深海平台系缆形状和张力分析

考虑海底地形的变化、系缆的拉伸形变及海流力等因素,研究了深海平台系缆形状和张力分析方法采用集中质量法,得到系缆方程组,采用牛顿法求解该非线性系缆方程组,建立系缆形状和张力的计算方法。计算了平坦海底和海底地形凹凸变化时水深1 018 m情况下的系缆形状、系泊张力和浮体平衡位置。计算结果表明,海底地形对于深海系泊系统张力影响较大,而计算系缆形状和张力、系泊浮体的运动时,需要考虑海底地形的影响。     

Extreme response prediction for nonlinear floating offshore structures by Monte Carlo simulation

The paper describes a method for the prediction of extreme response statistics of floating offshore structures subjected to random seas by Monte Carlo simulation. The particular case of the horizontal surge motions of a tension leg platform is considered, taking into account both the first order, wave frequency and the second order, slow-drift motions. The advantage of the Monte Carlo method is its simplicity and versatility, which allows us to account for the effect of time-variant wave-drift damping, as well as nonlinear mooring characteristics without noticeable increase in the computational complexity. It is demonstrated in this paper that the commonly assumed obstacle against using the Monte Carlo method for estimating extreme responses, i.e. excessive CPU time, can be circumvented, bringing the computation time down to quite acceptable levels.     

随机波浪荷载作用下海洋平台的前馈-反馈振动控制研究

该文研究线性前馈 -反馈控制策略对海洋平台振动控制的有效性。线性前馈 -反馈控制只有当输入荷载为白噪声过程时 ,所实施的控制才是最优的 ,因此该文采用一白噪声过程通过滤波器来近似随机波浪力谱 ,并将海洋平台 -主动控制系统的动力学方程转化为符合随机最优控制要求的增广状态空间表达形式。依据设计目标中对安全性以及经济性的权衡 ,通过使二次型控制目标函数最小化 ,推导出了随机最优控制力的计算方法 ,从而实现了最优控制的目的。在频率域上分析了海洋平台受控后的振动响应 ,结合典型的海洋天然气生产平台算例 ,将前馈 -反馈控制与反馈控制、TMD控制加以比较 ,总结了前馈 -反馈控制的特点及其优越性     

一种新型深海海洋平台——几何形Spar和集成浮力桶的试验研究

介绍了一种新型深海海洋平台——几何形Spar壳体概念和集成浮力桶立管支撑概念，并与常规Spar和桁架式Spar进行了比较。为测定多角形Spar和集成浮力桶在不同环境条件下运动响应的总体性能，设计并完成了在海洋工程水池中的模型试验，此类试验在国内尚属首次。     

Damage Localization of Offshore Platforms Under Ambient Excitation

In this paper Nondestructive Damage Detection (NDD) for offshore platforms is investigated under operational conditions. As is known, there is no easy way to measure ambient excitation, so damage detection methods based on ambient excitation have become very vital for the Structural Health Monitoring (SHM) of offshore platforms. The modal parameters (natural frequencies, damping ratios and mode shapes) are identified from structural response data with the Natural Excitation Technique (NExT) in conjunction with the Eigensystem Realization Algorithm (ERA) . A new method of damage detection is presented, which utilizes the invariance property of element modal strain energy. This method is to assign element modal strain energy to two parts, and defines two damage detection indicators. One is compression modal strain energy change ratio (CMSECR); the other is flexural modal strain energy change ratio (FMSECR). The present modal strain energy is obtained by incomplete modal shape and structural stiffness matr     

桶形基础平台海上沉放安装

桶形基础平台是世界上一种最新型的海洋平台，可广泛应用于海上油气田开发。为满足我国际油气田开发中卫星平台的结构和功能要求，桶形基础平台采用新的压载沉放方法安装，具有更高的效率和经济性。沉放过程中桶形基础平台受到水流和波浪的作用，结合模型试验对平台运动进行数值模拟分析，以了解在整个沉放过程中相应参数的变化趋势。根据桶形基础平台的特征，制定联台沉放方案，并通过压载实现平台的沉放控制。     

Numerical Study on the Probability of Fatigue Failure of a Semi-Submerged Platform Structure

On the basis of Miner's linear cumulative damage theorem, random variables are introduced to evaluate objectively the fatigue damage of a semi-submerged platform structure and a method is presented to analyze the fatigue reliability of the structure in its design life. The reliability of the method is verified through numerical examples and some conclusions are drawn, which have certain guiding and reference value for design and inspection.     

导管架海洋平台自振特性的简化计算方法

本文提出了一个方程中只考虑剪切、弯曲、转动惯量效应，而塔架形状变化、平台面转动惯量及台面集中质量变化等其他影响因素均以修正系数方法确定，得出平台基本频率的简化算法。     

A New Method of Surveying Underwater Parts of Self Elevating Drilling Platform

It is a new method of surveying leg spuds of self-elevating drilling platforms to lift them out of water with the help of additional middle guide blocks. Its main advantages in comparison with other methods normally used up to now are: less expensive, time saving, no need for specially designated water area, direct visual observation, good reliability and safety. The working principle has been presented with the example of two platforms "Bohai No. 8" and "Bohai No. 10", to which the method was used. Also a comprehensive comparison with other methods in technological and economical aspects is given in the paper.     

Efficient estimation of extreme response of drag-dominated offshore structures by Monte Carlo simulation

The paper describes a novel approach to the problem of estimating the extreme response statistics of a drag-dominated offshore structure exhibiting a pronounced dynamic behaviour when subjected to harsh weather conditions. It is shown that the key quantity for extreme response prediction is the mean upcrossing rate function, which can be simply extracted from simulated response time histories. A commonly adopted practice for obtaining adequate extremes for design purposes requires the execution of 20 or more 3-h time domain analyses for several extreme sea states. For early phase considerations, it would be convenient if extremes of a reasonable accuracy could be obtained based on shorter and fewer simulations. The aim of the work reported in the present paper has therefore been to develop specific methods which make it possible to extract the necessary information about the extreme response from relatively short time histories.The method proposed in this paper opens up the possibility to predict simply and efficiently both short-term and long-term extreme response statistics. The results presented are based on extensive simulation results for the Kvitebjørn jacket structure, in operation on the Norwegian Continental Shelf. Specifically, deck response time histories for different sea states simulated from an MDOF model were used as the basis for our analyses.