The hydrodynamic performance of a barge-type floating offshore wind turbine (FOWT) with a moonpool is studied in frequency domain with reference to the Ideol-Floatgen design. The correction of the viscous damping of the moonpool is considered. First, the resonance modes of the moonpool are analyzed. Then, the hydrodynamic coefficients of the FOWT under regular waves and the motion responses under irregular waves are investigated. Finally, the safety of the FOWT is verified with respect to the DNV standards. The results show that the dynamic pitch and nacelle acceleration of the barge-type FOWT meet the safety requirements under both operating and survival conditions. The investigation of the coupling effects of the platform motion and the moonpool resonance shows that the motion of the platform will cause the shift of the piston mode frequency of the moonpool and the reduction of the piston mode response amplitude, the frequency of the sloshing mode is basically unaffected, but the response amplitude of the first-order sloshing mode is increased. The motion responses of the barge-type FOWT with and without the moonpool are compared. It is found that the moonpool can reduce the motion response of the FOWT, and improve the overall hydrodynamic performance of the FOWT. The platform length, moonpool length and platform draught are parametrically analyzed. Surge, heave, pitch response RMS values and the nacelle acceleration response RMS value are used as the indicators of comparison. It is found that the increase of the platform length could effectively reduce the four response RMS values of the FOWT under both operating and survival conditions, the increase of the moonpool length will reduce the four response RMS values of the FOWT under the operating condition, and the increase of the platform draught could significantly reduce the four response RMS values of the FOWT under the survival condition, the heave and pitch response RMS values increase with the augmentation of the draught under the operating condition.

Compared with fixed offshore wind turbines, the vibration problem of floating offshore wind turbines is particularly prominent, and further reduction of the vibration of floating offshore wind turbines has become an engineering challenge. In order to solve this problem, a novel vibration suppression device, inerter-based absorber (IBA) is introduced, and the vibration control of semi-submersible offshore wind turbines is studied. A comprehensive optimization method, namely the structure-immittance approach, is utilized to design the IBA in a systematic way. In order to search for the optimum vibration suppression performance, a simplified dynamic model of the semi-submersible offshore wind turbine, and the IBA dynamic equations are established using D’Alembert’s principle. Simultaneous suppression of the vibration response of the floating platform and tower of a semi-submersible offshore wind turbine is realized using the dual IBA control strategy. Furthermore, by implementing the optimum IBA in the OpenFAST software, the vibration suppression benefits of the dual IBA compared with the dual tuned mass damper (TMD) are verified under the coupling effects of wind and waves. The results show that the vibration control performance of the dual IBA control strategy is significantly better than that of the single one, and that of the dual IBA is better than that of the dual TMD. In addition, under the condition of achieving the same suppression performance as the TMD, IBA installed at the nacelle and the platform can respectively decrease the required absorber mass by 23.9% and 32.2%, which can greatly reduce the manufacture cost of the device.

The depth distribution characteristics of particle velocity field intensity have had a significant impact on underwater acoustic detection and estimation. In this paper, based on the approximate conditions of the incoherent normal modes sum transformation to angular integration, the angular integration form of incoherent normal modes of particle velocity was derived, which avoided the complex calculations of eigenvalues and eigenfunctions while revealing the physical mechanism behind the significant variations in particle velocity intensity with source depth and symmetrical depth. The numerical results demonstrate that the analytical expression of the angular integration of incoherent particle velocity can facilitate fast computation and effectively characterize the depth distribution characteristics of particle velocity intensity. Additionally, due to the superposition effect of the amplitude function of normal modes, there are notable differences in the depth distribution of vertical and horizontal particle velocity. Subsequently, focusing on the intensity difference of particle velocity, the study analyzed the effects of parameters such as horizontal distance, source frequency, sound speed profile, and water depth on the depth distribution characteristics of particle velocity field intensity. The findings provide a theoretical basis for passive target depth estimation based on vector fields.

A prediction method based on the information data of finite scattering acoustic pressure is proposed for the prediction of underwater spherical target multistatic acoustic scattering sound field, which represents the scattering sound field as the product of the acoustic scattering transfer function and the source density function, obtains the acoustic scattering transfer function by numerical integration with the model surface grid information as input, and acquires the source density function by combining acoustic reciprocity, least squares, and matrix transformation with small amount of known scattered sound pressure data as input. The multistatic scattering sound field prediction method is validated by using the Rayleigh normal mode solution and the finite element method (FEM) for double-layered spherical shells and spherical shell with the.pngfener. The target strength experiment is conducted for the spherical shell with the.pngfener, and the experiment results are compared with the finite element calculations. Several test data and FEM calculation results data are used as input to predict the multistatic scattering sound field of the spherical shell with.pngfener and compared with the FEM results, respectively. It is found that the simulation and test results are in good agreement, which verifies the feasibility of the prediction method.

In modern ship degaussing systems, degaussing windings are mainly distributed based on the shape of ship bulkhead, which is difficult to ensure the degaussing effect of magnetic induction intensity of unit winding of each degaussing winding. In order to solve this problem, this paper introduces a tilted correlation screening in high-dimensional variable filter, which splits and recombines the original coils, and re-divides the original degaussing sections, so as to improve the degaussing efficiency of each coil. Aiming at the problem of sparse parameter vectors and multiple collinearity in the calculation of degaussing current after winding restructuring, this paper proposes a slant correlation screening and partial ridge regression algorithm. Through simulation, when the threshold is 0.73 and 0.91, the algorithm reduces 10.08% and 17.59% respectively compared with the least square method, while the residual root mean square error decreases by 10.45% and 12.17%. The simulation results show that the degaussing effect is significantly improved after the algorithm is adopted.

Aimed at the problem of low efficiency of ship pipeline design, an optimization method of pipeline layout is proposed. An optimization mathematical model is established by comprehensively considering the engineering background of safety, economy, coordination and operability, and the defects of ant colony optimization algorithm in dealing with mixed pipeline layout conditions are improved. A spatial state transition strategy for optimizing feasible solution search, a pheromone diffusion mechanism for improving pheromone inspiration effect and accelerating algorithm convergence are proposed, and a multi-ant colony co-evolution mechanism is designed for mixed pipeline layout conditions. Based on the secondary development technology, the application of this method in the third-party design software is realized, and verified by a nuclear primary pipeline layout project. The results show that the pheromone Gaussian diffusion multi ant colony optimization (PG-MACO) algorithm has a better performance and layout effect than the traditional ant colony algorithm. The routing efficiency is improved by 58.38%, the convergence algebra is shortened by 43.24%, the pipeline length is shortened by 33.88%, and the number of pipeline bends is reduced by 41.67%, which verifies the effectiveness and engineering practicability of the proposed method.

It is a significant technical challenge to exploit deep-sea polymetallic nodules with high efficiency and low disturbance. The mechanical behavior of seabed nodule collecting is very complicated, which is a multi-physical coupling process involving three-dimensional turbulent flow, discrete particle movement, and fine particle soil failure. In this paper, three main deep-sea hydraulic nodule collecting methods, i.e., the suck-up-based method, the Coandă-effect-based method, and the double-jet hydraulic method, are investigated by numerical simulation on the performance of nodule collecting and environmental disturbance. The realizable K-Epsilon two-layer model and the discrete element method are used to simulate the turbulent flow of the liquid phase and nodule particles in the solid phase respectively. The effect of collection flow q_m and drag velocity v on collection rate η, turbulent kinetic energy k, and volume fraction φ of the seawater-sediment mixture in the collecting flow field is analyzed. The flow velocity, pressure, and nodule distribution are explored. The results indicate that, at the same q_m and v, the double-jet hydraulic model will achieve the largest η, while the suck-up-based model will achieve the least η. The double-jet hydraulic model has the most significant disturbance to the near-bottom flow field and the most obvious sediment spreading phenomenon. In contrast, the suck-up-based model and the Coandăeffect-based model have less environmental disturbance, which is more conducive to the requirements of environmental protection. The Coandă-effect-based model shows minor sensitivity to q_m and v and a good balance between high nodule collecting efficiency and low environmental disturbance. This paper will provide a scie.pngic basis for revealing the nodule collecting mechanism and designing and developing a nodule collecting device.

To evaluate the bearing capacity evolution of subsea shallow foundations during operation, an undrained shear strength distribution of clay seabed following full consolidation due to preloading was deduced. The characteristics method was used to derive the stress characteristics equation and to evaluate the consolidated bearing capacity of shallow foundations. The influence of preloading ratio, soil inhomogeneity, effective internal friction angle, and foundation dimension on the consolidated bearing capacity of shallow foundations was investigated. The result shows that the relationship between the relative gain in the consolidated bearing capacity of shallow foundations and the preloading ratio is approximately linear. Meanwhile, the relative gain in consolidated bearing capacity is jointly determined by soil inhomogeneity and effective internal friction angle and is not affected by the foundation dimension individually. The accuracy and effectiveness of the proposed method were verified by comparing it with the results of soil-water coupled finite element analysis. Finally, possible errors between the characteristics solution and finite element model (FEM) results were analyzed. It was found that the discrepancy in the pore pressure calculation was the main reason for the disparity in the prediction of consolidated bearing capacity obtained by two methods. This characteristics solution can quickly and accurately predict the growth of consolidated bearing capacity of shallow foundations, which provides important reference for the optimal design of subsea shallow foundations.

In order to predict the crashworthiness of.pngfened plate structures of ships under eccentric vertical quasi-static ballast of wedge, a new simplified analytical method is proposed in this paper. The plastic deformation area of the rectangular plate is divided into eight asymmetrical plates and the aggregate is divided into two asymmetrical parts. An linear mode is adopted in the deformation of rectangular plate and aggregate. From the perspective of the internal dynamics of ship collision, and based on the rigid-plastic theory, a simplified analytical method is deduced between the deformation damage resistance and lateral deformation of rectangular plate and aggregate under the eccentric vertical action of wedge impact, considering tensile and bending effects of the membrane. The proposed method is verified by the simulation results of nonlinear finite element software Abaqus. The results show that the proposed method has a high prediction accuracy, and can be used in the hull structure design stage to quickly predict the crashworthiness of the ship side structure.

Slurry diffusion is the key factor affecting the resistance reduction of pipe jacking grouting. Therefore, this paper establishes a three-dimensional numerical analysis model of pipe jacking, introduces a diffusion ring to simulate the slurry diffusion process during pipe jacking construction, modifies the friction coefficient according to the contact between the soil around the pipe and the segment, and studies the influence of the slurry diffusion process on the resistance reduction effect during pipe jacking construction. The calculated jacking friction is compared with the measured data to verify the reliability of the method proposed. The influence of the filtering effect on soil displacement and the influence of grouting diffusion-related parameters on soil displacement and jacking friction during pipe jacking construction are further studied. The results show that the surface subsidence is smaller when the filtration effect is considered; The stronger the attenuation of permeability coefficient caused by the filtration effect, the smaller the surface settlement and jacking friction resistance; The faster the slurry diffuses and the more complete the slurry jacket is, the better the resistance reduction effect of grouting during pipe jacking.

The horizontal vibration model of partially buried pile group under vertical load is established based on Biot saturated porous media theory, considering the flow characteristics of liquefied soil. Considering the pile-soil coupling and continuous displacement conditions, the pile interaction factor solutions and the horizontal dynamic pile impedance solutions in liquefied soil under complex conditions are obtained using the variable separation method and the operator decomposition method. Parameter studies are conducted on liquefied soil characteristics and vertical loadings. The results show that at the same vibration frequency, the horizontal dynamic.pngfness of pile group decreases with the increase of surface liquefied soil thickness. When the liquefaction thickness is large, the dynamic.pngfness decreases significantly with the increase of frequency, and a negative.pngfness appears. Vertical pile top loading can reduce the dynamic.pngfness of pile group in liquefaction soils. The weakening effect becomes more obvious with the increase in the thickness of liquefied soil.

In order to study the difference of dynamic response between large diameter variable section single pile and pile group foundations in seismic subsidence soil with different thicknesses under ground motion, based on the Xiang’an Bridge of Xiamen Second East Channel, a shaking table model test was conducted to study the difference of dynamic response of soil subsidence, horizontal displacement of pile top, acceleration of pile body and bending moment between single pile and pile group foundation when the thickness of seismic subsidence soil layer is 30, 40, and 50 cm. The results show that with the increase of the thickness of seismic subsidence layer, the seismic subsidence, horizontal displacement of pile top, acceleration and bending moment of single pile and pile group foundations increase gradually, and the acceleration and bending moment change abruptly at variable section. In the seismic subsidence layer with the same thickness, the seismic subsidence of soil around pile group foundation is larger than that of single pile, but the acceleration of pile group foundation, horizontal displacement of pile top and bending moment of pile body are smaller than those of single pile. It is suggested that in the design of pile foundation in seismic subsidence site, the difference of dynamic response between variable section single pile and pile group should be mainly considered to ensure the seismic performance of pile foundation.

The cavity expansion theory provides a theoretical basis for the displacement prediction of the installed piles and the analysis of pressuremeter test results. However, there is a lack of systematic analysis of the influences of soil structure in the existing solutions. In this paper, based on the Cemented-CASM considering the cementation effect, an elastoplastic solution for the cylindrical cavity expansion under undrained condition was presented by deriving the elastic-plastic.pngfness matrix reflecting the soil stress-strain relationship in combination with the hardening laws and larger-strain theory. To verify the validation of the present solution, it was compared with the solution in Modified Cam Clay soils when ignoring the soil structure and compared with the numerical results of pressuremeter tests when the soil structure was considered. Parametric analyses were conducted to illustrate the effects of soil structure and destructuration on the cavity expansion process. The results show that the effective stresses and pore water pressure caused by the cavity expansion in structured soils are larger than those in reconstituted soils, while the plastic range around the cavity becomes smaller due to the soil structure. With the damage of the structure, the soil exhibits a strain softening behavior, while the radial stress increases and then decreases as the distance from the cavity wall decreases. When the soil structure is completely destroyed, the effective stresses around the cavity are consistent with those in the reconstituted soils. As the soil structure strengthens, destructuration become faster under the same variation in cavity expansion pressure or cavity radius, and the strain softening behavior becomes more pronounced.

To better predict the lateral displacements of diaphragm walls during deep excavation, a long short-term memory (LSTM) multi-step prediction model is developed in this paper based on the LSTM algorithm. First, the multi-output strategy of multi-step prediction model is discussed. Then, the construction method of the LSTM multi-step prediction model is introduced in detail, and the two hyperparameters, i.e., the space and time dimensions of the model input set, are explored to improve the prediction accuracy of the model. Finally, the errors between the predicted values and the field monitoring data are analyzed based on an excavation project buried in water-rich sandy strata. The analysis results of three typical monitoring points indicate that the LSTM prediction model is characterized by solid generalization ability, and the relevant algorithm is practically helpful for improving and optimizing deformation prediction methods of deep excavation.

Existing studies on road network recovery decision have ignored the impact of the differences in recovery speed and recovery degree of different road sections on the recovery performance of the road network. To address this problem, road network connectivity index based on section impedance tolerance was first constructed to evaluate road network performance under partial recovery of road section capacity. Then, a bi-level optimization model for emergency recovery decisions was constructed with the weighted road network performance resilience and recovery speed resilience as optimization objectives. When the optimal set and recovery time sequence of the road sections to be repaired are determined, the recovery degree and speed of the road sections to be restored are obtained through resource allocation and budget allocation at the road section level. Finally, based on the traditional parallel machine scheduling problem genetic algorithm, a new encoding and decoding method was constructed to solve the upper model. The lower level model was solved based on the Frank-Wolfe algorithm. Based on the data of a regional expressway network in Guizhou Province, the above models and algorithms were verified and analyzed. The results show that under certain resource and budget constraints, considering the difference in road section recovery degree can improve the road network performance resilience by 32.62%. Considering the difference in road section recovery speed can improve the road network performance resilience by 10.17%. The sensitivity analysis shows that taking into consideration the difference in road section recovery speed can improve the marginal benefits of increasing the number of recovery resources for improving road network performance resilience, recovery speed resilience, and weighted resilience by 12.69%, 5.47%, and 22.93% respectively. Considering the difference in road section recovery degree helps balance the improvement of road network performance resilience and the reduction of recovery speed resilience caused by the increase of recovery budget, so as to ensure the road network recovery performance. Therefore, it is important to consider the recovery differences in different road sections for road network recovery decision.

It is a common problem that the glass panel falls due to the damage of silicone structural sealant used for the connection of the hidden frame glass curtain walls in the service life of the curtain walls. Most of the existing studies used dynamics methods to detect the debonding damage of curtain walls. However, these methods usually require additional load excitation, and the measured dynamic response data are susceptible to environmental noise, which makes it difficult to achieve reliable assessment of the safety condition of curtain walls. In order to solve the above problems, this paper proposes a method to detect the debonding damage of curtain wall units by using the deflection and rotation angles of the glass panel under the action of negative wind pressure. First, a series of debonding damage experiments of hidden frame glass curtain wall are designed to verify the feasibility of using deflection and rotation angle to detect the safety state of the curtain wall under wind load. Then, based on the experimental results, a safety risk monitoring system for hidden frame glass curtain walls is proposed, which can realize the real-time monitoring of curtain wall units and conduct rapid ide.pngication of debonding damage.