Testing of a Prestressed Concrete Girder to Study the Enhanced Performance of Monitoring by Integrating Optical Fiber Sensors

To investigate monitoring of concrete members by integrating fiber optic technology, a series of static and dynamic loading tests have been conducted on a posttensioned concrete girder with a span of 16.8m and a total depth of 0.8m. For strain measurements optical fiber strain sensors, based on Bragg gratings, have been used. In literature only few papers deal with changes of dynamic parameters in posttensioned concrete at increasing damage levels. The obtained test results demonstrate the feasibility of fiber Bragg grating strain sensors, also for dynamic monitoring. On the dynamic behavior of the tested girder, it is found that, although a drop in eigenfrequencies is noticed with increasing load, significant shifts are only measured when the reinforcement starts yielding. Also with respect to damping values, no clear indication of damage in an early stage is observed. Further results show that the curvature of the mode shapes changes with increasing load and is related to the formation of a plastic hinge. An interesting observation is the change in phase angle between the modal strains and the vertical acceleration, which already occurred at an early stage.