Vision-based dynamic monitoring of a post-tensioned concrete bridge under vehicular traffic

Computer vision for the purpose of structural dynamic monitoring of bridges has received much interest in recent years given the possibility of measuring displacement time-histories in absence of stationary points, using hardware that has accessible costs and is easy to operate. The review of the state-of-the-art shows that vision-based monitoring can potentially provide results equivalent to those obtained with the use of well-established contact sensors such as displacement transducers and accelerometers. Applications to real full-scale steel bridges and footbridges showed the possibilities of this technology in real-world conditions as well as difficulties and challenges posed by the surrounding environment. However, despite the many contributions published in the technical literature, very few applications involved post-tensioned concrete bridges, a very common solutions in the Italian road network and in many other countries. Characterized by a stiffer response as compared to steel bridges and footbridges, post-tensioned concrete bridges with their lower displacement magnitude and higher natural frequency might represent a more demanding testbed for vision-based monitoring. Accordingly, this study focused on the performance analysis of a vision-based structural monitoring system when applied to medium-span post-tensioned simply supported concrete bridges. The experimental outcomes show very interesting potentialities together with some critical aspects relevant to the vibrations induced in the tripod supporting the video camera that require attention to ensure the accuracy of the measurements.