Digital Imaging for Bridge Deflection Measurement of a Steel Girder Composite Bridge

Bridge managers have historically relied on visual inspection reports and field observation, including photographs, to assess bridge health. The inclusion of instrumentation including strain gauges, tiltmeters, linear variable differential transformers (LVDTs), and accelerometers along with a structural model can enhance bridge management. This combination of instrumentation and modeling is commonly classified as Structural Health Monitoring (SHM). Traditional SHM measurements are reference-independent, such as strain gauges and tiltmeters. These sensors can be easily installed during the initial construction of new bridge but installation is significant more difficult once the bridge is in service. The collection of global deflection of a bridge, a reference-dependent measurement, is even more difficult to collect as the connection between the bridge structure and a fixed reference is geometrically challenging. A measurement technique that alleviates both of these issues is digital image correlation. Through recent advances in digital photography and the computational capability of personal computers, Digital Image Correlation (DIC) is a non-contact measurement technique that can be cost-effectively deployed to collect global deflection measurements of a bridge structure. DIC uses multiple digital cameras to photograph a target object to provide structural response information. This project incorporates a DIC system into the bridge instrumentation and testing program for a concrete deck-steel girder composite bridge in Barre, Massachusetts. This paper presents a collaborative research project partially funded by the CAREER, Major Research Instrumentation and the Partnerships for Innovation Programs at the National Science Foundation to develop a framework for bridge condition assessment integrating instrumentation and structural modeling for bridge decision-making and management.