Investigation on the Dynamic Response of a Damaged Bridge

Abstract

In this study, an experimental investigation was conducted on the changes to structural dynamic behaviour due to loss of section of a laboratory timber bridge. The fabricated timber bridge initially served as a benchmark to establish the dynamic characteristics of an undamaged bridge structure using Experimental Modal Analysis (EMA). Several damage scenarios were subsequently introduced on one of its girders to simulate damaged timber bridges. The modal tests/analysis were performed for each damage scenario, by which the extracted modal parameters were compared against that of the benchmark. The test results confirm that the detectable dynamic changes in terms of frequency response function (FRF), natural frequency and mode shape due to different damage scenarios are highly dependent on both ambient humidity and severity of damage. The investigation shows that although the damage can reflect detectable dynamic changes of the bridge, without decoupling the influence of humidity, employing damage identification methods may produce false identification results. This investigation provides further insight into current available damage identification algorithms with a view to establish new damage identification techniques for timber bridges.