Long-term measurements on a cable-stayed bridge

A long-term ambient vibration survey on the Fred Hartman Bridge in Texas is in progress primarily to monitor stay cable vibration. Part of this project includes efforts to better understand the overall wind performance and the modal characteristics of the structure. A PC-based data acquisition system was installed on the bridge to monitor deck and stay accelerations, wind speeds/directions and meteorological data during the three-year test program. One of the primary tasks in this process was the identification of structural frequencies and mode shapes under a wide range of meteorological and operating environments. The statistical distributions of the modal frequencies of the structure have been obtained from the locations of the peaks of the power spectra. In addition, the frequencies, as well as mode shape estimates, have been compared to a finite element (FE) model of the structure, showing reasonable agreement. This paper will summarize findings from the efforts described above, as well as describing relevant data from stay cable measurements.