Bending Stiffness Identification of Simply Supported Girders using an Instrumented Vehicle: Full Scale Tests, Sensitivity Analysis, and Discussion

Abstract

Static load tests are currently essential to assess the actual response of prestressed concrete bridges: the bending stiffness is indirectly estimated from deflection measurements under loading. In this paper, to overcome the time-consuming and economic limits of static tests, an alternative testing procedure is developed based on the use of an instrumented vehicle. The vehicle hosts a swinging pendulum equipped with a laser sensor. Road irregularities and the beam detection due to the moving load excite the measurement device. The natural frequency of the pendulum is tuned to amplify low frequencies (f ≈ 2 Hz), i.e., the excitation due to the moving load, being practically insensitive to the high-frequency excitation due to the pavement roughness. The displacement response of the pendulum yields an estimate of the bending stiffness of each bridge span by optimizing the correlation function between the displacement time history recorded by the pendulum and the time history generated by numerical simulation. The optimization parameters are the bending stiffness itself and the initial conditions of the pendulum response. The feasibility of the procedure is tested on a set of real-case bridges. Preliminary outcomes give confidence for further development of the procedure and prelude an adequate validation of the method by comparing the results with static load tests. Covariance-based sensitivity analysis gives final matter for discussion, enlightening the effect of the uncertainties of the parameters on the results.