A novel refined dynamic model of high-speed maglev train-bridge coupled system for random vibration and running safety assessment

Running safety assessment and tracking irregularity parametric sensitivity analysis of high-speed maglev train-bridge system are of great concern,especially need perfect refinement models in which all properties can be well characterized based on various stochastic excitations.A three-dimensional refined spatial random vibration analysis model of high-speed maglev train-bridge coupled system is established in this paper,in which multi-source uncertainty excitation can be considered simultaneously,and the probability density evolution method(PDEM)is adopted to reveal the system-specific uncertainty dynamic characteristic.The motion equation of the maglev vehicle model is composed of multi-rigid bodies with a total 210-degrees of freedom for each vehicle,and a refined electromagnetic force-air gap model is used to account for the interaction and coupling effect between the moving train and track beam bridges,which are directly established by using finite element method.The model is proven to be applicable by comparing with Monte Carlo simulation.By applying the proposed stochastic framework to the high maglev line,the random dynamic responses of maglev vehicles running on the bridges are studied for running safety and stability assessment.Moreover,the effects of track irregularity wavelength range under different amplitude and running speeds on the coupled system are investigated.The results show that the augmentation of train speed will move backward the sensitive wavelength interval,and track irregularity amplitude influences the response remarkably in the sensitive interval.

Development and Application of Oil-Spill Risk Assessment Model for Offshore Pipeline

To the potential oil-spill risk caused by offshore pipeline more attention has been paid after the Dalian oil spill incident from oil-pipeline explosion. Since then an issue about how to prevent and control the sudden oil-spill from the offshore pipeline has been raised. In this paper, we proposed an optimized model to analyze the main causes(probability) of spill and the consequence with the fuzzy comprehensive assessment model. Considering the complicated assessment process for oil-spill, the assessment factor system involving the spill probability and consequence was established based on the operative manual and statistic leakage/damage data of offshore pipeline in order to estimate the integrated spill risk score automatically. The evaluated factors of spill probability could be grouped into five aspects: corrosion, fatigue, national damage, third party, and operational fault; the consequence evaluated factors of spill included hazard of oil and impact-controlling capability. With some modifications based on experts' opinions, each of the evaluated factors in our work was developed with a relative weight and evaluation criterion. A test example for an offshore pipeline in the Bohai waters was described to show how the model can be used for an actual case in more detail. By using the oil-spill risk assessment model, it is easy to determine the risk level associated with the ongoing activity and management level and hence to take the risk mitigation action immediately.

Application of logistic regression model for hazard assessment of landslides caused by the 2012 Yiliang Ms 5.7 earthquake in Yunnan Province,China

Accurate assessment of seismic landslides hazard is a prerequisite and foundation for postdisaster relief of earthquakes.An Ms 5.7 earthquake occurring on September 7,2012,in Yiliang County,Yunnan Province,China,triggered hundreds of landslides.To explore the characteristics of coseismic landslides caused by this moderate-strong earthquake and their significance in predicting seismic landslides regionally,this study uses an artificial visual interpretation method based on a planet image with 5-m resolution to obtain the information of the coseismic landslides and establishes a coseismic landslide database containing data on 232 landslides.Nine influencing factors of landslides were selected for this study:elevation,relative elevation,slope angle,aspect,slope position,distance to river system,distance to faults,strata,and peak ground acceleration.The real probability of coseismic landslide occurrence is calculated by combining the Bayesian probability and logistic regression model.Based on the coseismic landslides,the probabilities of landslide occurrence under different peak ground acceleration are predicted using a logistic regression model.Finally,the model established in this paper is used to calculate the landslide probability of the Ludian Ms 6.5 earthquake that occurred in August 2014,78.9 km away from the macro-epicenter of the Yiliang earthquake.The probability is verified by the real coseismic landslides of this earthquake,which confirms the reliability of the method presented in this paper.This study proves that the model established according to the seismic landslides triggered by one earthquake has a good effect on the seismic landslides hazard assessment of similar magnitude,and can provide a reference for seismic landslides prediction of moderate-strong earthquakes in this region.

Performance-based seismic assessment of skewed bridges with and without considering soil-foundation interaction effects for various site classes

The seismic behavior of skewed bridges has not been well studied compared to straight bridges. Skewed bridges have shown extensive damage, especially due to deck rotation, shear keys failure, abutment unseating and column- bent drift. This research, therefore, aims to study the behavior of skewed and straight highway overpass bridges both with and without taking into account the effects of Soil-Structure Interaction （SSI） due to near-fault ground motions. Due to several sources of uncertainty associated with the ground motions, soil and structure, a probabilistic approach is needed. Thus, a probabilistic methodology similar to the one developed by the Pacific Earthquake Engineering Research Center （PEER） has been utilized to assess the probability of damage due to various levels of shaking using appropriate intensity measures with minimum dispersions. The probabilistic analyses were performed for various bridge configurations and site conditions, including sand ranging from loose to dense and clay ranging from soft to stiff, in order to evaluate the effects. The results proved a considerable susceptibility of skewed bridges to deck rotation and shear keys displacement. It was also found that SSI had a decreasing effect on the damage probability for various demands compared to the fixed-base model without including SSI. However, deck rotation for all types of the soil and also abutment unseating for very loose sand and soft clay showed an increase in damage probability compared to the fixed-base model. The damage probability for various demands has also been found to decrease with an increase of soil strength for both sandy and clayey sites. With respect to the variations in the skew angle, an increase in skew angle has had an increasing effect on the amplitude of the seismic response for various demands. Deck rotation has been very sensitive to the increase in the skew angle; therefore, as the skew angle increased, the deck rotation responded accordingly. Furthermore, abutment unseating showed an increasing trend due to an increase in skew angle for both fixed-base and SSI models.

Probability-based analytical model for predicting the post-earthquake residual deformation of SDOF systems

A probability-based analytical model for predicting the seismic residual deformation of bilinear single-degreeof-freedom(SDOF)systems with a kinematic/Takeda hysteretic model is proposed based on a statistical analysis of the nonlinear time history response,and the proposed model explicitly incorporates the influence of record-to-record variability.In addition,the influence of primary parameters such as the natural vibration period,relative yield force coefficient,stiffness ratio and peak ground acceleration(PGA)on the seismic residual/maximum deformation ratio(dR/dm)are investigated.The results show that significant dispersion of the dR/dm ratio is observed for SDOF systems under different seismic ground motion records,and the dispersion degree is influenced by the model parameters and record-to-record variability.The statistical distribution of the dR/dm results of SDOF systems can be described by a lognormal distribution.Finally,a case study for seismic residual deformation and reparability assessment of the bridge structure designed with a single pier is carried out to illustrate the detailed analytical procedure of the probability-based analytical model proposed in this study.

基于失稳概率的单体滑坡灾害风险定量评价及其工程应用

对潜在滑坡灾害实施风险评价至关重要,但在实际工程中单体滑坡灾害风险评价仍然以定性评价方法为主,由危险性和损失通过风险矩阵得到定性风险等级,存在风险标准多重性和不连续性的问题,不便于在实际工程中对风险大小进行比较并实施分类处置,还可能导致风险评价结果出现误差,误导风险处置。为此,运用概率模型定量描述滑坡灾害的稳定性,同时考虑承灾体的损失大小,得到单体滑坡灾害风险定量评价指标,提出了滑坡灾害风险曲面及风险等值线的概念,并开发相应的评估计算软件,形成了滑坡灾害风险定量评价方法,消除了传统滑坡风险矩阵带来的风险标准多重性和不连续性,提高了评估的准确性。通过对重庆市奉节县6个单体滑坡进行风险定量评价,验证了所提方法的正确性和可靠性,为滑坡灾害风险评价提供了新的途径。

基于概率论的油气管道风险评价方法研究

梳理了管道风险指标及其逻辑关系,基于概率论推导提出了新的管道风险评价模型,在大量管道上进行了应用验证,解决了原评分法存在的问题,可较好地指导管道风险管控实践。

地面装甲类目标毁伤建模与评估方法

针对战斗部对地面装甲类目标实战化毁伤评估中破片战斗部爆炸高瞬态形成的不确定破片群很难直接用现有的方法对复杂系统目标进行毁伤评估的现象,论文以轻型地面装甲车为被毁对象,提出了一种新的目标毁伤建模与评估方法。在深入探究目标系统及其子功能的基础上,对轻型地面装甲车进行易损性分析并建立等效模型,给出基于轻型装甲车目标易损性和弹目交会关系的概率模型;最后对目标的毁伤评估进行仿真模拟,结果表明评估破片战斗部对轻型地面装甲车的实战化毁伤效果,可为破片战斗部毁伤效能的研究提供参考,并为目标毁伤概率定量计算提供新的理论支撑。

层次分析法在山地地质灾害危险性评价中的应用——以辽宁凌源地区为例

凌源市是辽西地区山地地质灾害危害较为严重的区域。在GIS技术支持下,选取地形、岩性、构造、降雨、道路、土地利用等6个因素作为评价指标,根据已发生的68个山地地质灾害点计算了各指标因子的敏感性,分别采用层次分析法、信息量法和统计量法确定了各指标的权重,利用因子叠置法对危险性进行了综合评价。结果表明层次分析法在该区山地地质灾害危险性评价中效果良好。该研究对相似地区山地地质灾害危险性区划具有一定的借鉴意义。

中国花生黄曲霉毒素风险评估中膳食暴露非参数概率评估方法

基于2009年、2010年对全国13个花生主产省155个县市2 571份代表性花生样品检测分析获得的12 855个黄曲霉毒素检测数据,以及卫生部2002年、2004年中国居民营养与健康状况调查报告中膳食消费数据,采用Monte Carlo模拟和Bootstrap抽样方法量化人群花生黄曲霉毒素膳食暴露量的变异度和不确定度,构建了中国花生黄曲霉毒素风险评估中膳食暴露非参数概率评估模型,依据年龄段、地区间和收入水平差异的人群花生黄曲霉毒素膳食暴露量,分析了各暴露量分布的指标统计量和90%置信区间。评估结果显示,2～5岁儿童为花生黄曲霉毒素膳食摄入的高暴露人群,其高端暴露量(P97.5)中位值为每千克体重每天1.342ng(表示为ng.kg-1.d-1,下同),四分位间距为0.151ng.kg-1.d-1;18～45岁成人中,城市人群花生黄曲霉毒素膳食暴露量高于农村,其高端暴露量(P97.5)中位值为0.695ng.kg-1.d-1,四分位间距为0.078ng.kg-1.d-1;中等收入水平人群花生黄曲霉毒素膳食暴露量最高,其高端暴露量(P97.5)中位值为0.874ng.kg-1.d-1,四分位间距为0.086ng.kg-1.d-1。花生黄曲霉毒素膳食暴露非参数概率评估方法克服了点评估方法不能定量评估结果变异度和不确定度的缺点,结果更为精确。

基于风险的油气管道最优完整性维护决策(一)

对管线进行完整性维护是目前管道公司的一项重要任务。文章分析了油气管线风险评价技术的现状 ,指出目前研究工作的范围和重点 ;介绍了一种处理管线维护资源最优分配的技术———基于风险的管线完整性维护决策优化技术。该方法分为系统排序和决策分析两过程 :系统排序按照完整性维修等级或单位风险降低费用对不同管段进行排序 ;决策分析评估可供选择的维修方式 ,确定每一个目标管段的最优维修方式。建立了管道完整性维护决策的数学模型 ,模型包括五要素 :状态集、决策集、概率分布、后果函数、决策准则与最优值。着重介绍了完整性维护决策优化的效用函数方法 ,包括效用函数的定义、分析原理、多准则效用函数的评估方法、基于效用函数的决策树、效用函数的构成等。还介绍了有限费用的决策优化方法。最后指出定量风险评价以及该技术中存在的难点 ,并提出建议。

基于概率-凸集混合模型的汽车正面碰撞结构可靠性优化设计

基于概率和凸集模型研究汽车正面碰撞可靠性优化设计问题。根据汽车吸能结构厚度、材料参数等不确定参数类型,分别采用概率和多椭球凸模型进行描述,以汽车安全性可靠性指标为约束,考虑汽车吸能结构质量为优化目标,建立混合模型可靠性优化设计模型。采用拉丁方试验设计构造目标函数和约束函数的Kriging近似模型,利用功能度量法评定概率约束,通过基于移动因子序列优化与可靠性评定将嵌套优化解耦为单层次优化。实际算例表明算法具有较高的计算效率及精度,对实际设计工作有一定参考价值。

腐蚀管线失效概率的评定方法

基于结构可靠性的一般理论 ,建立了腐蚀缺陷管线失效的极限状态函数 ,并以规则化的随机变量形式表示。采用雷 菲法求解了失效概率 ,提出了管线全线的失效概率分析方法 ,即沿管线全长以 1km管线为失效概率的分析单元进行计算 ,这样能合理考虑管线沿线腐蚀状况的差异。对一条经过检测的输油管线的腐蚀缺陷数据、管道运行参数和管材性能参数进行了统计分析 ,运用新提出的概率数学模型计算了管道全线的失效概率 ,并与推荐的目标失效概率进行了比较 ,从而提出了对管线重点维修和监测的区段。本方法是在对油气输送管线的腐蚀程度检测之后再进行安全评定的一个行之有效的方法。

暂态稳定分析中的风险评估方法

首先讨论了暂态稳定分析中传统确定性方法存在的问题,以及在市场环境下概率性暂态稳定分析方法的不足,在此基础上引入了暂态稳定分析中的风险评估方法,重点介绍了暂态稳定分析中的随机因素以及相应的建模方法,并建立了市场条件下系统暂态失稳给发电方、输电方、用户及整个系统造成损失的后果模型。最后对暂态稳定分析中的确定性方法、概率性方法以及风险评估方法进行了系统性的比较。

一种面向风险评估的输电线路故障概率模型

设备停运是电力系统失效的根本原因,建立设备故障概率模型是进行系统风险评估的核心问题。根据输电线路故障产生的内外部机理,提出了面向风险评估且适用于表征输电线路故障概率的Ageing-Load-Health-Weather-PHM(ALHW-PHM)。模型中基准故障概率函数采用老化失效模型,协变量采用负载率相依的实时导体温度及健康状态和天气状况相依的劣化扣分值,并采用极大似然估计进行参数拟合。为了提高参数拟合的效率,设计了一种基于大数据平台的样本数据级并行参数估计架构。算例分析定量展现了各风险因素对故障概率的影响及在系统风险评估中故障概率的应用。该模型能综合响应老化失效、负载率、健康水平和天气状况等风险因素对故障概率的影响,能为电网的风险评估提供理论支持。

RBCA、CLEA及CalTOX模型在苯并[a]芘污染场地健康风险评估中的应用比较

为探讨不同模型对污染场地健康风险评估结果的影响,以苯并[a]芘为例,采用RBCA、CLEA和CalTOX模型对某工业污染场地表层土壤进行健康风险评估,分析了评估结果的差异和原因,同时对模型的主要暴露参数进行了敏感性分析,并推导出基于风险概率分布的土壤修复限值。结果表明,RBCA、CLEA和CalTOX模型计算的苯并[a]芘致癌总风险分别为2.40×10-4、6.32×10-4和7.04×10-6,且经口摄入和皮肤接触2个途径对人体健康造成的危害最大。降解作用是影响CalTOX模型风险评估结果不同于RBCA和CLEA模型的重要因素,3个模型间参数取值及方法学的差异也会导致风险评估结果不同。各模型暴露参数的敏感性排序也有差异。采用基于风险概率分布的方法推导土壤修复限值,RBCA、CLEA和CalTOX模型所得结果分别为0.18、0.08、0.13(不考虑降解作用CalTOX模型)和10.74(考虑降解作用CalTOX模型)mg·kg-1,为各模型直接推导值的1.5～2.6倍。基于风险概率分布的方法可有效降低风险评估过程中参数不确定性的影响,为工业污染场地土壤修复值的制定提供参考。

基于云理论的居民负荷集体谐波概率分布

电力电子型居民负荷和新能源装置在配电网中应用越来越广泛,其产生的集体谐波非常可观,对电力系统的影响与危害已不可忽视。文中提出一种基于云理论的居民负荷集体谐波评估方法,介绍了云模型和云变换的基本理论,阐述了基于云理论的居民负荷集体谐波评估流程。通过实际案例证明,采用云变换方法可精确拟合谐波电流概率分布曲线,能较好地呈现居民负荷谐波电流幅值分布曲线的多峰性,其95%概率最大值估计精度显著优于正态分布法。研究结果对分析居民谐波来源、确定谐波治理措施和监管政策具有重要意义。

基于负荷不确定性建模的静态电压稳定性风险评估

该文以负荷不确定性建模为基础,提出一种静态电压稳定性风险评估方法。负荷不确定性建模分3个阶段进行,其一采用改进模糊C均值聚类方法、Cholesky分解和多维正态分布抽样技术得到初始负荷波动模型;其二基于蒙特卡罗方法,建立可同时计及负荷增长方向及功率因数随机变化、用来模拟多节点负荷持续增长情景的概率超圆锥体模型;其三以相关系数和互信息量为评判体系,根据负荷曲线相似度将节点分群,确定负荷出现同时增长的节点编号。之后,构建蒙特卡罗-连续潮流算法,植入负荷不确定性模型,提出4项分别针对节点、线路及系统的风险指标,得到完整的风险评估体系。该文以太原110k V电网为例,对比分析了含恒功率负荷模型系统与含综合负荷模型系统的风险水平、薄弱区域,验证了文中所提方法的准确性和有效性。

基于THERP+HCR的人因事件分析模式及应用

分析了传统人因事件分析模式THERP和HCR的特点与不足。将两者结合,建立了以THERP+HCR为定量分析核心的人因事件分析模式,介绍了其规范化分析程序和文件报告模式,并给出了在核电站的应用实例。

基于多项式模型和低风险的贝叶斯垃圾邮件过滤算法

针对现有贝叶斯算法应用于垃圾邮件过滤时,贝叶斯贝努利模型对邮件文本特征向量进行处理不能区分特征向量的重要性,导致邮件分类召回率低,同时还存在合法邮件被误判的风险的问题,采用贝叶斯多项式模型对特征向量进行加权处理来区分特征向量的重要性;然后,采用低风险策略来降低合法邮件被误判的风险,提出基于多项式模型和低风险的贝叶斯垃圾邮件过滤算法。实验结果表明:对于不同数量的特征项,该算法能够有效提高邮件分类的正确率与召回率,降低合法邮件被误判的风险,并在过滤文本字符数量较大的邮件时,具有性能平稳、波动小的特点。