This Small Business Innovation Research Phase I project will investigate a novel means of measuring the relative motion (displacement and velocity) between a structure and the medium in which it is embedded when the system is subjected to shock loads, such as those from earthquakes. The complexity of the behavior at the structure-medium interface poses a large source of uncertainty in design and analysis of man-made structures that are partially or totally embedded in a medium. The proposed method involves the use of an encapsulated and collimated radioisotope source located in the medium near the structure-medium interface and an array of plastic scintillating fibers embedded in the structure. As the source and fibers move relative to each other, the collimated source beam penetrates the intervening material and sweeps across the fiber array, exposing different fibers at different times. The displacement and velocity of the source (medium) relative to the fibers (structure) can be determined from the fiber count-rate time histories. Key features of the proposed approach include: the instrument minimizes interference with the motion at the interface; the fibers can be fabricated into ribbons, which maintain inter-fiber registration but are flexible and rugged; and the system can achieve high spatial resolution and high data collection rates. Phase I will involve design, modeling, and experimental testing of a laboratory system, in order to demonstrate proof-of-principle. Instruments for field evaluation would be developed and extensively tested in Phase II.
