Assessment of reliability in water distribution networks using entropy based measures

Entropy based expressions for measurement of reliability and redundancy have recently been reported. These measures approach assessment of the reliability of the distribution network from the intrinsic redundancy of the network layout. The paper extends earlier work on entropy functions by including a more explicit statement of the alternate paths available in the network and by recognizing that under certain circumstances, e.g., failure of some part of the network work, an outflow link from a node under normal working condition may become an inflow link to the same node. The measures are assessed by comparison with parameters measuring Nodal Pair Reliability and percentage of flow supplied at adequate pressure for a range of networks and link failure conditions in this networks. The entropy measures are shown to reflect changes in the network reliability, as measured by these two comparative parameters, very well.     

Cost-effective network design for groundwater flow monitoring

The extensive use of groundwater resources has increased the need for developing cost-effective monitoring networks to provide an indication of the degree to which the subsurface environment has been affected by human activities. This study presents a cost-effective approach to the design of groundwater flow monitoring networks. The groundwater network design is formulated with two problem formats: maximizing the statistical monitoring power for specified budget constraint and minimizing monitoring cost for statistical power requirement. The statistical monitoring power constraint is introduced with an information reliability threshold value. A branch and bound technique is employed to select the optimal solution from a discrete set of possible network alternatives. The method is tested to the design of groundwater flow monitoring problem in the Pomona County, California.     

RC框架结构薄弱层的层间位移可靠度水平考察

讨论了钢筋混凝土框架结构层间极限变形角的近似概率特性,考察了大震作用下20余幢钢筋混凝土框架结构薄弱层的层间位移可靠度水平,从而为直接基于位移可靠度的抗震设计中层间目标位移可靠度的确定提供了一定依据。     

随机地震动场激励下拱坝多点输入的抗震可靠度分析

本文首次将空间随机地震场输入用于拱坝随机振动分析之中，与拱坝三维动力学有限元法结合，完成了三维拱坝在空间随机地震动场作用下的随机振动分析方法及算法的研究，另外考虑动力和静力的叠加，提出了三维空间随机地震动场的拱坝抗震可靠度分析方法，最后编制了相应的程序，对小湾拱坝进行了抗震可靠度分析，并与随机变量的结果进行了比较。     

结构模糊随机可靠度的实用计算方法

本文以模糊随机变量为基本变量，定义了结构的模糊随机功能函数，分析了结构有效状态与失效状态之间的模糊性，建立了结构的模糊随机极限状态方程。利用序关系给出单失效模式结构的模糊安全准则，讨论了ａ－约束水平条件下单失效模式结构的失效概率、可靠度及可靠指标，进而得出结构的模糊随机失效概率、模糊随机可靠度及模糊可靠指标等。本文给出的具体计算方法和目前设计规范中彩的方法是相对应的。     

高压断路器隔震体系抗震可靠度分析

给出了基于随机地震动模型的高压断路器抗震可靠性分析方法。通过建立高压断路器及其隔震体系的有限元计算模型，分析了在断路器底部瓷套管根部加设叠层橡胶垫后的动力性能，分析中利用随机地震动模型，充分考虑地震动的随机作用，给出了四类场地土条件下结构的地震响应均值和标准差；利用一次二阶矩理论计算得到高压断路器的可靠度，给出了各场地土条件下的震害率曲线。结果表明不同场地土条件下隔震垫的减震效果有所差异。     

Minimal cut-based recursive decomposition algorithm for seismic reliability evaluation of lifeline networks

In this paper, a new probabilistic analytical approach, the minimal cut-based recursive decomposition algorithm (MCRDA), is presented to evaluate the seismic reliability of large-scale lifeline systems. Based on the minimal cut searching algorithm, the approach calculates the disjoint minimal cuts one by one using the basic procedure of the recursive decomposition method. At the same time, the process obtains the disjoint minimal paths of the system. In order to improve the computation efficiency, probabilistic inequality is used to calculate a solution that satisfies the prescribed error bound. A series of case studies show that MCRDA converges rapidly when the edges of the systems have low reliabilities. Therefore, the approach can be used to evaluate large-scale lifeline systems subjected to strong seismic wave excitation.     

太湖流域水文遥测系统可靠性分析

水文遥测系统工作制式不同,系统的验收标准也不同,水文遥测系统的组网结构不同,系统可靠性的分析也不同。本文用概率方法对太湖流域水文遥测系统的可靠性进行探讨,对带存储功能的应答系统采用系统可靠度衡量,而不采用月平均数据畅通率衡量;同时讨论不同的系统结构对可靠性的影响,这种以概率统计的方法分析水文遥测系统的可靠性,对水文遥测系统建设的验收标准制定和水文遥测系统结构设计具有重要意义。     

The impact of upstream water abstractions on reservoir yield: the case of the Orós Reservoir in Brazil

Abstract

Water abstraction for irrigation upstream of a reservoir and its impact on reservoir yield and reliability are studied. Water demand and availability are strongly related in semi-arid environments where the irrigation sector is responsible for a large part of consumptive water use. Variations in water abstractions for irrigation depend on irrigation requirements per hectare and the size of the irrigated area. The Orós Reservoir in semi-arid Northeast Brazil has been taken as a case study. The results show that water abstracttion for irrigation is of significant importance for reservoir yield and reliability. Yield—reliability simulations for the study area show that taking into account upstream water abstraction for a reservoir yield of 20.0 m³/s results in a water-scarcity probability of 10% on an annual basis (90% reliability). This is only 5% if up-stream abstraction for irrigation is ignored. This study shows that observed land-use changes in the study area do have a significant impact on reservoir yield reliability. The variability of upstream water abstraction was found to be of low importance for reservoir yield and reliability.     

Markovian modeling of seismic damage accumulation

Analysis of civil structures at the scale of life‐cycle requires stochastic modeling of degradation. Phenomena causing structures to degrade are typically categorized as aging and point‐in‐time overloads. Earthquake effects are the members of the latter category this study deals with in the framework of performance‐based earthquake engineering (PBEE). The focus is structural seismic reliability, which requires modeling of the stochastic process describing damage progression, because of subsequent events, over time. The presented study explicitly addresses this issue via a Markov‐chain‐based approach, which is able to account for the change in seismic response of damaged structures (i.e. state‐dependent seismic fragility) as well as uncertainty in occurrence and intensity of earthquakes (i.e. seismic hazard). The state‐dependent vulnerability issue arises when the seismic hysteretic response is evolutionary and/or when the damage measure employed is such that the degradation increment probabilistically depends on the conditions of the structure at the time of the shock. The framework set up takes advantage also of the hypotheses of classical probabilistic seismic hazard analysis, allowing to separate the modeling of the process of occurrence of seismic shocks and the effect they produce on the structure. It is also discussed how the reliability assessment, which is in closed‐form, may be virtually extended to describe a generic age‐ and state‐dependent degradation process (e.g. including aging and/or when aftershock risk is of interest). Illustrative applications show the options to calibrate the model and its potential in the context of PBEE. Copyright © 2015 John Wiley & Sons, Ltd.