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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]

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]

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]

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]

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]

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]

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]

The response of laterally loaded piles installed near the crest of clay slopes is analysed. Three-dimensional finite element analyses are presented for piles at various distances from a slope crest and for different pile shape. The results of these analyses are used to study the variation of the pile displacement, the bending moment of the pile and the soil resistance in relation to pile to slope distance and pile shape. The obtained results show that the proximity of slope significantly affects the lateral load capacity of the piles but not significantly when the piles are placed at 7D (where D is pile diameter) or greater from the slope crest. Furthermore, the lateral soil resistance on the ground surface for circular piles is larger than that for rectangular piles at the same lateral load in level ground. The decrease rate of lateral soil resistance on the ground surface for circular piles gets faster as the slope ratio and load level increase. [ABSTRACT FROM AUTHOR]

In this study, a Finite Element (FE) model of locally strengthened high-strength stainless-steel tube subjected to lateral impact loads is established using LS-DYNA to investigate its dynamic behaviours. The accuracy of the FE results is verified by comparing with the test results. The impact force, bending moment, stress and strain responses as well as the internal energy dissipation histories of the strengthened tube are analysed during the entire impact process. The results indicate that the impact resistance of the strengthened tube is obviously enhanced as compared to hollow stainless-steel tube. Furthermore, parametric studies are conducted to reveal the influence of axial compressive force, impact position, impact velocity and material strength on the impact behaviour of the strengthened tube. The results show that the application of axial compressive force reduced the impact force and increased the deformations of the strengthened tube. The impact resistance of the strengthened tube performed an increasing trend when moving the impact position towards the support and increasing the material strength. In addition, the increase of impact velocity significantly reduced the impact duration. Finally, design recommendations and process were proposed to facilitate the application of locally strengthened tube. • The impact response of locally strengthened stainless-steel tube was numerically studied. • The impact force, bending moment, stress and strain response and energy dissipation were analysed. • Concrete was found to dissipate more impact energy than the other parts. • The effects of variant parameters on impact performances of the strengthened tubes were investigated. [ABSTRACT FROM AUTHOR]

• The dynamic response of thin-walled cylindrical shells subjected to lateral shock loading via foam projectile impact was systematically studied. • Structural deformation evolution, deformation/failure modes, and mid-point deflections of thin-walled cylindrical shells under lateral shock loading were experimentally measured. • The sensitivity of the dynamic response of thin-walled cylindrical shells to the impact momentum level and geometric parameters under lateral shock loading was numerically explored. • It is found that the deformation on the rear side exhibits two patterns: indentation and bulge, which are dictated by the combined effect of circumferential membrane forces and bending moments. A combined experimental and numerical study was carried out to explore the dynamic response of Q235 thin-walled cylindrical shells under lateral shock loading. The machined Q235 specimens were clamped on both sides and subjected to centered lateral simulated shock loading via foam projectile impact tests, with their dynamic deformation evolution, mid-point deflections, and final deformation modes experimentally measured. The mid-point deflections of the impact side are all positive (the direction of deformation is the same as the impact direction) while those of the rear side all exhibit negative values (the direction of deformation is opposite to the impact direction). To further explore this phenomenon, the method of finite element (FE) was employed to simulate the foam projectile impact, with good agreement against experimental measurements achieved. Using the validated numerical model, the effects of impact velocity, length-to-diameter ratio, and thickness-to-diameter ratio on the dynamic response of the thin-walled cylindrical shell were further analyzed. The direction of both side deflections and deformation modes are significantly affected by the impact level and the shell geometries. For the rear side, within the given range of impact momentum and geometric parameters, the numerically predicted deflection varies from −1.775 mm to 2.45 mm. Thereupon, the coupling of indentation and bulge deformation patterns are indicated, and their corresponding contribution changes are considered the main mechanism for determining the final deformation of the thin-walled cylindrical shell's rear side. [ABSTRACT FROM AUTHOR]

This study aims to investigate the one-way cyclic lateral responses of piles in sloping ground by means of experimental and theoretical analyses. For this purpose, a series of laboratory model experiments were performed for different cases of cycle number, load amplitude, and slope angle, and lateral static loading tests on both level ground and sloping ground were conducted for comparison. Based on these experimental observations, the effects of cycle number, load amplitude, and slope angle on the pile head deflection and the profiles of bending moment and subgrade reaction are discussed. The pile deflection profile is difficult to measure directly owing to the restriction of experimental conditions, and thus a supplementary finite beam element method (FBEM) is provided to compensate for this deficiency. The comparisons between experimental and theoretical results demonstrate that the FBEM can well predict the pile responses in sloping ground, either under one-way cyclic lateral loading or lateral static loading. [ABSTRACT FROM AUTHOR]

Offshore wind energy development is driven by ongoing research and development to determine technological issues connected with offshore wind turbines. A fundamental design difficulty is the offshore wind turbine foundations. By far, one of the most commonly practiced foundation systems is mono helical pile foundations because of their simplicity and resilience. Most of the studies on mono helical piles were focused on granular soils and few studies were on clayey soils. However, mono helical piles in clayey soils under combined loading remain to be examined. Hence, a series of three-dimensional finite element analyses were carried out to predict the uplift and lateral capacity of the helical pile embedded in soft clay. The numerical model is verified using the results from the analytical results and a small-scale laboratory test. The verified model is used to simulate the helical pile behavior under the combined uplift and lateral loading condition considering the pile with a different number of helical plates. The results of the combined loading analyses reveal that the lateral capacity decreased when the pile was subjected to uplift load, and a maximum reduction of 12% is observed in mono helical piles provided with a single plate for an applied 50% of the ultimate uplift load. The influence of uplift load also increased the bending moment of the helical pile. Finally, it is suggested that the helical piles should be designed considering the aspects for combined loading conditions. [ABSTRACT FROM AUTHOR]

The single pile is a structural element that has an important role in supporting any part of the superstructure. This paper adopted three dimensional finite element modelling by using ANSYS to discover the influence of soil size domain on pile diameter, pile length, load eccentricity and torsion magnitude. One type of soil was used and described by Drucker-Prager model. The numerical analysis has been performed to show how the variation in soil size domain effects on the behaviour of single pile under torsion load. The procedure which is adopted in the investigation depends on fixing all variables and changing one variable to show the impact of this variable on the pile response considering soil domain variation. From the investigation, it is obvious that the pile diameter, eccentricity and torsion load have a major influence on the pile response, while the pile length has a minor influence on the pile response. Here, the increase in pile diameter reduces the load transfer to the soil; also the increase in eccentricity increases the load transfer to the soil while the increase in soil domain reduces the pile response. When the torsion load increases the pile response increases too. The pile response refers to displacement, rotation, shear force and bending moment. [ABSTRACT FROM AUTHOR]

• Perform three-point bending tests on high strength grouted tube-sleeve connection. • Investigate load transfer mechanism of grouted tube-sleeve connection. • Perform FE simulation of grouted tube-sleeve connection under lateral load. • Perform moment-shear interaction analysis of grouted tube-sleeve connection. Prefabricated prefinished volumetric construction divides traditional buildings into room-sized modules that are manufactured off-site and assembled on-site. This construction method offers improved construction speed, superior quality control, and reduced environmental impact compared to traditional construction. In high-rise modular construction, the connections between modules may experience significant bending moments due to wind loads or earthquakes. Therefore, the flexural performance of these connections becomes a critical factor that affects the overall stability and robustness of the modular structures. The present study combines the advantages of high strength grout and square hollow section tube sleeves to develop a robust grouted connection for prefabricated structures without compromising assembly efficiency. Firstly, the study conducts three-point bending tests on eight full-scale specimens to investigate the flexural behavior of the connection. The load transfer mechanism, failure modes, moment-curvature relationship, and strain development of the tube-sleeve connection under lateral load are analyzed in detail. The study also quantifies and discusses the effects of different shear key spacing, grout length, inner tube width, and steel fiber content on the strength and stiffness of the connection. In addition, the study utilizes ABAQUS to simulate the bending responses of the connection, including inner tube fracture, grout crack development, and internal complex strain state. The finite element analysis results demonstrate good agreement with the experimental results, with an average ratio of 1.04 between numerical results and test results for flexural resistance, and a standard deviation of 0.04. Furthermore, based on elasto-plastic mechanics and the actual cross-sectional stress distribution of the connection, three analytical models are proposed to predict the flexural resistance of the connection. Finally, the moment-shear interaction relation is verified against the finite element and test results using the elastic-plastic analytical model and the ultimate state shear model. [ABSTRACT FROM AUTHOR]

This study is concerned with evaluating the response of single pile subjected to cyclic horizontal uniaxial loading. Combination of lateral cyclic loading and constant vertical or lateral load in two-orthogonal directions is also studied. Moreover, the influence of one- and two-way loading, number of cycles and the intensity of constant load in conjunction with the cyclic lateral load is presented. The study is further continued by comparing the performance of long and short single pile embedded in clayey soil. A series of three-dimensional finite element models using ANSYS code are conducted to model three-dimensional transient analysis as well as the complicated soil pile interaction. In order to verify the validity numerical model, the numerical response is compared with reported results obtained by experimental cyclic load test performed on single pile penetrated in soft clay. Results show strong coupling between the two-orthogonal direction of lateral loading that decreases the lateral pile capacity. The interaction relation of biaxial loading with the factor b = 1.2 and 1.15 for one- and two-way loading respectively may well approximate the analysis results. The results of study are presented in terms of lateral cyclic capacities, pile head deflection, displacement profile and bending moment over the pile length. [ABSTRACT FROM AUTHOR]

In many projects, piles are designed and installed as the ultimate solution in foundation construction, load transition to the resistant subsurface layers, providing lateral resistance, and overcoming the poor performance of surface soils. Pile design should be done with respect to structural consideration, the load-carrying capacity of the surface and surrounding soil, settlement, and constructional, technical and environmental problems. Pile group is a particular type of deep foundations which is mostly and widely utilized in coastal and offshore structures, and sustains vertical and lateral loads. Noting the lateral load exerted on the structure, the effect of loading on the behavior of pile should be analyzed using an appropriate method. In this article, a 4x4 pile group with piles of 100 cm diameter and 10, 15-m in length with center-to-center spacing of 3 times the diameter are modeled using the Plaxis 3D Foundation, which uses the finite element method, and the Mohr-Coulomb model, and the behavior of the piles driven in sand and subjected to loading is studied. Taking the results, the mechanism of the pile group behavior under vertical, lateral, adjacent structures loads and bending moment is calculated, and displacement in the x-direction, y-direction, and along the length, bending moment, and bearing capacity along the length of the pile have been obtained for each pile. [ABSTRACT FROM AUTHOR]

Round-ended concrete-filled steel tubular (RECFST) columns are gaining increasing usage in bridge structures. During their service life, RECFST columns under eccentric compression may suffer from impact loading. This study conducted test and numerical investigations to assess the performance of RECFST columns under the coupled actions of compression, bending and lateral impact loads. Fourteen columns were fabricated and tested, considering the influences of axial-load ratio, bending moment and impact energy. The damage mode and the time histories of impact force and displacement were accessed and analyzed. The experimental findings revealed that the initial bending moment negatively affected the impact resistance of RECFSTs. In addition, finite element model was established in ABAQUS and calibrated against the test results. The calibrated model was then employed to conduct the failure mechanism analysis and parametric study. Finally, a single-degree-of-freedom (SDOF) analysis was conducted to predict the mid-height deflection of RECFST columns under combined action of compression, bending and lateral impact loads, by incorporating the influences of pre-axial load and initial bending moment. • Drop-hammer impact tests on RECFST columns with varying eccentric compression. • Coupling influence of compression, bending and lateral impact loads. • Prediction of mid-height deflection response using the SDOF method. [ABSTRACT FROM AUTHOR]

Offshore wind turbines (OWTs) are affected by wind, wave, and current during their service life, which lead to the substructures undergoing combined effects of complex lateral loads and local scour. This phenomenon poses a significant challenge to the bearing capacity and cyclic responses of the widely used rigid monopiles for OWTs. This study develops three-dimensional numerical model to investigate the behavior of a rigid monopile subjected to lateral monotonic and cyclic loads, considering the stress history alteration induced by local scour. The hysteresis and plasticity accumulation of soils are captured by a bounding surface model. An accurate and concise semi-implicit stress integration scheme is creatively proposed to effectively incorporate this advanced constitutive model into the finite element (FE) software. The numerical model is verified by comparing FE results with centrifuge test results. Subsequently, the key factors such as cumulative deformation characteristics and bending moments distribution are investigated under different scour and cyclic loading conditions. The results indicate that with the facilitation of proposed semi-implicit scheme, the bounding surface model is capable of capturing the deformation pattern and cumulative deformation behavior of laterally loaded rigid monopile, and the cyclic responses of the monopile are significantly affected by the local scour. [ABSTRACT FROM AUTHOR]

With the development of offshore wind power energy, the monopile-wheel composite foundation has attracted wide attentions from scholars as an innovative foundation for offshore wind turbines (OWTs). And in offshore engineering, the local scouring usually tends to weaken the bearing capacity by moving surrounding soil till even become a non-negligible reason for some engineering disasters. To explore this effect of local scour qualitatively and quantitatively, the scouring morphology of the monopile-friction wheel composite foundations under unidirectional flow are obtained by means of CFD. Then, a 3D finite element model is developed to estimate the bearing behaviors and deformation characteristics with the consideration of various scouring conditions. Both internal forces and failure envelopes under H-T combined loads are also obtained through numerical analysis. The results reveal that key scouring parameters significantly affect the bearing capacity and envelopes shrinkage of the composite foundation. In particular, the scouring depth has the greatest effect on lateral and torsional bearing behaviors of 15%–32% and 24%–58%, respectively, followed successively by the scouring angle and extent. And the loading point height has a noticeable impact on the lateral resistance of the composite foundation. The findings provide valuable insights into understanding the load bearing behaviors of composite foundations and their practical application in engineering. • Through CFD, the morphology of monopile-wheel composite foundations under unidirectional flow is simulated and the morphology is simplified to evaluate the local scour. • Through numerical simulations, the influence of key scouring parameters and different loading point heights on the bearing capacity for the monopile-friction wheel composite foundation is obtained. • The distribution of the bending moment and torque along the monopile is explored, taking into consideration different parameters. • The failure envelopes for the composite foundations under H - T combined loads with the consideration of key scouring parameters are also obtained. [ABSTRACT FROM AUTHOR]

Centrifuge modelling and finite element analysis are powerful tools of research on the lateral pile/soil interaction. This paper aims at presenting the main results of experimental and numerical analysis of the pile response under monotonic lateral loading in sand. After description of the experimental devices, it focuses on the determination of the load-transfer P-Y curves for rigid and semi-rigid piles embedded in dry dense sand by using the experimental bending moment profiles obtained in centrifuge tests, as well as by a three-dimensional finite element models using ABAQUS Software. The elastic perfectly plastic Mohr-Coulomb constitutive model has been used to describe the soil response, and the surface-to-surface contact method of ABAQUS software has been used to take into account the nonlinear response at soil/pile interface. The analysis methodology has allowed to propose a hyperbolic function as a model to construct P-Y curves for rigid and semi-rigid piles embedded in dry dense sand, this model is governed by two main parameters, which are the initial subgrade reaction modulus, and the lateral soil resistance, the latter has been formulated in terms of Rankine's passive earth pressure coefficient, the sand dry unit weight, and the pile diameter. [ABSTRACT FROM AUTHOR]

This study presents experimental and numerical research on the dynamic behaviors and resistances of square concrete-filled steel tubular members internally strengthened by I-shaped CFRP profile (SCFST-CFRP) with fixed boundary conditions subjected to lateral impact loads. Dynamic impact tests were conducted on five SCFST-CFRP specimens and a traditional concrete-filled steel tubular (SCFST) specimen, examining their dynamic responses with respect to deformation modes, impact force, displacement, and strain distribution at different levels of impact energies and impact momentums. The test results indicated that the deformation of the specimens was concentrated in the impact region, approximately 0.38 L above the base, due to the transient localized characteristics of the lateral impact load. In terms of displacement and impact force, the SCFST-CFRP member exhibited better impact resistance compared to the SCFST member. Finite element models of the SCFST-CFRP members were created using LS-DYNA and validated against the impact tests. These validated models were then utilized to explore the damage patterns, dynamic bending moment, and load transfer mechanism of the SCFST-CFRP member under lateral impact loading. Additionally, a parametric study was conducted to evaluate the effects of load and structural parameters, including CFRP profile, impact energy, and impact momentum, on the impact resistance and dynamic flexural capacity of the SCFST-CFRP member. The results demonstrate that the enhancement in impact resistance caused by the inner CFRP profile was more significant under higher impact energy. Based on the parametric analysis results, empirical equations were proposed to predict the dynamic flexural capacity of lateral impact-loaded SCFST-CFRP members. • Impact tests of CFST member strengthened with CFRP profile under fixed boundaries. • Evolutions and distributions of deformation and internal force were summarized. • Impact load transfer mechanisms of the composite member were revealed. • Effects of load and structural parameters on the impact resistance were evaluated. • An equation for the dynamic flexural capacity of the composite member was proposed. [ABSTRACT FROM AUTHOR]

In the recent past, in order to cater lateral loads, provision of fins to monopiles is evolving as an option for enhancing their lateral load capacity. Numerical and experimental studies pertaining to fin piles subjected to lateral loading are very limited. It is very difficult to understand the behaviour of fin piles through conventional soil pile theories, due to their different fin configurations. In the present study, three-dimensional finite element analyses were performed on regular piles (pile without fins) as well as fin piles. For fin piles, different fin lengths, orientation and position were considered during the analyses. The results have shown that fins placed at the top portion of the piles are more effective than fins placed at bottom of the pile. In all cases, fin piles exhibited more lateral load-carrying capacity compared to regular piles. When fin's length is less than half of the pile length, lateral load-carrying capacity of fin piles is same irrespective of their orientation. However, fin's orientation is significant, when fin length is more than 0.5 times length of piles, star fin piles exhibit more lateral load-carrying capacity compared to diagonal and straight fin piles. Fin piles experienced less bending moment compared to regular piles for a given lateral load. Further, it was also noticed that lateral load-carrying capacity of the fin piles depend upon fins' length and their orientation. [ABSTRACT FROM AUTHOR]

Pile foundations are the most popular form of deep foundations used for onshore and offshore structures. They are often used to transfer large loads from superstructures in to deeper competent soil layers, particularly when the structure is to be located on shallow weak soil layers. The main objective of this investigation is to study the pile model behavior under lateral load in homogeneous soils and investigate the results using Finite Element Analysis (FEA). A Finite Element Analysis based on mathematical code developed in commercial software MATLAB to find out the maximum deflection and bending moment of pile under different operating conditions. The heavy duty PVC pipe material is considered for the model pile while different soils viz. sand and Black Cotton (BC) soil are used with different subgrade modulus present within the range. A single hollow pile of 24 mm outside diameter with thickness of 2.3 mm is considered for the analysis. The length of the pile varies between 720 mm to 912 mm with an eccentricity of 61 mm from the ground level. Afterwards, the study is further extended with the parametric study under different operating conditions. Effect of length of the pile, diameter of the pile, lateral load and the soil subgrade reaction has been analyzed. The results found that, there is the increase in deflection for lower diameter, lower length, and lower subgrade reaction, whereas the increase in bending moment for higher diameter, higher length and lower subgrade reaction of the soil, respectively. [ABSTRACT FROM AUTHOR]

Effective and convenient prediction of the peak displacement of piles under collision conditions facilitates the design framework preparation and pile damage evaluation. Hence, an energy-based method was proposed to predict the peak displacement of the widely used steel casing composite (SCC) piles under impact loading. The pile deformation energy was first calculated based on its deformation characteristics and the relationship between the sectional bending moment and curvature. The pile deformation energy and pile–soil energy distribution ratio were then employed to determine the relationship between the total absorbed impact energy and pile head displacement, which was represented by curves. The peak pile displacement under lateral impact loading was finally obtained by interpolating the absorbed impact energy curves. By conducting sectional analysis of the pile considering the strain rate effects and using a structural pushover procedure, the peak pile head displacements for various collision cases were predicted with reasonable accuracy. The effectiveness and reliability of the proposed method were verified by comparing its results with those of previous reduced-scale impact tests and validated full-scale finite element models. • An energy-based method was proposed to predict the peak displacement of the SCC pile under lateral collision. • The proposed method required only impact energy input, sectional analysis, and pushover procedure. • The deformation and energy distribution characteristics of piles under static and impact loading were similar. • The SCC piles had two deformation forms: a single plastic hinge and a double plastic hinge. • Pile deformation energy was derived from its deformed shapes and the sectional bending moment–curvature relationship. [ABSTRACT FROM AUTHOR]

Tunnels are often preferred for underground transportation in densely populated areas. In these areas, it is almost inevitable for tunnels to run close to some existing pile foundations. Since tunnelling activities induce stress relief and soil movement in the ground, existing piles may suffer from additional axial and lateral forces, bending moments, settlements and lateral deflections. Most of the previous researches on the responses of pile foundations due to tunnel construction were carried out under the plane strain condition. In this paper, a three-dimensional, elasto-plastic and coupled-consolidation finite element parametric study has been carried out to investigate the effects of a 6 m open-face advancing tunnel on a two by two pile group in saturated stiff clay. The influence of different cover-to-diameter (C/D) tunnel ratios (namely 2.0, 2.5 & 3.0) was studied. The objectives of this study are to determine the changes in axial load distribution, changes in shaft resistance along the shaft of pile group and settlement of pile cap due to an advancing open-face tunnel. [ABSTRACT FROM AUTHOR]

Pile group is a particular type of deep foundations which is designed and installed as the ultimate solution to foundation construction, load transition to the resistant subsurface layers, providing lateral resistance, and overcoming the poor performance of surface soils. Pile design should be done with respect to structural consideration, the load-carrying capacity of the surface and surrounding soil, settlement, and constructional, technical and environmental problems. Piles are mostly and widely utilized in coastal and offshore structures, and sustain vertical and lateral loads. Considering the imposed loads on structure, the effect of these loads on the pile behavior should be analyzed with an appropriate method. In this study, a 4x4 pile group with piles of 100-cm diameter and center-to-center spacing of 2, 3, 4 times the diameter is modeled using the Plaxis 3D foundation program, which uses the finite element method, and the Mohr-Coulomb model, and the behavior of piles subjected to loading, driven in sand, are investigated. Taking the achieved results, the mechanism of the pile group behavior under composite loads, adjacent structure loads, and bending moment are calculated, and displacement in the x-direction, y-direction and along the length, the bending moment and the axial force for each pile within a distance of 2, 3, 4 times the diameter are attained. [ABSTRACT FROM AUTHOR]

[Display omitted] • Reinforced UHPC beams are tested against repeated impact loads. • UHPC constitutive model and bond-slip behaviour are considered in the numerical analysis. • Energy evolution diagram, dynamic shear force and bending moment distribution diagram are discussed. • Failure mechanism of UHPC beam under repeated impact load are evaluated in the parametric study. This paper investigates the dynamic response of hybrid fibre reinforced ultra-high performance concrete (UHPC) beams against single and repeated low-velocity impact loads. A brief description of the drop weight impact tests on the UHPC beams was presented first followed by the development of the material and structural model in finite element analysis. A plasticity-based concrete material model with validated compressive and tensile strength surface and damage algorithm was adopted for hybrid fibre reinforced UHPC material. Based on the test results, the bond-slip behaviour between steel rebar and UHPC matrix was developed in an empirical form and incorporated in the model. Compared to the model with the bond-slip definition, the model with perfect bonding was found to underestimate the maximum mid-span deflection, which highlighted the necessity of considering the bond-slip behaviour in dynamic analysis where large deflection occurs. The repeated impact tests were performed numerically, and the results were validated with experimental data. A parametric study was then performed to investigate the effect of key parameters, including different impact energy and the same impact energy but different impact numbers. The results indicated when the total energy increased, the repeated impact loads became more hazardous than the single impact load. With the validated model, the dynamic shear force and bending moment distribution diagrams were compared to study the failure mechanism in single and repeated impact loads. [ABSTRACT FROM AUTHOR]

In this study, the dynamic responses of a single pile in liquefiable sand under bidirectional loading are investigated using fully coupled three-dimensional nonlinear finite element analyses. A multi-surface plasticity model is adopted to simulate the liquefiable sand behaviour. The analysis procedures elaborate the bidirectional shaking patterns of 2-D linear, circular, and oval shape simultaneously. Results reveal that compared to the unidirectional loading, the bidirectional loading reduces the soil liquefaction resistance and increases the depth of liquefied soil layer. The results also showed that the phase difference between orthogonal components of base excitation and the frequency content of the input motion have a significant impact on the dynamic responses of soil and pile. In addition, an increase in the phase difference reduces the excess pore water pressure and the thickness of liquefied layer, and delays the liquefaction occurrence. Moreover, the maximum pile bending moment and its location correspond to the dominance of either inertia or kinematic interaction forces, which are primarily influenced by the frequency content of input motion. • Dynamic response of single pile embedded in liquefiable sand is investigated through a 3D nonlinear finite element model. • Seismic performance of soil-pile systems under unidirectional and bidirectional loadings is studied. • Soil-pile response is remarkably influenced by the pattern of bidirectional loading and its frequency content. • The frequency content of input motion has a decisive effect on the maximum pile bending moment. [ABSTRACT FROM AUTHOR]

Most of the routine work concerning the design of laterally loaded monopile foundations is conducted using simplified one-dimensional (1D) models based on p-y curves. However, many of these curves have been derived from slender piles typically used in the oil and gas industry, which behave differently than rigid monopiles used as offshore wind turbine foundations. Moreover, these curves usually represent the soil response without considering its degradation, which may significantly modify the monopile lateral response. Hence, this work proposes a numerical methodology based on the finite element method to derive suitable curves for 1D models of monopiles installed in sand. First, a three-dimensional (3D) finite element model (FEM) of the monopile and the surrounding soil was constructed. In this model, the monopile had an elastic and linear material behavior. The soil response was addressed using the Mohr-Coulomb criterion combined with three different soil stiffness degradation models. For extracting the p-y curves from the 3D FEM, a 10th-order polynomial was used to fit the bending moment profiles; consequently, an 8th-order polynomial described the soil reaction profiles. Results obtained using the proposed 3D FEM and a 1D model based on the derived p-y curves were then verified against experimental results obtained through centrifuge modeling. Furthermore, the proposed 1D model adequately matched the experimental results, especially for small displacement conditions. • Soil stiffness degradation should be considered for a proper soil modeling. • Analytical stiffness degradation models can ease the numerical soil modeling. • Good agreement between numerical and experimental results. • Numerical 1D models based on the p-y method led to fast and accurate results. • Contact modeling was found to be significant during the unloading phase. [ABSTRACT FROM AUTHOR]

Three-dimensional finite element analyses were performed to study the behavior of piles in sloping ground under undrained lateral loading conditions. Piles of different diameter and length in sloping cohesive soils of different undrained shear strength and several ground slopes were considered. Based on the results of the finite element analyses, analytical formulations are derived for the ultimate load per unit length and the initial stiffness of hyperbolic p-y curves. New p-y criteria for static loading of piles in clay are proposed, which take into account the inclination of the slope and the adhesion of the pile-slope interface. These curves are used through a commercial subgrade reaction computer code to parametrically analyze the effect of slope inclination and pile adhesion on lateral displacements and bending moments. To validate the proposed p-y curves, a number of well documented lateral load tests are analyzed. Remarkable agreement is obtained between predicted and measured responses for a wide range of soil undrained shear strength and pile diameter, length, and stiffness. [ABSTRACT FROM AUTHOR]

In order to investigate the liquefied soil pressure inposed on an individual pile of pile group, a centrifugal shake table test on a pile-supported wharf on the sloping saturated sand stratum has been designed and implemented in this study. Final test results, including processing results of free-field soil responses as well as lateral displacements at the deck, are presented and discussed in detail. Analysis of pile bending moments of pile group shows that seaside pile bottom can come under more bending moment in contrast to landside piles, and the bending moment seems greater at pile top and bottom. A simplified finite element model has been constructed for an accurate analysis of liquefied soil pressure arising from lateral soil flow, where triangular soil pressure and uniform soil pressure need to be calibrated according to the measured monotonic bending moment of piles. Furthermore, comparisons with the current distribution law were made using the experimental outcomes. Finally, for investigating the effect of pile connection point rotational stiffness, parametric studies were carried out. • Seismic behavior of the soil and pile-supported wharf in liquefiable sloping stratum is presented and analyzed. • A finite element modeling is developed to investigate liquefied flow soil pressure scenarios on the pile group. • Two force-based design guidelines from JRA and JSWA are further calibrated. • Influences of key factors on the behavior of pile-supported wharf are examined. [ABSTRACT FROM AUTHOR]

• Unified equations for stiffness amplification coefficient are proposed. • The beam-shell mixed element model is developed to conduct parametric analyses. • Consistency of formulae for lateral and vertical load cases is proved. • Modified formulae of the coefficient for asymmetric beams are derived. • Proposed equations provide good accuracy predicting critical structural indices. The slab spatial composite effect arises due to compatible deformation of the reinforced concrete slab with the steel beam in composite frames. This effect can significantly amplify the stiffness of composite frame beams. Current Chinese design code adopts the stiffness amplification coefficient method for the design of composite frame beams, and the equivalent moment of inertia of the composite frame beam can be calculated to conduct the global analysis. However, the current formulae are only suitable for lateral load cases and symmetric I-shaped steel section. Therefore, this study aims to propose unified design equations of the stiffness amplification coefficient considering both vertical and lateral load cases and both symmetric and asymmetric I-shaped steel sections to address the aforementioned limitations. A series of parametric finite element analyses using the beam-shell mixed element model are conducted to derive the unified design equations. The reasonability of the proposed equations is verified by comparing the critical structural indices, such as the natural vibration period, inter-storey shear, lateral displacement, bending moment, and deflection distribution of numerical examples of multi-storey composite frames. Good accuracy is obtained through the comparison between the linear beam element model modified by the proposed equations and the beam-shell mixed element model. [ABSTRACT FROM AUTHOR]

• Eccentric and/or inclined loads induce nonlinear roto-translational displacements of pile groups. • Simplified modelling (beams, elastic half-space, localised yielding) compared with advanced analyses. • Vertical eccentric loads mobilise the lateral soil resistance at large cap displacements. • Charts for the reduction in vertical capacity, at prescribed cap displacements, due to load eccentricity and inclination. This paper presents a numerical study of 3 × 3 pile groups embedded in clay under vertical and inclined eccentric loads. Simplified modelling, based on elastic beams embedded in a soil continuum, is used to explore the soil-pile-cap response. This simple model allows rigorous treatment of the 3D foundation geometry and local soil plasticity, demonstrated through validation with 3D finite element analysis. The numerical results reveal that complex roto-translational displacements of the pile group are induced by eccentric or inclined loads, with highly nonlinear relationships when soil plasticity is considered. Interestingly, vertical eccentric loads mobilise the lateral soil resistance at large cap displacements. Thus, while existing t-z type models are shown to be adequate for serviceability predictions, they could provide overly-conservative estimates of the ultimate load capacity. Also, foundation internal forces can exceed allowable bending moments of reinforced concrete piles under multi-directional loads. For performance based design of pile groups under inclined eccentric actions, engineers should estimate the impact of soil yielding on both displacements and rotations of the cap, to satisfy limit state requirements. Dimensionless charts are presented, which describe the reduction in vertical capacity, for a prescribed cap displacement, as a function of load eccentricity and inclination. [ABSTRACT FROM AUTHOR]

It is very important to analyze the lateral cyclic response of monopiles for the design of offshore wind turbines (OWTs). A three-dimensional finite element method for lateral cyclic responses of large-diameter monopiles is developed based on a simplified constitutive model of clays that has been successfully encoded into the ABAQUS software package. The applicability of this method is validated by simulating the existing centrifugal model test. The method can predict the nonlinear hysteresis responses of monopiles in clays during cyclic loading, and the evolution of bending moment and lateral deflection profile of monopile with loading cycles. Various lateral cyclic loads with different loading patterns including one-way and two-way loading, symmetric and asymmetric loading, variable-amplitude and constant-amplitude loading are applied to monopiles. The impact of different cyclic loading patterns on lateral responses of large-diameter monopiles is systematically investigated. The research results can provide some reference for the engineering design of large-diameter monopiles under lateral cyclic loads. [ABSTRACT FROM AUTHOR]

Geometrical deviations in the manufacture and assembly of mechanical products often result in non-parallel bearing surfaces in the bolted joint. To reveal the influence of the non-parallel bearing surface on the loosening of the bolted joint, the paper proposes a non-parallel bearing surface anti-loosening analysis model, revealing the anti-loosening mechanism of the non-parallel bearing surface, and found that the non-parallel bearing surface will introduce additional contact pressure and contact friction torque. Within a certain range, the contact pressure and the contact friction torque increase as the inclination angle of the non-parallel bearing surface increases, and the thread anti-loosening performance is improved. A parametric finite element model is further established to verify the existence of additional contact pressure and contact friction torque, and the slip factor is introduced to evaluate the loosening. Finally, the anti-loosening analysis model and the finite element model are validated by the loosening experiment of the non-parallel bearing surface. The research result provides a new idea for the anti-loosening control of bolted joints. • The non-parallel bearing surface creates a bending moment on the bolt joint that causes the threads to be subjected to the lateral force, and the nut moves laterally, pressing the thread contact pairs to create additional contact forces and contact friction torques. • The additional contact force and the contact friction torque increase the bolt's anti-loosening properties. • The anti-loosening ability of the non-parallel bearing surface is affected by the inclination angle, and the bigger the inclination angle, the stronger the anti-loosening ability. • In the simulation process, combined with the slip factor, the influence of non-parallel bearing surface is further revealed, and the relevant laws are consistent with the theory and experiment. [ABSTRACT FROM AUTHOR]