantly. In addition, the post-cyclic load–displacement response of the pile was found to be influenced by the number of cycles, loading amplitude, and soil density index. Finally, a comparative study revealed that predictions made by the API code for the lateral resistance of flexible piles embedded in dry sand underestimate the p–y curves obtained from experimental observation. [ABSTRACT FROM AUTHOR]

In this research, body technology was established for side collisions with new IIHS MDB as a representative case. In the conventional body structure, most of the load received from the barrier is absorbed by bending deformation of the door beam and B-pillar, etc. For that reason, the body is subjected to large deformation before reaching the maximum load, and the deformation increases further when subjected to a high-energy collision. Therefore, the objective of this research is to create a structure that increases the load from the initiation of impact and suppresses the deformation of the car body. An arched door beam was developed to reduce the bending moment by the axial load in the longitudinal direction generated during the deformation and to increase the load in the lateral direction. A principle equation was developed that uses the shape of the door beam as a variable. A prototype of the arched door beam was fabricated, and its performance was evaluated by an impactor test. A full-car simulation was conducted using a mass-produced sedan as a base, to which the arched door beam was added to verify the performance of the complete vehicle. The results of the impactor tests were evaluated using the load gradient, which was defined as the generated load divided by the amount of deformation. Compared to conventional straight door beams, the load gradient was 7.1 times higher. Full-car simulation results showed that for a gasoline-powered vehicle body weight, the body load gradient of the proposed structure was 4.7 times higher, and the body deformation adjacent to the dummy shoulder was reduced by 210 mm. Spine acceleration of the dummy was reduced by 56%. The body structure proposed in this research has the effect of increasing the load gradient and reducing body deformation and spine acceleration. It is expected to be applicable to EVs and FCVs, which require more energy absorption due to their increased vehicle weight. [ABSTRACT FROM AUTHOR]

Due to the complexity of pile–soil interaction, there is little research on active–passive piles that bear the pile-top load transmitted from the superstructure and the pile shaft load caused by the lateral soil movement around the pile simultaneously. The purpose of this study is to analyze the displacement and internal force of active–passive piles. Most of the pile design codes in China use the elastic resistance method to describe the relationship between the lateral soil resistance and the horizontal displacement of the pile, but this is not accurate enough to analyze the internal force and deformation of the pile when the pile displacement is large. For this case, the passive load on the pile shaft caused by the adjacent surcharge load can be described in stages, and the p–y curve method can be used to express the relationship between the lateral soil resistance and the horizontal displacement of the pile. Additionally, taking both the active load (vertical force, horizontal force, and bending moment on the pile top) and the passive load into account, the deflection differential equation of the pile shaft is herein established, and a corresponding finite difference method program is implemented to obtain the calculations pursuant to the equation. The correctness of the analysis method and program was verified by two test cases. The results show that our calculation method can effectively judge the flow state of the soil around piles and accurately reflect the nonlinear characteristics of pile-soil interaction. Moreover, the influence depth of the pile displacement under the passive pile condition caused by the adjacent load is significantly greater than that under active pile condition, and the maximum pile-bending moment appears near the interface of soft and hard soil layer. [ABSTRACT FROM AUTHOR]

The driving of pile into the ground is one of the important tasks of construction works and especially for new buildings in big city. Difficulties in driving piles for new construction will adversely affect the foundations of neighboring and adjacent building. This research proposes a measure to assess the state of conduct of the pile driving process using a nonlinear Finite Element Method (FEM). Manuscript using Plaxis 3D Foundation analysis software for an existing building with reinforced concrete pile foundation with foundation tower size 2.0 m x 2.0 m on 4 piles with a cross-section of 0.3 m x 0.3 m, length 10.0 m; foundation bearing a load of 1000 kN. Then press the reinforced concrete pile size 0.3 m x 0.3 m, pile length 10.0 m, pressing position 0.5 m from the edge of the existing foundation, pressure 500 kN. The results of the analysis showed the effect of the adjacent pile process to the stress and strain of the neighboring building foundation in cramped land for construction conditions. In order to provide solutions to overcome difficulties for the adjacent building be effective. The effective stress in the existing reinforced concrete pile foundation without adjacent is -273.7 kN/m², but when it is interlocked, it is -3490.0 kN/m². After pressing the piles, the horizontal displacement of the existing piles is 10.2 mm and a bending moment of 48.6 kNm occurs. [ABSTRACT FROM AUTHOR]

Monopiles are the most common foundation form of offshore wind turbines, which bear the vertical load, lateral load and bending moment. It remains uncertain whether the applied vertical load increases the lateral deflection of the pile. This paper investigated the influence of vertical load on the behaviour of monopiles installed in the sand under combined load using three-dimensional numerical methods. The commercial software PLAXIS was used for simulations in this paper. Monopiles were modelled as a structure incorporating linear elastic material behaviour and soil was modelled using the Hardening-Soil (HS) constitutive model. The monopiles under vertical load, lateral load and combined vertical and lateral loads were respectively studied taking into account the sequence of load application and pile slenderness ratio (L/D; L and D are the length and diameter of the pile). Results suggest that the sequence of load application plays a major role in how vertical load affects the deflection behaviour of the pile. Specifically, when L/D ratios obtained by lengthening the pile while keeping its diameter constant are 3, 5 and 8, the relationships between lateral load and the deflection behaviour of the pile under the effect of vertical load demonstrate a similar trend. Furthermore, the cause of increased lateral capacity of the pile under the action of applied vertical load in the common practical application case and in the VPL case was analyzed by studying the variation law of soil stress along the pile embedment. Results confirm that the confining effect of vertical load increases means effective stress of the soil around the pile, thus increasing soil stiffness and pile capacity. [ABSTRACT FROM AUTHOR]

It is necessary to understand the response of monopile foundations for large offshore wind turbines (OWTs) with rated powers of 6 − 9 M W under cyclic loading. For this purpose, a monopile model test study was conducted in saturated medium dense sand under long-term unidirectional lateral sinusoidal cyclic loading for 12 , 000 cycles. The model pile was constructed with displacement transducers on the pile head and strain gauges along the pile length. The experimentally obtained bending moment, displacement, soil reaction evaluation along the pile length, pile head displacement accumulation, and lateral soil-pile stiffness were substantially different from the results of the American Petroleum Institute (API)-recommended method of determination and were significantly affected by the number of loading cycles. The experimentally based soil reaction (p) -pile displacement (y) curves obtained considering the maximum soil reactions for particular cycles were compared with the p - y curves recommended by the API. The maximum soil reaction (p) during the increase in pile displacement (y) obtained experimentally was significantly higher than the soil reaction obtained with the API method. The p–y curves obtained experimentally show similarities with those determined with the API method at only small pile displacements in the initial stage of the curves. [ABSTRACT FROM AUTHOR]

Even if precast pre-stressed hollow-core (PPHC) slabs are usually designed as simply supported elements, continuity with the supporting beam may exist when constructed together with a reinforced concrete topping and continuity reinforcing bars. During an earthquake (and possibly other lateral load), this continuity may result in bending moments being induced close to the supports as the buildings sway laterally. The response of precast floors to earthquake-induced demands has been addressed by past research. However, further investigation is required to improve understanding of several aspects of precast floor behaviour either revealed or emphasized by recent earthquakes in New Zealand. This paper proposes a mechanics-based modelling approach for the analysis of PPHC slab-to-beam seating connections. The model has been calibrated against existing test data to predict the failure of a PPHC slab under negative bending moments. The numerical outcomes allow comparison of the moment–drift response, principal tensile stresses, and crack progression during loading. The developed modelling approach will allow future studies to exhaustively investigate all aspects of precast floor behaviour by varying the properties and geometry of the PPHC seating connection. [ABSTRACT FROM AUTHOR]

This paper investigated and compared the dynamic responses of driven and helical piles in cohesive soil using finite element analysis. The finite element models were calibrated based on large-scale field dynamic tests on single steel piles driven into a soft clay layer and embedded in a gravelly sand layer. The soft clay was improved using the cement deep soil mixing technique. The calculated results from the numerical models were in good agreement with the measured response in the field tests. The numerical models were then employed to investigate the dynamic response of helical piles in clay. Driven steel piles and single- and double-helix piles were subjected to lateral dynamic loads, and their responses were compared. The results demonstrated that the helical pile exhibited excellent lateral and axial responses, comparable to that of the driven piles. The lateral displacement of the helical piles was similar to or less than that of longer driven piles depending on the clay strength, number, and spacing of the helices. In addition, the double-helix pile with an inter-helix spacing of 3 times the helix diameter reduced the required width of soil treatment to 7.5 times the pile diameter while achieving the same performance as a driven pile with a treated area 12 times the pile diameter. The kinematic and inertial interaction effects were evaluated for helical piles. It was found that the kinematic interaction forces increased the bending moment at the interface of different layers, while the inertial forces increased the bending moment at the ground level. Finally, the helical pile exhibited lower lateral deformations than the driven pile during the seismic motion, and the maximum bending moment was relatively lower. [ABSTRACT FROM AUTHOR]

Pile foundations supporting major structures are often founded in soft compressible clays. Apart from usual super-structural loading, these piles are subjected to cyclic lateral loads originating from actions of waves, ship impacts, winds or moving vehicles. Such repetitive loading induces stress reversal in adjacent soft clay initiating progressive degradation in soil strength and stiffness. This not only deteriorates the pile capacity with unacceptable displacements, the bending moments also increase. Although past studies investigated the response of single pile under lateral cyclic loading, a detailed study on pile group in clay under cyclic lateral loading with emphasis on bending moment is of immense practical interest. This paper focuses on detailed study of the response of pile group in clay under cyclic lateral loading, with emphasis on bending moment, through numerical modelling via a three-dimensional dynamic finite element (FE) approach and simplified boundary element modelling (BEM). Comparisons of computed results with available test data imply that the results obtained by 3 D dynamic FE model are better than the BEM. Extensive parametric studies with field data indicate that pile bending moment has been significantly influenced by cyclic loading parameters (number of cycles, frequency and amplitude). Relevant conclusions are drawn from the entire study. [ABSTRACT FROM AUTHOR]

With the rapid development of domestic mining industry, it is necessary to consider the safety of the mine when mining. In order to improve the high stress environment and the frequent failure of bolts caused by the increase of excavation depth, in this experiment, FLAC 3D is creatively proposed to establish the calculation model of bolt support roadway, analyze the basic geological environment and surrounding rock structure of the research area, and conduct the numerical simulation of the mechanical characteristics of bolt support deformation (BSD) in the high stress roadway (HSR). The basic geological environment and surrounding rock structure of the study area are analyzed, and FLAC 3D is adopted for establishing a calculation model of the bolt-supported roadway, which can be used to simulate the axial and lateral forces of the bolt, and then determine the boundary conditions. It is found that the supporting bolt in the roadway needs to bear not only axial tension, but also transverse shear and bending. Based on the Winkler foundation beam principle, a calculation model of the bolt's lateral bending force in the soft rock roadway is established, the lateral force characteristics of the bolt support are analyzed, the concept of "anchoring composite bearing body" is proposed, and the force characteristics of the bearing body are calculated. The research results show that in the HSR, the bolt mainly bears the combined forces of tensile and lateral bending; among them, the bolt's axial force remains basically unchanged at the tail part near the pallet, and the bolt's axial force at the end part deep into the rock mass decreases rapidly. The bending moment of the bolt is "wave-shaped" distributed along the length of the rod body in the positive direction and negative direction of the axis, and the comprehensive action of the axial tension and transverse bending of the bolt increases when the stress concentration increases. A smaller roadway radius will lead to longer bolts, denser arrangement and higher support strength. [ABSTRACT FROM AUTHOR]