基于功率谱传递和子集抽样原理的高速铁路桥梁地震行车安全性概率研究

The high-speed railways are extending into the mid-west part of China, where earthquakes frequently occur. The terrain conditions in these areas require a large proportion of bridge on railway lines. Further the vibration at the deck level on the bridge is more intense than that at the ground level. These factors make the derailment of the vehicle on bridges during earthquake a real concern for railways in the mid-west part of China. This project intents to investigate the probabilistic approach for the derailment of the high-speed train on bridges during earthquakes, considering the stochastic nature of the earthquake. Firstly, by investigating the dynamic feedback mechanism of the vehicles to the bridge, the vehicle-bridge system is to be equivalently decoupled. Secondly, derive the relation of the spectrum of vibration at the rail level of the equivalently decoupled bridge to that at the ground level, taking account the nonstationarity, partial coherency and wave passage effect of the ground motion; and the probability distribution of the intensity of the rail spectrum will be deduced from that of the intensity of ground motions. Finally, the probability of derailment is obtained through nonlinear rail-vehicle simulations by taking the rail spectrum as stochastic resource. The evolution of the randomness in the rail-vehicle system will be traced using the subset sampling method accompanied by the probability density evolution method; then the probability density of the derailment index will be given. The mechanism and criterion of geometric based derailment, in scenarios of moderate to high intensity earthquakes, will be investigated and adjusted according to shaking table test. This study will provide a simple probabilistic evaluation method for derailment of vehicles on bridges during earthquakes, which is convenient for engineering applications.

我国高铁建设正向地震频发的中西部地区延伸，中西部地形条件决定了线路上桥梁的比例很高，而桥梁面振动往往比地震动更剧烈。因此，地震作用下桥上行车安全性是中西部高铁建设面临的现实问题。鉴于地震动具有巨大的随机性，对地震作用下桥上行车安全性问题，应从概率的角度进行分析。首先，研究车辆对桥梁的动力反馈机理，对车辆-桥梁系统进行等代解耦。其次，考虑地震动的非平稳性、非完全相干性以及行波效应，给出桥梁的演变桥面谱与地震动谱的映射关系；并从地震动强度的概率分布，推导桥面谱强度的概率分布。最后，以轨面谱为随机源，输入车辆-轨道非线性模型进行脱轨概率分析；结合子集抽样和概率密度演化方法，追踪随机源的扩散过程，给出脱轨指标的概率分布。另外，探讨中高烈度地震下的车轮脱轨几何机制和脱轨准则，用震动台试验校准几何脱轨模型。本项目可提供一套便于工程应用的地震下桥上车辆脱轨概率分析的理论。

我国铁路建设向川藏、渝昆地区延伸。这些地区地震动活跃，对桥上车辆安全构成重大威胁。高速列车桥上抗震是高铁系统抗震研究的一项重要内容。项目研究取得如下成果：（1）给出了一种地震下的车-桥解耦分析方法及其适用条件；（2）开发了车-桥高效积分算法和缩减轨道模型；（3）将概率密度演化和子集抽样法引入桥上脱轨概率研究；（4）提出一种桥上脱轨工程化判据——桥面加速度响应谱强度。..研究成果将计算量巨大的地震车-轨-桥耦合振动模拟提高了2个数量级，从而使得工程优化设计、概率分析等需要大量模拟的研究成为可能。首次实现了地震桥上脱轨大系统强非线性的可靠度分析，为科学确定地震预警阈值，桥梁动力可靠度设计等提供了理论支撑和分析手段。开展了地震条件下桥上车辆脱轨的足尺震动台试验，支撑川藏线、渝昆线高烈度区地震桥上行车安全保障。提出的桥上脱轨的工程化判据概念清晰、计算简单，可直接服务于桥梁抗脱轨设计及地震下桥上脱轨易损性分析。