Vehicle–bridge interaction analysis by the state-space method and symplectic orthogonality

The dynamic properties of bridges can be extracted from the dynamic responses of the vehicles passing on these bridges. This paper proposes a method for the vehicle–bridge interaction analysis of continuous beam bridges with different spans and variable cross sections using numerical methods that are high in computational efficiency. Herein, the vehicle is simplified as a spring–damper–mass system and coupled to the bridge by its interactional force in the governing equations based on the Timoshenko beam theory. According to the symplectic orthogonality of the state vectors, the orthogonality of the mode shapes of the Timoshenko beams is proved, and the dynamic responses of the continuous beam bridges with different spans and variable cross sections can be solved by the mode superposition method. More complicated factors, such as harmonic load on vehicles, noise in measurement, and roughness of pavements, can also be conveniently taken into account. Finally, the proposed method is demonstrated using some numerical examples and applied to a real bridge. The results indicate that the method is convenient, efficient, and precise for engineering applications.