4频率变化的基本现象.docVIP

PAGE \* MERGEFORMAT 1 基于监测数据的斜拉桥模态频率变化特性分析 孙利民1，周毅 同济大学土木工程防灾国家重点实验室，上海 200092 1lmsun@tongji.edu.cn 【摘要】 “基于实测模态频率的变化对桥梁状态进行评估”是本文的出发点。前期研究发现，环境因素可以比结构损伤引起模态频率更大的变化，因而有必要把握环境因素对频率的影响规律，以消除其造成的影响。对东海大桥主航道斜拉桥五年实测数据的分析结果显示，模态频率存在长周期的变化成分，主要的周期成分如1年、1周、1天、12小时等。本文考虑温度、车流等环境因素对第一阶竖弯和第一阶侧弯频率的影响，对频率变化的主要周期成分所产生的原因进行了推测，并在1年、1周、1天、12小时四个周期成分上对频率的变化进行了回归建模。本文的工作可以为基于模态频率变化的结构状态评估提供参考。 【关键词】 结构健康监测；东海大桥；模态频率；环境因素 【Abstract】 Vibration-based structural health monitoring utilizes variation of modal parameters to assess structural condition. However, it was widely recognized by many researches that modal parameters can be influenced by environmental factors and it is necessary to investigate the correlations of environmental factors and structural modal parameters to “normalize” the environmental condition. Based on the long-term monitoring data recorded by the Donghai Bridge Structure Health Monitoring System (DBSHMS) from 2007 to 2011, this paper studied the variation of modal frequencies of the main navigation channel bridge (MNCB), a cable-stayed bridge with a steel-concrete composite girder of 420m central span. The spectral analysis showed that the variation of modal frequencies possessed some long periods components such as 1 year, 1 week, 1 day, 12 hours and so on. Focused on the first vertical bending mode and the first lateral bending mode, this paper took such environmental factors as temperature, traffic loads into consideration and inferred the reasons for those long-period variation components of modal frequency, respectively. Moreover, the regression analyses were also conducted for each variation component. Results of this study could contribute to a better understanding on the behavior of long-span cable-stayed bridges and benefit the maintenance of bridge. 【Keywords】 Structural Health Monitoring；Donghai Bridge；Frequency；Environmental Factors 引言 近20年来，结构健康监测技术在土木工程领域，尤其是在大跨度桥梁上得到了广泛的应用，如亚洲的青马大桥、苏通大桥，欧洲的Great Belt East Bridge、Tamar Bridge，美洲的Confederation Bridg