Dynamic characteristics of a damaged pedestrian overpass measured by wireless sensor array

In this study, a fundamental attempt for structural health monitoring was performed on a damaged pedestrian overpass by using wireless sensor network system. The pedestrian overpass had local damage on its girder. The vibration measurement was repeated before and after the repair work of the girder with 14 Imote2 wireless sensors. Tri-axial acceleration were measured by free damped vibration after human excitation. Natural frequencies, damping ratio and mode shapes of plural vibration mode were identified from measurement result. Its natural frequencies of each mode did not change by the repair work. Mode amplitudes were slightly changed in several vibration modes. A detailed finite element model was constructed to reproduce the bridge analytically and vibration characteristics were compared to the measurement results. In the model, every members including non-structural members were modeled. The structural damage was measured for repair designing and these damage was reproduced in the numerical model. Eigenvalue analysis and time history dynamic response analysis were conducted. A detailed FE model could reproduce the actual bridge. The error of natural frequencies were 4% at maximum up to 6^th mode. However changes of natural frequencies and modal shape by repair work were not fully corresponded. In certain analytical case, dynamic response was changed at the damage location. However simulation results were not fully corresponded with the vibration experiment. The modeling error were need to be examined in the future study.