Vibration-Based Monitoring and Damage Simulation of an Extradosed Cable-Stayed Bridge
Creators: Vendiola, Arnold
Publisher: name: University of Alberta Library
Year: 2023

<p>Most of Canada’s municipal infrastructure, including bridges, was built between the 1950s and 1970s. With design lives of 50-100 years, many of these structures are due for major rehabilitations or replacements. With the growing costs of deteriorating infrastructure, the cost savings from properly maintained structures are increasing in importance (Mirza, 2007). The use of Structural Health Monitoring (SHM), which uses sensor technology paired with data acquisition and analytical models to quantify various bridge parameters such as strain, vibration, and displacement, has been growing in popularity in recent years. The use of SHM systems can provide objective measurements which can supplement current inspection methods, such as visual inspections which can be prone to bias and inconsistency (Pines and Aktan, 2002). <br>
The Tawatinâ Bridge is an extradosed cable-stayed bridge in Edmonton, Alberta, Canada, that carries light-rail vehicle (LRV) and pedestrian traffic over the North Saskatchewan River. This thesis focuses on the development of a long-term vibration-based monitoring system for the Tawatinâ Bridge with the goal of providing a framework for establishing a baseline response for future structural health monitoring and predicting the effects of various damage cases on the modal properties of the bridge using an analytical model. Twelve triaxial accelerometers were deployed in four locations along the bridge, and the modal properties were calculated from the acceleration data using a Blackman windowing function, Fast-Fourier Transform (FFT), Covariance-driven Stochastic Subspace Integration (SSI-Cov), and Modal Assurance Criterion (MAC). A model was developed using CSiBridge to determine a theoretical baseline response and perform damage simulations. The model was analyzed using an eigenvector analysis and a linear modal time history using predicted train loads. The linear modal time history was paired with an SSI-Cov algorithm to determine the modal properties of the bridge.<br><br>
Data was collected from the field over ten site visits during the construction of the bridge’s shared-use-pathway (SUP). Data collected in the field during ambient testing appeared to have significant noise, and it appeared that more data collection is needed to effectively measure an accurate baseline response under ambient loads. Data collected from dynamic testing appeared to have issues with synchronization which made reporting accurate mode shapes infeasible. However, the forced excitation appeared to be effective in exciting some of the natural frequencies of the bridge as shown by agreement between the SSI-Cov and FFT results. Limitations of the sensor layout and data collection methods were discussed, and recommendations for future testing were provided and applied to the analytical model. <br>
An eigenvector analysis was performed with CSiBridge to determine the theoretical mode shapes of the bridge which may be measured during ambient conditions. A linear modal time history was also performed to investigate the theoretical behaviour of the bridge under predicted train loads. The mode shapes and natural frequencies of each damage case were compared to the baseline response to determine how effectively each damage type could be detected using the proposed damage detection scheme. In general, comparing mode shapes using MAC values appeared to be more effective at detecting damage than relying on natural frequency changes alone. Bearing damage and girder damage had the most notable impacts to the modal properties of the bridge which implies they could be easily detectable under the proposed damaged detection scheme. Stay cable damage and tower damage were found to have the least impact on the modal properties of the bridge which implies that other methods may be needed to detect damage to these components. </p>