Quantitative Measurement of Strain in Reinforced Concrete Structures Using Calibrated Optical Fiber Sensors

Abstract

This paper discusses the use of calibrated, quantitative optical fiber sensors for the internal diagnostics of reinforced concrete structures. Prior optical fiber sensor methods for the monitoring of reinforced concrete specimens and structures during fabrication, laboratory testing and field use first are reviewed. Much of this work has concerned either techniques for embedding optical fibers in concrete without severe damage to the fiber, or the use of qualitative and uncalibrated sensors to infer the general conditions within the concrete. Here we report the use of practical, short gage length relative strain sensors for the measurement and mapping of strain in reinforced concrete beam and crossbeam configurations, and issues in the implementation of absolute rather than relative strain measuring optical fiber sensors. Both types of fiber sensors were attached to rebar reinforcement rods prior to filling with concrete, and were colocated with conventional foil strain gages to allow direct comparison of output signals. By using conventional robust fiber cabling into the specimens, no difficulties due to fiber breakage were encountered.