Dynamic amplification of an orthotropic, multi span bridge deck under moving truck with tandem axles

Vehicles crossing bridges at high speeds can cause significant dynamic effects and must be studied by accurately simulating the interactive, dynamic responses of the bridge deck and the load-applying vehicles. Specifically, a multispan, orthotropic, bridge deck during truck loading is investigated to better understand the dynamic interaction between moving vehicles with tandem axles and highway bridge decks. The vehicle is modeled by a three-dimensional dynamic system with tandem axles with 9 degrees of freedom. The bridge deck is modeled by a thin, orthotropic, multi-span plate. The road surface irregularities are modeled by a random function characterized by a spectral roughness coefficient and power spectral density. The modal method is used to solve the equation of motion of the bridge deck. Equations of motion of the vehicle are obtained using a virtual work principle. The coupled equations of motion vehicle/bridge deck are integrated numerically by Newmark’s method. A computational algorithm in FORTRAN is used to solve the integrated equations of motion in a decoupled, iterative process. A numerical example of an orthotropic, three-span bridge deck, excited in nine degrees of freedom truck is presented. The resulting distribution of the Dynamic Amplification Factor on the bridge deck does not reflect any particular trend, because high values of the DAF can be obtained at points where the vertical displacement is small. The DAF is significant only under the interaction force. Thus, the road surface roughness had a significant influence on the dynamic vehicle/bridge deck interaction forces.