Field test investigations for condition monitoring of a concrete culvert bridge using vibration responses

Over the last two decades, vibration-based structural health and condition monitoring has gradually become one of the main methods for monitoring changes in a structure on a global scale. This method has been applied to damage detection in many areas, including aerospace, mechanical and structural systems. However, it has not been widely used for identifying condition change of the structure itself. This paper demonstrates the feasibility of utilising acceleration and strain responses measured from a short-span concrete culvert bridge located in New South Wales, Australia, to identify the effects of structural condition changes made to the deck due to bridge widening. In addition to the operating structural responses, two controlled traffic tests were carried out, before and after the bridge widening, in support of verifying the results from the modal analysis. A comparative study is presented evaluating the results obtained by two identification algorithms, namely, frequency-domain decomposition (FDD) and frequency–spatial domain decomposition (FSDD), from which the link between the decrease in modal frequency and the event of bridge expansion as condition change is successfully established. The contribution of this work is to emphasise the application of FDD and FSDD on a short-span concrete culvert bridge, in order to drive the interest from large-scale bridges to short-span bridges so as to increase the coverage of current bridge health monitoring.