Calculation of bridge deformations due to train passages by the use of strain and acceleration measurements from bridge monitoring supported by experimental tests

A monitoring campaign has been performed on a filler beam railway bridge for high-speed trains, measuring strains and accelerations due to train passages. For this purpose a very dense grid of measurement sensors was applied to the bottom side of the bridge deck, which allows the calculation of bridge deformations from strain measurements. Within this calculation the location of the cross section's neutral axis plays an important role, since it is required to derive curvatures from strains. The contribution shows how this location can be determined by means of modal analysis, using both acceleration and strain measurement data from decay curves after train passages. After a detailed description of the evaluation method experimental tests on a downscaled bridge deck are presented to prove the reliability of the proposed method. Similar to the situation on the real bridge deck, strain and acceleration sensors were distributed along the longitudinal axis of the test specimen. By measuring not only strains and accelerations but also deformations due to various kinds of excitation the evaluation method could be validated, since the calculated and measured location of the neutral axis and also the calculated and measured deformations were in good agreement. The evaluation method was successfully applied to measurement data from the presented monitoring campaign. The results are of great interest in view of assessing the bridge's dynamic behaviour. They also reveal valuable information about the cross-section properties of the monitored bridge deck which is finally discussed.