大跨度斜拉桥模态频率的环境影响因素研究

Environmental Effects on Modal Frequency of Long-Span Cable-Stayed Bridges

利用东海大桥结构健康监测系统自2007年以来的风速、温度和加速度数据,研究了环境/荷载因素对东海大桥主航道斜拉桥模态频率的影响规律。结果显示:强风、车辆荷载、温度作用对结构的模态频率均有明显的影响,且影响的时间尺度并不相同——风对频率的影响主要体现在强风期间,车辆荷载则主要在1周、1天、12 h的周期上影响频率,温度作用主要在1年、1天的周期上影响频率;车辆荷载和风荷载很可能通过振动强度(以加速度RMS值表征)的变化间接影响频率;明确的机理仍有待进一步研究。

Based on the data of anemometer,thermometer and accelerometer accumulated from the Donghai Bridge Structural Health Monitoring System( DBSHMS) since 2007,the correlation between the environmental or loading factors and the lower order modal frequencies of the main navigational channel bridge( MNCB) of Donghai Bridge was investigated. The results show that the strong wind,traffic loading and structural temperature have significant effects on the frequency variation,and these three factors dominate in different time scales. Compared with traffic and temperature factors,wind effects on frequency happen in a much shorter period,i. e. only during the strong wind process. Traffic load affects the frequency mainly in such cycles as 1 week,1 day and maybe also 12 hours,while temperature dominates in the cycles like 1 year and 1 day.Traffic and wind loading may influence the frequency in an indirect way by changing the vibration amplitude,and the explicit mechanism needs to be further studied.