Influence of truck suspensions on the dynamic response of a short span bridge over Cameron's Creek

The dynamic interaction between bridges and vehicles increases when the natural frequencies of the dynamic wheel forces associated with body bounce (2 to 4 Hz) match those of the bridge. This interaction with body bounce vibrations does not occur in short span bridges as their natural frequencies are greater than 8 Hz. However, research conducted as part of the Organisation for Economic Co–operation and Development DIVINE international research project has demonstrated that dynamic coupling occurs in short span bridges with natural frequencies corresponding to those of axle hop (10 to 15 Hz). The dynamic response of a 9.14 m (30 ft) span prestressed concrete bridge and the dynamic wheel forces were measured simultaneously for both a conventional steel leaf spring and air suspensions fitted to a tri–axle trailer. The dynamic response of the bridge was large but sensitive to speed, road roughness and suspension. Generally the peak bridge deflections were smaller when the air suspensions were fitted except when axle hop was induced by roughness. In this case, at critical speeds, the vehicle fitted with the air suspension and the bridge coupled to give large deflections and multiple fatigue cycles during the passage of the test vehicle.