A velocity-related running safety assessment index in seismic design for railway bridge

With the rapid expansion of the high-speed railway (HSR) network, high-speed train running safety (TRS) over bridges is increasingly highlighted in the world. Previously, spectral intensity (SI) was proposed and considered as a performance-based index for discussing TRS over HSR bridges in seismic design. However, the speed independence of the conventional SI index greatly limits its rationality and generalisation in the performance-based bridge design under earthquake. To this end, the velocity-related SI index is proposed for the first time and improves the limitations of the conventional index in this research. The discrepancy between the proposed SI and the conventional SI is explained theoretically, and the correlation between the proposed SI and train running speed is illustrated in detail. Additionally, a series of scale model experiments are conducted to validate the feasibility of the train-bridge coupled (TBC) system. The probability analysis of the proposed SI index is presented to help discuss the randomness and economy of HSR bridges. Furthermore, systematic parametric analyses are finished by taking the train running speed as the kernel parameter based on the TBC model. The simulation results show the conventional SI index unduly neglected the velocity-induced vibration of the train under an earthquake. Within the common train running speed range, the proposed SI indices have the same varying pattern with the derailment factors and are comprehensively larger than the conventional SI indices. The vibration induced by train speed seriously threatens TRS under earthquake, but it was ignored in the seismic design for the HSR bridge before.