Results from modal testing of the Daigneault Creek bridge

Despite several full-scale applications in Canada, the vibrational characteristics and performance of aluminium pedestrian bridges have not been studied comprehensively in the literature. Currently, a specific pedestrian supplemental code for aluminium bridges does not exist; thus only the general AASHTO LRFD bridge design specifications need to be met. Field vibration data from full-scale pedestrian bridges would likely shed new light on their vibrational behaviour and performance. This will allow aluminium bridge designers to create a competitive alternative to bridges constructed with conventional materials. A field study was conducted during the fall of 2012 to estimate the modal characteristics of an aluminium bridge in Brossard, Quebec. In this paper, the results of modal identification are presented, i.e., natural frequencies, damping, and mode shapes using a novel signal processing technique based on the vibration measurements. The estimated modal parameters are then compared with the results of a finite element model of the bridge. This field study provides new understanding of overall dynamics of aluminium pedestrian bridges, the contributions from higher modes, and the modal damping ratios.