Application of Optoelectronic Liquid Lever Sensor in Urban Bridges Deflection Monitoring

The deflection which reflects the bridge linear variety is an important parameter for the evaluation of bridge safety. According to the structural characteristics of urban bridges, the connected pipe optoelectronic liquid level sensor system is a novel kind of sensor for detecting the connected pipe liquid level, which can be applied for multipoint, long-period, online, remote, automatic measurement of bridge deflection, it is not affected by the dust, humidity and fog in the urban bridge health monitoring and maintenance. At present, the system has been integrated and applied in the project of main roads bridge Online Safety Monitoring Management System in Hangzhou (Phase II), a web-based urban bridge cluster monitoring system have been established since 2007. According to a tied arch bridge case studies, the measuring data show that the system not only can accurately collect the bridge normal deflection information and variety, but also successfully monitored the structural responses due to the Wenchuan earthquake on May 12, 2008. About two-minute abrupt changes in displacement amplitude were observed in the measured signals starting at 14:37, about 9 minutes later than the earthquake’s occurring. The results shows, it is an effective method for the real-time monitoring of urban bridge deflection.