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Monitoring and structural analysis of a rehabilitated box girder bridge based on long-gauge strain sensors

Structural rehabilitation is playing an increasingly important role in civil engineering owing to issues with aging infrastructure. In this context, a feasible inspection and monitoring system is needed to draw up effective structural rehabilitation projects. This article presents a case study of a real box girder bridge strengthened via external post-tensioning. With the aim of evaluating the strengthening project and the structural behavior changes, a large-scale strain sensing system containing four sensing areas was installed on the bridge before strengthening, and the static and dynamic strain distribution changes were recorded during annual inspections. The text focuses on discussing and comparing the variations of strain distribution across the bridge before and after strengthening, as well as the yearly changes the rehabilitated bridge has undergone. From the measured strain responses, we accurately determined that the rehabilitated bridge had undergone an unexpected reduction in its flexural stiffness as well as a torsion action. Moreover, finite element analysis results of three different damage models are discussed to understand the detailed cause for this.