自激非平稳振动数据驱动的拉索动力性能表征

Representation of dynamic performance of stay cables driven by self-excited non-stationary vibration data

跨海斜拉桥的拉索在非极端风环境下会产生自激振动,基于现代监测与数据分析技术可即时把握拉索自激振动的数字特征,并以此反映拉索的实时动力性能。根据某跨海大桥主航道斜拉桥拉索振动加速度长期监测数据中的共性特征,提出基于振动加速度时间序列信号上包络线高斯混合模型和频域功率谱的拉索风致自激振动非平稳段自动提取方法。提出基于各自激振动非平稳时间序列进行主导频率识别,并采用带通滤波后的最后1个下降段数据进行阻尼比识别的策略,排除了振动幅值上升段环境风自然激励带入能量对阻尼比识别的干扰。基于各自激振动非平稳段主导频率-阻尼比的识别结果,通过对频率值进行聚类,得到各阶模态对应的模态频率-阻尼比数据簇。根据阻尼比数据的离散、偏态特征提出采用对数正态分布模型的e^(μ)和其累积分布函数的分位值来描述拉索阻尼比统计规律。采用各数据簇的频率质心以及阻尼比概率特征参数作为表征拉索动力性能当前状态的指标。针对背景工程的主要结论包括:桥梁拉索振动加速度信号噪声强、干扰大,在动力特征分析时须排除类似干扰;桥梁拉索的自激振动加速度幅值最高已超过3000 mm/s^(2),振动幅度较大;桥梁拉索的阻尼比平均水平约为0.03%,与设计规范推荐值相比偏低。

Stay cables of cross-sea cable-stayed bridges will generate self-excited vibrations in non-extreme wind environments.Based on technologies of modern monitoring and data analysis,the digital features of the self-excited vibration of the stay cable can be captured immediately,and the real-time performance of dynamics about stay cables can be reflected accordingly.According to features of commonality in the long-term monitoring data of vibrating acceleration of stay cables from a main channel cable-stayed bridge of a cross-sea bridge,an automatic extraction method for the non-stationary sections of wind-induced self-excited vibration of the stay cable is proposed based on the vibrating acceleration time series signal’s Gaussian mixture model of the upper envelope and the power spectrum of the frequency domain.The strategies,that identify the dominant frequency based on the non-stationary time series of self-excited vibration,then identify the damping ratio using the data of the last descent section after band-pass filtering,are proposed.By the proposed strategies,the interference on the damping ratio identification from energy brought by the natural excitation of the ambient wind in the ascent sections of the vibration amplitude is excluded.Based on the identified results of dominant frequency-damping ratio in the non-stationary sections of the self-excited vibration,data clusters of the modal frequencydamping ratio corresponding to each order of the vibrating mode are obtained by clustering the frequency values.According to the discrete and skewed characteristics of the damping ratio data,the statistical law of using the e^(μ)of log-normal distribution model and the quantile value of its cumulative distribution function to describe damping ratio of stay cables is proposed.The frequency centroid of each cluster,as well as the probability characteristic parameter of damping ratio are used as indicators to represent the current state of the dynamic performance of stay cables.The main conclusions for the background engineering include:the signal of vibrating acceleration of stay cables on the bridge has strong noise and large interference,they must be eliminated in the analysis of dynamic characteristic;the amplitude maximum of the acceleration of the self-excited vibration of the bridge’s stay cable has exceeded 3000 mm/s^(2),the vibration amplitude is large;the average level of the damping ratio of the bridge’s stay cable is about 0.03%,which is lower than the recommended value of the design code.