Purpose <p>An effective framework based on an instrumented three-mass test vehicle is proposed for identifying the damping ratio of a bridge by considering support effect.</p> Methods <p>In this vehicle-bridge interaction system, several sensors are installed on the test vehicle and the corresponding virtual scanning points on the bridge are used to identify the bridge damping ratio. The closed-form damping formula is derived by using the free-decay responses of any two scanning points for a simply supported bridge. Unlike the single-mode closed-form solutions, the scanning-point responses in the finite element analysis need to be filtered out, while this study further makes use of the dynamic responses provided by the two unsprung mass to enhance the accuracy.</p> Results <p>The support effect is systematically investigated and discussed via a simple beam and a two-span continuous bridge.</p> Conclusion <p>The liability of the proposed framework is proven through the parametric study with various practical factors in concern.</p>