润扬大桥斜拉桥模态频率识别的环境变异性

为了研究大跨斜拉桥振动特性的环境时变特征,对润扬大桥斜拉桥的实测加速度响应进行了模态参数识别.采用峰值法识别了润扬大桥斜拉桥的主要模态频率,并详细地考察了日常运营条件下实测模态频率的环境变异性.分析结果表明,实际环境条件(交通荷载、环境温度和台风荷载)与斜拉桥实测模态频率存在较为明显的相关关系,主要表现为环境温度的变化对模态频率的影响是长期性的趋势,而交通荷载和风荷载对模态频率的影响则由于荷载的非平稳性呈现瞬时的颤动变化.环境激励下润扬大桥斜拉桥整体振动的模态频率在1天内可以发生约1%～4%的变化,其日平均值在1年中可以发生约1%～2.5%的变化.

Environmental variability in modal frequency identificationof Runyang Cable-Stayed Bridge

In order to investigate the environmental variability in the dynamic properties of long-span Cable-Stayed Bridges,the modal parameters identification of Runyang Cable-Stayed Bridge is performed using the measured acceleration responses.The modal frequencies of the bridge are identified using the peak-picking method and which the environmental variability of the modal frequencies is discussed in detail under daily traffic conditions.The analysis results reveal that the actual environmental conditions including traffic loadings,environmental temperature and typhoon loadings have remarkable correlations with the measured modal frequencies of Runyang Cable-Stayed Bridge.The changes of environmental temperature have a long-term trend influence on the modal frequencies,while the effect of traffic and typhoon loadings on the measured modal frequencies of the bridge presents instantaneous changes because of the nonstationary properties of the loadings.It is indicated that the natural frequencies of vibration modes of the bridge under ambient vibrations vary approximately within 1% to 4% in one day and the average natural frequencies per-day vary approximately within 1% to 2.5% in one year.