Development of a hybrid bridge evaluation system

There is an increasing need to verify analytical dynamic models used for the seismic evaluation of existing bridges. During a retrofit evaluation, analytical models are created to predict the bridge response and damage levels due to seismic loading. These models should be verified so damage levels can be determined more confidently. Currently experimental studies are only occasionally performed on existing structures to verify analytical models because existing testing methods are too costly, require traffic shutdowns, and do not deliver results quickly enough for routine use. To overcome these limitations, the hybrid bridge evaluation system (HBES) was developed using ambient vibration techniques to inexpensively and quickly determine the dynamic characteristics of a large variety of structures. The HBES combines state of the art vibration measurement hardware with a series of custom developed programs to expedite ambient vibration studies. In particular, two new functions were developed and implemented as part of the HBES software to interpret the data quickly. These functions made it possible to analyse the data obtained from ambient vibration measurements in the field. This is a considerable advancement over traditional systems which require several weeks of data analysis after the field work is completed. Since partial experimental results can be obtained with the HBES while some of the tests are still in progress, the quality of the collected information can be assessed before leaving the site. After returning from the site, the experimental results can be used to verify and tune analytical models. A number of tests were conducted as part of this thesis which demonstrate the HBES’ performance. The study of the Shipshaw Bridge data, which was analyzed in one day, demonstrated the unique speed of the system. The study of the Squamish Wharf demonstrated the system’s capability to determine the dynamic characteristics of structures with very small ambient vibrations levels (+1- 0.02 mg). The complete study of the Colquitz River Bridge was used to evaluate the HBES’ components and their integration. This study confirmed the suitability of the hardware and demonstrated that the integrated programs were capable of expeditiously acquiring, analyzing, and interpreting large amounts of data. The experimentally obtained characteristics of the structure were used to refine the structure’s analytical models. The HBES system can now be used as an effective tool in the seismic evaluation of bridges.