掉层RC框架结构基于典型失效模式的失效概率评估

结构失效模式决定了结构在强震下的抗震性能。该文采用基于可靠度理论的割集方法,对掉层框架结构地震作用下的典型失效模型的失效概率进行评估,并与规则框架结构进行对比,分析了掉层框架结构失效模式的特点。结果表明:掉层框架结构的柱极限剪切失效模式年平均发生概率高于规则结构,且掉层框架结构存在剪切破坏先于弯曲破坏的风险,应采取适当加强措施以满足"强剪弱弯"的设计原则;对掉层结构进行基于年平均概率的柱剪力增大系数分析,建议对掉层结构上接地柱进行抗剪承载力设计时,采用抗震等级提高一级所对应的剪力增大系数,且上接地柱全柱段箍筋应加密布置。     

随机和区间混合变量下结构可靠性分析方法研究

建立了包含随机变量和区间变量的结构功能函数,从失效概率积分式出发,推导出结构失效度为以区间变量为自变量的失效度函数在区间变量域上的均值,进而提出根据区间变量是否相关和问题的精度要求,在区间变量域中按照一定的规则抽取一定量的实现值,将对应的随机失效度的平均值作为结构失效度的近似值,从而形成了随机-区间混合变量下的结构可靠性分析模型。采用Monte Carlo模拟仿真运算,可得到较为精确的分析结果。实例分析验证了该文方法的合理性和可行性,并与其它模型的分析结果进行了比较。     

区间参数杆系结构非概率可靠性指标的改进仿射算法

将杆系结构中的不确定性参数用区间数表示,建立结构的非概率可靠性指标求解方程。将矩阵形式的仿射算术和递归导数信息结合,提出了改进的二元区间多项式矩阵形式的仿射上下界公式。给出了有界不确定性变量的仿射型和区间形式的相互转化,将有界不确定性变量的仿射型及结合导数信息的矩阵形式的仿射运算引入到杆系结构基于区间模型的非概率可靠性指标计算中。分别以某外伸梁和十杆桁架结构为例对该方法的可行性和有效性进行了验证。     

稳态热传导结构非概率可靠性拓扑优化设计

研究具有区间参数的稳态热传导结构在散热弱度非概率可靠性约束下的拓扑优化设计问题。建立了以单元相对导热系数为设计变量,导热材料体积极小化为目标函数,满足散热弱度非概率可靠性为约束条件的稳态热传导结构的拓扑优化设计数学模型。基于区间因子法,推导出散热弱度的均值及离差的计算表达式。采用渐进结构优化法的求解策略与方法,并利用过滤技术消除优化过程中的数值不稳定性现象。通过算例验证文中模型及求解策略、方法的合理性和有效性。     

基于支持向量机的非概率可靠性分析

针对具有隐式极限状态函数的不确定性结构的非概率可靠性分析,提出一种基于支持向量机回归的不确定性结构非概率可靠性分析方法,并给出了该方法的分析流程.抽取数据样本,优化支持向量机回归参数,使用训练后的支持向量机替代隐式极限状态函数.利用非概率集合理论中的区间分析法,引入尺寸比例因子,构造合适的不确定性结构非概率可靠性指标迭...     

非概率可靠性中一维优化算法的改进及其在桥梁评估中应用

为了减少非概率可靠性指标的计算量,提出了改进的一维优化算法.将区间变量转换为标准化区间变量后,得到了关于失效面的极限状态方程.在扩展空间中,通过缩小区间变量的取值范围能方便的确定目标函数的单调性.进一步,为了显示求解非概率可靠性指标的计算过程,提出了非概率可靠性指标的改进一维优化算法的计算步骤.讨论了在役桥梁的非概率可...     

随机区间模糊混合参数结构可靠性分析

研究同时存在随机、区间、模糊变量的混合参数结构可靠性问题。利用广义密度函数法将模糊变量转化为当量随机变量,基于随机概率可靠性分析方法,获得概率可靠度指标表达式。考虑可靠度指标具有的区间性,利用区间数运算法则及区间截断法对所得可靠度指标区间进行计算、重置,获得混合参数结构可靠度区间表达。通过两算例验证该方法的可行性及有效性。     

预应力CFRP加固钢筋混凝土受弯构件的抗力概率模型研究

预应力CFRP 加固混凝土结构技术因其在材料性能利用方面的优越性能已成为CFRP 加固的热点方向,其中预应力CFRP 加固结构的可靠性是这一方向研究的重要内容。该文分析了影响预应力CFRP 板加固钢筋混凝土受弯构件承载力的主要变量的概率特征,考虑CFRP 板尺寸效应和应力分布的影响,采用Weibull 分布推导了CFRP 板的极限强度概率分布函数,根据预应力CFRP 张拉工艺,分析了预应力损失随机变量,建立了在不同失效模式(破坏形态)下的受弯构件抗力概率模型,并开展了参数敏感性分析,获得各个失效模式下抗力概率模型的主要影响因素。研究结果表明:抗力概率模型是预应力CFRP 加固结构的失效概率计算与可靠度校准的重要内容之一,各参数的影响规律与各失效模式的破坏形式密切相关。     

在役腐蚀管道动态非概率可靠性分析简

 腐蚀失效是压力管道失效的主要形式之一,研究腐蚀管道的可靠性具有重要理论意义和应用价值.在对腐蚀管道可靠性分析时,概率可靠性模型和模糊可靠性模型对于数据信息的要求较高.而在掌握不确定性信息很少情况下,为了充分利用管道的不确定性信息弥补原始数据的不足,可将腐蚀管道可靠性分析中的材料屈服强度、管道直径、缺陷深度和操作压力等不确定参数视为区间变量,基于区间模型建立一种在役腐蚀管道动态非概率可靠性模型,给出了腐蚀管道剩余寿命预测的简便方法.结合工程实例计算与分析,表明了文中所提出方法的可行性和合理性,并在此基础上,分析了管道的壁厚、缺陷深度、实际压力和腐蚀速率这些区间变量的不同变异系数对非概率可靠性指标的影响,分析结果表明非概率可靠性指标对管道壁厚的变异系数最为敏感.     

含模糊-区间变量的结构非概率可靠性优化设计

工程结构中存在着诸多不确定性因素,可靠性方法是处理不确定因素的有效途径之一。针对大量工程结构中存在混合不确定信息的问题,提出了一种适用于工程的混合不确定性可靠度计算方法。将模糊变量转化为区间变量,基于体积比的区间可靠性模型,建立了含模糊-区间混合变量的结构非概率可靠性模型。由于该可靠性模型意义明确,对模糊信息的处理也比较合理,可作为混合可靠性计算方法的一种补充。应用此可靠性模型对某飞机机翼结构进行了优化设计,实例计算说明了该文的方法是有效和可行的。     

低周反复荷载下型钢混凝土-钢筋混凝土竖向混合结构转换柱受剪性能试验研究

为了研究型钢混凝土-钢筋混凝土竖向混合结构转换柱的受剪性能,对16个转换柱试件和1个钢筋混凝土柱对比试件进行了低周反复荷载试验。分析了转换柱试件的破坏形态,研究了其位移延性、承载能力、强度衰减,以及耗能能力等方面的力学性能,并与钢筋混凝土柱试件进行了对比。试验结果表明:转换柱的破坏形态可以分为剪切破坏、粘结破坏和弯曲破坏;转换柱中钢与混凝土之间的相互作用方式导致了其特殊的破坏特征;发生粘结破坏和弯曲破坏的试件,其最大承载力之后的强度衰减较大;转换柱的耗能能力介于型钢混凝土柱与钢筋混凝土柱之间。绝大多数转换柱试件的延性性能能够满足位移延性系数大于3的抗震设防要求。     

Hyperstatic and redundancy thresholds in truss topology optimization considering progressive collapse due to aleatory and epistemic uncertainties

Optimization leads to specialized structures which are not robust to disturbance events like unanticipated abnormal loading or human errors. Typical reliability-based and robust optimization mainly address objective aleatory uncertainties. To date, the impact of subjective epistemic uncertainties in optimal design has not been comprehensively investigated. In this paper, we use an independent parameter to investigate the effects of epistemic uncertainties in optimal design: the latent failure probability. Reliability-based and risk-based truss topology optimization are addressed. It is shown that optimal risk-based designs can be divided in three groups: (A) when epistemic uncertainty is small (in comparison to aleatory uncertainty), the optimal design is indifferent to it and yields isostatic structures; (B) when aleatory and epistemic uncertainties are relevant, optimal design is controlled by epistemic uncertainty and yields hyperstatic but nonredundant structures, for which expected costs of direct collapse are controlled; (C) when epistemic uncertainty becomes too large, the optimal design becomes redundant, as a way to control increasing expected costs of collapse. The three regions above are divided by hyperstatic and redundancy thresholds. The redundancy threshold is the point where the structure needs to become redundant so that its reliability becomes larger than the latent reliability of the simplest isostatic system. Simple truss topology optimization is considered herein, but the conclusions have immediate relevance to the optimal design of realistic structures subject to aleatory and epistemic uncertainties.     

CFRP复合材料螺栓连接失效载荷不确定性的评估方法

螺栓连接是先进复合材料结构的薄弱环节.因此,螺栓连接力学性能显著的不确定性不仅阻碍了先进复合材料的高效应用,且给整体结构的安全性和可靠性带来威胁.为定量评估碳纤维增强树脂(CFRP)复合材料螺栓连接失效载荷的不确定性,将数值的渐进损伤模型和区间分析方法结合,提出了一种高效、准确的分析方法.采用该方法预测了典型T800碳...     

Research on multiple-state industrial robot system with epistemic uncertainty reliability allocation method

Reliability allocation of industrial robot (IR) system is one of the important means to improve its whole life cycle, reduce maintenance cost, and characterize weak subsystems. The IR system is not only very complex but also has strong customization; meanwhile, its sample data are small, resulting in unclear degeneration and failure. Based on the above two epistemic uncertainties, a new methodology called multiple-state IR system reliability allocation method with epistemic uncertainty (MIRS-RAM-EU) is proposed. First, the Dempster-Shafer (D-S) evidence theory is used to quantify the epistemic uncertainty. Then, the Kolmogorov differential equations of MIR's subsystems are calculated. The reliability index of MIRS is allocated based on Birnbaum importance degree theory, and the reliability allocation coefficient of each IR subsystem is clearly expressed by this method. Finally, compared with traditional importance allocation method, the MIRS-RAM-EU is more efficient and accurate. This method is usefully directive for reliability evaluation of IR.     

Verification of the calculation of probability of loss of assured safety in temperature-dependent systems with multiple weak and strong links

Two approaches to the calculation of probability of loss of assured safety (PLOAS) in temperature dependent weak link/strong link systems are described and compared on the basis of three test problems. The approaches differ in that the first approach permits a separation of epistemic and aleatory uncertainty in the calculation of PLOAS and the second approach combines epistemic and aleatory uncertainty before the calculation of PLOAS. A discrepancy in the results obtained with the test problems led to the identification of an implementation error for one of the approaches. The importance and efficacy of well-designed verification test problems are demonstrated.     

带加劲肋腹板开洞组合梁极限承载力理论研究

基于空腹桁架破坏机理,根据腹板开洞组合梁在极限状态下的洞口区域塑性应力分布建立洞口4个次弯矩函数。提出了一种带加劲肋腹板开洞组合梁极限承载力的计算方法,该方法考虑了洞口上方混凝土板对组合梁的竖向抗剪承载力的贡献。计算结果表明:洞口设置加劲板能有效的提高腹板开洞组合梁的抗弯和竖向抗剪承载力,而且竖向抗剪承载力随着加劲板面积的增大而增大,混凝土板对组合梁的抗剪承载力有较大的贡献。并与试验和有限元结果进行了比较,结果吻合较好,算例验证了该计算方法的准确性和可靠性。     

Integration of computation and testing for reliability estimation

This paper develops a methodology to integrate reliability testing and computational reliability analysis for product development. The presence of information uncertainty such as statistical uncertainty and modeling error is incorporated. The integration of testing and computation leads to a more cost-efficient estimation of failure probability and life distribution than the tests-only approach currently followed by the industry. A Bayesian procedure is proposed to quantify the modeling uncertainty using random parameters, including the uncertainty in mechanical and statistical model selection and the uncertainty in distribution parameters. An adaptive method is developed to determine the number of tests needed to achieve a desired confidence level in the reliability estimates, by combining prior computational prediction and test data. Two kinds of tests — failure probability estimation and life estimation — are considered. The prior distribution and confidence interval of failure probability in both cases are estimated using computational reliability methods, and are updated using the results of tests performed during the product development phase.     

Quantification of margins and uncertainties: Alternative representations of epistemic uncertainty

In 2001, the National Nuclear Security Administration of the U.S. Department of Energy in conjunction with the national security laboratories (i.e., Los Alamos National Laboratory, Lawrence Livermore National Laboratory and Sandia National Laboratories) initiated development of a process designated Quantification of Margins and Uncertainties (QMU) for the use of risk assessment methodologies in the certification of the reliability and safety of the nation's nuclear weapons stockpile. A previous presentation, “Quantification of Margins and Uncertainties: Conceptual and Computational Basis,” describes the basic ideas that underlie QMU and illustrates these ideas with two notional examples that employ probability for the representation of aleatory and epistemic uncertainty. The current presentation introduces and illustrates the use of interval analysis, possibility theory and evidence theory as alternatives to the use of probability theory for the representation of epistemic uncertainty in QMU-type analyses. The following topics are considered: the mathematical structure of alternative representations of uncertainty, alternative representations of epistemic uncertainty in QMU analyses involving only epistemic uncertainty, and alternative representations of epistemic uncertainty in QMU analyses involving a separation of aleatory and epistemic uncertainty. Analyses involving interval analysis, possibility theory and evidence theory are illustrated with the same two notional examples used in the presentation indicated above to illustrate the use of probability to represent aleatory and epistemic uncertainty in QMU analyses.     

简支矩形深受弯箱梁静力性能试验研究

由于城市土地用途改变,冲沟回填筑路,原架空箱涵被掩埋并承受较大的附加土压力和车辆荷载,荷载工况的改变导致管道结构存在破坏风险。对山地城市排水干管常见的深受弯钢筋混凝土架空箱梁进行了模型静力加载试验,分析了此类箱梁的破坏形式、剪力滞效应和抗剪性能,讨论了现行有关设计规范对于箱涵抗弯承载力计算之不足,并对箱梁进行了非线性有限元模拟分析。研究表明:竖向均布荷载作用下,跨高比接近5的简支矩形深受弯箱梁的最终破坏为弯曲破坏。跨中截面无明显剪力滞现象,开裂前1/4跨截面剪力滞效应较明显,开裂后剪力滞效应逐渐削弱。箍筋作为主要的抗剪部件,在斜裂缝出现后承担着大部分剪力。非线性有限元模拟结果与试验结果吻合较好。对于按简支结构设计的排水箱涵在回填前应进行加固措施,避免排水箱涵过早开裂,影响管道的正常使用。