Mechanics-based algorithms to determine the current state of a bridge using quasi-static loading and strain measurement

Knowing the current state of a bridge is of interest for a variety of reasons. Some parameters that determine the current state of a bridge are the material properties and boundary conditions. Using strain measurements obtained from a slow-moving vehicle on a bridge, the boundary condition and material properties are determined through a mechanistic-based approach. Observing that the sign of the curvature would change at locations near the support when a load passes over a bridge with end rotational restraints, a methodology for determining the boundary conditions is proposed and validated. The linear elastic properties of the material that the bridge is made up of is determined from the strain measured at locations where the stress is independent of the material property. In this procedure, the structure is analyzed assuming some material properties and the stress at the measured point is determined. Then, the material parameters in the isotropic Hooke’s law are determined so that the stress estimated from the experimentally determined strains agrees with that obtained from the analysis with arbitrarily assumed material parameters. A prestressed high-performance concrete pi-shaped girder tested under a three-axle slow-moving load with strains measured at different locations is used to bring out the efficacy and appropriateness of the proposed methodologies. The mean value of Young’s modulus of the prestressed concrete bridge agrees well with the experimentally determined Young’s modulus.