Vibration Resonance and Cancellation of Simply Supported Bridges under Moving Train Loads

Based on the theoretical solution for vibrations of simply supported bridges under moving train loads, resonance and cancellation conditions are derived. The results reveal two types of vibration cancellations for simply supported bridges under moving train loads: the first is related to a single moving load, which is independent of the number and the composition of the train, while the second is related to the interval between a pair of moving loads. When cancellation occurs, the free vibrations induced by the moving loads cancel to null, and the bridge response is determined by the loads still on it. A resonance disappearance effect occurs when train speed meets both the resonance and cancellation conditions, while the cancellation plays a predominant role. Bridge damping has an influence on the cancellation effect: the higher the damping and the longer the interval between the loads, the lower is the cancellation efficiency. In a case study, dynamic responses of a bridge under high-speed train loads are analyzed and the mechanisms of resonance and cancellation are explained to support the theoretical solution.