Scanning the vertical and radial frequencies of curved bridges by a single-axle vehicle with two orthogonal degrees of freedom

This paper scans for the first time the vertical and radial (lateral) frequencies of a horizontal curved beam from the respective motions of a single-axle test vehicle by a theoretical approach. The vehicle is innovatively treated as a system with two orthogonal degrees of freedom (DOFs), each of a spring-dashpot unit, to capture both the vertical and lateral motions. To start, closed-form solutions are derived for the out-of-plane vibration (under the vertical and torsional contact forces) and in-plane vibration (under the centrifugal force) of the curved beam. Then the vertical and lateral motions of the vehicle are derived. Based on this, a generalized formula is derived for the corresponding contact responses. From the analyses using the generalized contact formula, it was demonstrated that: (1) the contact responses outperform the vehicle responses in that more higher bridge fre-quencies (out-of-plane and in-plane) can be identified; (2) the radius of curvature affects significantly the radial frequencies of the curved beam; (3) the eccentricity of the scanning vehicle has little effect on frequency identification; and (4) pavement roughness' effect can be remedied by random traffic, and it does not appear in the radial contact response.

Automated summary

This study scans the vertical and radial frequencies of a horizontal curved beam for the first time by analyzing the motions of a single-axle test vehicle. The vehicle is considered as a system with two orthogonal degrees of freedom, capturing both vertical and lateral motions. The results show that contact responses are superior in identifying higher bridge frequencies, the radius of curvature significantly affects the radial frequencies of the beam, the eccentricity of the vehicle has little effect on frequency identification, and pavement roughness can be overcome by random traffic without affecting the radial contact response.