基于可靠度理论的水工结构设计方法

基于水工结构可靠性设计标准,对目前水工结构可靠度的“作用效应-结构抗力”分析计算模型进行分析;通过对坝基面抗滑稳定及混凝土重力坝材料强度极限状态分析,发现采用以概率理论为基础的极限状态设计方法更为简便.将可靠度理论应用于水工结构稳定性计算;依据水工设计规范对可靠度方法中系数取值进行分析,将复杂计算方法简单化.对水工结构中概率极限状态设计法提出建议.     

基于可靠度理论的水工结构设计方法

基于水工结构可靠性设计标准,对目前水工结构可靠度的"作用效应~结构抗力"分析计算模型进行分析。通过对坝基面抗滑稳定及混凝土重力坝材料强度极限状态分析发现,采用以概率理论为基础的极限状态设计方法更为简便。将可靠度理论应用于水工结构稳定性计算,依据水工设计规范对可靠度方法中系数取值进行分析,将复杂计算方法简单化,对水工结构中概率极限状态设计法提出建议。     

可靠度理论在水工结构设计中的应用

文章论述了传统的安全系数设计法的不可克服的缺点,严重地阻碍水工结构设计的进一步合理化。从而论证按可靠度理论改革水工结构设计方法的必要性,说明了按可靠度理论改善水工结构设计方法的可行性。同时还对水工结构可靠度分析中各种参数的取值提供了建议。     

结构可靠度理论在水工结构设计标准中的应用

为了推动结构可靠度理论在水工结构设计标准中的应用和发展,系统地总结了笔者近30 a来参加完成的水工结构设计标准按结构可靠度理论修编的成功经验,提出了水工结构设计标准按结构可靠度理论修编的可靠度校准分析方法和目标可靠指标的确定原则;提出了水工结构设计标准分项系数的确定原则与方法;提出了分项系数设计表达式的相当安全系数的概念及其应用;提出了国内外结构设计标准的安全度设置水平比较时应遵循的基本原则和方法等。上述研究成果可供水工结构设计标准按结构可靠度理论进行修编时借鉴与参考。     

结构点可靠度在水工结构中的应用

通过对结构点可靠度的理论分析,并结合某砌石坝的具体算例,系统地介绍了结构点可靠度的计算方法在水工结构中的应用,并提出了结构点可靠度研究结合水工实际进一步完善计算方法的意见。     

水工结构可靠度置信区间的研究与应用

概述了水工结构可靠度设计理论的发展,基于数理统计理论中的置信区间提出了水工结构可靠度的置信区间的数学定义,推出了两个正态随机变量在四种常见情况下的可靠指标的置信下限。     

黄河利津段堤防边坡稳定可靠度分析的探讨

1引言1994年国家发布了《水利水电工程可靠度设计统一标准》,根据工程结构可靠度设计统一标准规定的原则,编制并发布了《水工建筑物荷载设计规范DL5077-1997》,《水工混凝土结构设计规范SL/T191-96》等一系列新的规范。但是,有些规范由于条件还不成熟,仍未能按工程结构可靠度标     

可靠度理论用于水工结构设计规范编制的几点建议

针对用可靠度理论编制水工结构设计规范的３ 点意见，认为作用的代表值定义多，易引起混淆；极限状态设计表达式的结构不够直观；用可靠度理论修订水工结构设计规范没能提高设计水平。建议加大对设计诸要素统计分析的投入； 同时在形式上做一些调整， 使可靠度理论的先进性得以充分体现。     

《水工钢筋混凝土结构设计规范（SDJ20－78）》可靠度校准分析

根据《水利水电工程结构可靠度设计统一标准》（文中简称《水工统标》）规定的原则和方法，对现行《水工纲筋混凝土结构设计规范（ＳＤＪ２０－７８）》（文中简称《现行规范》）中的构件强度可靠度进行了校准和分析，提出了设计目标可靠指标的取值建议，可供《水工统标》编制和《现行规范》修订时参考。     

水工钢闸门可靠度设计建议公式

随着可靠度理论的不断发展,工程结构可靠度分析已逐步应用到国内外各相关领域。而我国 现行水工钢闸门设计规范仍采用容许应力法,显然远落后于发展形势,难以满足闸门的实际需求。为了 推动可靠度理论在水工钢闸门方面的应用发展,文中给出按可靠度方法设计的建议公式,并与容许应力 法进行比较,指出两种方法的优缺点,为今后的研究和规范修订提供了基础。     

地下厂房施工过程的三维非线性数值模拟分析

根据冗各电站地下厂房开挖支护的施工顺序,以隐式杆单元模拟锚杆,以壳单元模拟混凝土喷层,采用三维非线性有限元技术,对洞室群的开挖支护动态过程进行了模拟计算。通过三维非线性有限元计算分析得到:洞室群动态开挖过程中围岩应力变形的分布规律,围岩塑性区的发展规律,锚杆受力变化情况。计算结果表明:整个开挖过程中,洞周围岩位移变化规律正常,量值较小,塑性区主要分布在洞室周边,围岩稳定性较好;但在洞室交叉口处围岩的变形较大,出现较大范围的塑性区,在此基础上提出了支护措施优化方案,并对优化方案的效果进行了评价。     

Evaluation of freshwater mussel relocation as a conservation and management strategy

The relocation of unionacean mussels is commonly used as a conservation and management tool in large rivers and streams. Relocation has been used to recolonize areas where mussel populations have been eliminated by prior pollution events, to remove mussels from construction zones and to re-establish populations of endangered species. More recently, relocation has been used to protect native freshwater mussels from colonization by the exotic zebra mussel Dreissena polymorpha. We conducted a literature review of mussel relocations and evaluated their relative success as a conservation and management strategy. We found that 43% of all relocations were conducted because of construction projects that were forced to comply with the Endangered Species Act 1973 and that only 16% were monitored for five or more consecutive years. Most (43%) relocation projects were conducted from July to September, presumably a period when reproductive stress is relatively low for most species and the metabolic rate is sufficient for reburrowing in the substrate. The mortality of relocated mussels was unreported in 27% of projects; reported mortality varied widely among projects and species and was difficult to assess. The mean mortality of relocated mussels was 49% based on an average recovery rate of 43%. There is little guidance on the methods for relocation or for monitoring the subsequent long-term status of relocated mussels. Based on this evaluation, research is needed to develop criteria for selecting a suitable relocation site and to establish appropriate methods and guidelines for conducting relocation projects.     

基于模型试验的河床砂砾石层基本特性研究

为了经济可靠地确定深厚覆盖层的基本特性参数,以大渡河双江口水电站坝基河床砂砾石层基本特性研究为工程背景,进行大尺寸模型试验,研究河床砂砾石层的旁压模量和动探击数随密度、级配以及上覆压力的变化规律。根据室内模型试验结果,结合现场旁压试验及钻孔试验成果,推断出坝址区河床砂砾石相关层位的密度,并依此进行砂砾石室内力学试验,获得设计所需力学参数。研究成果可为深厚覆盖层基本特性测试提供新的方法。     

基于BP神经网络-马尔科夫链模型的隧道围岩位移预测

在隧道工程施工中,围岩位移预测起着很重要的作用。将BP神经网络-马尔科夫链模型引入到隧道围岩位移预测中来,通过对训练样本的学习,利用BP神经网络实现了对位移时间序列的滚动预测,同时得到了实测值与预测值的相对误差;在此基础上利用马尔科夫链对相对误差进行修正,有效地提高了预测结果的精度。并将该模型应用于某公路隧道拱顶下沉位移时序预测中,结果表明该模型具有精度高、科学可靠的特点,为隧道围岩变形的预测提供了新的途径。     

Short communication. Pipelines as a refuge for freshwater snails

In the lower River Murray, Australia, populations of gastropods have declined markedly over the past 40 years. Of the native fauna of about 18 species, only the ancylid Ferrissia petterdi remains common (but in patches), and another five species feature in sporadic local resurgences. Until recently the viviparid Notopala was thought to be extinct. The introduced physid Physa acuta is widespread, but in low numbers. The decline probably is associated with flow regulation, high turbidity and the introduction of common carp. Snail populations have persisted, however, in irrigation pipelines fed from the river, where they periodically cause blockages. This paper reports the discovery of the only known populaion of Notopala hanleyi in a pipeline where the inner wall accumulates microbial and other organic matter, providing high quality food for snails. In the Murray before regulation most of the periphytic biomass was probably microbial, as fluctuating water levels would have maintained littoral communities in a highly productive, early state of succession his postulated that, by stabilizing seasonal water levels, regulation has promoted the production of filamentous green algae, an inferior food source, and so displaced snail populations from the open aquatic environment.     

浙江省水域调查录入系统的设计和应用

浙江省水域调查录入系统将调查数据与电子地图相整合,对分类水域数据进行统计计算,并对输入数据进行合理性和完整性检查,得到调查范围内现有水域的详细数据,实现了水域调查数据输入、计算、统计和查询的数字化管理,提高了工作效率和工作质量,为各地下阶段水域保护规划编制和水域管理工作提供了数据支持。对该系统的设计原则、功能和技术设计等作了介绍。     

基于CT-连续加荷水泥乳化沥青混凝土细观损伤规律研究

利用CT技术对水泥乳化沥青混凝土的细观损伤过程进行实时扫描观测,获得了混凝土试件在连续加荷下的CT图像。通过采用直观分析法、CT数分析法、CT数与损伤变量关系3种方法分析表明,水泥乳化沥青混凝土的破坏过程可分为压密、扩容、裂纹扩展、破坏4个阶段,同时混凝土在受压过程中具有韧性,在极限荷载之前各断面处于压密和微扩容的强化阶段,极限荷载之后混凝土从损伤到破坏发展比较平稳。     

Automated system for removal and pneumatic transport of fly ash from electric precipitator hoppers

A system for removal and pneumatic transport of fly ash is examined, in which air pulses act on batches (pistons) of ash formed in a duct. Studies are made of the effect of several physical parameters on the force required to displace a piston of ash and these serve as a basis for choosing a system for removal and pneumatic transport of ash simultaneously from several hoppers of an electric precipitator. This makes it possible to separate the ash particles according to size without introducing additional components. Formulas are given for calculating the structural and dynamic parameters of this system and measurements of indirect dynamic parameters are used to calculate the input-output characteristics of the system. In order to optimize the system, configurations for summing several ducts into a single transport duct for pneumatic ash transport are proposed. Some variants of dry ash utilization and the advantages of producing of size-separated particles are considered. __________ Translated from élektricheskie Stantsii, No. 2, pp. 26–30 (2008).     

The flood pulse advantage and the restoration of river-floodplain systems

The ‘flood pulse advantage’ is the amount by which fish yield per unit mean water area is increased by a natural, predictable flood pulse. Evidence for this increase is presented from tropical and temperate fisheries. It is argued that increasing multispecies fish yield by restoring the natural hydrological regime is consistent with increasing production of other trophic levels and with restoration from ecological and aesthetic viewpoints. When applied to a river-floodplain system, this restoration would provide a large, self-sustaining potential for recreation, commercial exploitation, and flood control. An interim ‘natural flood pulse’ restoration approach is proposed for systems modified for navigation. This approach approximates the natural hydrological regime in a river reach and is intended as a first step in the long process of restoring the watershed.     

浅谈天湖水电站水轮机运行故障及处理措施

简述天湖水电站投运以来各种故障的表现形式，分析其原因，提出了相应的处理方法及措施，并对合理利用国内外设备提出建议。