强台风下导管架平台倒塌全过程数值仿真

针对强台风引起的平台倒塌问题,综合隐式有限元与显式动力有限元算法,建立导管架平台结构倒塌全过程仿真流程;提出基于重现期的Pushover分析方法,充分考虑平台侧向环境载荷分布的变化以及可能的甲板上浪载荷因素,使得确定的倒塌环境载荷更加真实;采用APDL编制平台隐式与显式有限元模型转化程序,有效解决波浪载荷计算与精确施加的难题;在此基础上,应用LS-DYNA实现导管架平台在强台风载荷下的倒塌全过程仿真,动态再现平台结构倒塌过程中的构件破坏失效及内力分布,深入揭示平台结构的倒塌机理。研究成果可为导管架平台结构抗台风设计及理论研究提供参考。     

Investigation on Cutting Stability of Jacket in Decommissioning Process

Jacket cutting operation is one of the most complicated and highest risk operations in the process of decommissioning offshore piled platform, the security and stability of which must be assured. In this paper, the current research on offshore structure removal and jacket cutting is introduced, on the basis of which the types of load along with the load calculation method are determined. The main influences on the stability of a jacket in cutting are analyzed. The experiment test plan is drawn by using orthogonal testing method, and the formula of critical load during the cutting procedure is deduced by differential evolution algorithm. To verify the method and results of this paper, an offshore piled platform to be decommissioned in the South China Sea is taken for an example, and the detailed schedule for jacket cutting is made with the three-dimensional finite element model of the jacket established. The natural frequency, stress, strain and stability of the jacket during cutting process are calculated, which indicates that the results of finite element analysis agree well with that of the deduced formula. The result provides the scientific reference for guaranteeing the safety of jacket in cutting operation.     

靠球减震系统在导管架平台中的应用

导管架生产储油平台在油轮靠泊和外输期间,如遇风浪天气,平台的晃动非常明显,为此引入橡胶靠球减震系统。运用ANSYS有限元分析软件,建立导管架生产储油平台的真实有限元模型,计算平台在靠船碰撞力和波浪力共同作用下平台关键点位置应力变化及振动响应过程,为靠球减震系统在实际工程中应用提供理论依据。     

导管架式海上风力发电支撑结构振型扩阶方法

提出1种适用于海上风力发电支撑结构的模态振型扩阶方法。该方法无需借助转换矩阵实现振型扩阶,而是依靠实测模态并通过修正有限元模型对应振型在未测试自由度的振型值而获得空间完备的模态振型,并且所发展的方法在一定程度上可以忽略有限元模型存在的建模误差,是1种直接的估算方法,计算效率相对较高。文中采用三桩导管架式海上风力发电支撑结构验证提出方法的正确性以及在低阶模态振型扩阶上的优越性。数值结果表明,该方法对传感器位置、数量依赖程度低,尤其对于海上风电结构,仅在结构的水深较浅部位布置少数传感器即可比较精确的实现低阶模态振型扩阶,具有良好的工程应用前景。     

The co-location of offshore windfarms and decapod fisheries in the UK: Constraints and opportunities

The offshore wind sector in the UK is expanding rapidly and is set to occupy significant areas of the coastal zone, making it necessary to explore the potential for co-location with other economic activities. The presence of turbine foundations introduces hard substrates into areas previously dominated by soft sediments, implying that artificial reef effects may occur, with potential benefits for fisheries. This review focuses on the possibilities for locating fisheries for two commercially important decapods, the brown crab Cancer pagurus and the European lobster Homarus gammarus, within offshore wind farms.Existing understanding of habitat use by C. pagurus and H. gammarus suggests that turbine foundations have the potential to act as artificial reefs, although the responses of these species to noise and electromagnetic fields are poorly understood. Offshore wind farm monitoring programmes provide very limited information, but do suggest that adult C. pagurus associate with turbine foundations, which may also serve as nursery areas. There was insufficient deployment and monitoring of rock armouring to draw conclusions about the association of H. gammarus with offshore wind farm foundations. The limited information currently available demonstrates the need for further research into the ecological and socio-economic issues surrounding fishery co-location potential.     

Assessment of the dynamic behaviour of saturated soil subjected to cyclic loading from offshore monopile wind turbine foundations

The fatigue life of offshore wind turbines strongly depends on the dynamic behaviour of the structures including the underlying soil. To diminish dynamic amplification and avoid resonance, the eigenfrequency related to the lowest eigenmode of the wind turbine should not coalesce with excitation frequencies related to strong wind, wave and ice loading. Typically, lateral response of monopile foundations is analysed using a beam on a nonlinear Winkler foundation model with soil–pile interaction recommended by the design regulations. However, as it will be shown in this paper, the guideline approaches consequently underestimate the eigenfrequency compared to full-scale measurements. This discrepancy leads the authors to investigate the influence of pore water pressure by utilising a numerical approach and consider the soil medium as a two-phase system consisting of a solid skeleton and a single pore fluid. In the paper, free vibration tests are analysed to evaluate the eigenfrequencies of offshore monopile wind turbine foundations. Since the stiffness of foundation and subsoil strongly affects the modal parameters, the stiffness of saturated soil due to pore water flow generated by cyclic motion of monopiles is investigated using the concept of a Kelvin model. It is found that the permeability of the subsoil has strong influence on the stiffness of the wind turbine that may to some extent explain deviations between experimental and computational eigenfrequencies.     

Industry-academe linkages in the Philippines: Embedding foreign investors,capturing institutions?

The global sourcing of services from developing countries has made human capital a key local asset for attracting foreign direct investment. This paper analyses to what extent individual companies engage in linkages and collaborations with universities and how the education sector responds to the new demands of the knowledge economy. Offshore services are generally recognised as ‘footloose’ investments with limited local linkages. A case study of industry-academe linkages in the growing business process outsourcing sector in the Philippines finds that foreign investors engage in active embedding and develop linkages with human resource providers, leading to increased territorial embeddedness. This paper investigates the kind of linkages created, which actors engage in them and their motivations, to understand the resulting implications for local economic development. Interviews with foreign investors and higher education institutions reveal that most collaboration is initiated by large call centre companies and focuses on entry-level skills development for their operations. I argue that multinational corporations have been able to capture local institutions and introduce changes in the education system to supply mainly lower-end skills. While increasing the available talent pool and raising the competitiveness for further investments, this presents challenges for upgrading into higher value-added services and potentially transforms the country into a dependent market economy.     

The stable aryl hydrocarbon receptor agonist potency of United Kingdom Continental Shelf (UKCS) offshore produced water effluents

The in vitro aryl hydrocarbon receptor (AhR) agonist potency of offshore produced water effluents, collected from the United Kingdom Continental Shelf, was determined using the dioxin responsive (DR)-chemically activated luciferase expression (CALUX) assay. Octadecylsilane (C18) solid phase extraction (SPE) extracts of produced water were exposed to DR-CALUX cells for 24 h in order to investigate the contribution in potency from compounds that are stable to metabolism by the CALUX cells during exposure. The stable AhR agonist potency determined over 24 h was highly variable and ranged from 1 to 430 ng TCDD TEQ_CALUX l⁻¹. These data reflect the highly variable composition of produced water discharges from different production fields. It is recommended that further work be performed to characterise the full range of stable dioxin like AhR agonists present in offshore produced water discharges using techniques such as bioassay-directed analysis.     

System Reliability Analysis of an Offshore Jacket Platform

This study investigates strategies for solving the system reliability of large three-dimensional jacket structures.These structural systems normally fail as a result of a series of different components failures.The failure characteristics are investigated under various environmental conditions and direction combinations.Theβ-unzipping technique is adopted to determine critical failure components,and the entire system is simplified as a series-parallel system to approximately evaluate the structural system reliability.However,this approach needs excessive computational effort for searching failure components and failure paths.Based on a trained artificial neural network(ANN),which can be used to approximate the implicit limit-state function of a complicated structure,a new alternative procedure is proposed to improve the efficiency of the system reliability analysis method.The failure probability is calculated through Monte Carlo simulation(MCS)with Latin hypercube sampling(LHS).The features and applicability of the above procedure are discussed and compared using an example jacket platform located in Chengdao Oilfield,Bohai Sea,China.This study provides a reference for the evaluation of the system reliability of jacket structures.     

基于ASCAT风场数据的中国近海风能资源评估

卫星反演海面风场资料能够弥补海上气象测风资料缺乏的不足,对近海风能资源评估具有重要意义。通过ASCAT(Advanced Scatterometer)风速数据与美国及中国近海岸浮标测风资料的对比分析,结果表明,ASCAT风速的均方根误差为1.27 m·s-1。比较利用近海岸浮标逐小时风速及与其相匹配ASCAT瞬时风速计算的各项风能参数,得出ASCAT与浮标的平均风速和风功率密度的残差分别在±0.5 m·s-1和±50 W·m-2以内,该残差占浮标计算结果的比例分别在±8%和±12%以内。使用ASCAT风速资料拟合的Weibull分布函数与浮标的结果较吻合。因此,ASCAT风速资料也能够为海上风能资源评估提供有用的风能参数信息。最后使用ASCAT瞬时风速数据分析了中国近海10 m及70 m高度处的风能资源的空间分布特征,结果表明,台湾海峡平均风速和风功率密度最大。