Multiple Reference Impact Testing for Bridge Assessment with Drop Hammer

A new drop hammer was designed and used for multiple reference impact testing of two bridges. The drop hammer utilizes a multiple-rebound control system for successfully applying a single impact with repeatable high-level force for bridge testing. Signal analysis results indicate that the drop hammer provides a higher signal-noise ratio and a better coherence even when the response signals are subject to pollution due to traffic on the bridge. Modal flexibility was computed by using the impact data from the drop hammer, and meaningful deflected shapes could be generated demonstrating the potential of the envisioned structural assessment system.