Vibration measurement and safety assessment of bridges

Abstract The objectives of the present studies are (a) to investigate the guidelines of instrumentation for application of a vibration test for detecting invisible damage in bridges and (b) to discuss the application of the results of vibration measurement in safety assessment. Finite element models have been set up to find out the change of natural frequencies and mode shapes of bridges with damaged structural members. It is found that the mode shapes can be used as the indicator for detecting damage or deterioration of the superstructure of a bridge and that natural frequencies can be used for detecting damages in the piled foundation of a bridge. The required values of accuracy of frequency control for an exciter used in the test are 0.05 Hz for the former and 0.1 Hz for the latter. In addition, the safety assessment of bridges, based on their response data during severe earthquakes, is also discussed.