Highway Bridge Vibration Studies

The results of acceleration studies of highway girder bridges are presented. Deflection limitations and maximum span-depth ratios used in present bridge design codes do not necessarily ensure the comfort of bridge users. Vertical accelerations have been shown to be significant in producing adverse psychological effects on pedestrians and occupants of stopped vehicles. The effects on bridge accelerations of major bridge-vehicle parameters, including the properties of the bridge and the vehicle as well as the initial conditions of the roadway, were investigated analytically and compared to criteria for human response. Numerical solutions are obtained from a theory in which the bridge is idealized as a plate continuous over flexible beams for simple-span bridges and as a continuous beam with concentrated point masses for two- and three-span bridges. The vehicle is idealized as a sprung mass system. The results indicate that, for simple-span bridges, accelerations that might psychologically disturb a pedestrian are primarily influenced by bridge-span length, vehicle weight and speed and especially roadway roughness. Less significant factors are girder flexibility and transverse position of the vehicle. For the two- and three-span continuous bridges studies, roadway accelerations exceeded the recommended limit for comfort only when the effects of surface roughness were included. /Author/