ABSTRACT
Post-tensioned concrete is currently one of the most common technology used to construct bridges. For decades it was used to build medium-span bridges over the world and now many of them require diagnostics due to their worsening technical condition. One of the novel diagnostic technique for such bridges can be distributed fiber optic sensing (DFOS). It allows the measurements to be taken continuously over the entire structural length, which is especially important in such structures. The advantages of this method have already been proven in civil engineering applications, especially those related to concrete structures. Thanks to their construction distributed fiber optic sensors can be used for both new and existing structures. The paper presents the research on two post-tensioned beams with curvilinear multiwire strands in which optic sensors have been installed before and after concreting. The main aims of the research was to measure strains, stresses, cracks and displacements, to compare results from monolithic sensors embedded in the concrete (for new structures) and those installed in pre-made near-to-surface grooves (for existing structures) and to identify defects in one of the beam thanks to sensors installed inside the cable duct and the strain itself. The DFOS measurements were also compared with reference measurements made with conventional spot techniques, achieving very good compliance. The research proved that a well-designed DFOS-based system, including appropriate measurement techniques, optical sensors, installation methods and post-processing algorithms, is the relevant tool for the diagnostics of post-tensioned concrete bridges.
