Structural identification of steel stringer bridges for condition assessment

Recent bridge inventories indicate that over forty percent of the nearly half million bridges in the United State are deficient.;The University of Cincinnati Infrastructure Institute (UCII) has developed a bridge condition assessment methodology based on structural identification. This methodology has been designed to exploit and integrate recent advances in both experimental and analytical strategies, techniques, and tools, in order to overcome the obstacles which have so far hindered a reliable, conceptual, complete and accurate characterization of bridges.;This research was designed to simultaneously apply and improve the UCII bridge condition assessment method in the study of two steel stringer bridges.;The first bridge, a new bridge, was subjected to modal testing by impact as well as forced harmonic excitation. This testing capture twenty-one mode shapes and frequencies and the corresponding mass-normalized modal vectors; model flexibility was then obtained. Modal flexibility also served to test the completeness of the 3D Finite Element (FE) model calibrated as a byproduct of the structural identification process.;To complete the conceptualization of all the critical local response mechanisms, the bridge was comprehensively instrumented and tested by positioning four AASHTO Type 3-equivalent trucks in various configurations. The 3D FE model of the bridge was completed by incorporating the observed local deformation kinematics at the critical regions, and by calibrating the numerical model parameters to ensure the precise agreement of the measured and simulated modal and flexibility characteristics of the bridge.;The 3D FE model proved to be a reliable tool for the bridge since it simulated the measured behavior under the truck loading test. The critical rating factors obtained from analysis of the identified 3D FE model exceeded those obtained utilizing the AASHTO recommended load distributions by a factor of 2.8.;The same methodology was applied to the second bridge, a twenty-year-old bridge. Since the reliability of impact testing was confirmed on the first bridge, only this type of test was performed on the second bridge. The analytical model of the second bridge was then calibrated using the modal tests results. The final identified model was used to rate the bridge. (Abstract shortened by UMI.).