Seismic Evaluation of Multi-Storey RC Frame Using Modal Pushover Analysis

The recently developed pushover analysis procedure has led a new dimension to performance-based design in structural engineering practices. With the increase in the magnitude of monotonic loading, weak links and failure modes in the multi-storey RC frames are usually formed. The force distribution and storey displacements are evaluated using static pushover analysis based on the assumption that the response is controlled by fundamental mode and no mode shift takes place. Himalayan-Nagalushai region, Indo-Gangetic plain, Western India, Kutch and Kathiawar regions are geologically unstable parts of India and some devastating earthquakes of remarkable intensity have occurred here. In view of the intensive construction activity in India, where even a medium intensity tremor can cause a calamity, the authors feel that a completely up-to-date, versatile method of aseismic analysis and design of structures are essential. A detailed dynamic analysis of a 10-storey RC frame building is therefore performed using response spectrum method based on Indian Standard Codal Provisions and base shear, storey shear and storey drifts are computed. A modal pushover analysis (MPA) is also carried out to determine the structural response of the same model for the same acceleration spectra used in the earlier case. The major focus of study is to bring out the superiority of pushover analysis method over the conventional dynamic analysis method recommended by the code. The results obtained from the numerical studies show that the response spectrum method underestimates the response of the model in comparison with modal pushover analysis. It is also seen that modal participation of higher modes contributes to better results of the response distribution along the height of the building. Also pushover curves are plotted to illustrate the displacement as a function of base shear.     

黄土洞穴对公路危害的地质模式及致灾机理

作为黄土地区一种重要的不良地质现象,黄土洞穴对各种工程都造成了不同程度的危害,其中以对公路的危害最为突出。黄土洞穴对公路路基、边坡、桥梁、隧道和排水设施都有不同程度的危害,而且这些危害在型式、主要危害的部位及危害的严重程度等方面都有一定规律。为了从根本上认识黄土洞穴对公路的危害的规律和机理,指导公路黄土洞穴稳定性评价和防治,本文在对陕西省和甘肃省公路黄土暗穴调查的基础上,根据黄土洞穴对公路工程不同部位的破坏特征总结出黄土洞穴对公路路基、边坡、桥梁、隧道和排水设施危害的地质模式和致灾机理。     

多自由度内共振系统非线性模态的分岔特性

利用多尺度法构造了一个立方非线性1:3内共振系统的内共振非线性模态(NonlinearNormal Modes associated with internal resonance)．研究表明,内共振非线性系统除存在单模态运动外还存在耦合模态运动．耦合内共振模态具有分岔特性．利用奇异性理论对模态分岔方程进行分析发现此类系统的模态存在叉形点分岔和滞后点分岔这两种典型的分岔模式．     

复杂梁动力问题的近似分析方法

本文介绍了在各种复杂条件下，分析梁振动特性的一个近似方法－模态摄动法。这一方法是在等截面均匀梁的模态子空间内实施，将复杂梁的变系数微分方程的求解转化为代数方程组的求解。通过算例，表明这一方法简单实用，且有良好的近似性。     

加筋板结构的大变形

本文对受均布载荷，具有一根纵向加筋多根横向加筋的加筋板结构的残余变形导出了近似理论分析方法。从假设变形模态出发，依据极限分析原理获得可能变形模态和模态判别条件。在变形分析中，计及膜力（轴力）影响，但忽略弹性影响，得到了各变形模态下的残余变形估算公式。最后根据本文的理论分析方法和ＡＤＩＮＡ程序作了实例计算，两者的变形模态和最大残余变形均十分一致     

Lee极值原理与结构的大挠度塑性动力响应

本文介绍了利用Lee 极值原理确定结构的大挠度塑性动力响应的数值方法,给出了在均布冲击载荷作用下的理想刚塑性门形框架的大挠度进化模态解,指出如果模态形式取得合适,可使进化模态解接近于真实解.这样得到的门形框架的大挠度模态解与文献[8]中的实验结果和文献[9]中的大挠度完全解都符合得很好.     

双层碳纳米管中的周向导波

考虑双层碳纳米管的层间范德华力,采用连续介质力学的波动理论,建立了双层碳纳米管中周向导波传播模型,研究周向导波的频散现象.通过与单层碳纳米管结果的比较表明,双层碳纳米管中周向导波的传播表现出更为明显的频散特性,出现更多的模态干涉现象,并发现在某些特殊频率处出现成对模态的消失与新启现象.     

加注稀土元素铒改善轴承表面性能的研究

在Ｍｏ＾＋＋Ｎ＾＋注入模式的基础上，应用电子能谱、卢瑟福背散射谱、扫描电子显微镜和ＭＨＫ－５００型摩擦磨损试验机等研究了加注稀土元素铒正离子Ｅｒ＾＋对轴承表面摩擦学性能和耐蚀性能的影响。结果表明，在合理配置Ｍｏ＾＋、Ｎ＾＋、Ｅｒ＾＋之能量和剂量的情况下，加注Ｅｒ＾＋既能更好地改善轴承的表面性能，又能使重离子的强韧化效果提高２－４倍以上，表明ＭＯ＾＋＋Ｎ＾＋＋Ｅｒ＾＋注入模式是一种具有良好应用前景的     

FRET Enhancement in Aluminum Zero‐Mode Waveguides

Zero‐mode waveguides (ZMWs) can confine light into attoliter volumes, which enables single molecule fluorescence experiments at physiological micromolar concentrations. Of the fluorescence spectroscopy techniques that can be enhanced by ZMWs, Förster resonance energy transfer (FRET) is one of the most widely used in life sciences. Combining zero‐mode waveguides with FRET provides new opportunities to investigate biochemical structures or follow interaction dynamics at micromolar concentrations with single‐molecule resolution. However, prior to any quantitative FRET analysis on biological samples, it is crucial to establish first the influence of the ZMW on the FRET process. Here, we quantify the FRET rates and efficiencies between individual donor–acceptor fluorophore pairs that diffuse into aluminum zero‐mode waveguides. Aluminum ZMWs are important structures thanks to their commercial availability and the large amount of literature that describe their use for single‐molecule fluorescence spectroscopy. We also compared the results between ZMWs milled in gold and aluminum, and found that although gold has a stronger influence on the decay rates, the lower losses of aluminum in the green spectral region provide larger fluorescence brightness enhancement factors. For both aluminum and gold ZMWs, we observed that the FRET rate scales linearly with the isolated donor decay rate and the local density of optical states. Detailed information about FRET in ZMWs unlocks their application as new devices for enhanced single‐molecule FRET at physiological concentrations.     

Histidine‐modified organic‐silica hybrid monolithic column for mixed‐mode per aqueous and ion‐exchange capillary electrochromatography

A novel organic‐silica hybrid monolith was prepared through the binding of histidine onto the surface of monolithic matrix for mixed‐mode per aqueous and ion‐exchange capillary electrochromatography. The imidazolium and amino groups on the surface of the monolithic stationary phase were used to generate an anodic electro‐osmotic flow as well as to provide electrostatic interaction sites for the charged compounds at low pH. Typical per aqueous chromatographic behavior was observed in water‐rich mobile phases. Various polar and hydrophilic analytes were selected to evaluate the characteristics and chromatographic performance of the obtained monolith. Under per aqueous conditions, the mixed‐mode mechanism of hydrophobic and ion‐exchange interactions was observed and the resultant monolithic column proved to be very versatile for the efficient separations of these polar and hydrophilic compounds (including amides, nucleosides and nucleotide bases, benzoic acid derivatives, and amino acids) in highly aqueous mobile phases. The successful applications suggested that the histidine‐modified organic‐silica hybrid monolithic column could offer a wide range of retention behaviors and flexible selectivities toward polar and hydrophilic compounds.