ABSTRACT
In order to capture the deformation response of a bridge member during load testing, the structure has to be properly instrumented. Image- and video-based measurement techniques have significant advantages over traditional physical sensors in that they are applied remotely without physical contact with the structure, they require no cabling, and they allow for measuring displacement where no ground reference is available. This chapter introduces two techniques used to analyze digital images: digital image correlation (DIC) and Eulerian virtual visual sensors (VVS). The former is used to measure the static displacement response and the latter to capture the natural vibration frequencies of structural members. Each technique is introduced separately, providing a description of the fundamental theory, presenting the equipment needed to perform the measurements, and discussing the strengths and limitations. Case studies provide examples of real-world applications during load testing to give the reader a sense of the advances and opportunities of these measurement techniques.
