Nondestructive evaluation is an important tool for assurance of proper construction practices and selection of rehabilitation procedures for civil infrastructure. Improvements in technology for testing of concrete structures, such as the introduction of dry point contact ultrasonic arrays, allow for collection of repeatable and spatially diverse shear wave impulse time-histories. This dissertation deals with development of methods that can be used for quantitative evaluation of concrete pavement structures using ultrasound linear array systems. The synthetic aperture focusing technique was adapted to handle spatially diverse measurement pairs. Kirchoff migration and the Hilbert transform were utilized to correlate high intensity portions of the instantaneous amplitude time history envelopes to the physical location of changes in acoustic impedance of the tested medium. To mitigate the effect of limited aperture, the interpretation methods were generalized to accommodate virtual array systems and implemented to create two- and three-dimensional reconstructions of the subsurface concrete structure. This reconstruction analysis was applied for practical pavement problems such as reinforcement and layer boundary location, as well as stochastic flaw detection. Comprehensive ground truth validation on several full-scale concrete pavements confirmed the high resolution of the analytical tools developed in this dissertation.
展开▼
