影响斜拉桥模态参数变化的环境因素分析

Effect analysis of environmental factors on structural modal parameters of a cable-stayed bridge

在环境因素(如温度、交通荷载、风和雨等)的影响下,桥梁结构的动力特性会发生改变。对东海大桥主航道斜拉桥1年的结构状态监测的数据进行了处理,得到了结构模态参数和环境变量的统计结果。基于相干性分析和相关性分析,揭示了影响结构动力特性变化的主要环境因素。研究结果表明在一年的分析周期内环境温度和结构振动水平是影响桥梁模态频率变化的主要因素,而风速只有达到一定的幅值以后才会对结构的模态参数产生较为显著的影响。研究还表明这三个因素在不同的时间尺度上影响结构的动力特性:温度主要体现在年时间尺度上,表征结构振动响应强度的加速度RMS更多的体现在一周的时间尺度上,而风速影响则体现在短暂的强风期间。最后讨论了环境因素影响结构模态参数的机理。

Influenced by some environmental factors,such as,temperature,traffic loads,wind and rainfall etc.,dynamic properties of a bridge system would change.Here,one year monitoring data of the main navigation channel bridge of Donghai Bridge were analyzed and some statistical results were presented.Based on coherence analysis and correlation analysis,the main environmental factors affecting structural modal parameters were confirmed.It was shown that the temperature and structure vibration magnitude were two main influencing factors on the variation of the bridge modal frequency.The structural modal parameters were significantly affected by wind only when the wind speed was high enough.Moreover,the analysis results showed that these three factors affected structural dynamic properties in different time scale: the temperature change was accountable for yearly variation of the bridge modal parameters,the acceleration RMS(root mean square) indicating the structural vibration intensity was accountable for their weekly variations and the wind affecting structural modal parameters was in transient strong wind interval.Finally,the mechanism of environmental effects on frequency variation was discussed based on the above analysis results.