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 horiz ontal forced vibration utilizing an eccentric mass shaking machine. Data wa s collected with an array of accelerometers. Horizontal natural frequencies and mode shapes of the structure were determined for each test. Finite-ele ment models were created to simulate the structure. Structural parameters i n the model were optimized using an algorithm to match the natural frequenc ies and the mode shapes from the model with those from the experimental res ults. The analytical and experimental results were compared. It is shown th at the structural parameters optimized from the algorithm can be used to id entify the condition of the structure at each state. The technique presente d in this paper successfully identified the estimated location and intensit y of the damage or retrofit.