Vibration of Pedestrian Overpass

This is a report on the perceptible vibrations induced by normal pedestrian traffic on a pedestrian bridge in downtown Singapore, and the investigation of the relative efficiency of three proposed structural modification schemes for reducing vibration levels. The modifications involve, respectively, the addition of diagonal braces, an intermediate pier, and structural dampers to enhance the stiffness or the energy dissipation capacity of the bridge structural system. A comparative study was made of their relative efficiencies. Both the existing and modified bridge structures were subjected to a pulsating load representing a pedestrian walking across the bridge. On the basis of the maximum acceleration response at the midpoint of the bridge main span to this pulsating load, the relative efficiency of the structural modification schemes were determined. It was found that adding diagonal braces alone is least efficient in improving the dynamic behavior of the bridge structure, and that adding either structural dampers or an intermediate pier is most effective in reducing the bridge response to the pedestrian loads. The addition of structural dampers, was, however, found to the the most economical modification.