Examining changes in bridge frequency due to damage using the contact-point response of a passing vehicle

Ongoing inspection and maintenance of bridges poses a challenging task for infrastructure owners who must manage large bridge stocks with limited budgets. Drive-by monitoring approaches, using sensors in a vehicle, provide a promising solution to this challenge. This paper investigates the use of the response at the point-of-contact between the tyre and the bridge as a means of monitoring bridge frequency. An expression is derived to allow the contact-point (CP) response to be inferred directly from in-vehicle measurements, expanding on previous studies by allowing the vehicle suspension characteristics to be considered. The sensitivity of the CP-response to the pavement characteristics is investigated in detail and a rigid-disk model is used to overcome issues with how existing vehicle-bridge interaction models consider the interaction between the wheel and the pavement. The feasibility of the CP-response as a measure of bridge condition is investigated and results show that the CP-response significantly outperforms the response measured directly on the vehicle. The CP-response is successful in identifying the bridge frequency and changes caused by damage, without being influenced by the vehicle frequencies. Incorporating the CP-response into drive-by bridge monitoring will improve accuracy over existing methods which use the vehicle response alone.