Response of train-bridge system under intensive seismic excitation by random vibration method

Abstract

Earthquake is a kind of sudden and destructive random excitation in nature. It is significant to determine the probability distribution characteristics of the corresponding dynamic indicators to ensure the safety and the stability of structures when the intensive seismic excitation, the intensity of which is larger than 7, acts in train-bridge system. Firstly, the motion equations of a two-dimensional train-bridge system under the vertical random excitation of track irregularity and the vertical seismic acceleration are established, where the train subsystem is composed of 8 mutually independent vehicle elements with 48 degrees of freedom, while the single-span simple supported bridge subsystem is composed of 10 2D beam elements with 20 degrees of freedom on beam and 2 large mass degrees of freedom at the support. Secondly, Monte Carlo method and pseudo excitation method are adopted to analyze the statistical parameters of the system. The power spectrum density of random excitation is used to define a series of non-stationary pseudo excitation in pseudo excitation method and the trigonometric series of random vibration history samples in Monte Carlo method, respectively solved by precise integral method and Newmark-β method through the inter-system iterative procedure. Finally, the results are compared with the case under the weak seismic excitation, and show that the samples of vertical acceleration response of bridge and the offload factor of train obeys the normal distribution. In a high probability, the intensive earthquakes pose a greater threat to the safety and stability of bridges and trains than the weak ones.

摘要

地震荷载是自然界中一种突发并且对结构具有一定破坏性的随机激励。当震级大于6级即地震 烈度在7 以上的地震即**震作用在车桥耦合系统中时,确定系统响应的概率分布特性用于保障行车和 结构安全稳定十分重要。因此,本文分别采用蒙特卡洛实验法以及虚拟激励随机振动分析方法,构建 二维车桥耦合系统空间状态方程,考虑轨道不**顺随机激励和确定性轴重激励,以及通过大质量法输 入地震随机激励,借助精细积分法通过全过程迭代过程对该状态方程进行精确高效求解响应时程分 布。由此确定系统响应及相应动力学指标的概率分布,与非**震条件下的响应概率分布特性对比,最 终为保障行车和桥梁结构安全稳定提供建议。