Structural Strength Analysis of a Tri-Floater Floating Foundation for Offshore VAWT

Vertical axis wind turbines(VAWTs) are advantageous for the development of large-scale offshore wind power because the drive system is located at the bottom of the turbine. This study investigates the structural strength of a tri-floater floating foundation supporting a 2.6 MW Darrieus VAWT. Finite element models of the floating foundation were developed using space plate-beam elements. The environmental loads, such as the aerodynamic loads, static wind loads, and wave-current loads, were considered. The general strengths of the floating foundation were calculated for the normal operating case(a cut-out wind speed of 25 m s^(-1) and blade rotation of 12 r min^(-1) were used to analyze the most unfavorable loads) and an extreme case(wind speed of 40 m s^(-1) and parked blades), and the weak components of the structure were analyzed. The results show that the floating foundation meets the strength requirements and the structural stress is highest when the wave, wind, and current are in a collinear direction. The main and secondary supporting bars transmit the loads between the stand columns and the tower foundation, and their stresses are higher than those in the other components. In the actual design, these supporting bars should be strengthened. The aerodynamic loads are very important and should be considered in the structural strength analysis of the floating foundation and the floating wind turbine system.

Seabed structures and foundations related to deep-sea resource development:A review based on design and research

The deep‐sea ground contains a huge amount of energy and mineral resources,for example,oil,gas,and minerals.Various infrastructures such as floating structures,seabed structures,and foundations have been developed to exploit these resources.The seabed structures and foundations can be mainly classified into three types:subsea production structures,offshore pipelines,and anchors.This study reviewed the development,installation,and operation of these infrastructures,including their structures,design,installation,marine environment loads,and applications.On this basis,the research gaps and further research directions were explored through this literature review.First,different floating structures were briefly analyzed and reviewed to introduce the design requirements of the seabed structures and foundations.Second,the subsea production structures,including subsea manifolds and their foundations,were reviewed and discussed.Third,the basic characteristics and design methods of deep‐sea pipelines,including subsea pipelines and risers,were analyzed and reviewed.Finally,the installation and bearing capacity of deep‐sea subsea anchors and seabed trench influence on the anchor were reviewed.Through the review,it was found that marine environment conditions are the key inputs for any offshore structure design.The fabrication,installation,and operation of infrastructures should carefully consider the marine loads and geological conditions.Different structures have their own mechanical problems.The fatigue and stability of pipelines mainly depend on the soil‐structure interaction.Anchor selection should consider soil types and possible trench formation.These focuses and research gaps can provide a helpful guide on further research,installation,and operation of deep‐sea structures and foundations.

Experiment Study of Dynamics Response for Wind Turbine System of Floating Foundation

The floating foundation is designed to support a 1.5 MW wind turbine in 30 m water depth. With consideration of the viscous damping of foundation and heave plates, the amplitude-frequency response characteristics of the foundation are studied. By taking into account the elastic effect of blades and tower, the classic quasi-steady blade-element/momentum（BEM） theory is used to calculate the aerodynamic elastic loads. A coupled dynamic model of the turbine-foundationmooring lines is established to calculate the motion response of floating foundation under Kaimal wind spectrum and regular wave by using the FAST codes. The model experiment is carried out to test damping characteristics and natural motion behaviors of the wind turbine system. The dynamics response is tested by considering only waves and the joint action of wind and waves. It is shown that the wind turbine system can avoid resonances under the action of wind and waves. In addition, the heave motion of the floating foundation is induced by waves and the surge motion is induced by wind. The action of wind and waves is of significance for pitch.

Numerical Simulation on Floating Behavior of Buoyancy Tank Foundation of Anemometer Tower

The intact stability and damage stability of a model of an anemometer tower with buoyancy tank foundation are computed by the finite element software MOSES in this paper. The natural period of the anemometer tower is discussed through frequency domain analysis. The influence of a single factor, such as towing point position, wave height, wave direction and wave period, on towing stability is discussed through time domain analysis. At the same time, the towing stability under the condition of various combinations of many factors is analyzed based on the measured data of the target area. Computer simulation results show that the intact stability is preferable and the damage stability is sufficient under the condition of plenty of subdivisions. Within the scope of the buoyancy tank foundation,the higher the towing point position is, the better the stability is. Wave height has a great impact on the motion amplitude of buoyancy tank foundation, but the effect on the acceleration is not obvious; wave period has a great impact on the acceleration, while the effect on the motion amplitude is not obvious; following-waves towing is more conducive to safety than atry.

Motion Characteristics of Novel Floating Foundation for Offshore Wind Turbine

A novel floating foundation to support the NREL offshore 5 MW wind turbine was designed conceptually by combining the characteristics of barge and Spar. The main focus was structural design and hydrodynamic modelling. Based on this novel floating foundation, the hydrodynamic performance was investigated in the frequency domain and time domain by using the wave analysis software Hydro D and Deep C from Det Norske Veritas. The frequency domain analysis was conducted to investigate the effects of the incident wave angle and water depth. The time-domain analysis was carried out to evaluate the response of the floating foundation under a selected operational condition. The hydrodynamic performances of this floating foundation with respect to time series and response spectra were also investigated in this study.

Optimal Skirt Spacing for Subsea Skirted Foundation Considering Floating Stability

A hydraulics model is built in Moses to find the optimal internal skirt spacing for the maximum floating stability of the skirted foundation. The results show that the increase in the internal skirts’ number can help improve the floating stability of the skirted foundation. However, with the increase in the internal skirts’ number, the improvement of floating stability becomes more and more weak. In this study, an optimal number of four are found for the internal skirt spacing. Moreover, to testify the feasibility of internal skirt spacing, a practical project is modeled, which indicates that the optimal internal skirt spacing can satisfy the requirements of towing. © 2017, Tianjin University and Springer-Verlag Berlin Heidelberg.

Design Methodology Research of the Floating Foundation for the Offshore MW-Rating Wind Turbine

With the rapid growth of the offshore wind industry, the innovative floating offshore wind turbine is chosen as the most feasible device to harvest the vast wind energy in deep water area. However there is no practical design guide for the floating wind turbine especially the floating foundation. In this paper, based on the investigation on the worldwide floating wind turbine and current available expertise on floating platforms accumulated in offshore O/G （oil and gas） industry, an integrated design methodology is presented according to the specialized characteristics of wind turbine, including the type selection of foundation and mooring system, design standard, design procedure, design conditions, key technologies involved. Finally a semi-submersible floating foundation is designed to support certain megawatt-rating wind turbine of Goldwind and also performance analysis and code checks are performed to validate the design. The design method of the floating foundation provided in this paper is proved feasible and can be adopted in practical engineering design.

Coupled Time-Domain Investigation on a Vertical Axis Wind Turbine Supported on a Floating Platform

The dynamic responses of a floating vertical axis wind turbine(VAWT)are assessed on the basis of an aero-hydro-mooring coupled model.The aerodynamic loads on the rotor are acquired with double-multiple stream tube method.First-and second-order wave loads are calculated on the basis of 3D potential theory.The mooring loads are simulated by catenary theory.The coupled model is established,and a numerical code is programmed to investigate the dynamic response of the semi-submersible VAWT.A model test is then conducted,and the numerical code is validated considering the hydrodynamic performance of the floating buoy.The responses of the floating VAWT are studied through the numerical simulation under the sea states of wind and regular/irregular waves.The effects of the second-order wave force on the motions are also investigated.Results show that the slow-drift responses in surge and pitch motions are significantly excited by the second-order wave forces.Furthermore,the effect of foundation motion on aerodynamic loads is examined.The normal and tangential forces of the blades demonstrate a slight increase due to the coupling effect between the buoy motion and the aerodynamic loads.

A method to Estimate Dynamic Responses of VLFS Based on Multi-Floating-Module Model Connected by Elastic Hinges

Based on the elastic foundation beam theory and the multi-floating-module hydrodynamic theory,a novel method is proposed to estimate the dynamic responses of VLFS(Very Large Floating Structure).In still water,a VLFS can be simplified as an elastic foundation beam model or a multi-floating-module model connected by elastic hinges.According to equivalent displacement of the two models in static analysis,the problem of rotation stiffness of elastic hinges can be solved.Then,based on the potential flow theory,the dynamic responding analysis of multi-floatingmodule model under wave loads can be computed in ANSYS-AQWA software.By assembling the time domain analysis results of each module,the dynamic responses of the VLFS can be obtained.Validation of the method is conducted through a series of comparison calculations,which mainly includes a continuous structure and a three-part structure connected by hinges in regular waves.The results of this paper method show a satisfactory agreement with the experiment and calculation data given in relative references.

One-Step-Installation of Offshore Wind Turbine on Large-Scale Bucket-Top-Bearing Bucket Foundation

In 2010,the first offshore wind turbine with integrated installation was established in Qidong sea area of Jiangsu Province,China,which led to the implementation phase of one-step-installation technique based on the design and construction of large-scale bucket-top-bearing (LSBTB) bucket foundation.The critical technique of LSBTB bucket foundation included self-floating towing,penetration with adjustment of horizontal levelness,removability and one-step-installation.The process of one-step-installation included the prefabrication of LSBTB bucket foundation in onshore construction base,installation and debugging of wind power,overall water transportation of foundation and wind power system,and installation of foundation and offshore wind turbine on the appointed sea area.The cost of one-step-installation technique was about 5 000 Yuan/kW,which was 30%-50% lower than that of the existing technique.The prefabrication of LSBTB bucket foundation took about two months.During the one-step-installation process,the installation and debugging of wind power and overall water transportation need about one to two days in sea area within 35 m depth.After the proposed technique is industrialized,the cost will be further reduced,and the installation capacity is expected to be up to 500 wind turbines per year.

海上风电单柱复合筒型基础拖航性能研究

单柱复合筒型基础结合了单桩基础与筒型基础的优点,能有效缩短施工期、降低成本且对环境友好。拖航是单柱复合筒型基础可重复利用、便于运输和安装的关键技术,需对拖航性能进行深入研究,为实际拖航过程提供技术指导。使用MOSES软件建立单柱复合筒型基础水动力模型,对单柱复合筒型基础的拖航过程进行数值模拟。计算结果表明,单柱复合筒型基础拖航性能较好,其运动响应受波浪和浮运条件影响显著,应避免横浪和大浪,且不宜在波浪周期接近基础固有周期时段拖航;通过调整系缆点高度、吃水深度及拖航速度可提升结构拖航稳性。

浮式风机风载荷与浮式基础运动相互影响研究

本文定量研究浮式风机系统风载荷与浮式基础运动间的相互影响。建立了浮式风力机系统一体化耦合动力学分析模型,对比分析了风载荷对系缆力、浮式基础运动、机舱加速度的影响及浮式基础运动对叶片相对流速、叶片推力和发电功率的影响。结果表明,风载荷显著影响浮式基础纵荡/纵摇平均值,对其标准差影响较小;风载荷对系缆力的平均值和标准差都有一定影响,而机舱加速度受风载荷的影响并不大;浮式基础运动对叶片相对风速的标准差有显著影响,离轮毂越远位置的相对风速受基础运动影响越大,这导致浮式风机叶片推力和发电功率有很大波动。为保证平稳发电,对浮式风机控制设计时,需考虑浮式基础运动的影响。

杭州电竞中心基础及地下室设计

杭州电竞中心项目采用桩基、筏板基础等多种基础形式,采用YJK软件进行多种基础形式之间的沉降差计算,并提出多种基础形式运用于同一建筑物时的加强措施。对于三面覆土、一面开敞地下室的不平衡水、土压力问题,利用桩基抵抗不平衡水、土压力,并提出相应的加强措施。将抗拔桩、无粘结预应力抗浮锚杆以及排水泄压多种抗浮技术应用于本工程,基于连通器原理的排水泄压主动抗浮技术的应用,大大减少抗浮锚杆的数量,获得了良好的经济效应;对于工程中多向框架梁与斜柱的连接节点,采用圆形柱帽有效约束各个方向相交的框架梁,并采用ABAQUS进行了有限元分析来模拟其受力性能,证明连接节点的可靠性。最后介绍了下沉庭院大跨度无柱弧形楼梯的设计,并对其进行舒适度验算,结果满足规范要求。

我国海上风电发展现状与趋势综述

近年来,在碳达峰目标与碳中和愿景下,海上风电在我国取得了长足的发展。分析了我国目前海上风电的发展现状与未来规划,对海上风电装机规模、新增机型以及采用的技术路线进行了汇总。重点介绍了海上风电基础型式、防腐技术和运维技术,其中,漂浮式海上风电是基础型式研究的重点,运维巡检和运维管理系统是风电运维技术研究的重点。通过分析海上风电的发展状况,整理了各项技术的主要技术路线和先进成果。最后,基于目前国内的技术发展现状及需求,对我国海上风电未来发展趋势进行展望。

风浪流单独及耦合作用下15 MW级浮式基础动力特性研究

了解风浪流等环境荷载效应对浮式基础设计及优化至关重要,为此,以15 MW级漂浮式基础为研究对象,系统性定量分析风浪流环境荷载单独及耦合作用下对浮式基础运动及系泊系统受力的影响。首先,以INOWINDMOOR 12 MW和TaiDa 15 MW浮式基础为原型设计新的15 MW级浮式基础,并在ANSYS-AQWA建立水动力分析模型,风力荷载及海流荷载通过风力系数、流力系数添加;其次,针对风浪流等环境荷载单独及耦合作用下浮式基础运动和系泊受力等特征开展分析。结果表明:浮式基础运动及系泊受力主要受风力和流力的影响,波浪会加剧浮式基础运动及系泊受力的往复性,并加大运动幅度及系泊受力;流荷载对浮式基础运动及系泊受力影响较大,特别是风、浪与流耦合作用时会导致系泊受力明显增加,实际工程设计时,流荷载应给与重点关注。

海上风电单柱复合筒型基础拖航浮运特性分析

为保证单柱复合筒型基础拖航安全性,针对实际工程中单柱复合筒型基础制作比尺模型,采用模型试验的方法,对单柱复合筒型基础浮运特性展开研究,分析不同拖航方式对结构的拖航特性的影响,旨在为实际工程提供指导性建议。研究结果表明:在实际拖航中,要合理的选择拖揽点的位置和吃水深度,避免结构出现艏倾现象,在保证安全拖航的前提下可适当增吃水深度增加结构的拖航稳性。

漂浮式风电技术现状及中国深远海风电开发前景展望

随着海上风电高速发展及近海场址资源趋紧,适用于深远海域风资源利用的海上漂浮式风电成为中国海上风电未来发展方向。本文介绍国外和国内漂浮式风电发展历程与现状,详细阐述了漂浮式风电从样机示范、小型漂浮式风电场到大规模商业化开发的发展路径,分析不同漂浮式风电基础概念及其特点。剖析了中国漂浮式风电本土化发展所需要面临的技术挑战,主要包括大容量漂浮式风力发电机组、低成本漂浮式风电基础平台、新型系泊系统国产化研制、动态缆系统研制、高效建造安装施工模式和智慧运维安全保障等。针对中国独有的海洋环境、港口码头状况和风电产业链情况,提出了海上漂浮式风电研究方向和发展建议:研发设计适用于中国深远海抗台型大容量漂浮式风电,突破漂浮式风电降本平价发展瓶颈;考虑高效集约用海布局,规模化发展漂浮式风电场;强健漂浮式风电产业完整供应链,推进核心部件和设备国产化进程;创新“海上风电+”新模式新路径,探索海上风电与油气田多能互补融合发展。本文研究对海上漂浮式风电平价商业化开发和扩展海洋能源利用空间具有重要意义。

四浮筒半潜式海上风机基础水动力性能分析

参照三浮筒式OC4半潜式风机基础,设计了四浮筒式浮式风机基础。建立三浮筒式OC4半潜式风机基础与四浮筒式浮式风机基础水动力模型,利用AQWA软件分析四浮筒式浮式风机基础相关水动力参数,并将四浮筒式浮式风机基础与三浮筒式OC4半潜式风机基础进行不同工况下的时域分析对比,探究两者间性能差异。结果表明,四浮筒式浮式风机基础具有良好的水动力性能,相较于三浮筒式OC4半潜式风机基础,其在纵荡、横荡、纵摇、艏摇4个自由度方向上的运动响应以及缆绳张力方面存在优势。

新型漂浮式海上风电基础概念设计和初步动力响应分析

提出适用于南海200 m水域的新型漂浮式风电基础概念设计,并基于NREL 5 MW风力涡轮机对新型基础进行性能分析。采用莫里森方程和势流理论计算水动力载荷,并利用ANSYS/AQWA软件建立风力机结构与水动力数值模型,探究其在频域范围内的水动力性能,计算分析漂浮式风力机在不同波况下的时域动力响应。结果显示,该基础的固有周期能较好地避开常见波浪的周期范围,避免引起共振,水动力性能良好,在南海某海域1年、20年和50年一遇的3种波况下基础的运动响应均满足规范要求,能保证漂浮式风力机在极端海况下的安全性和稳定性。

市区交通路口复杂基坑设计的实例分析

某基坑工程位于上海繁华地段路口,四周受到各类条件的制约,为了保持交通顺畅和减小对周边已有建筑的影响,该基坑较好地利用了工程自身条件和周边环境,从时间、空间等多个角度统筹基坑设计,合理利用各类基坑施工工艺,巧妙安排施工进程,最终很好地解决了诸多疑难问题,起到优化设计、节约成本和保护环境的作用。