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This paper conducts a comparative study into the hydrodynamic loads and bearing reaction forces between T-deck and box-deck bridges under freak waves. Initially, a high-fidelity numerical flume is established and validated to accurately simulate the freak wave-bridge interaction. Subsequently, a comprehensive analysis distinguishes the hydrodynamic characteristics associated with equivalent-sized freak waves, Stokes fifth-order waves, and solitary waves. Utilizing the developed numerical flume, the detailed comparisons of hydrodynamic loads on T-deck and box-deck bridges under freak waves are conducted, considering various focus locations, wave height to significant wave height ratios (α 2), and wave crest to wave height ratios (α 3). The study then delves into the seaward and landward bearing reactions for both bridge types. Additionally, the ultimate resistance envelope for a tension-compression bearing is explored through a finite element model, and the safety evaluation of the bearings under freak waves is carried out. Key findings reveal that (a) freak waves pose a more significant threat to structures than the other two wave types; (b) strengthening the seaward bearing for the box-deck and the landward bearing for the T-deck is recommended in the bridge design under the impact of freak waves; and (c) the ultimate resistance capacity envelope efficiently evaluates the bearing capacity when encountering freak waves with the working conditions used in this paper. • The force induced by freak wave, Stokes-5th order wave, and solitary wave is compared. • Hydrodynamic distinctions between T-deck and box-deck under freak waves is examined. • The bearing reaction force under varying parameters of freak waves is analyzed. • An ultimate resistance envelope is obtained for a tension-compression bearing. [ABSTRACT FROM AUTHOR]

Cylindrical shells with corrugation are widely used in deep sea, underground pressure structures, and other fields. It is mainly subjected to uniform and concentrated external pressure. The current research mainly includes circumferentially corrugated shells and longitudinally corrugated shells. These two kinds of corrugations improve the strength of the cylindrical shell but also have some problems such as stress concentration, buckling extension, and so on. To solve these problems, a shell with composite corrugation is proposed and it has the structural characteristics of both circumferential and longitudinal corrugations. In this paper, the numerical analysis method is used to explore the stability of the composite corrugated shell under uniform and concentrated pressures. It is analyzed by Donnell's large deflection equation. In addition, it can reduce the area of damage caused by buckling. The excellent mechanical properties of the composite corrugated shell are proven. The influence of the number of corrugations and "diameter to thickness ratio" on the buckling performance is studied by using the control variate method. It is compared with a cylindrical shell without corrugation with equal volume and weight. The concentrated pressure tests of composite corrugated shells and shells without corrugation are finished. The results show that the curve of "radial compression-reaction load" obtained by the experiment is consistent with the simulation. The ultimate load of the composite corrugated shell is 34.96% higher than the shell without corrugation. The composite corrugation can effectively enhance the compressive strength and stiffness of the cylindrical shell. Composite corrugation can make more material of the shell to be involved in resisting external deformation. This method of increasing material utilization is effective. • The advantages of the composite corrugated shell are verified from mechanical theory, finite element analysis and test. • The influence of local curvature on the buckling performance of cylindrical shell is verified. • Donnell's large deflection equation has been applied and innovated in this paper. [ABSTRACT FROM AUTHOR]

As basic units of oil tankers and bulk carriers, corrugated bulkheads are usually subjected to lateral loads such as liquid cargo pressure. In this paper, the experiments have been designed and carried out to investigate the collapse modes and ultimate strength of corrugated bulkheads and plane bulkheads under lateral pressure. In the experiment, pure air pressure was used to apply uniformly distributed lateral pressure. The results show that ultimate capacity of corrugated bulkhead is significantly larger than that of traditional T-shaped stiffened plane bulkhead under the same weight of materials. The corrugated bulkhead reaches the ultimate limit state after three plastic hinges formed on the corrugation, and experimental results agree well with the nonlinear finite element analysis. In addition, through numerical analysis, it is found that the boundary conditions considered in this paper have little effect on the ultimate strength of corrugated bulkheads when in-plane displacements are restrained, and the stress and displacement distributions of the mid-span corrugation are similar with five bays of corrugations and above, and can well reflect the corrugated bulkheads in real ships. The results of this paper are helpful to understand the mechanism of corrugated bulkheads collapse and provide references for ultimate strength experimental designs of corrugated bulkhead structures. • Experiments have been designed and carried out for both corrugated and plane bulkhead structures under lateral pressure, by using the test method of pure air pressure loading without any intermediate medium between the tank and the air. This experimental setup can be further extended to such experiments with combined axial and lateral loads. •Numerical analyses are carried out, and both the ultimate strengths and collapse modes match well with the experiments. Collapse behavior has been carefully discussed based on experimental and numerical results. • The design advantages of the corrugated bulkhead are verified by the comparative experimental and numerical analysis of the corrugated bulkhead and the plane T-shaped stiffened plate bulkhead. • The elastic behavior, inelastic behavior and ultimate limit state of corrugated bulkhead under lateral pressure are obtained by comprehensive experimental test and finite element analysis. Also, it has reference value for the evaluation of the ultimate capacity of the corrugated bulkhead model in the actual ship. • The collapse mode of corrugated bulkheads has similarity with that of fixed/simply supported beams at both ends. It is found that when three plastic hinges are generated in middle and ends of the center corrugation, the corrugated bulkhead has reached ultimate limit state. • The results by NFEM show that the discrepancy on the ultimate pressure of corrugated bulkhead under clamped and simply supported boundary conditions is small only when the in-plane displacement is fully restrained at the boundaries, and the clamped supported boundary conditions have better robustness and matches well with the experimental results. • It is found that when the number of corrugations is small (e.g., three in this study), the distribution of stress and displacements of the central corrugations changes obviously compared with original case, indicating that it is greatly affected by boundary constraints. [ABSTRACT FROM AUTHOR]

Feeding is a crucial issue during the aquaculture process. The feed delivery method determines the efficiency of aquaculture on the one hand and the degree of environmental pollution of the aquaculture process on the other hand. A good fish feed delivery method helps increase fish feeding rate, reduce the waste of fish feed and reduce the pollution of the aquaculture environment, which is beneficial to the sustainable development of aquaculture. This paper establishes a numerical model based on the CFD method. The model uses DPM to simulate the diffusion and distribution behavior of particles in still water condition, current condition and wave-current coupling condition, and design the particle diffusion experiment for validation. However, only through the feed diffusion area and feed leakage situation obtained by numerical calculation cannot accurately analyze and compare the feed diffusion effect. Therefore, this paper proposes a method to quantitatively evaluate the feed diffusion effect and verify its reliability. The quantitative evaluation method is based on the finite element method and the weighted average method, considering the factors affecting the diffusion and distribution of feed and the eating habits of aquaculture fish. The method can comprehensively and intuitively judge the diffusion effect of feed. The quantitative evaluation results can help to select a feed delivery method with better feed diffusion and adjust the feed delivery method correctly when the aquaculture sea condition changes. • The diffusion law of particles under the condition of still water, current and wave-current coupling is described. • The accuracy of the DPM simulation of particle diffusion was verified by comparison with particle diffusion experiments. • The results of quantitative evaluation methods can reliably reflect the diffusion effect of feed inside the cages. • The diffusion effect law of feeds under different sea conditions and different feed delivery methods is described. [ABSTRACT FROM AUTHOR]

Ship vibration not only causes safety issues, but also easily generates noise pollution. Therefore, this paper introduces the quasi-zero stiffness (QZS) vibration isolator to solve the problem of low-frequency vibration. In terms of static analysis, this paper proposes a discretized beam constraint model (DBCM) to study the static properties of flexible beams with large deformation, and the finite element analysis (FEA) verifies the accuracy of DBCM. Regarding dynamic analysis, this paper combines the harmonic balance method (HBM) and the pseudo-arc length method (PALM) to analyze the dynamic response and explore the influence of excitation and damping ratio on the response stability. In addition, the performance of equivalent linear isolators is compared, revealing significant advantages of QZS isolator in terms of isolation bandwidth and peak transmissibility. The experimental data demonstrates that QZS isolator's initial isolation frequency (2.14 Hz) is 68.5% lower than that of linear isolators (6.79 Hz), and the isolation efficiency at 5.35 Hz can reach 90%, making it suitable for low-frequency isolation. Furthermore, experimental data validate the accuracy of the theoretical model and FEA. The static and dynamic theoretical models can optimize the structural parameters of flexible beams and serve as valuable inspiration and reference for designing and improving isolator. • The QZS isolator is composed of eight flexible beams and a linear spring. • DBCM can accurately calculate the nonlinear statics of flexible beams. • The QZS isolator has a wider isolation frequency band and lower transmissibility. [ABSTRACT FROM AUTHOR]

This paper reports the effect of padeye offset ratio on the keying behaviours and capacity of square plate anchors in clay. The investigation is conducted through three-dimensional large deformation finite element analyses using the Remeshing and Interpolation Technique with Small Strain in ABAQUS. Strain rate dependency of the undrained shear strength and soil remoulding are accounted for adopting an extended Tresca model. The results from LDFE analyses are compared with existing analytical solutions, centrifuge test data, and numerical results; with reasonable agreement obtained. Parametric analyses are then carried out varying several critical factors including initial embedment depth, load eccentricity, padeye offset ratio, soil sensitivity, and soil strength heterogeneity. It is seen that the padeye offset has significant influence on the ultimate loss of embedment and capacity under vertical loading. To assess the keying behaviour of square plate anchors in clay, an equivalent soil strength incorporating strain rate dependency and remoulding is adopted. A combined factor defined as a function of the initial embedment depth and equivalent soil strength is used to estimate the ultimate loss of embedment. An equivalent ultimate bearing capacity factor is shown to be a function of the initial embedment depth, padeye offset ratio, and load eccentricity. • The keying behaviour of square plate anchors with padeye offset in NC clay is investigated by 3D LDFE analysis. • The effects of strain softening and strain rate are considered during keying process of square plate anchors. • The ultimate bearing capacity factor is a function of the initial embedment depth, padeye offset ratio and load eccentricity. [ABSTRACT FROM AUTHOR]

The vertical uplifting response of suction caisson plays a pivotal role in the ability of the jacket foundation to resist the large moment. Although the macro element model, which encapsulates generalized load and displacement relationships in a unified element, is widely utilized to simulate foundation responses, a macro element model tailored for suction caissons considering project-specific foundation geometries and site-specific soil stress-strain curves is currently underdeveloped. This paper addresses this gap by constructing a macro element model for the uplift response of suction caisson. This goal is achieved by deriving the macro element model via up-scaling soil stress-strain relations. Firstly, finite element analyses (FEA), with a verified undrained hyperbolic soil model, are adopted to obtain macro responses of the uplifting suction caisson in undrained clays. Subsequently, using the same hyperbolic hardening relationship and associated flow rules as the constitutive model of soils, an elasto-plastic macro element model for suction caisson subjected to uplift loads is established. The macro model is then calibrated against the computed caisson responses from FEA, leading to the establishment of a scaling law between the parameters of the macro element model and that of the soil constitutive model. Finally, the constructed macro element model undergoes validation against numerical results and centrifuge test outcomes. The assessment affirms that the proposed macro element model, developed via the up-scaling strategy, can effectively represent test responses and serve as a practical alternative to advanced FEA solutions, providing an efficient and reliable design procedure. • Macro-element (ME) model of vertically loaded suction caisson is investigated. • ME model is established via up-scaling soil stress-strain relations. • Project-specific soil properties and foundation geometries are considered. • ME model serves as a practical alternative to FEA solutions. [ABSTRACT FROM AUTHOR]

The monopile-bucket composite foundation is an innovative offshore wind turbines (OWTs) foundation type for its good bearing properties. This paper establishes the 3D finite element models to explore the lateral bearing behaviors for the composite foundations in sand-overlaying-clay deposits. After model verification, the failure mechanisms of the monopile foundations, single suction bucket and monopile-bucket composite foundations are systematacially analyzed. In addition, a detailed parametric study is undertaken to quantify the effects of potential parameters on the lateral bearing behaviors of composite foundation. Finally, the load sharing ratio between the monopile and suction bucket in composite foundation under lateral loading is investigated. It is found that the composite foundation is superior to that of single pile. Increasing the bucket diameter, bucket length, and overlaying sand layer thickness, the bearing capacity of composite foundation can be enhanced. Among them, the variation of bucket diameter has the most significant effect, while raising the loading point height will weaken the lateral resistance. When the dimensionless pre-vertical load increases from 0 to 0.7, the foundation bearing capacity is improved, and more than 0.7 leads to weakening. • Through numerical simulations, the bearing behaviors for the composite foundation in sand-overlaying-clay deposits under lateral loadings are investigated. • A detailed parametric study is undertaken to quantify the effects of potential parameters on the lateral bearing behaviors for the composite foundations. • The load sharing ratio between the monopile and suction under lateral loading is investigated. [ABSTRACT FROM AUTHOR]

Polyamide 6 fiber ropes are of interest for floating offshore wind turbine mooring lines but could exhibit complex mechanical behavior during loading at sea, such as creep, relaxation, variable dynamic stiffness or visco-plasticity. There is a need for a model that could be introduced into finite element analyses to predict this complex response; it should also describe the effect of the loading history. This paper presents a visco-elasto-plastic behavior model based on four dashpot-ratchet-spring elements that allow a precise description of polyamide 6 rope behavior. An identification method, using a multi-relaxation test, is described. It has been implemented in a finite element analysis software and validations are made by comparing the model results to the experimental data. The present work is the result of an extensive effort initiated by the collaborative research project POLYAMOOR and continued by the MONAMOOR project, both led by France Energies Marines. • An elasto-visco-plastic behavior model that allows a precise description of polyamide 6 rope behavior. • A complete characterization of the mechanical behavior of synthetic ropes. • Proposition of a complete identification method using a multi-relaxation test. • First identification and validation on a reduced laboratory scale polyamide 6 sub-rope. [ABSTRACT FROM AUTHOR]

This paper presents an innovative deep-learning network underpinned by advanced data-fusion techniques developed explicitly for detecting structural damage in marine platforms. This study commences with a rigorous validation of the proposed methodology employing detailed experimental procedures and subsequently applies this method to identify damage under specific random load conditions utilizing state-of-the-art finite element analysis software. This entails the meticulous construction of an extensive database mirroring the real-life conditions encountered by a deep-water jacket platform in the South China Sea. By conducting thorough simulations based on the characteristic environmental loads of this marine area, the study succeeds in closely replicating real-world conditions. The developed damage-identification model, which is specifically adapted to the distinctive requirements of non-Gaussian white-noise loads, exhibits notable accuracy. The experimental outcomes derived from the application of the proposed deep-learning algorithm for data fusion indicate an impressive accuracy rate of 92.01%. In simulated scenarios involving complexly loaded jacket platforms, the model attains an accuracy of 88.25%, highlighting the robustness of the method and its wide applicability in the field of marine structural health monitoring. • Instead of a single sensor, use multiple sensors for data fusion as inputs. • Simulation of complex wind, wave and current loads in real sea locations. • Comparison of the effect of accuracy between white noise loads and complex loads. [ABSTRACT FROM AUTHOR]

In recent years, steel truss structures have been widely used in civil engineering and wind turbines. In addition to bearing vertical loads, they are also vulnerable to impact accidental loads. If the foundation structure undergoes large deformation, it will lead to the overall instability and collapse of the structure. In this paper, the impact load resistance of steel truss foundation of wind turbine under eccentric mass is taken as the research object, and the combination of pendulum impact test and finite element simulation is adopted. The impact resistance of steel truss foundation was analyzed from the parameters of failure characteristics, impact response and energy dissipation capacity through multiple pendulum impact tests. The results show that after two impacts the stiffness of the impact leg is significantly reduced and even fracture at its root. The branch tube near the point of impact are squeezed and bent, and the deformation and acceleration peak of the impact position are the largest. The denting of the impact leg is the main energy dissipation mechanism. These data provide an experimental basis for improving the impact resistance of full-scale wind turbine structures. • Pendulum impact test study on steel truss foundation under eccentric load. • The impact leg extrusion is nearly flat, and the branch tube joint is deformed in an "S" shape. • Proposed numerical simulation method for multiple pendulum impacts at different intervals. • The influence of different parameters on the impact resistance of steel truss is obtained. [ABSTRACT FROM AUTHOR]

Ships and offshore structures operating in ice-covered waters need to be able to break ice. The hulls of ships and offshore structures are often designed to be inclined so that an out-of-plane force can be incurred to initiate flexural failure. During this process, an in-plane force co-exists as the result of the hull inclination, which can affect the bending process and alter the magnitude of interaction force. Additionally, the loading process can be rapid and incur dynamic effect within the ice sheet, resulting in higher peak loads compared to the scenario of quasi-static loading. The effect of in-plane force and loading speed, however, are often neglected in the modelling of the icebreaking process in order to enable simplified solutions of analytical form, which leads to deviations in the estimation of ice loads. This paper aims to investigate the effects of in-plane force and loading speed on the ice bearing capacity during the icebreaking process. This is conducted via the Finite Element Analysis (FEA) with the Cohesive Element Method (CEM). An anisotropic beam analogy concept is proposed to model a 3D ice wedge with a 2D beam which has varying properties along the axial direction. The analogy enables fast and stable simulation of ice crack propagation through its thickness direction, while maintaining properties of the ice wedge in 3D. The analogy is verified with Nevel's closed-form solution for a narrow wedge resting on an elastic foundation. After that, the beam is loaded with a rigid wall with different inclination angles and loading speeds. The results reveal that the in-plane force and loading speed have significant influence on the icebreaking process, resulting in different bearing capacity and overall energy consumption. Based on the numerical results, a regression study is conducted to derive a correction coefficient accounting for the joint effect of in-plane force and loading speed on the bearing capacity, which can be incorporated into ice-structure interaction simulation models. • An anisotropic beam analogy is proposed to model 3D ice wedge with 2D beam to investigate ice wedge bearing capacity. • The joint effect of the in-plane force and the loading speed on the bearing capacity of the ice wedge is investigated. • A strong coupling effect between the in-plane force and the loading speed exists, which jointly affect the bearing capacity. • A regression formula is obtained to account for the joint effect of in-plane force and loading speed on bearing capacity. [ABSTRACT FROM AUTHOR]

In naval engineering, protecting sensitive articles from shock loads is a major concern, as it may lead to adverse consequences. This paper focuses on the design of a novel Hydrogenated Nitrile Butadiene Rubber (HNBR) and Polychloroprene Rubber (PCR)-based shock isolation system to protect a sensitive article stored in a hollow cylindrical naval vessel container (NVC). Firstly, NVC is modeled as a two-degree-of-freedom lumped parameter model (LPM), wherein isolators made of HNBR and PCR materials are modeled with 5-order polynomial nonlinear stiffness and linear damping. The optimal values of the isolator parameters are obtained using a multi-objective genetic algorithm, and corresponding responses to a shock load are found using MATLAB. Furthermore, a three-dimensional (3D) finite element model (FEM) of the NVC is generated in ABAQUS and subjected to shock loading in a transverse direction to conduct a comprehensive dynamic analysis of the isolation system. In 3D simulation, HNBR and PCR materials are modeled using a hyper-viscoelastic model developed based on experimental test data. The 3D simulation results of the NVC for the optimized design of HNBR and PCR isolators agree with the optimized results of the LPM. Moreover, the proposed HNBR and PCR isolators are very effective in shock reduction. • Optimum design of HNBR and PCR shock isolators for a naval vessel container. • Analytical modeling of rubbers takes into account nonlinearity up to the 5th order. • The multi-objective genetic algorithm is used for optimization of the analytical model. • A hyper-viscoelastic model defined the material properties of rubbers in the 3D FEM. • In the FEM, the optimal number of isolators is decided based on two variables' trade-offs. [ABSTRACT FROM AUTHOR]

This study employed numerical analysis to compare the seismic performance of different types of offshore wind turbine foundations: pentapod suction bucket, monopile, and pile jacket foundation. The finite element model of these foundations was modeled by Abaqus and was then verified by modal analysis. GH-Blade was used to create the wind field and eventually generated the thrust force by the wind which was then fed into the Abaqus. First, three earthquake records, i.e. El-Centro, Taft, and Topanga, were used to investigate the dynamic response of these OWTs. Then, a set of 16 earthquake records was used in fragility analysis. Under the combination of these earthquake loads and wind, the dynamic responses were obtained and then converted to the fragility curves to evaluate the probability of exceeding different damage states. The results show that OWT supported by monopile foundation (MP-OWT) has the largest top displacement. Despite occurring almost in the same position, the maximum stress on the tower of OWT supported by pile jacket foundation (J-OWT) is larger about 17.7% and 21.3% than that of OWT supported by suction bucket foundation (SB-OWT) and MP-OWT, respectively. The analysis also indicated that MP-OWT has a high risk in terms of tower-top displacement compared to the others while J-OWT was the most sensitive in terms of tower-base moment and tower stress. The paper provided an overview of the seismic response of different OWT foundations, thereby helping in seismic design for wind turbines. • Three-dimensional finite element analysis was conducted to predict the dynamic response of OWTs. • Seismic responses of OWTs supported by different foundation types were compared. • The probability of exceeding several damaged states within the OWT system was investigated. [ABSTRACT FROM AUTHOR]

In this paper, a vertically held thin elastic plate subjected to viscous fluid flow and undergoing flow-induced deformation is examined. Two-dimensional numerical simulations are carried out at low Reynolds number, Re = 100. The simulations are performed using an in-house fluid structure interaction code that combines the sharp-interface immersed boundary (IB) fluid solver with the finite-element method structural solver. The fluid solver and the structural solver are being coupled using the partitioned approach. The system's dynamic behaviour is investigated by considering the effect of parameters such as mass ratio (M) and bending rigidity (K b). When the plate undergoes deformation, the amplitude and frequency response for different reduced velocity (Ur) are obtained. We observe six distinct regions. The first is Low Amplitude region (LA) ( U r = 0 t o 1.0) , second is Initial branch (IB) (U r = 1.0 t o 2.5) , the third is Intermediate region (I) (U r = 2.5 t o 3.0) , the fourth is Upper Branch (UB) (U r = 3.0 t o 4.6) , the fifth is Bi-stable region (BS) (U r = 4.6 t o 6.0) and finally we have Lower Branch (LB) (U r = 6.0 t o 8.0). Further we observe synchronization of vortex shedding frequency (f v) with structural frequency (f s) at U r = 3.0 with first mode of natural frequency (f n 1) being the dominant frequency. In order to understand the dynamics of flow-induced deformation of vertical mounted elastic plates in viscous fluid flow we have analysed the amplitude, frequency and displacement response of structure and corresponding behavior of the fluid owing to the complexity of computationally modelling such interactions. An Artificial Neural Network machine learning model is also used to predict the plate oscillation frequency. The study further emphasizes the importance of using machine learning based prediction models to reduce computational expense. • Flow-induced deformation of vertically mounted plate at Re = 100. • Dominance of first mode plate vibration at low flow speeds. • Amplitude and Frequency response of plate ascertained for different plate bending rigidities. • Artificial neural network-based prediction model development for plate oscillation frequency. [ABSTRACT FROM AUTHOR]

Existing shafting alignment methods ignore the inherent uncertainties of the system when modelling and inputting variables. The calculated results and the working conditions differ. Therefore, this study establishes a shafting dynamic alignment model under uncertainty using the stochastic finite element, which combines the finite element method with Latin hypercube sampling. Bearing elevations and material parameters were used as random input variables. Bearing load and cross-section bending angle were used as evaluation indicators. The shafting operational reliability was calculated for linear, rational, traditional dynamic alignment and uncertainty dynamic alignments. The results show that only the uncertainty dynamic alignment satisfies the requirements. An experiment was conducted to simulate the hull deformation by continuously changing the bearing elevation. The bearing load and axis orbit were collected and analyzed for the four alignment states. According to the linear alignment, the deviations between the experimental and theoretical results for the aft stern, front stern, and intermediate bearings loads are 0.07 %, 15.26 %, and 5.12 %, respectively. Hence, the alignment model satisfied the requirements for accuracy. Furthermore, the uncertainty dynamic alignment as the shafting's optimal state can be determined by analyzing the axis orbit in different states. Therefore, considering the uncertainty, a shafting dynamic alignment is necessary. • This paper proposes a dynamic alignment calculation method based on Latin hypercube stochastic finite elements. • Incorporation of uncertainty due to dynamics into calculations in the form of probability distributions. • Stochastic simulation calculations were performed for three states: linear, rational, and dynamic alignment. • A sensitivity analysis was conducted to determine the impact of uncertainty in the random variables on the output response. • The model's validity is confirmed through experimental results of bearing loads and axis orbit. [ABSTRACT FROM AUTHOR]

The utilization of renewable energy is an important way to solve the energy crisis, and wind power is one of the most mature new energy technologies. This paper studies the potential of applying the viscoelastic damper to mitigate vibrations of the OWT tower under wind-wave loadings. The viscoelastic damper directly converts the horizontal deformation of the tower into the shear deformation of the viscoelastic material for energy dissipation, which provides a new idea for suppressing the dynamic response of the OWT. According to OWT structural dynamic characteristics and load conditions, a new high damping wall-type viscoelastic damper (HVED) control is developed. The mechanical properties of HVED are investigated by full scale test. A numerical vibration response analysis of the controlled and uncontrolled 4 MW OWT was carried out in ANSYS. Results indicate that the HVED can significantly reduce the dynamic response of OWT and increase its fatigue life. • A new high damping viscoelastic damper (HVED) is proposed to mitigate the vibration of OWT. • Advantages of HVED are significant energy dissipation, wide-frequency control, and convenient installation. • Full scale test was conducted to verify the mechanical properties of HVED. • Interaction of soil and structure (SSI) was considered in the finite element analysis. [ABSTRACT FROM AUTHOR]

The cavitation phenomenon caused by near-field underwater explosion imposes a secondary loading on ship structures. Studying the cavitation effects of plates during underwater explosions has implications for ship protection since plate is a typical structure of ships. This paper experimentally investigated the behavior of fixed square plates subjected to near-field underwater explosions. Experimental results indicated that cavitation existed in both shockwave and bubble pulsation stages; and the cavitation closure load at bubble pulsation stage was measured. To further investigate the cavitation phenomenon and the load characteristics at the bubble pulsation stage, finite element models were developed. The numerical results show that cavitation will increase the bubble load impulse by 47 % under specific conditions. These models were then used to investigate the influence of the stand-off distance and charge weight on cavitation area and load characteristics. An empirical formula was finally proposed to predict the coupled impulse of cavitation closure, bubble pulsation and water jet. This research has practical guidelines for the protection design of ship structures. • The wall pressure-time history curves of cavitation closure were obtained. • The cavitation closure load was accurately simulated by the CEL method. • The effect of the stand-off distance and charge weight on cavitation area and load characteristics. • An empirical formula was proposed to predict the coupled impulse of the cavitation closure and bubble jet load. [ABSTRACT FROM AUTHOR]

Virtual-real Fusion is a technology that enables rapid integration of physical information and decision-making through visualization and interaction. By combining with the field of ship structure design, this technology is applied to improve the competitiveness of enterprises. In this paper, a method of virtual-real interaction and symbiosis between engineering analysis and physical scenarios is proposed, aiming to enhance the design and evaluation of hull structures. Initially, the establishment of a high-fidelity digital twin model is ensured to be consistent with the physical scene, paired with a collision detection mechanism consistent with the physical scene, which plays a key role in the correlation of loads and boundary conditions for subsequent real-time numerical simulations. Secondly, measured data from physical sensors are used to drive virtual scenes to ensure that computers understand and reproduce specific physical phenomena. Subsequently, the real-time numerical simulation data is filtered and transformed. At the same time, engineers can explore finite element analysis results on-site through virtual reality visualization technology to track the mechanical interactions between physical components, thereby reducing spatial and logical misunderstandings and enabling collaboration with other departments. Finally, a prototype system with basic functions is developed. A case study focusing on mechanical experiment of ship structures is carried out, which demonstrates the practicability of the proposed method. • Acquire load data from the real environment and simulate deformation and stress of the structure in real time. • Carry out analysis and model modification of virtual reality-assisted interaction. • Configure a physical sensor network for real-time acquisition of virtual-reality fusion field data. • Enable real-time interaction and decision-making between virtual and physical objects. [ABSTRACT FROM AUTHOR]

Double carcass floating hoses (DCFHs) are extensively utilized in offshore oil and gas transportation, with the outer carcass serving as an effective means to minimize or entirely prevent leakage of conveyed fluid. This study employs a combined approach involving numerical simulation and full-scale burst experiments to investigate the mechanical-structural behavior and failure mechanisms of DCFHs with inner diameter of 600 mm subjected to internal pressure and tension. By using rebar elements and embedded element method, a nonlinear large-deformation finite element model for DCFHs under internal pressure and tensile loads was established. The accuracy and effectiveness of the finite element analysis is validated against full-scale experimental results. Python programming language is employed to create the script used in the parametric modeling of DCFHs with ABAQUS software. The impact of varying parameters such as inner diameter, helix steel wire pitch, number of cord layers beneath the helix steel wire, and winding angles were analyzed for DCFHs under burst pressure. Based on the classical thick-walled cylinder ultimate internal pressure theory, a fitting formula for predicting the burst pressure of DCFHs is proposed. This paper provides valuable insights in the structural design and application of DCFHs under ultimate internal pressure loads. • Bursting failure mechanisms of DCFHs have been investigated by experiments and numerical simulations. • Investigations into two bursting failure modes are conducted with varying parameters of DCFHs. • The bursting pressure of DCFHs was studied using a Python-based parametric model with varying parameters. • A burst pressure prediction formula for DCFHs was proposed. [ABSTRACT FROM AUTHOR]

During service, local damages in towering structures can induce structural stiffness degradation, which may lead to changes in structural dynamic characteristics, such as natural frequency. Thus, the control effect of the linear TMD with a narrow frequency band may decrease in the lifetime service. This paper proposes a novel hysteretic nonlinear shape memory alloy TMD (HNSMA-TMD) using the superelastic effect of the SMA and prestress method to improve the TMD's control effect when considering structural stiffness degradation. Firstly, the configuration and working principle of the proposed HNSMA-TMD is introduced. SMA's excellent superelastic performance can provide the hysteresis force for the HNSMA-TMD and broaden the control frequency bandwidth of HNSMA-TMDs. The mechanical model and finite element model (FEM) of the HNSMA-TMD are developed. Finally, a design method of the HNSMA-TMD is proposed, and the vibration responses of the offshore wind turbines without TMD, with TMD and with HNSMA-TMD under wind-wave loads are compared, considering structural stiffness degradation. Results show that the root mean square response reduction ratio of the wind turbine with HNSMA-TMD remains nearly 25% when considering 20% stiffness degradation. In comparison, the ratio of the wind turbine with TMD reduces from 36.3% to 6.4%. • A novel hysteretic nonlinear shape memory alloy TMD is proposed. • The mechanical model and FEM of the HNSMA-TMD are developed. • A design method of the HNSMA-TMD is proposed. • The vibration response of the OWT with HNSMA-TMD is studied. [ABSTRACT FROM AUTHOR]

Monopiles are the most common Offshore Wind Turbine (OWT) foundations due to their simplicity in design, fabrication, and installation. However, large new-generation turbines have led to significant changes in monopile dimensions, necessitating extensive finite element analyses and ground investigations to meet design requirements. While Cone Penetration Test (CPT)-based p - y methods can analyse slender pile lateral behaviour, they often miss additional resistance mechanisms relevant to rigid monopiles. This paper introduces CPT-informed resistance mechanisms for monopiles to incorporate additional lateral resistances beyond p - y modelling capabilities. Distributed moment–rotation (m - θ) springs are defined by repurposing CPT-based axial capacity estimation methods for piles; and pile tip shear and moment springs are informed by approximating a residual bearing stress post-installation using local CPT q c values. The performance of the multi-spring model is appraised against data reported from monotonic pile pushover tests conducted at two sand sites. Results show that the multi-spring model is capable of predicting pile head deflections reasonably well within serviceability deflection limits against the reported test data, but ultimate failure loads cannot be predicted using the proposed model. A clear sensitivity in pile response to local variations in CPT q c is demonstrated. • CPT-informed springs modelling additional lateral resistance in monopiles developed. • Moment–rotation springs are informed using CPT-based axial capacity methods. • Pile tip shear/moment springs informed from post-installation stress CPT estimates. • Multi-spring model evaluated against lateral pile pushover tests in sand. • Good deflection prediction within SLS range, shows sensitivity to local CPT changes. [ABSTRACT FROM AUTHOR]

Sea-crossing bridges face complex site environments compared to onshore bridges, with the marine environment significantly influencing seismic responses. Despite this, current seismic design for these bridges relies on onshore earthquake records. Therefore, investigating the impact of seawater layers and site conditions on sea-crossing bridge seismic performance is crucial. This paper investigates the influence of characteristics of offshore ground motion, site conditions, and hydrodynamic effect on the seismic performance of piers. Initially, based on the validated finite element model, 5 offshore and onshore strong ground motion records from K-NET were selected for assessing the seismic performance of piers. Subsequently, the effects of the water depth and site conditions on the seismic responses of piers were investigated. Finally, the effects of the section size, section shape, and boundary conditions on the piers were investigated. The result shows that the seismic response of piers under offshore ground motion exceeds that under onshore ground motion. In addition, the seismic response of the pier increases with greater water depth, while they exhibit a slight decrease with increasing soil depth. Notably, the larger the section size, result in higher the hydrodynamic pressure, and square piers experience greater hydrodynamic pressure compared to circular piers. • The seismic performance of piers subjected to offshore ground motion is studied. • Finite element models considering seawater layer and site conditions are developed. • The seawater layer significantly amplifies the seismic response of piers. • The soil layer has a constraint effect on the response of piers. • The hydrodynamic effects of underwater piers are explored. [ABSTRACT FROM AUTHOR]

The paper studies the effect of soil strength and stiffness degradation on the undrained cyclic performance of offshore foundations in low-plasticity cohesive soil using 3D finite element modelling. Cyclic triaxial tests on reconstituted kaolin are conducted at the ETH Zurich laboratory, providing insights into key parameters affecting the degradation process. A simplified soil constitutive model accounting for cyclic degradation is developed and encoded in Abaqus via a user subroutine. The model is calibrated against experimental results and validated with published centrifuge model tests of monopiles under cyclic lateral loading. It is subsequently used to evaluate the performance of suction caisson foundations with different aspect ratios (L/D = 0.5 and 2) under short-term cyclic and seismic loading. Due to its ductile resistance mechanism, the L/D = 0.5 caisson exhibits superior performance under vertical cyclic loading in fast-degrading soil. Under inclined cyclic loading, the slower degradation rate of the L/D = 2 caisson governs response, reversing the trend. Under seismic shaking, the degradation-induced resistance imbalance amplifies the irrecoverable settlements produced by kinematic shearing at the caisson sidewalls. For the fast-degrading soil examined, degradation is shown to increase settlements by up to 50%. • Cyclic strength and stiffness degradation of cohesive soils is explored via undrained triaxial tests on kaolin samples. • A simplified total stress-based constitutive model is developed for capturing such effects. • The model is validated against published centrifuge tests of a monopile subjected to lateral cyclic loading. • The undrained behaviour of caissons under cyclic and seismic loading is assessed, considering cyclic degradation effects. • For the case of fast-degrading soil examined, soil degradation may increase foundation settlements by up to 50%. [ABSTRACT FROM AUTHOR]