A local Scouring Monitoring and Safety Warning System of Bridge

• Main Authors: Wen-Kang Fan, 范文綱
• Other Authors: Chung-Yue Wang
• Format: Others
• Language: zh-TW
• Published: 2009
• Online Access: http://ndltd.ncl.edu.tw/handle/e8exwg

碩士 === 國立中央大學 === 土木工程研究所 === 97 === Scour is always the primary threat to bridges in Taiwan area. Since bridges will experience floods which may cause damage from scour holes forming around bridge piers and abutments. As scour changes the geometry of the bridge pier embedded in the soil foundation, the effects due to other loads, such as live load, wind load, debris collision, etc., are amplified. In this condition, bridge may have settlement or tipping even collapse. Therefore it is demanded by the bridge authority agencies to have a monitor sensor to determine the real-time scour depth. Besides, with internet it is easily to handle the real-time information at bridge site to alarm the siren in time from control center through the predefined safety warning algorithm. A piezoelectric fluoropolymer film type real-time scouring monitoring sensor installed along the bridge pier is presented. The core idea of developing this scouring sensing system is based on the physical character that output voltage can be generated as the piezoelectric thin film is deformed by the flowing media. Therefore, a sensing device can be manufactured by mounting piezoelectric thin films along the rod with a fixed distance and insert it into a borehole beside the bridge pier. The piezoelectric film embedded in the soil of riverbed is undeformed and the output voltage is much smaller than the one disturbed by the water current. From the output signals of all the piezoelectric sensors with known locations along the depth of the pier foundation, one can trace the variation of the soil/water interface before, during and after a flood. Compared with other types of scouring sensors, this piezoelectric type scouring sensor is working without power, durable, sensitive, real-time and cost effective. In this paper, the basis theory and the performance that in laboratory of this novel piezoelectric film type scouring device are introduced. The installation of the system in field is also addressed. In this study, it also brings up three methods for readers to analyze the safety of bridge, which can be taken into consideration of blocking a bridge.