Dynamic analysis of cable-stayed bridges using MIDAS Civil Software

Cable-stayed bridges are favored for long-span applications due to their structural efficiency and architectural appeal; however, their dynamic behavior under seismic activity, moving loads, and environmental excitation presents considerable design challenges. This study investigates the dynamic response of a typical cable-stayed bridge using MIDAS Civil, a specialized finite element analysis software for bridge engineering. The bridge was modeled with full 3D geometry, incorporating deck, pylons, and semi-fan stay cables. Modal analysis, time-history seismic loading, and vehicular moving load simulations were performed to evaluate displacement, stress variation, and vibration characteristics. Results revealed dominant low-frequency modes with coupled deck-cable-pylon behavior. The peak midspan displacement under seismic excitation reached 112 mm, with a damping ratio of approximately 5.7%, indicating stable energy dissipation. Moving load analysis showed stress variation in central cables up to ±12% of their prestressed force, highlighting the need for fatigue consideration. The simulation also confirmed that modal tuning, cable pretension optimization, and geometric nonlinearities significantly influence performance outcomes. This study demonstrates the effectiveness of MIDAS Civil in capturing complex dynamic interactions and supports its use for advanced performance-based design of cable-stayed bridges. The findings provide valuable benchmarks for engineers involved in the analysis, design and maintenance of long-span cable-supported structures.