Dynamic factor analysis considering elastic boom effects in heavy lifting operations

The dynamic factor is the ratio of the maximum dynamic load to the static load acting on the wire ropes between the boom of a floating crane and a cargo. In this paper, the dynamic factor is analyzed based on dynamic simulations of a floating crane and a cargo, considering an elastic boom. For the simulation, we designed a multibody system that consists of a floating crane barge, an elastic boom, and a cargo connected to the boom through wire ropes. The dynamic equations of motion of the system are based on flexible multibody system dynamics. Six-degree-of-freedom motions are considered for the floating crane and for the cargo, and three-dimensional deformations for the elastic boom. The hydrostatic force, the hydrodynamic force, the gravitational force, and the wire rope forces are considered as external forces. The dynamic factor is obtained by numerically solving the equation. The effects of the elastic boom on heavy cargo lifting are discussed by comparing the simulation results of an elastic boom and a rigid boom.     

浮船坞出运沉箱技术在船坞工程中的应用

采用气嚢搬运沉箱上浮船坞和浮船坞坐底出运沉箱的施工工艺,施工效率高且安全可靠,该工艺已在沉箱施工中得到了广泛应用。结合浮船坞修理改造后首次应用于渤海重工30万吨级大型船坞工程实例,介绍了浮船坞出运沉箱技术的工艺流程和施工要点,对类似工程的施工具有一定的参考价值。     

Dynamic response simulation of a heavy cargo suspended by a floating crane based on multibody system dynamics

In this paper, the dynamic response simulation of heavy cargo suspended by a floating crane is performed. The dynamic equations of the motions of the floating crane and the heavy cargo must be considered by the coupled equations because the floating crane and the heavy cargo are connected by wire ropes and provide force and a moment for each other. Hence, the dynamic equations of motion are set up for considering the 6-degrees-of-freedom floating crane and the 6-degrees-of-freedom cargo based on multibody system dynamics. The nonlinear terms in the equations of motion are considered. In addition, the nonlinear hydrostatic force, the linear hydrodynamic force, the wire rope force, and the mooring force are considered as the external forces. Finally, we estimate the motion of the floating crane and the heavy cargo and also calculate the tension of the wire rope between the two.     

Dynamic Response of Offshore Wind Turbine on 3×3 Barge Array Floating Platform under Extreme Sea Conditions

Offshore wind farm construction is nowadays state of the art in the wind power generation technology.However,deep water areas with huge amount of wind energy require innovative floating platforms to arrange and install wind turbines in order to harness wind energy and generate electricity.The conventional floating offshore wind turbine system is typically in the state of force imbalance due to the unique sway characteristics caused by the unfixed foundation and the high center of gravity of the platform.Therefore,a floating wind farm for 3×3 barge array platforms with shared mooring system is presented here to increase stability for floating platform.The NREL 5 MW wind turbine and ITI Energy barge reference model is taken as a basis for this work.Furthermore,the unsteady aerodynamic load solution model of the floating wind turbine is established considering the tip loss,hub loss and dynamic stall correction based on the blade element momentum(BEM)theory.The second development of AQWA is realized by FORTRAN programming language,and aerodynamic-hydrodynamic-Mooring coupled dynamics model is established to realize the algorithm solution of the model.Finally,the 6 degrees of freedom(DOF)dynamic response of single barge platform and barge array under extreme sea condition considering the coupling effect of wind and wave were observed and investigated in detail.The research results validate the feasibility of establishing barge array floating wind farm,and provide theoretical basis for further research on new floating wind farm.     

气囊出运沉箱的安全控制

伴随着深水泊位的建设，大型沉箱因具有良好的整体性、稳定性、施工的高效性而备受设计单位和建设单位的青睐，具有广泛的应用前景，如何确保沉箱的出运安全成为所有施工单位关注的焦点。成功采用了“超高压气囊顶升、运移沉箱上浮船坞出运沉箱”的施工工艺安全出运百余大型沉箱。结果表明，以安全生产责任制为核心，采用防治结合方法将其进行认真落实，保证措施有效是气囊出运沉箱安全的必要条件和有效保证。     

Analytical and experimental studies on installation of a suction caisson with tampered tip in clay

Concrete suction caissons have been successfully used as breakwaters or seawalls in recent years. The relative large wall thickness-to-diameter ratio of a concrete caisson can lead to the formation of a full soil heave plug that may cause difficulties in the installation of concrete caisson in clay. One way to overcome this limitation is to use a tampered tip for the caisson wall. An analytical method is proposed in this article to calculate the minimum suction pressure required to penetrate a caisson and the maximum allowable suction pressure that can be applied to avoid too much soil heave plug during the installation of the suction caisson. Four model tests were conducted in normally consolidated clay to study the installation process of a concrete suction caisson with tampered tip and to verify the proposed analytical method. The height of the soil heave plug in the caisson with a tampered tip is observed to be about half of that in the caisson with a flat tip.     

世越号起吊姿态敏感性分析与方案选择

韩国世越号打捞是世界上首次利用托底钢梁原状态整体起吊难船出水的工程。客滚难船装载的货物容易在沉没后发生移位,上层建筑长时间沉没海底后发生泥沙淤积导致难以准确估计整船的重量重心及浮力浮心的位置。利用水池模型试验和数值计算两种方法分别对大型浮吊船单臂架打捞法和双驳船抬吊打捞法进行了难船姿态受重心位置偏移的敏感性分析。水池模型试验中发现,用大型浮吊船单臂架打捞法,世越号的姿态受其重心位置偏移非常敏感,容易发生侧翻;而用双驳船抬吊打捞法,世越号的姿态受其重心位置的影响非常有限,难船和抬浮驳船都可以保持一个较好的姿态。对比水池模型试验的结果,由于难以计及托底钢梁的翘动和滑动现象,数值计算中得到的难船起吊姿态值偏小。双驳船抬吊打捞法被选为打捞世越号的施工方案,其对难船重心位置偏移不敏感的特性得到了现场实证。这个特点为世越号的成功打捞出水起到了关键作用。     

地震荷载沉箱码头大变形分析的离散元法初探

探讨了应用离散元分析方法求解地震荷载下沉箱和背后填土大变形问题的可能性,开发了能描述沉箱的平面形状及沉箱与土体摩擦特性的矩形单元。并通过简单实例分析了地震时沉箱码头的变形,再现了沉箱码头地震灾害的发生过程,为沉箱在地震情况下的大变形分析提供了一种新途径。比较了两种沉箱模型对分析结果的影响,提出了相应的方法。     

Large deformation finite element analysis of the installation of suction caisson in clay

The suction caisson (or called suction anchor) which is considered as a relatively new type of foundation of offshore structures, has been extensively studied and applied for offshore wind turbines and oil platforms. The installation of the suction caisson is of great importance in the design and construction because it can bring about several issues and further influence the performance of holding capacity in safety service. In this paper, large deformation finite element (FE) analyses are performed to model the installation of suction caisson (SC) by suction and jacking in normally consolidated clay. The penetration of the suction caisson is modeled using an axisymmetric FE approach with the help of the Arbitrary Lagrangian–Eulerian (ALE) formulation which can satisfactorily solve the large deformation problem. The undrained shear strength of the clay and elastic modulus are varied with depth of soil through the subroutine VUFIELD. The numerical results allow quantification of the penetration resistance and its dependence on the installation method. The centrifuge test and theoretical solution are used for the FE model validation. After the validation, the penetration resistance, the soil plug heave, and the caisson wall friction have been examined through the FE model. Based on the numerical results, it is shown that the ALE technique can simulate the entire suction caisson penetration without mesh distortion problem. The installation method can play an important role on the penetration resistance, namely, the suction installation reduces the penetration resistance significantly compared to the purely jacked installation. With a further study on the suction case, it is found that as the final applied suction pressure increases, the soil plug heave increases, while the penetration resistance reduces with increase of the final suction pressure. The effect of the friction of internal caisson walls has been also investigated and a conclusion is drawn that internal wall friction has a significant contribution to the penetration resistance and it can be implicitly represented by varying coefficient of internal wall friction. As for the penetration resistance, both jacked and suction installation have great dependency on the internal wall friction.     

海上风机稳桩施工平台吊装过程中的多船水动力干扰特性与动力响应分析

建立双臂起重船从运输船上起吊大型稳桩施工平台的吊装系统模型,其中,起重船与运输船呈T型布置。首先基于势流理论,采用专业水动力分析软件AQWA开展了双船系统的频域水动力分析,分析双船起吊系统的水动力干扰特性和遮蔽效应,并对双船间隙自由液面进行黏性修正从而提高频域多体水动力分析的精度。进一步采用频域—时域方法对起吊耦合系统进行参数分析,探究起吊速度、波浪周期等对吊索张力和起重船运动的影响规律。分析多个工况下运输船的遮蔽效应对起吊系统的影响。结果表明,对间隙流体施加阻尼自由液面边界条件可以一定程度提高计算模型的精度,在某些周期的迎浪条件下运输船对起重船的遮蔽效应可以降低吊装系统的响应;起吊速度对时域动力响应的影响较小;周期为8 s的规则波引起过大的动力响应。     

Calculation of Wave Pressure and Pressure Spectrum for Perforate-Pipe Breakwater

Standing waves are formed due to the reflection when waves meet vertical wall,thereforestrong structures are needed to keep the wall stability under the serious wave attack.For the improvementof the working condition and increase of the stability of the wall,the lower reflecting breakwaters have at-tracted close attention Reports mostly from Japanese researchers are often concerned with the wall ofcaisson equipped with open windows.In this paper a kind of hollow-pipe perforated breakwater is exam-ined which waves may partially perforate into the harbour basin.The wave in front of the wall can onlyform partial standing wave and wave force is reduced obviously.And the theoretical calculation of waveforce and analysis of wave force spectrum are all derived.Comparison between the results from theoreticalcalculation and hydraulic modeling shows reasonable agreement.     

光纤光栅称重传感器在大型海上浮吊中的应用

为了实现大型海上浮吊臂架结构健康状态监测,开发了大型海上浮吊光纤光栅称重传感器系统,提出了光纤光栅称重传感器设计理论,建立了传感器设计框架。通过悬臂梁理论,借助于有限元分析软件,提出了悬臂梁和受压弹性体复合结构;通过温度补偿理论与对比,提出了滤波温度补偿方案;通过迟滞效应原理,提出了双光栅式迟滞效应消除方案。进行光纤光栅称重传感器性能实验、反复性实验和稳定实验,讨论了系统的性能和可行性。并将大型海上浮吊光纤光栅实时称重系统应用于实际工程项目,成功实现了大型海上浮吊负重状况监测。     

Wave Motion Compensation Scheme and Its Model Tests for the Salvage of An Ancient Sunken Boat

1 .IntroductionIt is always hopedthat sunken merchant vessels would resume their ship performances after sal-vage ,that ancient sunkenships of archeological value would be salvagedinits entirety withlittle harmtothe cultural relics ,andthat warships with …     

Stability of jetties for channel protection in soft soils at Huanghua Port

This paper presents safety evaluations of jetties found on soft clays at Huanghua Port to protect the channel from deposition due to long shore transport. It is likely to be the most critical for the jetties during construction, as far as excess pore water pressure and its effects on the embankment stability are concerned. A rubble mound jetty and a caisson jetty are considered as design alternatives for comparison. Finite element analysis and limit equilibrium analysis are carried out to evaluate the stability of the jetties during construction. For the rubble mound jetty, effective stresses in the soft clays are calculated associated with consolidation, so as to estimate the shear strength increased thereby. With the effective stresses and shear strength, the critical situation of the rubble mound jetty is revealed by the limit equilibrium analysis. For the caisson jetty, wave action is concerned, which is transformed into distributed forces on the caisson. Both the finite element analysis and the limit equilibrium analysis indicate a potential general shear failure of the caisson jetty and the foundation.     

软土地基沉箱防波堤失稳模式及稳定性分析方法

针对现阶段深水软黏土地基防波堤建设的设计理论和稳定性分析方法尚不成熟,结合实际工程,采用三维弹塑性有限元数值分析方法,研究在水平或竖直单一方向荷载以及复合加载条件下软黏土地基上沉箱防波堤的失稳模式,提出破坏包络线的稳定性判别方法。在波浪水平荷载作用下,深水软基上沉箱防波堤发生倾覆失稳破坏,失稳转动点为沉箱底面以下中轴线偏右的某点,不同于规范中规定的岩石或砂质地基沉箱倾覆转动点为其后踵点;在重力等竖向荷载作用下,沉箱的失稳模式为结构整体下陷,抛石基床及地基形成连贯的塑性区域,呈现较明显地冲剪破坏形式;在水平、竖向复合荷载作用下,软基上沉箱防波堤的破坏包络线由结构倾覆破坏线和地基承载力破坏线组成,包络线将荷载组合区分成稳定区、仅发生水平承载力不足倾覆破坏区、仅发生地基竖向承载力不足破坏区、同时发生水平承载力和地基竖向承载力不足破坏区4个区域。研究成果为深水软基沉箱防波堤建设提供参考和借鉴。     

Transportation of floating structures by using newly built heavy lifting semi vessel HYSY278

Transportation of floating structures for long distance has always been associated with the use of heavy semi transport vessel. The requirements of this type of vessel are always special, and its availability is limited. To prepare for the future development of the South China Sea deepwater projects, COOEC has recently built a heavy lift transport vessel — Hai Yang Shi You 278 (HYSY278). This semi-submersible vessel has displacement capacity of 50k DWT, and a breath of 42 m. Understanding the vessel’s applicability and preparing its use for future deepwater projects are becoming imminent need. This paper reviews the critical issues associated with the floating structure transportation and performs detailed analysis of two designed floating structures during transportation. The newly built COOEC transportation vessel HYSY278 will be used to dry transport the floating structures from COOEC fabrication yard in Qingdao to the oil field in the South China Sea. The entire process will start with load-out/float-off the floating structures from the construction sites, offload the platform from the vessel if needed, dry transport floating structures through a long distance, and finally offload the platform. Both hydrodynamic and structural analyses are performed to evaluate transport vessel and floating structures. Critical issues associated with the transportation and offloading of platform from the vessel will be studied in detail. Detailed study is performed to evaluate the response of the system during this phase and additional work needed to make the vessel feasible for use of this purpose. The results demonstrate that with proper modifications, HYSY278 can effectively be used for transporting structures with proper arrangement and well-prepared operation. The procedure and details are presented on the basis of study results. Special attentions associated with future use will also be discussed based on the results from analysis.     

Laboratory experiments for wave motions and turbulence flows in front of a breakwater

In this paper, laboratory data for free surface displacements and velocity fields in front of a caisson breakwater covered with wave-dissipating blocks, together with wave pressures acting on the caisson, are presented and discussed. The core of the breakwater is made of a concrete caisson with a vertical front wall. The caisson is protected by a thick layer of tetrapods and is supported by a rubble mound. The breakwater is placed on the 1/25 impermeable slope. Two types of incident waves are used in the experiments: nonbreaking waves and spilling-type breaking waves. In the breaking wave case, the incident wave breaks offshore before it reaches the breakwater. The velocity data are obtained by using both the Laser Doppler Velocimeter (LDV) and the Electromagnetic Current Meter (EMCM). The raw data are analyzed using a numerical-filtering scheme so that turbulent fluctuations are separated from the phase-dependent wave motions. The vertical profiles of the time-averaged (over a wave period) turbulent velocity components at several vertical cross-sections in front of the breakwater are then analyzed. The spatial variations of the time-averaged turbulence velocity suggest that turbulence is generated inside the protective armor layer and transported into the flow region in front of the breakwater. The wave pressures on the vertical face and on the bottom of the caisson are also reported.     

Nonlinear identification of mooring lines in dynamic operation of floating structures

An adaptive algorithm for on-line estimation of physical coefficients of cables in viscous environment is presented. The procedure is useful for obtaining cable characteristics, which are needed in stability analysis and control system design for moored floating structures. It uses measurements of position and forces from on-board instrumentation. It is also able to track changes in the depth and to test for parameter consistency in order to confer the estimation robustness with respect to dynamic perturbations. It is based on nonlinear solvers, which can cope with transcendental functions of the model structure. The proof of asymptotic convergence is presented. Finally, three basic case studies are analyzed.     

柔性气囊助浮法拆除导管架技术研究

文中研究采用柔性气囊助浮法起升导管架的拆除技术。浅水海域浮吊进入困难并且拆除导管架的施工费用昂贵。考虑气囊产生的浮力巨大、价格便宜及连接结构方便的特点,针对即将拆除的QK18-2平台,设计气囊助浮起升导管架的技术方案。考虑水深确定导管架吃水,设计气囊与导管架的连接方式。针对导管架在位起浮状态,计算带有气囊的导管架系统幅频响应RAOs,考虑不同的海洋环境参数,计算分析风浪流作用下导管架系统6个自由度的时域运动响应,文中提出了多点系泊控制导管架运动的合理系泊方式。研究结果表明,气囊助浮法拆除导管架技术具有较高的工程实用价值,针对目标导管架平台设计的气囊助浮拆除技术方案,具有费用低、风险小及不需使用浮吊的技术优势,该项技术可以在导管架平台拆除中推广应用。     

海洋中波浪下迎浪驳船运动对两矩形驳船间窄缝内水体共振的影响

A three-dimensional time-domain potential flow model is developed and applied to simulate the wave resonance in a gap between two side-by-side rectangular barges. A fourth-order predict-correct method is implemented to update free surface boundary conditions. The response of an up-wave barge is predicted by solving the motion equation with the Newmark-β method. Following the validation of the developed numerical model for wave radiation and diffraction around two side-by-side barges, the influence of up-wave barge motion on the gap surfaceresonance is investigated in two different locations of the up-wave barge relative to the back-wave barge at various frequencies. The results reveal that the freely floating up-wave barge significantly influences the resonance frequency and the resonance wave amplitude. Simultaneously, the up-wave barge located in the middle of the back-wave barge leads to a reduction in the resonance wave amplitude and motion response when compared with other configurations.