Proceedings Article | 8 March 2014
KEYWORDS: Sensors, Bridges, Ferroelectric polymers, Fiber optics sensors, Reliability, Sensor performance, Magnetic sensors, Transducers, Fiber Bragg gratings, Safety
Scour occurring near bridge piers and abutments jeopardizes the stability and safety of overwater bridges. In fact, bridge
scour is responsible for a significant portion of overwater bridge failures in the United States and around the world. As a
result, numerous methods have been developed for monitoring bridge scour by measuring scour depth at locations near
bridge piers and foundations. Besides visual inspections conducted by trained divers, other technologies include sonar,
float-out devices, magnetic sliding collars, tilt sensors, and fiber optics, to name a few. These systems each offer unique
advantages, but most of them share fundamental limitations (e.g., high costs, low reliability, limited accuracy, low
reliability, etc.) that have limited their implementation in practice. Thus, the goal of this study is to present a low-cost
and simple scour depth sensor fabricated using piezoelectric poly(vinylidene fluoride) (PVDF) polymer strips. Unlike
current piezoelectric scour sensors that are based on mounting multiple and equidistantly spaced transducers on a rod,
the proposed sensor is formed by coating one continuous PVDF film onto a substrate, followed by waterproofing the
sensor. The PVDF-based sensor can then be buried in the streambed and at a location where scour depth measurements
are desired. When scour occurs and exposes a portion of the PVDF sensor, water flow excites the sensor to cause the
generation of a time-varying voltage signal. Since the dynamics of the voltage time history response is related to the
exposed length of the sensor, scour depth can be determined. This work presents the design and fabrication of the sensor.
Then, the sensor’s performance and accuracy is characterized through extensive laboratory testing.
