Impact study for multi-girder bridge based on correlated road roughness

The impact behavior of a multigirder concrete bridge under single and multiple moving<br />vehicles is studied based on correlated road surface characteristics. The bridge structure is modeled as<br />grillage beam system. A 3D nonlinear vehicle model with eleven degrees of freedom is utilized according<br />to the HS20-44 truck design loading in the American Association of State Highway and Transportation<br />Officials (AASHTO) specifications. A triangle correlation model is introduced to generate four classes of<br />longitudinal road surface roughness as multi-correlated random processes along deck transverse direction.<br />On the basis of a correlation length of approximately half the bridge width, the upper limits of impact factors<br />obtained under confidence level of 95 percent and side-by-side three-truck loading provide probability-based<br />evidence for the evaluation of AASHTO specifications. The analytical results indicate that a better<br />transverse correlation among road surface roughness generally leads to slightly higher impact factors.<br />Suggestions are made for the routine maintenance of this type of highway bridges.