Dynamic Responses of a Cable-stayed Bridge under a High Speed Train with Random Track Irregularities and a Vertical Seismic Load

Abstract

The dynamic analysis of train-bridge systems has been a popular research topic for a long time; however, studies on cable stayed bridges subject to train and seismic loads remain limited. Cable-stayed bridges can experience large vibrations under external periodical loads due to the high flexibility caused by their long decks and cables. Previous approaches to modeling the cables have limitations in accuracy, principle, or calculation efficiency, making them unsuitable for dynamic analysis with numerous time steps for long-span bridges with many cables. Furthermore, track irregularities and earthquakes bring additional excitations to the train-bridge system and threaten its structural and running safety. Thus, an accurate and fast approach to modeling and analyzing cable-stayed bridges under train loads and other excitations is needed. In this study, an improved parabolic cable element is included for dynamic analysis. This cable element facilitates a faster calculation while maintaining an accuracy similar to that of a catenary cable element. The coupled equation-of-motion of the train and cable-stayed bridge system is derived and solved via the time integration method. The effects of railway track quality and seismic load are investigated through the dynamic responses of train-bridge systems by considering various classes of tracks and levels of seismic intensities, respectively. The impact factors of the vertical displacement of the deck and the tensions in cables are used to represent the behaviors of the bridge, while the maximum accelerations of vehicle bodies are used to represent the behaviors of the train. Track irregularities and seismic load significantly increase the responses of the bridge and train. With increased train speed, the negative effects of poor quality track on the responses of the train-bridge system increased; however, with increased seismic loads the effects were found to decrease.