海洋细碎屑沉积物的多向单剪试验

海底陆坡对地震或风暴载荷的响应已经成为海上平台以及当地海啸灾害风险评估的一个重要因素。海底陆坡稳定性评价需要对土体的特性加以描述,而且要选择恰当的参数值。由于海洋沉积物样品的采集非常昂贵,所以海洋沉积物的土工资料很有限。     

温盐深测量平台发展现状与趋势

温度、盐度和压力是海洋重要的基本物理特性参数。温盐深测量仪(Conductivity Temperature Depth,CTD)是海水温盐剖面观测的关键仪器,在海洋经济开发、海洋观测、海洋国防建设方面有着极为重要的意义。本文介绍了几种典型的温盐深测量设备及移动观测平台,重点论述了CTD在Argo浮标、水下滑翔机等海洋移动观测平台上的应用现状,分析了水下滑翔机搭载的CTD在热滞效应、湍流等因素影响下产生的测量误差。最后探讨了以水下滑翔机为代表的海洋移动观测平台搭载CTD测量技术的发展趋势及应用前景。     

“南海挑战号”半潜式平台原型测量系统

深水海洋平台的现场原型监测是对其最直接的研究方法和安全保障措施,是我国深水油气开发研究中的必要技术。为了改变我国缺乏南海半潜式浮体实测经验的现状,为半潜式浮体设计与安全保障提供实测数据支持,在南海LH11-1油田"南海挑战号"半潜式平台上进行了台风期的原型测量工作。原型测量工作采用针对南海浮式平台应用所研发的原型测量系统,对平台工作海域的环境参数、平台姿态以及水下系泊和立管系统进行了监测,获得了跨台风期中大量的实测数据,最终对所获得的数据进行了初步的分析。分析结果显示原型测量系统在海洋平台上使用具有很高的稳定性,捕获了台风期中所有过境平台的台风数据,获得的数据能够为平台性能评价和新平台设计提供第一手资料。     

半潜式平台垂向运动对气隙影响的概率统计分析

应用矩和L矩方法以及二次转换方程,基于模型试验数据的概率统计分析,研究半潜式平台在作业工况和生存工况下的气隙响应,以及平台垂向运动对立柱周围不同位置处的波浪升高和气隙的影响。结果表明,垂向运动总体上能够增加气隙,海况越恶劣,增加程度越明显;在不同浪向下对不同位置的气隙影响有差别,后立柱周围的波浪升高和气隙受平台运动的影响相比前立柱更为显著;同时,平台垂向运动会引起立柱周围波浪升高的非线性增强。     

海洋平台磁流变阻尼器控制技术研究

为了更有效地减小海洋平台动力响应,采用基于模糊控制算法的磁流变阻尼器对海洋平台的振动进行控制.以海洋平台位移响应误差和误差变化为输入变量,以最优控制力为输出变量,优化设计出模糊控制器.考虑实际磁流变阻尼器输出控制力上限存在限制,采用半主动控制算法计算接近于最优控制力的半主动控制力.以一固定式海洋平台为算例研究磁流变阻尼器的振动控制效果及其模糊性,仿真结果表明模糊磁流变控制器对于平台的振动可以实现非常有效的控制,且控制效果对结构阻尼和环境的不确定性具有较好的模糊性.     

振动模态分析法在单立柱海洋平台上应用

提出联合经验模态分解和二次时频分布的参数识别方法.将结构的响应信号用经验模态分解的方法分解为单频率响应的振动信号,进而计算模态频率和模态阻尼,用Choi-Williams分布计算模态振型.对单立柱海洋平台的计算表明,该方法能比较理想地识别出结构的模态参数,且具有较强的抗噪能力.     

Curvature of Flexibility Matrix for Damage Identification in Legs of Jacket Platforms

In this paper a new nondestructive damage identification method is introduced. The method based on flexibility matrix can be used to detect and locate structm＇al damage and evaluate the severity of damage in legs of jacket platforms by modal parameters of a structure. With the modal data for only the few lower modes in both the intact and damaged states, the one-dimensional and two-dimensional distributed curvatures can be used to analyze damage location and the severity. Instead of directly comparing the curvatures before and ＇after damage, the method here uses modal parameters only in the damaged structure to detect the damage and it consists of three parts. First, ilexibility matrix is obtained by use of the absolute maximum in each column. Second, because the legs of jacket platforms are the pipe-like structure, the circumferential flexibility curvature matrix is obtained by use of the circular curvature. At last, equivalent curvature ratio is defined and the curve meaning equivalent curvature ratio and the severity of damage relationship for one element is given through the data of damage severity from ten percent to ninety percent by numerical simulation. Many existing damage detection methods need two steps, locate the damage firstly and evaluate the severity of the damage. However, the method present- ed! in this paper can locate and then evaluate the severity of damage at the same time. The numerical analysis results in- dicate that the present method is effective, useful and only need the first and the second mode data of the structure.     

Modal Identification of Offshore Platforms Using Statistical Method Based on ERA

Identification of modal parameters of a linear structure with output-only measurements has received much attention over the past decodes. In the paper, the Natural Excitation Technique (NEXT) is used for acquisition of the impulse signals from the structural responses. Then Eigensystem Realization Algorithm (ERA) is utilized for modal identification.For disregarding the fictitious ‘computational modes’, a procedure, Statistically Averaging Modal Frequency Method (SAMFM), is developed to distinguish the true modes from noise modes, and to improve the precision of the identified modal frequencies of the structure. An offshore platform is modeled with the finite element method. The theoretical modal parameters are obtained for a comparison with the identified values. The dynamic responses of the platform under random wave loading are computed for providing the output signals used for identification with ERA. Results of simulation demonstrate that the proposed method can determine the system modal frequency with high precision.     

考虑流固耦合时的海洋平台结构非线性动力分析

采用非线性的Morison方程,建立了考虑流固耦合时的海洋平台非线性动力方程及其时程分析方法.以一固定式导管架平台为算例,计算了考虑流固耦合时的海洋平台浪致振动响应,比较了考虑流固耦合和不考虑流固耦合时海洋平台动力响应的差异.算例表明：在较大的波浪条件下,不考虑流固耦合时的计算结果明显小于考虑流固耦合时的计算结果,因此,偏于不安全.分析认为,在极端海况条件下,考虑流固耦合的分析方法更符合实际情况.