| 摘要: | 目前台灣的橋梁所遭受最大的安全威脅便是基礎沖刷掏空，由於橋墩基礎已裸露，結構之承載力及穩定性不足，當局部沖刷深度加劇且外力作用大於橋墩基礎的承載力時，橋墩可能會下陷、傾斜、側移，更嚴重的可能會倒塌。本研究所開發的壓電片沖刷監測系統，結合網路達到遠端即時監測之功能，沖刷監測數據資料經由高速的網路傳送，工程人員只須在遠端的主控室即可監控所轄安裝有監測系統的橋梁，並且透過其中之橋梁沖刷安全性評估軟體，可即時掌控橋梁的健康狀態，並對損壞的橋梁發布警告、封橋與進行修復搶災的工作，達到即時迅速的安全預警效果，並可提供相關單位進行緊急應變措施或維修的參考。本研究所開發之壓電片沖刷監測計，具有耐久、穩定、經濟等特色，主要設計理念在於，壓電薄膜在擺動變形時可產生電壓，利用此原理，壓電薄膜在水中受到水流的擺動會產生電壓，而埋於土壤中的則不會有反應，藉由量測一連串沿墩柱基礎分部的壓電薄膜所輸出的電壓，即可測得沖刷所在深度及回淤的動態變化，目前已完成實驗室測試，並安裝於現地橋梁。本研究除沖刷監測儀器之開發外，另對後續之沖刷深度與橋梁安全性之關係作一評估的分析，並提出三種檢核方式作為封橋時機的參考。 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. |
