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A blastproof partition wall in civil air defense engineering is easily subjected to out-of-plane impact loads, such as object impacts, and structural collapse in peacetime. In this study, the pendulum impact test was carried out for the first time on six blastproof partition walls pasted with fiber-reinforced polymer (FRP). Using a method combining finite element simulation and experimental research, the influence of parameters such as the FRP type, layer number and width, and pendulum impact number on the impact resistance of the wall was systematically studied. The test results show that pasting FRP on the back of the blastproof partition wall can significantly improve the impact resistance and reduce the damage degree of the concrete. The impact recovery coefficient increased from 0.33 to 0.57, but with the increase in the number of impacts, large-rupture-strain FRP (LRS-FRP) can give full play to the advantages of a large tensile fracture strain and cooperate with the wall to deform, and the selection of FRP with a large tensile fracture strain is the key to resisting multiple impact loads. Finally, the experimental basis and an economical and reliable protection method are provided for the study of improving the impact resistance of the blastproof partition wall.

The physical model test interlinks the concept design and sea trial during the commercial utilization of wave energy converter. Aiming at the oscillating buoy wave energy converter, the energy conversion principle is firstly decomposed. Then, the model scale requirement of fluid motion and corresponding hydrodynamic similarity criterion considered in the physical model test are introduced. Finally, the solution of scaling orchestration problem is proposed considering the overall model scale in different energy conversion processes. The hydrodynamic similarity criterion is selected based on the working mechanism of the energy-capturing body only in contact with water, and the model scale requirements during the other stages of energy conversion structure are determined by the main mechanical factors. The first-stage energy conversion of device is recommended to meet the Froude similarity requirements, while the second-stage and third-stage energy conversions only need to meet the power similarity requirements. The power scale ratio in the three energy conversions is recommended to be consistent with the Froude similarity, and there are no requirements of geometric shape of second-stage and third-stage energy conversions to meet the similarity criteria.

During the long-term service condition, the mooring line of the deep-water floating platform may fail due to various reasons, such as overloading caused by an accidental condition or performance deterioration. Therefore, the safety performance under the transient responses process should be evaluated in advance, during the design phase. A series of time-domain numerical simulations for evaluating the performance changes of a Floating Production Storage and Offloading (FPSO) with different broken modes of mooring lines was carried out. The broken conditions include the single mooring line or two mooring lines failure under ipsilateral, opposite, and adjacent sides. The resulting transient and following steady-state responses of the vessel and the mooring line tensions were analyzed, and the corresponding influence mechanism was investigated. The accidental failure of a single or two mooring lines changes the watch circle of the vessel and the tension redistribution of the remaining mooring lines. The results indicated that the failure of mooring lines mainly influences the responses of sway, surge, and yaw, and the change rule is closely related to the stiffness and symmetry of the mooring system. The simulation results could give a profound understanding of the transient-effects influence process of mooring line failure, and the suggestions are given to account for the transient effects in the design of the mooring system.

For the marginal oilfield with low oil extraction, adding wave energy conversion device integration to the jacket platform is very meaningful for reducing the mining cost. First, the design concept of integrated oscillating water column (OWC) device with jacket platform is proposed. Then, the optimal model of OWC device structural arrangement parameters is established with the aim of low wave force and high wave energy conversion efficiency. Finally, the dynamic response of the integrated device is analyzed under the working and extreme sea states. The results show that the integrated device has certain effectiveness and feasibility.

Logistical supply is costly for the deepwater oil and gas exploitation, thereby it is necessary to develop a novel power supply solution to improve the offshore structure’s self-holding capacity. The two-body point absorbers, as a renewable energy device, have achieved a rapid development. Heave plate is used to constrain the truss’s motion in the two-body point absorber, and the floater moves along the truss up and down. This two-body point absorber can be considered to be an essentially mass-spring-damper system. And it is well known that the heave plates have been widely used in the Spar platform to suppress the heave motions. So if the two-body point absorber can be modified to combine with offshore floating structures, this system can not only offer electric power to support operations or daily lives for the platform, but also control the large motions in the vertical plane. Following this concept, a novel tuned heave plate (THP) system is proposed for the conventional semi-submersible platform. In order to investigate the dynamic performances of the single THP, two experiments are conducted in this paper. First, the hydrodynamic coefficients of the heave plates are studied, and then the THP experiments are carried out to analyze its dynamic performance. It can be concluded that this THP is feasible and achieves the design objective.

The accurate estimation of mooring line damping is significant for the mooring system design and the global motion responses analysis. Aiming at the existing method of mooring damping estimation can only calculate the total damping contribution of mooring line, an improved method is proposed to accurate estimate the mooring line segments damping contribution to the floating structures. The dynamic responses analysis model of mooring line is established firstly. Secondly, the fluid drag force on the mooring line element and its working energy dissipation are obtained. Then, the mooring damping of each segment of mooring line could be calculated through piecewise integration combined with the indicator diagram method. Finally, the proposed method is validated by comparing with the experimental results of single catenary chain with the top end forced excitation in the wave tank. The results show that the proposed method could both accurately estimate the damping contribution of whole mooring line and each segment, which is suitable for the mooring damping estimation of single component and multi-components mooring line.

The porous structures are widely designed in coastal and ocean engineering to reduce the wave load. A macroscopic CFD approach is established to study the wave interaction with a porous plate placed in front of a solid wall. The established numerical wave tank was firstly validated by the analytical results of a vertical wall, and the macroscopic CFD model was validated by the experimental results of a single vertical porous plate. Then the wave load reduction effect of a solid wall with a vertical porous plate in front is investigated, the influences of porosity and relative gap width are compared, and the effects of wave height are also analyzed. The results demonstrate that the porosity and relative gap width are the main effect factors to the wave force reduction effect, and the wave forces on structure increase almost linearly with the increase of relative wave height, while the wave load reduction coefficient and refection coefficient are not linearly. A porosity of 0.2 and relative gap width of 0.2–0.3 are deemed to be optimal geometry parameters at which the wave load reduction effect is optimal. The total horizontal wave force increases nonlinearly with the increase of wave heights, and the quadratic pressure drop condition is essential when studying the wave force on thin porous structures.

A numerical simulation platform is established to realize the active truncation model test method of deep-water mooring system, and the time delay is focused in this paper. The Stewart platform is chosen as the actuator aiming to realize the motion control of truncated point in mooring line. The corresponding kinematic model and motion control strategy of actuator are established. The method of cubic spline interpolation is proposed to solve the time delay compensation of actuator motion control, the influences parameters affecting compensation results are compared, and the corresponding compensated effects are verified. Through compensating the input signal of actuator, the real-time motion tracking accuracy of the truncated point of mooring line is effectively improved, which have contribution to the success of following physical experiments.

Porous structures have been widely applied in the coastal and ocean engineering. In the CFD (Computational Fluid Dynamics) simulations of interactions between waves and porous structures, the microscopic model establishment approach usually requires huge amounts of fine grids around the model boundary, thus causing a huge computational overhead. This paper establishes a CFD numerical model using a macroscopic approach to simulate the interaction between waves and a vertical porous plate. By analysing the pressure loss of the interaction above and adding it into the momentum equation as a source term, the macroscopic porosity simulation can be implemented without using huge amounts of fine grids around the perforations. A series of CFD simulations of wave interacting with a vertical porous plate are performed based on the established numerical model, and the corresponding tank tests are conducted. The effects of wave characteristics and porosity of porous plate on horizontal wave force and the reflection and transmission coefficients are analyzed. The results demonstrate that the established model is reliable for engineering analysis and thereby being of great significance for reference purpose in the CFD simulations of waves interacting with porous structures.

The motion of truncated point in the active-truncated model test of deep-water mooring system can be simulated using the actuator, and the motion tracking control of actuator determines the validity of test results. Taking the Stewart Platform as actuator, the kinematic model is established. The permanent magnet synchronous motor (PMSM) is selected as the drive motor of actuator, and the transfer function is identified using the white noise signal excitation. The Feedforward control and RBF neural network control methods are designed to compare the motion tracking control effect at the truncated point and the corresponding influences on the top tension at the fairlead. The simulation results show that the feedforward control can reduce the motion tracking error by 50% while the RBF neural network can reduce the tracking error by 75%, which both have obvious effect on the motion tracking control and provide theoretical basis for constructing the active-truncated model test platform of deep-water mooring system.

The mooring system may appear slack-taut alternating transformation with the motion excitation of floating structure, resulting in the dynamic tension amplitude of mooring line significantly increase. Based on the dynamic finite element analysis, a series of sinusoidal excitations with different amplitudes and frequencies are applied at the top of mooring line, and the results show that the slack-taut phenomenon would occur when the top excitation reaches a certain amplitude and frequency. The minimum value of tension is close to zero, and the maximum value can reach several times of pre-tension. The spectrum analyses show that the components of high frequency appear besides the excitation frequency, and the main factor affecting slack-taut phenomenon of mooring line is the component of excitation along axial direction of mooring line. Through improving the initial pre-tension, selecting the cable with large elastic modulus and small cross-section diameter, and making the length of mooring line as short as possible, these settings would have benefit for keeping mooring line in the taut state and avoid the occurrence of snap load. The results of this paper would have significant reference for further exploring the mechanism of snap load in the mooring system and its design and safety assessment.

Structural control plays an important role in suppressing structural vibration under different loads. During a severe earthquake, a structure will exhibit nonlinear behaviors. In this case,...

A fully coupled 6-degree-of-freedom nonlinear dynamic model is presented to analyze the dynamic response of a semi-submersible platform which is equipped with the dynamic positioning (DP) system. In the control force design, a dynamic model of reference linear drift frequency in the horizontal plane is introduced. The dynamic surface control (DSC) is used to design a control strategy for the DP. Compared with the traditional back-stepping methods, the dynamic surface control combined with radial basis function (RBF) neural networks (NNs) can avoid differentiating intermediate variables repeatedly in every design step due to the introduction of a first order filter. Low frequency motions obtained from total motions by a low pass filter are chosen to be the inputs for the RBF NNs which are used to approximate the low frequency wave force. Considering the propellers’ wear and tear, the effect of filtering frequencies for the control force is discussed. Based on power consumptions and positioning requirements, the NN centers are determined. Moreover, the RBF NNs used to approximate the total wave force are built to monitor the disturbances. With the DP assistance, the results of fully coupled dynamic response simulations are given to illustrate the effectiveness of the proposed control strategy.

A novel tuned heave plate energy-harvesting system (THPEH) is presented for the motion suppressing and energy harvesting of a semi-submersible platform. This THPEH system is designed based on the principle of a tuned mass damper (TMD) and is composed of spring supports, a power take-off system (PTO) and four movable heave plates. The permanent magnet linear generators (PMLG) are used as the PTO system in this design. A semi-submersible platform operating in the South China Sea is selected as the research subject for investigating the effects of the THPEH system on motion reduction and harvesting energy through numerical simulations. The numerical model of the platform and the THPEH system, which was established based on hydrodynamic analysis, is modified and validated by the results of the flume test of a 1:70 scale model. The effects of the parameters, including the size, the frequency ratio and the damping ratio of the THPEH system, are systematically investigated. The results show that this THPEH system, with proper parameters, could significantly reduce the motions of the semi-submersible platform and generate considerable power under different wave conditions.