Identification of bridge mode shapes using a passing vehicle

This paper describes the Short Time Frequency Domain Decomposition (STFDD) method for identification of bridge mode shapes using the responses measured in a passing vehicle. Several segments are defined on a bridge and a truck-trailers system is employed to measure the signals. Subtraction of the responses measured from following axles on the truck-trailers is used to remove the effect of road profile. The sensitivity of the STFDD method to sampling time interval and vehicle velocity is investigated using numerical studies. It is shown that selecting an optimum time interval may improve the accuracy of the results obtained. Furthermore, keeping vehicle speed below 4 m/s provides enough data for successful identification of bridge mode shapes.