As the civil infrastructure (e.g. bridges) of the global highway system ages,there exists a critical need for structural health monitoring over large areas that isrobust, inexpensive and easily interpreted. According to the American Society ofCivil Engineers, in 2008, 161,892 bridges were structurally deficient or obsolete. Inthe next fifteen years, nearly half of America’s bridges will exceed the typical 50-year design life. Thorough inspection of these aging bridges is important to ensurepublic safety. Currently, bridge health is assessed primarily using qualitative visualinspection, which is subject to variability due to an inspector’s interpretation.Instruments such as strain gages, accelerometers, fiber optic sensors, displacementtransducers, etc. are becoming more common for monitoring bridge health. Thesesensors require external power, cabling/antenna for data transmission, high dataacquisition channel counts and only measure at a discrete point or along a line(making it difficult to detect damage outside the sensor’s proximity). To rectifythese drawbacks, this paper presents research results of using three-dimensional(3D) digital image correlation (DIC) as a new approach for quantitative bridgestructural health monitoring.3D DIC is a non-contact, full field, optical measuring technique that uses twodigital cameras to measure surface geometry, displacement, and strain. Long termmonitoring with DIC can be accomplished by imaging the bridge periodically andcomputing strain, displacement and surface geometry fromimages recorded at different dates. In this paper, DIC is shown to1) quantify spalling by comparing subsequent surface geometry measurements,2) monitor crack width using extensometers established between photogrammetrictargets and 3) successfully locate non-visible cracks using full-field strain anddisplacement measurements. These techniques are first confirmed in laboratorytests.Next field measurements are made on three operational full-scale bridges. Thispaper also discusses the challenges and solutions to effectively implementing DIC
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