Reliability Analysis for Offshore Platform Structural Systems

A system reliability estimation method for spatial jacket platforms is developed in this paper. The jacket platform is modeled into three-dimensional assembly of spatial beam and plate elements in Finite Element Method (FEM). The limit failure states correspond to collapse of a series of structural members which are identified by engineering design criteria. In this paper the following aspects are taken into account: the punching shear and buckling failures in member failure modes for the tubular joints and tubular columns respectively; incremental loading approach for establishment of the safety margin equations of system failure; the algorithm of enumerating significant failure modes for the structural systems and other concepts, such as the false failure mode and the virtual limit state. The final work is devoted to the reliability analysis for a practical jacket platform presently put into operation on the Bohai Sea. The computed results shows that method suggested in this paper is feasible and effective for the evaluation of the system reliability of offshore platforms.

Structural Interval Reliability Algorithm Based on Bernstein Polynomials and Evidence Theory

Structural reliability is an important method to measure the safety performance of structures under the influence of uncertain factors.Traditional structural reliability analysis methods often convert the limit state function to the polynomial form to measure whether the structure is invalid.The uncertain parameters mainly exist in the form of intervals.This method requires a lot of calculation and is often difficult to achieve efficiently.In order to solve this problem,this paper proposes an interval variable multivariate polynomial algorithm based on Bernstein polynomials and evidence theory to solve the structural reliability problem with cognitive uncertainty.Based on the non-probabilistic reliability index method,the extreme value of the limit state function is obtained using the properties of Bernstein polynomials,thus avoiding the need for a lot of sampling to solve the reliability analysis problem.The method is applied to numerical examples and engineering applications such as experiments,and the results show that the method has higher computational efficiency and accuracy than the traditional linear approximation method,especially for some reliability problems with higher nonlinearity.Moreover,this method can effectively improve the reliability of results and reduce the cost of calculation in practical engineering problems.

Matrix description of differential relations of moment functions in structural reliability sensitivity analysis

In a structural system reliability analysis that lacks probabilistic information, calculating the numerical characteristics of the state functions, especially the first four moments of the state functions, is necessary. Based on that, the structural system reliability is analyzed with a fourth-order moment method. The reliability sensitivity is required to conduct the differential operation of the numerical characteristic functions. A reliability sensitivity analysis formula is then derived in combination with the relation of the differential operation. Based on the matrix theory and Kronecker algebra, this paper systematically derives a matrix expression of the first four moments of the state functions, and establishes the matrix relation between the first four moments of the state functions and those of the basic random variables. On this basis, a differential operation formula of the first four moments of the state functions is further derived against the first four moments of the basic random variables. The vector relation between the state functions and the multidimensional basic random variables is described by means of the matrix operation to extend the operation method. Finally, a concise and intuitive formula is obtained to explore the inherent essential relation between the numerical characteristics of the state functions and those of the basic random variables, leading to a universal equation for the two kinds of numerical characteristics.

Analysis of Reliability for 3-State Device Network with Link-Capacities

This paper presents a concept of the 3-state device system with link-capacity, whichcan, besides its normal operative state, assume two different failure states: an open-mode and ashorted-mode failure state. The 3-state system reliability analysis often uses flow required andprobability of the device to compute the probability of the system with link-capacity. We use themethod of max-flow and min-cut theorem, give four theorems to reduce 3-state device network withlink-capacity reliability problems to 2-state problems. For practical, relevant network sizes (up to100 components), the algorithm is fast and efficient.

OPTIMUM DESIGN BASED ON RELIABILITY IN STOCHASTIC STRUCTURE SYSTEMS

The optimum design method based on the reliability is presented to the stochastic structure systems （i. e., the sectional area, length, elastic module and strength of the structural member are random variables ） under the random loads. The sensitivity expression of system reliability index and the safety margins were presented in the stochastic structure systems. The optimum vector method was given. First, the expressions of the reliability index of the safety margins with the improved first-order second-moment and the stochastic finite element method were deduced, and then the expressions of the systemic failure probability by probabilistic network evaluation technique（PNET） method were obtained. After derivation calculus ,the expressions of the sensitivity analysis for the system reliability were obtained. Moreover, the optimum design with the optimum vector algorithm was undertaken. In the optimum iterative procedure, the gradient step and the optimum vector step were adopted to calculate. At the last, a numerical example was provided to illustrate that the method is efficient in the calculation, stably converges and fits the application in engineering.

理论驱动的弹性结构体系图神经网络计算模型

该文提出了一个理论驱动的弹性结构体系图神经网络计算模型StructGNN-E,能够高保真数字化结构体系的拓扑连接关系与构件组成信息,无需外部标签数据即可实现对任意杆系结构体系的弹性内力分析,且计算结果具有理论正确性。总结了结构体系层次的特点,理论分析了常规神经网络的不可行性,进而采用了基于非欧图数据的图神经网络架构,能够有效刻画结构体系的非序列性与非平移不变性。考虑到体系层次数据严重匮乏以及常规智能计算方法忽视力学意义的问题,通过将三大力学方程与深度学习推理过程相结合,提出了适用于体系内力分析的理论驱动模式,实现了不依赖于外部标签数据的智能求解方案。数值试验表明:StructGNN-E模型能够高精度完成杆系结构体系的弹性内力分析,且在大规模框架结构计算中计算效率提升可达36%。通过具体的对比试验,证明了常规深度学习模型与数据驱动模式在体系层次的不适用性,进一步阐释了StructGNN-E模型的有效性与合理性。

基于有限退化结构的多态组合导航系统可靠性

组合导航系统(integrated navigation system,INS)广泛用于航空航天、海洋探索等领域,因其工作环境、系统构成的复杂性等因素,系统从正常工作到完全失效会经历各种退化状态,进而增加系统可靠性分析难度。将有限退化结构(finite degradation structures,FDS)方法应用于多态组合导航系统可靠性分析。首先,参考故障模式与影响分析(failure mode and effect analysis,FMEA)方法将组件的故障模式转化为状态空间;其次,利用抽象运算得到组件状态和系统状态的关联关系,建立组合导航系统的FDS模型;然后,进行系统临界场景分析和可靠性指标计算,得出系统状态的发生概率、组件状态的敏感性,找到系统的薄弱环节、系统完全失效前的退化边界;最后,根据结果指导制定系统维护策略、预防系统风险发生方案等可靠性决策。

STPA和CREAM方法在飞行冲突调配人因差错研究中的应用

为了研究管制员飞行冲突调配的人因差错问题,进而有效评估管制员解决飞行冲突的可靠性,以保障空中交通的安全运行,提出系统理论过程分析(System Theoretic Process Analysis, STPA)与认知可靠性与失误分析方法(Cognitive Reliability and Error Analysis Method, CREAM)相结合的人因可靠性分析方法。首先,通过STPA方法构建系统控制模型,识别不安全控制行为(Unsafe Control Action, UCA)以及致因因素,找到管制员在调配飞行冲突过程中可能存在的差错行为;其次,基于CREAM扩展法对管制员的差错行为进行定量分析,得到管制员调配飞行冲突的人因失误概率。研究显示:使用该方法能够系统、全面地识别出管制员在调配飞行冲突过程中出现的差错行为,进而计算管制员飞行冲突调配的人因失误概率。实例分析表明该方法可以预测管制员在飞行冲突调配过程中的人因失误概率及可靠性,为管制员人因可靠性分析提供了新思路。

Progress in Theoretical Research on Reliability for China's Space Engineering

With the support of the Fundamental Reliability Theoretical Research (FRTR) Foundation of the Quality Control Bureau of Ministry of Astronautics (MOA), PRC, 9 Chinese institutes and universities have worked for years on reliability statistics problems pending to be solved in space research and development. This paper gives a brief review of our main research results, including (1) Results on Normal Distributions; (2) Results on Weibull Distributions; (3) Results on the Synthesisof System Reliability-Theoretical Method; (4) Results on the Synthesis of System Reliability-Approximation Method: Binomial Distribution, Exponential Distribution, Weibull Distribution, Parallel System, General Cases; (5) Structual Reliability; (6) Zero-Failure Reliability Estimation; (7) Storage Life and Others. All these results can be acquired from the Quality Control Bureau of the Ministry of Aero-Space Industry (MAS).

基于电动汽车分群的“风-网-站-车”体系调度研究

根据车型、充电方式2大特征对电动汽车分群,通过概率论与数理统计,推导出BEV相关系数指标,用来体现充电负荷之间的关系紧密程度,以此作为优化调度的依据。建立基于BEV分群优化方法的“风网站车”体系调度模型,以BEV用户满意度、电网稳定性最大为目标,并进行加权求和。其次研究基于可信性理论的模糊机会约束,对风电机组出力和电动汽车负荷这2个不确定变量进行清晰化等价处理。最终根据基础数据对模型进行对比分析、灵敏度分析,表明所提方法既保证了BEV用户的满意度以及电网稳定性,又提高了风电消纳的能力。

多失效模式下基于区间非概率的岩质隧道稳定可靠度分析

对于岩质隧道工程的稳定可靠度分析,一方面由于岩体参数的统计数据获取困难使得概率可靠度方法难以适用,另一方面其工程稳定与多种失效模式密切相关,须考虑隧道结构体系的可靠度问题。首先,基于区间理论,通过区间变量形式表征不确定性参数;然后,针对岩质隧道工程中多种失效模式并存的情况,引入结构体系可靠度理念,建立基于区间非概率的岩质隧道结构体系可靠度指标计算及其稳定性评价方法;在此基础上,通过工程实例验证了该方法的合理性;最后,定义不确定性参数的波动幅度,进一步分析各失效模式中不同参数对相应可靠度指标以及结构体系可靠度指标的影响。分析结果表明,各失效模式相应的非概率可靠度指标均随区间变量范围的增大而降低,且同一参数在不同失效模式中表现出不同的影响;另外,不确定性参数的变化还将导致影响岩质隧道结构体系稳定的主要失效模式发生相应的变化。

基于GT-RBD的电力系统可靠性分析方法

针对现有电力系统可靠性评估方法均存在一定的局限性,难以从总体上对系统可靠性进行分析的问题,提出了一种新型电力系统可靠性分析方法.通过引入图论确定线路和节点的状态,并根据节点的可靠性程度对给定的设备组合进行分类.采用可靠性框图评估每一节点的可靠性,并通过在MATLAB中搭建IEEE-9节点系统验证方法的有效性.结果表明,提出的方法可以较好地应用于IEEE-9节点系统中,能够将线路中的节点可靠性进行排序,其准确率可达97.16%,实现了电力系统的安全性和可靠性的有效分析.

基于网络流与危险与可操作性分析的天然气站场系统可靠性

为了更全面、准确地分析天然气站场的系统整体可靠性,提出采用跨领域的网络流理论来分析天然气站场系统的整体可靠性,并对网络流理论做了归纳创新与适应性分析,通过最小路集与不交化算法计算出站场系统在正常工艺状态下的失效概率,然后创新性地提出基于危险与可操作性分析(hazard and operability analysis,HAZOP)确定站场系统在工艺参数偏差状态下的失效概率,分析偏差状态对于站场系统可靠性的影响,将其与正常工艺状态下的站场系统失效概率对比,从而更加全面地分析天然气站场系统的整体可靠性。结果表明:所提出的网络流分步法比网络流整体法分析站场系统的可靠性适应性更强,网络流分步法不存在必要通路不在最小路集内的问题,既能保证连通性又能保证满足工艺要求;正常工艺状态下该站的系统失效概率为4.9869×10^(-2),工艺参数偏差状态下该站的系统失效概率为5.8036×10^(-2),较正常工艺状态增大16.38%,两种状态下各子系统的失效概率数量级没有改变,大小排序也没有改变,因此该工艺参数偏差状态下建议各子系统排序不变,但对于各子系统中的设备需按各自失效概率增大的程度进行重点关注的调整,这对于天然气站场的实际生产运行与安全运行管理具有一定的指导意义。

一种基于证据理论的结构可靠性分析方法

提出了一种基于证据理论的结构可靠性高效求解方法.通过构造优化问题求解极限状态方程的非概率可靠性指标及设计验算点,并构造一辅助区域.通过辅助区域显著减少需要进行极值分析的焦元个数,并基于区间分析方法减少焦元上极限状态方程的计算次数,从而有效降低计算成本.数值算例及工程应用验证了该方法的有效性.

铁路接触网系统的Markov分析

根据接触网的可修特性,采用马尔可夫(Markov)理论和数理统计的原理,建立了接触网可靠性分析的数学模型,推导出了接触网系统的稳态有效度、可靠度和平均故障间隔时间等重要特征量的计算公式.用此模型对宝成线的可靠性进行了预测和分析,在同国外接触网系统的可靠性进行比较的基础上,提出了提高我国接触网系统可利用度的有效措施.为铁路系统的可靠性设计、维护和科学管理提供了理论依据和新的方法.

地下管道动力可靠性分析的降维计算方法

地下管道是城市重要的基础工程之一,对其进行的地震作用下的可靠性分析是地下管道安全性的重要指标.但传统的可靠性分析只是针对单根管道进行分析与实际情况存在一定差异.本文采用系统可靠性理论对地震作用下的地下管线动力可靠性进行分析,并针对系统可靠性计算量大的难题,引入了PNET法(point evaluation technique)与谱系聚类分析法两种降维方法,在保证精度的同时大大提高了计算效率,使对地下管线的系统可靠性分析达到实用化程度.最后还结合实例进行了系统可靠性计算并对两种降维方法做了比较分析,提出了相应改进措施.

基于Copula理论的风光互补发电系统可靠性评估

提出应用Copula理论建立风电场、光伏电站出力联合概率分布模型的方法。该方法不仅考虑了风电场、光伏电站出力的随机性,并且计及两者出力的相关性。根据某风光互补电站的实测出力数据,采用非参数核密度估计法,估计风电场、光伏电站出力的概率分布。选取Kendall秩相关系数作为风电场、光伏电站出力的相关性测度。利用Frank Copula函数,计算风电场、光伏电站出力的联合概率分布。以RBTS标准测试系统作为算例,对风光互补发电系统进行可靠性评估,结果表明:建立的模型能够较好地描述风光互补发电系统出力的概率特性,且考虑相关性的可靠性评估更接近实际情况。

基于可信性理论的电气化铁路接触网可靠性的模糊评估

首先基于故障树分析法建立了接触网系统的可靠性模型,在大量调研和统计分析的基础上,用梯形模糊变量描述接触线、承力索和绝缘子的故障率和修复率,用三角形模糊变量描述接触网其他部件的故障率和修复率,将接触网系统的故障率、修复率和可用度等可靠性指标视为随机模糊函数,利用可信度理论实现了接触网可靠性的模糊评估。计算结果表明,只要掌握各部件故障率和修复率的大致分布,就可以较准确地计算接触网系统的可靠性指标,误差满足工程精度的要求。

基于脆性理论的多状态制造系统可靠性分析

针对传统制造系统可靠性分析方法的不足,将复杂系统脆性理论与多状态制造系统理论相结合,提出一种基于脆性理论的多状态制造系统可靠性分析方法。研究了制造系统多态性的产生机理与脆性激发机理,从加工过程、人员、环境三个方面构建了脆性激发因素集以及三方面因素之间的相互耦合关系,并给出各脆性激发因素风险度、耦合度与脆性度的量化方法;引入状态空间模型,描述了脆性效应作用下多状态制造系统的状态演变过程,在此基础上建立多状态制造系统的状态演变模型;提出一种考虑脆性效应的改进通用生成函数法,分别定义了多状态制造系统及其设备单元的生成函数,对多状态制造系统的工作性能状态与实际稳态可靠度等指标进行了分析。以国内某制造企业的双缸体零件族制造系统为例,证明了所提方法的可用性与有效性。

基于可靠性理论的事件树分析方法研究

事件树分析过程中事件树的编制和分析方法缺乏系统性,导致实际运用中事件树的编制缺乏可操作性。从目标系统的选择、环节事件逻辑关系的确定、定量分析中基本数据的来源和确定方法等三个问题进行了系统研究,并以可靠性的相关理论为基础,提出"从控制和影响初始事件发展演化的角度,调查分析对初始事件做出响应的安全功能,按系统工作原理对目标系统进行重构,构建目标系统的功能结构图,画出系统的可靠性框图"入手,对"传统的事件树绘制程序"进行修正,解决了事件树分析过程中目标系统的选择、环节事件逻辑关系的确定以及定量分析基本数据的确定方法等问题。修正后的方案对实现事件树的正确编制和系统分析逻辑更清晰,操作指导性更强。