Bridge-Type Specific Management of Steel-Stringer Bridges Phase I, Validation of Tools;Final rept

摘要

The primary objective of this research has been to rigorously demonstrate that modal analysis and the measure of flexibility extracted from modal test data are effective tools for the condition assessment of structures. Modal test methods and modal flexibility were utilized on a decommissioned 3 span steel girder/concrete deck overpass in Cincinnati, Ohio. The bridge was subjected to various controlled damage and retrofit scenarios. Mutliple impact reference testing methods were employed to characterize the as-is condition as well as before and after each induced structural change. A portable, roving, instrumented impact hammer was used to apply impulse force to the test structure at multiple points. Vibratory responses were measured with accelerometers. Impact force and acceleration response signals were acquired and processed into frequency response functions with a dynamic signal analyzer. Modal characteristics were subsequently identified through diagnostic truckload testing. The results of the various tests were compared and correlated to evaluate (1) the consistency of modal test data, in particular, modal flexibility; (2) the effectiveness of modal flexibility for assessing existing bridge condition; and (3) the sensitivity of modal flexibility to changes in structural state/condition. Finally, test data was used to calibrate a 3D FE model of the structure and track the effects of various damage/retrofit scenarios on model parameters.