Evaluation of signal processing techniques for the analysis of large civil structures.

Several new methods of determining change in the data signature of a large Cable-Stayed bridge are examined and compared. Two sets of data, one taken in September 1995, and the second in June 2000 are studied. Structural changes are investigated using several techniques; (1) Modal behavior in the .3 to 3 Hz range is investisated using Transmissibility FRFs and the Random Decrement Method, (2) Quasi Periodic behavior in the 3 to 30 Hz frequency range is observed in several tests. Potential causes and characteristics of this behavior are investigated. (3) Some methods of non-linear analysis are applied to the bridge data and changes in behavior are evaluated. Capability and concerns with each method are addressed in conjunction with physical ambient excitation data and its signal properties