Dynamic Field Testing for Condition Assessment of Bridge Bents

Seven forced vibration tests were performed on an isolated single span of a freeway overpass structure. The tests were performed in connection with a series of states of controlled damage and repair. The work focused on horizontal forced vibration utilizing an eccentric mass shaking machine. Data was collected with an array of accelerometers. Horizontal natural frequencies and mode shapes of the structure were determined for each test. Finite-element models were created to simulate the structure. Structural parameters in the model were optimized using an algorithm to match the natural frequencies and the mode shapes from the model with those from the experimental results. The analytical and experimental results were compared. It is shown that the structural parameters optimized from the algorithm can be used to identify the condition of the structure at each state. The technique presented in this paper successfully identified the estimated location and intensity of the damage or retrofit.