Modal analysis of natural dynamic frequency for a double deck cable-stayed steel bridge by using finite element method

Double-deck cable-stayed bridges are appropriate when there is a high traffic volume and little space for the structure. They combine road and rail transit to maximize the utilization of bridge structures and tackle traffic issues. This study investigates the fluctuations in the modal properties caused by several factors that impact the modal characteristics of bridges. The aim is to ascertain the system’s inherent frequencies, associated natural periods, and mode shapes. The modal analysis inquiry was conducted utilizing a software model grounded in the finite element method. The bridge deck slab, cable, pier, and pylon are discretized utilizing SHELL 181, CABLE 280, and BEAM 188 elements in this finite element model. The model’s dependability was validated by mesh convergence analysis and comparison with findings from prior research investigations. The cumulative mass participation factor analysis reveals that the bridge induces vibrations in 90% of the mass associated with the first five modes in the research of cumulative modal vibration. The application of prestressing force has significantly increased the natural frequencies of the bridges, resulting in a large rise. An increase in the damping ratio leads to a reduction in the natural frequency. Several factors, such as the existence or absence of prestressing force and different damping ratios in the bridge system, will affect free vibration results. Additionally, it can provide the foundation for subsequent fatigue analysis related to different dynamic loads.