A theoretical study of force identification using prestressed concrete bridges

A moving force identification method taking into account the effects of prestressing is presented. A 2-axle medium lorry is modelled as a set of forces, with their magnitudes either constant or time-varying, moving across a bridge model having a span length of 28 m. Results show that identified forces are identical to input forces only when no noise is added to the simulated bridge responses. The identified forces from responses which include noise are poor, even with a noise level as low as 1%. However, the identification can be greatly improved using a low-pass filter. Results also show that the identified forces are over- and under-estimated, respectively, when the prestressing effects are neglected in the identification and calibration processes. Large percentage errors are also obtained when the prestressing effects are neglected in both processes. Additionally, the percentage errors decrease with decreasing prestressing forces, and do not change with the magnitude of axle forces and mass per unit length.