ABSTRACT
ABSTRACT: Bridge scour is the leading cause of bridge failure in the United States. Scour is credited with 95% of bridge collapses that take place in the United States. Because these damages occurs under water and not visible, they went undetected thereby jeopardizing the safety and security of the users. Current techniques for scour detection are extremely labor intensive requiring heavy and special equipment to operate and to transport from bridge to bridge making it expensive to use for a large number of bridges. To overcome the shortcomings of current scour detection techniques, the Center for Transportation Infrastructure Safety and Security at Alabama A&M University is currently developing an innovative, low cost and high resolution technique to remotely and continuously monitor and detect scour at bridge piers and abutments. The proposed technique uses low cost PFOSs and MEMS-based electronics and will be installed around bridge piers and abutments to detect and monitor scour depth. The proposed monitoring system uses an array of polymer optical fibers connected to specially configured MEMS-based electronics e.g., switches, phototransistor, LED, amplifier, detector and multiplexing system to detect and monitor the change in the media. The reflection mode of the optical fiber will be used to detect scour and erosion near bridge support. The principle of the detection system is shown in Figure 1. As shown in Figure 1-a, a MEMS light source generates a light intensity and this light intensity travels in the fiber optic and then reflected back from the end of the fiber. The reflected signal is received by a MEMS-based detection and signal processing system to display the sensor response. The reflected signal depends on the medium in contact with the end of the optical fiber and after calibration this property will be
used to detect scour. For example if the end of the optical fiber is in contact with sediment, the sensor will exhibit a signal reflecting the presence of sediment. When a scour occurs and the sediment is eroded, the sensor displays a different reflection signal indicating that water has replaced sediment and thus scour has occurred and by using an array of these sensors, the depth of the scour can be determined.
