海底管线管跨段涡激振动响应的实验研究

海底管线管跨段的涡激振动,是引发海底管线失效的主要因素之一,尤其是管跨在涡激振动下的“频率锁定”现象,是导致管线断裂失效的主要原因,也是在设计和维护管理中必须要避免的状态。影响管跨涡激振动响应规律的因素很复杂,因此,模型实验是研究和探索其规律的主要手段。为了探索海流运动对管跨动力响应的影响规律,在实验水槽中,分别对管跨在稳定流和随机流的作用下,管跨的动力响应规律进行了测定,本文对实验结果进行了分析的基础上,总结了“频率锁定”现象出现的条件,提出了在海底管线的可靠性设计和管道理中应采取的相应措施。     

非对称管 土边界的海底悬跨管道涡激振动特性

海底悬跨管道涡激振动问题十分复杂,需考虑流 管-土多场耦合效应。本文将悬跨管线简化为Euler-Bernoulli梁,两端跨肩管-土作用与线弹性弹簧和扭转弹簧近似,采用Van der pol方程描述旋涡脱落的尾迹特性。利用模态正交性对流-耦合控制方程进行解耦,采用龙格-库塔法进行数值求解,重点分析非对称边界对海底管道涡激振动特性的影响。计算结果表明：非对称边界条件对最大响应幅值影响不大;约束条件越强烈,模态激发越难,响应频率越高。     

涡激振动下管桥段的模糊动力可靠性研究

本文首先给出了管道在流体作用下的力学模型，并对风力作用下管道产生涡激振动的机理进行了分析，从而建立了管桥在风力作用下的力学模型和相应的振动微分方程，同时给出了管桥的固有特性和动力响应分析结果，然后，在此基础上，提出了首超模糊失效、模糊疲劳失效和混合失效等三类模糊失效准则，并依据这些准则分析给出了动力可靠性的计算公式，最后，给出了具体的算例。     

海底管道最大允许悬跨长度计算

海底悬跨管道在自身重量、内部流体重量、外部环境荷载作用下,将可能发生静力破坏及动力破坏。海底管道悬跨管段的长度是决定管道静力破坏与动力破坏的关键因素,因此确定了海底管道最大允许悬跨长度,就能够避免管道因悬跨长度过大而发生破坏。本文把避免出现涡激振动作为控制条件,提出了管道在顺流向振动下的最大允许悬跨长度公式,推导了不同边界条件下的管道自振频率公式,计算了管道在垂直流向振动下的最大允许悬跨长度。结果表明,支撑情况对管道最大允许跨长有很大的影响,在固端约束条件下的最大允许悬跨长度比简支约束下的长度大。     

带焊缝圆灯柱气动特性及焊缝影响机理研究

为了研究某实桥带焊缝圆灯柱的气动特性以及焊缝对灯柱涡激振动的影响机理,开展了灯柱刚性节段测压模型风洞试验,测试了无焊缝工况以及0°～180°焊缝位置的灯柱周向压力分布,分析了灯柱气动力以及流体卡门涡脱强度,揭示了焊缝对灯柱涡激振动的影响机理。研究结果表明：焊缝对灯柱的气动特性影响显著,不同的焊缝位置可以激发不同的流动模式,当焊缝在灯柱前驻点或者原分离点后侧时,灯柱气动特性受焊缝影响较小。当焊缝在B区域(21°～33°)和C区域(36°～63°)时,流体在焊缝附近发生分离-再附-再分离现象,卡门涡脱强度降低,灯柱的涡激振动被抑制。当焊缝在D区域(63°～78°)时,流体在焊缝位置直接涡脱,伴随着脉动风压和卡门涡脱强度的增强,使灯柱的涡激振动增大;焊缝尺寸的变化不会改变灯柱的气动力系数随焊缝位置的变化规律,但是可能会影响涡激振动风速锁定区间和振动幅值。     

水下悬跨输流管道流致振动响应研究

水下输流管道是油气管输的重要组成部分,海床或河床受水流的冲蚀而出现管跨后在内外流的作用下引起振动,造成水下管道的动力破坏。为此,以水下管道悬跨段为研究对象,考虑内外流体与管道间的流固耦合作用,将管跨处理成等截面的直梁模型,两端入土端的约束等效为弹性支承,采用模态叠加法对其进行动态响应研究,通过算例分析了各种参数对涡激振动特性的影响,从计算结果看出,内外流流速、压力、轴向力、管跨结构参数对管跨的动态响应具有重要影响。本文分析方法对水下管跨的动态设计和可靠性分析评估具有参考价值。     

桥塔涡激共振可靠性简化计算方法

针对桥塔在风载荷下的涡激共振可靠性问题,在涡激振动机理与频率锁定现象研究基础上,提出一种计算桥塔涡激振动可靠性的简化方法.将临界风速结合Re数和Strouhal数建立涡激共振下桥塔安全裕度方程,并引入AFOSM求解方法解决非线性问题,利用MATLAB进行可靠性求解程序编制,在保证计算精度的同时大大降低了桥塔涡激振动可靠...     

用动力测量值确定基础—地基系统的频变参数

提出了基础－地基系统具有频变参数的质－弹－阻模型，在这个模型中，系统的刚度Ｋ＝Ｋ０－Ｋ１ω＾２和阻尼系数Ｃ＝Ｃ０＋Ｃ１ω随系统振动频率而变化。文章以竖向振动为例，给出了用稳态激振下的动力反应测量值确定系统参数Ｋ０，Ｋ１，Ｃ０，Ｃ１的方法；讨论了基础频变刚度系统与附加质量系统的等效范围和差别。     

用动力测量值确定基础－地基系统的频变参数

提出了基础－地基系统具有频变参数的质－弹－阻模型，在这个模型中，系统的刚度Ｋ＝Ｋ０－Ｋ１ω２和阻尼系数Ｃ＝Ｃ０＋Ｃ１ω随系统振动频率而变化。文章以竖向振动为例，给出了用稳态激振下的动力反应测量值确定系统参数Ｋ０、Ｋ１，Ｃ０，Ｃ１的方法；讨论了基础频变刚度系统与附加质量系统的等效范围和差别。     

大跨斜拉桥桥面风致抖振的粘滞阻尼控制分析

现代大跨度斜拉桥结构重量轻、阻尼小,因而对风的作用比较敏感。紊流风诱发桥梁过大的抖振响应会危及行车、行人的舒适和安全。本文利用有限元软件ANSYS,以山东滨州黄河公路大桥为例建立了大跨斜拉桥三维空间有限元模型,在全桥动力特性分析的基础上,利用混合自回归模型模拟桥梁脉动风荷载,并进行了自激力的时域化处理,重点分析了桥面侧向抖振响应;通过对粘滞阻尼器力学特性的分析,提出了在桥塔和主梁之间安装与桥面成45°的粘滞阻尼器来控制桥面侧向抖振响应的方案,并分析了不同阻尼系数时的控制效率。研究结果表明:在侧向风力的强迫作用下,桥面侧向抖振响应不可忽视;粘滞阻尼器控制下,桥面抖振响应显著减小,各主要构件内力均无明显增加,且随着阻尼系数的增大,减振效率显著增大,阻尼器的出力也增大,但当阻尼系数达到一定值后,减振效率的增大趋于平缓,存在一个经济合理的最优值。     

Probability-credibility health risk assessment under uncertain environment

The ability to describe variables in a health risk model through probability theory enables us to estimate human health risk. These types of risk assessment are interpreted as probabilistic risk assessment (PRA). Generally, PRA requires specific estimate of the parameters of the probability density of the input variables. In all circumstances, such estimates of the parameters may not be available due to the lack of knowledge or information. Such types of variables are treated as uncertain variables. These types of information are often termed uncertainty which are interpreted through fuzzy theory. The ability to describe uncertainty through fuzzy set theory enables us to process both random variable and fuzzy variable in a single framework. The method of processing aleatory and epistemic uncertainties into a same framework is coined as hybrid method. In this paper, we are going to talk about such type of hybrid methodology for human health risk assessment. Risk assessment on human health through different pathways of exposure has been attempted many a times combining Monte Carlo analysis and extension principle of fuzzy set theory. The emergence of credibility theory enables transforming fuzzy variable into credibility distribution function which can be used in those hybrid analyses. Hence, an attempt, for the first time, has been made to combine probability theory and credibility theory to estimate risk in human health exposure. This method of risk assessment in the presence of credibility theory and probability theory is identified as probabilistic-credibility method (PCM). The results obtained are then interpreted through probability theory, unlike the other hybrid methodology where the results are interpreted in terms of possibility theory. The results obtained are then compared with probability-fuzzy risk assessment (PFRA) method. Generally, decision under hybrid methodology is made on the index of optimism. An optimistic decision maker estimates from the \(\alpha\)-cut at 1, whereas a pessimistic decision maker estimates from the \(\alpha\)-cut at 0. The PCM is an optimistic approach as the decision is always made at \(\alpha\)=1.     

结构振动的模糊建模与模糊控制规则提取

模糊振动控制中存在的模糊控制规则的建立大都依赖于主观经验的现状。对此本文提出了一种通过对结构振动模糊建模来产生控制规则的方法。首先，通过对系统运动状态变量的模糊化，建立结构振动的模糊关系模型；其次通过对结构振动的模糊关系模型的分析，提取出模糊控制规则；最后，通过一个单自由度体系的数值仿真方法进行了验证。     

基于模糊数学的农村砖木民房震害预测研究

基于模糊数学方法及其应用理论对农村地区砖木民房进行震害预测研究。建立了适用于砖木民房的震害影响因子集及其与震害等级的模糊关系,进一步研究出基于模糊综合评价方法的砖木民房震害预测模型。初步研究表明,该震害预测模型条理清晰,计算简便,可进一步研究推广应用。     

余震区长度与震级关系的模糊神经元网络模型

本文试图将模糊人工神经元网张及模糊信息分析理论引入到余震区长度与震级关系的识别之中，采用信息扩散与ＢＰ型人工神经元网络相结合的方法建立模型，该模型有较强的自适应能力及处理矛盾样本的功能。最后将该模型的识别结果与统计结果瑟统计结果进行了比较，结果表明该模型具有一定的优越性。     

Updating Real-Time Flood Forecasting Using a Fuzzy Rule-Based Model/Mise à Jour de Prévision de Crue en Temps Réel Grâce à un Modèle à Base de Règles Floues

Abstract

An updating technique is a tool to update the forecasts of mathematical flood forecasting model based on data observed in real time, and is an important element in a flood forecasting model. An error prediction model based on a fuzzy rule-based method was proposed as the updating technique in this work to improve one- to four-hour-ahead flood forecasts by a model that is composed of the grey rainfall model, the grey rainfall—runoff model and the modified Muskingum flow routing model. The coefficient of efficiency with respect to a benchmark is applied to test the applicability of the proposed fuzzy rule-based method. The analysis reveals that the fuzzy rule-based method can improve flood forecasts one to four hours ahead. The proposed updating technique can mitigate the problem of the phase lag in forecast hydrographs, and especially in forecast hydrographs with longer lead times.     

建筑物震害预测模糊震害指数法

建筑物震害预测是城市防震减灾的基础工作之一。本文在分析现有震害预测方法的基础上，提出了一种新的震害预测方法－模糊震害指数法。模糊震害指数法以现有震害预测资料为基础，采用模糊数学方法实现。本文详细阐述了模糊震害指数法的理论模型，推导了其数学公式，最后给出了实例分析。     

Modeling the initiation of sediment motion under a wide range of flow conditions using a Geno-Mamdani Fuzzy Inference System method

The current study introduces a novel approach to estimate the incipient motion of sediments under a wide range of flow regimes by developing a fuzzy model with a fuzzy-band that refers to a transition from weak motion to general motion of sediment. The partial sediment entrainment is defined by fuzzy sets considering the uncertainty related to the individual ratio of inertia to viscous forces which is the definition of shear Reynolds number. In the current study, the Mamdani Fuzzy Inference System (Mamdani FIS) is used to develop a comprehensive fuzzy model of the incipient motion of sediment. The Mamdani FIS has a shortcoming regarding the training of the fuzzy model. To estimate the dimensionless shear stress, a new method is developed by combining a genetic algorithm with the fuzzy approach which is named the Geno-Mamdani Fuzzy Inference System (GMFIS) method. The performance of the GMFIS model is evaluated using experimental data by considering root mean square error (RMSE), Nash-Sutcliffe coefficient of efficiency (CE), degree of robustness (D_r), and concordance coefficient (CC) as evaluation criteria. The GMFIS model performed very well based on the RMSE, CE, D_r, and CC values and satisfactorily represented the three types of incipient motion. Finally, a new range of fuzzy, dimensionless, critical shear stress values is established in all flow conditions from weak to general sediment entrainment.     

Fuzzy logic algorithm for runoff-induced sediment transport from bare soil surfaces

Utilizing the rainfall intensity, and slope data, a fuzzy logic algorithm was developed to estimate sediment loads from bare soil surfaces. Considering slope and rainfall as input variables, the variables were fuzzified into fuzzy subsets. The fuzzy subsets of the variables were considered to have triangular membership functions. The relations among rainfall intensity, slope, and sediment transport were represented by a set of fuzzy rules. The fuzzy rules relating input variables to the output variable of sediment discharge were laid out in the IF-THEN format. The commonly used weighted average method was employed for the defuzzification procedure.The sediment load predicted by the fuzzy model was in satisfactory agreement with the measured sediment load data. Predicting the mean sediment loads from experimental runs, the performance of the fuzzy model was compared with that of the artificial neural networks (ANNs) and the physics-based models. The results of showed revealed that the fuzzy model performed better under very high rainfall intensities over different slopes and over very steep slopes under different rainfall intensities. This is closely related to the selection of the shape and frequency of the fuzzy membership functions in the fuzzy model.     

基于区间直觉模糊数的地震应急服务点选址模型

地震应急物资储备服务点选址是地震应急救援决策工作的重要基础。本文分析了地震应急服务点选址问题的不确定性,介绍了直觉模糊数和区间直觉模糊数的概念,在分析两者之间关系的基础上,定义了区间直觉模糊数的得分函数和精确函数,进而提出了基于得分函数和精确函数的区间直觉模糊数的排序规则;行车时间受诸多因素影响,将行车时间看成区间直觉模糊信息,构建了约束中含有区间直觉模糊参数的地震应急服务点选址模型,提出了一种基于区间直觉模糊数排序规则的模型算法,可得到地震应急服务点最优选址方案。通过算例分析验证了该方法的有效性。     

Uncertainty Analysis for a Dynamic Phosphorus Model with Fuzzy Parameters

A simplified method based on fuzzy set theory is presented to incorporate uncertainty of parameters into a dynamic total phosphorus model. Uncertainty may arise from difference between calibrated conditions and projected condition as well as from inconsistency of available data in the literature. The uncertainty in parameters was represented by fuzzy numbers that can be generated through various ways such as model calibration process, soft interpretation of literature data, and subjective opinions of experts. The proposed fuzzy approach decomposed fuzzy parameters into interval numbers at different level cuts, and solved for interval solutions through very simple calculation instead of solving nonlinear programming models. The interval solutions at each level cut were could be combined to obtain fuzzy solutions. This method has been applied to the phosphorus load-response model of the Triadelphia Reservoir near the Washington, DC area. Two pollution control scenarios have been simulated with fuzzy parameters. The measures of necessity and possibility have been used to analyze the potential risk of the two scenarios. The research results indicated that uncertainty is a very important factor in water quality modeling. By incorporating uncertainty into model framework, the fuzzy model identified the highly risky scenario that was considered preferable based on solutions of the deterministic model.