Impact studies of multigirder concrete bridges

The impact behavior of multiple vehicles moving across rough bridge decks on seven multigirder concrete bridges with different span lengths is studied. The bridges are modeled as grillage beam systems. The vehicle is simulated as a nonlinear vehicle model with 12 degrees of freedom according to the HS20-44 truck design loading in American Association of State Highway and Transportation Officials (AASHTO) specifications. Four classes of road-surface roughness generated from the power-spectral-density function for the approach roadways and bridge decks are used in the analysis. The parametric analysis shows that the impact of exterior girders of short-span bridges is highly sensitive to such factors as lateral loading position, vehicle weight, road roughness, number of loading lanes, and lateral stiffness. The maximum impact factors of girders were obtained for three trucks (side by side) through changing their transverse positions, with different speeds and road-surface roughnesses. The results are useful for bridge design and further study of the impact formula proposed by the AASHTO specifications.