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The Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model integrated with the Volume of Fluid (VOF) method is applied to study the complex gas-fluid-particle coupled system. To enhance the model's feasibility, the efficiency and accuracy improvement approaches are implemented into the model, including the coarse-grained method, porous medium replacement and semi-resolved method. To validate the effectiveness and accuracy of the model, simulations of the particle water entry and dam break scenarios are conducted, Subsequently, the VOF-CFD-DEM model is utilized to study the sediment transportation under breaking waves. A comparison of various turbulence models reveals that the stabilized k - ω model can simulate the breaking wave with acceptable efficiency and accuracy. The study examines the flow characteristics, forces acting on slopes, and typical sediment movements, providing detailed case studies and data relevant to gas-fluid-particle systems. This work extends the application of the VOF-CFD-DEM model to extreme conditions in ocean engineering, offering a mesoscopic perspective on complex engineering challenges. [ABSTRACT FROM AUTHOR]

Understanding the pipeline scour mechanism under different conditions is essential for protection measures. The computational fluid dynamics (CFD) and discrete element method (DEM) are coupled for the simulations. To reduce the computational effort, the coarse-grained method is applied, and the Darcy-Forchheimer porous model is used to replace the far field elements. Both of the porous medium and particles-fluid interaction model are validated by comparison between simulation results and theories. The scouring simulation results show a good agreement with the experiments conducted with single-diameter spherical particles under different current-wave conditions. Further, the flow around the pipeline, the seepage in the sediment bed and the force acting on the particles are analyzed. The vortex shedding exists downstream under current but the vortex moves around under waves. The seepage depends on the pressure, influenced by the pipeline and the water depth, and the variation of the seepage is discussed. The force acting on the particles is not uniform along bed and the distribution is analyzed. This paper provides an insight into scour mechanics from the aspects including seepage and flow-particle interaction. Different methods are used for modification, giving a reference for the usage of CFD-DEM model in the analysis of scour process. [ABSTRACT FROM AUTHOR]

In the offshore environment, monopile foundations are facing significant local scour problems, which would have a serious negative impact on their stability and safety. The numerical simulation provides us with an efficient tool to investigate the patterns and underlying mechanisms of local scour. In this study, an Euler-Lagrange two-phase flow (CFD-DEM) model was employed to simulate local scour around monopiles. The CFD-DEM model was utilized to simulate several different scenarios, including sediment transport under undisturbed flow, flow around monopiles, and local scour around monopiles. In the first scenario, the LES model was incorporated to simulate turbulent flow, and it was observed that the CFD-LES-DEM model accurately predicted flow characteristics and sediment behavior within the water–sediment two-phase system. In the second scenario, the flow around the monopile was simulated under rigid bad conditions, and the characteristics of the flow field, including the horseshoe vortex and the wake vortex, were studied and validated. In the last scenario, the local scour around monopiles was simulated under different mean flow velocities, with simulation results being validated through model experiments. Based on experimental and numerical results, the phenomena and mechanisms of local scour were studied from a particle-scale perspective. [ABSTRACT FROM AUTHOR]

This paper demonstrates a series of 1 g model tests and numerical modelling in order to investigate the pushout extraction process of suction anchors in sand. The suction anchor models used in this study have aspect ratios of 1 and 2, and the pumping rate and soil permeability are varied to reveal their influence on the extraction process. It is shown that changes in the pumping rate and soil permeability rarely alter the overpressure during the extraction process but can affect the displacement rate and final extracted length of the suction anchor. The ratio of the final extracted length over the total length of the suction anchor is also found to be different for suction anchors with different aspect ratios in the 1 g model tests. Eventually, a calculation method for this pushout extraction process is proposed and validated to determine the peak overpressure with some basic parameters of the suction anchor and sands. The relationship between the pumping rate and the displacement rate of the suction anchor is also revealed in the calculation method. • Pumping rate and soil permeability barely affect the overpressure during extraction. • The final extracted length is dependent on the pumping rate and anchor geometry. • The initial displacement rate has a linear relationship with the pumping rate. • The overpressure can be obtained with basic parameters using the proposed method. [ABSTRACT FROM AUTHOR]

• A series of new connections were proposed for large-span steel hyperbolic towers. • The connections under bending and shear force was studied via experiments and numerical models. • Different connector types, row number of the bolts, and plate thickness were considered in the study. • The new connections have excellent bending stiffness and ultimate bending capacities. In this study, a series of new beam-column connections was proposed for large-span steel hyperbolic towers. The mechanical performance of the connections under an out-of-plane bending moment and a shear force was studied via experimental tests and numerical simulation. Different parameters such as the connector type, row number of the bolts, and plate thickness were considered during the study. The moment–rotation curves and main failure modes of the connections were obtained and discussed in detail. The results showed that the new beam-column connections proposed in this paper had excellent bending stiffness and ultimate bending capacities. In addition, the finite element model of the connections was established by ABAQUS software, and the experimental and numerical results were compared. The comparison results showed that the numerical model could predict the moment–rotation curve and different failure modes accurately. The new joint system and study presented in this paper are relevant references for the study of large-span steel hyperbolic towers, which are increasingly becoming the prominent options compared with concrete cooling towers. [ABSTRACT FROM AUTHOR]

In this study, the traditional Temcor joint (TR-Temcor) is modified using a central hollow hexagonal prism and some front bolts. The Finite Element Analysis (FEA) model is established and verified by experiments. Then, a parametric analysis is carried out for the improved Temcor joint (IM-Temcor). To obtain the optimal parameters for the modified joint, the key factors, namely: number and location of the front bolts, bolt-hole deviation, pretension force in bolts, thickness of front plate and heat-affected zone caused by the welding work, are considered in the FEA models. The modified joint, with the optimized factors, is analyzed for different static load conditions, considering axial pressure, axial tension, pure bending, bending with axial force, and eccentric axial forces. The overall mechanical behavior of the joint, including the M-Φ curves, initial stiffness, ultimate strength and deformation capacity, as well as the failure modes are identified. The results from the improved joint are compared with corresponding values from of the traditional Temcor joints. The results show that the central hollow hexagonal prism and front bolts significantly improves the stiffness and ultimate strength of the joint, especially when the joint is subjected to pure bending, bending with shear force, axial force, bending with certain axial force and eccentric force. • An improved Temcor joint system was designed. • FE model of the joint was established and verified. • Optimized analysis was conducted on the improved Temcor joint. • Mechanical behavior of the improved joint under different loading conditions were identified. • The new joint significantly improves the stiffness and ultimate strength of the traditional joint. [ABSTRACT FROM AUTHOR]

In recent years, the local scour has developed into a major threat to the safety of offshore group piles. The numerical simulation methods are useful tools in investigating the key mechanisms behind local scour. However, conventional simulation methods often neglect the microscopic sediment behavior, thus impeding a more profound understanding of the scour mechanism. In this research, the CFD-DEM method was applied to investigate the local scour around twin piles. And the coarse grain method and porous media model were incorporated to enhance simulation efficiency. The CFD-DEM model was constructed and validated using experimental data. Based on the validated model, a series of local scour simulations around twin piles were conducted under different arrangements. The time-development curves of scour depth were analyzed, and the variation of the equilibrium scour depth with pile spacing exhibits good agreement with the dates from previous studies. Based on the simulation results, the flow field, scour pit morphology, sediment flux, and microscopic behavior of sediment around twin piles were analyzed under different arrangements, and four key mechanisms of twin piles' local scour were observed and analyzed during this process. [ABSTRACT FROM AUTHOR]

To study the cyclic behaviour of a novel gear–bolt semi-rigid joint, quasi-static tests were conducted on seven full-size specimens. The key parameters of the gear–bolt joint investigated in this test include the gear–bolt diameter, number of teeth, and tooth depth to gear-bolt diameter ratio ( t/d ). A detailed research is carried out to study the effects of these parameters on the hysteresis curves, skeleton curves, degraded characteristics, ultimate capacity, energy-dissipation capacity, and failure mode. The experimental results showed that the hysteresis performance was enhanced with the increasing of number of teeth, gear–bolt diameter, and t/d . In particular, the hysteresis curves were fuller with higher number of teeth; however, an excessive number of teeth should be avoided as it would lead to a brittle rupture of the teeth. The ultimate capacity increased with the increase in the gear–bolt diameter and t/d . of accurate finite-element (FE) models of gear-bolt joint considered the geometry and material nonlinearity was established, and the accuracy of the FE mode was verified by comparison of the computation with test results. [ABSTRACT FROM AUTHOR]

When the required suction of the suction foundation exceeds the critical suction, piping will occur in sands, leading to the failure of the installation process. The reliable prediction method of installation suction and critical suction for the suction foundations is significant. This paper introduces and discusses five prediction methods of installation suction and seven prediction methods of critical suction which are used to analyze the installation suction and critical suction of two offshore prototype suction foundations with different lengths. It is found that the predicted critical suction is about 1.68–2.6 times the installation suction for the short foundation, while it is only about 1.06–1.34 times the installation suction for the long foundation. The calculated suctions by different methods are then compared with the in-situ measured suctions of the two foundations. The results show that the prediction methods based on the Cone Penetration Testing (CPT) results have the advantages of convenience and accuracy in engineering practice. Based on this method, the influence of hydraulic gradient on the effective stress of sands during the penetration process is considered. A new method for predicting installation suction considering the effect of hydraulic gradient on the effective stress (HG-ES method) is proposed. The accuracy of the new method is verified using the offshore in-situ test data. Using the HG-ES method instead of the DNV method to predict the installation suction will help reduce the relative error from 18% to 11% for the long foundation. • A new suction prediction method considering the effect of hydraulic gradient on effective stress (HG-ES method) is proposed. • The short foundation reaching critical suction offers a greater safety redundancy compared to the long foundation. • CPT-based methods for the estimation of required suction of the suction caisson installations in sand are shown to display higher accuracy. • For the long slender suction foundation installed in sand, as the installation depth increases, the hydraulic gradient around the foundation first rapidly increases, and then the trend slows down. [ABSTRACT FROM AUTHOR]

To investigate the meso -mechanism of scouring process, a numerical model that couples the porous medium model, computational fluid dynamics and discrete elements method (PORO-CFD-DEM model) is established and validated. Two pipeline conditions, suspended and partially buried, are considered. The porous medium is used to replace most of the discrete elements, significantly reducing the computational requirements. Two particle generation methods, namely fictious grid method (FGM) and breath-first search method (BFM), are proposed, and three kinds of particle samples are generated with different gradations: Gaussian, gap and continuous. Detailed analyses of flow, fluid-particle interaction and sediment motion is conducted with an increasing inlet velocity. When the pipeline is suspended, the seepage flow is induced by the gap flow beneath the pipeline, with the pressure dropping along the seepage path. Around partially buried pipeline, the seepage flow is much weaker and the pressure concentration appears. The seepage force fluctuates, and the loose bed is disturbed, leading to randomly collapses. Different particle movement patterns, including the jumping, suspended transportation and the formation of sand slope, are captured during the simulations. It's confirmed that the PORO-CFD-DEM model can capture the meso -movement of the particles and provides insights into the theory of sediment transportation. [ABSTRACT FROM AUTHOR]

The nodal connection system for the free-form grid spatial structures should both implement complex-shaped curvature and fulfil the required loading capacity, whilst also meeting various important requirements, such as quick and easy assembly at the construction site. A novel joint system named gear joint with the above advantages, developed for free-form grid spatial structures, is presented in this paper. First, a series of tests was carried out considering different bolt diameters, tooth heights, tooth numbers and ball thicknesses. The different failure modes and whole moment-rotation ( M-Ф ) curves of gear bolt joints were obtained, and the joint stiffness and strength were investigated. Second, a three-dimensional finite element (FE) model of the joint was established. The comparison between computation and experiments highlights the degree of accuracy of the proposed FE model. The stiffnesses, strengths, rotation behaviours, and failure modes of the new joint system were carefully compared and discussed. Based on the results, the influence rules of the parameters on the mechanical behaviour of the new joint were obtained. Finally, based on the power-function model, the formulae for predicting the M-Ф curves of the joints were established. The M-Ф curves have preferable accuracy compared with the experimental curves. [ABSTRACT FROM AUTHOR]

Most of the existing studies on reticulated shells with a semi-rigid joint system have been focused on the mechanical properties under static loads. Taking material and geometric nonlinearities into account, the finite element analysis (FEA) model of a single-layer reticulated shell with semi-rigid joints was established using the software ABAQUS and then validated through comparison with the experimental result. Based on the bending stiffness of a bolt-column (BC) joint obtained through experiments, the dynamic behaviour and a seismic design method for single-layer reticulated shells with semi-rigid joints were investigated in this paper. First, analysis of the free vibration frequency of the single-layer latticed domes with semi-rigid bolt-column (BC) joints was conducted based on several different parameters, including joint stiffness, ratio of rise to span, initial geometric imperfection. Second, the seismic internal force coefficient of the members of the semi-rigidly jointed spherical single-layer reticulated shells of different parameters was studied in detail. Finally, the seismic internal force coefficients for spherical single-layer reticulated shells with semi-rigid joints under a common earthquake were derived. [ABSTRACT FROM AUTHOR]

Scour is a key issue affecting the service life of submarine pipelines. Understanding the scour process and scour mechanism around the pipelines is crucial for developing the reasonable and effective scour prevention measures. In this paper, the computational fluid dynamics and coarse-grained discrete element method (CFD-CGDEM) is used to simulate the scour process around the pipeline. The influence of the drag force model which is an important factor for analyzing the scour process of the submarine pipelines is investigated, and the results indicate that the choice of the drag force model has less influence on the simulation results. The characteristic of the CG method is studied considering different CG factors, particle radius and flow velocities. The results show that the CG method which can reduce the large need of computing resources and excessive computation time does not bring large deviation to the results, especially the scour depth beneath the pipelines. The evolution of the scour depth obtained by the CFD-CGDEM model agree well with the experimental results. A reasonable scour phenomenon around the pipeline is shown by the numerical simulation, which implies that the CFD-CGDEM model established in present study can simulate the scour process around the pipelines well. • CFD-CGDEM models are set up to simulate the scour process around the pipelines. • Influence of different drag force model and CG factor are studied and discussed in detail. • CFD-CGDEM model is validated by comparing with experimental results. • The mechanism of the scour around the pipeline is studied on the aspect of the particles motion and the seepage. [ABSTRACT FROM AUTHOR]

Recent challenge for large-span single-layer reticulated structures is the development of a new joint that can provide these structures with adequate stiffness while satisfying various important requirements, such as easy assembly on a construction site. In this paper, a new semi-rigid joint system, which is referred to as the bolt-column (BC) joint, is developed. A series of tests was performed considering different thicknesses of the side plates, pretension forces and diameters of the bolts. A three-dimensional finite element (FE) model of the joint was developed to evaluate the bending stiffness, moment resistance, rotational capacity and failure mode of the joint. A comparison between the computations and experiments highlights the degree of accuracy of the proposed FE models. The moment-rotation curves, which can be introduced in the analysis of the structure, were obtained. The stiffnesses, strengths, rotation behaviours, and failure modes of the joints are carefully compared and discussed. Based on the results, the influence rules of the parameters on the mechanical behaviour of the new joint are obtained, which are helpful for engineers and designers. The results indicate that the application of this type of joint in construction practice is promising. The experimental results are employed to calibrate the finite element models, which are used to conduct a parametric study. [ABSTRACT FROM AUTHOR]

The bolt–column (BC) joint, which can efficiently connect H, I and rectangular section members, is actually semi-rigid and of partial strength. The consideration of real semi-rigid behaviour can lead to a more accurate global analysis and, consequently, more optimized structures. In this paper a parametric analysis is conducted on the joint. A total of 341 models, divided into five series G1–G6, were analyzed. The main parameters affecting the rotational capacity and failure mode of the joint were considered in the finite element (FE) models. First, the optimal geometric parameters, such as the suitable thickness of the side plate and front plate, were obtained and discussed. Second, the mechanical behaviour of the joints under different static load conditions, including pure bending moment, eccentric pressure, eccentric tension, bending with a defined pressure and bending with a defined tension force, was investigated in detail. The theoretical equations and envelope curves for predicting the moment capacity of the joints under eccentric forces and bending with axial forces were established. Furthermore, based on the component methods in Eurocode 3 (EC3) (CEN, 2005) [1], a trilinear mathematical model for predicting the moment–rotation relationship of the joints was developed. The moment–rotation curves obtained by the mathematical model compare very satisfactorily with the experimental results. [ABSTRACT FROM AUTHOR]

SWRH82B steel wires are commonly used in suspended-cable structures, large-span structures, and cable-stayed bridges owing to their light weight, strong bearing capacity, and safe and reliable operation. In this study, the dynamic mechanical performance of SWRH82B steel wires under low-velocity impact was studied experimentally and numerically. A drop-hammer impact test system was adopted for the impact experiments, considering the influence of the specimen diameter, specimen span, indenter shape, and impact position. Two-section steel wires, including circular and Z -shaped wires, were investigated. The experimental results indicated that local denting deformation occurred at the impact position with a lower impact energy, and wire breakage occurred near the position of the clamping device with a larger impact energy. Circular wires were stronger and stiffer than Z -shaped wires of the same diameter because they can provide a higher impact resistance and stronger energy absorption capacity with a regular section shape. The experimental data indicated that the specimen diameter positively affects the impact bearing capacity, providing more flexural rigidity. However, the specimen span negatively influences the dynamic performance of both types of steel wires; a greater increase in peak load was observed when using a cylinder hammer. In addition, a finite element model was established to further analyze the failure modes and discuss a larger range of parameters. Finally, a numerical model of prestressed steel wires was developed using ABAQUS/EXPLICIT, with the results indicating that the prestress force could strengthen the impact resistance of steel wires at a lower level. • Drop-hammer impact experiments were conducted on SWRH82B steel wires to investigate the effects of impact response and failure modes with 18 specimens. • A numerical model was established using ABAQUS/EXPLICIT. The model was validated by comparing the numerical results with the experimental data considering different parameters. • Three typical failure modes were identified: local denting, breakage near the clamping system, and punching failure. • Simulation work considering prestress was conducted. [ABSTRACT FROM AUTHOR]

Offshore pipelines are often suspended or partially-buried during operating process. Understanding the scouring mechanism of the suspended and partially-buried pipelines is important for protecting the pipelines. The numerical models of pipelines under steady flow are established, in which Reynolds Averaged Navier-Stocks equation (RANS) with the k-ω turbulence closure, as well as the sediment transport equation, are solved with the finite volume method. After experimental verification, the models are applied to a series of parametric analysis for the suspended and partially-buried pipelines under steady flow. The effect of different variables such as the pipe diameter D , the suspension height e , the pipe shape, the embedment depth, on the scour process of the pipelines are investigated in detail based on more than 150 simulation results. For the suspended pipelines, the gap-to-diameter ratio e / D is the key parameter to predict scour depth. The pipe shape has an influence on the scour depth and the position of the scour hole. A formula to predict scour depth in terms of e/D and the relation between gap velocity and scour depth is obtained. For the partially-buried pipelines, the block height and the curvature of the pipeline is proposed as the key parameters to analyze the flow field around the pipeline. • The numerical model of pipelines under steady flow are established and verified. • Effect of different parameters on scour process of offshore pipelines are studied. • Formula to predict scour depth in terms of e / D is proposed for suspended pipelines. • Block height and curvature are key data to analyze flow of partially-buried pipelines. [ABSTRACT FROM AUTHOR]

Most existing studies on single-layer spatial structures with semi-rigid joints were focused on spherical domes. The present paper analyzed the squared plan-form single-layer structures, examining the influence of joint-rigidity on the mechanical performances of the structures. An experiment has been conducted on a 5×6 m single-layer cylindrical reticulated shell with semi-rigid bolt-ball joints. The mechanical performance of the latticed shell is investigated in detail. Finite element analysis (FEA) model of the latticed shell is established taking material and geometric nonlinearities into account. The results show that the behavior determined using the FEA models correlates well with the experimentally observed behavior for the single-layer structures with semi-rigid joints. [ABSTRACT FROM AUTHOR]

Abstract: Socket joint systems are typical semi-rigid joints used in space structures. This paper presents numerical analyses of semi-rigid joint systems in which the bolts are pretensioned. Eleven numerical models of socket joints are studied: three of them are subjected to bending and the others are subjected to proportional bending and axial compression. Moment–rotation relationships of the joints are obtained using models in which the material and geometric nonlinearity are taken into account. The load-carrying mechanism of socket joint system is investigated in detail through the numerical analysis. Through comparison of the finite element analysis (FEA) and corresponding test measurements, it is shown that the proposed FEA models can be used effectively to describe the mechanical performance of the semi-rigid joints in spatial structures, including the initial bending stiffness, ultimate bending moment, deformation and the failure mode. [Copyright &y& Elsevier]

Abstract: Based on the bending stiffness of socket joints obtained through experiments, the finite element models of single-layer elliptical paraboloid latticed shells with the semi-rigid socket joints are established. Parametric analysis of the latticed shells is carried out using ANSYS. The parameters considered are bending stiffness, ratio of rise to span, rotation-stiffness, ball size, asymmetric load distribution, tube section, support conditions and initial imperfections. The effects of the different parameters on the critical loads of the shells are thereby identified. Both geometric and material nonlinearity are considered during the analysis. Finally, formulae are derived for the calculation of critical loads of the shells under symmetric and asymmetric loading conditions. This will be useful for the design and application of single-layer latticed shells with semi-rigid joints. [Copyright &y& Elsevier]

Abstract: Socket joints and bolt-ball joints are typical semi-rigid joint systems widely used in spatial structures. In this paper, tests on fifteen joints are carried out to study their mechanical behavior. Three socket joint systems are subjected to bending moment and shear force, and another seven socket joint systems and five bolt-ball joint systems are subjected to bending moment, shear force and axial compressive force. The main characteristics of the moment–rotation relationship for the connections under different loading schemes are summarized and discussed. The results indicate that: (i) both socket and bolt-ball joint systems have good bending stiffness; (ii) the axial compressive force increases the initial bending stiffness of the joints; (iii) the axial compressive force has different effects on the bending moment capacity of different joints; and (iv) the yield process of moment–rotation curves of the joints is shortened due to the action of the axial compressive force. [Copyright &y& Elsevier]

Abstract: A new classification system for the joints in lattice shells is proposed. The stiffness and moment capacity of the joints together with the overall structural behavior of the lattice shells are considered in order to establish the classification system. According to this new system, joints in lattice shells can be classified into unique categories: rigid, semi-rigid or pinned. The rigid joints have both high bending stiffness and moment capacity; the semi-rigid joints have both moderate bending stiffness and moment capacity, and the pinned joints have either low bending stiffness or low moment capacity. Determination coefficients α and β are defined, based on the stiffness and moment capacity of the joints, and these are used to establish clear boundaries between the different categories. Some numerical examples are included to demonstrate the validity of the classification system. With the help of the classification system, an efficient process for practical engineering design is proposed, which can help designers choose the appropriate analysis method for lattice shells with different joints. [Copyright &y& Elsevier]

To study the stability of aluminum alloy columns (AACs) under an axial compressive load and a bending moment at high temperatures, 30 AACs under eccentric compression were tested in a high-temperature environment. All the specimens were H-shaped, and the material was 6082-T6 aluminum alloy. After the test, it was found that all the AACs suffered bending and torsional instability. ABAQUS software was used to establish a finite element (FE) model. The accuracy of the FE model was validated by comparing the experimental results with those of the FE model. A design formula for the stability capacity of AACs under eccentric compression at high temperatures was proposed. To study the reliability of the formula, 2520 FE models were established at five different temperatures with two different cross sections. The results showed that the formula for the stability bearing capacity of AACs under eccentric compression at high temperatures was safe and reliable. Finally, the test results were compared with the results obtained using a fitting formula and European standard EC9. The results of EC9 were found to be more conservative, while the results of the fitting formula were closer to the experimental data. • 30 6082-T6 aluminum columns under eccentric compression were tested at high temperatures. • Capacity formula for aluminum columns under eccentric compression at high temperatures was proposed. • 2520 FE models were established at five different temperatures to verify the proposed formula. • The results of the fitting formula were closer to the experimental data compared with EC9. [ABSTRACT FROM AUTHOR]

In this study, the parameters of the Johnson-Cook model of SWRH82B steel are determined to describe the dynamic mechanical properties and fracture behaviors of steel wires. A total of 299 specimens are tested to determine the parameters. Quasi-static tensile tests at varying temperatures (20–700 °C) and different strain rates (10−4–10 −2 s −1) and split Hopkinson pressure bar tests are conducted to identify the parameters of the Johnson-Cook model. Notch tensile tests are conducted to calibrate the Johnson-Cook fracture criterion model. The wires made from SWRH82B high-strength steel with different diameters and shapes have different material performance due to different manufacturing and cold-drawing process. Therefore, two cross-section types (circular and Z shapes) and seven diameters of high-strength steel wires are considered for the material characteristic tests. The strain rate hardening effect is not significant at low loading rates but has a remarkable effect at loads exceeding. Analysis of the stress-strain curves at elevated temperatures shows that the thermal softening effect of the two types of wires is evident and that the temperature sensitivity varies in different temperature ranges. In addition, the mechanical performance of circular wires with diameters ranging from 4.0 to 5.2 mm and Z -shaped wires with diameters from 4 to 6 mm are compared. Fractography of SWRH82B high-strength steel is conducted to investigate the failure mechanism at various temperatures and strain loading rates. Finally, an improved Johnson-Cook model is proposed considering the strain hardening of SWRH82B steel wires based on different shapes and diameters. [Display omitted] • The Johnson-Cook constitutive and the damage criterion parameters for SWRH82B steel are calibrated. • Microstructure tests are conducted to explain the thermal softening and strain-rate hardening effect. • A modified Johnson-Cook constitutive model for SWRH82B steel is proposed. • The results indicate the modified model is more accurate for SWRH82B steel. [ABSTRACT FROM AUTHOR]

With the increasing demand for clean and renewable energy, offshore wind turbines are growing in size and are being positioned closer to deep waters. This trend presents significant aerodynamic research challenges for floating offshore wind turbines, including aeroelasticity and unsteady problems due to large blade deformations and the dynamic motions of floating support structures in complex ocean environments. Traditional methods such as Computational Fluid Dynamics (CFD) and Blade Element Momentum (BEM) theory struggle to balance computational efficiency and accuracy in these challenging conditions. In contrast, the Vortex Lattice Method (VLM) has been validated in several studies for providing accurate results while requiring fewer computational resources. VLM can reduce the computational cost by at least 50% compared to CFD while maintaining comparable accuracy. Compared to the BEM, the VLM offers superior geometric and physical fidelity, thus achieving higher accuracy, while the increasing in computational cost remains acceptable. Furthermore, VLM shows much promise for extending its capabilities to study nonlinear aeroelastic problems rather than BEM. This paper reviews the development of VLM and its application in aerodynamic calculations for offshore wind turbines. It compares VLM with other aerodynamic methods and discusses potential research directions for its application in offshore wind turbine aerodynamics. • The application of Vortex lattice method on offshore wind turbines are reviewed. • The aspects including the accuracy and efficiency of VLM are compared with other methods. • The development process of VLM and its applicaiton on aerodynamics is presented and discussed. • Future research directions regarding VLM applied on offshore wind turbine issues are discussed in detail. [ABSTRACT FROM AUTHOR]

Based on the experimental and numerical bending-rotation (M - Φ) curves of a new semirigid connection, the finite element model (FEM) of a semi-rigidly jointed reticulated steel (SJRS) cooling tower structure is established. Considering the connection stiffness (including rigid and semirigid), height, and mesh size, the dual nonlinear stability behavior of the SJRS cooling tower is analyzed. The complete load–displacement curves, buckling modes, and percentage of different connection statuses (linear, elastic–plastic, plastic, and unloading states) in the structure are obtained. Further, the influence rules of each parameter on the structural stability performance are analyzed in detail. Three main buckling modes, two local buckling modes (Mode-I and Mode-II), and one overall buckling mode (Mode-III) are obtained for the SJRS cooling towers with different connection stiffnesses. The results indicate the good carrying capacity of the steel cooling towers, and that the effect of bending stiffness on the stability of the SJRS cooling towers varies significantly with height, and the bending stiffness of the connection around the z-axis is the key factor affecting the critical load and buckling mode of the cooling towers. • The FEM of semi-rigidly jointed reticulated steel cooling tower structure is established. • The influence rules of key parameter on the structural stability performance are analyzed in detail. • Two local buckling modes, and one overall buckling mode are obtained. • The results indicate the good carrying capacity of the steel cooling towers. [ABSTRACT FROM AUTHOR]

In this study, the material and stability of 10 axial compression aluminum alloy columns are systematically tested at five temperatures. The material grade of the aluminum alloy used in the tests is 6082-T6. The experimental results demonstrate that flexural buckling occurs in all the column specimens under different temperature environments. A finite element (FE) model of the experiment is established, and the obtained results are compared with the experimental results to verify the accuracy of the FE model. To study the stability at different temperatures, 765 FE models considering geometry and material nonlinearity are created in five different temperature environments. Three section types (H-type, rectangular, and circular tube sections), three sectional dimensions for each section type, and 17 slenderness ratios are considered in the models. Based on the FE results and the statistical regression method, the formula for calculating the stability coefficient for the columns with different slenderness ratios at different temperatures is fitted. The fitting formula is compared with the test results, Chinese Code (GB), and European Code (EC9). The comparison results demonstrate that the fitting formula can provide a more accurate stability coefficient for the columns at different temperatures. • Ten 6082-T6 aluminum columns under axial compression at five temperatures were tested. • 765 FEM with different parameters were analyzed at five different temperatures. • Formula for calculating the stability coefficient for the columns at different temperatures is fitted. • The fitting formula provide a more accurate stability coefficient at different temperatures than GB and EC9. [ABSTRACT FROM AUTHOR]

A single-layer reticulated steel (SRS) cooling tower consists of members and joints. Joint stiffness is an important component of SRS cooling towers, as it significantly influences the overall behavior of the structure. A new semi-rigid joint system consisting of H-shaped and C-shaped rolled steel, known as an HCR joint, has been developed for application in SRS cooling towers. In this study, a finite element (FE) model of an HCR joint under bending conditions is established and verified by joint tests. Then, HCR joints subjected to different loading combinations, including bending and shear forces, bending and certain axial forces, and eccentric forces, are numerically analyzed. The bending moment-rotation (M - Φ) curves and change rules for the stiffness and ultimate bending capacity are obtained. Next, the stability of SRS cooling towers with semi-rigid HCR joints is analyzed based on the M - Φ curves of the HCR joints under various eccentric forces. Two FE models of the structures are established. In FE Model-1, the stiffness of the HCR joints under a bending load is used for all of the joints in the structure. In FE Model-2, the stiffness of the HCR joints under different eccentric forces are used based on the different ratios of bending force to axial force in the joints at different locations in the structure. During the analysis, the structural height, grid size, and joint stiffness are considered, and the effect of the parameters on the critical load and buckling mode of the structure is determined. [ABSTRACT FROM AUTHOR]

• New joint for connecting aluminum rectangular hollow section members is proposed. • Six different full-scale ARH joints are tested under an out-of-plane bending moment. • The M-Φ curves, stress variation, and failure modes of the ARH joint are obtained. • A bilinear model is proposed to summarize the M-Φ curves of the joint. • The influence of different factors on mechanical behavior of ARH joints is analyzed. A new joint system for connecting aluminum alloy rectangular hollow section (ARH) members is proposed to overcome the problem of connecting rectangular tubes using the traditional Temcor joint. The structural performance of the ARH joint system under an out-of-plane bending moment is studied experimentally. The moment-rotation (M-Φ) curves, stress variation, and failure modes of the ARH joint obtained from the tests are discussed. A bilinear model is proposed to summarize the M-Φ curves of the joint. The influence of the key parameters, gusset thickness and bolt quantity on the mechanical behavior of the ARH joint is analyzed. Subsequently, finite element analysis is conducted to investigate the moment rotational behavior of the ARH joint. The comparison between the experimental and numerical results proves that the proposed finite element model is accurate enough and can be used to study the moment resistance behavior of the ARH joint system. The results show that the proposed ARH joint, for connecting rectangular hollow section members, can be considered as a semi-rigid connection. This study provides a reference for the practical application of the ARH joint in reticulated structures made of aluminum rectangular members. [ABSTRACT FROM AUTHOR]

• Tests of the two joint systems under out-of-plane and in-plane bending were conducted. • FE model of the two joint systems was established and verified. • The M-Φ curves and failure modes of the two joints were obtained, compared and discussed. • Parametric analysis is carried out to study the mechanical behavior of the new joint. • Different loading combinations of axial force and bending were considered during analysis. The static behavior of the traditional aluminum alloy Temcor (AAT) joint system and a new aluminum alloy hollow prism-plate (AHP) joint system is studied experimentally. The bending moment-rotation curves and failure modes for the two joint systems under out-of-plane bending (M x) and in-plane bending (M y) are obtained. The test results indicate that the bending stiffness and carrying capacity of the new hollow prism-plate (AHP) joint is superior to that of the traditional Temcor (AAT) joint. The refined finite element model (FEM) of the two kind of aluminum alloy joint systems are established based on a large-scale finite element analysis software. The simulation results are verified by comparing with the experimental results. Finally, to investigate the mechanical behavior and force transfer mechanism of the new hollow prism-plate (AHP) joint system, the parametric analysis is carried out to obtain the moment-rotation (force-displacement) curves and failure modes of the joint system under different loading conditions, including axial compression force, axial tension force, bending with compression force, and bending with tension force. [ABSTRACT FROM AUTHOR]

• Sensitivity analysis was carried out on modeling parameters of reticulated shells. • Probabilistic seismic demand and capacity models were established. • Fragility curves of reticulated shells were obtained based on IDA results. Single-layer aluminium alloy cylindrical shells are established using the powerful finite element (FE) software package ABAQUS. Furthermore, the probability distribution models of different random parameters in structural modelling are summarized. Forty seismic ground motion records are selected to consider the uncertainty of earthquakes. Sensitivity analysis of modelling parameters is conducted to determine the parameters with the greatest influence on seismic responses. The incremental dynamic analysis (IDA) method is performed on aluminium alloy cylindrical latticed shell structures with different structural parameters. After applying the damage index and structural performance levels of the latticed shells proposed in this paper, the probabilistic seismic demand model and probabilistic seismic capacity model are established. The seismic performance and the collapse capacity of different aluminium alloy cylindrical latticed shells are discussed based on the FE results. Furthermore, vulnerability curves are obtained according to the IDA results, which can be utilized to predict the failure probability and to evaluate the structural performance of aluminium alloy cylindrical latticed shells under different levels of earthquakes. [ABSTRACT FROM AUTHOR]

The risks posed by local scour around offshore monopile foundations are substantial and threaten the structural safety of these installations. It is therefore essential to study the mechanisms of local scour to mitigate these risks. Numerical simulation is an effective tool to help us understand the mechanisms of local scour. However, the accurate modeling of the local scour process remains to be challenging due to the complexity of sediment transportation, in which the continuity threatment of sediment phase is typically used, the discrete behavior of the sediment is hard to be described. Therefore, in this paper, in order to conduct the deepin investigation into the mechanism of the local scour around monopile, a three-dimensional CFD-DEM model was established by coupling the computational fluid dynamic method (CFD) and discrete element method (DEM). To increase the efficiency and accuracy of the CFD-DEM model, the coarse grain method (CGM) was used to decrease the number of required DEM particles in the simulation, and the angle of repose was used to calibrate the contact parameters between DEM particles. During the validation process of the numerical model, it was found that the development of the scour depth and the morphology of scour pit obtained by the CFD-DEM model showed good agreement with the previously published results. The CFD-DEM simulation revealed that seepage-induced vertical drag force plays a crucial role in the initial stage of local scour. Two sediment transportation processes, "Pile toe erosion-Slope avalanche" and "Push-Accumulation-Wash", were observed and the relationship between bedload sediment flux and the Shields number was quantified. In the end of this paper, the critical evaluation of the CFD-DEM method was conducted. • The first time that the CFD-DEM method is used to research the sediment motion during the local scour around monopile. • The coarse grain method is used to improve the efficiency of CFD-DEM coupling method. • The seepage-induced vertical drag force was proved to be crucial in the early stage of local scour around monopile. • The "Pile toe erosion-Slope avalanche" and "Push-Accumulation-Wash" process of sediment transportation were observed. • A method is proposed to convert the parameters of discrete phase into the continuous phase parameters. [ABSTRACT FROM AUTHOR]

Local scour refers to the erosion or migration of sedimental particles around bridge piers or abutments under the action of water flow. It can potentially undermine the hydraulic structures, resulting in catastrophic damage or even collapse. Under various hydraulic conditions, monopiles with diverse cross-sectional shapes have increasingly been applied to marine foundations. This study aims to investigate the effect of monopile shapes on scour development, and to establish a cross-scale connection between the macroscopic evolution of scour pits and the microscopic characteristics of sediments. The scour processes around monopiles are simulated using a coupled computational fluid dynamics and discrete element method (CFD-DEM). Four monopile shapes are examined, including circular, square, square with rounded corners, and diamond. Macroscopic characteristics such as seabed morphology, maximum scouring depth, and scour areas are analyzed, along with the microscopic characteristics such as the kinetic energy, drag force, and mechanical coordination number. The outcomes highlight that the diamond-shaped pile results in the greatest scour depth and widest scour areas compared to the other shapes. The incorporation of rounded pile corners improves flow characteristics and mitigate scour pit development. Furthermore, the local scour at different areas around the monopiles varies under the influence of different flow features. [ABSTRACT FROM AUTHOR]

In this study, the dynamic performance of a long curved river-crossing pipeline with multiple floating bodies during immersion process is investigated in detail. Based on the pipeline theory, six degree-of-freedom buoy theory, winch theory, and multi-body coupling theory, a numerical model of the immersion system with multiple floating bodies is established. The numerical calculation method is observed to conform well with the field measurement results. The dynamic performance of the immersion system is comprehensively investigated based on varying key parameters, e.g. the deflation time of the airbags, lowering speed of the suspension cables, and airbag deflation methods. The results from the numerical simulations indicate that the immersion process for the pipeline with the proposed construction method is safe, stable, and controllable. The presented numerical calculations and results can provide valuable construction recommendations to avoid potential engineering risks and ensure the economic efficiency of this or future similar projects. • A dynamic pipeline immersion project for a long curved river-crossing pipeline and multiple floating bodies is investigated. • The dynamic performance of the pipeline during the immersion process is investigated. • The numerical calculation method conforms well with the field measurement results. [ABSTRACT FROM AUTHOR]

Rammed earth-timber joints without enlarged ends have been used in rammed earth buildings for several hundreds of years. Due to the embedment nature, the joint has a certain degree of flexibility, allowing the floor and roof beams to slide without damaging the rammed earth, enabling dissipating energy during earthquakes. The energy dissipation mechanism of rammed earth-timber joint has not yet been fully understood. This study studied the energy dissipation characteristic of eight rammed earth-timber joint specimens via cyclic pull-out/push-in experiments, investigating the effects of compressive loading, embedment length, and surface roughness on joint performance. Results show that the joint stiffness under cyclic loading was reduced nonlinearly with the increase of pull-out displacement until the occurrence of slippage. The high vertical compression from the upper level, the deformability of timber frames, and the plasticity of rammed earth were found to be the primary energy dissipators. A linear frictional and nonlinear geotechnical hysteretic model, combining frictional and soil mechanics theories, was established to represent the joint behavior. In addition, a simplified multi-linear hysteretic model was developed for the same purpose. The predictions and the measurements had good agreement, suggesting that geotechnical methods should be employed to analyze the joint, maintaining the assumption that both the timber frame and the rammed earth are linear-elastic. • Energy dissipation of rammed earth-timber joint was investigated experimentally. • Effects of compressive loading, embedment length, and surface roughness on joint performance were studied. • Stiffness of rammed earth-timber joint under cyclic loading was reduced nonlinearly until slippage. • Vertical compression, deformability of timber frames, and rammed earth plasticity were the primary energy dissipators. • Two hysteretic models were established to represent the behavior of rammed earth-timber joint. [ABSTRACT FROM AUTHOR]

Broken prestressing wires in prestressed concrete cylinder pipe (PCCP) can cause incident of pipe burst. A method was proposed to repair damaged PCCP with broken wires by externally bonding carbon fiber reinforced polymer (CFRP). A finite element model was established and calibrated against the data from a prototype-scale laboratory test. Upon calibration, a three-dimensional numerical model was built to simulate the response of PCCP pipeline with five segments. Multi-field coupling was accomplished by Mesh-based parallel Code Coupling Interface (MpCCI) to incorporate the soil–pipe interaction and the effect of hydrodynamic pressure for PCCP. The effect of externally bonded CFRP to repair PCCP with broken wires was systematically analyzed. Results show that at a certain number of broken wires, the use of CFRP for pipe repair can significantly reduce the strains for each pipe component and increase the resilience of PCCP. The improved PCCP performance was assessed on the basis of crack visibility in the concrete core, and the deformation of the steel cylinder. The CFRP strain was much less than its ultimate strain, when cracks in the concrete core became visible and the steel cylinder yielded, suggesting that failure of PCCP could be ahead of CFRP. • A full-scale test is conducted on a PCCP under internal pressure. • A new technique to simulate the behavior of PCCP is realized through MpCCI. • Yield occurs in the steel cylinder of PCCP without repair work when 89 wires are broken. • The bearing capacity of PCCP can be improved by at least 13.3% a CFRP sheet with a thickness of 1.336 mm is wrapped. [ABSTRACT FROM AUTHOR]