Structural Identification of a Deteriorated Reinforced Concrete Bridge

AbstractDisplacement coefficients and profiles have been proposed as objective indexes for bridge structural condition evaluation by many researchers. In this paper, experimental data of the following type were collected for structural identification (St-Id) of a deteriorated bridge: (1) static displacement and strain measurements taken under proof-load level and (2) multireference impact testing (MRIT) data from one of the spans of a three-span, cast-in-place reinforced concrete T-beam bridge (Smithers Bridge). The MRIT was used to generate the modal data for computation of the modal flexibility and displacement profiles. Several significant obstacles were encountered during the St-Id of the Smithers Bridge including high damping level (which led to difficulties in identifying and selecting the poles), finite-element (FE) model updating challenges, and correlation of the MRIT results with truck load test measurements. The first challenge was addressed through the use of the complex mode indicator function method of modal identification, which is capable of identifying highly damped modes. Then the updating of the FE model was accomplished using the Strand7 FE analysis package coupled with the MATLAB application programming interface. Finally, to allow for direct comparison of the MRIT and truck load results, two strategies were employed. The first involved the redistribution of truck load force to the MRIT degrees of freedom and the second utilized interpolation functions for modal expansion of the MRIT results to include the truck tire locations. The St-Id procedure used during this application was designed to mitigate blatant human error and epistemic uncertainty in the data interpretation process. Successful results from the MRIT demonstrated the reliability of the applications for bridge condition assessment based on impact testing.