Thanawat Visessin, Koravith Tiprak, Eiichi Sasaki

Abstract: In traditional finite element analysis (FEA) of cable-stayed bridges, each stay cable is often represented by a single tension-only truss element with reduced stiffness to consider sag effects. Although this simplification is computationally efficient, the accuracy may not be sufficient to ensure reliable performance in cable Structural Health Monitoring (SHM). This study examines the influence of cable modeling strategies, particularly element discretization levels (1, 10, 50, and 100 elements per cable) and sag representation using Ernst’s effective modulus, on the dynamic characteristics of the Bhumibol Bridge in Thailand. Field-measured vibration data were employed to validate the numerical model in terms of modal frequencies and mode shapes. The results indicate that increasing the number of cable elements slightly raises the natural frequencies and enables more precise simulation of cable responses., while frequencies remain nearly constant beyond 50 elements. Incorporating Ernst’s effective modulus reduces the frequencies of both girder-dominated and cable-dominated modes, enhancing agreement between analytical and experimental results. Additionally, the inclusion of precamber slightly decreases the overall modal frequencies. These findings highlight the importance of proper cable discretization and sag representation to ensure accurate dynamic simulations, which are essential for SHM and digital-twin applications in long-span bridges.

Keywords: Cable-stayed bridge, finite element analysis, element discretization, precamber, Ernst effective modulus

Date Published: December 22, 2025
DOI: 10.11159/ijci.2025.022

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