Behavior Study of Two Decked Cables Stayed Concrete Bridge Under Modal Frequency Analysis

Abstract

Two decked cable stayed concrete bridges are engineered to support heavy traffic loads while optimizing space utilization in regions with limited land availability. These bridges are particularly suitable for spanning large distances while maintaining high functionality and aesthetic appeal. This research investigates the dynamic behavior of such bridges by utilizing finite element analysis (FEA), with a focus on modal frequencies, oscillation periods, and mode shapes that characterize the vibrational response pertaining to the structure. The Comprehensive Two decked cable stayed concrete bridge was devised by using staad pro to simulate the interactions between key structural components, including 12piers, 1440plates, 2 H type pylons, 160 cables. The modal mass participation analysis revealed the influence of elementary vibrational modes on the overall dynamic behavior of the structure, emphasizing the importance of mass distribution and dynamic loading effects in the performance of the bridge. Parametric studies were conducted to assess how changes in damping ratios affect the inherent frequencies of the structure. The time history distribution was performed to evaluate the bridge’s behavior under transient loading conditions. The analysis offered valuable insights into how damping helps control vibration amplitudes at Node 2 during the 1, 2, 3, 4, 5, 6 second time interval. Through interpretation of the graphs of acceleration, velocity, and displacement over time, it became apparent that damping plays a pivotal role in reducing vibrations—ultimately helping the bridge better withstand fatigue from repeated loading. This study yields noteworthy insights that help improve bridge design strategies, durability of double-deck cable- stayed concrete bridges, and support their long-term stability and resilience— especially when facing dynamic forces and the effects of maximum base shear in X, Y, Z directions."