Displacement Monitoring of I-35W Bridge with Current Vibration-Based System

Vertical displacements, while informative for monitoring the long-term serviceability and short-term behavior of bridge structures, are traditionally challenging to measure without on-site surveying. This project would develop an advanced sensor system to estimate the (1) long-term and (2) dynamic vertical displacements without a reference or on-site surveying. The long-term vertical displacements would reflect the serviceability of the bridge; while, the dynamic displacements would be used to augment the monitoring of the I35W bridge as a more robust indicator of stiffness, connection, and foundation degradation. Additionally, vertical deflection may offer a more direct comparison with design calculations and maintenance guidelines. Minnesota offers the unique opportunity of using the acceleration data from the I-35W Saint Anthony Falls Bridge alongside the global positioning (GPS) correction service offered by Minnesota Department of Transportation (MnDOT) to implement a vertical deflection monitoring system. Based on the long-term fidelity of the acceleration data, the accelerometer data (accounting for temperature and time-dependent effects) would be used in conjunction with a low-cost GPS sensor to estimate the vertical displacement of the bridge. Thus, no GPS base-station or fixed reference would be required. If the technique is successful and inexpensive, the monitoring approach could be widely implemented to help MnDOT prioritize maintenance needs among bridges and could limit routine surveying requirements.