AbstractFiber-optic sensing (FOS) provides distributed strain measurement that can enhance both structural health monitoring (SHM) and laboratory testing capabilities. In particular, optical frequency domain reflectometry (OFDR) provides strain or temperature measurements every millimeter over tens of meters of fiber, with a high sampling rate. For RC applications with embedded fiber-optic cables, the sensitivity of the fibers and their ability to measure and survive cracking are both important considerations. In this study, tests were conducted on six RC specimens to investigate the effectiveness of using OFDR strain sensing to evaluate the cracking behavior of concrete and the deformation of steel reinforcing bars. Six types of fiber-optic cables with very different structures, sensitivity, and survivability were tested. Fibers were placed in the concrete and in grooves in the reinforcing bars. A new deconvolution method was developed; using the method, crack widths were accurately measured up to the target load levels using both the more sensitive fiber-optic cables and cables with reduced sensitivity but better survivability. OFDR strain sensing, combined with new methods of data processing, was shown to be capable of detecting distributed microcracking and providing reliable crack widths. The OFDR technique was also used to reveal the location-dependent bond-slip relationships between the concrete and rebar at early stages.

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