Study on Solid-Liquid Two-Phase Flow on PWR Sump Clogging Issue

It has been a concern that sump screen clogging would occur in pressurized water reactors (PWRs) in the case of a loss-of-coolant accident (LOCA), because two-phase jet flow would strip off thermal insulation from the piping and wash down the broken and fragmented debris to sump screens. It is necessary for the evaluation of the effectiveness of sump screens to estimate the amount of transported debris from a break position to sumps. In general, conservative logic trees have been used to determine debris transport rates. Realistic debris transport evaluation is useful for considering measures and rational decision making in licensing. The purpose of this study is to develop a debris transport evaluation model and to apply the model to this issue. We developed a solid-liquid multiphase model that is capable of simulating debris transport, settling, and resuspension. The model is able to treat solid particles of different sizes, which are smaller than uniform-sized liquid particles. This approach contributes to reducing the calculation cost in a large-scale simulation. The model and a turbulence model were implemented into a code based on the moving particle semi-implicit (MPS) method. Several open-channel hydraulic experiments with fibrous debris were conducted. The code named SANSUI 2.0 was validated by the comparison of the analytical results with experiments. This method was applied to the debris transport analysis of a full-scale PWR containment vessel floor, and the debris transport behavior was evaluated.     

蜂巢芯空心楼盖足尺试验研究及有限元分析

为准确掌握新型蜂巢芯空心楼盖的结构性能,进行了足尺九柱四区格蜂巢芯空心楼盖的破坏性静力加载试验研究。分区格进行了5种工况的加载试验,得到了楼盖结构的荷载-挠度曲线,测定了楼盖的整体极限承载能力。试验结果表明,蜂巢芯空心楼盖裂缝出现和分布情况与一般的实心板无梁楼盖基本相同,变形能力也与实心板楼盖类似。利用ANSYS软件对蜂巢芯空心楼盖在均布荷载下的受力进行了非线性有限元分析,并进行了计算开裂荷载、破坏荷载及荷载-挠度曲线和实测值的对比,结果表明两者吻合良好。     

门式刚架含缺陷外伸式端板梁柱节点有限元分析与试验研究

对1个符合规范要求(无缺陷)和3个不符合规范要求(含缺陷)的门式刚架外伸式端板连接节点进行了承载力试验及相应的有限元分析,以了解实际工程中存在的含缺陷节点的力学性能,并对该类节点在正负弯矩作用下的性能进行了有限元分析。研究结果表明:在节点域屈曲起控制的节点中,节点域设置加劲肋对提高节点的承载力作用相当显著;相对于梁端板和柱翼缘同时加厚的无缺陷节点,含缺陷节点的极限承载力基本接近,但其弹性抗弯能力下降、初始转动刚度有所下降,其性能分析适合采用半刚性理论。所采用的有限元分析方法结果可靠,可为含缺陷节点的门式刚架结构的整体受力分析或后续加固提供依据。     

咸阳国际机场T3A航站楼屋盖圆管相贯节点试验研究

西安咸阳国际机场二期扩建工程T3A航站楼的钢结构屋盖节点形式采用构造复杂的空间加强套管相贯节点。由于节点构造复杂,不能简单按现行钢结构规范进行极限承载力计算,为考察节点的受力性能,对三个足尺试件模型进行试验研究,并运用有限元的方法进行分析。试验结果表明,试件的承载力均能达到SJ2c支管设计荷载水平的1.8倍以上,且试件无宏观破坏现象。试验和有限元分析结果证明,节点采取加焊套管的加强措施是有效的。     

全尺寸超、特高压交流绝缘子串的覆冰闪络特性

线路绝缘子的覆冰闪络是影响线路安全稳定运行的重要问题。为此提出了基于恒压升降法获取交流绝缘子串覆冰闪络电压的程序和方法,通过此方法可得到绝缘子串的50%覆冰闪络电压。试验在中国电力科学研究院特高压直流试验基地污秽及环境试验室人工气候罐内(直径22m、高34m)进行,在全尺寸条件下,利用上述方法分别完成了交流500、750、1 000kV等级线路绝缘子串的覆冰闪络特性研究。提出了用统计覆冰桥接程度来评估带电绝缘子串覆冰严重度。结果表明:随覆冰时间的增长,在固定电压等级运行电压下覆冰的绝缘子串桥接程度首先急剧增加,之后达到一定的饱和值。在试验尺寸范围内,串长和闪络电压之间具有较弱非线性关系。结合泄漏电流典型特征分析,严重覆冰条件下绝缘子串闪络在带电融冰期可分为"调整阶段"和"危险阶段"2个阶段。     

广州市翠湖山庄工程钢管混凝土柱节点足尺静载试验研究

广州市翠湖山庄工程采用了新型钢管混凝土环梁节点,并进行了足尺构件静载试验.文中详细介绍试验方案的设计、试件的制作、加荷方式、试件的裂缝发展情况及破坏形态等试验结果.足尺试验研究表明,合适的设计可以保证新型钢管混凝土环梁节点有足够的抗弯、抗剪能力及良好的延性,易于实现"强柱弱梁"的抗震要求.     

Large-eddy simulation of wind effects on a super-tall building in urban environment conditions

A combined study of large-eddy simulation (LES), wind tunnel testing and full-scale measurement is conducted for the evaluation of wind effects on a super-tall building in a complex urban area. To validate the numerical simulations, the wind tunnel experiments including synchronous multi-pressure and high-frequency force balance model tests are conducted in a boundary layer wind tunnel laboratory. The numerical predictions are then compared with the experimental results, demonstrating that the LES can provide comparable predictions of the wind effects on the super-tall building. Furthermore, the cross-validation of the predicted displacement responses by the LES against the wind tunnel and full-scale measurements are presented and the agreement among them is reasonably good. The main objective of this study is to explore an effective numerical approach for the accurate estimation of wind effects on tall buildings in urban environment conditions and promote the practical use of the LES in the wind-resistant design of complex structures.     

考虑损伤因素的单层平面索网静力试验研究

在单层平面索网玻璃幕墙建筑的使用过程中,单层平面索网作为支承结构,不可避免地会受到各种损伤。为了研究损伤因素对单层平面索网结构静力承载性能的影响,针对尺寸为4.85m×4.85m的4×4网格索网结构足尺试验模型,分别引入索与索之间连接节点失效、索预应力损失、索锚固端破坏这三种损伤因素,进行静力加载试验研究。试验结果表明:横索与竖索连接节点失效几乎不影响单层平面索网结构的承载性能;索预应力损失时,节点索网平面外位移变化率不超过15%;锚固端破坏对结构局部影响较大,节点平面外位移变化率介于18%～36%;损伤因素对节点平面外位移的影响大于索力;损伤的影响取决于损伤程度和损伤位置;相同损伤对结构的影响程度随荷载增加而减小。     

倍增比自适应的图像超分辨率重建

近年来,图像超分辨率重建一直是热门的研究领域,但是对于任意倍增比的超分辨率研究仍然鲜见相应的成果.在高倍增比的情形下,图像清晰度变得较低,肉眼已难以识别图像的内容.随着技术的进步,机器视觉已开始识别清晰度极低的图像,面向任意倍增比的超分辨率技术研究已显得日益重要.通过测试各种代表性的超分辨率算法,本文在进行图像超分辨率的任意倍增比分析之后,根据全尺度质量总和准则提出了一种倍增比自适应的超分辨率重建算法.实验结果表明,所提算法在整个倍增尺度内实现了更好的整体重建性能.     

经历弱震损伤的混凝土框架结构抗火性能试验研究

设计了2榀配筋相同的足尺寸单层单跨混凝土框架KJ1、KJ2,对KJ1先进行模拟经历弱震损伤的低周反复荷载试验,接着进行了固定轴压比下的火灾反应试验,包括升温和降温过程;对KJ2直接进行固定轴压比下的火灾反应试验。研究了混凝土框架在火灾中的温度及变形反应,对KJ1、KJ2在试验后的表观现象、温度曲线、承载力变化等方面进行了对比分析,同时根据简化的温度场初步计算了框架柱的高温极限承载力。通过试验和理论分析比较表明,计算结果与最终试验现象从定性上分析是相符的。