Analysis of Fiber Optic Traffic Sensors in Flexible Pavements

A series of linear-elastic plane-strain finite-element analyses were conducted on a newly developed fiber optic traffic sensor whose potential uses include traffic classification and weigh-in-motion. These sensors have performed well in the pavement when placed in six-foot-long narrow vertical grooves. The objective of this research was to determine how the sensor functions in this vertical configuration. Results from three finite-element models were correlated to laboratory and field results showing that the pavement groove closes, thereby squeezing the sensor as tires load the pavement around it. As the fiber optic sensor deforms, the intensity of the light passing through the fiber decreases, allowing roadside computer systems to use this intensity for vehicle classification or weigh-in-motion. Laboratory testing of sensors was performed pneumatically to simulate tire pressures, enabling comparable load, optical light intensity, and deflection data to be obtained for bare and encapsulated sensors. In the field, load-deflection data from falling weight deflectometer testing was used to validate the finite-element modeling.