Dynamic Parameters Identification of a Truss Pipeline Pedestrian Bridge

This paper is concerned with the study of the modal properties of a historical truss pipeline pedestrian bridge by means of operational modal analysis. Originally, it was a railway bridge that has been recently relocated about 100 km from its original location and converted into a pedestrian bridge. The deck is supported by two Pratt girders that have no connection at the top. On both sides of the bridge there are two walkways, originally intended for maintenance, but currently occupied by two water pipes. In this study, we apply operational modal analysis to the bridge under two different conditions, i.e., with empty and full pipes, and analyze the resulting changes in the modal properties of the bridge. Then, we study the effect of mass variation on the seismic response of the bridge. The results show that the first two natural frequencies of the bridge are greatly affected by the mass variation, while its seismic response remains unchanged.