驳船载导管架拖航及下水工况中的结构强度分析

根据相关规范,应用ANSYS有限元软件对上海船舶研究设计院的导管架拖航/下水驳船的设计方案进行了结构强度的有限元分析.为取得可靠的计算精度,对导管架、滑道和驳船均进行了精确的有限元建模,对该设计方案进行了多工况的应力和变形的计算,给出了有限元模型建立过程中单元的选取、网格剖分以及约束和载荷的处理方法,并对计算结果进行了分析,从而提出了结构改进建议和作业环境要求.本文的研究成果为驳船的设计及结构强度分析提供了参考方法.     

近海结构疲劳计算中波浪与结构建模探讨

文章根据作者已提出的基于海况频度分布的统计分类及非线性动力学计算的疲劳评估方法,通过进一步改进波浪能的输入,提出了一种更为有效的计算方法。通过将这一方法运用到一典型导管架结构的疲劳计算,文中首先研究了波浪方向对疲劳破坏的影响,进而分析了波浪谱中若干重要参数及HHT-α时间积分中步长对疲劳计算结果的影响。通过对结构反应的统计研究,发现海况的恶劣程度并不直接影响结构响应非高斯趋势的显著程度。文中提出的方法在减少不确定性的同时又不降低安全标准,有效提高了疲劳计算的精确度,从而可以降低相关近海结构建设和维护成本。文中的计算方法已被成功地应用于北海及墨西哥湾数座近海结构在风和波浪荷载作用下的疲劳评估。     

南海固定式平台极限承载能力分析

针对南海海域环境荷载下服役的固定式平台,以一固定式导管架平台为例,运用基于ANSYS软件的单元替换法分析计算该平台无缺陷情况下和有腐蚀、海生物附着、构件缺失等损伤情况下的极限承载能力,验证了计算正确性和可行性.     

导管架滑移下水强度智能分析技术研究

针对传统导管架滑移下水强度分析时手动分析方法费时费力的问题,介绍一套导管架滑移下水的强度智能分析方法,包括导管架下水分析的基本理论和假定,分析自动化和智能化技术的实现原理和思路以及交互软件的开发框架和方法。该方法在荔湾3-1及后续项目中得到成功推广和应用,能大幅度地提高分析效率,缩短分析时间。     

Finite Element Simplified Fatigue Analysis Method for a Non-tubular Joint of an Offshore Jacket Platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analys...     

Finite element simplified fatigue analysis method for a non-tubular joint of an offshore jacket platform

This paper proposes the finite element simplified fatigue analysis method for fatigue evaluation of the composite non-tubular joint structure of an offshore jacket subjected to wave loads. The skirt pile sleeve of the offshore jacket, which had been in service, was taken as an example of the non-tubular joint structure. SACS software was used for global analysis of multi-directional wave loads for the jacket platform, and ALGOR software was used to build a finite element model, perform finite element analysis, post-process stress results for acquiring the stress range, and perform fatigue evaluation. The analysis results indicate that the extreme stress range is within the allowable stress range and meets the requirements of DNV code. That means the simplified fatigue analysis method is effective and can be used in fatigue design for the non-tubular joint structure of an offshore jacket.     

T型导管架下水驳船设计建造过程中的控制要点

在海洋油气的开发中,下水驳船承担着大型结构物(如导管架、组块等)的装载、运输、下水和安装等角色,尤其是超大型导管架(例如荔湾3-1项目32 000 t导管架)的滑移下水,更是下水驳船所独有的功能。该文重点从导管架下水设计的角度出发,以18 000 t T型导管架下水驳船为例,介绍了在设计和建造此类下水驳船中,需要控制的一些技术要点,从而为今后同类船舶的设计建造提供借鉴。     

Damage detection in offshore structures using neural networks

This paper discusses the damage detection in offshore jacket platforms subjected to random loads using a combined method of random decrement signature and neural networks. The random decrement technique is used to extract the free decay of the structure from its online response while the structure is in service. The free decay and its time derivative are used as input for a neural network. The output of the neural network is used as an index for damage detection. It has been shown that function N is effective in damage detection in the members of an offshore structure. Experimental studies conducted on a reduced model for a real jacket structure with geometrical scale of 1:30 are used. The applied loads were random loads. Two different load spectra were used: White noise, and Pierson-Moskowitz.     

三类边界条件下隔水套管涡激非线性振动的分析研究

考虑流及波流联合作用,研究了套管的涡激非线性振动.将套管简化为梁模型,考虑3类不同的边界条件,计及莫里森非线性流体动力和涡激荷载,建立套管的涡激振动方程.应用克雷洛夫函数求解套管的固有频率和模态,采用了计算涡激非线性动力响应的迦辽金方法.以东海勘探3号钻井隔水套管为例,研究了不同边界条件下流引起的主共振和波流联合引起的组合共振.计算结果表明:流对套管的动力响应占主导地位,而波的影响不大.分析了3类不同边界条件下隔水套管的涡激非线性动力响应,揭示了波流联合激励下套管复杂的动力响应特性.     

导管架下水过程的理论计算和模型试验

上海交通大学船舶流体力学研究室新近对导管架下水过程的理论计算和模型试验进行了开发性研究。文中采用直角坐标和Euler角描述导管架和驳船系统的空间状态,将约束方程的二次微分形式与动量(矩)方程联立,建立了下水过程的三维运动方程,用Runge-Kutta法求其数值解。文中选了一个二维运动的侧子进行计算,并与试验结果作了比较,符合程度良好。     

船舶纵向下水试验及支座反力的计算

本文给出了Ａ、Ｂ两船纵向下水的试验结果及支座反力的计算方法，计算结果与试验结果相当吻合，可在校该核纵向下船舶强度时用于确定载荷。     

显式和隐式方法求解防波堤可靠度的差异分析

半圆形防波堤具有稳定性高、结构简单、便于施工等优点。以往对其进行可靠度计算时,根据波高与周期,计算防波堤受到的荷载作用,将荷载作为随机变量,估计其概率分布模型,建立显式的极限状态方程,再进行求解。计算得到的波浪荷载序列对于最优分布线型的离散程度较差。采用基于隐式功能函数的防波堤可靠度分析方法,将波高和周期作为随机变量,无需计算波浪荷载这一中间序列,规避了误差的产生,简化了计算流程。分别采用隐式与显式两种方法对半圆形防波堤进行了可靠性分析。结果表明,两种方法得出的可靠度指标存在差异,这种差异是由于波浪荷载拟合时所产生的误差造成的。     

Analysis of unsteady flow over Offshore Wind Turbine in combination with different types of foundations

Environmental effects have an important influence on Offshore Wind Turbine (OWT) power generation efficiency and the structural stability of such turbines. In this study, we use an in-house Boundary Element (BEM)—panMARE code—to simulate the unsteady flow behavior of a full OWT with various combinations of aerodynamic and hydrodynamic loads in the time domain. This code is implemented to simulate potential flows for different applications and is based on a three-dimensional first-order panel method. Three different OWT configurations consisting of a generic 5 MW NREL rotor with three different types of foundations (Monopile, Tripod, and Jacket) are investigated. These three configurations are analyzed using the RANSE solver which is carried out using ANSYS CFX for validating the corresponding results. The simulations are performed under the same environmental atmospheric wind shear and rotor angular velocity, and the wave properties are wave height of 4 m and wave period of 7.16 s. In the present work, wave environmental effects were investigated firstly for the two solvers, and good agreement is achieved. Moreover, pressure distribution in each OWT case is presented, including detailed information about local flow fields. The time history of the forces at inflow direction and its moments around the mudline at each OWT part are presented in a dimensionless form with respect to the mean value of the last three loads and the moment amplitudes obtained from the BEM code, where the contribution of rotor force is lower in the tripod case and higher in the jacket case and the calculated hydrodynamic load that effect on jacket foundation type is lower than other two cases.     

导管架下水驳船简介

导管架下水驳是一种专门用来进行导管架运输和下水的驳船,目前世界上只有少数国家具有导管架下水工程船的设计、建造能力,关键的技术资料很少.文章描述了导管架下水驳的船型及特点,并对船体主尺度的确定,结构强度,稳性,下水及主要特种下水装置做了简要的介绍,供大家参考.     

随机波浪载荷作用下导管架平台动力响应及疲劳可靠性分析

主要针对波浪载荷作用下导管架式海洋平台结构的疲劳可靠性进行研究.采用Airy线性波浪理论,将导管架结构离散成空间梁有限单元结构;在此基础上采用结构模态分析方法,编程计算了平台结构在随机波浪载荷作用下的位移、速度、加速度和应力随机响应及其概率统计量.导管架结构疲劳可靠性分析建立在频域响应的基础上,假设结构响应的应力范围服从Rayleigh分布,利用结构应力传递函数得到结构应力响应谱,然后利用Miner线性累积损伤准则推导出结构疲劳寿命的概率分布函数,并考虑结构疲劳强度影响系数的随机性,求得结构在随机应力谱下给定疲劳寿命时的疲劳可靠性指标.文中所建立方法可用于导管架式平台结构的疲劳安全评估.     

基于灰预测和粗神经网络的海洋平台逆控制研究

导管架式海洋平台在随机波浪等外载荷作用下极易产生有害振动,且其动力响应具有极强的非线性和时变性,采用被动控制方法和基于精确数学模型的主动控制方法控制海洋平台的有害振动很难达到理想的控制效果.为此文中将灰预测和粗神经网络相结合,提出了一种基于灰预测和粗神经网络的预测逆控制方法,并将其与动态刚度阵法相结合用于导管架式海洋平台的振动主动控制中.数值算例分析表明此种控制方法可有效地控制波浪和风载荷作用而引起的导管架式平台的有害振动,并能解决由于控制信号传输等原因引起的时滞问题.     

Experimental study on responses of an 8-module VLFS considering different encounter wave conditions

For the very large floating structure (VLFS) which is deployed near seashores, islands and reefs, the encounter wave conditions are always extremely complex. Traditional methods using homogeneous wave environment conditions cannot be applied for the analysis. In order to provide references for the further development of numerical methods, this paper reports an experimental study on responses of an 8-module VLFS under three different encounter wave conditions. The wave heights, accelerations, motions and connector loads of VLFS in three test schemes are obtained and analyzed. The comparative results show that the inhomogeneous wave conditions have an essential influence on the responses of VLFS. Especially for the connector loads, the values in the inhomogeneous wave conditions increase a lot compared with the other two test schemes. It indicates the traditional numerical methods using homogeneous wave field may not guarantee a safe design of VLFS and its connectors in the complicated wave environments.     

限制水域船舶纵向下水的动力学分析

为了对限制水域内船舶纵向下水运动进行完整而准确的预报,考虑兴波阻力、粘性阻力、锚链力、钢缆力、水流力、横向侧推力的动力效应以及不对称水域等因素对下水运动的影响,针对下水各阶段建立了船体运动模型,提出了一种较为完善的限制水域内下水运动理论计算方法.采用该方法对一艘45000吨化学品/成品油轮的下水运动进行了预报,并与实船下水测试结果进行了比较分析.结果表明,此方法可以较好地模拟船舶下水运动,为分析和判断船舶下水的安全性提供了依据.