Assessing the Influence of Modifications on In-service Performance of Structural Systems Using Vibration Measurements

This paper outlines application of dynamic testing to three separate structures where evaluations of their in-service condition and performance were required. In two of these cases, both bridges, model updating procedures enabled identification of key structural properties for performing an integrity assessment. In the case of the first bridge, dynamic testing was able to demonstrate that the first attempt at introducing bandbeams to strengthen the bridge over its piers was virtually ineffective in stiffening the bridge. However, after these bandbeams were replaced, similar dynamic testing verified that the new work was now in fact so effective in stiffening this same bridge. Dynamic testing of the second bridge, a historical wrought iron swing bridge, was able to verify the integrity of the central pile group about which this bridge swings to allow riverboats to pass through. For the third case, involving a specialist laboratory floor system, a variety of excitation options were exercised to establish the acceptability of the floor to stringent criteria on vibration response levels.