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The I-35W St. Anthony Falls bridge was highly instrumented with over 500 sensors to verify design assumptions; serve as a testbed to examine bridge sensing techniques; and evaluate the effectiveness of different bridge monitoring strategies. The instrumentation deployed on the bridge to investigate the structural behavior included vibrating wire strain gages (VWSGs); thermistors; fiber optic sensors (SOFO); resistance strain gages; linear potentiometers; accelerometers; and corrosion monitoring sensors. This report documented the successes and challenges of the monitoring program over the first ten years of the bridge's life. In particular; the effectiveness of different strain measurement techniques and sensor distributions were addressed. Previous investigations of temperature-dependent and time-dependent behavior were also expanded with the larger data set to better understand the behavior of post-tensioned concrete box girder structures with the potential to impact future designs.

Since the opening of the I-35W Saint Anthony Falls Bridge in 2008; over 500 sensors have been collecting data to better understand the behavior of post-tensioned concrete box girder structures. Recent research in the accelerometers installed on the bridge indicates they can be effectively used in a vibration-based structural health monitoring system; but previous studies have shown that natural frequency alone may not be sufficient to determine the performance of the structure. Vertical displacements were believed to be a simpler performance measure as direct comparisons can be made with design calculations and maintenance guidelines. To avoid the shortcomings of conventional displacement measurement options; this study focuses on using the currently installed accelerometers to estimate the vertical displacements of the southbound bridge. The proposed technique utilizes up-to-date modal parameters within a dual Kalman filter to estimate the vertical displacements of the structure from noisy acceleration measurements. When applied to the I-35W Saint Anthony Falls Bridge; it was found that the dual Kalman filter approach captures only dynamic displacements due to relatively slow loading (e.g.; traffic loading and thermal loading) and the corresponding low-frequency static displacements are likely too small for GPS measurements due to the high stiffness of the structure.