侧风作用下列车—桥梁耦合振动响应的时频特性、概率统计特征及评价准则

The dynamic responses of the coupled rail vehicle-bridge system under crosswind are nonstationary random processes with short duration due to the time-varying and nonlinear characteristics of the system as well as the nonstationary input excitations. In this study, both the time-varying characteristics and energy distribution of the frequency spectra of rail vehicle-bridge dynamic responses are investigated, based on the Wavelet Transform (WT) and Hilbert-Huang Transform (HHT). Meanwhile, the applicability of these two time-frequency techniques, i.e., WT and HHT, in analyzing the nonstationary dynamic responses with short duration is also evaluated. In addition to the time-frequency analysis, the probability and statistical characteristics of the dynamic responses are also studied, in which the numbers of response sample required for the statistical analysis as well as the probability distribution of the peak responses are investigated. Finally, the analysis of time-frequency, and probability and statistical characteristics are used to develop the assessment criteria of the coupled rail vehiclel-bridge dynamic system under crosswind, based on reliability theory. Specifically, the statistical evaluation indexes of the dynamic responses of the coupled rail vehicle-bridge system under crosswind are proposed. Furthermore, the comprehensive evaluation indexes which are expected to be capable of assessing the safety and running comfort of the coupled rail vehicle-bridge system under crosswind are also proposed. This proposed study involves the fundamental and extremely important problems which have strong engineering background. It has important significance in promoting the research of the coupled rail vehicle-bridge system under crosswind, and also has certain practical significance in ensuring both the serviceability of raiway bridges and the safety and running comfort of rail vehicles in strong wind-prone region.

侧风作用下列车—桥梁耦合振动响应是短时非平稳随机过程，这是由系统的时变特性、系统的非线性因素以及系统实际输入激励的非平稳性三个方面共同作用导致。本项目拟采用小波变换和希尔伯特—黄变换技术，研究侧风作用下列车—桥梁耦合振动响应的频谱特性随时间的变化规律和响应的能量分布特征，探明这两种时频分析技术在处理系统短时非平稳响应信号时的适用性。从概率统计特征方面入手，确定响应统计分析中计算样本数量的选取依据，建立响应峰值的概率分布模型。通过响应的时频分析和概率统计特征的研究，并结合可靠度理论，提出侧风作用下列车—桥梁耦合振动响应的统计评价指标和反映系统整体安全性和舒适性的综合性评估指标。本项目的研究内容是与工程紧密联系的关键基础性问题，对促进侧风作用下列车—桥梁耦合振动系统的研究工作具有重要的理论意义，也对保证强风区铁路桥梁的安全运营以及桥上列车的安全、平稳运行具有重要的现实意义。

列车—轨道—桥梁耦合系统的动力响应是短时随机过程，系统内外多种因素，例如：风速、车速、轨道不平顺激励、车轮多边形磨耗、桥梁参数等，均可能对列车—轨道—桥梁耦合振动系统的时变特性、非平稳特性和概率统计特征产生影响。本项目针对列车—轨道—桥梁耦合系统动力响应的时频特性、非平稳特性、概率统计特征和评价准则开展研究。基于小波变换时频分析方法探讨了侧风作用下桥上双车交会过程中列车动力响应在时间域与频率域的联合分布特性。基于多体动力学理论，以国内某高速列车动车车辆为原型，运用多体动力学分析软件SIMPACK建立了列车—轨道耦合动力学模型。采用逆序数检验法和单位根检验法分别对列车动力响应随机过程的平稳性进行了检验。同时，运用Monte-Carlo方法并结合随机过程的相关理论，通过列车动力响应时程样本序列的集合均值和集合相关函数，时间均值和时间相关函数，对列车动力响应的平稳性和各态历经性进行了证明。此外，通过构建基于高斯混合模型的列车振动加速度响应最大值的概率密度分布函数，并结合期望最大化算法对概率模型参数进行最大似然估计，从而对列车加速度响应最大值分布的统计规律以及响应样本数量的选取开展研究。进一步地，基于ANSYS和SIMPACK联合仿真方法建立了列车—轨道—桥梁耦合振动分析模型。以车轮多边形磨耗作为系统的输入激励，详细探究了不同阶数和幅值的车轮多边形磨耗对列车、桥梁和钢轨动力响应指标的影响规律，研究表明车轮多边形磨耗对列车—轨道—桥梁耦合系统的振动响应影响显著。在列车—轨道耦合系统动力响应随机过程平稳性研究的基础上，针对列车—轨道—桥梁耦合系统动力响应的平稳性开展了研究，对比分析了列车运行速度、车轮多边形磨耗和桥梁参数等对列车、桥梁和钢轨动力响应平稳性的影响规律。本项目的研究成果可为列车—轨道—桥梁耦合系统动力响应评价准则的确立提供参考，进而对桥上列车的安全和平稳运行提供保障，同时对桥梁结构的安全运营具有一定的指导意义。