排序方式: 共有34条查询结果,搜索用时 421 毫秒
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地震作用下,饱和砂土地层地铁车站的动力反应特征是城市轨道工程抗震的关键问题。以太原地铁新近沉积粉细砂地层地铁工程为对象,通过模拟地震运动输入的饱和砂土地基地下结构的振动台模型试验,分析了不同峰值加速度地震作用下饱和砂土与地下结构相互作用的动力反应性状。研究了地震波作用的放大效应与频率特征,动孔压比增长发展过程和液化区域分布,以及动土压力的变化规律。表明加速度放大系数为1.5~2.0;0.1~0.25g峰值加速度地震作用下饱和砂土均产生动孔隙水压力累计发展;0.3g峰值加速度地震作用下饱和砂土产生液化,抑制了土与地下结构的振动放大效应,地表面大量冒水,结构模型出现了明显上浮,地下结构两侧产生震陷。 相似文献
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鉴于目前常用的剪切波速测试法、液性指数法和原位测试法等进行砂土震动液化的复判方法存在弊端,本文提出标准贯入击数--锥尖阻力复判法( qc--N 复判法) 及瑞利波法等间接测试击数的方法进行砂土震动液化判别。通过理论计算及实例验证表明,判别结果与相对密度法测得结果一致,同时具有工作效率高、生产成本低的优点,有较高的实际应用价值。 相似文献
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The present work evaluates the possibility of using dynamic data to assess structural integrity. It addresses the problem of understanding when it is sufficient to measure and use only natural frequencies, thus avoiding the need to measure modal shapes. The classic problem of detecting damage in beams, or beam assemblies, due to concentrated cracks, or damage spread over a structural member is dealt with. Damage is represented as a decrease in stiffness and linear behaviour before and after the event assumed to have caused damage is considered. Damage is restricted to a few unknown sections or elements, so that only the modification of few parameters of the system need to be determined. This study thus rejects assumptions unrelated to the physical aspects of the problem, in contrast to many papers on the subject. The amount of data to locate and quantify damage correctly is discussed; general considerations lead to the conclusion that a unique and reliable estimate of the damage can be obtained using only few additional frequency data with respect to the number of damaged zones. Continuous and discrete (finite element) models are examined. Finally the paper considers the applications to both analytical and experimental data of the procedure developed, which takes account of the peculiar characteristics of damage detection problem. Copyright © 1999 John Wiley & Sons, Ltd. 相似文献
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Hugo Oliveira François Louf Estelle Hervé-Secourgeon Fabrice Gatuingt 《国际地质力学数值与分析法杂志》2020,44(1):19-39
In numerical models, the connections among component members are crucial for the prediction of structural behaviour under different types of solicitations. In reinforced structures, the connections are often assumed rigid, what may not be realistic in many practical cases. As alternative, a semi-rigid behaviour depending on a set of independent parameters can be proposed. In this case, a new difficulty arises, which is finding the appropriate values for those parameters. The present study proposes a numerical strategy for identification of the connection parameters based on the constitutive relation error (CRE). To include all available information, an augmented version (Modified CRE) is implemented. The parameters search is iterative and require large amount of system response analysis. To increase the computational efficiency, a reduced order model is adopted. The proposed approach shows low-sensitivity to limited lack of information and also to support condition variability, both of them verified numerically. In this work, experimental tests for a real 1:4 scale structure is utilized for finding the parameters corresponding to the first three modal shapes. A good agreement between numerical predictions and observations is verified, what highlights the accuracy and stability of the proposed numerical approach. The present study may also find applications in the domain of design of experiments. 相似文献
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现有的静力试桩方法主要有堆载法、锚桩反力架法和自平衡法3种,且各自都存在明显的不足。为了弥补传统基桩静载试验的不足,设计并加工了一套能在工程实践中应用的真空负压静力试桩的反力装置,并进行了原型桩堆载和真空负压静载试验。在试桩上安设了钢筋应力计、桩底土压力盒和桩底位移杆监测传感器及装置,借鉴了地基真空预压排水预压密封系统的措施,形成了有效的密封反力系统。分析了试桩在加载过程中的荷载-位移(Q-s)曲线、位移-时间(s-lgt)曲线,以及轴力、桩侧摩阻力和桩端摩阻力的分布规律。试验表明,桩侧摩阻力的发挥与抽真空过程密切相关。由于负压平台的刚度、压力传递和密封效果原因,真空负压最大加载量级与理论值存在一定差距,针对上述问题提出了相应的解决方案和改进措施。 相似文献