Development of a Strain-Based Deformation Estimation System for Multipoint Dynamic Deflection Measurement of Bridges

Real-time monitoring of multipoint dynamic deflections is an important yet challenging task in bridge health monitoring. In this paper, a novel strain-based deformation estimation system (SDES) is developed to offer a viable solution for bridge deformation measurements. The SDES comprises a sensing device and a corresponding deformation estimation algorithm. The sensing device consists of a sensing element integrated with strain sensors and several hinged supports. A mechanics-based methodology, the smoothed local variational method (SLVM), is proposed for the estimation of deformed shapes of the SDES. The SLVM formulation is derived by minimizing the difference between the numerical and experimental curvature fields. In practice, a sensing device is placed on the girder along the bridge length, and its deformation at the location of the hinged support placement that of the girder. Curvature measurements are attained using strain sensors and subsequently input into the SLVM to reconstruct the dynamic deflection. The SDES enables continuous, dynamic, direct deflection measurement, without the need for visual contact or a fixed reference point. Indoor and field validation tests are performed, and the results demonstrate the excellent reconstruction capability of the SDES for multipoint dynamic deflection.