Richard L. Wood
Date of this Version
Martindale, G. (2018). "Structural Identification and Assessment of the Inverted Tee Girder Bridge System." MS Thesis, University of Nebraska-Lincoln.
The Inverted Tee (IT) girder bridge system was originally developed in 1996 by the University of Nebraska–Lincoln (UNL) and Nebraska Department of Roads (NDOR) engineers. This bridge system currently accounts for over 110 bridges in Nebraska used for both state highways and local county roads. Excessive transverse and longitudinal deck cracking has been observed and noted in numerous bridge inspection reports. Since the IT girder bridge system is relatively new, limited data and knowledge exist on its structural performance and behavior. This study evaluates the IT girder bridge system by conducting twenty field observations as well as recording accelerometer time histories and lidar scans for a selected subset of these bridges. The field observations included visual inspection for damage and developing deck crack maps to identify a trend for the damage. System identification of the bridge deck and girders helped investigate the global and local structural responses, respectively. Operational modal analysis quantified the natural frequencies, damping ratios, and operational deflected shapes for the instrumented IT girder bridges. These results helped diagnose the reason for the longitudinal deck cracking. The IT girders respond nonuniformly for the first operational deflected shape and independently for higher modes. Two comparable bridges, namely one slab and one NU girder bridge, were instrumented to verify and demonstrate that the IT girder behavior is unique and undesirable. An advanced geospatial analysis was conducted for the IT girder bridges to develop lidar depth maps of the deck and girders elevations. These depth maps help identify locations of potential water/chloride penetration and girders set at various elevations and/or where the deck thickness is nonuniform.
Advisor: Richard L. Wood