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  • A General Spectral Difference Method for Calculating the Minimum Safety Distance to Avoid the Pounding of Adjacent Structures during Earthquakes

    A General Spectral Difference Method for Calculating the Minimum Safety Distance to Avoid the Pounding of Adjacent Structures during Earthquakes [J]. Engineering Structures. Zhi-wu Yu(余志武) , Han-yun Liu(刘汉云), Wei Guo*(国巍), Qun Liu(刘群) accepted. 

    本文的主要研究内容为:With the development of cities, buildings have become increasingly concentrated. Therefore, there are serious potential collision dangers between the adjacent buildings or the building partitions under earthquakes, hence buildings need to set the appropriate safety distance to avoid pounding. However, the calculation of the minimum safety distances (MSD) of the adjacent buildings in Chinese Code is rough and arbitrary, while the traditional response spectrum method is derived based on the assumption of proportional damping and it is difficult to consider the non-proportional damping characteristics for large and complex building systems. Based on the above, this paper proposes a new general spectral difference method (gSDM) to calculate the MSD. First, the pseudo-excitation method is used to derive the relative displacement random expression of adjacent buildings during earthquakes. Then, combined with the response spectrum method, the gSDM formula is established, in addition, the explicit expressions of combination coefficient in the gSDM formula are given. Finally, the examples of two adjacent multi-storey shear-buildings are used to illustrate the accuracy and wide adaptability of the gSDM during the El-Centro earthquake. The results compared and discussed in detail with the classical spectral difference method (cSDM), SRSS method and time history analysis.


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    2017-7-22
  • 竖向地震作用下薄壁箱梁的剪力滞后效应

    摘要:为了研究竖向地震作用下薄壁箱梁的剪力滞后效应,对结构设定了三个位移函数,利用哈密顿原理建立了箱梁在竖向地震作用下的振动控制微分方程和相应的边界条件,并对方程进行了求解。根据方程的解可计算竖向地震作用下箱梁的动力响应。为了能更简单的反应结构的滞后程度,给出了剪滞比的定义,随后以悬臂箱梁为例进行了计算分析。研究结果表明:较小的地震动幅值引起了较大的应力响应幅值和明显的剪力滞后效应,在共振频率区域尤其显著;转动惯量对应力幅值的最大影响很小,但对结构振动时的滞后效应影响较大,不可以忽略;增大跨款比能减弱结构的滞后效应,但也增大了结构的内力,工程中应保持合适的跨款比。
    2017-4-7
  • 一种基于非线性接触关系的新型二维轮轨耦合单元及OpenSees实现

    一种基于非线性接触关系的新型二维轮轨耦合单元及OpenSees实现

    古泉1  李维泉1  国巍2,3*  刘永斗1  蒋丽忠2,3  余志武2,3

    1.厦门大学建筑与土木工程学院,厦门 3610002.中南大学土木工程学院,长沙 410075

    3.高速铁路建造技术国家工程实验室,长沙,410075)

    摘要:本文基于轮轨竖向非线性接触关系,提出一种新型通用的二维轮轨耦合单元模型,并在有限元OpenSees软件平台上实现。所提单元由轮节点和与之接触的梁单元节点组成,通过建立和求解轮轨作用力的一元三次方程,得到轮轨之间的接触力,继而计算由于轮轨相互作用产生的耦合单元各节点力,定义为单元内力,其中不包括梁单元内力。通过与文献中计算结果对比,验证了该单元模型的准确性和可靠性,并基于此模型分析了高速列车通过桥梁时在轨道不平顺激励和地震作用下的动力响应。此耦合单元模型易于集成到有限元计算平台中,和已有的列车模型、轨道和桥梁等模型联合使用,能够考虑轨道不平顺和轮轨脱离等情况,可用来分析复杂的竖向车桥耦合系统的动力问题。


    由图5所示,基于本文轮轨耦合滑动单元计算所得的质块竖向位移和简支梁跨中挠度时程曲线与文献3阶模态解析解(标注为解析解)和曾庆元(标注为数值解)数值解高度吻合;质块的加速度时程曲线与文献数值解在趋势和数值上均吻合的很好,但是在末段,本文耦合单元模型数值解结果与3阶数值解有一定偏差,考虑到解析解仅考虑了3阶模态,其误差几乎是可以忽略,完全满足工程需求。

    本文基于轮轨非线性接触关系提出了一种新型二维轮轨耦合单元。所提单元由轮节点和与之接触的梁单元节点组成,通过建立和求解轮轨作用力的一元三次方程,得到轮轨之间的接触力,继而计算由于轮轨相互作用产生的耦合单元各节点力,定义为单元内力,其中不包括梁单元内力。由于此耦合单元采用有别于传统有限元概念的单元内力和位移的定义方式,大大降低了加入现有的通用有限元框架的难度,使得该单元非常实用且能够方便的加入现有的通用有限元框架。并体现与其他方法不具备的优势:(1)能够同时模拟弹性接触和密贴接触两种接触关系,即可考虑车辆跳轨情况;(2)能够分析轨道不平顺激励的影响。



    2017-4-6