Monitoring of Bridge Stability Due to Scour Using Remote and Low-cost Optical Sensors

Download or read book Monitoring of Bridge Stability Due to Scour Using Remote and Low-cost Optical Sensors written by Mohamed Saafi and published by . This book was released on 2008 with total page 51 pages. Available in PDF, EPUB and Kindle. Book excerpt: Scour is the erosion of the stream and banks near foundations, piers and abutments of a bridge which is also referred to as bridge scour. Scour of the bed near bridge piers and abutments has resulted in more bridge failures than all other causes in recent years. Highway bridge failures cost millions of dollars each year as a result of both direct costs necessary to replace and restore bridges, and indirect costs related to disruption of transportation facilities. There are two issues associated with such scour induced damage to bridge pier footings. The first effect is the loss of foundation material which exposes the footing and lowers its factor of safety with regard to sliding or lateral deformation. The greatest loss of sediment to scour occurs at high water velocities, such as during floods. Secondly, pier movement may occur as a result of material loss beside and beneath the base of the footing which produces undesired stresses in the bridge structure and ultimately results in structural collapse. Scour can go undetected for many years until a catastrophic disaster occurs. This problem cannot be entirely eliminated, but can be corrected when scour does occur. A major obstacle in correcting this dilemma is determining when and where the crisis is occurring. Many methods have been used in determining whether or not scour is present. Some of these techniques are permanently attached to the structures and others can be transported from bridge to bridge to measure the scour. Also, some of the current procedures cannot work in some conditions and places. Recently, the National Cooperative Highway Research Program (NCHRP) recognized the need of more research activities to develop, test and evaluate instrumentations that would be both technically and economically feasible for use in monitoring maximum scour depth at bridge piers and abutments. The scour monitoring devices should be low cost, reliable, and capable of installation on or near a bridge pier. Therefore, the objective of this project is to develop a low-cost optical system to detect scour. The proposed optical system was developed and evaluated through large scale scour tests. Results indicated that the proposed sensor is capable of detecting scour depth under flood conditions.