Displacement shape measurement of continuous beam bridges based on long-gauge fiber optic sensing

摘要

Displacement shape is an important index for performance assessment of bridges. It is usually hard to find "reference point" for direct arrangement of displacement transducers on real bridges, and therefore indirect measurement methods using strain sensors attracts increasing attention. A reference-free method for monitoring displacement shape of continuous beam bridges using long-gauge fiber optic sensors is proposed in this article. Firstly, the method for calculating the displacement shape of continuous beam bridges using fiber optic strain sensors along the whole structure was theoretically established. Meanwhile, displacement shape determination of a certain span using fiber optic strain sensors along the corresponding span was also presented for the purpose of cost saving in practical engineering. The presented method is independent of external loads and could be applied to both static and dynamic loads. Results from numerical simulation of a three-span bridge show that both methods could obtain the displacement shape of each span with high precision. Furthermore, experimental results indicate that the presented method could perform online monitoring of time-displacement series at each cross section with high accuracy, and could achieve the displacement shape along the continuous beam bridge at a certain time. Therefore, it could be a convenient reference-free strategy for monitoring the displacement shape of continuous beam bridges in actual engineering.