剪力墙抗震能力设计措施有效性的校验与改进

为研究有效的剪力墙抗震能力设计措施,引导其在强震中实现可控的预期破坏模式,通过理论分析指出目前剪力墙能力设计措施存在的问题,通过精细有限元动力时程算例分析,校验了中国规范剪力墙能力调整措施的有效性;提出了改进措施,并进行了算例验证.结果表明,在刚性地基假定下中国2001版抗震规范抗弯能力调整措施使得剪力墙底截面在大震下...     

薄板混凝土组合截面部分外包组合柱(弱轴)滞回性能足尺试验研究

为了研究薄板混凝土组合截面部分外包组合柱（弱轴）的滞回性能,对3个薄板混凝土组合截面部分外包组合柱（弱轴）足尺试件在恒定轴压下进行了水平低周反复荷载试验,观察了加载过程中薄壁板件翼缘局部屈曲和混凝土裂缝开展与压溃现象,得到了试件的荷载 位移滞回曲线。根据试验结果分析了试件的承载力、抗侧刚度、延性与耗能、破坏模式等力学性能。结果表明：试件具有较好的变形能力和耗能能力;试件的破坏模式为柱脚部位混凝土压溃和拉结筋屈服甚至拉断,随之薄壁板件翼缘发生局部屈曲。研究进一步丰富了薄板混凝土组合截面部分外包组合柱研究成果,为该类柱设计规范的制订和工程应用提供了理论依据和技术储备。     

基于对数正态分布的岩石损伤本构模型研究

根据岩石微元物理力学性能服从随机分布的特点,采用对数正态分布作为岩石微元强度的概率分布模型,结合损伤力学理论和统计强度理论,建立了三轴压缩条件下的岩石损伤本构模型。在此基础上,考虑岩石破裂过程全应力应变曲线的特点,利用多元函数极值理论依据试验曲线的特征参量确定出损伤本构模型参数。与试验结果及前人研究结果比较,该模型形式简单,参数求取容易,能较好地反映岩石内部缺陷分布和变形特征,表征岩石破裂过程的全应力应变关系。     

DIFFERENT ROOF BEHAVIOUR UNDER DIFFERENT UPPER MINING BOUNDARY CONDITION IN DATONG

Understanding roof behaviour and immediate roof failure patterns of Iongwall face is a prerequisite for establishing correct roof control theory and appplying effective roof control measures. Roof behaviour and immediate roof failure pattern have a close relationship with upper mining boundary conditions of Iongwall face. According to actual situation of Datong Mining Area, upper mining boundary conditions of Iongwall face have been classified into 5 types in this paper. Roof behaviour and immediate roof failure pattern under each upper mining boundary condition are discussed in details.     

基于贝叶斯网络的土石坝可靠性分析

提出采用贝叶斯网络方法来分析大坝的可靠性问题．首先简要地介绍了贝叶斯网络方法的基本原理和建模方法，将贝叶斯网络方法和故障树方法进行了比较，并给出了故障树向贝叶斯网络转化的基本步骤．定义了贝叶斯网络中节点的重要度因子，并给出了相应的计算公式．最后以土石坝为例，根据土石坝的失效机理建立了土石坝可靠性分析的贝叶斯网络模型，并对溃坝原因进行了重要度分析．结果表明，贝叶斯网络能够有效地进行大坝可靠性分析，它能够更直观地表示大坝失事的因果关系，且贝叶斯网络能够方便地解决共因失效问题．故障树可以方便地转化为相应的贝叶斯网络模型．贝叶斯网络节点的重要度分析结果为制定有效的大坝失事概率控制措施提供了理论依据．     

Failure cost design of structural systems

A systematic design approach based on applying weights to modes of failure is proposed. Representative individual failure modes are identified on the limit state surface using a nonlinear structural analysis program. Modal failure probabilities are computed in load space (in which randomness in structural resistance is included), and linearized around mean plastic moment capacities. Single- and multi-objective formulations with objectives of failure cost and initial cost, and with mean plastic moment capacities of structural members as decision variables are used. An iterative procedure with successively tighter bounds on the decision variables is employed. The procedure is applied to a simple frame for which optimum plastic moment capacities (single-objective case) and a trade-off curve between future (failure) cost and initial cost (multi-objective case) are found.     

A feasibility assessment of the use of nanofluids to enhance the in-vessel retention capability in light-water reactors

Nanofluids, colloidal dispersions of nanoparticles, exhibit a substantially higher critical heat flux (CHF) compared to water. As such, they could be used to enhance the in-vessel retention (IVR) capability in the severe accident management strategy implemented by certain light-water reactors. It is envisioned that, at normal operating conditions, the nanofluid would be stored in dedicated storage tanks, which, upon actuation, would discharge into the reactor cavity through injection lines. The design of the injection system was explored with risk-informed analyses and computational fluid dynamics. It was determined that the system has a reasonably low failure probability, and that, once injected, the nanofluid would be delivered effectively to the reactor vessel surface within seconds. It was also shown analytically that the increase in decay power removal through the vessel using a nanofluid is about 40%, which could be exploited to provide a higher IVR safety margin or, for a given margin, to enable IVR at higher core power. Finally, the colloidal stability of a candidate alumina-based nanofluid in an IVR environment was experimentally investigated, and it was found that this nanofluid would be stable against dilution, exposure to gamma radiation, and mixing with boric acid and lithium hydroxide, but not tri-sodium phosphate.     

Two types of a passive safety containment for a near future BWR with active and passive safety systems

The paper presents two types of a passive safety containment for a near future BWR. They are named Mark S and Mark X containment. One of their common merits is very low peak pressure at severe accidents without venting the containment atmosphere to the environment. The PCV pressure can be moderated within the design pressure. Another merit is the capability to submerge the PCV and the RPV above the core level. The third merit is robustness against external events such as a large commercial airplane crash. Both the containments have a passive cooling core catcher that has radial cooling channels. The Mark S containment is made of reinforced concrete and applicable to a large power BWR up to 1830 MWe. The Mark X containment has the steel secondary containment and can be cooled by natural circulation of outside air. It can accommodate a medium power BWR up to 1380 MWe. In both cases the plants have active and passive safety systems constituting in-depth hybrid safety (IDHS). The IDHS provides not only hardware diversity between active and passive safety systems but also more importantly diversity of the ultimate heat sinks between the atmosphere and the sea water. Although the plant concept discussed in the paper uses well-established technology, plant performance including economy is innovatively and evolutionally improved. Nothing is new in the hardware but everything is new in the performance.     

核动力系统冗余泵组的可靠性研究

根据核动力系统中设备冷却泵的工作状态,将冗余泵组的中止回阀看成两个冗余阀,得出简化的可靠性分析框图,并建立泵组的可靠性分析模型.以核动力装置设备冷却泵组为例,分别计算泵组在3种情况下的可靠度.计算结果表明,冗余泵组比单个泵工作的可靠性高,但冗余泵组中泵和阀之间的相关失效削弱了泵组的可靠性.     

干熄焦锅炉炉管失效机理分析

通过对干熄焦锅炉炉管及腐蚀产物开展系统研究,提出炉管失效原因为氧化/硫腐蚀＋高温粉尘冲刷。长寿命炉管仅耐磨层发生了较为严重的氧化及硫腐蚀,而近基体层发生了轻微氧化及硫腐蚀,基体只发生了轻微氧化;短寿命炉管耐磨层、近基体层以及基体裂纹内均发生了较为严重的氧化及硫腐蚀,且存在珠光体球化、内表面产生全脱碳层等缺陷。推测短寿命炉管存在超温现象,而超温可加剧氧化及硫腐蚀反应。此外,短寿命炉管遭受了较为严重的高温粉尘冲刷,不仅可造成炉管减薄,还会导致炉管表面温度升高。因此,减少循环气体中粉尘量尤其是大颗粒,可有效减弱冲刷以及控制炉管表面温度,是提高炉管使用寿命的关键。